RECOMMENDED PRACTICE
DNVGL-RP-0034
Edition September 2019
Steel forgings for subsea applications
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FOREWORD
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DNV GL recommended practices contain sound engineering practice and guidance.
©
DNV GL AS September 2019
Any comments may be sent by e-mail to rules@dnvgl.com
This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this
document. The use of this document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibility
for loss or damages resulting from any use of this document.
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This document is a republished version of the first edition of DNVGL-RP-0034 (February 2015). No changes
have been made to the content of this document.
Acknowledgements:
This recommended practice was developed by a Joint Industry Project (JIP). The work was performed by
DNV GL and discussed in regular project meetings and workshops with individuals from the participating
companies. They are hereby acknowledged for their valuable and constructive input. In case consensus has
not been achievable, DNV GL has sought to provide acceptable compromise.
Sponsors of the JIP included the following organisations:
Aker Solutions
Brück
Celsa
Chevron
Det Norske
Dril-Quip
Ellwood Group
Eni
ExxonMobil
FMC
Frisa
GE
Japan Steel Works
Lundin
OneSubsea
Petrobras
Ringmill
Scana Subsea
Shell
Statoil
Changes - current
CHANGES – CURRENT
Total
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Further organisations have participated in the review process. DNV GL is grateful for the valuable cooperations and discussions with individuals in these organisations.
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Changes – current.................................................................................................. 3
Section 1 General.................................................................................................... 5
1.1 Introduction......................................................................................5
1.2 Scope and application.......................................................................5
1.3 Steel forging classes.........................................................................5
1.4 Purchase order information.............................................................. 6
1.5 Normative and informative references............................................. 6
1.6 Definitions.........................................................................................8
1.7 Verbal forms..................................................................................... 8
1.8 Abbreviations.................................................................................... 9
Section 2 Quality assurance and quality control................................................... 10
2.1 Quality management system.......................................................... 10
2.2 Manufacturing procedure specification........................................... 10
2.3 Inspection and test plan.................................................................11
2.4 Marking and traceability................................................................. 11
2.5 Certification and documentation..................................................... 12
Section 3 Technical provisions.............................................................................. 13
3.1 Manufacturing practices..................................................................13
3.2 Chemical composition..................................................................... 14
3.3 Mechanical testing.......................................................................... 15
3.4 Metallographic examination............................................................ 18
3.5 Non-destructive testing.................................................................. 19
3.6 Dimensional inspection................................................................... 20
3.7 Repair............................................................................................. 20
Section 4 Manufacturing procedure qualification.................................................. 22
4.1 General........................................................................................... 22
4.2 Qualification testing........................................................................22
4.3 Validity............................................................................................25
Changes – historic................................................................................................ 27
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Contents
CONTENTS
SECTION 1 GENERAL
1.1 Introduction
This recommended practice (RP) contains criteria, technical requirements and guidance on qualification,
manufacture and testing of carbon and low alloy steel forgings for subsea applications.
The RP has been written for general world-wide application. Governmental regulations may include
requirements in excess of the provisions given by this RP.
a)
b)
c)
d)
e)
f)
g)
provide an internationally acceptable and harmonised standard for carbon and low alloy steel forgings
provide for reduced lead time, enhanced stock keeping and interchangeability
provide consistent quality to increase reliability/integrity of subsea equipment
simplify the risk assessment process
serve as a contractual reference document between manufacturers and purchasers
serve as a guideline for designers, suppliers, purchasers and regulators
comply with and complement existing industry codes for subsea equipment.
The RP is divided into four main sections:
— Sec.1 General: Contains introduction, scope and application, information to be supplied by purchaser,
normative and informative references, definitions and abbreviations
— Sec.2 Quality assurance and quality control: Contains requirements for quality management system,
manufacturing procedure specification, inspection and test plan, marking and traceability, documentation
and certification
— Sec.3 Technical provisions: Contains requirements for manufacture, testing and inspection of production
parts
— Sec.4 Manufacturing procedure qualification: Contains requirements for qualification of manufacturing
processes, methods, procedures and validity.
1.2 Scope and application
The steel forgings covered herein are intended for components in subsea equipment. Typical applications
include:
a)
b)
c)
d)
e)
subsea wellhead and tree equipment as per ISO 13628-4 or API 17D
completion/workover riser systems as per ISO 13628-7 or API 17G
subsea structures and manifolds as per ISO 13628-15 or API 17P
flexible pipe as per ISO 13628-11 or API 17B
drill-through equipment as per ISO 13533 or API 16A.
The material grades covered are carbon steels, micro-alloyed steels, low alloy steels and modified grades
thereof as per material groups 1 and 2 in API 20B.
This RP is not intended to inhibit a vendor from offering, or the purchaser from accepting, alternative
materials or manufacturing processes. This can be particularly applicable where there is innovative or
developing technology. Where an alternative is offered, it is the responsibility of the vendor to identify any
variations from this RP and provide details to the purchaser.
1.3 Steel forging classes
This RP establishes requirements for three steel forging classes (SFC) designated SFC 1, SFC 2, and SFC
3. These SFC designations define different levels of forged product technical, quality and qualification
requirements.
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The objectives of this RP are to:
All classes are intended for equipment that shall meet product specification level (PSL) 3 and 3G
requirements in the referenced industry codes, e.g. ISO 10423 or API 6A. The three forging classes reflect
increasing criticality as defined by the end user and, hence, increasing requirements from SFC 1 to SFC 3:
— SFC 1 is intended for less critical components, e.g. components that are not subjected to continuous
exposure to flowing hydrocarbons or components with simple shapes.
— SFC 2 is intended for pressure containing and/or load bearing components that are of significant enough
size and complexity to warrant additional mechanical testing and surveillance.
— SFC 3 is intended for fatigue sensitive pressure containing and/or load bearing components.
1.4 Purchase order information
The purchaser shall provide at least the following information in the order:
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
l)
m)
n)
o)
that the forging(s) shall be made according to this RP;
the steel forging class (SFC);
the steel designation (name or number);
the quantity of forgings required;
the drawing number(s) containing the dimensions, tolerances and surface finish;
the position and thickness of the critical section(s) in the part;
the minimum design temperature (MDT)/Charpy V-notch (CVN) test temperature;
the specified minimum yield strength (SMYS);
the marking requirements for the forging(s);
the type of certification document
whether the forging(s) shall be ISO 15156-2 or NACE MR0175 compliant;
whether the forging(s) shall be subjected to simulated post weld heat treatment (SPWHT);
whether forging plan/sketch shall be submitted for review or approval prior to production;
whether test sample drawing shall be submitted for review or approval prior to production;
whether ultrasonic testing (UT) procedure and scan plan shall be submitted for review or approval prior
to production;
whether magnetic particle testing (MT) procedure and test coverage description shall be submitted for
review or approval prior to production;
whether manufacturing procedure specification (MPS) shall be submitted for review or approval prior to
production;
whether inspection and test plan (ITP) shall be submitted for mark-up, review or approval prior to
production;
whether manufacturing procedure qualification (MPQ) report shall be submitted for review or approval
prior to production;
whether any additional requirements shall apply.
p)
q)
r)
s)
t)
1.5 Normative and informative references
The codes and standards in Table 1-1 and Table 1-2 include provisions and guidance which, through reference
in this text, constitute provisions and guidance of this RP. The latest edition applies unless dated references
are given.
Other recognised codes and standards may be used provided it can be demonstrated that these meet or
exceed the requirements of the referenced codes and standards.
Any deviations, exceptions and modifications to the codes and standards shall be documented and agreed
between the manufacturer and purchaser.
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Table 1-1 Normative references
Heat Treatment and Testing of Carbon and Low Alloy Steel Large Cross Section and
Critical Section Components
API Spec 20B
Open Die Shaped Forgings for Use in the Petroleum and Natural Gas Industry
ACCP-CP-1
American Society for Nondestructive Testing Central Certification Program
ASME BPVC-V
ASME Boiler and Pressure Vessel Code (BPVC), Section V: Nondestructive Examination
ASTM A370
Standard Test Methods and Definitions for Mechanical Testing of Steel Products
ASTM A388
Standard Practice for Ultrasonic Examination of Steel Forgings
ASTM A604
Standard Practice for Macroetch Testing of Consumable Electrode Remelted Steel Bars
and Billets
ASTM A694
Standard Specification for Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings,
Valves, and Parts for High-Pressure Transmission Service
ASTM A707
Standard Specification for Forged Carbon and Alloy Steel Flanges for Low-Temperature
Service
ASTM A751
Standard Test Methods, Practices, and Terminology for Chemical Analysis of Steel
Products
ASTM A788
Standard Specification for Steel Forgings, General Requirements
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API RP 6HT
ASTM E110
Standard Test Method for Indentation Hardness of Metallic
Materials by Portable Hardness Testers
ASTM E112
Standard Test Methods for Determining Average Grain Size
ASTM E381
Standard Method of Macroetch Testing Steel Bars, Billets, Blooms, and Forgings
ASTM E709
Standard Guide for Magnetic Particle Testing
ASTM E1820
Standard Test Methods for Measurement of Fracture Toughness
EN 10204
Metallic products - Types of inspection documents
ISO 643
Steels - Micrographic determination of the apparent grain size
ISO 9001
Quality Management Systems – Requirements
ISO 9712
Non-destructive testing - Qualification and certification of NDT personnel
ISO 10423/API Spec 6A
Petroleum and natural gas industries - Drilling and production equipment - Wellhead
and christmas tree equipment/Specification for Wellhead and Christmas Tree
equipment
ISO 10474
Steel and steel products - Inspection documents
ISO 12135
Metallic materials - Unified method of test for the determination of quasistatic fracture
toughness
ISO 15156-2/NACE
MR0175
Petroleum and natural gas industries - Materials for use in H2S-containing
environments in oil and gas production - Part 2: Cracking-resistant carbon and lowalloy steels, and the use of cast irons/Petroleum and natural gas industries - Materials
for use in H2S-containing environments in oil and gas production
ISO/IEC 17020
Conformity assessment - General criteria for the operation of various types of bodies
performing inspection
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ISO/IEC 17025
General requirements for the competence of testing and calibration laboratories
Table 1-2 Informative references
API RP 17B
Recommended Practice for Flexible Pipe
API Spec 16A
Specification for Drill Through Equipment
ISO 13533
Petroleum and natural gas industries - Drilling and production equipment - Drillthrough equipment
production systems - Part 1: General requirements and recommendations/Design and
Operation of Subsea Production Systems-General Requirements and Recommendations
ISO 13628-4/API Spec 17D
Petroleum and natural gas industries - Design and operation of subsea production
systems - Part 4: Subsea wellhead and tree equipment/Design and Operation of
Subsea Production Systems-Subsea Wellhead and Tree Equipment
ISO 13628-7/API RP 17G
Petroleum and natural gas industries - Design and operation of subsea production
systems - Part 7: Completion/workover riser systems/Recommended Practice for
Completion/Workover Risers
ISO 13628-11
Petroleum and natural gas industries - Design and operation of subsea production
systems - Part 11: Flexible pipe systems for subsea and marine applications
ISO 13628-15/API RP 17P
Petroleum and natural gas industries - Design and operation of subsea production
systems - Part 15: Subsea structures and manifolds/Design and Operation of Subsea
Production Systems - Subsea Structures and Manifolds
1.6 Definitions
Table 1-3 Definitions
critical section(s)
section(s) of the forging in which mechanical properties have to meet the specified minimum
requirements and are deemed critical to the design and safe operation of the component.
1.7 Verbal forms
Table 1-4 Verbal forms
shall
verbal form used to indicate requirements strictly to be followed in order to conform to the
document.
should
verbal form used to indicate that among several possibilities one is recommended as particularly
suitable, without mentioning or excluding others, or that a certain course of action is preferred
but not necessarily required.
may
verbal form used to indicate a course of action permissible within the limits of the document.
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Petroleum and natural gas industries - Design and operation of subsea
ISO 13628-1/API RP 17A
1.8 Abbreviations
Table 1-5 Abbreviations
carbon equivalent (international institute of welding)
CS
carbon steel
CTOD
crack tip opening displacement
CVN
Charpy V-notch
DAC
distance amplitude correction
DGS
distance gain-size
EAF
electric arc furnace
ESR
electro slag re-melting
FBH
flat bottom hole
ITP
inspection and test plan
LAS
low alloy steel
LR
ladle refining
MDT
minimum design temperature
MPQ
manufacturing procedure qualification
MPS
manufacturing procedure specification
MT
magnetic particle testing
MTR
material test report
NDT
non-destructive testing
PWHT
post weld heat treatment
QMS
quality management system
RP
recommended practice
SFC
steel forging class
SMYS
specified minimum yield strength
SPWHT
simulated post weld heat treatment
UT
ultrasonic testing
VAR
vacuum arc re-melting
VD
vacuum degassing
VT
visual testing
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CE (IIW)
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SECTION 2 QUALITY ASSURANCE AND QUALITY CONTROL
2.1 Quality management system
The forging manufacturers and steel manufacturers shall have a certified quality management system (QMS)
conforming to ISO 9001.
2.2 Manufacturing procedure specification
All production shall be based on an manufacturing procedure specification (MPS) established by the forging
manufacturer. The MPS shall describe how the specified properties will be achieved and verified. The MPS
shall address all factors that affect the quality and reliability of production including all subcontractors
applied. Every principal production step from starting material to shipment of finished product(s) shall be
addressed. References to the detailed procedures used for the execution of all steps shall be included.
As a minimum, the MPS shall include the information in Table 2-1.
Table 2-1 Content of MPS
a) A descriptive title and a unique identification number with revision control
1) General
b) Description of product(s) and size range(s)
c) Reference to applicable standards and specifications
d) Reference to MPQ(s)
a) Steel manufacturer, steel grade, melt practice, refining and casting method
2) Starting materials
b) Specification for chemical composition and carbon equivalent (CE)
c) Ingot type
d) Methods and practices for ingot discard
a) Forging method, e.g. open die, closed die or ring rolling
b) Forging press/equipment capacity, as applicable
c) Hot work temperature range and method of temperature monitoring during forging
3) Forging
d) Description of basic forging steps, i.e. sequence of upsetting, drawing, etc
e)
Forging reduction calculation method for each step and minimum overall forging
reduction ratio
f)
Sketch of forging(s) including prolongation, if used, in as-forged condition
a) Heat treat condition of supply, e.g. quenched and tempered
Sketch of forging(s) including prolongation, if used, at time of heat treatment, if any
b) different from as-forged geometry. Finished geometry, if known, shall be given with
dashed lines
c) Maximum thickness of forging(s) at time of heat treatment
4) Heat treatment
Description of furnace loading practice with typical sketch(es) showing maximum loading
d) weight, location and minimum spacing of parts in the furnace, location of prolongation or
sacrificial part and location of contact thermocouples/heat sinks
e) Description of heat treatment cycles, temperatures and times
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f)
Minimum quench tank size/volume
g) Quenching medium and type of agitation
h) Quenching medium start and finish temperature and maximum transfer time to quench
i)
Maximum surface metal temperature at removal from quench tank including how and
when temperature is measured
a) Specified tensile, Charpy V-notch (CVN) and surface hardness testing
b)
Sketch showing sampling position and specimen orientation in prolongation or sacrificial
forging, as applicable
5) Mechanical testing,
metallographic
c) Sketch with the locations for surface hardness testing
examination, and
d) Grain size determination
product analysis
e) Inclusion rating for SFC 3
f)
Chemical composition determined as product analysis for SFC 3
a) Visual testing
6) Non-destructive
testing, as applicable
b) Magnetic particle testing, including sketch or description of test coverage
c) Ultrasonic testing, including scan plan
8) Final certification
a) Dimensional control
b) Method, extent, and position of marking
a) Type of certificate
b) Associated records and documentation
2.3 Inspection and test plan
The forging manufacturer shall establish an inspection and test plan (ITP) for SFC 2 and SFC 3. The ITP
shall have a reference to the relevant MPS and shall list the sequence of activities contained in the MPS.
Manufacturers may use their own ITP format, but it shall as a minimum include:
a)
b)
c)
d)
e)
f)
all principal production, inspection and testing activities
location of activity
associated procedure or specification including acceptance criteria governing the activity
verifying document to be used for recording inspection and test results
forging manufacturer’s intervention activities
columns for intervention by purchaser and 3rd party.
2.4 Marking and traceability
The forgings shall be marked to ensure full traceability to the heat or re-melt ingot (as applicable), heat
treatment lot and the certificate representing the forgings. Additional marking shall be as specified in the
purchase order.
Each forging shall be marked with a low stress marking method on a position as stated in the MPS.
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7) Dimensional
control and marking
2.5 Certification and documentation
Certification of production forgings shall be as specified by the purchaser. Any of the following certification
documents are applicable:
— A manufacturer’s test report (MTR) giving the results of all specified tests and inspections.
— An inspection document type 3.1 or 3.2 according to ISO 10474 or EN 10204.
The certificates shall be supplied by the manufacturer to the purchaser and shall, as a minimum, give the
following particulars:
a)
purchaser’s name, order number and part number
b)
forging manufacturer’s name and order number
c)
description of forging(s) including quantity and drawing number(s)
d)
reference to this RP
e)
steel designation and SFC
f)
reference to the applicable MPS
g)
steelmaker’s name
h)
steelmaking process including secondary refining
i)
forging method and forging reduction ratio
j)
name of heat treat subcontractor, if applicable
k)
heat number(s) and heat treat lot number(s)
l)
heat treatment temperatures, soaking times, quenching medium and transfer time from furnace
to quench tank
m)
prolongation or sacrificial part dimensions
n)
prolongation or sacrificial part dimensions
o)
results of tensile, CVN, surface hardness, metallographic and any other testing required
p)
NDT report(s)
q)
marking of forging(s).
The certificates shall be accompanied by documentation and records as follows:
r)
heat treatment chart(s) and furnace loading sketch(es)
s)
test plan/sketch showing locations for tensile, CVN, surface hardness, metallographic and any
other testing required
t)
NDT procedure(s)
u)
dimensional inspection report(s)
v)
for SFC 2 and SFC 3, copy of certificate(s) from steelmaker.
The manufacturer shall maintain documentation and records of relevant manufacturing procedure
qualification (MPQ).
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SECTION 3 TECHNICAL PROVISIONS
3.1 Manufacturing practices
3.1.1 General
All manufacturing shall be based on the MPS, the associated MPQ (for SFC 2 and SFC 3), and the
requirements of this RP.
3.1.2 Melting, refining, and casting
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3.1.2.1 The steel shall be melted using the electric arc furnace (EAF) followed by secondary refining such as
ladle refining (LR) and vacuum degassing (VD). Secondary re-melt processes such as electro slag re-melting
(ESR) and vacuum arc re-melting (VAR) may also be used.
3.1.2.2 The steel shall be fully killed and made to a fine grain practice. See also [3.4].
3.1.2.3 The steel for SFC 3 shall be treated for inclusion shape control. When Ca treatment is used, Ca shall
not exceed 0.005%. See also [3.4].
3.1.2.4 The steel shall be ingot cast with bottom pouring, ingot cast with top pouring in vacuum, or
continuous cast. Adequate top and bottom ingot discards shall be made to ensure freedom from piping and
harmful segregations in the finished forgings. Surface and skin defects, which may be detrimental during the
subsequent working and forming operations, shall be removed.
3.1.2.5 Repair by welding on ingots, blooms or billets shall not be permitted.
3.1.2.6 Melting, refining and casting practices shall be as stated in the MPS.
3.1.3 Forging
3.1.3.1 Forgings shall be made by any of the following methods: Open die, closed die or ring rolling.
3.1.3.2 The material shall be hot worked, and shall be forged as close as practical to the finished shape and
size.
3.1.3.3 The hot work temperature shall be monitored during the forging process by pyrometer or equivalent
equipment.
3.1.3.4 The overall forging (total hot work) reduction ratio shall be minimum 4.0:1 for all classes, with the
following considerations:
a)
b)
c)
d)
The initial free upsetting operations of the as cast ingot shall not be considered as part of the overall
forging reduction ratio
Upsetting following cogging or drawing may be considered as part of the overall forging reduction ratio.
If upsetting following cogging or drawing is to be considered, the overall forging reduction ratio shall be
minimum 6.0:1
For ring rolling or mandrel forging, punching or piercing of holes shall not be considered as part of the
overall forging reduction ratio
The overall reduction ratio shall be sufficient to produce a wrought structure throughout the entire part.
3.1.3.5 The hot work reduction ratio for a single hot work operation and the total hot work reduction ratio
shall be calculated according to API 20B.
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3.1.3.6 For ring rolling or mandrel forging, the initial cross-sectional area shall be as-punched or pierced
wall thickness times as-punched or pierced height. The final cross-sectional area shall be final wall thickness
times final height.
3.1.3.7 For closed die forging, the reduction ratio shall meet the requirement of this RP prior to the closed
die operation.
3.1.3.8 Repair by welding on forgings shall not be permitted.
3.1.4 Heat treatment
3.1.4.1 General
Forgings shall be supplied in the heat treat condition as stated in the MPS.
Where forgings are to be quenched and tempered and cannot be hot worked close to shape, they shall be
rough machined as close as practical to final shape and size prior to heat treatment.
3.1.4.2 Heat treatment practices
Heat treatment practices shall comply with the requirements in API 6HT and the following additional
requirements:
a)
b)
c)
Qualification of heat treatment equipment shall be according to ISO 10423 or API 6A, Annex M.
No stacking of SFC 3 forgings shall be allowed during heat treat operations.
In the case of SFC 1 and SFC 2 ring forgings and bars, etc, stacking shall be allowed provided that
—
—
—
—
spacers or cradle between layers are used
proper agitation is applied for heat transfer
the stacking is shown in the MPS
the stacking was used during heat treatment for MPQ of SFC 2.
d)
In cases where the 90 seconds transfer time from furnace to quench tank is not achievable or applicable
due to hardenability/thickness, transfer time shall be as qualified and stated in the MPS.
e)
The temperature monitoring for SFC 2 and SFC 3 shall be done by the attached thermocouple monitoring
method described in API 6HT.
f)
Surface metal temperature at removal from quench tank shall be measured.
3.1.4.3 Simulated post weld heat treatment
Where forgings are subjected to subsequent welding and post weld heat treatment (PWHT), as specified by
the purchaser, a SPWHT shall be carried out. See [3.3.8].
3.2 Chemical composition
3.2.1 Heat analysis
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Heat analysis shall be performed for all classes according to ASTM A751. The heat analysis shall comply with
the specified limits and the requirements given in Table 3-1.
3.2.2 Product analysis
Product analysis shall be performed for SFC 3 according to ASTM A751. The product analysis shall comply
with the specified limits and the requirements in Table 3-1, subject to permissible variations as specified in
ASTM A788. Product analysis of nitrogen, hydrogen and oxygen is not required.
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Table 3-1 Chemical composition limits in weight %
Element
1)
Sulphur (S)
Phosphorus (P)
Aluminium (Al)
2)
Calcium (Ca)
SFC 1
SFC 2
SFC 3
0.010 max.
0.010 max.
0.005 max.
0.015 max.
0.015 max.
0.010 max.
0.055 max.
0.055 max.
0.055 max.
-
-
0.005 max.
Vanadium (V)
3)4)
0.06 max.
0.06 max.
0.03 max.
Niobium (Nb)
3)4)
0.02 max.
0.02 max.
0.02 max.
Titanium (Ti)
0.025 max.
0.025 max.
0.025 max.
Tin (Sn)
0.02 max.
0.02 max.
0.015 max.
Antimony (Sb)
0.03 max.
0.03 max.
0.02 max.
Arsenic (As)
0.03 max.
0.03 max.
0.02 max.
Lead (Pb)
0.010 max.
0.010 max.
0.010 max.
Bismuth (Bi)
0.010 max.
0.010 max.
0.010 max.
0.0010 max.
0.0010 max.
0.0005 max.
0.012 max.
0.012 max.
0.012 max.
Hydrogen (H)
2 ppm max.
2 ppm max.
2 ppm max.
Oxygen (O)
25 ppm max.
25 ppm max.
25 ppm max.
0.48 max.
0.48 max.
0.48 max.
Boron (B)
5)
Nitrogen (N)
CE (IIW)
4)
6)7)
1)
Limits for elements such as carbon, manganese, silicon, chromium, nickel and molybdenum shall be as specified in
the MPS.
2)
Min. 0.020% Al (total content) unless other nitrogen binding elements are used, e.g. Nb, V or Ti.
3)
Limit applies to forgings subjected to subsequent welding and PWHT.
4)
Not applicable for ASTM A707 L3.
5)
Boron shall not be intentionally added.
6)
CE (IIW) = C + Mn/6 + (Cu + Ni)/15 + (Cr + Mo + V)/5
7)
Limit applies to CS forgings, typically ASTM A694 F60 and F65, subjected to welding without PWHT. Steels with CE
> 0.45 shall have supporting weldability data for the thickness and composition under consideration demonstrating
compliance with relevant hardness requirements.
3.3 Mechanical testing
3.3.1 Test laboratories
Test laboratories shall have a QMS conforming to ISO 17025 or equivalent. If the laboratory is not certified
according to ISO 17025, the QMS shall be approved by the purchaser.
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3.3.2 Test material
3.3.2.1 Tensile and impact properties are required at the critical section(s). For this reason, test material
for mechanical testing shall have a thickness representative of the critical section(s) of the part. The critical
section(s) shall be determined by the equipment manufacturer in the product design and communicated to
the forging manufacturer.
3.3.2.2 Test material for all classes shall be a prolongation, as defined in API 20B, or a sacrificial production
part. Test material shall represent each heat, re-melt ingot (if applicable) and heat-treat lot.
3.3.2.3 Forging manufacturers shall take into account that extra test material is needed for SPWHT. Forging
manufacturers shall also take into account the possibility of re-testing in establishing the minimum amount of
test material required.
3.3.2.4 Test material shall be marked for identification.
3.3.3 Test sampling
3.3.3.1 For SFC 1, one tensile and one set of three CVN specimens shall be taken for each position and
orientation, as given in the applicable industry code.
For SFC 2 and SFC 3, one tensile and one set of three CVN specimens shall be taken for each position and
orientation, as given in Table 3-2.
Table 3-2 Position and orientation of specimens for production testing of SFC 2 and SFC 3
Thickness,T
1)
Test specimen position
2) 3)
Orientation
4) 5)
≤ 100 mm (4 in.)
½T
Longitudinal and transverse
> 100 mm (4 in.)
¼ T and ½ T
Longitudinal and transverse
1)
Thickness (T) is the thickness of the test material, i.e. critical section, at the time of heat treatment.
2)
Position ½ T is at the centre (solid forging) or mid-wall (hollow forging) thickness. Position ¼ T is one quarter
thickness below heat treated surface.
3)
4)
Sampling of solid forgings when centre will be subsequently removed shall be at IDfinish instead of the ½ T position.
Test specimen orientations shall be as defined in ASTM A370. Specimens shall be taken in both directions, if
geometry permits.
5)
For circular forgings such as rings and discs, longitudinal and tangential tests shall be used.
3.3.3.2 Test specimens shall be positioned such that the tensile specimen middle gauge length and CVN root
are as follows:
a)
b)
for hollow forgings, T from any second surface
for solid forgings, ½ T from any second surface.
3.3.4 Test methods
3.3.4.1 Tensile and CVN testing shall be performed according to the applicable standards given in ASTM
A370.
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Page 16
3.3.4.2 Brinell or Rockwell hardness testing shall be performed according to the applicable standards given
in ASTM A370 using a stationary machine. If stationary testing is impracticable, then portable hardness
testing in accordance with ASTM E110 may be used.
3.3.5 Mechanical properties
3.3.5.1 Tensile properties shall comply with the requirements specified in Table 3-3.
Table 3-3 Tensile property requirements in longitudinal and transverse direction
Tensile property
Requirement
Elongation in 50 mm (2 in), min., %
17
Reduction in area, min., %
35
Yield strength to tensile strength ratio (actual values), max.
0.90
Actual yield strength, max., MPa (ksi)
950 (138)
1)
1)
For compliance with requirements in API 17G, the minimum elongation in longitudinal direction shall be 18%.
3.3.5.2 CVN test temperature shall be at minimum design temperature (MDT), as specified by the purchaser.
CVN absorbed energy shall comply with the requirements in Table 3-4.
Guidance note:
The MDT/CVN test temperature should correspond to one of the temperature classes specified in API 6A, e.g. U (-18°C/0°F), P
(-29°C/-20°F), or L (-46°C/-50°F). The MDT should be agreed between the purchaser and end user.
---e-n-d---o-f---g-u-i-d-a-n-c-e---n-o-t-e---
Table 3-4 Minimum CVN absorbed energy in longitudinal and transverse direction
Specified minimum yield strength (SMYS)
SFC 1
Average
SFC 2 and SFC 3
Single
Average
50 J
(37 ft-lb)
Up to 517 MPa (75 ksi)
Over 517 MPa (75 ksi)
Up to 586 MPa (85 ksi)
40 J
(30 ft-lb)
1)
Over 586 MPa (85 ksi)
Up to 655 MPa (95 ksi)
30 J
(22 ft-lb)
1)
Single
1)
38 J
(28 ft-lb)
1)
60 J
(44 ft-lb)
45 J
(33 ft-lb)
70 J
(52 ft-lb)
53 J
(39 ft-lb)
1)
For compliance with requirements in API 17G, the minimum absorbed energy in longitudinal direction shall be 60 J
(44 ft-lb) average and 45J (33 ft-lb) single.
3.3.6.1 Both the test material surface and the forged or the rough machined surface of each production
forging shall be hardness tested after quality heat treatment. The test locations and acceptance criteria
(minimum and maximum hardness) shall be as stated in the MPS.
3.3.6.2 Maximum hardness shall be in accordance with ISO 15156-2 or NACE MR0175 where components
are intended for sour service.
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3.3.6 Hardness testing
3.3.6.3 For any component that can be exposed to cathodic protection, the hardness shall not exceed 35
HRC, 328 HBW or 350 HV 10.
3.3.7 Re-testing
3.3.7.1 If the results from tensile testing do not meet the specified requirements, two additional tensile tests
may be made from the same test material. If both of these additional tests meet the requirements, the parts
represented shall be accepted.
1)
2)
3)
The average value of six specimens shall meet the specified minimum average value
Not more than two of six individual values shall be lower than the specified minimum average value
Not more than one of six individual values shall be lower than the specified minimum single value.
3.3.7.3 If the results from hardness testing do not meet the specified requirements, two additional readings
may be taken in close proximity to the failed reading. If the average of the three readings meets the
requirement and, in the case of parts for sour service, no individual reading is greater than 2 HRC above the
specified value, the part shall be accepted.
3.3.7.4 If re-testing fails, the forgings represented may be subjected to re-heat treatment and then
submitted to testing in accordance with [3.3]. In such cases, the forgings may be subjected to one additional
full heat treatment cycle and may not be re-tempered more than twice. All the tests previously performed
shall be repeated after re-heat treatment and the results shall meet the specified requirements.
3.3.8 Testing after simulated post weld heat treatment
3.3.8.1 Where a forging is subjected to subsequent welding and PWHT, as specified by the purchaser,
sufficient material shall be removed from the test material and subjected to a SPWHT.
The time and temperature shall be the same as those used during MPQ or as specified by the purchaser. Total
time at temperature shall consider inclusion of multiple heat treat cycles to accommodate weld repair.
3.3.8.2 Following the SPWHT, the material shall be tensile, CVN and surface hardness tested and shall meet
the requirements of the applicable code and this RP.
3.4 Metallographic examination
The prior austenite grain size for all classes shall be determined for each heat according to ISO 643 or ASTM
E112. The prior austenite grain size shall be 5 or finer. Sampling position shall be ½ T for T ≤ 100 mm (4 in)
and ¼ T for T > 100 mm (4 in).
Steel cleanliness for SFC 3 shall be determined for each heat according to ASTM E45, method A (Modified
JK). Sampling position shall be ½ T for T ≤ 100 mm (4 in) and ¼ T for T > 100 mm (4 in) . Inclusion rating
limits shall meet the requirements in Table 3-5. If any oversize inclusions are present, they shall be recorded
separately as per ASTM E45.
Table 3-5 Modified JK inclusion rating limits for SFC 3
Type
A
B
C
D
Thin
1
1
1
1½
Thick
½
½
½
1
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3.3.7.2 If the results from CVN testing do not meet the specified requirements, one additional set consisting
of three specimens from the same test material may be tested. In order to accept the parts represented,
after testing the additional set, the following conditions shall be satisfied simultaneously:
3.5 Non-destructive testing
3.5.1 General
3.5.1.1 Companies performing magnetic particle testing (MT) and ultrasonic testing (UT) activities shall
comply with ISO 17020 or its equivalent within non-destructive testing (NDT). Companies shall meet the
requirements for Type A or Type B inspection bodies, as applicable.
3.5.1.2 Personnel responsible for MT and UT activities, including approval of procedures, shall be qualified
and certified to Level 3 in accordance with ISO 9712, ASNT Central Certification Program (ACCP) or
equivalent third party certification system in the method(s) concerned.
3.5.1.3 Personnel performing MT and UT and interpretation of test results shall be qualified and certified
to minimum Level 2 in accordance with ISO 9712, ASNT Central Certification Program (ACCP) or equivalent
third party certification system in the method(s) concerned.
3.5.1.4 Personnel performing visual testing (VT) shall comply with vision requirements in accordance with
the manufacturer's documented procedures that meet the applicable requirements of ISO 9712.
3.5.2 Visual testing
3.5.2.1 All forgings shall be visually tested on all accessible surfaces in the final condition to be supplied to
the purchaser. The light intensity at the examination surface shall be minimum 1000 lx. Forgings supplied in
the black condition shall be de-scaled prior to VT.
3.5.2.2 Forgings shall be free from cracks, seams, laps, folds, pipe, segregation, underfills, scale or other
imperfections, which due to their nature, degree or extent will interfere with the use of the forgings in the
machining and fabrication of parts.
3.5.3 Magnetic particle testing
3.5.3.1 All forgings shall be subjected to magnetic particle testing (MT) on the accessible surfaces in the final
machined condition.
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3.5.3.2 Where forgings are supplied in the black or rough machined condition, they shall be capable
of meeting the MT requirements for parts in the final machined condition. This shall only apply to
defects related to forging manufacturers’ activities, e.g. materials, forging and heat treatment. Forging
manufacturers shall perform intermediate MT taking this into consideration. In such cases, the extent of
testing and acceptance criteria shall be agreed with the purchaser.
3.5.3.3 MT in final machined condition shall be performed using continuous wet fluorescent technique in
accordance with ASME BPVC V Article 7 and ASTM E709 with the following exceptions: Prods, permanent
magnets and DC magnets are not permitted. Copper electrodes or contact plates are not permitted.
3.5.3.4 If access limits the possibility for MT at a bore, UT shall be performed as given in [3.5.4.7].
3.5.3.5 MT acceptance criteria for SFC 1 and SFC 2 parts in the final machined condition shall be:
a)
b)
c)
no relevant linear indication
no relevant rounded indication with a major dimension equal to or greater than 3 mm (1/8 in)
2
2
no more than ten relevant indications in any continuous 40 cm (6 in ) area
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d)
e)
four or more relevant indications in a line separated by less than 1.6 mm (
unacceptable
no relevant indications in pressure contact sealing surfaces.
in) (edge to edge) are
Relevant indication shall be as defined in ISO 10423 or API 6A.
3.5.3.6 MT acceptance criteria for SFC 3 parts in the final machined condition shall be no relevant indication,
as defined in ISO 10423 or API 6A.
3.5.4 Ultrasonic testing
3.5.4.1 All forgings shall be subjected to ultrasonic testing (UT) covering the entire volume. UT shall be
performed in accordance with ASME BPVC V Article 5 and ASTM A388. The instrument sensitivity shall be
based on distance amplitude correction (DAC) curve . Alternatively, the distance gain-size (DGS) method
may be used. The DGS method, if used, shall be verified on minimum two known reflectors of relevant size in
a reference block of the same nominal chemical composition, heat treatment, surface finish and thickness as
the forging(s) to be tested. The verification shall be documented.
3.5.4.2 Scanning shall be performed from all accessible surfaces and at least from two perpendicular
directions. Forgings which cannot be examined axially using the straight-beam technique shall be scanned
with the angle-beam technique in both axial directions.
3.5.4.3 Where the configuration of the forging limits complete coverage using straight beam probe,
additional scanning with angle beam probe shall be performed. Alternatively, the machining of the part
shall be such that areas where adequate ultrasonic testing is not possible will be removed during the final
machining.
3.5.4.4 SFC 1: Scanning shall be in accordance with ASTM A388. Sensitivity setting for straight beam probes
shall be in accordance with ISO 10423 or API 6A PSL 3. Sensitivity setting for angle beam probes shall be
in accordance with ASTM A388 for cylindrical and hollow forgings. Acceptance criteria for straight beam and
angle beam probe shall be in accordance with ISO 10423 or API 6A PSL 3.
3.5.4.5 SFC 2: As for SFC 1, with the addition that reference reflector sizes refer to wall thickness after final
machining and not the actual thickness at time of examination.
3.5.4.6 SFC 3: As for SFC 2 with the addition that circumferential angle beam scanning, clockwise and
counter-clockwise, shall be performed regardless of OD/ID ratio. If ID notch is not accessible, side drilled
holes (SDH) may be used as reference reflector.
3.5.4.7 If access limits the possibility for MT at a bore, UT shall be performed on solid forgings before drilling
of the bore, or before final machining of the bore. In such cases, the UT shall be based on a reflector size of
flat bottom hole (FBH) Ø1.6 mm. No indications exceeding the reference are accepted in the location of final
machined surface. The testing shall be defined in the scan plan and shall be unambiguously reported.
3.6 Dimensional inspection
All forgings shall be inspected for dimensions and shall be according to drawings supplied by the purchaser.
3.7 Repair
Surface defects may be removed by grinding or machining provided dimensional tolerances are maintained.
The resulting grooves shall have a bottom radius of approximately three times the depth and shall be
blended into the surrounding surface to avoid any sharp contours. Complete elimination of the defective
material shall be verified by suitable NDT.
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Repair by welding on forgings shall not be permitted.
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SECTION 4 MANUFACTURING PROCEDURE QUALIFICATION
4.1 General
Manufacturing procedure qualification (MPQ) is not required for SFC 1.
For SFC 2 and SFC 3, the manufacturing processes, methods, and procedures shall be qualified by testing of
a representative forging in order to:
— demonstrate that the manufacturing results in products meeting specified requirements
— verify that the mechanical properties of the prolongation represent the critical cross section of the
production part, as agreed between the purchaser and the manufacturer
— demonstrate the properties in the thickest cross section of the production part.
The qualification forging shall be representative in geometry and mass of production forgings and shall be
produced in accordance with the MPS as specified in [2.2]. Regular production equipment shall be used for
qualification and heat treatment furnaces used shall have maximum load.
Where stacking is allowed and intended used in production, see [3.1.4.2], the qualification forging shall be
from the middle of the stack.
The qualification forging shall have an integral prolongation if prolongation testing is used in production.
Where a prolongation is used, it shall have the same or smaller forging reduction ratio and the same thermal
history as the critical section of the part.
Qualification forgings failing to meet the acceptance criteria specified in [4.2] shall be cause for re-evaluation
of the processes and procedures used. A revision of the MPS and re-qualification is required.
4.2 Qualification testing
The qualification forging shall be subjected to testing on both the prolongation, if used, and the sacrificial
part itself. Detailed requirements are given in [4.2.1] to [4.2.8]. Where production testing will be performed
on a sacrificial part only, any reference to qualification testing on the prolongation shall be understood to
mean qualification testing on the critical section of the sacrificial part.
All test results shall be documented.
4.2.1 Chemical composition
The chemical composition shall be determined as heat and product analysis for both SFC 2 and SFC 3. Test
methods and acceptance criteria shall be as given in [3.2.1].
4.2.2 Tensile and Charpy V-notch testing
4.2.2.1 Test specimens shall be taken in both longitudinal and transverse direction, if geometry permits. For
circular forgings such as rings and discs, longitudinal and tangential tests shall be used.
4.2.2.2 Test specimen positions shall be as given in Table 4-1. The distance from any second surface shall be
as given in [3.3.3]. Test methods, Charpy V-notch (CVN) test temperature and acceptance criteria shall be as
given in [3.3].
4.2.2.3 In the event that acceptance criteria are not met at ½ T position for the thickest section, engineering
analysis may be performed to determine if properties are fit for use.
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Table 4-1 Position of tensile and CVN specimens for qualification testing
Prolongation (if used)
and sacrificial part, critical section
1) 4)
T ≤ 100 mm (4 in): ½ T
T > 100 mm (4 in): ¼ T, ½ T and ¾ T
1)
2)
3)
4)
Sacrificial part, thickest section
2) 3) 4)
Near outer surface but not deeper than 31.75 mm (1¼ in),
At ¼ Tth, ½ Tth and ¾ Tth,
Near inner or opposite surface but not deeper than 31.75 mm (1¼ in)
Thickness (T) is the thickness of the critical section at the time of heat treatment.
Thickness (Tth) is the thickness of the thickest section at the time of heat treatment.
Testing near outer and inner surfaces is not required for Tth ≤ 100 mm.
Sampling of solid forgings when centre will be subsequently removed shall be at IDfinish instead of the ½ T and ½
Tth positions.
4.2.3 Hardness testing
4.2.3.1 Testing on surface
Hardness testing shall be performed on the surfaces of the prolongation and the thickest section of the
sacrificial part as follows:
— For round cross sections, at least three indentations evenly distributed along the circumference
— For square and rectangle cross sections, at least two indentations on each side.
Forgings having a heat treated length (exclusive of prolongation) exceeding 5 m shall be tested at each end.
Test methods and acceptance criteria shall be as given in [3.3.6].
4.2.3.2 Testing through cross section
Hardness testing using stationary equipment shall be performed through the cross sections of the
prolongation (if used) and the thickest section of the sacrificial part. Each cross section shall be tested along
two perpendicular traverses (solid sections) or two traverses 180° apart (hollow sections). At least five
indentations shall be made along each traverse at the following positions:
a)
b)
c)
d)
near the outer surface but not deeper than 31.75 mm (1¼ in)
at ¼ T, ½ T, and ¾ T (prolongation)
at ¼ Tth, ½ Tth, and ¾ Tth (thickest section)
near the inner or opposite surface but not deeper than 31.75 mm (1¼ in).
Test methods and acceptance criteria shall be as given in [3.3.6]. In the event that acceptance criteria are
not met at ½ Tth position for the thickest section, engineering analysis may be performed to determine if
properties are fit for use.
4.2.4 Testing after simulated post weld heat treatment
Tensile, CVN and surface hardness testing shall be performed after SPWHT as given in [3.3.8], if applicable.
4.2.5 Metallographic examination
4.2.5.1 Prior austenite grain size
The prior austenite grain size shall be determined on the prolongation and the thickest section of the
sacrificial part. Sampling position shall be as given in Table 4-2. Test method and acceptance criteria shall be
as given in [3.4].
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A photo-micrograph illustrating the typical appearance of the grain structure shall be provided at a
magnification of 100X or higher.
4.2.5.2 Steel cleanliness
Steel cleanliness shall be determined on the prolongation and the thickest section of the sacrificial part.
Sampling position shall be as given in Table 4-2. Test method shall be as given in [3.4]. Acceptance criteria
shall be as given in [3.4] for SFC 3 and in API 20B for SFC 2.
Table 4-2 Position of metallographic examination for qualification testing
1)
Type of test
Prolongation
Prior austenite grain size
T ≤ 100 mm (4 in): ½ T
T > 100 mm (4 in): ¼ T
¼ Tth
Steel cleanliness
T ≤ 100 mm (4 in): Close to surface and ½ T
T > 100 mm (4 in): Close to surface and ¼ T
Close to surface and ¼ Tth
1)
2)
Sacrificial part, thickest section
2)
Thickness (T) is the thickness of the critical section at the time of heat treatment.
Thickness (Tth) is the thickness of the thickest section at the time of heat treatment.
4.2.5.3 Wrought structure
One full-section sample from the prolongation and one full-section sample from the thickest section shall be
taken and macro-etched according to ASTM A604 or ASTM E381.
The samples shall show a wrought structure, as defined in API 20B, throughout the section. No injurious
segregation or porosity shall be permissible. Acceptance criteria shall be S1R1C1 as per ASTM E381, see
ASTM Adjuncts: Photographs for Rating Macroetched Steel (3 plates). Photo-macrographs shall be taken.
4.2.6 Fracture toughness testing
4.2.6.1 CTOD fracture toughness testing is required for SFC 3. Testing shall be performed according to ASTM
E1820 or ISO 12135.
4.2.6.2 Unless otherwise agreed with or required by the purchaser, at least three single-edge bend
specimens of width 25 mm (1 in) shall be tested. Specimens shall be sampled from the sacrificial part at
the critical section, as specified by the purchaser. Crack plane orientation shall be L-R (round section) or L-T
(square/rectangular section).
Guidance note:
The number, type, size and location of test specimens should also be agreed between the purchaser and the end user.
---e-n-d---o-f---g-u-i-d-a-n-c-e---n-o-t-e---
4.2.6.3 Test temperature and acceptance criteria shall be as given in Table 4-3.
Table 4-3 CTOD requirements at the critical section
1)
Specified minimum yield strength (SMYS)
Test temperature
CTOD
Up to 517 MPa (75 ksi)
MDT
0.25 mm
Over 517 MPa (75 ksi)
Up to 586 MPa (85 ksi)
MDT
0.30 mm
Over 586 MPa (85 ksi)
Up to 655 MPa (95 ksi)
MDT
0.35 mm
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Steel forgings for subsea applications
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Specified minimum yield strength (SMYS)
1)
Test temperature
CTOD
1)
Values are applicable for final machined critical section thickness up to 100 mm (4 in).
4.2.7 Non-destructive testing
The qualification forging shall be non-destructive tested (NDT) as given in [3.5].
4.2.8 Dimensional inspection
The qualification forging shall be inspected for dimensions as given in [3.6].
4.3 Validity
For the MPQ to remain valid, all production shall be within the limits of essential variables defined in Table
4-4. Any change outside the limits of essential variables shall lead to re-qualification.
Table 4-4 Validity of MPQ, limits of changes to essential variables
Essential variable
Change requiring requalification
SFC 2
SFC 3
X
X
a)
Change outside specified limits for chemical composition
b)
Increase in specified mechanical properties
2) Chemical composition
a)
Reduction in CE (IIW) value for CS and LAS below 0.03 of
qualified CE value (based on heat analysis)
X
X
3) Melting, refining and
casting
a)
Change of methods and practices for primary melting, secondary
refining and casting
X
X
a)
Change from open die to closed die forging or vice versa
b)
Change from open die to ring rolling or vice versa
X
X
c)
Change from press forging to hammer forging
5) Forging capacity
a)
Reduction in forging capacity (forging press tonnage)
X
X
6) Forging reduction ratio
a)
Reduction in overall forging reduction ratio
X
X
a)
Change of quality heat treatment parameters outside specified
limits, e.g. temperature and minimum soaking time
b)
Increase in maximum transfer time, if more than 90 seconds
c)
Change of furnace type
d)
Increase in furnace size
X
X
e)
Change of quenching medium
f)
Reduction in stacking distance (stacking not permitted for SFC 3)
g)
Use of a subcontractor for quality heat treatment or change in
subcontractor used
a)
Increase in thickness of the critical section
b)
Increase in thickness of the thickest section
X
X
1) Steel grade
4) Forging method
7) Heat treatment
8) Thickness
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Steel forgings for subsea applications
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Essential variable
Change requiring requalification
9) Manufacturer of starting
material
a)
Change of manufacturer
a)
Change of ingot type
b)
Change of methods and practices for ingot discard
a)
Increase in weight of a single forging above 10% for forgings over
2300 kg and above 25% for forgings under 2300 kg
10) Ingot/bloom
11) Forging weight, as heat
treated
Recommended practice — DNVGL-RP-0034. Edition September 2019
SFC 3
-
X
-
X
-
X
Page 26
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SFC 2
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Changes – historic
CHANGES – HISTORIC
There are currently no historical changes for this document.
Recommended practice — DNVGL-RP-0034. Edition September 2019
Steel forgings for subsea applications
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Page 27
About DNV GL
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