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Cold Cracking of Flux Cored Arc Welded Armour grade High Strength Steel Weldments

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Journal of Materials Science & Technology 2009年第4期25卷 516-526页

作者： g.Magudeeswaran v.Balasubramanian g.Madhusudhan reddy Metal Joining Research Center(MJRC) Sri Ramakrishna Engineering College Centre for Materials Joining & Research(CEMAJOR) Department of Manufacturing EngineeringAnnamalai University Metal Joining Section Defence Metallurgical Research Laboratory(DMRL)

In this investigation, an attempt has been made to study the influence of welding consumables on the factors that influence cold cracking of armour grade quenched and tempered （Q＆.T） steel welds. Flux cored arc welding （FCAW） process were used making welds using austenitic stainless steel （ASS） and low hydrogen ferritic steel （LHF） consumables. The diffusible hydrogen levels in the weld metal of the ASS and LHF consumables were determined by mercury method. Residual stresses were evaluated using X-ray stress analyzer and implant test was carried out to study the cold cracking of the welds. Results indicate that ASS welds offer a greater resistance to cold cracking of armour grade Q＆T steel welds.

关键词： Quenched and tempered steel Flux cored arc welding process Weld cold cracking Implant testing

Effect of Hardfaced Interlayer Thickness and Low Hydrogen Ferritic Capping on Ballistic Performance of Shielded Metal Arc Welded Armour Steel Joints

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Journal of Iron and Steel Research International 2013年第12期20卷 82-91页

作者： M Balakrishnan v Balasubramanian g Madhusudhan reddy Center for Materials Joining and Research(CEMAJOR) Department of Manufacturing EngineeringAnnamalai University Solidification Technology Division Metal Joining GroupDefense Metallurgical Research Laboratory(DMRL)

Armour grade quenched and tempered steel closely confirming to AISI 4340 is well known for its superior ballistic performance and hence used in the fabrication of combat vehicles. The traditional fillers like austenitic stain- less steel showed poor ballistic performance of these welded joints as compared to the base metal. Attempts have been made to deposit hardfaced interlayer between austenitic stainless steel weld metals. Though this method, mar-- ginal improvements in ballistic performance can be yielded, and cracks were observed in between base metal and hardfaced layer. Thickness of the hardfaced interlayer plays a vital role for the effective ballistic performance. Thus, an attempt has been made to investigate the effect of hardfaced interlayer thickness on ballistic performance of ar- mour steel welds. The results of effect of buttering, low hydrogen ferritic （LHF） filler and three different hardfaced layer thicknesses （4, 5.5 and 7 ram） on ballistid performance of shielded metal arc welded armour steel joints were given.

关键词： armour steel low hydrogen ferritic electrode sandwich structure ballistic performance hardfacing metallography

Experimental Investigation on the Performance of Armour grade Q&T Steel Joints Fabricated by Flux Cored Arc Welding with Low Hydrogen Ferritic Consumables

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Journal of Materials Science & Technology 2009年第5期25卷 583-591页

作者： g.Magudeeswaran v.Balasubramanian g.Madhusudhan reddy g.gopalakrishnan Metal Joining Research Center(MJRC) Sri Ramakrishna Engineering CollegeN.G.G.O Colony-Post Centre for Materials Joining&Research(CEMAJOR) Department of Manufacturing EngineeringAnnamalai University Scientist-F Metal Joining SectionDefence Metallurgical Research Laboratory(DMRL)Kanchanbagh(P.O)

Quenched and Tempered （Q＆T） steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking （HIC） and softening in the heat affected zone （HAZ） after welding. The use of austenitic stainless steel （ASS） consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic （LHF） steel consumables can also be used to weld Q＆T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q＆T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely （i） austenitic stainless steel and （ii） low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding （FCAW） process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone （CgHAZ） is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.

关键词： Quenched and tempered steel Flux cored arc welding process Low hydrogen ferritic steel Tensile properties

Metallurgical characteristics of armour steel welded joints used for combat vehicle construction

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Defence Technology（防务技术） 2018年第5期14卷 590-606页

作者： g.Magudeeswaran v.Balasubramanian g.Madhusudan reddy Department of Mechanical Engineering PSNA College of Engineering and TechnologyKothandaraman NagarMuthanampatti624 622DindigulTamilnaduIndia Centre for Materials Joining&Research Department of Manufacturing EngineeringAnnamalai UniversityAnnamalai Nagar608002Tamil NaduIndia Outstanding Scientist & Associate Director Defence Metallurgical Research LaboratoryKanchanbaghHyderabad500058TelanganaIndia

Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced cracking(HIC) but they are very expensive. In recent years, the developments of low hydrogen ferritic steel(LHF) consumables that contain no hygroscopic compounds are utilized for welding Q&T steels. Heat affected zone(HAZ) softening is another critical issue during welding of armour grade Q&T steels and it depends on the welding process employed and the weld thermal cycle. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on metallurgical characteristics of armour grade Q&T steel joints by various metallurgical characterization procedures. Shielded metal arc welding(SMAW) and flux cored arc welding(FCAW) processes were used for making welds using ASS, LHF and HNS welding consumables. The joints fabricated by using LHF consumables offered lower degree of HAZ softening and there is no evidence of HIC in the joints fabricated using LHF consumables.

关键词： Armour grade Q&T steel Heat affected zone softening Shielded metal arc welding process Flux cored arc welding process Austenitic stainless steel Low hydrogen ferritic steel High nickel steel

Effect of Welding Processes and Consumables on Tensile and Impact Properties of High Strength Quenched and Tempered Steel Joints

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Journal of Iron and Steel Research International 2008年第6期15卷 87-94页

作者： g Magudeeswaran v Balasubramanian g Madhusudhan reddy T S Balasubramanian Center for Advanced Materials Joining and Research(CEMAJOR) Department of Manufacturing EngineeringAnnamalai University Metal Joining Section Defence MetallurgicalResearch Laboratory Special vehicles Division Combat Vehicles Research and Development Establishment

Quenched and tempered steels are prone to hydrogen induced cracking in the heat affected zone after welding. The use of austenitic stainless steel consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. In this investigation, an attempt was made to determine a suitable consumable to replace expensive austenitic consumables. Two different consumables, namely, austenitie stain less steel and low hydrogen ferritic steel, were used to fabricate the joints by shielded metal are welding （SMAW） and flux cored arc welding （FCAW） processes. The joints fabricated by using low hydrogen ferritic steel consumables showed superior transverse tensile properties, whereas joints fabricated by using austenitic stainless steel consumables exhibited better impact toughness, irrespective of the welding process used. The SMAW joints exhibited superior mechanical and impact properties, irrespective of the consumables used, than their FCAW counterparts.

关键词： shielded metal arc welding process flux cored arc welding process austenitie stainless steel low hydro gen ferritic steel transverse tensile property impact toughness

ZrB_(2)-SiC based composites for thermal protection by reaction sintering of ZrO_(2)+B_(4)C+Si

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Journal of Advanced Ceramics 2017年第4期6卷 320-329页

作者： R.v.KRISHNARAO v.v.BHANUPRASAD g.MADHUSUDHAN reddy Defence Metallurgical Research Laboratory KanchanbaghHyderabad-500058India

Synthesis and sintering of ZrB_(2)-SiC based composites have been carried out in a single-step pressureless reaction sintering(PLRS)of ZrO_(2),B_(4)C,and Si.Y_(2)O_(3) and Al_(2)O_(3) were used as sintering *** effect of ratios of ZrO_(2)/B_(4)C,ZrO_(2)/Si,and sintering additives(Y_(2)O_(3) and Al_(2)O_(3)),was studied by sintering at different temperatures between 1500 and 1680℃in argon ***_(2),SiC,and YAg phases were identified in the sintered *** as high as 4.2 g/cm^(3),micro hardness of 12.7 gPa,and flexural strength of 117.6 MPa were obtained for PLRS *** material was also prepared by PLRS for tungsten inert gas(TIg)welding of the ZrB_(2)-SiC based *** shear strength of the weld was 63.5 *** PLRS ZrB_(2)-SiC composites exhibited:(i)resistance to oxidation and thermal shock upon exposure to plasma flame at 2700℃for 600 s,(ii)thermal protection for Cf-SiC composites upon exposure to oxy-propane flame at 2300℃for 600 s.

关键词： ZrB_(2) SiC reactive sintering synthesis composites

Joining and machining of(ZrB2-SiC)and(Cf-SiC)based composites

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Defence Technology（防务技术） 2018年第5期14卷 385-395页

作者： R.v.Krishnarao g.Madhusudan reddy v.v.Bhanuprasad Defence Metallurgical Research Laboratory KanchanbaghHyderabad500058India

Filler materials of(ZrB_2-SiC-B_4C-YAg) composite were developed for gas tungsten arc welding(gTAW) of the ZrB_2-SiC and Cf-SiC based composites to themselves and to each other. Reaction with filler material,porosity and cracks were not observed at weld interfaces of all the joints. Penetration of filler material in to voids and pores existing in the Cf-SiC composites was observed. Average shear strength of 25.7 MPa was achieved for joints of Cf-SiC composites. By incorporation of Cf-SiC(CvD) ground short fibre reinforcement the(ZrB_2-SiC-B_4C-YAg) composite was machinable with tungsten carbide tool. The joint and machined composites were resistance to oxidation and thermal shock when exposed to the oxy-propane flame at 2300℃ for 300s. The combination of(ZrB_2-SiC-B_4C-YAg) and Cf-SiC based composites can be used for making parts like thermal protection system or nozzles for high temperature applications.

关键词： ZrB2-SiC Composite Sintering Machining gas tungsten arc welding

Microstructure and mechanical properties of similar and dissimilar metal gas tungsten constricted arc welds:Maraging steel to 13-8 Mo stainless steel

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Defence Technology（防务技术） 2019年第1期15卷 111-121页

作者： C.v.S.Murthy A.gopala Krishna g.M.reddy Defence Research and Development Laboratory Jawaharlal Nehru Technological University Defence Metallurgical Research Laboratory

Maraging steel (250) and 13-8 Mo stainless steel plates were joined by gas tungsten constricted arc welding(gTCAW) process in similar and dissimilar metal combinations using 13-8 Mo stainless steel filler wire. The similar and dissimilar metal welds made in solutionized condition were subjected to standard post weld hardening treatments direct ageing at 485 ℃, soaking for 31/2 hours followed by air cooling(ageing treatment of maraging steel) and direct ageing at 510 ℃, soaking for 4 h followed by air cooling(ageing treatment of 13-8 Mo stainless steel). The joint characterization studies include microstructure examination, microhardness survey across the weldments and transverse weld tensile *** and dissimilar metal weldments responded to both the post weld ageing treatment. After post weld aging, increase in yield strength, UTS and slight reduction in % elongation of similar and dissimilar metal were observed. The observed tensile properties were correlated with microstructure and hardness distribution across the welds.

关键词： Maraging steel(250) 13-8 Mo stainless steel Mechanical properties Microstructure

Electrical transport and current properties of rare-earth dysprosium Schottky electrode on p-type gaN at various annealing temperatures

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Journal of Semiconductors 2017年第11期38卷 39-47页

作者： g.Nagaraju K.Ravindranatha reddy v.Rajagopal reddy Department of Physics Sri Venkateswara University Tirupati-517 502 India Department of Physics SGS Arts College Tirupati-517 502 India

The electrical and current transport properties of rapidly annealed Dy/p-gaN SBD are probed by I-v and C-v techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 ev（I-v）/0.93 ev（C-v） and 0.87 ev（I-v）/1.03 ev（C-v）. However, the BH rises to 0.99 ev（I-v）/1.18 ev（C-v）and then slightly deceases to 0.92 ev（I-v）/1.03 ev（C-v） after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung＇s functions, the series resistance of the SBD is estimated. The BHs estimated by I-v, Cheung＇s and ΨS-v plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-gaN SBD at all annealing temperatures.

关键词： p-gaN rare-earth Dy Schottky contacts annealing effects electrical properties energy distribution profiles carrier transport mechanism