Improving Plate Yield by Reduction of Steel Defects
ABSTRACT
In today’s competitive business environment delivery of prime product to customer at desired time and
competitive cost is the key to success for all the steel makers. With the growth of economy the demand
for special steel plates with stringent ultrasonic requirement is increasing.
Defective generation in plates was a concern for Bhilai Steel Plant and was affecting timely delivery of
plates to customers. Steel defects in plates in the year 2012-13 were as high as 2.74 %.
To overcome this difficulty a root cause analysis was done and the reason for high NDT failures in heavy
plates was found to be Hydrogen induced cracking and Production of plates by a process route
which was strictly as per steel order and not as per technology required for achieving such high
levels of UT (ASTM578 level B and S2 E3).
After identification of the root causes, strategy was formulated which involved.
1. Defining a process route for making plates of different grades and thickness.
2. Monitoring efficiency of different stations in the process route and shutdown planned as per
quality feedback.
3. Adopting Dynamic process control measures for taking care of process deviations
With the implementation of these measures from Dec ‘2012 significant improvement in plate quality was
achieved and Steel defects in plates reduced from yearly average of 2.74 % to 0.71 % in Feb ‘2013.
Effectiveness of the strategy was confirmed by continuous reduction of steel defects to below 1 % level
in 2013-14.
The above measures helped BSP in on time delivery of plates, reduced cost of poor quality by 3.00
Crores/month and helped in developing capability to deliver plate with S2E3 level of UT thereby opening
a new market segment.
Introduction: In the present era of stiff competition, production of quality products at competitive prices
becomes essential. For meeting this objective, it is imperative to reduce product defect with little impact
on productivity. Various technological innovations in machine design and process optimisation in
continuous casting enabled to produce quality products.
Minimisation of Cracks in continuously cast product plays an important role for improving product yield
and quality. Cracks are initiated due to formation of low ductility zones in steel at high temperature, while
solidification. The causes of low ductility and the measures to enhance the ductility of steel is of prime
concern in optimising steel making and casting parameters for reducing product defects.
Following are same of the Steel Defects observed in Plates in BSP:




Non Metallic inclusions (NMI)
Longitudinal Crack
Spider Crack
UT Failure (NDT)
Internal (across BSP-SMS-2 and PM) Norms for Defects are :


Defective due to steel defects : 1.40% max.
Defective due to mill defects : 0.43% max.
Impact of High Steel Defect is as follows :



Delay in order servicing.
Chocking of Plate Mill finishing area.
Loss of market.
Hence a challenge was undertaken to evolve a system which aligns process capability with customer
needs.
Analysis of Steel Defect April 2012 – November 2012 :
65.53
70
60
50
40
30
20
10
5.88
3.01
2.83
1.46
1.27
0
NMI
LCRK
SPCRK
NDT
PORO
SLSD
Analysis of steel defects components:
Year wise analysis of Steel Defect:
2.76
3
2.23
2.5
2
2.16
1.73
1.5
1
0.5
0
2009-10
2010-11
2011-12
2012-13
Year wise analysis of Steel Defect:
55.47
60
50
Defective
40
30
16.45
20
10
3.83
6.96
3.47
0.67
0
NMI
LCRK
SPCRK
NDT
PORO
SLSD
Root cause analysis of UT failure was done and :
Major reasons identified are –



Hydrogen cracking.
Caster condition.
Process route – Not aligned with customer need.
Action plan for reducing NDT failures was formulated as given below:

Defining of process route for different grades/thickness –
A. Technological Process RouteConverter  LF  RH  Caster  Plate Mill  NDT
This process route is to be followed for –
1. For all high tensile (with or without Cu) below 410 MPa YS, steel plates of 32mm and
above thickness.
2. For 2062 E410 and above grades this route shall be followed for plate thickness 28 mm
and above.
3. Calcium treatment in LF for all high tensile, micro alloyed heats and EME grades.
4. All mild heats for plates of 32mm and above thickness.
5. All BQ heats irrespective of plate thickness.
Action Plan:

Improving Efficiency of Different Stations in Process Route1. Ensuring vacuum level of <3 mbar in 2 to 2.5 minutes and achieving vacuum level of <1
mbar in 3.5 to 4 minutes.
2. Measurement of RH out hydrogen at least once in a day. Aimed hydrogen less than
1.5ppm in tundish.
3. RH off take change/maintenance planned after 1500 heats.
Improving Efficiency of Different Stations in Process Route:

Caster Maintenance1. Timely segment changes at caster 6 based on logger readings and feed back on UT
results.
2. Increased frequency of manual inspection of Caster 3.
3. Tightening of foundation bolts of caster by hydraulic torque wrench up to 400 Kg/cm2.
Process Control:

Initiatives taken under this are1. Minimum 15’ degassing of 1st heat of sequence/tundish and ensuring a hydrogen level of
less than 1.6 ppm.
2. First heat of tundish/sequence planned only for thinner plates and not for heavy plate.
3. Use of MES for effective monitoring of quality feedback and based on this feed back
caster maintenance plan made.
4. Diverting heat with less degassing to lower thickness.
5. Leaner chemistry for lower segregation.
6. Inclusion rating on regular basis Aim below 1.0 for EME grades.
7. Periodical sulphur printing of slabs for monitoring caster condition.
Benefits:



Timely servicing of orders.
Increase in customer confidence.
Capability to service S2E3 (NDT) plate orders developed.
Reduced Cost:
5
4.67
4.5
4
3.5
3
2.5
2
1.5
0.51
1
0.5
0
Befor
After
Results of Improvement Initiatives M/C # 6 Performance:
Insp.
NDT
Period
%
16599
635
Before
3.8
149917
150685
13832
39
After
0.28
150686
Till 24th
3.8
4
3.5
3
2.5
2
1.5
1
0.28
0.5
0
Before
After
Heat Number
Results of Improvement Initiatives M/C # 3 Performance:
Insp.
NDT
Period
%
Heat Number
12851
428
Before
3.3
149917
150685
7649
63
After
0.8
150686
Till 24th
3.3
3.5
3
2.5
2
1.5
0.8
1
0.5
0
Before
After
Month
Oct-12
Nov-12
Dec-12
Jan-13
Feb-13
Mar-13
Defective (Ton)
3184
2068
1125
1033
933
1419
Opportunity Loss (Cr)
4.67
2.76
1.21
1.14
0.86
1.27
352.52
304.46
327.39
333.67
313.99
333.06
1.33
0.91
0.37
0.34
0.27
0.38
Total Sales (Cr)
Opp. Loss/Sales (%)
1.4
1.33
1.2
0.91
1
0.8
0.6
0.37
0.4
0.34
0.38
0.27
0.2
0
Oct-12
Nov-12
Dec-12
Jan-13
Feb-13
Mar-13
Customer Feed Back:

TATA HITACHI –
Subject : FW : feedback from Tata Hitachi (TELCON) Feed back fro customer is sent please Balu
From : Ajay Kumar [mailto: ajaykumar@tatahitachi.co.in] Sent: 03 April 201314:02 to : KL
Balasubramaniam Cc: Prabhat; Manoj Barik; Malay Palit
Subject : feedback
Dear Sir,
The quality of plates have been improved in all parameters. We continue to look forward
to similar support in the future also.
Regards
Ajay Kumar
Divisional Manager (Supply Chain Management)
Tata Hitachi Construction Machinery Co.Ltd.
Tata Motors premises, Telco Jamshedpur – 831010 INDIA.

RSB Transmission Jamshedpur –
Sent: Tuesday,26 February 2013,17:34 Subject: Feed Back on quality from M/s RSB.
Dear Sir(s)
Submitted herewith the feedback on quality form M/s RSB Transmission please Balu KL
Balasubramaniam DGM (Quality) Bhilai Steel Plant Mo. 9407981698, Dear Sir please find the
details of Heat no. which we receive after heat no. 150686 we find no complain on these heat
nos.
Regards
Manzar Alam
Sr.Manager (Material)
RSB Transmission (I) Ltd Unit (II) Jamshedpur (India)
Email: manzar.alam@rsbglobal.com Mo. 09334628226
HIGHLIGHTS OF 2013-14
Lowest ever steel defects of 0.60% in
Jan’2014
Overall steel defect till Jan. 1.01%