分别采用阿普拉斯焊接工艺、中频逆变点焊工艺对1.0 mm厚SUS301L-ST与1.5 mm厚EN1.4318+2G轨道车辆用奥氏体不锈钢进行电阻焊接,焊后根据相关标准进行点焊接头的外观质量、断面质量观察,剪切拉伸、轴向拉剪疲劳试验与分析.结果 表明,与中频逆变点焊接头相比,阿普拉斯焊接接头外观质量得到大幅提升,达到无痕焊接,拉剪性能以及疲劳性能也均符合轨道车辆产品规定的要求.

Aluminum alloy components of high-speed trains have a great risk of being corroded by various corrosive medium due to extremely complex atmospheric environments. This will bring out huge losses and reduce the safety and stability of trains. In order to solve the problem, cold spray process was used for repairing the damage of the aluminum alloy components with Al-based powders. Microstructure, mechanical properties and corrosion behavior were studied. The results indicated that there were very few pores and cracks in the repaired areas after repairing. The average microhardness of the repaired areas was 54.5 HV ± 3.4 HV, and the tensile strength of the repaired samples was 160.4 MPa. After neutral salt spray tests for 1000 h, the rate of mass loss of the samples repaired by cold spray was lower than that of 6A01 aluminum alloy. The electrochemical test results showed that the repaired areas had a higher open circuit potential than 6A01 aluminum alloy. As a result, the repaired areas such as the anode protected its nearby substrate. The samples repaired by cold spray exhibited better corrosion than 6A01 aluminum alloy. Cold spray process and Al-based powders are applicable for repairing the aluminum alloy components of high-speed trains.

Aluminum alloy structures may be damaged due to wear or corrosion while in service. These damages will bring about huge financial costs, as well as a huge amount of energy consumption. There is an urgent need to search for an appropriate repair method in order to solve this problem. In this research, the cold spray process was used to repair the damages by using a mixture of powders with Al and Al2O3. A 7N01-T4 aluminum alloy plate with a factitious pit was regarded as the damaged sample. The microstructure, mechanical properties, and corrosion behavior were studied. The results showed that there were no visible perforative pores or cracks in the repaired areas. The microhardness of the repaired areas was in the range of 57.4–63.2 HV and was lower than that of the 7N01-T4 aluminum alloy. The tensile strength of the repaired samples was markedly improved compared with the unrepaired samples. The alternate immersion test results indicated that the repaired samples had the lowest rate of mass loss compared with 7N01-T4 and the unrepaired samples. After alternate immersion tests for 504 h, the repaired samples were covered with dense corrosion products. The repaired samples had a superior corrosion resistance compared to that of 7N01-T4. Thus, the cold spray process is a method of repairing damage in aluminum alloy structures.

In this paper, aiming at high-end stainless steel subway products, a new product of stainless steel rail vehicles manufactured by using thin plate lap laser welding instead of resistance spot welding was first developed in China, which made the stainless steel car body structure more optimized, and the welding quality and manufacturing process of its car body steel structure were significantly improved, and advanced stainless steel vehicles entered the high-end vehicle market. Therefore, this paper develops the laser welding process of stainless steel car body, optimizes the process parameters, defines the weld quality standard and develops the weld quality monitoring device, builds the laser welding manufacturing system, and realizes the batch application of the new laser welding technology in high-end stainless steel rail vehicle products. At present, it has formed the world's leading batch production capacity of high-end stainless steel vehicle products and improved the competitiveness of the company at home and abroad.

采用周期浸润腐蚀实验方法分别研究了N800CF、SMA490BW和Q345C三种母材在1.0x10-2mol/L NaHSO3腐蚀溶液中的失重率,以及焊接热输入对N800CF焊接接头腐蚀行为的影响,利用SEM、XRD分别对表面锈层进行形貌观测和相组成及腐蚀机理分析.结果表明,在本实验条件下,N800CF腐蚀失重率低于Q345C,但高于SMA490BW.与N800CF母材相比,N800CF焊接接头的腐蚀失重率降低,且当热输入不超过15 kJ/cm时接头耐腐蚀性能优良.

为了探究动车组转向架构架T形接头单丝、双丝GMAW焊接温度场及应力场分布特征,基于ABAQUS有限元分析软件,采用数值模拟与实际测量相结合的方式,以转向架侧梁SMA490BW耐候钢T形接头为研究对象,分别建立了单丝及双丝焊的热源模型,模拟了接头的焊接温度场和焊后残余应力场,并通过试验对模拟结果进行了验证.结果表明:单丝焊和双丝焊的焊缝模拟尺寸与测量结果的相对误差均不超过5％.与单丝焊相比,双丝焊的熔池峰值温度提高,熔池在长度方向上被拉长,焊缝厚度明显增大,焊脚尺寸也略有增大,焊后残余拉应力分布范围有所减小,焊缝最高残余拉应力下降8.5％.

The effects of arc modes on laser-arc hybrid welding for AA6082-T6 aluminum alloy were comparatively studied. Two arc modes were employed: pulsed metal inert gas arc and cold metal transfer arc. The results indicated that joints without porosity, undercutting, or other defects were obtained with both laser-pulsed metal inert gas hybrid welding (LPMHW) and laser-cold metal transfer hybrid welding (LCHW). Spatter was reduced, and even disappeared, during the LCHW process. The sizes of equiaxed dendrites and the width of the partially melted zone in the LPMHW joint were larger than those in the LCHW joint. The microhardness in each zone of the LPMHW joint was lower than that of the LCHW joint. The softening region in the heat-affected zone of the LPMHW joint was wider than that of the LCHW joint. The tensile strength of the LCHW joint was higher than that of the LPMHW joint. For the two joints, the fractures all occurred in the softening region in the heat-affected zone, and the fracture morphologies showed ductile fracture features. The dimples in the fractograph of the LCHW joint were deeper than those of the LPMHW joint.

研究了MIG焊叠加对6A01-T5铝合金FSW焊接头组织及性能的影响.结果表明,MIG/FSW叠加焊缝熔合良好,叠加位置未出现气孔等缺陷,FSW焊核区及热影响区组织发生粗化,叠加位置附近微观组织出现明显改变;叠加区域硬度明显降低,尤其是FSW焊缝热力影响区和热影响区.FSW、中心叠加、前进侧热力影响区叠加和后退侧热力影响区叠加MIG焊接头的抗拉强度分别为219.8,188.0,195.4和191.4 MPa,MIG焊叠加降低了接头的抗拉强度,断口均表现韧性断裂特征;FSW焊接头及带有MIG叠加焊缝余高的三种接头中值疲劳强度分别为76.7,65.0,67.5和65.0 MPa,MIG焊叠加也使FSW接头的疲劳性能有所下降.

采用周期浸蚀试验研究了N800CF低碳贝氏体钢及其焊接接头在模拟工业大气环境下的耐腐蚀行为,并与SMA490BW和Q345C两种材料进行了对比.通过计算腐蚀失重率以及电化学极化曲线分析其腐蚀行为与机理.结果表明,N800CF低碳贝氏体钢耐工业大气腐蚀性能低于SMA490BW耐候钢,但好于Q345C低合金钢;N800CF低碳贝氏体钢接头的耐蚀性能高于母材,且不同焊接热输入下的N800CF低碳贝氏体钢接头在腐蚀前期耐蚀性相差不大,随着腐蚀时间的延长,线能量为15 kJ/cm时焊接接头耐蚀性最好,当线能量达到18 kJ/cm时其耐蚀性相对较差.

采用成组法和升降法,对板厚0.8mm的SUS301L-DLT与板厚2mm的EN1.4318+2G轨道车辆用不锈钢激光搭接焊接头分别在室温空气环境、-40℃低温空气环境和3.5％NaCl水溶液环境中进行剪切拉伸疲劳试验,绘制S-N曲线并进行断口形貌分析.试验结果表明:在循环寿命为1×107条件下,与空气环境相比,-40℃低温环境下不锈钢激光搭接焊接头的剪切拉伸疲劳强度提高57.8％,而在3.5％NaCl水溶液中接头疲劳强度降低25.5％.激光焊接头的疲劳裂纹均起始于搭接下板内侧靠近焊缝应力集中处,沿下板厚度方向扩展直至断裂,其中在瞬时断裂区存在大量韧窝,呈韧性断裂特征.

6082-T6 aluminum alloy with thickness of 6 mm were welded by laser-MIG hybrid welding. The effects of welding parameters on the porosity distribution, the correlations between the porosity distribution and mechanical properties were comprehensively investigated. The porosities mainly appeared near the fusion line of the arc zone when the arc current larger than 140 A, and which mainly existed in the center of the laser zone with other unsuitable parameters. Adopting low welding speed and setting heat source distance as around 3 mm were beneficial for the reduction of the porosity rate. The laser power, defocus distance, fit-up gap and gas flow rate had less effects on the porosity distribution. The average tensile strength of the joints without porosities was 260 MPa, which decreased to 224 MPa and 202 MPa as the porosity rate increased to 5.1% and 8.9%. The tensile specimens fractured at the heat affected zone or in the weld center when the porosity rates less or greater than 3%, and the fracture feature was diverted from ductile fracture to ductile and brittle mixed mode as the porosity rate increasing. The fatigue strength reduced from 113 MPa to 56 MPa when the porosity rate increased from 0% to 8.9%, while the porosity position had little effect on it. The fracture initiated in the weld surface when the joints without porosity, and which initiated near the porosity when the porosities existed in the joint.

6A01-T5 aluminum alloy and SUS301L-DLT austenitic stainless steel sheets were welded by a laser-cold metal transfer (CMT) hybrid welding-brazing method with ER5183 filler wire. We researched the weld forming, intermetallic compounds, and mechanical character, which are influenced by laser power, wire feeding speed, and welding speed. Well-formed joints with uniformly distributed interface layers were obtained under certain parameters. The spreading and wetting distance on the steel upper surface increased initially and then decreased as the laser power increased, and increased progressively as the wire feeding speed increased or welding speed decreased. There were both Fe2Al5 and Fe4Al13 in the interfacial intermetallic compounds (IMCs) layer. The thickness was controlled to within 2.0–6.9 µm. The thickness of the IMCs layer increased as the heat input increased; however, the increasing rate decreased gradually. The tensile strength of the joints was not only completely dependent on the thickness of the IMCs, but also on the spreading and wetting distance on the steel surface. The highest tensile strength could reach up to 188.7 MPa, which is about 77.1% of that of the base aluminum alloy. The tensile sample fracture occurred at the IMCs layer, and regional metallurgical bonding happened in the interface layer.

Currently, high-speed trains work under various atmospheric environments, and the bogie as a key component suffers serious corrosion. To investigate the corrosion behavior of bogies in industrial atmospheric environments, the periodic immersion wet/dry cyclic corrosion test for SMA490BW steel and automatic metal active gas (MAG) welded joints used for bogies was conducted in the present work. Corrosion weight loss rate, structure, and composition of rust layers as well as electrochemistry parameters were investigated. The results showed that the corrosion weight loss rate decreased with increasing corrosion time; furthermore, the corrosion weight loss rate of the welded joints was lower than that of SMA490BW steel. The XRD results showed that the rust layers formed on SMA490BW steel and its welded joints were mainly composed of α-FeOOH, γ-FeOOH, Fe2O3, and Fe3O4. The observation of surface morphology indicated that the rust layers of the welded joints were much denser and had a much finer microstructure compared with those of SMA490BW steel. After corrosion for 150 h, the corrosion potential of the welded joints with rust layers was higher than that of SMA490BW steel. In short, the welded joints exhibited better corrosion resistance than SMA490BW steel because of the higher content of alloy elements, as shown in this work.

利用双环电化学动电位再活化法研究了激光焊接热输入对奥氏体不锈钢激光搭接焊接头晶间腐蚀敏感性的影响,并通过X-射线衍射仪、扫描电子显微镜及能谱仪分析了激光搭接焊接头的相组成与主要合金成分.结果表明,不锈钢激光搭接焊接头的晶间腐蚀敏感性高于母材,且随着激光热输入的增加,焊接接头的阳极极化曲线钝化区间逐渐变窄,维钝电流密度增大,再活化率Ra=Ir/Ia增大,接头的晶间腐蚀敏感性增加.与焊缝金属相比,焊接热影响区的晶间腐蚀倾向更为明显,成为接头中耐晶间腐蚀性能最薄弱的部位,而在晶界上析出M23C6导致晶界贫铬是晶间腐蚀敏感性增加的主要原因.

采用高功率光纤激光焊接设备对0.8 mm厚SUS301L-DLT和2.0 mm厚EN 1.4318+2G奥氏体不锈钢板进行了激光搭接焊工艺试验,并对接头分别进行了草酸腐蚀、硝酸腐蚀和电化学腐蚀试验,分析了接头及其母材在不同腐 蚀条件下的晶间腐蚀行为.结果表明,焊接接头及母材经过草酸溶液浸蚀后,其晶界组织均为第一类阶梯组织,而在硝酸溶液热浸蚀时,接头的腐蚀率高于其母材金属.在硫酸溶液腐蚀介质中,焊接接头及其母材的双环电化学动电位再活化(DL-EPR)曲线上均出现再活化峰,其中接头的再活化率值较母材大,表明奥氏体不锈钢激光搭接焊接头的抗晶间腐蚀性能下降.

The 7075 aluminum alloys have major applications in commercial, transportation industry and military air carriers, owing to their associated light weight, high strength, good machinability, high fracture toughness and low fatigue crack growth. Several welding techniques, such as metal inert gas (MIG) welding, tungsten inert gas (TIG) welding, laser welding and friction stir welding (FSW), have been applied to weld the 7075 aluminum alloys. However, their applications are limited because of the lower weld strength, slower welding speed and other significant limitations of them. Among the different welding techniques, plasma-MIG hybrid welding is a new fabrication technique with many advantages such as stable welding process, no weld spatter, the decreased pores, small grain size and high joint quality. Up to now, the study mainly focuses on coaxial plasma-MIG hybrid welding, and it is rare in dealing with the hot cracking susceptibility of 7000 senes aluminum alloys welded by paraxial plasma-MIG hybrid welding. In this work, the paraxial plasma-MIG hybrid welding system was used to weld 7075-T6 aluminum alloy plates. The quantitative relationship between plasma-MIG hybrid welding parameters of 7075 aluminum alloy and weld penetration was established by linear regression orthogonal test. Hot ductility tests were studied by using the thermal simulated test to determine the brittleness temperature range of the alloy. Welding hot cracking susceptibility tests were conducted by using the fish bone method, and the type and cause of the hot cracking were analyzed by SEM, EDS and OM. The results indicated that the brittleness temperature range of 7075 aluminum alloy was 470 similar to 620 degrees C. When the heat inputs of plasma-MIG hybrid welding were 2.52, 2.95 and 3.42 kJ/cm respectively, the welding hot cracking susceptibility decreased and then increased with the heat input increasing. The type of cracking in partially melted zone of base metal was liquation cracking, and that of weld zone was solidification cracking. When the heat input was 2.95 kJ/cm, the welding hot cracking sensitivity was the least, and the welding cracking was solidification cracking. Compared to MIG weld-ng joints, the hot cracking susceptibility of plasma-MIG hybrid welding joints decreased by 47% under the same conditions.

Plasma-MAG hybrid welding method and ordinary MAG welding method were used respectively to carry out the welding tests of SUS301L-MT stainless steel middle heavy plates for railway vehicles under the condition of ER308LSi welding wire and ψ (Ar)98％+ψ(CO2)2％ shield gas selected.The pulsating tensile fatigue test and the fatigue strength estimation were conducted on the butt welded joints and the cruciform joints of plasma-MAG hybrid welding and ordinary MAG welding respectively.The results indicate that the median fatigue strength in fatigue life of 2×106 cycle is 279 MPa and 160 MPa for the butt joint and the cruciform joint of plasma-MAG hybrid welding respectively.Compared with ordinary MAG welding,the fatigue strength of plasma-MAG hybrid welded joints increases,in which the fatigue strength of butt joint is higher than that of cruciform joint.

对转向架SMA490BW耐候钢在不同焊接线能量下进行了单丝MAG焊接试验,研究了线能量对接头显微组织与力学性能的影响.结果表明:焊接线能量在10～32 kJ/cm时,随着线能量的增加,焊缝金属中的晶内针状铁素体逐渐转变为条状或块状的铁素体,晶界侧板条铁素体尺寸增大;热影响区晶粒逐渐粗化,粒状贝氏体和晶界的先共析铁素体增加,当线能量达到32 kJ/cm时晶界的先共析铁素体几乎呈网状分布.不同线能量下,焊接接头拉伸试样均断裂于母材.随着线能量的增加,焊缝金属和热影响区的冲击功逐渐减小,对于焊缝金属、热影响区,线能量分别不超过25、32 kJ/cm时,其冲击功满足在-40℃下不小于27 J的要求.

In order to study the influence of welding heat input on low temperature toughness of SMA490BW weathering steel,the thermal simulation test was conducted on the coarse grain heat-affected zone (CGHAZ) of SMA490BW weathering resistant steel by using Gleeble-1500 thermal simulation test machine,and the low-temperature impact test was carried out at-40 ℃ temperature under the condition of different heat input.The results show that low-temperature impact toughness of CGHAZ decreases with the increase of welding heat input,but the impact energy can meet the requirement of standard of not less than 27 J when the heat input is no more than 30 kJ/cm.The increase of granular bainite,the formation of feathery bainite and the coarsening of grains in the coarse grain heat-affected zone of welding thermal simulation are the main reasons leading to the decrease of low-temperature impact toughness.

选用转向架构架常用的SMA490BW耐候钢及不同焊接工艺的接头为对象,研究其在中性盐雾腐蚀条件下的腐蚀行为,并利用光学显微镜、扫描电镜、X射线衍射仪等分析耐候钢及其接头的微观组织、腐蚀形貌、锈层特征及腐蚀产物.结果表明:随着腐蚀时间的增加,耐候钢及其接头的腐蚀失重先增加后降低;腐蚀360h后,腐蚀产物主要为α-FeOOH、γ-FeOOH和Fe3O4;SMA490BW耐候钢及其接头的耐腐蚀性从大到小依次为SMA490BW耐候钢、双丝自动焊接头、单丝自动焊接头、单丝手工焊接头.