- K. Ratna Kumar
- K. Srinivasa Rao
- V. S. N. Venkata Ramana
- K. Ratnakumar
- P. Venkata Ramana
- P. K. Ghosh
- T. Mohandas
- Ashok Khanna
- Mrityunjoy Hazra
- P. Vijaya Kumar
- N. Venkateswara Rao
- S. Nagarjuna
- V.S.N. Venkata Ramana
- V. V. Bhanu Prasad
- V. V. Satyanarayana
- K. Kishore
- V. S. M. Ramakrishna R.
- Jai Prakash Gautam
- P. Masthanaiah
- K. Bhanu Sankara Rao
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Madhusudhan Reddy, G.
- Studies on Partially Melted Zone and Pitting Corrosion Resistance of A356 Aluminium-Silicon Alloy GTA Welds
Authors
1 Department of Metallurgical Engineering, Government Polytechnic, Visakhapatnam-530 007, IN
2 Metal Joining Group, Defence Metallurgical Research Laboratory, Hyderabad-500 058, IN
3 Department of Metallurgical Engineering, Andhra University College of Engineering(A), Visakhapatnam-530 003, IN
Source
Indian Welding Journal, Vol 47, No 1 (2014), Pagination: 27-42Abstract
Gas Tungsten Arc Welding (GTAW) of Pressure Die cast A356 Al-Si alloy with strontium modification was done both with and without filler. The microstructural changes in Weld metal zone (WM), Heat affected zone (HAZ) and Partially Melted Zone (PMZ) were studied. PMZ of aluminium alloy weld is an important region, as it is the weak link in the weldments. It is significantly affected by the welding parameters, filler metal and prior thermal condition. In the present work affect of welding techniques i.e. Continuous Current Gas Tungsten Arc Welding (CCGTAW) and pulsed Current Gas Tungsten Arc Welding (PCGTAW) on microstructure and pitting corrosion resistance of weld metal, Partially melted zone and Heat affected zone in the prior conditions of as cast and T6 conditions were studied. Susceptibility to liquation was found to be less in the weld made in as cast condition of pulsed current GTA welds compared to that of artificially aged condition (T6) of continuous current GTA welds. This was mainly attributed to the silicon enrichment of eutectics at the grain boundaries. Potentiodynamic polarization testing was carried out to study the pitting corrosion behavior of the welds. Pitting corrosion resistance of weld made with pulsed current GTAW of as cast alloy is better than the that of weld made with continuous current GTAW of T6 alloy. This is mainly attributed to the discontinuous eutectic formation at the grain boundary base metal and PMZ.Keywords
Aluminium Alloys, GTA Welds, Partially Melted Zone, Continuous Current Gas Tungsten Arc Welding, Pulsed Current Gas Tungsten Arc Welding.
- Effect of Welding Process on Microstructure and Pitting Corrosion Behavior of AA2014 Al-Cu Alloy Welds
Authors
1 Department of Mechanical Engineering, GITAM Institute of Technology, GITAM University, Visakhapatnam - 530045, IN
2 Department of Metallurgical Engineering, Government Polytechnic, Visakhapatnam - 530 007, IN
3 Metal Joining Group, Defence Metallurgical Research Laboratory, Hyderabad - 500 058, IN
4 Department of Metallurgical Engineering, Andhra University College of Engineering (A), Visakhapatnam- 530 003, IN
Source
Indian Welding Journal, Vol 45, No 3 (2012), Pagination: 29-40Abstract
Wrought AA 2014 Al-Cu alloy in mill annealed (O) condition and naturally aged (T4) condition was welded by the Gas Tungsten Arc Welding (GTAW) and Friction Stir Welding (FSW) processes. The microstructural changes and pitting corrosion behaviour in all zones of welds for both the welding processes have been investigated when the alloy was welded in O as well as in T4 conditions. It was observed that naturally aged (T4) alloy weld exhibited better corrosion properties than annealed (O) alloy weld this is attributed to the precipitation of fine grained eutectics in T4 alloy during welding. The pitting corrosion resistance was found to be better and uniform through out cross section of the friction stir welds compared to GTA welds, indicating improvement in corrosion properties of the welds in solid state welding.Keywords
Gas Tungsten Arc Welding, Friction Stir Welding, AA2014 Alloy, Partially Melted Zone, Thermomechanically Affected Zone, Pitting Corrosion, Potentiodynamic Polarization.- Corrosion Resistance of Friction Stir Welded AA6061 Aluminium Alloy
Authors
1 Department of Metallurgical Engineering, Government Polytechnic, Visakhapatnam, IN
2 Defence Metallurgical Research Laboratory, Hyderabad, IN
3 Department of Metallurgical Engineering, Andhra University College of Engineering (A), Visakhapatnam-530 003, IN
Source
Indian Welding Journal, Vol 45, No 3 (2012), Pagination: 41-53Abstract
Present work pertains to microstructure and the corrosion behaviour of the nugget zone (NZ), thermo mechanically affected zone (TMAZ) and heat affected zone (HAZ) of friction stir welded AA6061 alloy. An attempt was made to find the influence of prior thermal temper of the alloy. Potentio-dynamic polarisation testing was used to determine the pitting corrosion resistance of the welds. Optical microscopy (OM) and transmission electron microscopy (TEM) with Energy dispersive X-ray spectroscopy studies were carried out to find the mechanism of formation of TMAZ and corrosion. Friction stir welding of this alloy resulted in fine recrystallized grains in weld nugget which has been attributed to frictional heating and plastic flow. The process also produced a softened region in the weld nugget, which may be due to the dissolution and growth of possible precipitates. Corrosion resistance of nugget zone has been found to be higher than that of TMAZ and base metal. Corrosion resistance of naturally aged (T4) alloy exhibit higher corrosion resistance than that of artificial aged (T6) alloy.Keywords
Pitting Corrosion, General Corrosion, Dynamic Polarisation, Friction Stir Welding, Aluminium Alloys.- Dissimilar Metal Gas Tungsten Arc Weldments of Maraging Steel and Medium Alloy Medium Carbon Steel – Effect of Post-Weld Heat Treatments
Authors
1 Mahatma Gandhi Institute of Technology, Gandipet, Hyderabad – 500 075, IN
2 Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad – 500 058, IN
Source
Indian Welding Journal, Vol 45, No 1 (2012), Pagination: 45-56Abstract
Maraging steel and medium alloy medium carbon steels exhibit their best mechanical properties such as tensile strength and toughness in their respective heat treatment conditions. Gas tungsten arc welding of maraging steel and medium alloy medium carbon steel was carried out taking both the steels in soft annealed condition. Later the weldments were subjected independently to two post-weld heat treatments, one corresponding to the maraging steel i.e. solutionising at 815°C/1 hr/air cooled&aging at 480°C/3 hrs/air cooled, and the other corresponding to medium alloy medium carbon steel i.e. quenching at 925°C/35 min/air cooled&tempering at 295°C/45 min/air cooled. The effect of post-weld heat treatments on the microstructure and mechanical properties such as hardness, tensile strength and impact toughness of the dissimilar metal welds of maraging steel and medium alloy medium carbon steel was investigated. The influence of filler materials was also studied by employing maraging steel and medium alloy medium carbon steel fillers. Maraging steel welds responded to the solutionising and aging treatment whereas the medium alloy medium carbon steel welds responded to quenching and tempering. Lowering of the hardness was observed at the interaction of maraging steel and medium alloy medium carbon steel due to the diffusion of manganese. Medium alloy medium carbon steel filler welds showed good strength and toughness properties.Keywords
Maraging Steel, Medium Alloy Medium Carbon Steel, Gas Tungsten Arc Welding and Post-Weld Heat Treatment.- The Influence of Electrode Polarity and Welding Current on Mechanical Properties of Submerged Arc Weld (SAW) in C-Mn Steels
Authors
1 Defence Metallugical Research Laboratory, Hydrabad 500 258, IN
2 Welding Research Laboratory, University of Roorkee, Roorkee, IN
Source
Indian Welding Journal, Vol 26, No 3 (1993), Pagination: 1-4Abstract
An experimental study has been carried to study the effect of electrode polarity and welding current on mechanical properties of multipass SAW welds made by using C-Mn filler wire and basic flux. Weld deposits were characterised on the basis of tensile properties, hardness and charpy impact toughness Hardness survey of the weld revealed that higher hardness occured in the coarse microstructural region than the reheat refined region. For a given polarity there was an improvement in weld impact toughness as the current decreased from 700 A to 500 A. However the trend was reverse for tensile to be better for DCEP compared to DCEN.- Weldability Aspects of Ferritic Stainless Steels
Authors
1 Defence Metallurgical Research Laboratory, Hyderabad, IN
Source
Indian Welding Journal, Vol 27, No 2 (1994), Pagination: 7-15Abstract
Ferritic stainless steels have recently drawn greater attention owing to their lower costs and better resistance to stress corrosion cracking than austenitic stainless steels. Although these properties make the alloy commercially attractive they still exhibit several significant draw backs that limit their use Ferritic stainless steels are less weldable than austenitic ones. A pronounced grain growth takes place in the heat affected zone and carbide precipitation occur at the grain boundaries. This makes the weld more brittle and decreases its corrosion resistance Furthermore cracks can occur in the weld metal when it cools down.
When welding stainless steels care must be taken that welding process does not affect either the corrosion resistance of the weldment or its mechanical properties. This article covers what effects the welding process can have on the metallurgy of ferritic stainless steels, selection of consumable and suggests practical advice on how potential problems can overcome
- Effect of Weld Parameters on Residual Stress Distribution in Flux Cored Arc Welding of High Strength Low Alloy Steel
Authors
1 Defence Metallurgical Research Laboratory, Hyderabad, IN
Source
Indian Welding Journal, Vol 27, No 2 (1994), Pagination: 25-30Abstract
Various types of high strength steels are increasingly used for producing welded structures with reduced weight and improved performance. Welding problems related to residual stress and distortion can arise, since yield stress of these steels are high, there is always a possibility of producing very high residual stresses in some locations near the weld. In general residual stresses become dangerous if they lead to local multi axiallity of tension stresses, which favour brittle fracture, knowledge of the residual- stress distribution in welds is necessary in order to assess the risk of crack growth in service The distribution of residual stresses after welding depends strongly on the weld parameters Attempts were made to study the influence of weld parameters (arc voltage, travel speed, welding current) on residual stresses pattern of high strength low alloy steel weldments This study was mainly performed by using X-ray stress analyzer.- The Influence of Electrode Polarity and Welding Current on Mechanical Properties of Submerged Arc Weld
Authors
1 Defence Metallurgical Research Laboratory, Hyderabad - 258, IN
2 Welding Research Laboratory, University of Roorkee, Roorkee, IN
Source
Indian Welding Journal, Vol 23, No 3 (1991), Pagination: 145-150Abstract
An experimental study has been made on the effect of electrode polarity on macrostruclure and mechanical properties of multipass submerged arc welds. The influence of welding current with two polarities has been studied. The welds are made by using C-Mn filler wire and basic flux. Weld deposites were characterised on the basis of tensile properties, hardness measurements and charpy impact toughness. The study of macro structure of weld deposites shows that the amount of reheat refined weldmetal increases with decreasing welding current with DCEP than that observed with DCEN. Hardness survey on the transverse section along the vertical line of the weld deposite revealed that higher hardness occured in the coarse micro structural region than the reheat refined region of the weld deposite. The charpy V-notch impact results show better toughness in the welds deposited at lower level of current with DCEP than that observed at DCEN. Yield strength and ultimate tensile strength are higher with DCEN than that observed in case of DCEP.- Microstructure and Mechanical Properties of Explosive Weld Copper-Mild Steel Joint
Authors
1 Defence Metallurgical Research Laboratory, P.O. Kanchanbagh, Hyderabad-58, IN
Source
Indian Welding Journal, Vol 51, No 1 (2018), Pagination: 50-57Abstract
Mild steel and copper was joined with explosive welding using suitable parameters to obtain a copper-mild steel joint of high integrity. There was no diffusion, melting and formation of intermetallic zone between the bonded plates. An inter-mixed zone of the base materials is observed with a span of 1300 μm around the interface. Significant hardening and softening of the microstructure was observed on the copper and steel sides around the interface respectively by inter-mixing effect arising out of mechanical inter-locking. Shear strength of the joint (260 MPa) was quite higher with respect to that of the copper, the weaker metal of the copper-mild steel bimetal combination. Reasonably ductile shear failure occurred in the copper plate, and no failure was observed along the interface.Keywords
Mild Steel, Copper, Explosive Weld Interface, Inter-Mixed Zone, Shear Strength.References
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- Microstructure, Mechanical and Corrosion Behaviour of AA7075 Aluminium Alloy Friction Stir Welds
Authors
1 Department of Mechanical Engineering, Raghu Institute of Technology, Visakhapatnam, IN
2 Defence Metallurgical Research Laboratory, Hyderabad, IN
3 Department of Metallurgical Engineering, Andhra University, Visakhapatnam, IN
Source
Indian Welding Journal, Vol 51, No 2 (2018), Pagination: 66-74Abstract
Friction stir welding (FSW) is emerging as an alternative technique for joining high strength aluminium alloys as it eliminates the problems during fusion welding. In this work, the effect of post weld treatments (PWHT), viz., peak aging (T6) and retrogression and reaging (RRA) on the microstructure, mechanical properties, pitting corrosion and stress corrosion cracking (SCC) resistance of AA7075 aluminium alloy friction stir welds has been studied. An attempt also has been made to change the chemical composition of the weld nugget by adding boron carbide (B4C) nano powder with the aid of the FSW. Hardness and tensile properties were found to be better in PWHT – T6. Pitting corrosion and SCC resistances were improved in PWHT-RRA condition with negligible loss of strength when compared to PWHT-T6. RRA promotes coarse precipitation of the equilibrium phase η in the grains and sub grain boundaries, while maintaining a fine distribution of η' in the grain interiors. The increased strength and hardness in the peak aged (T6) condition was attributed to the presence of semi-coherent intermediate η' (MgZn2). With the addition of B4C nano powder to the weld nugget, hardness, tensile properties, pitting corrosion resistance and SCC resistance were further improved significantly when compared to the unreinforced weld nugget. PWHT-RRA treatment on the welds with B4C nano powder addition resulted in improved hardness of weld nugget which is attributed to the uniform distribution of strengthening precipitates in the matrix and powder strengthening. Pitting corrosion resistance, Tensile strength and SCC resistance was improved significantly in B4C added welds after RRA treatment when compared to the same welds without B4C addition.Keywords
Friction Stir Welding, FSW, AA7075 Aluminium Alloy, Pitting Corrosion, Stress Corrosion Cracking, Retrogression-Reaging, RRA, Boron Carbide (B4C).References
- Sharma C, Dwivedi DK, Kumar P (2012); Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of AA7039 aluminum alloy, Mater Des, 36, pp.379-390.
- Paglia CS, Buchheit RG (2008); A look in the corrosion of aluminum alloy Friction stir welds, Scr Mater, 58, pp.383-387.
- Karaaslan A, Kaya I, Atapek H (2007); Effect of aging temperature and of retrogression treatment time on the microstructure and mechanical properties of alloy AA 7075, Metal Sci Heat Treat, 49, pp.9-10.
- Venugopal T, Srinivasa Rao K, Prasad Rao K (2004); Studies on friction stir welded AA7075 aluminum alloy. Trans Indian Inst Metals, 57 (6), pp.659-663.
- Rao K Srinivasa, Rao K Prasad. (2004); Pitting corrosion of heat-treatable aluminium alloys and welds: a review, Trans Indian Inst Met, 57 (6), pp.593-610.
- Ranganatha R (2013); Multi-stage heat treatment of aluminum alloy AA7049. Trans Nonferrous Met Soc China, pp.1570-1575.
- Su JQ, Nelson TW, Mishra R, Mahoney M (2003); Microstructural investigation of friction stir welded 7050- T651 aluminium, Acta Mater, 51(3), pp.713-729.
- Hassan KhAA, Norma AF, Price DA, Prangnell PB (2003); Stability of nugget zone grain structures in high strength Al-alloy friction stir welds during solution treatment. Acta Mater, 51 (7), pp.1923-1936.
- Sullivan A, Robson JD (2008); Microstructural properties of friction stir welded and post weld heated 7449 aluminum alloy thick plate. Mater Sci Eng (A), 478, pp.351-360.
- Oliveira Jr AF, de Barros MC, Cardoso KR, Travessa DN (2004); The effect of RRA on the strength and SCC resistance on AA7050 and AA7150 aluminum alloys, Mater Sci Eng, 379 (A), pp.321-326.
- Fuller CB, Mahoney MW, Calabrese M (2010); Evolution of microstructure and mechanical properties in naturally aged 7050 and 7075 Al friction stir welds, Mater Sci Eng, 527 (9), pp.2233-2240.
- Bahrami M, Dehgani K, Givi MKB (2014); A novel approach to develop aluminum matrix nano composite employing friction stir welding technique, Mater Des, 53, pp.217-225.
- Azimzadegan T, Khalaj GH, Kaykha MM. Heidari AR (2011); Ageing behavior of friction stir welding AA7075-T6 aluminum alloy, Comput Eng Syst Appl ,Vol. II, pp.183-187.
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- Kashani-Bozorg SF, Jazayeri K (2008); Formation of Al/B4C surface nano composite layers on 7075 Al alloy 4 employing friction stir processing. AIP Conf Proc, 1136 (1), pp.715-719.
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- Characterization of Clad Joints of High Strength Low Alloy Steel with Stainless Steel and Titanium
Authors
1 Defence Metallurgical Research Laboratory, Kanchanbagh PO, Hyderabad-500058, IN
Source
Indian Welding Journal, Vol 51, No 4 (2018), Pagination: 46-56Abstract
In the present investigation, a study has been carried out to understand the structure-property correlations in explosive clad joints of high strength low alloy steel (Yield Strength >600 MPa) in as-clad, hot rolled and heat treated conditions. The cladding materials employed were austenitic stainless steel of AISI 347 grade and commercial pure (CP) titanium. An attempt has also been made to realise the structure-property correlations in the clad joint of the HSLA steel with AISI 347 grade austenitic stainless steel produced by weld overlay cladding technique. In explosive cladding, the interface was found to be wavy type and in weld overlay cladding, the interface was flat. Explosive clad joints of HSLA steel + austenitic stainless steel exhibited a bond strength of 491 MPa in as-clad condition and 408 MPa after hot rolling and heat treatment. Explosive clad joint of HSLA steel + CP titanium exhibited a bond strength of 356 MPa in as-clad condition as CP titanium possesses lower strength (337 MPa) compared to that of AISI 347 grade austenitic stainless steel (515 MPa). The weld overlay clad joint exhibited a bond strength of 488 MPa which is almost equal to that of explosive clad joint in as-clad condition. The clad joints of austenitic stainless steel and CP titanium, with the base plate in heat treated condition, exhibited good formability when three point bend tests were conducted upto 114º and 139º respectively.Keywords
Explosive Cladding, Weld Overlay Cladding, Hsla Steel, Stainless Steel, Microstructure, Shear Bond Strength.References
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- Kamachi MU, Ananda Rao B M, Shanmugam K, Natarajan R and Baldev Raj (2003); Corrosion and microstructural aspects of dissimilar joints of titanium and type 304L stainless steel, Journal of Nuclear Materials, 321, pp. 40-48.
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- A Comparison Between Microstructure, Tensile Properties and Pitting Corrosion Resistance of Friction Stir and Gas Tungsten Arc Ferritic Stainless Steel Welds
Authors
1 Defence Metallurgical Research Laboratory, Hyderabad, 500 058, IN
2 Department of Metallurgical Engineering, A. U. College of Engineering (A), Visakhapatnam - 530 003, IN
Source
Indian Welding Journal, Vol 46, No 4 (2013), Pagination: 59-64Abstract
In the present work an attempt was made to study the pitting corrosion susceptibility of AISI 430 ferritic stainless steel welds. Gas tungsten arc (GTA) welding and friction stir welding (FSW) processes were used to make welds. Potentio-dynamic polarization test was used to evaluate pitting corrosion resistance of the welds. Optical and electron microprobe analysis were used to study the microstructure and corrosion mechanism respectively. It was observed that the weld microstructure of GTA weld was predominately columnar. Friction stir weld exhibited fine equiaxed grain structure. Investigations clearly revealed that pitting corrosion resistance of friction stir weld zone was inferior compared to GTA weld in which breakdown potential was reduced by chrornium depletion. This was due to enhanced formation of intermetallic phase in friction stir welds compared to GTA welds. This was attributed to the slower cooling rate of friction stir welds, which results in longer exposure to the temperature range for precipitation during cooling cycle. Fine grain structure of friction stir weld has resulted in greater chromium depleted area than that of weld zone of GTA weld. In addition to the above, lower pitting corrosion resistance of friction stir welds was correlated to the formation of strain induced martensite in the nugget zone. Presence of residual stresses was also found to be affecting localized corrosion resistance by increasing number of active anode sites on the surface.
Keywords
Piiting Corrosion, Ferritic Stainless Steel, Welding, Microstructure, Sensitization.- Partially Melted Zone in Dissimilar Aluminium Alloy Welds-Effect of Prior Thermal Temper and Welding Process
Authors
1 Department of Mechanical Engg., PVP Siddhartha Institute of Technology, Vijayawada-520007, IN
2 Defence Metallurgical Research Laboratory, Hyderabad-500 058, IN
3 Department of Metallurgical Engineering, Andhra University College of Engineering(A), Visakhapatnam - 530 003, IN
Source
Indian Welding Journal, Vol 43, No 2 (2010), Pagination: 32-40Abstract
Partially melted zone (PMZ) of aluminium alloy welds is an important region and requires careful attention. This is mainly because PMZ in these alloys is a weak link in the weldments and is significantly affected by welding parameters. Microstructural changes in PMZ are related not only to welding heat input and processes, but also depend on the initial thermal history of the alloy (for example, whether it is in O, T4, T6 orT87 condition etc.). Interestingly not many detailed studies are available in this respect. In the present work effect of prior thermal temper and welding process on the PMZ behaviour of dissimilar AA2014 and AA6061 alloy GTA and EB welds were studied. Grain coarsening and melting in PMZ is more when the alloys are welded in T4 temper than in O condition and AA2014 alloy is prone for liquation compared to AA6061 alloy which attributes high alloying element concentration in AA2014 side of the joint. EB welding proved to be efficient welding process compared to GTA welding in terms of resistance to liquation and better mechanical properties.
Keywords
Partially Melted Zone, Gas Tungsten Arc Welding, Electron Beam Welding, Dissimilar Alloy Welds.- Friction Welding Studies on SiCp Reinforced Aluminium Alloy AA 2124 Metal Matrix Compositie
Authors
1 Defence Metallugical Research Laboratory, Kanchanbagh, Hyderbad - 500 058, IN
Source
Indian Welding Journal, Vol 43, No 3 (2010), Pagination: 43-50Abstract
Continuous drive friction welding studies were carried out on AA 2124 SiCp metal matrix particulate composite. Taguchi technique was employed to select the best combination of friction welding parameters. Studied the influence of main friction welding process parameters such as friction force, forge force and burn off on tensile properties. Low friction force, high forge force and high burn-off yielded maximum tensile strength. Friction welds of metal matrix composite with higher volume fraction of SiCp yielded high tensile strength. It was observed that tensile strength of the welds were stronger than the corresponding parent material. The higher tensile strength of the welds is thought to be due to the break down of the reinforcement particle.
- Robust Design of Dissimilar Stainless Steel Joining
Authors
1 IIW Defense Metallurgical Research Laboratory, Hyderabad, IN
2 IIW
3 Department of Mechanical Engineering, Vasavi College of Engineering, Ibrahimbagh, Hyderabad, IN
Source
Indian Welding Journal, Vol 41, No 4 (2008), Pagination: 38-42Abstract
Robustness is a key strategy for achieving high quality. There were different approaches to robust design namely inner-outer array approach advocated by Taguchi, the dual response approach using response surfaces and the tolerance analysis approach which is also through response surfaces.
This paper reports on a study that has been taken up to develop the robust design by dual response and tolerance analysis approaches for understanding the friction welding characteristics of austenitic stainless steel - ferritic stainless steel dissimilar metal welds.
Keywords
Austenitic Stainless Steel, Ferritic Stainless Steel, Friction Weld, Robust, Taguchi Method.- Grain Refinement in Ferritic Stainless Steel Welds Through Magnetic Arc Oscillation and Its Effect on Tensile Property
Authors
1 Defence Metallurgical Research Laboratory, Hyderabad-58, IN
Source
Indian Welding Journal, Vol 39, No 3 (2006), Pagination: 35-41Abstract
Grain size reduction in weld fusion zone confers the advantage of increased resistance to solidification cracking and improved mechanical properties. In an effort to refine the fusion zone grain structure in AISI 430 ferritic stainless steel, Gas tungsten arc welding (GTAW) was performed during which transverse oscillations of the arc were induced through the use of an alternating external magnetic field. It was observed that the structure in the as - soIidified weld was predominantly columnar in the case of the conventional (i.e. continuous current) gas tungsten arc welding process. Arc oscillation results in columnar to equiaxed transition in the grain structure; under optimum condition of arc oscillation frequency and amplitude, the grain size of the weld bead was finer than in conventional welds. This could be attributed to the factors that include enhanced fluid flow, reduced temperature gradients and continually changing weld pool size and shape due to the action of the imposed magnetic field. An oscillation variable, which resulted in maximum grain refinement in the fusion zone, was employed to evaluate longitudinal all-weld tensile properties, and residual stresses across weldments. The tensile properties of arc oscillation welds were found to be superior to those of conventional welds. Arc oscillated welds exhibited low tensile residual stresses in the fusion zone compared to conventional gas tungsten arc welds.
- Solidification Cracking Studies on Steels
Authors
1 Defence Metallurgical Research Laboratory, Hyderabad - 500058, IN
Source
Indian Welding Journal, Vol 34, No 3 (2001), Pagination: 13-19Abstract
Three steels namely, Cr-Mo steel equivalent to 4130, modified 4340 steel Containing higher silicon and high nickel whose strength is equivalent to maraging steel 250 and a maraging steel have been studied for their solidification cracking behaviour during continuous current gas tungsten arc welding employing varestraint test system. The Cr-Mo steel was also subjected to pulse mode of gas tungsten arc welding to understand the influence of current pulsing on solidification cracking behaviour. Cr-Mo steel exhibited least solidification cracking tendency while modified 4340 steel (silicon steel) showed marginally higher cracking tendency than the maraging steel. Cr-Mo steel exhibited a greater tendency to cracking in pulsed mode of welding than in conventional welding. The observed cracking tendency of cracking in pulsed mode of welding is explained on the basis of possible differences in the weld thermal history between conventional welds and pulsed welds.
Keywords
Solidification Cracking, Cr-Mo Steel, Maraging Steel, Ultra High Strength Steel, Varestraint Test, Houldcroft Test, Tekken Test.- Laser Welding of Ultrafine Bainitic Steels
Authors
1 Mahatma Gandhi Institute of Technology, Gandipet, Hyderabad - 500 075, IN
2 School of Engineering Sciences and Technology, University of Hyderabad - 500 046, IN
3 Defence Metallurgical Research Laboratory, Hyderabad - 500 058, IN
4 Defence Research Development Laboratories, Hyderabad - 500 058, IN
5 Ministry of Steel Chair Professor, MGIT, Hyderabad - 500 075, IN
Source
Indian Welding Journal, Vol 52, No 3 (2019), Pagination: 52-56Abstract
Laser beam welding (LBW) is one of the advanced welding process which results in joining of materials with intense heat. The intense heat is produced using focused light source falling upon the metallic material’s surfaces to be welded. The coherent laser beam is a known source of electromagnetic energy or light with single frequency which can be projected without diverging and also can be focused to an exact spot. The current investigation aims at establishing the parameters required for producing sound welds by fibre laser beam welding and identifying the evolution of microstructure in bainitic steel during similar welding of three mm thick plates. Sound welding was accomplished with laser power 3.5kW and at traverse speeds of 2000, 3000 and 4000 mm/min. The weld joints revealed base metal, weld zone and heat affected zones. The widths of weld zone and HAZ varied as a function of welding speed. Weld zone displayed hardness around 750-800 VHN. A sudden drop in hardness was observed across the heat affected zone, reaching a dip in the intercritical region of HAZ. Hardness in ICHAZ reached around 400-450VHN. The ICHAZ was more pronounced at 3000 mm/min. Microstructural changes were explored by optical microscopy techniques. The high hardness in fusion zone and low hardness in the intercritical structure was found to have correlation with prevailing microstructural features in the respective zones.
Keywords
Bainitic Steel, Fibre Laser Welding, Fusion Zone, Heat Affected Zone, Intercritical Structure, Hardness.References
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