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.     

Strength enhancement of autocompleting medium and high carbon steels friction welded joints

An autocompleting friction welding method, which was developed by the authors, is to weld with using a rotating insert piece set between fixed workpieces. The conditions to enhance the strength of the welded joint in an autocompleting friction welding method which involves a rotating insert between the fixed workpieces were determined. The weld faying surface of the fixed specimen had a 10 mm diameter. When MCS joint was made at an insert thickness of 4 mm through a friction pressure of 36 MPa, it did not achieve 100% joint efficiency because the weld interfaces were not completely joined. MCS joint had 100% joint efficiency and fractured on the MCS base metal although the crack was generated at the weld interface, when that was made at an inner groove diameter of 11 mm with the bottom of the grooves for the insert piece (groove bottom thickness) of 0.9 mm or more through a friction pressure of 90 MPa. To obtain a joint with no cracks, MCS joint was made with an inner groove diameter of 12 mm at a friction pressure of 90 MPa. When the groove bottom thickness was 0.75 mm, MCS joint had 100% joint efficiency and the MCS base metal fracture with no crack at the weld interface. When HCS joint was made with an inner groove diameter of 11 mm at friction pressures of 90 and 150 MPa, it did not achieve 100% joint efficiency because the weld interfaces were not joined completely. The weld interfaces of HCS joint at a friction pressure of 120 MPa were completely joined although it did not achieve 100% joint efficiency. To improve the joint efficiency, HCS joint was made with an insert thickness of 5 mm, a groove bottom thickness of 0.64 mm, and an inner groove diameter of 12 mm with a friction pressure of 120 MPa. HCS joint had 100% joint efficiency and fractured on the HCS base metal with no crack at the weld interface.     

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.     

Effect of friction welding condition on joining phenomena and joint strength of friction welded joint between brass and low carbon steel

Abstract

This paper describes the effect of friction welding condition on joining phenomena and joint strength of friction welded joints between copper–zinc alloy (brass) and low carbon steel (LCS). When the joint was made at a friction pressure of 30 MPa with a friction speed of 27·5 s^?1, brass transferred to the half radius region of the weld interface on the LCS side. Then, transferred brass extended towards the almost whole weld interface with increasing friction time. The joint efficiency increased with increasing friction time, and then the joint obtained 100% and the brass base metal fracture when the joint was made with a friction time of 4·2 s or longer. However, the fact that all joints had some cracks at the periphery portion of the weld interface was due to a deficiency of transferred brass at the periphery portion on the weld interface of the LCS side. On the other hand, brass transferred to the peripheral region of the weld interface on the LCS side, and then transferred towards the entire weld interface when the joint was made at a friction pressure of 90 MPa with a friction speed of 27·5 s^?1. The joint efficiency increased with increasing friction time, and it reached 100% at a friction time of 1·5 s or longer. In addition, all joints fractured from the brass base metal with no cracking at the weld interface. To obtain 100% joint efficiency and the brass base metal fracture with no cracking at the weld interface, the joint should be made with opportune high friction pressure and friction time at which the entire weld interface had the transferred brass.     

Nd:YAG激光焊接800 MPa TRIP钢的接头组织与性能

采用Nd:YAG激光对强度为800MPa,厚度为1.2mm的TRIP钢板进行焊接.研究焊接速度对焊缝外观和截面成形的影响及接头的组织特点、硬度、强度和成形能力.激光功率相同,焊接速度较低时焊缝易产生气孔,速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝组织主要由马氏体构成,从焊缝、热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝中出现马氏体,接头的塑性和韧性降低,板材的冲压成形能力下降.     

Friction stir welding of DH36 steel

Abstract

Hot rolled DH36 carbon steel, 6.4 mm in thickness, was friction stir welded at speeds of 3.4 mm s^-1 (8 in min^-1), 5.1 mm s^-1 (12 in min^-1), and 7.6 mm s^-1 (18 in min^-1). Single pass welds free of volumetric defects were produced at each speed. The relationships between welding parameters and weld properties are discussed. Optical microscopy, microhardness testing, and transverse and longitudinal tensile tests have been performed. Bainite and martensite are found in the nugget region of the friction stir welds whereas the base material is comprised of ferrite and pearlite. The maximum hardness is observed in the weld nugget, and the hardness decreases gradually from the weld nugget, through the heat affected zone, to the base metal. Tensile testing also indicates overmatching of the weld metal relative to the base metal. Maximum hardness and longitudinal (all weld metal) tensile strengths increase with increasing welding speeds. Weld transverse tensile strengths are governed by the base metal properties, as all transverse tensile bars fail in the base metal.     

30 mm 7A05铝合金搅拌摩擦焊接头组织及力学性能

采用搅拌摩擦焊方法利用新型搅拌头对30 mm厚的7A05-T6铝合金进行了单道对接,焊后分析讨论了焊缝接头微观组织和力学性能.结果表明,接头焊核区发生动态再结晶,生成细小的等轴晶粒;焊缝两侧热力影响区受机械和热的双重作用,组织存在较大差异,前进侧为窄条状组织,后退侧为扁平状组织;热影响区晶粒粗化;在焊接30 mm板时,工艺参数范围较窄,旋转频率为360 r/min,焊接速度为100 mm/min时,可获得无缺陷、成形好的焊缝;接头抗拉强度为367.7 MPa、屈服强度为280.8 MPa、断后伸长率为14.4%高于母材,接头抗拉强度可达母材的95%.接头显微硬度的分布呈类似W形分布,热影响区软化趋势比较明显.     

35mm厚板铝合金搅拌摩擦焊接头组织和性能

采用搅拌摩擦焊双面焊工艺,对35 mm厚板6005A-T6铝合金型材进行了搅拌摩擦焊接,获得成形良好、表面光滑、无隧道孔和沟槽缺陷的焊接接头.应用光学显微镜、扫描电镜、显微硬度仪及电子拉伸试验机等对搅拌摩擦焊接头组织与性能进行研究.结果表明,接头焊核区组织为细小等轴晶;前进侧出现明显的螺旋纹及清晰的结合线,热力影响区晶粒被明显拉长呈条状组织,热影响区受热晶粒粗大;后退侧未见螺旋纹,晶粒比前进侧细小,过渡区较前进侧宽.在搅拌头旋转频率为650 r/min,焊接速度为200 mm/min工艺条件下接头抗拉强度为213 MPa,达到母材强度的84.8%,断裂起始于焊缝前进侧的热影响区,扩展至双面焊接重合区时,沿着焊缝后退侧热影响区直至断裂;接头显微硬度最低值出现在前进侧热影响区,最低值为50 HV.     

CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.     

Effect of inclination of weld faying surface on joint strength of friction welded joint and its allowable limit for austenitic stainless steel solid bar similar diameter combination

This paper describes the effect of the inclination of the weld faying surface on joint strength of friction welded joint and its allowable limit for austenitic stainless steel (SUS304) solid bar similar diameter combination. In this case, the specimen was prepared with the inclination of the weld faying surface pursuant to the JIS Z 3607, and the joint was made with that diameter of 12 mm, a friction speed of 27.5 s^?1, and a friction pressure of 30 MPa. The initial peak torque decreased with increasing inclination of the weld faying surface, and then the elapsed time for the initial peak increased with increasing that inclination. However, the steady torque was kept constant in spite of the inclination of the weld faying surface increasing. The joints without the inclination of the weld faying surface, which were made with friction times of 1.5 and 2.0 s with a forge pressure of 270 MPa, had achieved 100% joint efficiency with the base metal fracture. Those joints had 90° bend ductility with no crack at the weld interface. The joints with the inclination of the weld faying surface of 0.3 mm (gap length of 0.6 mm), which were allowable distance, was also obtained the same result with this condition. Furthermore, those joints with a friction time of 2.5 s obtained the same result. On the other hand, the joints with the inclination of the weld faying surface of 0.6 mm (gap length of 1.2 mm), which were twice inclination of the allowable distance, also obtained the same result in a friction time of 2.5 s. However, the joints without the inclination of the weld faying surface at this friction time did not obtain the base metal fracture, although those achieved 100% joint efficiency. In conclusion, to obtain 100% joint efficiency and the base metal fracture with no cracking at the weld interface, the joint must be made with the inclination of the weld faying surface, with allowable distance pursuant to the JIS Z 3607.     

Mechanical properties of friction welded joint between Ti–6Al–4V alloy and Al–Mg alloy (AA5052)

Abstract

The present paper describes the mechanical properties of a friction welded joint between Ti–6Al–4V alloy and Al–Mg alloy (AA5052). The Ti–6Al–4V/AA5052–H112 joint, made at a friction speed of 27.5 rev s^?1, friction pressure of 30 MPa, friction time of 3.0 s, and forge pressure of 60 MPa, had 100% joint efficiency and fractured in the AA5052–H112 base metal. The Ti–6Al–4V/AA5052–H34 joint, made under the same friction welding conditions, did not achieve 100% joint efficiency and it fractured in the AA5052–H34 base metal because the AA5052–H34 base metal had softened under friction heating. The joints made at low friction speed or using short friction time showed fracture at the welded interface because a sufficient quantity of heat for welding could not be produced. However, the joints made at high friction speed or using long friction time were also fractured at the welded interface: in this instance, the welded interface also had an intermetallic compound layer consisting of Ti₂Mg₃Al₁₈. The Ti–6Al–4V/AA5052–H34 joint made at a friction speed of 27.5 rev s^?1 with friction pressure of 150 MPa, friction time of 0.5 s, and forge pressure of 275 MPa had 100% joint efficiency and fractured in the AA5052–H34 base metal, although the AA5052–H34 side softened slightly. In conclusion, the Ti–6Al–4V/AA5052–H112 joint and Ti–6Al–4V/AA5052–H34 joint had 100% joint efficiency and fractured in the AA5052 base metal when made under the friction welding conditions described above.     

Effect of friction welding conditions on mechanical properties of A5052 aluminium alloy friction welded joint

Abstract

The present paper describes the mechanical properties of Al–Mg aluminium alloy (A5052) friction welded joints. Two types of A5052 with different tensile properties were used, namely, H112 base metal with 188 MPa tensile strength and H34 with 259 MPa tensile strength. Similar metal specimens were joined using a continuous drive friction welding machine with an electromagnetic clutch to prevent braking deformation. That is, the joints were welded using the 'low heat input' friction welding method developed by the present authors, in which the heat input is lower than in the conventional method. An A5052–H112 joint produced using a friction speed of 27·5 s^?1, friction pressure of 30 MPa, friction time of 2·0 s (just after the initial peak torque), and forge pressure of 60 MPa had approximately 95% joint efficiency. It fractured at the welded interface and in the A5052–H112 base metal. To improve the joint efficiency, an A5052–H112 joint was produced at a forge pressure of 75 MPa, which was the same as the yield strength of the A5052–H112 base metal. It had 100% joint efficiency and fractured in the A5052–H112 base metal. In contrast, an A5052–H34 joint was made using a friction speed of 27·5 s^?1, friction pressure of 90 MPa, friction time of 0·3 s (just after the initial peak torque), and forge pressure of 180 MPa. It had approximately 93% joint efficiency and fractured in the A5052–H34 base metal. This joint also had a softened region at the welded interface and in the adjacent region. To improve the joint efficiency, an A5052–H34 joint was made at a forge pressure of 260 MPa, which was the same as the ultimate tensile strength of the A5052–H34 base metal. Although this joint had a slightly softened region at its periphery, it had approximately 93% joint efficiency. The failure of the A5052–H34 joint to achieve 100% joint efficiency is due to a slight softening at the periphery and the difference in the anisotropic properties of the A5052–H34 base metal between the longitudinal and radial directions.     

钛/铝双面冷弧MIG组合熔钎焊接头组织和性能

采用SAl5183焊丝对TA2钛和5A06铝合金进行了双面冷弧MIG组合焊接.对接头厚度方向不同位置的Ti/Al界面组织特性进行了分析;并对接头抗拉强度进行了测试.结果表明,试验工艺获得的接头中,钛与焊缝形成了平直的结合界面,界面处未发现剥离、裂纹等缺陷.受焊接热输入影响,形成两种不同的Ti/Al界面:接头中上部钛与焊...     

0Cr15Ni5Cu4Nb中厚板锁底结构大功率光纤激光焊接工艺特性

采用大功率光纤激光对7 mm厚度0Cr15Ni5Cu4Nb不锈钢锁底结构实施了焊接试验,通过对不同焊接工艺参数下的接头质量、力学性能、微观组织结构的分析,研究了其焊接工艺特性. 结果表明,焊缝中的主要缺陷是焊接气孔,采用负离焦、高速度的焊接参数能够有效抑制气孔的形成. 焊缝区域硬度有所增加,并且焊缝上部和下部的硬度要高于中部的硬度值,接头的力学性能稳定,焊缝平均抗拉强度为970 MPa,冲击韧性略有降低,为母材的89%. 焊缝组织主要由马氏体、残余奥氏体和δ-Fe组成,焊缝中部δ-Fe要多于上部,马氏体转变不充分,热影响区中主要由晶粒细小的淬火马氏体组成.     

Microstructure and Mechanical Properties for TIG Welding Joint of High Boron Fe-Ti-B Alloy

采用钨极气体保护焊,以基体金属作为焊接填料,可以成功实现对高硼Fe-Ti-B合金的焊接。对焊件的微观结构进行了分析,研究表明,高硼Fe-Ti-B合金的焊接质量良好,焊接接头处不存在裂纹、未熔合、未焊透等缺陷;熔合区和热影响区的微观结构与基体明显不同,但能谱分析表明其化学成分非常均匀。对焊件进行了力学性能测试。测试结果表明,相对于基体材料,焊件的屈服强度略有升高,但抗拉强度降低。尽管如此,焊后高硼Fe-Ti-B合金的抗拉强度高于580 MPa,屈服强度高于400 MPa,焊件的力学性能已达到一个较高的水平。     

镁合金搅拌摩擦焊接技术

对5mm厚镁合金AZ31B板材的摩擦焊接技术进行了试验研究，结果表明：适合其板材的搅拌摩擦焊接的搅拌头，材料为W6MoSCr4V2高速钢，结构为凹面圆台形，根部直径5．5mm，端部直径为2．5mm，轴肩尺寸为12mm，长度为4．7mm。镁合金搅拌摩擦焊接头的抗拉强度可达母材的90％，延伸率可达母材的50％。搅拌摩擦焊接头焊合区为动态再结晶组织，在接头前进边焊合区与母材有明显的分界线，返回边过渡区有金属微熔的迹象。     

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.     

TC4钛合金水下湿法激光焊接焊缝组织与性能

使用光纤激光器对TC4钛合金进行了水下湿法激光焊接试验,通过在TC4表面预置焊接辅助剂实现了增加水下湿法焊接熔深的同时对焊缝进行保护的目的. 对焊缝的微观组织和力学性能进行了分析,结果表明,预置焊接辅助剂后,焊缝熔深增大,焊接阈值增加,焊缝中裂纹减少. 焊缝中心主要由初生α和马氏体组织α'相组成,在熔池底部还保留有粗大的β晶界,焊缝由于水的急冷作用出现了淬硬组织,显微硬度远高于TC4母材. 水下焊接拉伸试验试件均断裂在焊缝处,焊接接头平均抗拉强度值为439 MPa,呈现为脆性断裂.     

TiNi形状记忆合金与不锈钢激光焊接头裂纹分析及防止措施

采用激光焊对TiNi形状记忆合金与不锈钢异种材料进行焊接,用扫描电镜和激光共聚焦显微镜研究了TiNi合金/不锈钢接头裂纹及断口特征,分析了焊缝裂纹的形成机理,并提出了防止裂纹的措施.结果表明,裂纹多以微裂纹的形式出现于焊缝中心和TiNi合金侧熔合区.焊缝中存在大量的脆性化合物是产生裂纹的内在原因,接头受到拉伸应力是产生裂纹的必要条件,焊缝裂纹是二者共同作用的结果.通过焊接区加镍和钴中间层材料、改变激光光斑位置、焊接区施加轴向力及优化激光焊接参数的方法均能在一定程度上改善焊缝金属的裂纹敏感性,其中加金属中间层效果更为明显,加镍和钴中间层后,接头抗拉强度分别达到372和347 MPa,比未加中间层的接头的抗拉强度分别提高98.9%和85.6%.     

1420铝锂合金激光焊接接头拉伸性能分析

针对2.5 mm厚1420铝锂合金板材,研究了修饰焊和焊后热处理对激光焊接接头拉伸性能的影响,并且分析了轧制方向对接头拉伸性能的作用.试验结果表明:修饰焊对接头拉伸性能影响不大,但可明显改善焊缝成形,减少焊缝缺陷;热处理工艺对接头的拉伸性能影响最大,能显著提高接头的抗拉强度;轧制方向对接头的拉伸性能没有影响.