Hideaki Shirai

Development of joining process between aluminium alloy and stainless steel by using plastic flow in automotive parts

In recent years, a lot of process innovations are strongly required for cost and weight reductions in addition to upgrading driving performance and reducing greenhouse grasses in automotive industry. In case of manufacturing automotive parts, a number of materials are used to satisfy their high accuracy and cost reduction. Dissimilar metal joint such as combination of aluminium alloy and austenitic stainless steel is increasing to apply them based on this background. In this joint, an index to guarantee the quality is indispensable, because the formation of intermetallic compounds introduces brittle fracture at the interface between two metals. It is described that plastic flow is applied for dissimilar metal (aluminium alloy and stainless steel) joint in this paper. Based on this research, it is possible to control the break point by forming projection on aluminium alloy. Projections are formed to promote the plastic flow and they are formed by keeping aluminium alloy on softening temperature. It is clear that joint boundary is composed of two reaction layers, one contains Al–Fe–Si–O and the other contains (Fe–Cr–Ni) Al3 intermetallic compound. The new process described in this paper is available for application to production line of various precise sensors for automotive parts.

The effect of beam profile at a focal point on welding deformation. A study of the deformation behaviour by laser welding at micron or submicron level in automobile parts

Abstract Due to a growing awareness for the environment, demands for functions which enable cleaner exhaust emissions and lower fuel consumption have increased in the field of automotive components. In order to manufacture automotive components that meet these demands and still remain competitive, it is vital to develop high-precision processing technologies for realising new functions. One technique which has been receiving attention is laser processing.1,2 Laser welding has a higher energy density and hence induces much less welding deformation than arc welding. However, even this degree of deformation is too significant to ignore in welding at micron and sub-micron levels (which is the subject of this study). Also, since the types of lasers used in laser welding vary greatly, an understanding of the characteristics between laser energy distribution (the beam profile) and welding deformation is necessary to improve precision in processing. For example, by examining the effects of different beam profiles at the focal point on welding deformation, it will be possible to obtain a beam profile and enable the reduction and control of welding deformation at the sub-micron level.

Reduction of welding deformation by the twin beams method. A study of deformation behaviour due to laser welding of automotive parts at micron or submicron level

Abstract Amid growing concern over the global environment, manufacture of environmentally friendly automotive parts that provide cleaner exhaust gas emissions and improved fuel efficiency is seen as an important engineering task. To develop automotive parts which meet these requirements, it is necessary to achieve a processing accuracy in a range of several microns to submicron level. Production technology in welding and joining, including laser processing, has also been intensively researched from this perspective. Figure 1 gives typical examples of the accuracy requirements extending to specific automotive parts.

Analysis of bending deformation behaviour during circumferential welding of cylindrical parts: study of deformation behaviour at micron to sub-micron level of laser-welded automotive parts

Amid the increasingly rigorous regulatory environment now surrounding the manufacture of motor vehicles alongside the development of progressively more competitive automotive parts, extremely important aspects of advanced parts processing technology are not only to achieve high quality enhancement and reduced manufacturing costs, but also to seek differentiation through efforts to elicit new component functions. At the level of product features, these developments are now translating into needs such as high precision, miniaturisation, high performance, etc. as well as spurring the addition of new functions to automotive parts addressing these needs. Much greater emphasis is also now being placed on higher-quality dimensional accuracy. Recent years have seen more widespread applications of laser welding as an effective processing technology able to meet these needs. Figure 1 shows trends in application of laser welding technology to automotive parts over recent decades. The period of the 1970s to late 1980s saw arc welding being applied in the manufacture of large structures and large actuators at an accuracy level ranging from 1000 μm to 100 ìm, whereas the 1990s ushered in more widespread applications of laser welding as an effective technique for low-distortion micro-region joining of parts. With the proliferation of automotive technologies such as EFI (electronic fuel injection), laser welding from the latter half of the 1990s was mostly focused on product miniaturisation and manufacturing cost reduction. Laser welding has therefore seen rapid advances as a processing technology in this area. Laser welding generally provides higher energy density and lower distortion than arc welding. The processing mechanism per se, however, is much like that of arc welding. Previous research has thus far extensively addressed distortion prevention methods for control of welding distortions in conventional arc welding. These research efforts have led to the proposal of methods involving the application of preheating, restraining devices etc., as well as methods intended to reduce general deformation by straightening after welding. 5 Other proposals include methods involving the application of multiple heat sources and methods for control of welding distortions based on the elaboration of novel welding procedures. The research studies so far conducted, however, have mostly sought to address the deformation generated in the final state after welding is completed, with the deformation generated during the welding process itself being little studied. This particularly concerns circumferential welding of pipe-shaped cylindrical parts that involve a mixed pattern of longitudinal shrinkage, transverse shrinkage, and angular distortion. Although the residual deformation generated in the final state has been to some extent previously reported, the continuous deformation behaviour of such cylindrical parts has been poorly documented. Consideration has been further given to the development of welding distortion control methods based on comprehensive restraint as well as to straightening of cylindrical parts after welding is completed. It is now important, however, to elaborate a post-welding concept of total accuracy covering welding-induced distortion being added to assembly accuracy before welding starts. In the current situation of an overall view being taken of deformation behaviour throughout the welding process as a whole, the purpose of this study is to ensure effective control of welding distortion at micron to sub-micron level after welding of automotive parts required to have Welding International 2004 18 (8) 626–634 Selected from Quarterly Journal of the Japan Welding Society 2003 21 (3) 389–396; Reference QJ/03/3/389; Translation 3283