铝合金无减薄搅拌摩擦焊工艺优化及特征分析

为提高无减薄搅拌摩擦焊接头力学性能,基于响应面法对参数进行优化,建立了响应面模型,并对模型进行回归分析. 结果表明,无减薄搅拌摩擦焊是成形优良的焊接工艺,而且焊接参数对接头拉伸性能影响明显,其中主轴转速及焊接速度对其影响更为显著. 在无缺陷条件下,提高主轴转速的同时选取适中的焊接速度,以得到性能更优的焊接接头. 焊接参数为主轴转速1 000 r/min,焊接速度200 mm/min、轴肩下压量0.25 mm时,接头的抗拉强度最大为363 MPa,为母材的94.3%,断后伸长率11.2%. 而且相比于常规搅拌摩擦焊,无减薄搅拌摩擦焊在厚度方向上的性能更加均匀.     

Development of autocompleting friction welding method

Abstract

This paper describes an autocompleting friction welding method that was carried out to weld with an insert piece set between fixed base metals. The base metal was low carbon steel, and the faying surface of the fixed specimen had a 10 mm diameter. The effect of the thickness of the insert piece (insert thickness) on the joining phenomena was investigated. When the insert thickness was 3˙2 mm and the friction welding conditions were a friction speed of 27˙5 s^–1 and friction pressure of 36 MPa, the insert piece had a shear fracture toward the circumferential direction in the peripheral portion of the weld interfaces by the initial peak produced during the friction process. The joint also had cracks at the adjacent region of the weld interfaces, although it had the same tensile strength as the base metal. On the other hand, the joint made using the insert piece with a groove on its peripheral portion had the same tensile strength as the base metal, where it fractured. This joint also had 90° bend ductility without cracks. In this case, the optimum insert thickness was 4˙0 mm, and the thickness at the bottom of the grooves (groove bottom thickness) was 1˙2 mm with an 11 mm inner groove diameter, and the friction welding conditions were a friction speed of 27˙5 s^–1 and friction pressure of 36 MPa. In conclusion, a sound friction welded joint was made by an autocompleting friction welding method.     

基于响应面法7A52高强铝合金FSW接头抗拉强度预测及优化

为了研究7A52铝合金搅拌摩擦焊的焊接速度、搅拌头转速及轴肩压深对接头抗拉强度的影响,采用响应面法的中心复合试验设计法设计20组试验,并建立抗拉强度响应函数关系式. 为了验证响应函数关系式的精确性,通过方差分析和回归分析确定该回归模型为显性,相关性系数R2的偏差为3.17%. 通过单一焊接参数因素和双因素焊接参数对抗拉强度的影响分析,进一步验证了模型的准确性,最后通过拉伸试验验证. 结果表明,基于响应面法拟合的搅拌摩擦焊焊接速度、搅拌头转速及轴肩压深与接头抗拉强度响应函数关系式能精确的预算不同焊接参数组合所对应的接头抗拉强度,并获得接头最佳参数组合为焊接速度110 mm/min、搅拌头转速1 436 r/min和轴肩压深0.55 mm,得到最大预测抗拉强度为380 MPa.     

ZK60镁合金自持式搅拌摩擦焊工艺

采用直径为16 mm且表面刻有逆时针旋转的螺旋槽的轴肩,直径为6 mm的圆柱形光面搅拌针且沿长度方向加工三个对称平台的自持式搅拌摩擦焊搅拌头,成功进行了3 mm厚ZK60镁合金薄板自持式搅拌摩擦焊,研究了焊接参数对接头表面成形、缺陷的形成及力学性能的影响。研究结果表明,搅拌头旋转速度为600r/min不变,焊接速度较低时,接头上、下表面产生沟槽缺陷,增大焊接速度获得表面无缺陷的接头,过分增加焊接速度,在前进侧和后退侧分别形成线状缺陷和孔洞缺陷,接头的力学性能随焊接速度的增大线增大后减小;采用焊接速度为400 mm/min不变,采用较低的搅拌头旋转速度时,接头表面鱼鳞纹均匀、成形美观、接头表面和内部均无缺陷,旋转速度过分增大,鱼鳞纹粗糙,在前进侧和后退侧接头内部分别产生线状缺陷和孔洞缺陷,接头力学性能随搅拌头旋转速度增大而减小。接头最大的抗拉强度为270 MPa,断后伸长率为8. 92%,接头强度系数达到87%。     

304不锈钢薄板列置双TIG高速焊缝组织与性能

相比常规速度不锈钢焊接,高速焊接过程中焊缝金属的凝固过程及组织形态将会发生变化,从而影响焊缝组织和性能. 对1.2 mm厚304不锈钢薄板对接,采用列置双TIG焊在焊接速度为3.0 m/min时获得了良好焊缝成形,并与常规速度单TIG焊接工艺相比,采用非标准拉伸试样测试了焊缝性能,并分析了其组织. 结果表明,高速双TIG焊接焊缝中心生成等轴晶,两侧树枝晶未形成对向生长的定向晶粒,焊缝抗拉强度及断后伸长率略低于母材;相比常规单TIG焊接工艺,高速双TIG焊接热影响区晶粒平均直径降低了10.3%,但焊缝中心晶粒平均直径增大了12.9%;焊缝抗拉强度和断后伸长率分别提高了4.3%和23.2%,焊缝中心硬度值略高于母材.     

Joint properties and its improvement of high-tensile strength steel joint by autocompleting friction welding method

This paper describes the improvement of properties of a high-tensile strength steel joint by an autocompleting friction welding method that was developed by the authors. The base metal was high-tensile strength steel of 800 MPa class. The weld faying surface of the fixed specimen had a 10 mm diameter, and the effect of the thickness and that at the bottom of the grooves (groove bottom thickness) for the insert piece on the joining phenomena and joint properties were investigated. The value of a circumferential shear fracture (CSF value) was defined and calculated by the ratio between the theoretical and the actual generated friction torques. When the CSF value was lower than 1, the insert piece had the CSF before the friction torque reached the initial peak. Also, when the CSF value was larger than 1, the insert piece had the CSF after the friction torque reached the initial peak. When the joint was made at the insert thickness of 5 mm with the CSF value of nearly 1, it had 100% joint efficiency although it had the softened region near the weld interfaces. The joint had cracks at the weld interface when it was made with friction pressures of 36 and 120 MPa. However, the joint had no crack at the weld interface when it was made with a friction pressure of 90 MPa. When the joint was made at the insert thickness of 4 mm with the CSF value of nearly 1, it had also 100% joint efficiency although it had the softened region near the weld interfaces. However, the softened region at the weld interface of the joint with the insert thickness of 4 mm was lower than that with 5 mm. Also, this joint had 90° bend ductility with no crack at the weld interface. In conclusion, it was possible to make a joint with no cracks for high-tensile strength steel by an autocompleting friction welding method.     

6063-T6铝合金双轴肩搅拌摩擦焊接头组织及力学性能分析

对4 mm厚6063-T6铝合金进行了双轴肩搅拌摩擦焊接试验. 结果表明,双轴肩搅拌摩擦焊可以实现6063-T6铝合金的焊接,得到表面成形良好且内部无缺陷的接头. 接头宏观形貌为哑铃状,其微观形貌分为焊核区、热力影响区、热影响区及母材区. 在搅拌头转速为1 200 r/min,焊接速度为400~700 mm/min的工艺区间内,接头强度呈先升高后降低的趋势,最高可达181.64 MPa,为母材的68.5%,硬度分布呈W状分布,接头断裂位置位于前进侧热影响区,断裂方式为韧性断裂.     

7A52铝合金搅拌摩擦焊工艺优化

接头强度是搅拌摩擦焊接头性能的一个重要指标,通过搅拌头旋转频率、焊接速度和轴肩下压量等焊接工艺参数的不同组合制备了35个7A52焊接试板,对试板进行拉伸试验检测了接头的抗拉强度,建立并分析了焊接接头抗拉强度与焊接工艺参数之间的回归模型,搅拌头旋转频率n,焊接速度v和轴肩下压量d<,ta>单独变化时,接头抗拉强度都有峰值...     

Friction stir welding of aluminium lap joint by tool without probe

A friction stir welding process, with a rotating tool without a probe, was employed and applied to a lap joint of aluminium plate. The thickness of the aluminium plates was 0.5 mm. New tool shapes were developed. The tops of the tool were dome shaped. In this process, the rotating tool was plunged into the aluminium plate. The tool-rotating axis was vertical to the specimen surface, and then moved in the welding direction at a speed of 20 mm/s. Tool rotation speed was 18,000 rpm.

At tool plunge depths of 0.1 mm or over, it was possible to weld the two plates. At tool plunge depth of 0.1 mm, its joint was fractured at the weld interface. At tool plunge depth of 0.2 mm or over, the joints were fractured at the stir zone of the upper plate or the heat affected zone of the lower plate. Based on observation of the hardness profiles and the thickness change of the weld area, controlling factors of the joint strength are discussed.     

Joining phenomena and joint strength of friction welded joint between pure aluminium and low carbon steel

Abstract

This paper describes the joining phenomena and joint strength of friction welded joints between pure aluminium (P-Al) and low carbon steel friction welds. When the joint was made at a friction pressure of 30 MPa with a friction speed of 27·5 s^?1, the upsetting (deformation) occurred at the P-Al base metal. P-Al transferred to the half radius region of the weld interface on the low carbon steel side, and then it transferred toward the entire weld interface. When the joint was made at a friction time of 0·9 s, i.e. just after the initial peak of the friction torque, it had ～93% joint efficiency and fractured on the P-Al side. This joint had no intermetallic compound at the weld interface. Then, the joint efficiency slightly decreased with increasing friction time. The joint had a small amount of intermetallic compound at the peripheral region of the weld interface when it was made at a friction time of 2·0 s. When the joint was made at a friction time of 0·9 s, the joint efficiency decreased with increasing forge pressure, and all joints were fractured at the P-Al side. Although the joint by forge pressure of 90 MPa had hardly softened region, it had ～83% joint efficiency. To clarify the fact of decreasing joint efficiency, the tensile strength of the P-Al base metal at room temperature was investigated, and the tensile test was carried out after various compression stresses and temperatures. The tensile strength of the P-Al base metal has decreased with increasing compression stress at any temperature. Hence, the fact that the joint did not achieve 100% joint efficiency was due to the decrease in the tensile strength of the P-Al base metal by the Bauschinger effect. To obtain higher joint efficiency and fracture on the P-Al side, the joint should be made without higher forge pressure, and with the friction time at which the friction torque reaches the initial peak.     

Properties of as welded and heat treated pure titanium–7075 Al–Zn–Mg alloy friction weld joints

Abstract

The effects of joining conditions and an age hardening post­weld heat treatment (PWHT) at 120°C for 24 h on the tensile strength and metallurgical properties of dissimilar friction joints between pure titanium and age strengthened 7075 Al–Zn–Mg alloy were investigated. Highest strength was achieved using intermediate friction pressure (150 MPa), short friction time (0.5 s), and high upsetting (forging) pressure (400 MPa). The joint tensile strength decreased when the joint diameter was increased from 8 to 16 mm. The joint tensile strength of as welded (AW) dissimilar joints was similar to that of PWHT joints with diameters of 8, 12, and 16 mm. Detailed TEM confirmed that there was a negligible difference in the thickness of the intermetallic layer formed at the dissimilar joint interface for AW and PWHT joints. While the intermetallic phases formed at the joint interface comprised Al₃Ti, τ (Ti₂Mg₃Al₁₈), and Al in AW joints, they consisted of Al+τ or Mg₂Al₃+τ+Al in PWHT joints. Softened regions were generated in 7075 base material immediately next to the interface in AW joints. Post­weld heat treatment increased the hardness of the softened region almost to that of as received 7075–T6 base material in 12 and 16 mm diameter joints. In contrast, the hardness of the softened region in 8 mm diameter joints could not be recovered to that of the as received material. This was a result of overaging and coarse precipitates in the softened region produced during the friction welding operation.     

2205双相不锈钢搅拌摩擦焊接头组织和性能

采用不同搅拌头转速,研究了搅拌头转速对4 mm厚2205双相不锈钢板材搅拌摩擦焊接头组织及性能的影响. 结果表明,当焊接速度为50 mm/min时,搅拌头转速在600 ~ 800 r/min的范围内,均可获得表面成形良好且内部无缺陷的接头.接头搅拌区在动态再结晶的作用下组织得到细化,硬度值较高,热影响区在焊接热作用下组织粗化,硬度值较低.整个接头的铁素体含量在50% ~ 60%范围内,且随着转速的升高搅拌区的铁素体含量有所增加. 当转速为600 r/min时,接头的抗拉强度达到最大824 MPa,为母材的97.3%,断裂位置为接头的热影响区.     

1561铝合金搅拌摩擦焊接过程压力特征及接头组织性能分析

采用恒压力控制方式对4 mm厚1561新型高镁铝合金板材进行了搅拌摩擦焊接试验，并对焊接过程中搅拌头压力特征、接头微观组织以及力学性能进行了研究. 结果表明，焊接下扎阶段下压力呈先上升后下降再上升的趋势. 稳定焊接阶段，由于材料力学性能的周期性变化导致下压力呈近似正弦周期性变化. 固定焊接速度为200 mm/min，当转速低于800 r/min或高于1 800 r/min时，焊缝产生孔洞缺陷. 当转速超过1 000 r/min时，搅拌区产生"S"线. 接头抗拉强度在低转速时主要受接头金属强度影响，高转速时主要受"S"线分布特征影响. 随搅拌头转速的增加，接头抗拉强度先上升后下降.     

2A12-T4/7A09-T6铝合金搅拌摩擦焊搭接接头性能分析

采用不同的搅拌摩擦焊工艺参数对1.2 mm 2A12-T4铝合金搭接4.0 mm 7A09-T6铝合金板材进行焊接试验，对焊后试样进行力学拉伸检测并对焊缝横截面进行微观组织观测. 结果表明，搅拌针从厚板插入薄板的接头力学性能高于从薄板插入厚板，当转速达到800 r/min、焊接速度达到400 mm/min时，焊接接头的抗拉伸载荷达到最高的17 kN，达到薄板2A12-T4铝合金母材的85%. 在焊接速度不变的情况下，随着转速的提升，焊缝横截面的界面曲线长度缩短，而界面长度曲线越短，接头力学性能越好. 试样断口全部出现在薄板一侧的焊缝起始端，断裂机制为混合断裂.     

应变率对无铅焊锡接点力学行为的影响

对150℃条件下经过0,72,288,500 h等温时效的Cu/Sn3.0Ag0.5Cu/Cu焊锡接点试样进行了应变率为2×10^-4,2×10^-2和2 s^-1的拉伸试验,研究了时效时间和应变率对焊锡接点抗拉强度和破坏模式的影响.结果表明,应变率对焊锡接点的抗拉强度有明显强化作用,抗拉强度随应变率的升高而增大.应变率从低到高的过程中,焊锡接点的破坏模式由焊料内部的韧性断裂逐渐转变为界面金属间化合物(intermetallic compound-IMC)层内的脆性断裂.     

铝和不锈钢摩擦焊接界面组织与性能研究

针对6061铝合金与1Cr18Ni9Ti不锈钢异种金属焊接,采用连续旋转摩擦焊接实现铝钢异种材料焊接,并采用SEM、EDS进行组织分析和性能测试。试验结果表明:在旋转速率为600 r/min、顶锻压力为4.5 MPa,顶锻时间为2 s等工艺参数条件下,铝/钢摩擦焊接头结合紧密,界面呈现波纹状;接头抗拉强度可达252 MPa,且拉伸断裂位置发生在铝侧;铝/钢异种材料接头的结合界面两边互有元素扩散,形成厚度小于2μm的金属间化合物层;其显微硬度在界面处发生阶跃变化,且形成金属间化合物的界面处硬度最高达230 HV。     

根部螺纹搅拌针对搭接接头钩状缺陷和性能的影响

选用3 mm厚的7075–T6铝合金为研究对象,研究了根部带有螺纹的搅拌针对搅拌摩擦焊搭接接头钩状缺陷及拉剪载荷的影响. 结果表明,搅拌针上的螺纹可明显改变焊接过程中的材料流动;塑性材料在搭接面上部集中,挤压搭接界面,焊后搭接接头的钩状缺陷向下弯曲;搭接面处焊核区的宽度较搅拌针的直径明显增大. 因搅拌针端部无螺纹,焊接速度较大时接头底部会由于材料无法及时填充而产生孔洞缺陷. 随着搅拌头焊接速度的升高,搭接接头的拉剪载荷先上升后下降,最高载荷在焊接速度为40 mm/min时取得,为23.333 kN.     

5A06铝合金静止轴肩搅拌摩擦焊T形接头组织与性能

采用静止轴肩搅拌摩擦焊方法实现了10 mm厚5A06铝合金T形接头的焊接. 通过低主轴转速匹配高焊接速度与高主轴转速匹配低焊接速度两组不同的焊接参数,结合拉伸试验、宏观与微观金相分析、电子背散射衍射(electron backscattered diffraction,EBSD)分析与扫描电镜(scanning electron microscope,SEM)断口分析,研究了热输入对焊接接头力学性能与组织的影响. 结果表明,在两组焊接参数下均可获得无孔洞缺陷的全焊透T形接头,焊缝表面光滑平整,几乎无减薄发生;热输入不同会改变搅拌针与周围材料的摩擦形式,引起焊缝出现弱结合缺陷,并影响接头抗拉强度; 在高主轴转速匹配低焊接速度时,焊缝中心重叠区顶部易产生弱结合缺陷,导致接头抗拉强度较低,为198 MPa,拉伸试样断裂在筋板. 在低主轴转速匹配高焊接速度时,焊缝无缺陷存在,接头抗拉强度为287 MPa, 拉伸试样断裂在底板.     

7055铝合金搅拌摩擦焊工艺

利用正交试验法研究搅拌摩擦焊工艺参数对4 mm厚7055-T6铝合金对接接头力学性能和显微组织的影响。结果表明:焊接速度对接头抗拉强度影响最大,旋转速度和压入量依次减小;最优参数焊接的试样的抗拉强度为475.5 MPa,接头强度系数0.788;焊缝的显微硬度低于母材,呈"W型"分布;在正弯角约75.4°和背弯角约62.1°时出现开裂。     

Selection guide of insert piece shape for steel joint by autocompleting friction welding method

Abstract

An autocompleting friction welding method, which was developed by the authors, is to weld with using a rotating insert piece set between fixed base metals. This paper describes the selection guide of the insert piece size for steel joints by the autocompleting friction welding method. The base metal was low carbon steel (LCS), and the weld faying surface of the fixed specimen had a 10 mm diameter. The effect of the thickness at the bottom of the grooves for the insert piece (groove bottom thickness) on the joining phenomena was investigated. When the joint was made at a friction pressure of 90 MPa with a friction speed of 27·5 s^?1, the insert piece had a shear fracture towards the circumferential direction (circumferential shear fracture) in the peripheral portion of the weld interfaces by the initial peak produced during the friction process. In this case, the insert piece had the following dimensions: the thickness was 4·0 mm, and the groove bottom thickness was 1·2 mm or over with an inner groove diameter of 11 mm. In particular, the joint with a groove bottom thickness of 1·2 mm had 100% joint efficiency and the LCS base metal fracture with no crack at the weld interface. The value of a circumferential shear fracture (CSF value) was defined and calculated by the ratio between the theoretical and the actual generated friction torques. When the CSF value nearly equalled 1, the joint had 100% joint efficiency and the LCS base metal fracture with no crack at the weld interface.