ICS 25.160.10
J 33
DL
:61655-2018
Electrical power industry standard of the people’s republic of china
DL/T 1762-2017
___________________________________________________________________________
Technical guide of welding-for transmission line steel tube tower
Published on 2017-11-15
implementation
2018-03-01
___________________________________________________________________________
National Energy Board
DL/T 1762-2017
Contents
1 Scope ............................................................................................................................................................... 1
2 Normative reference documents ................................................................................................................... 1
3. Basic regulations ........................................................................................................................................... 2
3.1 General requirements ............................................................................................................................. 2
3.2 Steel .......................................................................................................................................................... 2
3.3 Welding materials ................................................................................................................................... 3
3.5 Welding equipment ................................................................................................................................. 5
3.6 Weld grade............................................................................................................................................... 5
3.7 Welding process operation documents................................................................................................ 10
4 Design requirements .................................................................................................................................... 11
4.1 Welding design principles .................................................................................................................... 11
4.2 Welds connecting steel pipes and flanges............................................................................................ 13
4.3 Construction and quality requirements of gusset plates and steel pipe welds ................................ 14
4.4 Dimensions of T-shaped welding joint of gusset plate ....................................................................... 14
4.5 Longitudinal weld arrangement of main pipe ........................................................................................ 15
4.6 Requirements for weld layout and corner cutting of stiffeners and accessories ............................. 15
4.7 Tailor welding of circumferential ribs ................................................................................................ 15
4.8 Structural requirements for the slope change of the main material of the tower body and the
hanging points ............................................................................................................................................. 16
4.9 Welding groove form and size ............................................................................................................. 16
4.10 Pipe truss structural welds ................................................................................................................. 16
5 Grooving processing and weldment assembly ........................................................................................... 18
5.1 Bevel processing .................................................................................................................................... 18
5.2 Weldment assembly .............................................................................................................................. 18
6 welding .......................................................................................................................................................... 20
6.1 Environmental requirements ............................................................................................................... 20
6.2 Preheating and inter pass temperature............................................................................................... 20
6.3 Welding process .................................................................................................................................... 21
6.4 Correction of weldments ...................................................................................................................... 24
6.5 Afterheat ................................................................................................................................................ 24
6.6 Post-weld heat treatment ...................................................................................................................... 24
7 quality inspection ..................................................................................................................................... 24
8 quality standards.......................................................................................................................................... 26
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DL/T 1762-2017
8.1 Weld appearance inspection quality standards.................................................................................. 26
8.2 Non-destructive testing quality standards for welded joints ............................................................ 30
9. Treatment of unqualified welded joints .................................................................................................... 31
10 Welding technical documents ................................................................................................................... 31
II
DL/T 1762-2017
List of figures and tables
Figure 1 Rigid connection between steel pipe and flange .................................................................................. 6
Figure 2 Flexible connection between steel pipe and flange Weld connection form of steel pipe tower
component .......................................................................................................................................................... 6
Figure 3 Butt welding of steel pipe and neck flange Forged flat neck ................................................................ 7
Figure 4 Steel pipe and neck flat welding flange ................................................................................................ 7
Figure 5 Steel pipes intersect with steel pipes ................................................................................................... 7
Figure 6 Welding of connecting plates, annular reinforcing plates, rip plates and steel pipes.......................... 7
Figure 7 c-shaped 0-shaped insert plate and Welding of glyph inserts, intermediate inserts and steel pipes .. 8
Figure 8 Welding of U-shaped groove and U-shaped plate ................................................................................ 8
Figure 9 Butt welding of tensile steel pipe tower hanging wire plate ................................................................ 8
Figure 10 Circumferential butt welding of main material pipes with variable slope ......................................... 9
Figure 11 Flange butt welding of main material pipes with variable slope ........................................................ 9
Figure 12 Flat flange bolt connection of main material with variable slope ...................................................... 9
Figure 13 Angle steel opening and bending welding seam diagram ................................................................ 10
Figure 14 Steel plate split butt .......................................................................................................................... 10
Figure 15 Convex fillet weld .............................................................................................................................. 12
Figure 16 Fillet welds with unequal welding legs on both sides....................................................................... 12
Figure 17 Relief (convexity) weld ...................................................................................................................... 13
Figure 18 Combined weld (butt + fillet weld) ................................................................................................... 13
Table 1 Classification and grouping of commonly used steel materials for domestic steel tube towers .......... 2
Table 2 Recommended welding materials for commonly used steel types ....................................................... 3
Table 3 Values of leg dimensions for T-shaped welding joints of gusset plates............................................... 14
Table 4 Weld groove forms and dimensions of T, K, and Y-shaped joints of pipe truss structures ................. 16
Table 5 for common steel welding preheating temperatures. For steel materials .......................................... 20
Table 6 Length and number of tack welds for steel pipe and flange combinations ......................................... 22
Table 7 Weld appearance inspection and acceptance criteria ......................................................................... 26
Table 8 Allowable deviation of weld size (mm) ................................................................................................ 27
Table 9 Allowable enlarged dimensions of welds ............................................................................................. 28
Table 10 Fillet weld leg dimensions for T, K, and Y-shaped joints of pipe truss structures.............................. 28
Table 11 Allowable deviation of weld edge straightness ................................................................................. 30
Table 12 Inspection methods and grade requirements for internal quality of welds ...................................... 30
III
DL/T 1762-2017
Preface
This standard is drafted in accordance with the rules given in GB/T1.1-2009 "Standardization Work
Guidelines Part 1: Structure and Preparation of Standards".
Please note that some content in this document may be subject to patents. The publisher of this
document assumes no responsibility for identifying these patents.
This standard is proposed by China Electricity Council.
This standard is under the jurisdiction of the Electric Power Industry Power Station Welding
Standardization Technical Committee (DL/TC18).
The units responsible for drafting this standard: China Electric Power Research Institute Co., Ltd.,
Qingdao Wuxiao Group, Hebei Ningqiang Light Source Co., Ltd., Jiangsu Huadian Tower
Manufacturing Co., Ltd., Weifang Wuzhou Dingyi Tower Co., Ltd., Jiangsu Electric Power Company
Electric Power Research Institute, State Grid Corporation of China Communication Construction
Branch.
The main drafters of this standard: Qiao Yaxia, Nie Renyuan, Min Mingzhao, Liu Ya, Wu Jianqiang,
Ren Jihua, Liu Jianjun, Zhao Sen, Wu Yingli, Liu Weining, Leng Yuechun.
This standard is published for the first time.
Feedback your opinions or suggestions during the implementation of this standard to the
Standardization Management centre of China Electricity Council (No. 2 Tiao 1, Baiguang Road,
Beijing, 100761).
IV
DL/T 1762-2017
1 Scope
This standard specifies the welding technical requirements during the design, manufacture and
maintenance of steel tube towers.
This standard applies to welding methods using electrode arc welding (SMAW), non-melting arc gas
shielded welding (GTAW), melting electrode (solid and flux-cored wire) gas shielded welding
(GMAW, FCAW), submerged arc welding (SAW), etc. welding work.
This standard also applies to the welding of steel pipe poles, substation steel pipe structural supports,
and angle steel towers.
2 Normative reference documents
The following documents are essential for the application of this document. For dated references, only
the dated version applies to this document. For undated referenced documents, the latest version
(including all amendments) applies to this document. GB/T 700 carbon structural steel
GB/T 706hot rolled steel
GB/T 709 Dimensions, shapes, weights and tolerances of hot-rolled steel plates and strips
GB/T 985.1 Recommended slopes for gas welding, electrode arc welding, gas shielded welding and
high energy beam welding!
GB/T 985.2 Recommended grooves for submerged arc welding
GB/T 1591Low alloy high strength structural steel
GB/T3274 Carbon structural steel and low alloy structural steel hot-rolled thick steel plates and strips
GB/T 3323 Radiography of metal fusion welded joints
GB/T 4842 gas
GB/T 5117Non-alloy steel and fine grain steel welding rods
GB/T 5293Carbon steel wire and flux for submerged arc welding
GB/T 5313Thickness direction performance steel plate
GB/T8110 (carbon steel and low alloy steel welding wire for body shielded arc welding
GB/T8162Seamless steel pipe for structural use
GB/T 10045carbon steel flux cored wire/T 11345 Non-destructive testing of welds Ultrasonic testing
technology, testing levels and assessment
GB/T 12470Low alloy steel wire and flux for submerged arc welding
GB/T 17493Low alloy steel flux cored wire
GB/T29712 Non-destructive testing of welds Ultrasonic testing acceptance level
DL/T 542 Ultrasonic testing method and quality assessment of steel fusion welded T-joints
DL/T 678 General technical conditions for welding of power steel structures
DL/T 752 Technical Specifications for Welding of Dissimilar Steels in Thermal Power Plants
DL/T 819 Technical Specifications for Welding Heat Treatment in Thermal Power Plants
DL/T 820 Technical Specification for Ultrasonic Inspection of Pipe Welded Joints
DL/T 868Welding procedure qualification procedures
DL/T 1611 Ultrasonic inspection and quality assessment of butt welds of steel pipes on transmission
line towers
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DL/T 1762-2017
HG/T 2537carbon dioxide for welding
JB/T 3223 Quality Management Regulations for Welding Materials
JG/T 203 Ultrasonic flaw detection and quality classification method for steel structures
NB/T 47013.4 Non-destructive testing of pressure equipment Part 4: Magnetic particle testing
NB/T 47013.5 Non-destructive testing of pressure equipment Part 5: Penetrant testing
3. Basic regulations
3.1 General requirements
3.1.1 Before welding the steel pipe tower, the welding process qualification should be carried out in
accordance with the provisions of DL/T 868 or the technical requirements of product design.
3.1.2 Prepare welding process operation documents based on welding process assessment and on-site
processing conditions.
3.1.3 The welding method should be based on the technical and economic requirements of the
structure, weld type, welding equipment, welder operating skills, and processing conditions. Relatively
certain.
3.1.4 The requirements for welding technicians, welding quality inspectors, welding inspection and
testing personnel, welders, and welding heat treaters should comply with the provisions of DL/T 678.
3.1.5 Welding work should comply with occupational health and safety, environmental regulations
and other relevant technical requirements’/T 3728 Mixed gas oxygen and carbon dioxide for
welding16:26
3.2 Steel
3.2.1 The quality of steel materials should comply with the requirements of the design documents, and
should be accompanied by material quality certification documents. Before using steel for the first
time, weldability data and instructive process data on welding, welding heat treatment and other
thermal processing methods should be collected. Commonly used steel materials for domestic steel
tube towers are classified into groups and should comply with the regulations of DL/T 868.
Table 1 Classification and grouping of commonly used steel materials for domestic steel tube towers
Steel type
Category
number
Carbon structure
steel
I
Low alloy
high
strength
steel
II
Group
number
Steel grade example
Corresponding
standard
I-1
Q235、Q255、Q275
GB/T 700
II-1
Q345
II-2
Q390
II-3
Q420
II-4
Q460
2
GB/1591
DL/T 1762-2017
Note: the steel category from low to high are I, IL, and the steel group from low to high are 1、2、3 “
．
3.2.2 The quality of steel plates, angle steel (including large-size angle steel), seamless steel pipes and
flanges used in steel tube towers should comply with GB/T 700, GB/T 709, GB/T 1591, GB/T 706,
GB/T 3274, GB/T8162 and other standards, the supply status should be hot rolled. The steel plate used
to manufacture flat flanges shall not have delamination defects; when using Z-direction performance
steel, the quality shall meet the requirements of GB/T5313.
3.2.3 Steel materials should be re-inspected before they can be put into use, and the use of engineering
materials should be approved by the designer.
3.2.4 During use, if there is any doubt about the steel material, the chemical composition and
mechanical properties should be re-inspected and confirmed according to the steel furnace batch
number.
3.2.5 The quality requirements of steel for straight seam welded pipes should comply with the relevant
procurement technical conditions. The steel used for manufacturing straight seam welded pipes should
have no delamination defects within 25mm of the edge of the straight welded plate.
3.2.6 Forged flanges should be supplied in a normalized or normalized and tempered state. They should
have a quality certificate when purchasing and undergo sampling re-inspection. The re-inspection
items include appearance quality and size, material chemical composition, mechanical properties,
metallographic structure and internal defect inspection. The quality requirements should comply with
the provisions of the contract procurement technical conditions. In addition to the above requirements,
if the technical specifications of the procurement contract have other quality requirements for forged
flanges, they shall be implemented in accordance with the specified requirements.
3.3 Welding materials
3.3.1 Welding materials should be selected according to the chemical composition, mechanical
properties and operating conditions of the steel. Recommended welding materials for commonly used
steel types are shown in Table 2.
Table 2 Recommended welding materials for commonly used steel types
Arcwelding
electrode model
Steel grade example
Submerged
C02 Gas shielded
arc welding welding
wire and flux
Solid F flux cored
wire wire
model
Low carbon
steel
Low alloy
high strength
steel
Q235、
Q255、
Q275
Q345
E4303
E4316
E4315
E5016
E5015
E5015·G
model
GTAW
Welding
wire
grade
F4A2-H08A
F4A4-H08MnA
F5A2-H08MnA
F5A2-H 10Mn2
3
ER50．2
E43 IT-G
ER50．6
E500T15
ER50-G
E501T· IL
E501T· 1
DL/T 1762-2017
Q390、420
E5016
E5015
F5A2-H 10M
F5A4-H 10Mn2
E5015．G F5A2-H IOMnSi
CHW-S9
E5516-G
Welding
wire:
E5515G
H08MnMoA
E5510-G
ER55-G
ER50-G
E551T-Nil
ER55-G
ER60-G
E551T1．Nil
E601T1 ·Kl
E601T1 ·Ni2
ER60-G
F55XXQ 360
E6015．G
E6016-G
HO8MnMoA
F55XXH08Mn2MoVA
3.3.2 The selection of welding materials of the same type of steel shall meet the following
requirements:
a) The chemical composition and mechanical properties of the deposited metal of welding materials
are equivalent to those of the base material.
b) The welding process performance is good.
3.3.3 When welding dissimilar steels, the selection of welding materials should comply with the
requirements of DL/T 752. 3.3.4 Welding rods for carbon steel and low alloy structural steel should
comply with the regulations of GB/T5117.
3.3.5 The types of submerged arc welding wire and flux and the mechanical properties of the deposited
metal should comply with the regulations of GB/T5293 and GB/T 12470.
3.3.6 Carbon steel and low alloy steel welding wires used for gas shielded welding should comply with
the regulations of GB/T8110, and flux-cored welding wires should comply with the regulations of
GB/T10045 and GB/T 17493 respectively.
3.3.7 New welding materials used for the first time should have technical data such as chemical
composition, mechanical properties, and instructive welding process parameters of the deposited
metal, and can only be used after passing the welding process assessment.
3.3.8 Imported welding materials used in welding projects should be re-inspected to confirm that they
meet the design requirements before use, and the welding process should be evaluated.
3.3.9 The acceptance, storage and use process of welding materials should comply with the provisions
of JB/T3223.
3.3.10 The drying of welding rods should meet the following requirements:
a) Moisture-proof measures should be taken when storing acidic welding rods. The damp welding rods
should be baked in the range of 100℃~150℃ for 1h~2h before use.
b) Low hydrogen type welding rods shall meet the following requirements:
-The welding rod should be baked at 350℃~400℃ for 1h~2h before use, or baked according to the
welding rod instruction manual provided by the manufacturer.
Dry. The temperature of the oven when the welding rod is placed should not exceed half of the
specified maximum baking temperature, and the baking time shall not exceed the specified maximum
baking temperature when the oven reaches the specified maximum.
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DL/T 1762-2017
Calculation starts after high baking temperature.
- The dried low-hydrogen welding rod should be placed in an insulating box with a temperature of not
less than 100°C for storage until use; it should be placed in an insulating barrel when used and taken
out as needed.
After drying, the welding rod should not be left in the atmosphere for more than 4 hours, and the
number of times it should be re-dried should not exceed 2 times.
3.3.11 Flux should meet the following requirements:
a) Before use, it should be baked at the temperature recommended by the flux manufacturer. Flux that
has become damp or agglomerated should not be used:
6) Flux used for welding Class II steel should not be left in the atmosphere for more than 4 hours after
drying.
3.3.12 The welding wire should be de-rusted, de-scaled and de-greased before use.
3.4 Welding gases
3.4.1 Ammonia gas should comply with the regulations of GB/T4842, and the purity of hydrogen used should
reach 99.9% and above.
3.4.2 Carbon dioxide gas should comply with the regulations of HG/T 2537, and mixed gas should
comply with the regulations of HG/T 3728.
3.4.3 Other gases used in welding projects should comply with relevant standards.
3.5 Welding equipment
3.5.1 All welding equipment (including heat treatment equipment, non-destructive testing equipment)
and instruments used should be inspected regularly and kept in good condition. Measurement
calibration is required.
The part should be used within the verification validity period.
3.5.2 Before use, the welding process equipment and welding auxiliary equipment involved in welding
and welding repair should be confirmed to be suitable for the welding work undertaken.
3.5.3 The welding current, welding time, and mechanical pressure of automatic welding equipment
should match the parameters required to produce welding workpieces, meet the requirements of
welding process parameters, and have point-to-point repeatable positioning accuracy, trajectory
repeatability accuracy of the equipment, and the accuracy of the machine equipment. The control and
drive systems have corresponding anti-interference capabilities. Automatic welding equipment should
have welding teaching functions, welding process fault display and self-processing functions, and arc
starting and arc closing functions
3.6 Weld grade
3.6.1 The grades of steel tube tower welds are classified as follows:
a) First-level welds: circumferential butt welds between steel pipes and forged neck flanges, butt welds
connecting hanging wire plates, and steel pipe butt welds at slope changes.
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DL/T 1762-2017
b) Secondary welds: butt welds and gap butt welds of steel pipes with stiffened plates at slope changes.
c) Secondary appearance weld: circumferential fillet weld between steel pipe and flat flange. The main
stress-bearing welds connecting the gusset plate and the steel pipe, the outer welds between the steel
pipe and the connecting plate, the insert plate, that is, C-shaped, cross-shaped, and flat-shaped, and the
intersecting connection welds between pipes, etc.
d) Level 3 welds: gusset plates or rib plate welds on steel pipes, longitudinal welds of welded pipes
and other welds.
Note: The slope change point refers to the part where the slope of the tower body and the tower head
structural surface changes, causing curved connecting tower materials to appear at the nodes.
3.6.2 The weld connection form of steel pipe tower components is shown in Figure 1 (the middle weld
level is shown in the figure). The weld level should be determined according to the requirements of
the drawings and design documents. If there are no clear requirements in the drawings and design
documents, the weld level should be determined in accordance with 3.6.1 based on the stress state,
weld form, working environment and importance of the tower component welds.
Upper ring weld
appearance level two
lower ring weld
Figure 1 Rigid connection between steel pipe and flange
Upper ring weld
lower ring weld
stiffened plate angle (combined)weld
Figure 2 Flexible connection between steel pipe and flange Weld connection form of steel pipe tower
component
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DL/T 1762-2017
First -level grith weld
between steel pipe and
forged neck flange
steel pipe
Forged neck flange
Figure 3 Butt welding of steel pipe and neck flange Forged flat neck
steel pipe
steel pipe and forged neck
flanges fillet ring welds
Forged neck flat
welding flange
Figure 4 Steel pipe and neck flat welding flange
stiffened plate welds(third level
welds)stiffened plates
Branch steel pipe
Main steel pipe
intersecting welds
(secondary appearance)
Figure 5 Steel pipes intersect with steel pipes
Main stress weld secondary
Main stress welding seam
secondary appearance
secondary appearance
Ring plate butt weld
secondary welds
secondary appearance
fillet welds,tertiary welds
Figure 6 Welding of connecting plates, annular reinforcing plates, rip plates and steel pipes
7
DL/T 1762-2017
cross plate steel pipe C(1) shaped
plug -in board
Main stress bearing welds
meet the secondary appearance quality
Main stress bearing welds
meet the secondary appearance quality
secondary appearance
secondary welds
fillet welds,tertiary welds
Figure 7 c-shaped 0-shaped insert plate and Welding of glyph inserts, intermediate inserts and steel pipes
U-shaped plug- in board
The main stress bearing welds
steel pipe
meet the secondary appearance quality
Figure 8 Welding of U-shaped groove and U-shaped plate
main stress weld (secondary appearance)
First level penetration weld
First level penetration weld
Hanging board
Figure 9 Butt welding of tensile steel pipe tower hanging wire plate
8
DL/T 1762-2017
steel pipe longitudinal weld seam
steel pipe circumferential butt weld
First class weld
Figure 10 Circumferential butt welding of main material pipes with variable slope
steel pipe butt weld
secondary welds
main steel pipe slope change method
stiffened plate angle (combined )weld
level three 3 weld
Figure 11 Flange butt welding of main material pipes with variable slope
variable slope main material steel pipe
Bolted flat flange
rib board
External (inner ) grith weld between flange and pipe
corner fillet weld, secondary appearance
stiffened plate angle (combined )weld
level three 3 weld
Figure 12 Flat flange bolt connection of main material with variable slope
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DL/T 1762-2017
Gap filler welding plate
cut butt weld
secondary welds
Figure 13 Angle steel opening and bending welding seam diagram
bending line
cut welds
secondary welds
Figure 14 Steel plate split butt
3.7 Welding process operation documents
3.7.1 Welding process operation documents should be prepared separately for different components
and confirmed during first article inspection.
3.7.2 Welding process operation documents should include the following contents:
a) Purpose and coverage of preparation.
b) Basis of preparation, product/component name.
c) Conditions before starting work (including people, tooling and molds, environmental factors,
preparation before welding, process measures, etc.).
d) Bevel form, size and processing method.
e) Description of welding methods, welding equipment and welding materials.
f) Set assembly and tack welding requirements.
g) Preheating methods and processes.
h) Welding specifications.
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DL/T 1762-2017
i) The requirements for the number of layers of multi-layer welding, the number of passes for multipass welding, and the control requirements for operating time.
j) Requirements and instructions for root cleaning on the back side of the weld.
k) Welding sequence and measures to control welding deformation.
1) Methods and specifications for post-heating and post-weld heat treatment.
m) Quality inspection items and acceptance criteria as well as repair instructions.
3.7.3 The important contents of the welding process operation documents should form a welding
process card.
4 Design requirements
4.1 Welding design principles
4.1.1 The weld layout should follow the following principles:
a) The welding seam location should avoid the maximum stress and stress concentration parts of the
structure.
b) They should be dispersed as much as possible to avoid centralized gathering and intersection, reduce
"cross" cross welds in plane or space, and reduce weld overlap.
c) The location of welds should consider accessibility for welding and inspection.
d) The weld settings should be arranged as symmetrically as possible.
e) There should be no sharp corners at the end of the weld, and the joint should have a smooth
transition.
4.1.2 The form of weld joints should follow the following principles: comprehensive consideration
should be given to welding method, structural shape and size, strength requirements, amount of filler
metal and groove form, ease of processing and other factors.
4.1.3 The design of weld grooves should follow the following principles:
a) The groove design should be able to ensure the welding quality, enable the arc to reach the root
penetration, and ensure that the root penetration of the weld does not cause defects such as incomplete
penetration and incomplete fusion.
b) On the premise of meeting the strength requirements, select reasonable welding joints and grooves
to reduce the filling amount of welding materials, improve welding efficiency, and reduce welding
stress and welding deformation.
c) The weld groove should be comprehensively considered together with the welding method,
workpiece thickness, and weld quality grade requirements.
d) Priority should be given to bevelling that is easy to process.
4.1.4 The weld size design should follow the following principles:
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DL/T 1762-2017
a) The weld strength of the working force transmission welds should be calculated; the secondary
contact welds should meet the weld structure requirements, and economy should be considered, and
the size of the welds should not be increased arbitrarily: For those who bear both the work force
transmission and connection for welds that are acting, the strength of the working force transmission
should be calculated.
b) The welding position of the intersection node of the component, the effective weld length, the
effective cross-sectional size of the weld, and the weld penetration depth of the combined weld should
comply with
c) Design strength, weld construction requirements, and calculated thickness h of the weld. As shown
in Figure 2. The weld size should be indicated in the design drawings.
For example, fillet welds are marked with weld thickness h. Or weld leg size hro c) When a partially
penetrated butt weld is used, the form and size of the groove and its calculated thickness h should be
noted in the design drawing. It should not be less than 1.5√, 1 (mm) is the maximum thickness of the
weldment.
d) The maximum leg size hr of the fillet weld should not be greater than 1.2 times that of the welded
thinner plate (except for steel pipe structures). The size of the weld legs on both sides of the fillet weld
is generally the same. When the thickness of the welding parts differs greatly and equal welding leg
sizes cannot meet the requirements, unequal welding leg sizes can be used. The size of the welding leg
in contact with the thinner plate weldment should not be greater than 1.2 times the thickness of the
thinner plate; the size of the welding leg in contact with the thicker plate should not be less than 1.5√t
of the thicker plate.
Reheight (convexity)
weld
weld leg size hf
weld seam
weld thickness
welding leg size hf
calculated thickness of weld he
Figure 15 Convex fillet weld
Reheight (convexity)
horizontal direction
weld leg size hf2
weld seam
welding leg size hf
size hf
calculated thickness of weld he
Figure 16 Fillet welds with unequal welding legs on both sides
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DL/T 1762-2017
welding feet
weld thickness
weld
convexity
welding leg size hf
calculated thickness of weld he
Figure 17 Relief (convexity) weld
Reheight (convexity)
weld
welding leg size hf
weld
welding leg size hf
calculated thickness of weld he
weld thickness
Figure 18 Combined weld (butt + fillet weld)
4.2 Welds connecting steel pipes and flanges
When the steel pipe is connected to the flange, if it is not specified on the drawing, the size of the
welding leg should meet the following requirements:
a) When the steel pipe is inserted into the rigid plane flange [see Figure 1)], the depth of the steel pipe
inserted into the flange should not be less than 1/2 of the flange thickness, double the surface adopts
the welding form of internal and external fillet welds, and the size of the welding leg is determined by
the thickness of the pipe wall. The welded intersections between stiffeners, flanges, and steel pipe
walls should be chamfered to avoid overlapping welds.
b) When welding steel pipes to flexible flanges [see Figure 2)], the insertion depth of the steel pipe
into the flange should not be less than 1/2 of the flange thickness.
For the circumferential weld on the upper ring of the flange, when the thickness of the flange plate is
less than 30mm, fillet welds are used on both sides, and the welding leg size is based on the thickness
of the steel pipe wall; when the thickness of the flange plate is greater than or equal to 30mm, the
inside of the upper ring of the flange plate The groove should be processed, and the welding leg size
hr should be determined based on the effective calculated thickness of the weld.
For the circumferential weld of the lower ring of the flange, when the pipe wall is less than 8mm, the
welding leg size hr can be taken as the pipe wall thickness: when the pipe wall is greater than or equal
to 8mm, the outside of the steel pipe should be chamfered, and the welding leg size hr should be based
on the weld Effectively calculate thickness to determine
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DL/T 1762-2017
4.3 Construction and quality requirements of gusset plates and steel pipe welds
The welds between the gusset plate and the steel pipe are shown in Figure 1a) ~Figure 11). The main
stress-bearing welds should meet the quality requirements of the second-level appearance. When the
thickness of the gusset plate is greater than or equal to 8mm, groove welding should be performed
according to the welding regulations; the rib plate welds are secondary welds, usually fillet welds, or
butt joints. + Fillet joint combination welds meet the third-level weld quality requirements. When the
thickness of the gusset plate is greater than or equal to 12mm, groove welding should be performed
according to the welding regulations.
4.4 Dimensions of T-shaped welding joint of gusset plate
For gusset plate T-shaped welded joints, the leg size of the weld can be taken as shown in Table 3. For
stressed welds, the effective calculated thickness of the weld should be calculated
Table 3 Values of leg dimensions for T-shaped welding joints of gusset plates
Welded
seam
fillet weld
(No bevelling)
/< 8mm
Schematic
diagram
Full weld
penetration
Partial weld
penetration
combined
weld
combined
weld
Combined weld (doublesided bevel） /
冫12mm
Full weld penetration
partial weld penetration
penateration
combination
weld
combined
weld
gap
fillet weld
Combined weld (single
side bevel)8mm<t<
12mm
gap
stress
welding
hf1= hf2= 1.2mm
，(
t1,t2)
Secondary
welding
hf1= hf2= 1.0mm
hf2>0.6min(t1,t2)
hf1>0.6min(t1,t2)
hf2>0.85min(t1,t2)
hf1>0.85min(t1,t2)
hr=max (hp, hr=max (hp,
vertical
vertical
dimension of dimension of
groove +b+(1- groove +b+(12.5) b
2.5) b
(t1,t2)
，
14
hf2>0.6min(t1,t2)
hf1>0.6min(t1,t2)
hf2>(0.85-90) min(t1,t2)
hf1>(0.85-90)min(t1,t2)
hr=max(hp,
vertical
dimension of
groove +b+(12.5)b
hr=max(hp, vertical
dimension of groove
+b+(1-2.5)b
hf2>0.5min(t1,t2)
hf1>0.5min(t1,t2)
hr=max(hp,
vertical
dimension of
groove +b+(12.5)b
hf2>0.7min(t1,t2)
hf1>0.7min(t1,t2)
hr=max(hp, vertical
dimension of groove
+b+(1-2.5)b
DL/T 1762-2017
a. For partial penetration welds of slope welding, the penetration depth should be ensured by
controlling the welding process. For partial penetration welds under stress, when using the
parameters in the table, it is necessary to ensure that the non-penetrated part of the weld
should not exceed 25‰ of the thinner thickness. The non-penetrated weld part of the
secondary partial penetration weld should not exceed 40% of the thinner thickness. For
special structural welds where the weld penetration depth cannot be guaranteed, the weld leg
size should be appropriately increased to ensure the effective cross-section of the weld, and
the effective load-bearing cross-section of the weld should be verified and calculated based
on the weld leg size value.
b. the vertical welding leg size (hr) on the side of the groove should be the larger of " hp" and
"vertical size of the groove + b (alignment gap) + (1, 2.5)". That is to say, the welding seam
is required to cover more than 1mm and 2.5mm of the groove edge, and the influence of the
welding plate group on the gap (b) on the calculated size of the welding seam is considered,
and the welding seam should smoothly transition from the vertical plane to the horizontal
plane.
c. Coefficients (0.85, 0.90), for steel pipe towers commonly used Q235, Q345, 20 steel, Q420
steel with a thickness less than or equal to 16mm, select 0.90, and other steel materials can
select 0.85.
4.5 Longitudinal weld arrangement of main pipe
The longitudinal welds of the main pipes used in the tower body or cross arms should be arranged in
the outer direction of the diagonal line of the structure section, and the longitudinal welds of the
substation steel pipe structure brackets should be arranged in the plane inside. When the longitudinal
weld of the steel pipe overlaps with the stiffener plate and auxiliary parts, it should be adjusted and
avoided.
4.6 Requirements for weld layout and corner cutting of stiffeners and accessories
a) The layout of stiffeners and accessories should avoid the longitudinal welds of straight seam welded
pipes. The welds between ribs, flanges, connecting plates and steel pipes should be equipped with
corner cuts to ensure that the main welds are connected. The angle cutting should be in the form of an
arc, and the radius of the arc should be [h + (10~15)] mm to facilitate weld sealing operations and
galvanizing operations. Design confirmation is required for the need to increase the size of the chamfer
arc due to structural reasons, resulting in a reduction in the length of the rib weld. All welds of
galvanized components shall be closed welded.
b) Seat belt hanging holes, hanging point channels on the inside of the station platform, and gusset
plates or bolts should not overlap and interfere with the welds on the steel pipes. The welding positions
of safety belt hanging holes, station platforms, annular stiffeners and other components should be
arranged to avoid affecting the correct installation direction of connecting bolts.
4.7 Tailor welding of circumferential ribs
Circumferential ribs with an arc exceeding 180° can be connected by tailor welding, but the number
of tailors welded plates should not exceed 3.
15
DL/T 1762-2017
4.8 Structural requirements for the slope change of the main material of the tower body and
the hanging points
a) The rigid plane flange connection structure should be used first for the slope change position of the
main material of the tower body.
b) The tension tower hanging wire plate should be stressed as a whole structure or two plates should
be spliced together to form a girth weld with the cross arm main pipe.
4.9 Welding groove form and size
The design of welding groove form and size should comply with the relevant regulations of GB/T985.1
and GB/T 985.2.
4.10 Pipe truss structural welds
In the pipe truss structure, the weld groove form and size of T, K, and Y-shaped joints can be selected
according to Table 4
Table 4 Weld groove forms and dimensions of T, K, and Y-shaped joints of pipe truss structures
Detail A= 180̊-、135̊
Detail B
=150̊、50̊
detail C
= 75̊、30̊
90̊
When 105. Time is 60
40. 60 when larger.
45̊
3715。；1 when
smaller/2
slope size
Bevel angle
maximum
smallest
Branch pipe end maximum
bevel angle
root space
= 40̊、15̊
-
1 /2
Determine according to the angle of the bevel
_
smallest
Detail D
10.
or
when >105. Time
is 45.
_
-
10̊
φ
Bottom weld width
maximum
FCAW-S
SMAW
5mm
GMAW-S
FCAW-G
5mm
FCAW GMAW-S
FCAW-G
-S
SMA when >45. When
6n dishes when
W
6mm 45. 8mm
FCAW-S
SMAW
smallest
2mm
2mm．
When > 90. when >120.
2mm
time,
not time,
not
specified specified
2mm
GMAW-S
FCAW-G
3mm
25°~40°
5mm
15°~25°
3mm
30°~40°
6mm
25°~30°
1Omm
20°~25°
13mm
Weld b
he
>tb
hf
>tb/sin but no
need to exceed
1.75tb
>tb/sin but not more
than 1.7%
When y > 90̊ >6
when <.90̊, t/sin y
Schematic diagram of weld groove form of T, K and Y-shaped joints of pipe truss structure
16
Welds can be over layer to
meet this requirement
>2tb
DL/T 1762-2017
dimensions allowed
for overlay welding
branch pipe
blunt edge
toe area
(detail A range)
side area
(detail B range)
when changing from 135 to
90 degree F, it changes from
0 to tb/2
transition or heel area
(Detail C or D range)
manager
Schematic diagram of round pipe intersecting joint partition
detail B
detail A
Prime weld
detail C
Prime weld
Transition C to D
Prime weld
detail D
Note: is the dihedral angle; tb is the wall thickness of the branch pipe; is the welding fillet size: is the
weld thickness; F is the reinforced welding leg size; the minimum size is, and when it meets tb<6mm,
F>3mm; 6n plate < 12n plate When 12nm1<<2 run, F>6mm); when 12nm1<<2 run, F>6
The necessary width of the weld groove (provided by the primer weld. b Quantity inspection standard.
Can be used as welding material.
17
DL/T 1762-2017
5 Grooving processing and weldment assembly
5.1 Bevel processing
5.1.1 The blanking and bevel processing of weldments should meet the following requirements:
a) Machining, thermal cutting (including plasma arc, flame) and carbon arc gouging cutting
and grooving can be used for blanking and bevelling of weldments.
b) Low-alloy high-strength steel that uses thermal processing methods (such as flame cutting,
plasma cutting, and bevelling) should be polished to remove the contamination layer.
c) When using thermal processing methods or carbon arc gouging to process bevels, they
should be polished after cutting to avoid grooves or cutting edges with a depth greater than
2mm, and the quality of the beveled surface should be inspected.
5.1.2 After the weldment is blanked and beveled, the quality of the blanked and beveled surface
should be inspected to check for oil, paint, and dirt on the beveled surface of the weldment and
the nearby base metal (inner and outer walls are the front and back sides), rust, etc. until
metallic lustre appears. The cleaning range is as follows:
a) Butt weld: the groove on each side is not less than 10mm.
b) Fillet weld: not less than the leg size (hr+15)
c) Submerged arc welding seam: add 5mm to the cleaning range of a) or b).
5.2 Weldment assembly
5.2.1 Group preparation and inspection
5.2.1.1 The spare tooling mold should meet the following requirements:
a) When designing and assembling the tooling mold, it should be considered that the
positioning datum of the tooling is unified with the positioning datum and installation datum
of the workpiece; the tooling should have sufficient strength and rigidity, and should be safe,
reliable, fast, convenient and accurate in action during use. Other characteristics: The
positioning datum should be checked regularly during batch processing and production.
b) The set of tooling molds should be versatile and interchangeable.
c) For components with small batches or complex structures that are not interchangeable, they
should be marked and recorded during production.
5.2.1.2 Before assembling, the following items of quality inspection should be carried out on
the components to be assembled:
a) Part specifications should comply with the drawing requirements.
b) When inspecting the dimensional deviation of parts and components, focus on checking the
length deviation and angle deviation of the welded edges of the parts, the fixed-length cutting
dimensions of steel pipe fittings, the cutting and grooving dimensions of special-shaped plates,
and the margins of the connecting plate installation inserts.
18
DL/T 1762-2017
c) Check the deformation of welded parts. If the deformation deviation during the processing
of straight parts exceeds the specification requirements, it should be corrected; the shape, size,
and position deviation of curved parts (such as the mounting surface of the U-shaped support
of the ladder) should comply with the drawing requirements.
d) Check the quality of the cutting surface and groove surface of the welded parts, and grind
and clean the burrs and cutting slag of the welded parts before assembly.
5.2.1.3 When welding parts are assembled, the surfaces of the two parts to be welded should
be flush, and their offset value should not exceed the following limits: a) The local offset value
of the first and second-level welds should not exceed 10 times the thickness of the weldment.
%, and not larger than 2mm.
b) The local offset value of other welds should not exceed 15% of the thickness of the
weldment, and should not be greater than 3mm.
Note: For pairs of weldments of different thicknesses, the thickness of the weldment will be
calculated as the thinner weldment.
5.2.2 Grouping requirements
Group according to the following requirements:
a) When assembling the connecting plate and the annular plate, a template should be used for
positioning. Appropriate gaps should be left between the annular stiffeners, steel pipes and
connecting plates. The splicing of ring plates should be smooth.
b) When assembling the steel pipe and the necked flange, it should be carried out on the
assembly mold of the flange assembly machine or assembly tooling platform. Adjust the flange
installation size by moving the flange template position. Use pin positioning to ensure that the
mounting holes of the two flanges are consistent with the relative positioning holes of the tire
mould. Adjust the steel pipe support frame and adjust the coaxiality between the steel pipe and
the flange.
c) When assembling the steel pipe and the flat flange, it should be carried out on the assembly
mold of the flange assembly machine or assembly platform. Determine the installation angle
between the flange and the steel pipe by adjusting the angle between the flange master and the
axis of the steel pipe. The contact gap between the steel pipe and the flange should be uniform
and meet the design size requirements of the weld.
d) The assembly of the steel pipe and the plug-in plate should be carried out on the assembly
tooling. Use the pin positioning to determine the position and size of the plug-in plate
installation hole. At the same time, check and determine the size deviation of the plug-in plate
hole margin.
e) Accessories for installing ladders should be welded on the outside of the steel pipe tower,
and it should be ensured that the upper and lower main pipe ladders are on the same axis within
the tower section with the same slope.
f) When assembling welded parts, the assembly gap should be controlled according to the
welding process requirements. After assembly, the local gap exceeds 8mm, but the length is
not greater than 15% of the weld length. Welding is allowed on both sides or one side of the
19
DL/T 1762-2017
groove. The same process is used for surfacing welding on seams, but the following regulations
should be met: it is strictly prohibited to fill the gap with metal materials: layer-by-layer surface
flaw detection and inspection during surfacing, and grinding with a grinding wheel to the
original groove size after surfacing: welding of the surfacing parts Non-destructive testing
should be added to the seams.
g) Before positioning and welding the welded parts together, the positioning reference
structural dimensions of the tooling should be detected and determined. Only when they meet
the requirements of the drawings and specifications can the welded parts be assembled and
positioned welded.
6 welding
6.1 Environmental requirements
6.1.1 The minimum ambient temperature allowed for welding operations should comply with
the following regulations: Q235 steel is not lower than -10℃: Q345 steel is not lower than 10℃
At 0℃: Q420 and Q460 steel shall not be lower than 5℃. When the welding environment
temperature does not meet the requirements, measures to keep warm should be taken. Note:
The lowest ambient temperature can be measured within the range of 1m centred on the
welding site.
6.1.2 When the air humidity exceeds 80%, welding operations should not be performed.
6.1.3 The ambient wind speed during gas shielded welding should not be greater than 2m/s,
and the ambient wind speed during other welding methods should not be greater. When
required, wind protection measures should be taken.
6.1.4 Welding shall not be carried out when the metal surface of the base metal is wet, covered
with ice and snow, or when the welding site is directly attacked by rain, snow, hail, etc.
6.2 Preheating and inter pass temperature
6.2.1 When the thickness exceeds a certain size or the welding ambient temperature is lower
than the minimum ambient temperature requirements, preheating should be carried out
according to the relevant provisions of DL/T 819. When welding different steel materials, the
side with the higher preheating temperature should be selected; when welding the main pipe
and the branch pipe, preheating should be carried out according to the conditions of the main
pipe.
6.2.2 See Table 5
Table 5 for common steel welding preheating temperatures. For steel materials
Plate thickness of the thickest part of the joint'
Steel grades
/ 20
20 < /<40
20
40 <／
<60
60</< 80
／> 80
DL/T 1762-2017
Q345
-a
20
60
80
1 commission
Q390、20
20
60
80
100
120
60
20
80
100
120
150
a " " indicates that preheating measures may not be taken when the
welding environment is above 0°C.
6.2.3 Determination of preheating temperature before welding under special circumstances:
a) When welding different steel types, the preheating temperature should be selected according
to the steel with high strength and higher carbon equivalent.
b) When welding the main pipe and the branch pipe, the preheating temperature should be
selected according to the main pipe.
6.2.4 The temperature between welding layers should not be lower than the minimum
preheating temperature.
6.3 Welding process
6.3.1 General provisions
6.3.1.1 The arc should not be ignited on the surface of the base metal outside the weld of the
workpiece to be welded.
6.3.1.2 Fillers should not be embedded in the assembly gaps or grooves of welded parts for
welding.
6.3.2 Arc starting plate and lead out plate
6.3.2.1 The size of the arc starting plate and lead-out plate of submerged arc welding should
not be less than 50mm × 100mm, and the joints of the welding parts should be bottom-sealed
or padded with flux pads.
6.3.2.2 After welding, mechanical means, carbon arc gouging or gas cutting should be used to
remove the work clamps, arc starting plates and lead-out plates. When using the gas cutting
method, the cutting should be done at a distance of more than 3mm from the surface of the
workpiece. After removing the arc-starting plate and lead-out plate, the remaining parts should
be polished and trimmed, and the surface quality should be checked.
6.3.3 Positioning welds
6.3.3.1 As a formal weld, the welder, welding materials, welding process, welding quantity,
etc. of the tack weld should be the same as the formal weld welding requirements.
6.3.3.2 When steel pipes are butted, the positioning welds shall meet the following
requirements:
21
DL/T 1762-2017
a) When weld positioning is used at the root of the groove, the quality of each positioning
welding spot should be checked after positioning welding. If there are any defects, they should
be removed immediately. If necessary, the positioning welding should be performed again.
b) The height of the positioning weld should not exceed 2/3 of the designed weld height, usually
4mm~6mm. The length of tack welds should be 20mm~40mm, and the spacing between tack
welds should not exceed 400mm. There are generally no less than 3 tack welding points, and
the tack welds should be evenly distributed. For low alloy steel constructed in winter, the
thickness of the tack weld can be increased to 8mm and the length can be 30mm~40mm.
c) When steel pipes are butted longitudinally or circumferentially, the positioning weld length
is 30mm~50mm, and the weld spacing is 150mm~250mm.
d) Positioning welds should not be arranged at intersections of welds or places where the
direction of the welds changes drastically.
e) Defects such as cracks, pores, and slag inclusions on the positioning welds should be
removed.
6.3.3.3 The length and number of tack welds for the combination of steel pipe and flange should
be arranged according to the requirements of Table 6.
Table 6 Length and number of tack welds for steel pipe and flange combinations
Nominal
pipe
diameter
mm
granule 200
Locating weld length
Locating
weld points
15～30
not less than 3
200 < granule 300
20～40
not less than 4
3 commission < 5
25～40
not less than 5
500 < 7 commission
30～40
not less than 6
> 700
35～50
not less than 7
6.3.3.4 For welds that require preheating, preheating should be carried out within 150mm on
both sides of the weld during positioning welding. The preheating temperature shall be as
specified in the regulations.
The specified preheating temperature is 20℃~30℃.
6.3.3.5 For tack welding of primary and secondary butt welds requiring penetration, welding
can only be transferred to the next process after passing the inspection.
6.3.3.5 Welding and removal of welds of work clamps and temporary positioning parts:
a) When welding components such as tools and fixtures, the arc starting point and arc extinction
point should be on the fixture and other components.
22
DL/T 1762-2017
b) When dismantling components such as tools and fixtures, it is strictly forbidden to use
hammering, and thermal cutting or grinding wheel cutting should be used to remove them. The
base material of the workpiece must not be damaged. After cutting, it should be smoothed with
a grinding wheel and inspected for surface cracks.
6.3.4 Welding
6.3.4.1 The welding operation instructions should be prepared in accordance with the
provisions of 3.7, and include the reasonable welding sequence and the requirements for
measures for multiple welders to weld one component at the same time. During the welding
process, welding should be carried out in accordance with the welding methods and welding
parameters specified in the welding operation instruction. The actual welding parameter
changes should be limited to the range specified in DL/T 868.
6.3.4.2 The support structure of the weldment should be decided based on the bearing capacity
of the root layer weld bead.
6.3.4.3 The molten pool should be filled when the weld bead is closed. When welding multilayer or multi-pass welds, the welder should pass the self-inspection layer by layer before
welding the sub-layer welds. Multi-layer and multi-channel welding joints should be staggered
by more than 30mm.
6.3.4.4 For double-sided welds requiring full penetration, the welding process of single-sided
welding and double-sided forming should be adopted. When root cleaning measures are taken,
the number of welds on the non-root cleaning side should not be less than three layers. After
root cleaning, the contaminants in the groove should be removed according to the requirements
of 5.1.2.
6.3.4.5 Supervise and inspect the welding parameters, number of welding layers, cleaning
conditions between layers, interlayer appearance quality, weld interlayer temperature,
preheating temperature, root cleaning quality, and welding deformation to confirm that they
meet the requirements of the welding operation instructions. Require.
6.3.4.6 It is advisable to control welding deformation by adjusting welding parameters (such
as reducing welding current) and adjusting welding sequence. Welding deformation can also
be controlled by methods such as reverse deformation and rigid fixation.
6.3.4.7 When the temporary support is removed, it should not be removed by hammering. The
weld should be mechanically polished, oxygen-gas flame or carbon arc gouging should be
removed about 3mm from the surface of the base metal of the weldment. If necessary, surface
non-destructive testing should be used to confirm Surface Quality.
6.3.4.8 After welding is completed, the welder should clean up the spatter, slag, etc. on the
surface of the weld and the base metal, and check the appearance quality. Appearance quality
defects or weld defects that affect the quality of galvanizing should be ground or partially
repaired before galvanizing, and the repaired weld should maintain a smooth transition from
the original weld. Weld repairs shall comply with the provisions of Chapter 9. After the weld
has passed the welder's self-inspection, and the second-level and above welds have passed the
welder or welding machine operator's self-inspection, the welder should put his own steel
stamp code on a visible place 50mm away from the end of the weld, and it should be clearly
visible after anti-corrosion treatment.
23
DL/T 1762-2017
6.4 Correction of weldments
6.4.1 Operating process procedures should be prepared during thermal orthopaedics. The
operating process procedures should at least include the form and degree of deformation,
heating zone, heating temperature, heating and cooling methods, time, temperature
measurement method, orthopaedic method, etc. For materials of Q420 and above grade, when
using thermal orthopaedic process, thermal orthopaedic process evaluation should be carried
out.
6.4.2 When local heating is used for orthopaedics, the temperature of the heating zone should
be controlled below 800°C.
6.4.3 When the curvature of non-main material components is less than 10°C, cold
straightening can be carried out. However, when the ambient temperature is below 0°C,
materials of grade Q420 and above are not allowed to be cold straightened: when the ambient
temperature is below -12°C, all materials are not allowed to be cold straightened.
6.5 Afterheat
6.5.1 For low-alloy structural steels that are highly sensitive to cold cracking or weldments that
are highly constrained, post-heating measures should be taken immediately after welding.
6.5.2 The heating width of post-heating should be 3 times the thickness of the base metal on
each side of the weld and not less than 100mm.
6.5.3 The post-heating temperature is generally 250℃~350℃. The holding time is related to
the post-heating temperature, weld metal thickness, etc., and should not be less than 30 minutes.
After the holding time is reached, it should be slowly cooled to normal temperature.
6.5.4 Weldments that undergo post-weld heat treatment immediately after welding do not need
to undergo post-heating.
6.6 Post-weld heat treatment
6.6.1 When the design document or welding procedure qualification has post-weld heat
treatment requirements, post-weld heat treatment should be carried out on the weldment in a
timely manner after welding. The heating width, temperature measurement and control
requirements, and insulation width of post-weld heat treatment shall be implemented in
accordance with DL/T 819.
6.6.2 The post-weld heat treatment temperature should be 600℃~650℃, and the constant
temperature time is calculated as 1h for every 25mm thickness, with a minimum of 0.5h.
7 quality inspection
7.1 Appearance inspection of welded joints
7.1.1 All welds should be visually inspected. The appearance inspection is mainly based on
visual inspection, and the weld inspection ruler or magnifying glass should be used to assist.
When one of the following situations occurs, the surface of the weld should be inspected nondestructively. Magnetic particle or penetrant inspection can be used, in accordance with NB/T
47013.4, NB/T47013.5 regulations:
24
DL/T 1762-2017
a) When cracks are found in the visual inspection of welds, 100% surface non-destructive
testing of the same batch of similar welds should be carried out.
b) When cracks are suspected in the appearance inspection of the weld, surface non-destructive
testing should be carried out on the suspected parts.
c) When the steel tube tower design drawings specify, surface non-destructive testing should
be carried out.
d) The fillet welds connecting the flange of the UHV steel pipe tower and the steel pipe plugin type shall undergo 100% surface non-destructive testing.
7.1.2 Exceeding appearance defects that can be eliminated by polishing should be recorded.
7.1.3 Macroscopic dimensional inspection of welded parts should be carried out according to
the requirements of the drawings. For important components, welding deformation should be
monitored during the welding process, and final dimensional inspection should be performed
after welding or post-weld heat treatment is completed.
7.2 Internal quality inspection of welded joints
7.2.1 Internal quality inspection should be carried out for primary and secondary welds.
Internal quality inspection of welded joints should be carried out 24 hours after welding is
completed. Only after passing the appearance quality inspection or passing the repair or
grinding can the internal quality inspection be carried out.
7.2.2 Internal quality inspection adopts non-destructive testing method. Non-destructive testing
methods, technical conditions and quality classification should be based on the characteristics
of the component type. The regulations shall be implemented in accordance with the provisions
of DL/T 1611, DL/T 820, DL/T 542, GB/T 11345, GB/T 29712, GB/T 3323 and JG/T 203
respectively.
7.2.3 For primary and secondary welds whose design requires full penetration, ultrasonic
testing methods should be used to detect internal defects. When there are doubts about
ultrasonic testing, other methods can be used for supplementary inspection and verification.
7.2.4 The detection ratio of primary welds should be 100%, and the detection ratio of secondary
welds should be 20%.
Note: The calculation method of the internal quality inspection ratio of welds should be based
on each weld, and the inspection length should not be less than 200mm. When the weld length
is less than 200mm, internal quality inspection of the entire weld should be carried out.
7.2.5 Butt welded joints whose base metal thickness is less than 8 mm shall be inspected for
internal defects using the inspection methods specified in DL/T 1611 or DL/T 820.
7.2.6 The combined welds of butt joints and fillet joints can be tested in accordance with DL/T
542, GB/T 11345, and GB/T 29712 standards.
7.2.7 If the weld quality level is not indicated in the design, the inspection shall be based on
the third-level weld quality requirements.
25
DL/T 1762-2017
7.2.8 The repaired primary and secondary welded joints should be 100% subject to nondestructive testing.
8 quality standards
8.1 Weld appearance inspection quality standards
8.1.1 Weld appearance inspection requirements
The appearance of the welding seam should be uniform in shape and beautiful in shape. The
metal transition between welding beads and welding seam and base metal should be smooth.
Welding slag and spatter should be removed cleanly. The appearance quality of welds shall
comply with the requirements in Table 7.
Table 7 Weld appearance inspection and acceptance criteria
serial
project
number
1
Cracks, crater
cracks
Weld
2
3
4
Surface pores
Surface
slag
inclusion
5
6
7
8
9
10
Level 1
Level 2
Grade of weld and corresponding defect
limits
Level 3
not allowed
not allowed
not allowed
not allowed
The depth is not greater than
0,05' and not greater than 0,3;
Not greater than 0
The continuous length shall not
not
mountain and not
undercut
exceed 1 mm and the total
allowed
greater than 0.5,
undercut length on both sides of
length unlimited
the weld shall not exceed 10% of
the total length of the weld.
Notch depth not
greater than 0.05/and
Bad connector
not allowed
not greater than 0.5,
not more than one
weld per 1m0
Not
fully
Not more than 0.2 +
soldered
0.02' and not more
(Referring
to
than
not allowed
insufficient
1.0, total length of
design
defects per 100 welds
requirements)
not greater than 2,0
Not fused
not allowed
Not penetrated
not allowed
b
Not greater than 0.2 + 0.02t
Not greater than 0,
and not greater than 1.0
2 + 0.04t/ and not
Root shrinkage not
greater than 2.0
(concave)
allowed
unlimited length
26
DL/T 1762-2017
Item
a
Grade of weld and
corresponding defect
limits
Level 3
serial
number
Level 1
11
Level 2
Arc Abrasion
Individual arc abrasions
are permitted when the
properties of the base
material are not affected.
non-permissible
Note: / is the thickness of the thinner pipe or plate at the joint.
an Except for the indication of defects in fillet welds, the rest are common to butt and fillet
welds.
When one of the following occurs, it is a failure: in any 300mm continuous length of the weld,
its cumulative length exceeds 25mm: when the length of the weld is less than 300mm, its
cumulative length exceeds 8% of the total length of the weld.
8.1.2 Requirements for weld dimensions
8.1.2.1 The allowable deviation of weld reinforcement and misalignment shall comply with the
provisions of Table 8.
8.1.2.2 The weld widening shall comply with the provisions of Table 9. Among them, the
difference between the maximum width B max and the minimum width B min of the weld shall
not exceed 4.0mm within any 50mm weld length range. Within the entire weld length range
the deviation value is not greater than 5.0mm.
Table 8 Allowable deviation of weld size (mm)
serial
number
project
Allowable deviation
legend
Butt weld
reinforcement
(C)
Level 1
Level 2
B < 20 hour，
B
1
Cfor0、3，0；
B>20 hour， c
Level 3
B < 20-hour， C is 0～
3.5
When B>20, c is 0～
5.0
for 0～4．0
Wrong Side
∆0.1t and <2
2
3
Fillet weld
reinforcement
(C)
When
h ≤6, c is 0～1.5;
When
h >6, c is 0～3.0;
27
∆0.15t and <3
DL/T 1762-2017
4
Angle
(combination)
weld leg size
(hf)
When
h ≤12, c Is 0～3.0;
When
h >12cis 0～4.0;
Table 9 Allowable enlarged dimensions of welds
Welding method
Weld form
Weld width B
Bmin
Bmax
submerged arc
welding
I-shaped weld
b+6
b + 10
Non-I-shaped welds
g+2
g+8
Welding rod arc
welding and gas
shielded welding
I-shaped weld
b+4
b+8
Non-I-shaped welds
g+2
g+6
Note 1: b in the table is the assembly clearance, which should comply with the actual
assembly value required by GB Ding 985.1 and GB Ding 985.2. g is the width of the
groove surface.
Note 2: See Figures 3 and 4 for I-shaped grooves and non-I-shaped grooves.
B
B
B=b+2a
Figure 3 1-shaped groove butt weld
B=g+2a
Figure 4 Non-I-shaped groove butt weld
8.1.2.3 The leg size h of the fillet welds of the T, K, and Y-shaped joints of the pipe truss
structure shall be in accordance with Table 10. Table 10 does not apply to the case where the
branch/rod inclination angle @ is less than 30° or the branch/main pipe diameter ratio d/D is
not greater than 1/3.
Table 10 Fillet weld leg dimensions for T, K, and Y-shaped joints of pipe truss structures
Minimum Solder Pin Size
perspectives
roots < 60̊
Legend = 0,
Square
he=t
he=1.07t
1.5t
1.5t
Taking the larger of 1.5
and 1.4t+Z
28
DL/T 1762-2017
side 100̊
t
1.4t
1 lang on the
side. ,110̊
1.1t
1.6t
sidebar 110̊、
120̊
toe > 120̊
1.75t
1.8t
1.2t
t (trimming）
1.5t
1.4t <trimming>
2.0t
bevelling60̊-90̊
(penetration)
toe area
root zone
side area
toe area
side area
root zone
Note 1: ' is the thickness of the thinner part; is the effective thickness of the fillet
weld, that is, the minimum distance from the root of the weld to the surface of the
weld; z is the size of the root fillet weld that is not penetrated, and z is determined by
the welding process evaluation.
Note 2: The allowable root gap is 0mm, 5mm: when the root gap is less than 1.6mm,
the value should be increased appropriately.
Note 3: When > 120. The edges should be cut off.
8.1.2.4 Within any continuous weld length of 300mm, the straightness of the weld edge along
the weld axis is shown in Figure 5, and its value should comply with the provisions of Table
11; within any 25mm length of the weld, the weld reinforcement C max the allowable deviation
value of ~C min is not greater than 2.0mm, see Figure 6.
300
Figure 5 Schematic diagram of weld edge straightness
29
DL/T 1762-2017
Figure 6 Schematic diagram of weld surface concavity and convexity
Table 11 Allowable deviation of weld edge straightness
Allowable deviation value of weld edge straightness 丆
Welding method
submerged arc welding
3．0
Welding rod arc welding and gas shielded
welding
2．0
8.1.2.5 The angular deformation and lengthwise welding deformation of the welded joint shall
comply with the requirements of the design documents, quality specifications and welding
procedure specifications.
8.2 Non-destructive testing quality standards for welded joints
8.2.1 The quality level of non-destructive testing of the surface of welded joints should comply
with level 1 of NB/T47013.4 or NB/T47013.5.
8.2.2 The detection levels of ultrasonic testing and radiographic testing of primary and
secondary butt welds with base metal thickness greater than 8 mm shall comply with the
provisions of Table 12.
Table 12 Inspection methods and grade requirements for internal quality of welds
Testing and acceptance levels
Detection
method
Ultrasonic
testing
According
to the
standard
Testing and
acceptance
requirements
First class weld
GB/T
11345
Detection level
B class
B class
GB/T
29712
Acceptance level
2class
3class
Transillumination
technical level
B class
B class
quality level
Il class
Ill class
GB/T 3323
Radiographic
testing
Secondary weld
8.2.3 The internal quality inspection of primary and secondary welds with base metal thickness
not greater than 8 mm shall comply with the quality requirements of DL/T 1611.
30
DL/T 1762-2017
8.2.4 Quality standards for combined welds. The quality of welds requiring penetration shall
be evaluated according to ultrasonic testing in Table 12. Other T-shaped joint welds are tested
according to DL/T 542, and the weld quality is accepted according to the technical
requirements.
9. Treatment of unqualified welded joints
9.1 Surface defects such as pores, slag inclusions, welding nodules or excessive reinforcement
should be removed by grinding first, and welding repairs should be carried out if necessary.
9.2 Defects such as root depressions, arc craters, insufficient weld size, and undercuts should
be repaired by welding.
9.3 Internal defects such as cracks and lack of fusion should be handled according to the
following provisions:
a) Remove these defects first, and use penetrant (PT) or magnetic particle (MT) methods to
detect if necessary.
b) The removal length should be 50mm longer than both ends of the defect range.
c) For crack defects in thick and large parts, measures should be taken to prevent the cracks
from continuing to expand before removal.
d) Carry out repair welding according to the proposed welding repair process.
9.4 When removing defects, grinding should be done with a grinding wheel, carbon arc gouging
or other mechanical methods can also be used. After the defects are removed, the bottom of the
groove should have a smooth transition to meet the requirements for welding repair. Carbon
arc gouging should remove the contaminated layer.
9.5 Before repair, the welding repair process should be formulated, evaluated and verified.
9.6 The number of repairs at the same position of the weld should not exceed 2 times, and the
repair status will be recorded in the product quality file.
9.7 Polish the completed reworked weld to form a smooth weld that is flush with the surface
of the adjacent base metal.
9.8 Reworked or reworked welds should be inspected according to the original method, and
the same technology and quality standards should be used.
10 Welding technical documents
Welding technical documents should be collected, summarized and archived for future
reference in a timely manner. Information should be complete, accurate and traceable. Main
technical information includes:
a) Welding procedure qualification report and welding procedure specifications.
b) Welding qualification (copy).
c) Quality guarantee certificate and re-inspection report of base metal and welding materials.
31
DL/T 1762-2017
d) Welding construction inspection records and reports.
e) Welding heat treatment records and reports.
f) Welding final inspection records and reports.
g) Repair or rework records.
h) Opinions on handling major welding technical issues.
i) Material changes and substitute witness information.
j) Welding engineering technology summary and quality evaluation report.
32