Effect of Hardfacing Consumables on Ballistic Performance of Q&T Steel Joints

This study was carried out to evaluate the effect of hardfacing consumables on ballistic performance of armour grade quenched and tempered(Q&T)steel welded joints.To evaluate the effect of hardfacing consumables,joints were fabricated using 4 mm thick tungsten carbide(WC)/chromium carbide(CrC)hardfaced middle layer;above and below which austenitic stainless steel(SS)layers were deposited on both sides of the hardfaced interlayer.Shielded metal arc welding(SMAW)process were used to deposite all(hardfaced layer and SS layers)layers.The fabricated joints were evaluated for its ballistic performance,and the results were compared with respect to depth of penetration(DOP)on weld metal and heat-affected zone(HAZ)locations.From the ballistic test results,it was observed that both the joints successfully stopped the bullet penetration at weld center line.Of the two joints,the joint made with CrC hardfaced interlayer(CAHA)offered better ballistic resistance at weld metal.This is because its hardness is higher due to the presence of primary carbides of needle shape,polyhedral shape and eutectic matrix containing a mixture of gt M7C3carbides in the CrC hardfaced interlayer.The scattering hardness level in the WC interlayer,the matrix decomposition resulted lower hardness and the co-existence of d ferrite in the interface between hardfacing and SS root/SS cap could be attributed to the inferior ballistic resistance of the joint made with WC hardfaced interlayer(WAHA joint).

Effect of tool pin profile on microstructure and tensile properties of friction stir welded dissimilar AA 6061e AA 5086 aluminium alloy joints

Joints between two different grades of aluminium alloys are need of the hour in many light weight military structures.In this investigation,an attempt has been made to join the heat treatable(AA 6061) and non-heat treatable(AA 5086) aluminium alloys by friction stir welding(FSW)process using three different tool pin profiles like straight cylindrical,taper cylindrical and threaded cylindrical.The microstructures of various regions were observed and analyzed by means of optical and scanning electron microscope.The tensile properties and microhardness were evaluated for the welded joint.From this investigation it is founded that the use of threaded pin profile of tool contributes to better flow of materials between two alloys and the generation of defect free stir zone.It also resulted in higher hardness values of 83 HV in the stir zone and higher tensile strength of 169 MPa compared to other two profiles.The increase in hardness is attributed to the formation of fine grains and intermetallics in the stir zone,and in addition,the reduced size of weaker regions,such as TMAZ and HAZ regions,results in higher tensile properties.

焊接方法对Ti-6Al-4V合金接头微观组织及拉伸和冲击性能的影响(英文)

钛合金由于具有高比强度、优越的耐腐蚀性和出色的耐热性等优良特性,已成功应用于航空航天、造船和化学工业。尽管钛合金具有合适的可焊性特点,但焊接方法极大地影响焊接接头性能。焊接过程中热循环将会影响焊接金属凝固、相转变和微观组织。采用钨电极惰性气体保护焊接(GTAW)、激光束焊接(LBW)和电子束焊接(EBW)方法制备Ti-6Al-4V合金的焊接接头。EBW焊接接头的强度高于GTAW和LBW接头的强度,但GTAW接头较其它两种接头具有较高的断裂韧性。焊接接头的拉伸和冲击性能与焊接金属的微观组织有关。

AZ31B镁合金的脉冲电流气体保护钨极焊过程参数优化(英文)

建立预测脉冲电流气体保护钨极焊AZ31B镁合金接头的拉伸强度经验方程。研究焊接过程参数如峰值电流、基础电流、脉冲频率和脉冲时间对焊接接头的影响。试验设计了一个四因素五水平的正交实验。建立的经验方程能够有效地预测脉冲电流钨电极惰性气体保护焊AZ31B镁合金的焊缝拉伸强度,可信度为95%。结果表明,脉冲频率对拉伸强度的影响最大,其次是峰值电流、脉冲时间和基电流。

Optimization of Friction Welding Process Parameters for Joining Carbon Steel and Stainless Steel

Friction weIding is a solid state joining process used extensively currently owing to its advantages such as low heat input, high production efficiency, ease of manufacture, and environment friendliness. Materials difficult to be welded by fusion welding processes can be successfully welded by friction welding. An attempt was made to develop an empirical relationship to predict the tensile strength of friction welded AISI 1040 grade medium carbon steel and AISI 304 austenitic stainless steel, incorporating the process parameters such as friction pressure, forging pressure, friction time and forging time, which have great influence on strength of the joints. Response surface methodology was applied to optimize the friction welding process parameters to attain maximum tensile strength of the joint. The maximum tensile strength of 543 MPa could be obtained for the joints fabricated under the welding conditions of friction pressure of 90 MPa, forging pressure of 90 MPa, friction time of 6 s and forging time of 6 s.

搅拌头倾斜角对搅拌摩擦焊AA2014-T6铝合金焊接接头强度和显微组织的影响（英文）

结合各种焊接参数,包括焊接速度、转速、轴肩和搅拌针直径、搅拌头倾斜角等,搅拌摩擦焊(FSW)已经广泛应用于制造铝合金接头。FSW参数能够显著影响焊接强度,其中,搅拌头倾斜角是一种重要的过程参数。因此,本文作者研究搅拌头倾斜角对搅拌摩擦焊铝合金(AA2014-T6)搭接焊接强度的影响。搅拌头倾斜角的变化范围为0°~4°,等值增量为1°,其他参数保持一致。采用宏观和微观组织分析、显微硬度测量、扫描电镜、透射电镜和能谱分析等方法对搅拌摩擦搭接接头的搭接剪切强度进行测定。结果表明,当搅拌头倾斜角为1°~3°时,可获得无缺陷的焊接接头;当倾斜角为2°时,可获得具有最大剪切强度(14.42 kN)和显微硬度(HV 132)的接头。采用1°和3°倾斜角焊接的接头其剪切强度较差,这是搅拌摩擦焊过程中焊接区域内物料流动不平衡导致的。

AZ61A镁合金搅拌摩擦焊接头在NaCl溶液中的腐蚀行为(英文)

对6mm厚的挤压态AZ61A镁合金板进行搅拌摩擦对接焊。采用浸泡试验研究焊接接头在NaCl溶液中的腐蚀行为,建立了一个经验公式来预测在不同的溶液pH值、浸泡时间和氯离子浓度下的接头腐蚀速率。该经验公式的可信度水平为95%。采用3因素、5水平的中央复合旋转设计方法来减少实验工作量。采用响应面方法来构建方程。结果表明,在碱性溶液中AZ61A镁合金接头的腐蚀速率要比其在酸性或中性溶液中的低,而且腐蚀速率随着氯离子浓度的降低和浸泡时间的延长而减少。β相的分布对其腐蚀形貌有重要影响。

Al/SiC_p金属基复合材料搅拌摩擦焊工艺参数的多目标优化(英文)

碳化硅颗粒(SiC_p)增强铸造铝基复合材料(MMC)在制造高比强、高温性能好和耐磨的轻质结构件中得到广泛应用。焊接接头的性能取决于搅拌摩擦焊(FSW)的工艺参数。研究铸造AA6061/20%SiC_p(体积分数)金属基复合材料焊接接头的抗拉强度、缺口拉伸强度和硬度,建立搅拌摩擦焊工艺参数(刀具转速、焊接速度和轴向力)与接头性能(抗拉强度、缺口拉伸强度和焊点硬度)之间的关系,确定最佳的焊接条件,以最大限度地提高接头的力学性能。结果表明,当搅拌针转速为1370 r/min、焊接速度为88.9 mm/min和轴向力为9.6 kN时,接头的最大抗拉强度、缺口拉伸强度和硬度分别为265 MPa、201 MPa和HV114。

Stress corrosion cracking behaviour of gas tungsten arc welded super austenitic stainless steel joints

Super 304 H austenitic stainless steel with 3% of copper posses excellent creep strength and corrosion resistance, which is mainly used in heat exchanger tubing of the boiler. Heat exchangers are used in nuclear power plants and marine vehicles which are intended to operate in chloride rich offshore environment. Chloride stress corrosion cracking is the most likely life limiting failure with austenitic stainless steel tubing. Welding may worsen the stress corrosion cracking susceptibility of the material. Stress corrosion cracking susceptibility of Super 304 H parent metal and gas tungsten arc(GTA) welded joints were studied by constant load tests in 45% boiling Mg Cl2 solution. Stress corrosion cracking resistance of Super 304 H stainless steel was deteriorated by GTA welding due to the formation of susceptible microstructure in the HAZ of the weld joint and the residual stresses. The mechanism of cracking was found to be anodic path cracking, with transgranular nature of crack propagation. Linear relationships were derived to predict the time to failure by extrapolating the rate of steady state elongation.

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

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.