Marcin Korzeniowski

Using resistance spot welding for joining aluminium elements in automotive industry

The aluminium alloys are more frequently used in automotive industry especially as an alternative material for car-bodies. In this article the comprehensive summary concerning technology of resistance spot welding of aluminium alloys was presented. The welding schedules, electric parameters of welding, electrodes materials and electrodes life time by resistance spot welding aluminium were described. Few examples directly from automotive industry were presented and advantages of aluminium as a material for some vehicle parts were also discussed.

Friction Welding of Aluminium and Aluminium Alloys with Steel

The paper presents our actual knowledge and experience in joining dissimilar materials with the use of friction welding method. The joints of aluminium and aluminium alloys with the different types of steel were studied. The structural effects occurring during the welding process were described. The mechanical properties using, for example, (i) microhardness measurements, (ii) tensile tests, (iii) bending tests, and (iv) shearing tests were determined. In order to obtain high-quality joints the influence of different configurations of the process such as (i) changing the geometry of bonding surface, (ii) using the interlayer, or (iii) heat treatment was analyzed. Finally, the issues related to the selection of optimal parameters of friction welding process were also investigated.

Real-time ultrasonic control of spot-welded steel joints

Resistance welding is a welding method where the joining of materials is achieved by heating the contact area of the pieces to be joined with an electric current and pressure from plastic strain in the area of the weld. The process of heating workpieces in resistance welding occurs as a result of heat generated by the resistance of the welding current running through the workpieces. Spot welding is a process of joining overlapping workpieces between electrodes, which clamp the pieces together and pass the welding current on to heat the contact area (or ‘spot’) to the proper welding temperature (above the melting temperature). Because this process is quick, simple and effective, spot-welded joints are commonly applied in the automotive industry. Although the welds are usually made at robotized welding stations, they may still show some defects. Fundamental factors having a negative effect on spotwelded joints include:

Ultrasonic quality control methods for spot-welded joints

Spot resistance welding is the most popular method of connecting the steel structures of automotive vehicles. At a time when quality requirements relating to finished goods are higher and higher, welded joints must undergo precise controls in order to assure the highest safety standards possible. Ultrasonic methods enable quick and accurate assessment of any welded joints quality, and at the same time are environmentally friendly. Three ultrasonic applications that make it possible to determine the quality of a welded joint were discussed in the article: testing of joints welded by a single welding head, scanning acoustic tomography, and the resistance spot welding analyzers system – with the application of a mosaic head. The advantages and drawbacks of individual systems were described based on our own experience.

Aluminium to steel resistance spot welding with cold sprayed interlayer

ABSTRACT Studies on bonding of aluminium alloys to steels are popular because these are structural materials widely used in a variety of industries. However, joining these dissimilar materials is difficult mainly because of the formation of brittle intermetallic compounds. This paper presents a study on welding aluminium to steel by resistance spot welding. Before the welding, steel surface was covered by cold spraying with the layer of aluminium, nickel and nickel–aluminium. This way, instead of the welding of dissimilar materials, the welding of aluminium to aluminium (or nickel) layer pre-deposited on the steel sample was performed. The feasibility of using interlayers for improving the welding of dissimilar materials was tested using SEM, EDX and XRD. Mechanical properties of welds were investigated by microhardness and shear strength tests. The results showed that the coating allowed to decrease hardness in the welding zone and to increase the shear strength of the weld.

Metallisation of polycarbonates using a low pressure cold spray method

ABSTRACT In many industries, polymers are in great demand due to their low weight and good mechanical properties. However, films and coatings are sometimes applied to improve polymer surface properties. This work presents a study on the metallisation of polycarbonates using a low pressure cold spray (LPCS) method. Two types of commercial powders were selected for the deposition of coatings: (i) tin and (ii) aluminium. The coatings were applied (i) on an unmodified substrate and (ii) on a substrate with an interlayer, which enabled the formation of good adherent aluminium coatings. A light and scanning microscopy was used to analyse the microstructure of coatings. Electrical conductivity was determined using the four-probe method and is discussed in relation to the oxygen content. Moreover, bond strength and microhardness were investigated.

IN‐LINE ULTRASONIC INVESTIGATION OF SPOT WELD QUALITY USING MULTI‐TRANSDUCER SET‐UP

This article presents one of the most recent developments in real‐time ultrasonic quality control methods for resistance spot welds. Currently existing in‐line systems use single‐element transducer to characterize the spot weld quality. The new set‐up is based on 8 ultrasonic transducers placed in one line above the center of the spot weld. The solution presented in this paper makes another step forward towards improvement of accuracy of measurements using array of ultrasonic transducers.

Assessment of Electrode Consumption in Resistance Welding

The article discusses the assessment of electrode consumption during spot resistance welding processes. The process was performed using a manipulator provided with a welding head. During the process, welding parameters, environmental conditions and the material subjected to welding remained unchanged. The tests involved the performance of five welding cycles including the making of 100, 500, 1 000, 2 000 and 4 000 welds. Afterwards, to compare the consumption of six sets of electrodes, both used and not used in individual cycles, it was necessary to perform metallographic tests and hardness measurements. The tests revealed that the consumption of electrodes, leading to the lack of penetration in the central area of the weld, resulted from progressive recrystallization in the work area and from physical failure manifested by discontinuities having the form of intercrystalline cracks.

A high frequency ultrasonic imaging of welded joints

The paper presents chosen results obtained during the investigation of welded joints (laser, spot and friction) tested using acoustic microscopy method. Detection of welds properties and the defects strongly depends on ultrasonic transducers parameters. For the purpose of this research a prototype hardware setup was built - enabling evaluation of various types of ultrasonic probes. The system can be easily adjusted to the geometry of an object and is well equipped with appropriate software for the analysis and processing of images such as B-scan or C-scan. The setup enables determination of welds geometry, in particular the depth of the weld penetration in some cases.

Modelling ultrasonic wave propagation in a multilayered medium for resistance spot welding

This paper presents the results of modelling ultrasonic wave propagation in multi-layered media. Using a Finite Element Method (FEM), the analysis facilitates an improved understanding of wave behaviour within a typical weld stack-up, enabling one to better visualize phenomena associated with its propagation. In particular, the models developed in this work account for various weld-tip geometries. Here, inhomogeneity is generated by means of an uneven temperature distribution within the sample, in some cases giving rise to material phase transformation.