强制冷却搅拌摩擦焊接工艺

搅拌摩擦焊接在工业生产中应用的主要问题之一,是焊接硬化状态材料时接头强度系数较低.简要分析了焊接热对接头强度的影响,提出了在搅拌摩擦焊接过程中进行强制冷却的工艺方法.对比了强制冷却对紫铜搅拌摩擦焊接头表面状况、硬度分布和接头性能的影响,建立了强制冷却搅拌摩擦焊接过程中焊接区温度的近似表达式.结果表明,在紫铜搅拌焊接过程中进行强制冷却,可以降低焊接过程中焊缝及热力影响区变形金属的温度,减小接头软化的程度和范围,提高搅拌摩擦焊接接头的性能.采用转速1 500 r/min、移动速度0.3 mm/s的强制冷却的工艺方法,得到的紫铜搅拌摩擦焊接头抗拉强度达269 MPa.     

6061-T6铝合金DP-MIG焊轧复合成形接头组织与力学性能

为解决6061-T6铝合金焊后热影响区软化导致力学性能下降的问题,基于焊接接头余高大变形强化过时效软化区的思想,采用双轧辊系统对6061-T6薄板铝合金直流双脉冲熔化极气体保护焊(DC double pulse metal inert gas welding,DP-MIG焊)接头进行同步双面轧制,并分析了焊轧复合成形接头组织与力学性能.结果表明,焊缝晶粒受到竖直方向的轧制力发生大塑性变形,内部气孔消失,焊缝区域变宽,邻近焊缝的热影响区受到来自焊缝的挤压力发生协同宏观变形,远离焊缝的过时效软化区组织受到来自焊缝处的压应力,从沿垂直焊缝方向产生部分协同形变强化;接头的硬度明显提升,过时效软化区的硬度由60～70 HV提升至80～90 HV,过时效软化区的拉伸性能也有所提升,当焊接速度为800 mm/min时,抗拉强度最佳可达到母材的83.6%,相较于焊接接头提升19.4%,进而实现了对过时效软化区的强化效果.     

20MnSi控冷钢筋焊接软化区宽度

采用控冷工艺生产的20MnSi钢筋在焊接时热影响区性能有软化现象,软化区的存在使得钢筋的承载能力下降。通过控制焊接工艺参数和自回火温度可以控制软化区的宽度,从而改善钢筋的承载性能。基于C.M.Adams公式建立了自回火温度、焊接工艺参数和软化区宽度的模型,并在此基础上进行了分析。结果表明,自回火温度升高时,软化区宽度减小;预热温度升高或焊接热输入增大时,软化区宽度增大;小规格钢筋焊接HAZ软化区宽度较大规格钢筋大。     

JFE980S高强钢焊接接头软化分析

研究了激光-MAG复合热源和常规MAG两种焊接方法在焊接JFE980S低合金调质高强钢时的接头软化问题.通过对接头强度、硬度和组织的测试分析,探讨了低合金调质高强钢焊接接头的软化规律及机制.结果表明,焊后JFE980S高强钢常规MAG焊接头发生了明显软化,而激光-MAG复合热源焊接接头软化不明显;激光-MAG复合热源焊接接头的软化区域宽度和软化程度明显小于常规MAG焊接头;接头的软化主要发生在焊接热影响区的过回火区域和不完全正火区域,该区域中出现沿晶界呈块状或颗粒状分布的组织是造成接头软化的主要原因.     

铁素体不锈钢激光-MAG复合热源焊缝成形及接头冲击韧性分析

利用激光-MAG 复合热源分别进行了 T4003 和 TCS 铁素体不锈钢的焊接试验研究.通过与常规 MAG 焊的对比,测试分析了两种焊接方法的焊缝成形、接头的低温冲击韧性及接头的微观组织.结果表明,激光-MAG 复合热源焊接易于实现铁素体不锈钢的单面焊双面成形,与常规 MAG 焊相比,其焊接效率可以提高 1 倍以上.利用激光电弧复合热源可以提高铁素体不锈钢焊接接头的低温冲击韧性,较常规 MAG 焊,复合焊接头的低温冲击韧性可以提高 50%以上.激光-MAG 复合热源焊接接头热影响区粗晶区组织宽度明显小于常规 MAG 焊接头的粗晶区宽度.

Abstract：

Laser-MAG hybrid welding of T4003 and TCS ferrite stainless steels was studied. Through comparing with the conventional MAG welding of ferrite stainless steel, the results of the two welding methods including the appearance of weld, impact toughness under low temperature and the microstructure of the butt joints were tested and analysed. The analysing results show that it is easy to get one-side welding with back by laser-MAG hybrid welding. Comparing with the conventional MAG welding, the welding efficiency of ferrite stainless steel by laser-MAG hybrid welding can be improved more than one times, the low temperature impact toughness of the joints by laser-MAG hybrid welding can be improved over 50% than that of conventional MAG welding joints, and the width of coarsegrained zone of hybrid welding joints is thinner than that of MAG welding joints.     

TA2薄壁钛管双TIG焊温度场和残余应力分布对接头组织性能的影响

针对纯钛TA2薄壁管的钨极氩弧焊(TIG)高速焊接时出现的咬边、驼峰等成形缺陷,以及焊接效率低等问题,提出采用双TIG焊接工艺,可有效提高焊接速度,改善焊缝成形的解决措施。同时采用ABAQUS对两种焊接方法建立焊接热弹塑性有限元模型,对比分析焊接温度场和焊后残余应力分布,并进一步对焊接TA2薄壁钛管进行显微组织分析及力学性能测试。试验结果表明:模拟所得的两种接头的焊缝轮廓尺寸与实际接头相近,双TIG焊接时焊缝中心温度低于TIG焊接,且双TIG焊缝附近Von Mises应力大于200 MPa的宽度小于TIG焊缝,焊后稳态时焊缝中心的Von Mises应力相近。双TIG焊缝中心及热影响区显微组织比TIG焊细小,两种接头的各项力学性能和耐海水腐蚀性能均满足相关标准要求。φ19 mm×0.7 mm的TA2钛管在获得良好焊缝成形的条件下,采用双TIG焊接工艺的焊接速度可达5 m/min。与TIG焊接工艺相比,生产效率大为提高,基本实现焊缝零缺陷。     

Explosively welded copper‐stainless steel bimetal and an example of its application

Summary

Friction welding was carried out under various welding conditions using high strength 7075 aluminium alloy; an investigation into the structure and the mechanical properties of joints thus obtained leads to the following conclusions: The fibrous structure at the heat affected zone changed to align in the direction of flash expulsion and the fibrous structure at the weld zone disappeared and a non-directional fine grain structure was evident. The hardness at the weld interface had a lower value than that of the base metal and an even more softened zone than the weld interface was noted at the heat affected zone. The hardness values at the weld interface and the softened zone were seen to recover after friction welding due to natural ageing but did not recover fully. Both the values of the tensile strength and the elongation declined compared with the base metal in joints made under the conditions that gave the maximum value of tensile strength; the former was 81% and the latter was 83% that of the base metal. The joint impact value of a specimen with a notch on the weld interface was 73% that of the base metal.     

7A52铝合金电子束焊接参数及性能

对20mnrl厚7A52铝合金板材采用试件法进行电子束焊接,确定了焊接参数并对力学性能进行分析．结果表明,采用加速电压60kV,电子束流120mA,聚焦电流763mA,焊接速度800mm／min,可得到良好的焊缝表面．电子束流增大焊缝深宽比显著增加,聚焦电流微小的数值变化可引起焊缝形状突变．接头焊缝区晶粒细小均匀,抗拉强度为母材的87％,焊缝维氏硬度最低值为母材的61％,焊缝冲击韧度为母材的95．4％,表明了电子束接头的性能很高．     

TC4合金TIG焊接头组织转变与力学性能分析

针对TC4合金TIG焊接头微观组织特征以及焊接过程中的组织转变规律进行了研究,并对接头力学性能进行了分析.经历TIG焊接热循环之后,焊缝及热影响区粗晶区晶粒严重粗化,热影响区晶粒尺寸具有突变特征,过渡区组织呈带状分布,不存在明显的细晶区.升温过程中(α+β)→β转变过程包括两个阶段:原始β→高温β转变和原始α→高温β转变,而且在原始α→高温β转变开始之前,原始β→高温β转变已经完成.冷却过程中在β→α'转变区间冷速较慢时,α'相首先在高温β晶界上形核,并向晶内生长,生成针状α';在快速冷却时,α'相在晶内大量形核,形成"筐篮"组织.硬度测量结果表明,粗晶区部位存在一个软化区;接头抗拉强度与母材接近,接头性能优异.

Abstract：

The microstructure and phase transformation of TC4 alloy weld joints during TIG welding were investigated. The mechanical properties of the welded joints were also tested. When the TC4 alloy was heated by TIG arc, grains in the weld bead and heat affected zone (HAZ) were badly coarsening. The grain size in HAZ has mutant character. The microstructure in the transition region presented zonal distribution. There was no obvious fine grained region. In temperature-rise period, the transformation of (α + β)→β was divided into two processes which included the original β→ high-temperature β and the original α→ high-temperature β. And the previous phase transformation was finished before the next starting. In the cooling process, slowly cooling rate introduced α' phases nucleating at the high-temperature β grain boundary in the β→α transform temperature range. The α' martensite grew up into the center of the β grains and generated acicular martensite. With quicker cooling rate, large numbers of α' phase nucleated in the high-temperature β grains and generated orthogonally oriented martensites. Hardness measurements show there is a softened zone in HAZ. Tensile strength of welded joint was approximate with the base metal. And the properties of the welded joints were good.     

6N01铝合金水冷MIG焊接头组织和性能

针对6N01铝合金熔化焊接头软化问题,研究了水冷对MIG焊接头组织和性能的影响,并与自然冷却条件下接头进行对比.金相试验结果表明,水冷使填充和盖面焊道部分熔化区变窄,焊缝近熔合线的柱状晶区变宽,焊缝内部等轴晶细化;显微硬度试验结果表明水冷条件下接头软化区范围明显变窄且硬度提高;软化区TEM观察显示水冷减少了β'析出相长大;水冷还提高了MIG焊接接头屈服强度和抗拉强度.结果表明,水冷能优化6N01铝合金MIG接头组织并提高力学性能.     

Laser welding of AZ61 magnesium-based alloys Laser welding of AZ61 magnesium-based alloys

0IntroductionMagnesium alloys containing small amounts of alloyedelements such as aluminum, manganese, zinc, zirconium,etc., have strength equaling that of mild steels. They dis-play high strength to weight ratio making them materials ofchoice whenever weight reduction is important or when it isimperative to reduce inertial forces (for rapidly moving ma-chine parts). Magnesiumalloys also have good castability,excellent recyclability and price competitiveness. Thereforethey are more and more wi…     

Laser welding of AZ61 magnesium-based alloys

Laser welding of AZ61 magnesium alloys was carried out using a CO2 laser welding experimental system. The welding properties of AZ61 sheets with different thickness were investigated. The effect of processing parameters including laser power, welding speed and protection gas flow was researched. The results show that laser power and welding speed have large effect on the weld width and joint dimensions. Protection gas flow has relatively slight effect on the weld width. The property test of three typical joints indicates that microhardness and tensile strength in weld zone are higher than that of AZ61 base metal, Joints with good appearance and excellent mechanical properties can be produced using CO2 laser welding method. The microstructure with small grains in weld zone is believed to be respoasible for the excellent mechanical properties of AZ61 joints.     

Experimental and numerical investigation on combined girth welding of API X80 pipeline steel

Abstract

API X80 pipeline steel is widely used in natural gas and oil transportation. In this study, X80 pipeline steels with 18.4?mm thickness and 1219?mm diameter, made in China, were welded by a combined girth welding technology. Experimental results showed that microstructures in weld metal and coarse grain heat affected zone are mainly composed of coarsening bainite grains with dimensions of 20–50?μm, and Vickers hardness in weld seam is lowered by the seven-pass welding process. Simulated results illustrated that repeatedly thermal cycles imposed by the combined multipass girth welding process easily result in softened weld joints. The predicted microstructures, phase compositions and hardness in weld metal are in agreement with the measured ones. The results could be applied to optimise this combined girth welding process and improve the weld quality of API X80 pipeline steel and even higher grade pipeline steels.     

异质钛合金线性摩擦焊接头微观组织与显微硬度分析

选用优化的工艺参数对TC4/TC17异质钛合金进行线性摩擦焊及测温试验.焊后利用光学显微镜、扫描电镜及显微硬度仪等对接头微观组织及显微硬度进行分析.结果表明,线性摩擦焊接过程中界面温度超过1 200℃、超过β相变温度,在焊后冷却过程中发生再结晶,产生细小针状组织.界面混合区再结晶组织有等轴化甚至球化现象.TC4侧热力影响区由被拉长的α相及破碎的β相组成,TC17侧热力影响区的α相和β相被拉长细化.TC4侧热力影响区组织发生应变强化,TC17侧热力影响区靠近焊缝侧发生一定的软化现象,靠近母材侧强化现象明显.     

风力发电机电机转子焊接工艺

针对轴材25CrMo和辐板Q345D,采用焊条电弧焊-气体保护焊复合焊方法,J507R打底层,ER50-6填充盖面、预热温度250℃、层间温度300℃、550℃/3h焊后热处理缓冷等工艺制备完整的焊接接头。通过拉伸试验、弯曲试验、冲击试验、维氏硬度试验以及观察分析焊接接头显微组织和冲击断口形貌进行研究,结果表明,采用该焊接工艺获得的焊接接头具有良好的焊接质量,为25CrMo和Q345D焊接的材料选择、工艺制订提供参考。     

高强度钢差厚板激光拼焊焊缝成形及组织分析

选取2.0 mm,1.5 mm厚的HSA340板材和0.7 mm厚的H340LAD Z板材,按强度相近厚度不同原则两两搭配进行激光拼焊.焊后选取具有代表性的焊缝横截面进行金相组织检验,并对焊缝接头各区域进行硬度测量,分析了激光焊缝接头各区域金相组织及其硬度的变化.结果表明,差厚板激光拼焊过程中,母材散热情况不同,会造成焊缝金相组织在各自靠近母材的局部区域有很大差异;激光拼焊板的热影响区宽度窄,与母材及焊缝间有明显的界线,生成的组织细密;焊缝及热影响区的硬度值均大于母材;合理调整激光光束的入射位置和入射角度,可以显著改善焊缝成形,提高拼焊板的接头质量.     

TC17钛合金线性摩擦焊接头组织及力学性能分析

针对固溶时效态TC17钛合金焊态及焊后热处理态线性摩擦焊接头，进行显微组织及力学性能对比分析. 结果表明，焊态时焊缝组织发生了回复与再结晶，由于焊后冷却速度较快，生成了亚稳定β相，焊缝区发生了软化；热力影响区组织沿受力变形方向拉长、细化、交替呈带状分布，加工硬化程度较高，显微硬度明显高于其它区域；热影响区由于二次次生α相基本溶解于亚稳定β相，导致显微硬度显著降低. 经过焊后热处理，亚稳定β相发生时效分解，析出了弥散程度更高的针状次生α相使得焊接区硬度大幅度提高. 由于亚稳定相的生成，焊态接头发生软化，拉伸均断裂在焊缝区，抗拉强度达到母材强度91.8%，断口呈脆性断裂形态；焊后热处理态接头由于二次次生α相的析出，起到弥散强化的作用，拉伸试验均断在母材，断口呈典型韧性断裂形态.     

高速列车6005A-T6铝合金型材激光-双丝MIG复合焊

分别利用双丝MIG焊和激光-双丝MIG复合焊进行了高速列车6005A-T6铝合金型材的焊接试验研究,对比分析了两种焊接方法的焊缝成形、焊接变形、接头力学性能及其接头微观组织.结果表明,激光-双丝MIG复合焊接6005A-T6铝合金型材时的焊接速度可达4.5 m/min,焊接过程具有较好的搭桥能力,对接间隙达到1.4 mm时,仍可以获得良好的焊缝成形.当焊接速度大于或等于4 m/min时,复合焊接头的焊接变形量仅为常规双丝MIG焊的40%左右,其抗拉强度达到了母材强度的83%,比常规双丝MIG焊接头的抗拉强度提高了9%左右.     

Application of switch back welding to V groove MAG welding

The formation of stable back beads in a root pass weld during one side multi-layer welding is important to achieve high quality welded metal joints in MAG welding. The authors employed the switch back welding method for V groove joints without backing plates. In this switch back welding method, the torch moves forward and backward with an oscillation frequency of 2.5 Hz. In order to achieve this welding, personal computers control the conventional welding robot, the power source characteristic and the wire feeder unit. During the forward, the torch is weaving on the V groove gap without the weld pool. If the weaving width becomes wider than the proper width, the tip of the wire becomes high and a good back bead cannot be obtained. The weaving width is adjusted so as to get the proper width in the switch back welding. The suitability of the welding conditions for each root gap was verified by observation of the arc, the weld pool and the external appearance of back beads. A good back bead was obtained under V groove welding in 2–4 mm gap.     

3D finite element modeling of the thermally induced residual stress in the hybrid laser/arc welding of lap joint

In this study, a three-dimensional (3D) finite element model is developed to investigate thermally induced stress field during hybrid laser–gas tungsten arc welding (GTAW) process. In the hybrid welding case, we focus on the GTAW process sharing common molten pool with laser beam and playing an augment role in the hybrid welding system. An experiment-based thermal analysis is performed to obtain the temperature history, which then is applied to the mechanical (stress) analysis. A modified material model is used to consider the influence of face-to-face contact between the top and bottom metal sheets in the thermo-mechanical analysis of welding lap joints. Results show that the normal stress components prevail in the weld zone during hybrid welding process, and maximum thermal stress exceeding the yield point of material exists at the heat affected zone (HAZ) near the weld pool. Increasing the welding speed causes the penetration and width of weld bead to decrease, and the thermal stress concentration at the welded joint is also reduced accordingly. After welding and cooling down, longitudinal tensile stress (SZ) and transverse compressive stress (SX) are retained in the formed weld, and the higher longitudinal compressive stress exists around the weld bead. In addition, a series of experiments are performed to validate the numerical results, and a qualitative agreement is achieved. Compared to the welded joint obtained by GTAW and laser welding alone, the residual stress concentration in the weld joint obtained by hybrid laser–GTAW is the minimal one.