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Quarterly Publication Rs. 20
OCTOBER 2019 Weld 18 Bead 3
Page 2 of 33
AROUND IWS
Know Your President
17th AGM
68th NGC - Images
KNOWLEDGE SHARING
RAW 2019 by IWS Hyderabad Centre
@ MCET Student Forum
Workshop on “Recent
Developments in Welding
Technology” by KSRCT Student
Forum
Seminar on "Advancement of
Welding in Boilers Industries" @
RIT Student Forum
Hands on Training & Workshop on
“Modern Surface Coating
Technology” @ RIT Student Forum
TECHNICAL PAPERS
Effect of ATIG Welding Process
Parameters on the Mechanical and
Microstructure Properties of Super
Duplex Stainless Steel
Microstructural Characteristics of
Shielded Metal Arc Welded
Dissimilar Joints of Armour Steels
THE JOURNAL OF
Regn. No. 41817 / 2002
QUARTERLY PUBLICATION
OCT 2019 Weld: 18 Bead: 3
PRESIDENT
SHRI R PADMANABHAN
Immediate Past President
SHRI S BISWAS
Vice Presidents
SHRI HIMANSHU I GANDHI SHRI S PRABAKARAN
Dr S ARAVINDAN
Hon. Secretary
SHRI N RAJASEKARAN
Hon. Treasurer
Mrs. A SANTHAKUMARI
Members
Dr K Asokkumar Dr A Chandrasekhar
Shri A Maruthamuthu Dr. T Senthil Kumar
Shri G Rajendran Shri V Ganesh Sinkar
Shri M P Jain Dr Shashikantha Karinka
Shi M Kasinathan Shri Gyan Prakash Bajpai
Shri R Easwaran Dr G Padmanabham
Shri S M Agarwal Shri Muneesh Narain
Shri S M Bhat Dr T Prakash
Shri Amit Agarwal Dr S Shanavas
Dr V Balasubramanian Shri Naresh Malli Reddy
Shri T Baskaran Dr Yadaiah Nirsanametla
Dr N Murugan Shri A K Verma
Dr N Raju Dr P Sivaprakash
Editor in Charge Shri S. CHANDRASEKARAN – Editor in Charge
ASSOCIATE EDITORS Shri Praveen Kumar Lakavat Shri R. Arivalagan
CO-ORDINATORS Dr. N Raju Shri A K Verma
PUBLISHED BY
On Behalf of IWS by
Shri N RAJASEKARAN Hon. Secretary (IWS)
INDIAN WELDING SOCIETY INSTITUTIONS BUILDING, KAILASAPURAM, TIRUCHIRAPPALLI – 620 014
INDIA Websites: www.iws.org.in www.iwsevents.com E mail: [email protected] [email protected]
Page 3 of 33
Shri R PADMANABHAN
PRESIDENT (IWS)
Mr. R Padmanabhan, 58, is Executive Director of the BHEL Tiruchirappalli Complex comprising of High Pressure
Boiler Plant (HPBP) and Seamless steel Tube Plant (SSTP) at Tiruchirappalli, Power Plant piping Unit (PPPU) at
Thirumayam, Piping Centre (PC) at Chennai and Industrial Valves Plant (IVP) at Goindwal in the Punjab. A
Mechanical Engineering graduate of the batch of 1983, from the reputed Alagappa Chettiar Government College
of Engineering and Technology, Karaikudi in Tamil Nadu.
Mr. R Padmanabhan is an engineering professional with over 35 years’ experience in Commercial, Project
Management, Operations, Defence and Aerospace Business, Business Development, Quality & Business
Excellence, Outsourcing and Advanced Technology Products for the Power and Industries verticals of the
company.
Mr. R Padmanabhan joined BHEL Tiruchirappalli as an Engineer Trainee in 1983 and after initial training, was
posted to the Fossil boilers (Commercial) group where he developed his exceptional projects management skills
and set new standards for customer relations, earning a reputation for ensuring customer satisfaction at all costs,
an attribute for which he has been well-known throughout his career. He gained specialized expertise in the
development of cutting-edge technology and products when he subsequently moved to the nuclear products
group dedicated to the manufacture and supply of sophisticated products for Defence and Nuclear Power Plants
applications. Later, He was put in charge of the Business Development Group entrusted with diversification and
entry into new Products markets.
On his elevation to the post of General Manager in 2013, Mr. Padmanabhan was posted to the Project
Management Group at BHEL’s Industry Sector at New Delhi and was subsequently entrusted with the sensitive
Defence Business Portfolio in BHEL’s industry Sector. In 2017, he returned to BHEL Tiruchirappalli to head the
Business Development Group and was then put in charge of the production of Advanced Technology Products
where he was responsible for streaming complex operations and achieving cycle time reduction on an
unprecedented scale.
He later headed the Outsourcing department before his transfer back to BHEL’s Corporate Office at New Delhi in
December 2018 on elevation as GM-in-charge and head of the Corporate Quality and Business Excellence group.
He took charge as head of the BHEL Tiruchirappalli complex in on March 23, 2019. Mr. Padmanabhan is widely
travelled, having visited several countries including the USA, Israel and the Ukraine.
Page 4 of 33
17th ANNUAL GENERAL
MEETING
The 17th Annual General Meeting of the Society was conducted at the Institutions Building, BHEL
Township, Kailasapuram, Tiruchirappalli – 620 014 on 23rd September 2019 evening. 51 members
attended the AGM.
Since Mr. Subrata Biswas, President (IWS) could not attend the
AGM, Mr. A. Maruthamuthu, Vice President presided over the
AGM and conducted the business session.
Mr. S Singaravelu, Vice Chairman (IWS, SZ) welcomed the Patron
& Executive Director of BHEL, NGC members and members from
various parts of the country for the AGM.
Mr. N Rajasekaran, Hon. Secretary read out the MOM of the 16th AGM and requested the AGM to adopt
the same. Mr. G. Uma Shanker proposed and Mr. R Easwaran seconded the proposal. The AGM
unanimously adopted the MOM.
Mr. N Rajasekaran, Hon. Secretary presented the Annual Report for the year 2018-19. Mr. H I Gandhi
proposed and Dr. T Senthilkumar seconded the report. The report was unanimously adopted by the
AGM.
Hon. Treasurer Mr. G. Rajendran submitted the audited accounts for the year 2018-19. Dr. P
Sivaprakash proposed and Mr. L Ramachandran seconded. The AGM approved and adopted the same.
Mr. G Rajendran, Hon. Treasurer moved the following resolutions in the AGM.
Resolution 1: IWS 2k12 bank account: Ref Note 2: of audited report
Due to lack of transactions, the IWS 2k12 account was
frozen by ICICI Bank, Mumbai branch. Efforts are on to
receive the amount Rs. 692685.10. Already discussions
were held with ICICI Bank. It is proposed to authorise the
Hon. Treasurer, Hon. Secretary and authorised
signatories of the account to discuss with the bank and
bring back the amount to IWS.
Mr. K Sureshkumar proposed and Mr. R. Arunan
seconded. The AGM approved the resolution.
AROUND
Page 5 of 33
Resolution 2: Write off of unrecoverable balances:
It is proposed to write off of the unrecoverable balances as indicated below, totaling to Rs. 656941.10.
CENTRE / EVENT NAME FINANCIAL YEAR NATURE OF RECEIPT AMOUNT TO BE WRITTEN
OFF
IWS-SZ FY 2013-14 DELEGATE FEES 8000
IWS-SZ FY 2013-14 SPONSORSHIP FEES 10000
IWS-SZ FY 2014-15 DELEGATE FEES 10674
IWS-SZ FY 2015-16 DELEGATE FEES 140
IWS-SZ FY 2017-18 DELEGATE FEES 950
IWS-HQ MAIN FY 2015-16 DELEGATE FEES 77520
IWS-NZ FY 2017-18 DELEGATE FEES 102350
IWS- CHENNAI FY 2017-18 DELEGATE FEES 22800
IWS- COIMBATORE FY 2016-17 DELEGATE FEES 837
IWS 2K14 FY 2014-15 DELEGATE FEES 63436
IWS 2K14 FY 2014-15 ADVERTISEMENT 50000
IWS 2K14 FY 2014-15 SPONSORSHIP 98000
IWS 2K16 FY 2016-17 DELEGATE FEES 69000
IWS 2K16 FY 2016-17 ADVERTISEMENT 87017
IWS 2K16 FY 2016-17 SPONSORSHIP 20000
IWS MEMBERSHIP FY 2015-16 SERVICE TAX 21630
IWS NZ FY 2012-13 TDS 9587
IWS SZ FY 2013-14 TDS 5000
TOTAL 656941
Mr. L D Prabhu proposed and Dr. S. Jaishankar seconded. The AGM approved the resolution.
Mr. N Rajasekaran, Hon. Secretary moved the following resolution.
Resolution 3: Set apart of part of income for purpose of the trust
Out of the income of the trust for the previous year, relevant to the assessment year 2019-20, an
amount of Rs. 36,87,471 which is 75 (%) per cent of the income of the trust for the said previous year,
shall be accumulated or set apart for carrying out the purposes of the trust. The period of set apart
ends on 31/03/2024.
Mr. S Singaravelu proposed and Mr. G Uma Shanker seconded. The AGM approved the resolution.
Then, Mr. A. Maruthamuthu, Vice President addressed the members. In his address he said, “I am
happy in double count one is that in the last two years IWS has successfully conducted two mega events,
the SOJOM at SZ and IWS 2k18 at Mumbai. IWS entered into an MOU with COEWT, PSGTECH,
Coimbatore for conducting the Fresh Engineers Course”. He took pride that during the period the ADD
ON Course for engineering colleges was launched successfully at KSRCT, Tiruchengode and the same
can be spread at all colleges”. Further, he said, “the other reason for my happiness is that IWS will lead
by and able leader Mr. R Padmanabhan, Executive Director, BHEL for the period 2019-21.
Page 6 of 33
Since Dr V P Raghupathy, Returning Officer IWS Elections 2019, could not come due to personal reasons,
vide E mail he has authorised Mr. G Rajendran to announce the election results. Mr. G Rajendran
informed the results to the AGM for the NGC, Zones and centres (Wherever election was conducted).
The AGM endorsed the results.
Mr. R Easwaran, former Chairman (TC) of IWS installed the office bearers and NGC members. He said,
“I am confident that under the leadership of Mr. R Padmanabhan, the dynamic team will achieve newer
heights and bring laurels to IWS.”
Mr. R Padmanabhan, Executive Director, BHEL assumed charge as
President of IWS for the period 2019-22. Mr. N Rajasekaran took charge
as Hon. Secretary and Mrs. A. Santhakumari, as Hon. Treasurer. Mr.
Himanshu Gandhi and Dr S Aravindhan took over as vice presidents along
with NGC members. Mr. G Uma Shanker, former Chairman, Educational
Committee of IWS offered his felicitations.
Then, Mr. R. Padmanabhan, President addressed the members. During his address he unveiled the
vision for the tenure, as detailed below.
1. Increasing the membership including the industrial corporate
members
2. To vibrate the zones and centers with the support of IWS stalwarts
and experienced members.
3. Training and skill development to school dropout and bring them in the main stream by making
eligible to earn their livelihood.
Page 7 of 33
4. To encourage the students to take welding as a prime career over blue collar job.
5. To bridge the gap and demand of qualified welding engineers, supervisors and welders of quality
class in various segments, positions and skill to join the different materials for Indian industries
and projects abroad.
6. To help CSR company to spend their CSR earmarked allocated funds under section 135 of
companies act in the area of education, training and skill development through IWS.
7. To create the different module to help the industry to be competitive in the global world and
sharing of welding related knowledge to IWS members and the general beneficiaries of the
society who are in need for the same.
8. Signing the MOU with various international research institute and company to bring the 21st
century the latest technology and know-how at the door steps of MSME enterprises and startups
in India.
He sought the support of all the members to convert the said visions to the reality by working hard and
collectively.
Mr. R Padmanabhan felicitated the outgoing Vice President Mr. A Maruthamuthu and Mr. G Rajendran,
Hon. Treasurer.
Then Mrs. A. Santhakumari, Hon. Treasurer moved the motion to retain
the services of M/s. K. S. GUPTA & CO. as auditor for the year 2019-20.
The AGM unanimously approved the motion. The AGM also accepted the
proposal mooted by Mrs. A. Santhakumari, Hon. Treasurer that the
remuneration for the auditor will be decided by the NGC. Dr. T Senthilkumar proposed and Dr. K
Asokkumar seconded.
It was also resolved by the
AGM that the modified rules
and regulations of the society
will be submitted in the next
EGM / AGM for consideration.
Mr. N Parameswaran,
conducted the proceedings.
The AGM concluded with the
vote of thanks proposed by
Mrs. A. Santhakumari, Hon. Treasurer of IWS. The AGM ended with a dinner.
Page 8 of 33
Page 9 of 33
KNOWLEDGE SHARING
Inauguration of student forum (IWS) and One day workshop
on “Recent Advances in Welding” - RAW 2019 at MCET, Hyderabad
On 22nd August 2019 , Dr. K. Thyagarajan, Chairman, Indian
Welding Society (IWS), Hyderabad centre has inaugurated the
IWS student forum and one day workshop on “Recent Advances
in Welding” RAW 2019, at Methodist College of Engineering &
Technology (MCET), King Koti Road, Abids, Hyderabad – 500 001.
Dr. S. Venkateshwar, Dean, MCET, Welcomed the gathering. Dr.
A Rajasekhar, Hon. Secretary, IWS, Hyderabad centre and Professor & Head, Department of Mechanical
Engineering, MCET has briefed about the
student forum and “RAW 2019” workshop.
In his address, Dr. Ravinder Reddy, Principal,
MCET has welcomed the initiative taken by
the department and expressed his hope that
students under this forum will get
benefitted by IWS in the form of lectures,
internships and projects.
During the inaugural address Dr. K. Thyagarajan, Chairman,
Indian Welding Society (IWS), Hyderabad centre emphasized the
importance of advanced welding technologies in structural
industry.
Dr. G. Madhusudhan Reddy motivated the students to do
research in the field of welding technology. In his presentation
he has focused on the latest welding technologies and general
challenges in application of these technologies to different
materials. Shri C. V. S Murthy has delivered expert lecture on
various types of advanced welding techniques and used in
aerospace industry. Shri Nagi Reddy inspired the students
regarding the personality qualities and highlighted the uses of
welding in the daily human life.
Page 10 of 33
Nearly 140
members including
students, faculty
members from
various engineering
colleges from
Telangana and
Andhra Pradesh &
industry personnel
participated and
got benefit from the
workshop.
Dr. P. Prabhuraj,
IWS student forum
Advisor, Associate
Professor, Mech.
Engineering, MCET
proposed vote of
thanks.
Page 11 of 33
SEMINAR ON "ADVANCEMENT OF WELDING IN BOILERS INDUSTRIES" @
RIT STUDENT FORUM
RIT - IWS Student Forum along with the Mechanical Department Association “RIT- Mechanizo”
conducted a seminar on "Advancement of Welding in Boilers
Industries" during 06.07.2019 for the student forum members
and Mechanical Engineering students.
Mr. N. Rajasekaran, Hon. Secretary (IWS) inaugurated the
department association and seminar. In his technical talk on the
theme of the seminar, he elucidated on “Types of Welding
Processes viz,. GMAW, GTAW, SAW, SMAW, FCAW, FSW, etc., and advances in welding of boiler
materials.”
HANDS ON TRAINING AND WORKSHOP ON “MODERN SURFACE
COATING TECHNOLOGY” @ RIT STUDENT FORUM
RIT – IWS Student Forum in association with the Department of
Mechanical Engineering of Ramco Institute of Technology,
Rajapalayam organised a Hands on Training and Workshop on
“Modern Surface Coating Technology” in Surface Engineering for
students those who are pursuing value added course MVA 009 –
Surface Coating Technology and Indian Welding Society Students
Members on 03.08.2019.
The Expert Speaker Dr. M. Adam Khan, Post-Doctoral Research Fellow, University of Johannesburg,
South Africa delivered the lecture on topic “Modern Surface coating Technology” in Surface Engineering
and handled sessions on “hands on training on surface coating technology”. 42 students’ members have
attended the session. The Faculty Advisor of RIT – IWS Student Forum, Mr. S. Maharajan, co-ordinated
the event and welcomed the expert speaker and gathering.
WORKSHOP ON “RECENT DEVELOPMENTS IN WELDING TECHNOLOGY”
BY KSRCT STUDENT FORUM
On 19th August 2019, the KSRCT - IWS Student Forum in association with Department of Mechanical
Engineering, K. S. Rangasamy College of Technology organized
a Workshop “Recent Developments in Welding Technology” at
the college premises.
The workshop conducted at the Seminar Hall, Main building
was inaugurated by Mr. N. Rajasekaran Hon. Secretary (IWS) in
the presence of Mr. S. Singaravelu, Vice Chairman, IWS, SZ. The inauguration started with invocation
Page 12 of 33
song followed by the welcome address by Dr. K Mohan, Faculty Advisor of KSRCT – IWS Student forum.
Dr. K. Thyagarajah, Chief Executive Officer, K.S.R. Educational Institutions presided over the function.
In his address, he said, “Welding plays a crucial role in manufacturing in all
type of industry. Gaining knowledge on welding will be more helpful for the
young engineers to excel in their fields.”
In his inaugural address, Mr. Rajasekaran gave an overview on the
opportunities available for welding engineers. He also congratulated KSRCT
for offering the Add on Course in Welding with IWS. He also said, “It is giving
immense pleasure to IWS that its services are reaching the budding
engineers. My thanks are to Mr. S Singaravelu for coordinating the course, effectively”.
After the inauguration, Mr. Rajasekaran handled a session on
“Advances in Gas shielded welding processes” covering the basics,
applications and advances in GTAW, GMAW and plasma welding
processes.
Post lunch, Mr. S. Singaravelu made a technical presentation on
“Advances in Flux Shielded welding processes”. The lecture encompassed the applications of SMAW
and SAW processes and the basics and advances also.
In the evening, Mr. S Singaravelu distributed the certificates to the
participants in the presence of Mr. Rajasekaran and Dr Mohan.
The workshop was coordinated by Dr. K. Mohan, Professor & Faculty
Advisor, IWS student Forum and Mr. R. Prakash, Assistant Professor,
K. S. Rangasamy College of
Technology. 60 student
members from K. S. Rangasamy college of Technology actively
participated in the free workshop. The workshop concluded with
the vote of thanks by Mr. Karthikeyan, Assistant Professor, K. S.
Rangasamy College of Technology.
Page 13 of 33
EFFECT OF ATIG WELDING PROCESS PARAMETERS ON THE
MECHANICAL AND MICROSTRUCTURE PROPERTIES OF SUPER DUPLEX
STAINLESS STEEL
A. Arun Mani*& Dr. T. Senthil Kumar **
*Research Scholar, Department of Mechanical Engineering, Anna University Tiruchy
**Professor, Department of Mechanical Engineering, Anna University Tiruchy
ABSTRACT
In this investigation of super-duplex stainless steels (UNS S32750) by Activated
Tungsten inert gas welding (ATIG) using super duplex stainless steel fillers. In
recent years, very high strength, corrosion resistive UNS 32750 super duplex
steel is being used in chemical industries and marine sectors for manufacturing
lifting equipment and Cryogenics applications. Activated Tungsten inert gas
welding (ATIG) is a fusion welding methodology which is being successfully
used to join super duplex stainless steel material. In this investigation, ATIG
welding was used to weld 32750super duplex stainless steel material, by
fluctuating vital process parameters such as torch travel speed, welding
current and welding voltage. After welding, the test samples were non-
destructively tested to ensure no defects and test samples were prepared for
micro structural examinations and ferrite content measurements. The root
region had complex microstructure because of the repetitive heating of the
zone during different weld layers. It was observed that at low heat input
desirable microstructure was formed. Also the presented results reported the
effect of filler metals on strength and toughness during the multi-pass welding.
Using response surface methodology, the ATIG welding process parameters
were optimized for the improvement of tensile and impact strength using
appropriate filler wire without obtaining any deleterious phases.
Keywords: Super Duplex Stainless Steel, Activated Tungsten Inert Gas (ATIG),
Microstructure Analysis.
1.0 INTRODUCTION
Super-duplex stainless steels present excellent combination of mechanical and corrosion
resistance, due to their strict composition control and ferrite austenite phase balance. This
balance may however be disturbed during welding in both the fusion and HAZ due to the rapid
cooling rates and may lead to loss of the good corrosion and mechanical properties of the
weldments. All the data have been collected through various literature surveys and journals. The
required proposed welding procedure specification is prepared to conduct the welding test. Two
experiments are carried out to analyze the issues.
Page 14 of 33
One weldment by argon and another element by argon with 2% nitrogen mixture as inert gas by
Gas Tungsten Arc Welding process. Various tests will be carried out on the welded test specimen
and the results will be analyzed. Duplex Stainless Steels (DSS) combine corrosion resistance and
high mechanical strength. They are often used for applications that require higher resistance to
chloride stress corrosion cracking, pitting, inter-granular attack and crevice corrosion than
Austenitic Stainless Steels (ASS). Applications include components for hydro-processing units,
sour water strippers, crude and amine units, brackish water piping, fuel gas piping and marine
equipment. Higher yield strength than ASS is an attractive property which results in significant
material savings during design by reducing the required wall thickness. Thermal conductivity is
superior to ASS while thermal expansion is comparable with that of carbon steel which reduces
the amount of distortion and welding residual stresses.
The SDSS are more highly alloyed than the other duplex grades and can withstand more
aggressive environments. The most commonly used SDSS is grade UNS S32750 which contains
about 25 % Cr, 7 % Ni, 4 % Mo and 0.24-0.32 nitrogen as alloying elements. Various product forms
are typically used in the oil sand industry including welded and seamless piping, forgings, fittings,
and plate.
These steels have a duplex microstructure which contributes to their high strength and high
resistance to stress corrosion cracking. Duplex steels offer high resistance to uniform and local
corrosion because of their high content of nitrogen, chromium and molybdenum. Duplex
stainless steels have good weldability. There are three groups of duplex stainless steels that
include the following steels Lean Duplex, Standard Duplex and Super Duplex. The most widely
used of the duplex grades is duplex 2205. However, the super duplex steels like 2507 are excellent
for servicing severe corrosive environments, such as offshore and marine applications. Lean
duplex 2101 is available as an economic alternative to 300 series stainless steels.
Stainless steels are iron-base alloys containing 8–25 % nickel and more chromium than the 12 %
which is necessary to produce passivity but less than 30 %. The steels resist both corrosion and
high temperature. Stainless steels can be divided into five types as Ferritic, austenitic,
martensitic, duplex and precipitation-hardening. Ferritic stainless steels are widely used due to
the fact that their corrosion resistance is higher at room temperature and they are much cheaper
than the other stainless steels. Ferritic stainless steels contain 16-30 % Cr within their structures
in respect of addition of the alloy element. This type of the steel can be shaped easily and resist
atmospheric corrosion well and thanks to these characteristics, it has a wide range of application
in architecture, interior and exterior decoration, kitchen utensils, manufacturing of wash boilers
and drying machines, food industry, automotive industry, and petrochemical and chemical
industries.
Austenitic-stainless steel is preferred more than other stainless-steel types due to easiness in
welding process. Then, some negative metallurgic changes are taken into consideration in
welding of the steels. These are given as; delta ferrite phase, sigma phase, stress-corrosion
Page 15 of 33
cracking, chrome–carbide precipitate between grain boundaries at 450–850 °C of Cr–Ni austenitic
steels such as 18/8 joined by fusion welding in long waiting time.
Stainless steels can generally be welded with all methods of fusion welding and solid state
welding. Out of the fusion welding methods, electric arc welding, submerged arc welding, MIG,
TIG, Plasma welding, electron beam welding, resistance welding, and laser welding etc. are
widely used. In the fusion welding methods for joining the stainless steel, brittle intermetallic
compounds phases are produced in the fusion zone, which reduces the strength of the welding
joint. However, in the TIG joining of stainless steel, because these phases are reduced, it improves
the performance of the stainless steel joint. Super Duplex UNS S32750 has excellent corrosion
resistance in a wide variety of corrosive media making it ideal for use in environments exposed
to the harshest chemical conditions. It has outstanding resistance to pitting and crevice corrosion
in seawater and other chloride containing environments, with Critical Pitting Temperature
exceeding 50 °C. Compared to austenitic and 22 % Cr duplex stainless steels, UNS S32750 is of
higher strength and even more suitable in situations where it will be exposed to extremely high
stresses. This combined with its excellent ductility and impact strength at both ambient and sub-
zero temperatures further increases its appeal as the ultimate super duplex grade.
High resistance to abrasion, erosion and cavitation erosion combined with excellent resistance to
stress corrosion cracking in chloride containing environments makes UNS S32750 perfect for use
in the Oil and Gas Industries where subsea equipment is subject to some of the harshest chloride
containing conditions in the world. Stainless steel Super Duplex 2507 is designed to handle highly
corrosive conditions and situations were high strength is required. High molybdenum, chromium
and nitrogen content in Super Duplex 2507 help the material withstand pitting and crevice
corrosion. The material is also resistant to chloride stress corrosion cracking, to erosion corrosion,
to corrosion fatigue, to general corrosion in acids. This alloy has good weldability and very high
mechanical strength. UNS S32750 is listed in NACE MR 01 75 for sour service for its suitability of
use for oilfield equipment where sulphide stress corrosion cracking may be a risk in hydrogen
sulphide (sour) environments. UNS S32750 is also ASME Approved for Pressure Vessel
applications
2.0 MATERIALS AND METHOD
In the paper, UNS 32750 grade super duplex stainless steel of thickness 10 mm was selected as
the base material. Using abrasive cutters, they were cut to 200 mm in length and 140 mm in
breath. The base material was cleaned using acetone for dust and grease removal. The base
material microstructure was studied using optical microscope at 100 x magnification. The
microstructure samples were polished using emery sheets with grits varying from 220 to 1200.
The optical microstructure revealing the austenite and ferrite structure was examined and
indicated in Fig 1.
Page 16 of 33
Fig 1. Base Material Microstructure Displaying a Combination of Ferrite and Austenite
Fig 2. Activated Tungsten Inert Gas Welding (ATIG)
S32750 combines high tensile and impact strength with a low coefficient of thermal expansion
and high thermal conductivity. These properties are Suitable for many structural and mechanical
components. The low, ambient, and elevated temperature mechanical properties of S32750
sheet and plate are shown below. All of the test data shown are for samples in the annealed and
quenched condition. S32750 is not recommended for applications which require long exposures
to temperatures in excess of 570 °F because of the increased risk of a reduction in toughness. The
data listed in this document are typical for wrought products and should not be regarded as a
maximum or minimum value unless specifically stated. Welding of 300 series usually requires
preheat and post-weld heat treatment to minimize stress that can lead to cracking. The chemical
compositions and physical properties of both steels were given in Table 1 & 2 respectively.
Table 1. Chemical composition of super duplex stainless steel S32750
Elements C Cr Cu Mo Mn N Ni P S Si W
Minimum - 24.0 - 3.00 - 0.24 6.00 - - 0.20 0.50
Maximum 0.030 26 0.50 5.00 1.20 0.32 8.00 0.035 0.020 0.80 1.00
Page 17 of 33
Table 2 Physical properties of super duplex stainless steel S32750
Density (Kg.m-1) 7810
Magnetic Permeability 33
Young’s Modulus (N/mm2) 199 x 103
Specific Heat, 20°C (J.Kg-1.°K-1) 475
Fracture Toughness, Kq (MPa.m) 475
Specific Electrical Resistance, 20°C (µO.m) 0.80
Thermal conductivity, 20°C (W.m-1.°K-1) 14.2
Mean coefficient of thermal expansion, 20-100°C (°K-1) 11.1 x 10-6
Table 3 Mechanical properties of super duplex stainless steel S32750
0.2% Proof Stress 550 N/mm2
Tensile Strength 800 N/mm2
Elongation, 5.65√S0 25%
Reduction of area 45%
Hardness (Brinell) <270
Impact Strength (Room Temp) 80J
Impact Strength (-46oC) Longitudinal 45 J (35 J min)
Here the mechanical properties of super duplex stainless steel had been shown in Table 3.
2.1 Corrosion Resistance
The high chromium and molybdenum content of Super Duplex makes it extremely resistant to
uniform corrosion by organic acids like formic and acetic acid. Super Duplex also provides
excellent resistance to inorganic acids, especially those containing chlorides.
The pitting Resistance equivalent of Super Duplex, calculated by PREN = Cr + 3.3 Mo + 16 N, will
exceed 40 in most material forms.
3.0 DIMENSION OF WELDING MATERIAL
In this investigation the dimension taken as 200mm length, 140 mm width and 10 mm thickness.
By using the above dimensions the super duplex stainless steels plates were used to fabricate the
joints. After the fabrications tensile test and micro structure specimens were prepared by using
wire cut electrical discharge machine. Eighteen plates had been machined and by that nine joints
has been joined by using Activated Tungsten Inert Gas Welding (ATIG).
Page 18 of 33
4.0 RESULTS AND DISCUSSIONS
4.1 Mechanical Properties
According to ASTM E8/8M standards, the tensile test specimens were prepared and subjected to
tensile failure tests. Micro hardness at the joint region was measured using Vickers micro
hardness testing equipment. In the weld centre, at three different regions, the micro hardness
measurement was done and the average of the three was recorded to be used for further
evaluation. The tensile strength and the weld region micro hardness of the super duplex steel
joints fabricated with the activated tungsten inert gas welding process parameter value
combinations are shown.
Here for finding the mechanical properties several trials had been carried out and finally the
optimum results of tensile strength, yield strength and elongation were found. For finding the
tensile test results ASTM/E8 had been carried out for nine joints. Here the maximum and
minimum of tensile strength, yield strength and elongation has been listed below.
Table 4 Mechanical properties of Super Duplex Stainless Steel (S32750)
Specimen Tensile Strength (MPa) Yield Strength (MPa) Elongation (%)
1 853.99 697.57 24.67
2 854.25 698.17 24.15
3 854.75 700.63 23.34
4 870.04 718.02 20.90
5 871.54 720.39 21.65
6 870.96 719.50 21.05
7 881.76 756.17 17.47
8 880.96 755.80 18.25
9 870.04 718.02 20.90
4.2 MICROSTRUCTURE RESULT
The investigation revealed that the microstructure as well as the impact property of the weld
metal was significantly affected by the heat input and filler wire. Concerning the filler metal.
Super duplex stainless steel welding by Activated Tungsten inert gas welding (ATIG) the various
parameter. For finding the metallurgical properties METSCOPE-1A Microscope equipment had
been used. The microstructure revealed elongated grains of austenite in a matrix of ferrite. The
microstructure revealed coarser interdendritic chromium-carbide precipitation. The
microstructure revealed fine interdendritic of chromium-carbide precipitation.
Base: The microstructure revealed elongated grains of austenite in a matrix of ferrite.
Page 19 of 33
HAZ: The microstructure revealed coarser interdendritic chromium-carbide precipitation.
Weld: The microstructure revealed fine interdendritic chromium-carbide precipitation.
Microstructure of Base, Weld and Heat affected Zone of SDSS 32750 plates are shown in Fig 4.1
Here for studying the micro structural characteristic due to the effect of activated tungsten inert
gas welding on the super duplex stainless steel several specimens had been taken and finally
three optimized process parameter values were subjected to microscopic evaluation
Fig 3 (a) Microstructure of Base, Weld and Heat Affected Zone for 40 W heat input
Fig 3 (b) Microstructure of Base, Weld and Heat Affected Zone for 60 W heat input
Fig 3 (c) Microstructure of Base, Weld and Heat Affected Zone for 80 W heat input
From the above characteristics the Fig 3(a) studies indicates the microscopic structure of the base
material of UNS 32750 super duplex stainless steel material which remained unaffected during
the thermal cycles which were induced during welding. Fig 3 (b) shows the heat affected zone
which has been slightly coarsened during the welding process. Fig 3 (c) indicates the weld region
microstructure, where platelet elongation was observed.
Page 20 of 33
5.0 CONCLUSIONS
In this paper, enhancement of mechanical aspects of UNS 32750 super duplex stainless steel
joints, by optimizing welding process parameters of ATIG welding has been conducted. The
information obtained from the investigation is being summarized as follows
At 150 W heat input a better microstructure, micro hardness and tensile properties is
achieved
Higher tensile strength of 881.76 MPa and yield strength of 156.94 MPa were formed at
150 W heat input.
Interaction and perturbation plots showed that variation in gas flow rate had greater
influence on joint properties than torch travel speed and weld current. Microscopic
evaluation of joints indicated grain coursing in heat affected zone and platelet elongation
in weld zone.
REFERENCES
1. Sarlak H, Atapour M, Esmailzadeh M. Corrosion behavior of friction stir welded lean duplex stainless steel.
Materials & Design. 2015;66:209-16.
2. Bettahar K, Bouabdallah M, Badji R, Gaceb M, Kahloun C, Bacroix B. Microstructure and mechanical behavior
in dissimilar 13Cr/2205 stainless steel welded pipes. Materials & Design. 2015;85:221-9.
3. Ramkumar KD, Thiruvengatam G, Sudharsan S, Mishra D, Arivazhagan N, Sridhar R. Characterization of weld
strength and impact toughness in the multi-pass welding of super-duplex stainless steel UNS 32750. Materials
& Design. 2014;60:125-35.
4. Kang DH, Lee HW. Effect of Different Chromium Additions on the Microstructure and Mechanical Properties
of Multipass Weld Joint of Duplex Stainless Steel. Metallurgical and Materials Transactions A. 2012;43:4678-
87.
5. Ramkumar KD, Mishra D, Raj BG, Vignesh M, Thiruvengatam G, Sudharshan S, et al. Effect of optimal weld
parameters in the microstructure and mechanical properties of autogeneous gas tungsten arc weldments of
super-duplex stainless steel UNS S32750. Materials & Design. 2015;66:356-65.
6. Karlsson L, Börjesson J. Orientation relationships of intragranular austenite in duplex stainless steel weld
metals. Science and Technology of Welding and Joining. 2014;19:318-23.
7. Kim S-T, Jang S-H, Lee I-S, Park Y-S. Effects of solution heat-treatment and nitrogen in shielding gas on the
resistance to pitting corrosion of hyper duplex stainless steel welds. Corrosion Science. 2011;53:1939-47.
8. Tan H, Jiang Y, Deng B, Sun T, Xu J, Li J. Effect of annealing temperature on the pitting corrosion resistance of
super duplex stainless steel UNS S32750. Materials characterization. 2009;60:1049-54.
9. Wessman S, Pettersson R, Hertzman S. On Phase Equilibria in Duplex Stainless Steels. steel research
international. 2010;81:337-46.
10. Sadeghian M, Shamanian M, Shafyei A. Effect of heat input on microstructure and mechanical properties of
dissimilar joints between super duplex stainless steel and high strength low alloy steel. Materials & Design.
2014;60:678-84.
Page 21 of 33
MICROSTRUCTURAL CHARACTERISTICS OF SHIELDED METAL ARC WELDED DISSIMILAR JOINTS OF ARMOUR STEELS
1S. Abhijith, 2V. Balasubramanian, 3S. Malarvizhi, 4A. Hafeezur Rahman &5V. Balaguru
1,2,3 Centre for Materials Joining and Research (CEMAJOR)
Department of Manufacturing Engineering, Annamalai University, Annamalainagar
4,5 Combat Vehicle Research and Development Establishment (CVRDE), Avadi, Chennai
ABSTRACT
The life expectancy of high strength and high hard armour grade steels has become
limited due to the prevalence phenomenon of heat affected zone (HAZ) softening and
hydrogen induced cracking (HIC). The higher the hardness and strength of armour
grade steel, the greater is the difficulty in making welds due to the presence of higher
carbon content and higher carbon equivalent number which makes the steel
susceptible to HIC and HAZ softening. Hence, the microstructural characteristics of the
dissimilar weldments were analysed on the basis of micro hardness and
microstructural studies. A comparative study has been made between weldments
obtained using three electrodes namely low hydrogen ferritic (LHF), austenitic
stainless steel (ASS) and duplex stainless steel (DSS) electrodes. The joints fabricated
using LHF electrodes showed wider HAZ whereas the joints fabricated using ASS
electrodes showed narrow HAZ and DSS joint showed moderate HAZ due to the
difference in weld thermal cycle as well as their intermixing with the base metal during
their fabrication.
Keywords: Armour steel, shielded metal arc welding, dissimilar joint, microstructure,
microhardness, HAZ
1.0 INTRODUCTION
The higher overall weight of Armoured Tracked Vehicles (ATV) has forced the designers to
develop Ultra-High Hard Armour (UHA) steel despite of currently used Rolled Homogenized
Armour (RHA) steel. The properties of these steels are distinct which are obtained from their
composition and special heat treatment processes – quenching and tempering (Q&T) with an
impressive ballistic behavior in terms of deformation capacity and resistance to multiple impacts.
Q&T steels dominates in ductility and notch toughness which makes them suitable where specific
strength is desirable [1]. Hydrogen induced cracking (HIC) and the development of mushy zone in
the heat affected zone (HAZ) are the situations that need attention while welding. These steels
are predominantly welded using conventional welding processes and hence demands proper
precaution during welding to avoid premature failure of the weldments.
Quenched and tempered steels are prone to HIC in the soft zone. The susceptibility of cracking is
attributed to hardness and microstructure of the steel, magnitude of tensile residual stresses and
Page 22 of 33
the level of diffusible hydrogen. The increase in solubility of hydrogen at higher temperatures
enables the individual hydrogen atoms to diffuse through the metal and gradually recombines to
form hydrogen molecules. The steel becomes brittle and fracture due to the pressure associated
with the hydrogen molecules within the metal. Hence, proper filler metal selection, welding
process and often pre- and post-heating of the weldments are essential to avoid hydrogen
embrittlement post welding [2].Austenitic stainless steel (ASS) finds demand for the welding of
high hardness armour steel due to its higher solubility of hydrogen in austenitic phase. The service
requirements includes good resistance to cold cracking and hot cracking for which these steels
are well established. Hence, these steels are manipulated to weld ultra-high hard armour steel
[3]. The use of stainless steel filler for a non stainless steel base metal must be avoided as ASS
filler are much more expensive. Currently, the development of low hydrogen ferritic steel (LHF)
consumables having no hygroscopic elements are preferred for welding high hard armour steels
[4,5].The majority of the armour fabrication is performed by fusion welding process due to which
they exhibit HAZ softening when exposed to weld thermal cycles and alters the ballistic
performance required for the military vehicle application. The softening characteristics not only
depends on the weld thermal cycle but also the kinetics of the phase transformation and the
chemical composition of the steel employed. Recent studies reported that the HAZ softening is
the least in SMAW process for the high strength armour grade steels [6].
Armour grade Q&T steels have been widely fabricated using SMAW process and demands high
welding quality and proper selection of welding consumables. Apart from these technical as well
as economic aspects of dissimilar weld fabrication of armour grade steels are indispensable.
Hence, in this investigation an attempt has been made to compare the microstructural
characteristics of armour grade Q&T steel dissimilar joints fabricated by SMAW process using
ASS, LHF and DSS electrodes.
2.0 EXPERIMENTAL PROCEDURES
The base metals (BM) used in this investigation are RHA and UHA steel. The microstructure of
both the BM exhibits tempered martensite (Figure 1). Rolled plates of 10 mm thick BM were
sliced into the required dimensions (300×150 mm) by abrasive cutters and grinding. Single ‘V’
butt joint configuration, as shown in Figure 2, was prepared to fabricate the joints by SMAW
process. The initial joint configuration was obtained by fastening the plates in position using tack
welding. The direction of welding was normal to the rolling direction. All necessary care was
taken to avoid joint distortion and the joints were made after holding the plates in a welding
fixture. ASS, LHF and DSS consumables were used to fabricate the joints. Vacuum spectrometer
(ARL Model: 3460) was used to study the chemistry of the weld metal (WM) and BM. Sparks were
ignited at various locations of the weld region and their spectrum was analysed for the estimation
of respective alloying elements. The chemical composition and mechanical properties of the BMs
and WMs are presented in Table 1 and Table 2. The process parameters used in the fabrication
of the joints are given in Table 3.
Page 23 of 33
The microstructure analysis of the weldments were carried out using a light optical microscope
(Make: MEIJI, Japan; Model: ML7100). The weldments were sliced in transverse sections and the
specimens for microstructural and micro hardness analysis were extracted from the weldments.
The specimens were ground and polished using SIC abrasive papers and fine polished upto 1µm
using velvet cloth. The specimens were then etched with 2% nital reagent to reveal the
microstructure of the weld, BM and HAZ regions of the LHF weldments. Aqua regia and Kalling’s
reagent was used to reveal the microstructure of the ASS weld and DSS weld regions respectively.
3.0 RESULTS
3.1 Macrostructure
The macrograph of the joints at transverse cross-section and at the top surface of the weldment
is furnished in Figure 3. Comparing the width of the fusion zones of three joints, DSS joints are
having moderate width whereas ASS joints having the lowest and LHF joints having the highest.
A similar trend has been followed in the case of HAZ also for all the three cases. The weld defects
such as lack of penetration, lack of side wall fusion, porosity were absent in all the three
weldments. The top surface macrograph also depicts fabrication of defect free joint. In Table 4 it
shows the quantitative analysis of the different zones from top to bottom at the transverse cross
section of the weldment. The size of the WZ and HAZ were calculated in the form of area in which
LHF joints shows maximum WZ area of 210.6 mm2 whereas ASS joint shows the lowest WZ area
of 142.8 mm2.
3.2 Microstructure
The micrographs of the joints at various region of both UHA and RHA are depicted in Figures 4-6.
The microstructural analysis was performed at different location. From the micrographs, it is well
comprehended that the entire joint invariably consists of three distinctive regions. They are weld
metal (WM) region, coarse grain heat affected zone (CGHAZ) and fine grain heat affected zone
(FGHAZ).
The WM region of the ASS joint unveils a skeletal delta ferrite in the plain austenitic matrix (Figure
4(a)) and the DSS joint discloses a regular delta ferrite in the austenitic matrix (Figure 5(a)) and in
contrast the LHF joint revealed small ferrite plates entirely in the matrix recognized as acicular
ferrite morphology (Figure 6(a)). The microstructure of the different regions for the weldments
are presented in Figures 4-6.
The microstructural analysis of FGHAZ invariably indicates a hardened region of untempered
martensite in all the joints. The ASS joint has a finer untempered martensite compared to DSS
and LHF joints in both UHA and RHA. Although, LHF joint exhibits a coarser untempered
martensite than the DSS joint in the FGHAZ. A similar trend as that in the case of FGHAZ was
absent in the CGHAZ region of all the joints.
Page 24 of 33
Away from the weld zone specifically the CGHAZ, all the joints reveal tempered martensite. The
micrograph of CGHAZ of DSS joints shows a fine tempered martensite in both UHA and RHA when
compared to other joints. In both UHA and RHA of ASS joint it shows a coarser tempered
martensite. The CGHAZ and FGHAZ of LHF joint in both UHA and RHA invariably shows coarser
tempered and untempered martensite respectively.
3.3 Micro hardness
The hardness across the weld cross-section was measured using a Vickers microhardness testing
machine. The micro hardness values for BMs, weld zones and HAZ were measured. The micro
hardness plot is displayed in Figure 7. The micro hardness (mean value) of the unwelded base
metal are 400 HV and 590 HV for RHA and UHA respectively. In spite of that the DSS joint shows
355 HV and LHF joint exhibits 350HV whereas ASS indicates the lower hardness of 240HV in their
respective weld metal region. The values of the hardness in FGHAZ of the joints are found to be
higher than those of the BMs. The values in this zone of ASS, LHF and DSS are 770 HV, 680 HV and
750 HV for UHA and 430HV, 580 HV and 590 HV for RHA respectively. The values in CGHAZ of ASS
joint are 395HV and 680HV in RHA and UHA respectively and shows higher hardness in the CGHAZ
of UHA.
4.0 DISCUSSION
This section discusses and comprehends the inferences of the above results. The adoption of DSS
electrode for welding armour grade steels was to intensify both toughness and the transverse
tensile properties of the joint. However, there is a difference in the dilution of the weld metal
with base metal.
4.1 Effect of Welding Consumables on Macrostructure
The crystal structure and the phases present in the weld metal plays an important role in the
fusion of weld metal to the base metal. However, outstanding mechanical and metallurgical
properties are attained if both weld metal and base metal consist of identical crystal structures
as well as phases. The armour grade steels obtained from special heat treatment processes –
quenching and tempering (Q&T) consists of tempered martensite. Hence, the steel is a
martensitic steel but they are also comprehended as ferritic steels. Delta ferrite is a residual
structure formed at high temperature and possess low temperature brittleness and minimum
solubility of carbon due to the shape of its atomic lattice. Also, ferrite structure are desirable in
all the weld structures as they serves proportionally higher strength and hardness [7].
The major constraint in welding armour grade steels is the presence of hydrogen in WM which
decreases the mechanical properties of metals. The formation of porosity, embrittlement and
cold cracking are connected with the presence of hydrogen in the WM. The favorable remedy is
to employ LHF consumables which virtually prevents the introduction of hydrogen in WM and
moreover increases the intermixing of weld metal and base metal substantially since, both weld
metal and base metal have similar crystal structure. But, in the case of ASS joint the intermixing
Page 25 of 33
is limited due to the difference in the phases and crystal structure. Hence, the weld joint
fabricated using ASS electrode will exhibit a distinct interface between weld metal and base
metal.
Duplex stainless steel consist of equal amount of austenite and ferrite phases furthermore a
suitable substitute for ASS and LHF consumable where both toughness and strength is a
challenge. There is a considerable amount of reduction in austenitic phase in the WM due to
their chemical composition. At high temperature there is complete formation of ferrite
undergoes grain growth thereby upon cooling austenite is formed along the ferrite grain
boundaries with a plate morphology [9]. The higher Cr content stabilizes the ferrite phase and
low Ni reduces the austenite phase thereby exhibiting equal amount of two phases. These steel
have higher strength than ASS and higher toughness than ferritic steels [10,11]. Hence, the weld
interface and the width of the weld zone is in-between the weld zone of LHF and ASS.
4.2 Effect of Welding Consumables on Weld Metal Microstructure
It is well known that the presence of austenitic phase in WM plays an important role in increasing
the toughness in WM. This is aided by the higher nickel content which improves the toughness
by reducing brittle ferrite phase and stabilizing the austenite phase [12]. The alloying contents of
Mn and Ni are very important in the solidification process in high strength steels [13,14]. The
primary solidification product in WM is delta ferrite which is transformed directly from the
molten metal. The delta ferrite at the core of the dendrites, which form at the beginning of
solidification, is very rich in chromium. However, the chromium content goes on decreasing as
the solidification proceeds. Proper control of the amount of delta ferrite in welds is very much
essential and critical. The higher amount of delta ferrite in welds tends to reduce the ductility
and toughness [15].
The WM chemistry of ASS shows low Cr (20 wt%) than DSS (25 wt%). The considerable increment
of Ni in ASS (9 wt%) than DSS (6.9 wt%) was observed. This difference in WM chemistry of Ni and
Cr in ASS and DSS joints has a great influence on the microstructural features. Thus ASS joints
have austenitic phase with a regular network of skeletal delta ferrite whereas DSS joints exhibits
homogenous mixture of regular delta ferrite in austenitic matrix.
4.3 Effect of Welding Consumables on Heat Affected Zone Microstructure
The microstructure in the HAZ is primarily a function of the thermal cycle imposed by the welding
process as well as chemistry of the BM. The weld thermal cycle is a function of heat input and the
thermal conductivity of the material [17]. The thermal conductivity of the armour grade steels
are generally lower for which they exhibits wider heat affected zone during fusion welding
processes. Moreover, the hardness of the HAZ is also a function of thermal cycle as well as the
carbon equivalent number. The thermal cycle plays an important role in altering the
microstructure of the HAZ during fusion welding which in turn alters the mechanical properties
of the HAZ.
Page 26 of 33
In fusion welding process of ferritic/martensitic steels, the joints invariably shows three distinct
regions of HAZ namely CGHAZ, FGHAZ and ICHAZ. The CGHAZ is near to the weld metal whereas
FGHAZ is away from weld metal and ICHAZ being observed in-between FGHAZ and BM. During
fusion welding process HAZ undergoes heat treatment cycle which assists this zone for
microstructural transformation. The armour grade steels used in Q &T form, transforms to
untempered martensite in HAZ during high heat input process such as fusion welding. Also, the
cooling rate in the different zones of HAZ alters the size of the grains resulting in coarser grains
near to fusion zone and finer grains away from fusion zone.
4.4 Effect of Welding Consumables on Micro hardness
In fusion welding process, the mechanical properties in HAZ can drastically differ from the
unaffected BM. This difference influenced by the chemical composition and the thermal cycle
imposed by the welding process. It has been reported that HAZ softening occurs during the
welding of Q&T steels [16]. The presence of soft zone in a welded structure alters the mechanical
properties and limits armour application [17].
In the present study a soft zone with a tempered martensite does exist in the CGHAZ away from
the fusion boundary for all the joints except DSS. There exist a non-uniform softening in the joints.
The CGHAZ of UHA for ASS joint exhibits higher degree of softening compared to BM and a
considerable amount of reduction in hardness in the LHF joint. When comparing the CGHAZ for
the three cases, ASS joint exhibits higher softening in both RHA and UHA (495 and 400 HV
respectively) whereas DSS joint recorded lower softening in RHA and UHA (535 and 710 HV
respectively). The above phenomenon is due to the difference in the heat input recorded during
welding. A heat input of 1.86 kJ mm-1 was recorded for the fabrication of ASS joint and hence
show higher softening. A heat input of 0.96 kJ mm-1 was recorded for the fabrication of DSS joint
thereby exhibit lower softening. A heat input of 1.5 kJ mm-1 was recorded for the fabrication of
LHF joint and shows moderate softening.
The degree of softening in the HAZ is a function of weld thermal cycle moreover a characteristic
of the welding procedure employed. Apparently, the above review proves the use of different
welding consumables significantly affects the CGHAZ softening characteristics due to the
difference in heat inputs.
5.0 CONCLUSIONS
The present study confirmed that dissimilar grade armor steels (RHA and UHA) can be welded
without defects using SMAW process. The important conclusions are furnished below.
(i) The LHF joints showed maximum inter-mixing of the WM and BM whereas ASS joint
showed the lowest mixing and DSS joint exhibited the moderate mixing due to difference
in the percentage of both austenitic and ferrite phases present in the weld metal region.
Page 27 of 33
(ii) The ASS and DSS joints showed narrow WM zone compared to LHF joint. This may be due
to maximum dilution that occurred because of compatibility of LHF electrodes with base
metal (both are ferritic phases).
(iii) The LHF joint shows wider HAZ compared to ASS and DSS joint due to maximum dilution
as well as high heat input. In all the joints, hardness of FGHAZ is higher compared to BM
and CGHAZ which is due to the presence of fine untempered martensite.
ACKNOWLEDGEMENT
The authors wish to record sincere thanks to Extramural Research & Intellectual Property (ERIPR),
DRDO, Ministry of Defence, New Delhi for the financial support rendered through a R&D project
no: EPIR/EP/RIC/2016/1/M/01/1630. The authors wish to thank the Director, Research &
Innovation Centre (RIC), DRDO, Chennai for his constant help and support. The authors are
grateful to the Director, CVRDE, Avadi, Chennai for providing base materials to carry out this
investigation.
REFERENCES
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and Technology Organization, Adelaide, Australia, 1–17.
3. G. M. Reddy, T. Mohandas and D. S. Sarma: Sci. Tech. Weld. Join, (2003), 8, (6), 407–414.
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shielded metal arc weldments of HY-80 steel. Mater Sci Eng (1988); 77:155–67.
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6. T. Mohandas, G. M. Reddy and B. S. Kumar: J. Mater. Sci. Technol., (1999), 88, 284–294.
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9. BADJI, R., BOUABDALLAH, M., BACROIX, B., et al., "Phase transformation and mechanical behavior in annealed 2205
duplex stainless steel welds", Materials Characterization (2008), v.59, n.4, pp. 447-453.
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13. M. Murugananth, H. K. D. H. Bhadeshia, E. Keehan, H. O. Andren and L. Karlsson: in ‘Mathematical modelling of weld
phenomena – VI’, (ed. H. Cerjak and H. K. D. H. Bhadeshia), 205– 230; (2002), London, Institute of Materials.
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797– 802; (2001), Tokyo, Japan Welding Society.
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Page 28 of 33
Table 1 Composition of base metals and filler metals (wt %)
Material C Si Mn Cr Mo Ni P S Fe
RHA 0.180 0.17 0.56 0.46 0.40 1.41 0.006 0.003 Bal UHA 0.315 0.239 0.54 1.25 0.52 1.25 0.018 0.009 Bal ASS 0.06 0.56 1.20 20.89 2.38 9.02 0.024 0.012 Bal LHF 0.049 0.544 1..59 0.58 0.55 2.08 0.023 0.011 Bal DSS 0.030 0.46 1.01 25.4 3.8 6.9 0.018 0.006 Bal
Table 2 Mechanical properties of base metals and filler metals (all weld metal)
Material 0.2% Yield strength
(MPa)
Ultimate tensile
strength (MPa)
Elongation in 50mm gauge
length (%)
Impact toughness
@ RT (J)
UHA 1450 2150 10 42 RHA 1050 1190 25 52 ASS 700 745 30 66 LHF 750 815 20 48 DSS 900 1000 30 56
Table 3 Welding parameters used to fabricate the joints
Parameters Unit ASS LHF DSS
Preheat temperature oC 200 200 200 Interpass temperature oC 150 150 150 Electrode baking temperature oC 200 350 200 Filler diameter mm 4 4 4 Welding current A 130 136 123 Arc voltage V 23 26 25 Heat input kJ mm-1 1.865 1.569 0.968
(a) RHA steel (b)UHA steel
Figure 1 Micrograph of base metals
Page 29 of 33
(a) (b)
Figure 2 (a) Joint configuration (b) Scheme of extraction of specimen
Joint Type
Macrograph (cross-section)
Macrograph (top surface)
ASS
LHF
DSS
Figure 3 Macrographs of welded joints
Table 4 Dimension (mm) of Weld Metal Zone (WMZ) and HAZ
Joint
Weld Metal Zone
RHA Side HAZ UHA Side HAZ
WMZ area
(mm2)
Width at top
side (mm)
Width at mid
thickness (mm)
Width at root
side (mm)
HAZ area
(mm2)
Width at top side
(mm)
Width at mid
thickness (mm)
Width at root
side (mm)
HAZ area
(mm2)
ASS 142.8 1.4 1.3 1.8 48.6 1.9 2.2 2.7 53.7 LHF 210.6 3.5 4.3 2.1 102.1 1.6 3.1 2.6 100.4 DSS 170.5 2.9 3.2 2.0 65.3 2.1 2.9 2.9 79.3
Page 30 of 33
RHA Side UHA Side
Figure 4 Microstructure of ASS weldments at various regions (a) WM (b, c) WM-HAZ interface (d, e) FGHAZ (f, g) CGHAZ
a a - high magnification
c b
d e
f g
Page 31 of 33
RHA Side UHA Side
Figure 5 Microstructure of LHF weldments at various regions (a) WM (b, c) WM-HAZ interface (d, e) FGHAZ (f, g) CGHAZ
a
b c
d e
f g
a - high magnification
Page 32 of 33
RHA Side UHA Side
Figure 6 Microstructure of DSS weldments at various regions (a) WM (b, c) WM-HAZ interface (d, e) FGHAZ (f, g) CGHAZ
a
c b
d e
f g
a - high magnification
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Figure 7 Microhardness plot of the weldment
Table 5 Micro hardness distribution across the weld (at mid-thickness region)
RHA Side Weld Metal (WM)
UHA Side
Weld Metal
FGHAZ CGHAZ WM-HAZ Interface
WM-HAZ Interface
CGHAZ FGHAZ
ASS 430 395 290 240 350 680 770 LHF 580 520 440 350 435 570 680 DSS 590 535 420 355 480 650 750