动态低应力小变形无势裂随焊锤击焊接技术研究

从力学角度出发,首次提出随焊锤击的焊接技术,并结合跨焊缝两侧横向位移的测量及显微组织的研究,分析了随焊锤击防止焊接裂纹的作用机理,试验结果表明,随焊狂击技术可显著地改善焊缝显微组织及残余应力分布,防止焊接热裂纹的产生,并能够有效地控制LY12CZ铝合金薄板焊接横向及纵向收缩变形,可以认为随焊锤击是一种更合理,更具实用价值的低应力小变形无热裂的焊接技术新方法。     

动态低应力小变形无热裂随焊锤击焊接技术研究

从力学角度出发,首次提出随焊锤击的焊接技术,并结合跨焊缝两侧横向位移的测量及显微组织的研究,分析了随焊锤击防止焊接热裂纹的作用机理．试验结果表明,随焊锤击技术可显著地改善焊缝显微组织及残余应力分布,防止焊接热裂纹的产生,并能够有效地控制LY12CZ铝合金薄板焊接横向及纵向收缩变形．可以认为随焊锤击是一种更合理、更具实用价值的低应力小变形无热裂的焊接技术新方法．     

原位研究胶接修补固化温度对LY12CZ铝合金疲劳裂纹扩展门槛值的影响

通过带加温系统的扫描电镜原位观测技术研究了胶接修补固化温度对LY12CZ铝合金疲劳裂纹扩展行为的影响。结果表明:高温使得LY12CZ铝合金中萌生孔洞并聚集长大,从而易于萌生短裂纹,产生沿晶破裂趋势,降低材料的疲劳性能;LY12CZ铝合金疲劳裂纹扩展门槛值随着温度的升高逐步降低,且在温度撤除后,疲劳裂纹扩展门槛值并未恢复到常温状态下的门槛值,因此胶接修补过程中需要严格控制胶黏剂的固化温度,以减小其对基体材料疲劳性能的影响。     

LY12—CZ和LC4—CS铝合金在多种环境中的腐蚀疲劳裂纹扩展

文中对两种常用铝合金LY12—CZ和LC4—CS在各种环境中的疲劳裂纹扩展速率与实验室空气中的数据进行了比较,揭示了不同的腐蚀环境对疲劳裂纹扩展速率的影响。腐蚀环境的参加使两种铝合金的裂纹扩展速率明显加快,其影响的严重程度由重到轻依次为:盐水,盐雾,盐雾+SO_2,潮湿空气。LC4—CS合金比LY12—CZ合金对环境因素表现更为敏感,其疲劳裂纹扩展抗力在腐蚀环境中的降低更为显著。     

钇对低合金钢焊缝组织和低温韧性的影响

本文通过焊条药皮向低台金钢焊缝中掺入钇的方法,研究钇对焊缝组织形态和低温韧性的影响。研究结果表明:在低合金钢焊缝中掺入适量钇可使沿晶界析出的粗大的先共析铁素体和侧板条铁素体的比例减小,而使细小的针状铁素体比例大大增加,晶粒细化,从而提高焊缝的低温韧性。     

随焊冲击碾压对LY12CZ铝合金接头组织和性能的影响

随焊冲击碾压是一种控制薄壁结构焊接应力变形、防止热裂纹的新方法.这种方法同时也改善了LY12CZ铝合金接头组织,提高了其力学性能.金相和拉伸断口SEM观察表明,随焊冲击碾压焊缝区晶粒明显细化,组织更加致密,气孔、缩松等缺陷大大减少.与常规焊接接头拉伸断口脆性和塑性断裂特征并存相比,随焊冲击碾压焊缝断口形貌呈现典型的塑性断裂的特征.随焊冲击碾压之后,接头区的硬度有了明显提高,表明接头软化区重新得到强化.而拉伸、疲劳和三点弯曲实验结果表明,随焊冲击碾压之后接头的抗拉强度、塑性及疲劳寿命等力学性能也都得到不同程度的提高.由于薄弱的焊趾部位得到强化,裂纹萌生位置也由焊趾转移到焊缝.     

强电场对摩擦焊接头组织与性能的影响

为提高摩擦焊缝金属的变形能力，采用外加电场考察了摩擦焊缝金属的电塑性效应，利用金属组织观察、显微硬度测试及抗拉试验，定量分析了外加强电场对LY12铝合金摩擦焊缝组织与力学性能的影响，结果表明：外加强电场使焊缝金属组织轴向分布梯度减小，等轴性提高；不同焊接压力时，强电场使焊接接头的动态再结晶区宽度有不同程度的增大；在中等摩擦压力作用下，使近轴心线处的动态再结晶区宽度趋干均匀；此外，外加电场使接头焊合区硬度增加，并使焊接接头的硬度分布趋干均匀；采用强规范施焊时，外加电场提高了焊接接头的抗拉强度。     

供应状态LY12CZ硬铝合金的动态再结晶与超塑性研究

本文对供应状态LY12CZ硬铝合金在未经任何超细预处理的情况下进行了超塑性变形的力学特性、显微组织方面的研究。确认LY12CZ硬铝合金在等温压缩变形中发生了动态再结晶,动态再结晶会诱发超塑性,使用新研制的D润滑剂,使其能在快速成形时有较好的超塑性能,在实际生产中有推广应用价值。     

珠光体耐热钢与奥氏体不锈钢的焊接

奥氏体不锈钢(1Cr18Ni9Ti)和珠光体耐热钢(12Cr12Mo)焊接时,用在珠光体耐热钢的坡口表面堆焊过渡层或附加中间过渡段的方法,可以得到奥氏体和少量铁素体的双相组织的焊缝,焊接接头在500℃以上的条件下工作,提高焊接接头的热持久强度,取得较好的使用效果。     

关于隔离开关各种常见故障的分析及措施

奥氏体不锈钢(1Cr18Ni9Ti)和珠光体耐热钢(12Cr12Mo)焊接时,用在珠光体耐热钢的坡口表面堆焊过渡层或附加中间过渡段的方法,可以得到奥氏体和少量铁素体的双相组织的焊缝,焊接接头在500℃以上的条件下工作,提高焊接接头的热持久强度,取得较好的使用效果。     

结构钢焊接匹配性研究进展

对结构钢焊接的高强匹配和低强匹配两种技术路线的发展进行了综述。在焊缝金属具有足够韧性的情况下,高强匹配能利用焊缝金属的高强度降低位于焊缝中裂纹的扩展驱动力、从而有利于焊接接头抗断性能的提高;随着结构钢强度的提高,焊接冷裂纹敏感性增大、焊缝韧性降低,采用焊接裂纹敏感性相对较低、焊缝金属塑韧性相对较高的低强匹配焊接技术能较好的控制焊接冷裂纹的产生并保证接头的抗断性能。     

Effect of post-weld aging treatment on mechanical properties of Tungsten Inert Gas welded low thickness 7075 aluminium alloy joints

This paper reports the influence of post-weld aging treatment on the microstructure, tensile strength, hardness and Charpy impact energy of weld joints low thickness 7075 T6 aluminium alloy welded by Tungsten Inert Gas (TIG). Hot cracking occurs in aluminium welds when high levels of thermal stress and solidification shrinkage are present while the weld is undergoing various degrees of solidification. Weld fusion zones typically exhibit microstructure modifications because of the thermal conditions during weld metal solidification. This often results in low weld mechanical properties and low resistance to hot cracking. It has been observed that the mechanical properties are very sensitive to microstructure of weld metal. Simple post-weld aging treatment at 140 °C applied to the joints is found to be beneficial to enhance the mechanical properties of the welded joints. Correlations between microstructures and mechanical properties were discussed.     

Failure analysis of a welded impeller in coke oven gas environment

In this study, a centrifugal impeller made of FV520B martensitic precipitation hardening stainless steel failed after 12 months service in coke oven gas environment. An increase in vibration was recorded prior to the breakdown. Analysis revealed that fracture initiated at the welded joints and the main failure mechanism was sulfide stress corrosion cracking (SSC). Efforts were made to assess the cracking susceptibility of base metal and weld metal. Results indicated that welded joints experienced lower fracture toughness and higher susceptibility to SSC cracking. This paper brings out the details of investigation and suggests remedial measures to improve performance of this welded impeller under aggressive environment.     

Microstructure and mechanical properties of laser welded joints between 2198/2060 Al–Li alloys

Dissimilar Al–Li alloys (2198 and 2060) were laser welded without the addition of filler material. The effects of welding parameters on the formation of the welded joints, microstructure evolution, solute segregation, porosity and their relationships with the mechanical properties of the joint were investigated. It was found that reducing the weld heat input can effectively prevent grain coarsening, while decreasing porosity and reducing the tendency for hot cracking, thereby enhancing the properties of the joint. The dissolution of precipitates such as the T1 phase and θ′ phase in the base metal, and the variations in Cu and Mg content between grain interiors and boundaries, resulted from solute segregation during welding, leading to reductions in the strength of the weld.     

Susceptibility to Hot Cracking and Weldment Heat Treatment of Haynes 230 Superalloy

This study investigates the susceptibility of hot cracking and weldment heat treatment of Haynes 230 superalloy. The Varestriant test was conducted to evaluate this susceptibility. Welding was performed by gas tungsten arc welding （GTAW） and plasma arc welding （PAW） with stress relief heat treatment and solid solution heat treatment. A tensile test is then performed to measure the changes in the mechanical properties of the heattreated material. The results indicate that the number of thermal cycles does not affect the susceptibility of Haynes 230 superalloy to hot cracking. However, it does increase the strain. In weldment of heat treatment, stress relief annealing increases the yield strength and tensile strength of the welded parts. The section of the tensile specimens shows fibrous fractures on the welded parts, regardless of whether they are heat-treated.     

Corrosion resistance of girth joints of pipes made by contact butt welding

We establish that welded joints made by contact butt welding of ferritic-austenitic steel are not susceptible to general, intercrystalline, and pitting corrosion, and the mechanical properties of the joints of pipes comply with the requirements of the ISO API-1104 standard. The base metal and welded joints are subjected to corrosion cracking in a boiling 42% MgCl₂ solution and NACE solution. E. O. Paton Institute of Electrical Welding, Ukrainian Academy of Sciences, Kiev. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 1, pp. 107–108, January–February, 1999.     

Experimental investigation of the hot cracking mechanism in welds on the microscopic scale

The results of the accurate experimental observations on binary Al-Si alloys are presented, which clearly demonstrate that the solidification cracking is a result of the accumulation of macroscopic tensile displacement in aβmicroscopic intergranular liquid film of segregates at the final stage of the weld metal solidification. The reconstructed mechanism of crack initiation provides a clear phenomenological interrelation between the cracking susceptibility, parameters of the welding process and properties of the base and filler material. The correspondent numerical model takes into account the effects of displacement accumulation as well as the influence of thermo-dynamical and thermo-mechanical properties of the welded material. It is successfully applied for development of technological means for elimination of the solidification cracking during welding of aluminium alloys AA6056, such as a multi-beam welding.     

基于惰性气体钨极保护焊受电弓用6082铝合金角接接头开裂分析

受电弓在组装时发现下臂主轴与吊耳所组成的角接接头近焊缝区出现表面裂纹,结合焊接结构和实际工艺,通过材料理化性能试验、T型接头裂纹敏感性分析、焊接接头裂纹断面宏观和微观检查,对裂纹产生的原因及机理进行了分析。结果表明：受电弓下臂主轴与吊耳的焊接接头近焊缝区开裂是由于热输入过大而引起的液化裂纹,而吊耳装配时的锤击导致该液化裂纹进一步扩展,形成了沿焊趾的开裂。最后提出了预防裂纹的措施,保证了产品的焊接质量。     

Improvement of weld temperature distribution and mechanical properties of 7050 aluminum alloy butt joints by submerged friction stir welding

Submerged friction stir welding (FSW) in cold and hot water, as well as in air, was carried out for 7050 aluminum alloys. The weld thermal cycles and transverse distributions of the microhardness of the weld joints were measured, and their tensile properties were tested. The fracture surfaces of the tensile specimens were observed, and the microstructures at the fracture region were investigated. The results show that the peak temperature during welding in air was up to 380 °C, while the peak temperatures during welding in cold and hot water were about 220 and 300 °C, respectively. The temperature at the retreated side of the joint was higher than that at the advanced side for all weld joints. The distributions of microhardness exhibited a typical “W” shape. The width of the low hardness zone varied with the weld ambient conditions. The minimum hardness zone was located at the heat affected zone (HAZ) of the weld joints. Better tensile properties were achieved for joint welded in hot water, and the strength ratio of the weld joint to the base metal was up to 92%. The tensile fracture position was located at the low hardness zone of the weld joints. The fracture surfaces exhibited a mixture of dimples and quasi-cleavage planes for the joints welded in cold and hot water, and only dimples for the joint welded in air.     

Effect of cooling to 4.2 K on the strength and cracking resistance of the parent metal in welded joints in 07Kh13N4AG20 steel

The results are presented of experimental examination of short-term strength and cracking resistance of the parent metal and welded joints in 07Kh13N4AG20 steel in the temperature range 293–4.2 K. The mechanical characteristics of the welded joint in the examined steel are compared with the characteristics of 12Kh18N10T and 03Kh20N16AG6 steels. The results show that the mechanical properties and crack propagation resistance of the weld metal in 07Kh13N4AG20 steel are similar to those of the parent metal.Translated from Problemy Prochnosti, No. 9, pp. 45–48, September, 1990.