35#钢摩擦焊多级加压对轴向缩短量及焊后组织的影响

以35#钢为焊接母材,应用连续驱动摩擦焊接方式,采用正交试验的方法并经过极差分析后,探究了中等直径焊件多级加压方式下各工艺参数对轴向缩短量的影响规律,并对焊接接头显微组织及显微硬度进行了分析.实验结果表明,对焊件轴向缩短量影响程度依次为:二级摩擦位移、二级摩擦压力、一级摩擦压力、一级摩擦位移;观察焊接接头显微组织发现焊缝处得到了细小的铁素体与珠光体相互融合的优良组织,焊缝组织达到正火态;通过对焊件焊缝及热影响区显微硬度测试后可以得出,各焊件焊缝的显微硬度值明显高于母材,不同焊接工艺参数组合方式对焊件接头晶粒存在一定影响并直接影响焊件接头硬度.     

热处理对CLAM钢TIG焊接接头显微组织影响

采用TIG焊接方法对中国低活化马氏体钢(CLAM 钢)进行了平板对接试验,分别对焊接接头采用不同温度的焊后热处理,试验温度分别为610,660,710,760,810℃,保温30 min.结果表明,焊后进行热处理与不做热处理两种情况下,CLAM钢焊接接头微观形貌和硬度存在很大不同;随温度增加,焊接接头焊缝中马氏体板条分布及尺寸均匀性得到提高,热处理温度710℃以上时板条均匀性最好,但晶粒尺寸与板条也会随温度升高而长大.焊后热处理使焊接接头各部分硬度随热处理温度的升高而逐渐降低,焊缝金属硬度下降值比母材和焊缝热影响区大得多,尤其在810℃时焊缝金属硬度下降值最大,降至与母材硬度相当.     

ME20M变形镁合金的TIG焊工艺研究

探讨了ME20M变形镁合金TIG焊工艺参数的选择,采用金相显微镜、拉伸试验机以及扫描电子显微镜等表征方法对焊接接头的微观组织、力学性能以及断口形貌等进行了分析.结果发现,焊接电流为80 A时,焊接接头成形较好,焊缝区组织呈细小的等轴晶,热影响区组织较粗大;焊缝区的硬度由于晶粒细化的原因而有所提高,在热影响区则有所下降;拉伸试验表明焊接接头的力学性能低于母材的力学性能,接头抗拉强度约为母材抗拉强度的75%左右.拉伸断口扫描形貌分析表明,断口呈韧-脆混合断裂.     

纯镍直缝焊管不同焊接方法的接头性能对比

采用等离子与等离子+TIG 2种焊接方法获得尺寸为Φ112mm×3.5mm×6 500mm纯镍直缝焊管.分析了焊后接头宏观形貌、微观组织、力学性能及耐蚀性.结果表明:等离子+TIG较等离子接头各区域晶粒尺寸有所粗化;等离子+TIG接头抗拉强度达到母材的85.6%,满足了镍管接头力学性能要求;等离子+TIG焊缝耐蚀性优于等离子焊缝,较母材有所降低;TIG电弧对焊后等离子接头的二次加热使得等离子接头产生了二次重熔效果,消除了等离子接头产生的咬边、气孔等缺陷,提高了焊接速度,获得了均匀、美观的鱼鳞纹状焊缝表面形貌.综合可见,等离子+TIG焊接是纯镍N6直缝焊管焊接的理想方法.     

低合金钢Q345的深熔TIG焊研究

针对8 mm厚Q345低合金钢的深熔TIG焊中焊接电流、焊接速度、保护气体流量对Q345焊缝成型的影响进行了研究,并对成型较好的焊接接头进行了硬度测试和金相观察.试验结果表明,虽然深熔TIG焊在对低合金钢焊接时的焊接参数不稳定,焊接窗口较窄,不易形成良好的焊缝.但在适当的焊接条件下,可以实现深熔TIG焊对8mm厚Q345的一次性单面焊双面成型,焊缝性能较好并且成型良好的焊缝区组织由铁素体和少量针状贝氏体组成,焊缝熔合区和热影响区的硬度较母材上升了50%,无软化现象.具有继续研究深熔TIG焊应用于低合金钢Q345的意义.     

D36高强钢摩擦塞焊焊接接头组织和性能研究

利用自主研发的摩擦塞焊设备对摩擦塞焊圆柱形试样进行试验,试样材料选择D36高强钢,通过温度巡检仪采集焊接过程中温度演化数据,试验后对焊接接头进行宏观形貌、金相组织、硬度以及拉伸性能的研究.结果发现:在焊接过程中,温度先迅速升高,之后缓慢降低,塞孔底部最先升温,温度峰值出现在塞孔侧壁中间处;塞棒端部和塞孔底部带有倒角的试样可以获得无缺陷的焊接接头;焊接接头中母材组织为轧制后的铁素体和珠光体的带状组织,焊缝组织和上部热影响区组织为上贝氏体,而塞孔底部倒角处的热影响区以细小的铁素体和珠光体组织为主;焊接接头的硬度分布一般为母材最低,热影响区次之,焊缝最高;当塞棒端部和塞孔底部的倒角达到4,mm时,摩擦塞焊焊接接头拉伸试验的断裂位置在母材处,保证了焊接接头的拉伸性能.     

大厚度紫铜搅拌摩擦焊接

采用搅拌摩擦焊接方法对厚度为30mm和50mm的T2紫铜板分别进行单面和双面焊接实验,并对焊缝的微观组织与力学性能进行了分析.结果表明:在一定的参数范围内,可获得表面成形美观、内部无缺陷且变形小的对接接头.30mm T2紫铜板单道焊焊后平均抗拉强度为177.2 MPa,达到母材的81.7%,断后平均伸长率为25.4%;焊缝横切面显微硬度分布波动较大,最低值位于前进侧热影响区底部,说明了此处位置是焊缝薄弱环节.     

焊后多次正火对超细晶粒钢热影响区组织与硬度的影响

为研究400 MPa级超细晶粒钢焊接接头热影响区粗晶区的晶粒细化行为,对其空冷与水冷接头均进行了3次焊后正火热处理.组织观察表明:第1次正火后粗晶区晶粒明显细化,但细晶区和母材区的晶粒均比正火前的稍微粗大,第2次与第3次正火并不能进一步细化晶粒;冷却条件对热影响区组织的影响并不十分显著.显微硬度测试表明:第1次正火使接头硬度大幅度降低,甚至低于母材的原始硬度,后续正火对硬度的影响较小;在所有试样中,仅水冷接头第1次正火后的热影响区硬度与原始母材及母材区的硬度接近.由于焊后多次正火并不能使热影响区晶粒进一步细化,反而使其有粗化与软化的趋势,故应避免焊后多次正火处理.     

HRB500E高强度抗震钢筋焊接性能

国内某厂通过铌微合金化和控冷工艺开发试制HRB500E高强度抗震钢筋,采用金相显微镜、维氏硬度计、闪光焊接、疲劳试验机及力学性能测试,对HRB500E钢筋焊接样力学性能、HV5硬度、金相显微组织、焊接接头强度及疲劳强度进行了试验研究。结果表明:焊接前后焊件和母材强度变化小于5 MPa,强度变化不大,焊件拉伸断口远离焊缝,为延性断口,焊接性能良好;在焊接热循环作用下,焊接接头焊缝、热影响粗晶区、热影响细晶区的表层和芯部经历奥氏体化后再结晶,其组织和硬度变化不大;混晶区至母材表层和芯部则经历不完全奥氏体化后的再结晶,母材芯部组织为F+P+B、表层组织为S,表层硬度HV5高于芯部硬度30 HV5,其组织和硬度变化较大;焊接接头的抗拉断负荷从焊缝到混晶区逐渐减小,焊缝和热影响粗晶区的抗拉断负荷比母材的高;采用国际焊接学会推荐的FAT75疲劳设计曲线对钢筋焊接接头疲劳强度设计是安全的。     

SiCp/ZC71镁基复合材料激光焊焊接接头的组织和性能

采用Nd∶YAG激光器对SiCp/ZC71镁基复合材料进行焊接,研究了两种不同焊接工艺条件下激光焊接接头的微观组织和力学性能。结果表明:在两种焊接工艺下,SiCp/ZC71镁基复合材料都获得了较好的形貌,焊缝完全焊透;焊接接头区域SiC颗粒分布均匀,白色的镁的金属间化合物消失了,没有明显的热影响区;焊接接头的抗拉强度相对母材低,显微硬度高于母材,断裂发生在焊缝区域。     

AZ31镁合金氩弧焊接接头组织与力学性能研究

钨极氩弧焊(TIG)为镁合金焊接中最常用的一种焊接方法。本文采用直流钨极氩弧焊对6.0 mm厚AZ31镁合金挤压板材进行了双面焊接实验。采用光学显微镜、扫描电镜、拉伸试验机考察分析了焊接接头显微组织与力学性能。显微组织分析表明,AZ31镁合金直流TIG焊接头由母材、热影响区、焊缝区组成,焊缝组织呈现焊丝熔化后凝固组织;在母材热影响区与焊缝区之间坡口处形成过渡区,晶粒细小,为母材与焊丝的熔合区。采用AZ31焊丝焊接接头平均抗拉强度为241.0 MPa,延伸率为13.8%,分别达到了母材的86.0%和63.6%。焊接接头的断裂均位于热影响区,断口呈现韧脆混合断裂特征。     

Effects of the types of overlap on the mechanical properties of FSSW welded AZ series magnesium alloy joints

The effects of the types of overlap on the mechanical properties of the friction stir spot welding (FSSW) welded AZ series magnesium alloy joints were investigated by microstructural observations, microhardness tests, and tensile tests. The results show that the microstructure of the stir zone adjacent to the periphery of the rotating pin is mainly composed of the upper sheet. The average distance D between the longitudinal segment of the curved interface and the keyhole periphery, the tensile shear force, and the microhardness of the stir zone of the FSSW welded AZ61 alloy joint are the highest in all samples. During FSSW of AZ31 and AZ61 dissimilar magnesium alloys, the irregular deformation of the longitudinal segment of the curved interface appears, while the microhardness of the stir zone is higher when AZ61 alloy is the upper sheet. Moreover, the microhardness of the stir zone increases initially and then decreases sharply in the longitudinal test position.     

Ca对AZ31镁合金CO_2激光焊接接头组织和性能的影响

采用添加填充材料的CO2激光焊接工艺对AZ31镁合金薄板进行焊接,研究了不同Ca含量对焊缝金属的显微组织和力学性能的影响.结果表明:当激光功率为1 500W,焊接速度为3 m/min时,AZ31镁合金CO2激光焊接的焊缝金属中添加一定量的σCa0.19%元素,可以得到成分相对较均匀、组织细小的焊缝.当填充带材为AZC04(焊缝中Cσa=0.19%)时,焊缝区晶粒相对细小,析出相细小弥散,此时焊接接头的力学性能最优,焊接效率基本可达到100%.     

AZ31镁合金板材自动氩弧焊接工艺研究

利用六轴焊接机器人夹持氩弧焊枪进行AZ31镁合金自动氩弧焊接工艺研究,焊后利用金相显微镜、扫描电子显微镜、X射线衍射仪和万能试验机等对焊接接头进行微观组织表征及力学性能测试。结果表明,在焊接电流160 A、焊接速度0.45 m/min、填丝速度0.6 m/min、钨极针与板材距离0.5 mm（前半段）和2.0 mm（后半段）以及保护气体流量16 L/min（正面）和21 L/min（背面）的条件下,能得到外观形貌良好、质量可靠的AZ31镁合金焊接接头。焊接接头的金相组织显示,焊缝区微观组织可清晰地分为母材区,热影响区和熔化区。焊接过程在热影响区和熔化区出现了大量的沉淀相,X射线衍射结果表明,该沉淀相为β Mg17Al12沉淀相。拉伸结果显示,焊接接头的抗拉强度达到了母材的81.02%,在断口观察到了大量的解离面和韧窝的存在,呈现出脆性断裂与韧性断裂相结合的混合断裂特征。     

Development of liquid-nitrogen-cooling friction stir spot welding for AZ31 magnesium alloy joints

A liquid-nitrogen-cooling friction stir spot welding (C-FSSW) technology was developed for welding AZ31 magnesium alloy sheets. The liquid-nitrogen cooling degraded the deformability of the welded materials such that the width of interfacial cracks increased with increasing cooling time. The grain size of the stirred zone (SZ) and the heat-affected zone (HAZ) of the C-FSSW-welded joints decreased, whereas that of the thermomechanically affected zone (TMAZ) increased with increasing cooling time. The maximum tensile shear load of the C-FSSW-welded joints welded with a cooling time of 5 or 7 s was larger than that of the friction stir spot welding (FSSW)-welded joint, and the tensile shear load decreased with increasing cooling time. The microhardness of the C-FSSW-welded joints was greater than that of the FSSW-welded joint. Moreover, the microhardness of the SZ and the HAZ of the C-FSSW-welded joints increased, whereas that of the TMAZ decreased, with increasing cooling time.     

焊接热输入对镁合金与镀铜钢冷金属过渡焊接接头性能和缺陷影响

利用冷金属过渡焊(CMT)对镁合金和镀铜钢异种金属进行焊接,填充材料选择AZ31镁合金焊丝,对焊接接头的显微组织进行检测,分析焊接接头的性能和缺陷。实验结果表明:Cu元素对镁合金在钢表面的润湿铺展起到良好的促进作用,焊接热输入影响Cu元素对镁/钢表面的润湿铺展效果。焊接接头产生富铜区,易产生裂纹,降低了焊接接头强度。经过拉伸测试,在焊接热输入为212. 2 J/mm时,焊接接头强度达到最大值3. 99 k N,但在焊接热输入达到254. 6 J/mm时,焊接强度反而降低,这是由于钎焊区生成了大量的中间层脆性化合物。焊接接头组织中检测到气孔、夹渣和裂纹等焊接缺陷的存在,这与母材表面的氧化膜和焊缝内应力有关。     

Microstructure and mechanical properties of friction-stir welded St52 steel joints

The aim of this work is to investigate the mechanical properties and microstructures of friction-stir welded (FSWed) St52 structural steel joints. In this study, St52 steel plates with a thickness of 4 mm were butt-welded by friction-stir welding (FSW) using a tungsten carbide tool having a conical pin. The microstructure of the welded zone consists of equiaxed fine ferrite, grain boundary ferrite, Widmanstatten ferrite, and aggregates of ferrite + cementite. The microhardness measurements showed that the hardness of the welded zone was significantly higher than that of the base metal. The FSWed St52 joint exhibited a significant strength overmatching in the weld region and a strength performance similar to or slightly higher than that of the base plate.     

2024-T42铝合金点焊接头性能研究

为改善高强铝合金接头连接性能,提高焊接质量,研究了2024-T42铝合金回填式搅拌摩擦点焊(RFSSW)、电阻点焊和铆接3种不同接头的连接性能,采用显微组织观察试验、拉伸试验、拉剪试验和显微硬度试验等方法,对接头组织和性能进行表征与分析.结果 表明:RFSSW接头的力学性能最优,拉剪性能达到7.23 kN,较铆接和电阻...     

Influence of CO2 laser welding parameters on the microstructure, metallurgy, and mechanical properties of Mg-Al alloys

This study investigated the microstructural characteristics, metallurgy, microhardness, and tensile strength of AZ31 and AZ61 magnesium alloy weldments, fabricated in a CO₂ laser welding process with the adjustment of various parameters. The results show that the AZ31 weldment contains equiaxed grains within the fusion zone (FZ). By contrast, the FZ of the AZ61 weldment contains refined cellular grains and the partially melted zone (PMZ) contains bulk grains. We infer that the difference in aluminum content between the two magnesium alloys results in different supercooling rates and solid grain structures. For both weldments, the ultimate tensile strength (UTS) decreases following the CO₂ laser welding process. However, no significant difference is noted between the UTS of the two weldments, suggesting that tensile strength is insensitive to the Al content of the magnesium alloy. The CO₂ laser welding process is shown to increase the microhardness of both magnesium alloys. Furthermore, grain refinement is responsible for the maximum hardness in the FZ of both weldments. The AZ61 weldment has a higher content of Al, resulting in a greater grain refinement.