Dissimilar friction welding of aluminium alloys to other materials

Friction welding makes it easier to set welding conditions and also confers greater reproducibility than other welding processes. Through being a solid-phase process, friction welding moreover makes it relatively easy to join dissimilar materials. Other advantages of friction welding include good operability, the lack of any need for special skills, and a convenient capability for incorporation in assembly lines without showers of sparks and similar hazards being generated. Friction welding is therefore extensively used in a wide variety of industries, such as automotive engineering, printing, etc. Joining of dissimilar materials as a characteristic friction welding application has been well researched,¹ reported,² and thoroughly explained with reference made to practical examples.³ In the current situation of materials development advancing apace in pursuit of various objectives, available data relating to joining of dissimilar materials remains scant. To meet resource- and energy-saving objectives, machinery and plant, transport machinery, etc. are now required to embody lighter weight in a well-established trend that can only serve to expand the use of light metals. Compared with ferrous metals, however, friction welding of light metals has been little documented.     

Dissimilar friction stir welding between 5052 aluminum alloy and AZ31 magnesium alloy

Dissimilar friction stir welding between 5052 Al alloy and AZ31 Mg alloy with the plate thickness of 6 mm was investigated. Sound weld was obtained at rotation speed of 600 r/min and welding speed of 40 mm/min. Compared with the base materials, the microstructure of the stir zone is greatly refined. Complex flow pattern characterized by intercalation lamellae is formed in the stir zone. Microhardness measurement of the dissimilar welds presents an uneven distribution due to the complicated microstructure of the weld, and the maximum value of microhardness in the stir zone is twice higher than that of the base materials. The tensile fracture position locates at the advancing side (aluminum side), where the hardness distribution of weld shows a sharp decrease from the stir zone to 5052 base material.     

Lapped friction stir welding between ductile cast irons and stainless steels

This study investigated the influence of preheating temperature and welding speed on the microstructure of dissimilar lapped friction stir welding (FSW) of ductile cast iron FCD450 and 304 stainless steel. The stainless steel was placed on FCD450, and then FSW was carried out at a tool rotational speed of 200, 400, and 600 rpm and welding speed between 1 and 10 mm/s. Preheating was conducted at 573 and 773 K. Martensitic structure was formed in HAZ of FCD450 without the preheating, while the preheating resulted in the formation of a pearlite structure. Even when the preheating was employed, however, stir zone (SZ) of FCD450 had the chill structure at a lower welding speed, because the SZ temperature exceeded the eutectic temperature. Formation of the chill structure in the SZ could be prevented at a higher welding speed. This study showed that FSW would be available as a dissimilar welding method between ductile cast iron and stainless steel.     

Dissimilar spot welding of aluminium alloy and galvannealed steel by metal flow-application of friction anchor welding to aluminium alloy and Zn-coated steel

ABSTRACT

Lap joints of an upper Al alloy (1.0-mm-thick A5052) and lower hot dip galvanized steel (1.2-mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding.’ As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.     

High temperature wear and friction properties of duplex surface treated bearing steels

Duplex treatments by thermo reactive diffusion (TRD) chromizing and puls plasma nitriding were carried out on AISI 52100 and 8620 bearing steels. Tribological behaviors of TRD chromized and duplex treated bearing steels were investigated against Al₂O₃ ball in ball-on-disc system at room temperature and 500 °C. The samples were pack chromized in a furnace at temperature of 1000 °C for 5 h. After chromizing, the samples were puls plasma nitrided for 5 h at 500 °C. The coated steels were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scratch and microhardness testing. Plasma nitriding of chromized steels increased the total thickness of the compound layer. The subsequent plasma nitriding increased the surface hardness to 2135 HK_0.025 due to the formation of CrN and Cr₂N. The surface hardness and scratch resistance of coating can be increased with duplex treatment of chromizing followed by plasma nitriding, resulting in high wear resistance. Tribological tests indicated that puls plasma nitriding process decreased the coefficient of friction values and wear rate of the chromized steels at room temperature and 500 °C. Also, examination of the worn surface of the samples showed that particularly at high temperature, the oxidized compact layer occurs and tribo-oxidation played an important role in oxidation behaviour of the steels after the duplex treatment.     

搅拌摩擦焊应用及焊接设备简介

介绍了搅拌摩擦焊的工艺过程，分析了搅拌摩擦焊焊缝及焊接过程的优缺点。对搅拌摩擦焊的应用和常用搅拌摩擦焊设备作了简要的描述。     

牙轮扩孔器异材钢焊接工艺

牙轮扩孔器是海上石油钻井中的关键设备,由于受海底地质条件的影响,设计选用35CrMo和35CrMo、35CrMo和35、35CrMo和Q235-B、35和35钢焊接结构,由于多种材质组合焊接,结构焊接性能很差,容易形成热裂纹。我们经过认真研究和试验,制定了正确的焊接工艺,保证了产品质量。     

Dissimilar spot welding of aluminium alloy and hot dip galvanised steel by metal flow: application of friction anchor welding to aluminium alloy and Zn-coated steel

Lap joints of an upper Al alloy (1.0 mm-thick A5052) and lower hot dip galvanized steel (1.2 mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding’. As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.     

High strength lap joint of aluminium and stainless steels fabricated by friction stir welding with cutting pin

Abstract

Dissimilar lap joints of aluminium and stainless steel were first friction stir welded by the tool with a cutting pin. The results showed that sound joints could be obtained by this method. When the pin was inserted into the lower steel sheet, macrointerlocks were formed by the steel flashes plugging into the upper aluminium at both sides of the nugget bottom. At the aluminium/steel interface, a thin intermetallic compound (IMC) layer and the mechanical bonding of microinterlocks were formed. In addition, the aluminium near the interface was also strengthened by grain refinement and IMC particles. Therefore, the beneficial effect of the macrointerlocks provided by the steel flashes was removed, the shear strength of the joint reached 89·7 MPa, which was even higher than that of the base metal of aluminium.     

Metallurgy of arc welding of structural steels and welding materials

To improve the formation of the welded joint in narrow-gap welding, investigations were carried out into the method of welding with double modulation of the electrode wire feed rate and pulsed feed of the welding arc.     

Repair welding process of friction stir welding groove defect

The groove defect formed in the friction stir welding dramatically deteriorates weld appearances and mechanical properties of the joints owing to its larger size and penetration. Therefore, the friction stir repair welding was utilized to remove such a groove defect, and the focus was placed on the mechanical properties and microstructural characteristics of the repair joints so as to obtain an optimum repair welding process. The experimental results indicate that the groove defect can be removed by friction stir repair welding, and the offset repair welding process is superior to the symmetrical repair welding process. In the symmetrical repair welding process, a large number of fine cavity defects and an obvious aggregation of hard-brittle phase Al2Cu occur, accordingly the mechanical properties of the repair joint are weakened, and the fracture feature of repair joint is partially brittle and partially plastic. A good-quality repair joint can be obtained by the offset repair welding process, and the repair joint is fractured near the interface between the weld nugget zone and thermal-mechanically affected zone.     

搅拌摩擦焊接技术的研究进展和应用

搅拌摩擦焊是一种新型固相塑化焊接方法,可以有效地避免氧化和蒸发,焊后冷却过程中不出现热裂纹,焊缝区晶粒得到细化,优化了接头各项性能,同时焊接过程不需要填充金属,不产生火花、飞溅、烟雾、弧光等,是一种高效、节能、优质、简单、无污染的焊接工艺.介绍了搅拌摩擦焊的原理、焊接工艺特点、搅拌摩擦焊的最新发展情况及其应用.     

Study of friction welding of polyethylene

The technologies of intermediate coating and diffusion welding of standard columnar laboratory specimens of the joint of the austenitic steel and titanium alloy are well-tested. Materials for the intermediate coating are chosen. Tensile tests on the welded joints are carried out at the temperature of 18–20°C. The technology of copper coating on steel and niobium coating on titanium is the most prospective.     

Thermal modelling of friction stir welding

The objective of the present work is to present the basic elements of the thermal modelling of friction stir welding as well as to clarify some of the uncertainties in the literature regarding the different contributions to the heat generation. Some results from a new thermal pseudomechanical model in which the temperature-dependent yield stress of the weld material controls the heat generation are also presented.