Tomokatsu Aizawa

Interfacial microstructure of magnetic pressure seam welded Al-Fe, Al-Ni and Al-Cu lap joints

A new welding method, magnetic pressure seam welding, was used to lap join dissimilar metals (Al-Fe, Al-Ni and Al-Cu). The circuit for magnetic pressure seam welding consists of a capacitor, an electric discharge gap switch, and a plate-type coil. The overlapped metal plates are placed over the coil. When an impulse current from an energy-storage capacitor bank passes through the coil, a high-density magnetic flux is suddenly generated around the coil. The generated high-density magnetic flux lines cross the end of the overlapped plates. Eddy currents are induced mainly inside the Al plate because it has a high electrical conductivity. Both the Joule heat generated in the plates and the magnetic pressure applied from the Al side promote the joining of the lapped plates. The welding is normally achieved within 10 μs. This results in very little microstructural change in the parent plates aside from the area around the weld interface. Strong lap joints were obtained for every metal combination and no tensile fracture took place in the weld region. A characteristic wavy morphology was observed at the weld interface. An intermediate phase layer was also observed at the weld interface. TEM observation revealed that the intermediate layer consisted of fine Al grains and intermetallic compound particles dispersed among the Al grains. The growth direction of the wave, the welding condition dependency of the wavelength and the amplitude of the interfacial wave were intensively investigated in order to clarify the welding mechanism of this method.

Experimental and numerical study on magnetic pulse welding to improving the life time of one-turn flat coil

The objective of this investigation was to obtain an improved understanding of magnetic pulse welding processes and the mechanisms of electromagnetic forces applied to a one-turn flat coil. Results of simple numerical investigation and experiments show that the electromagnetic forces on the middle part of the coil can be canceled out by loading the welded workpieces on both sides of the coil and can prevent coil deformation and improve its lifetime.

Electromagnetic Bulging of Stainless Steel Sheet by Using Flat One-Turn Coil

In this paper, we describe an electromagnetic bulging for a SUS304-O stainless steel sheet (0.15 mm thick) and its experimental results. In the die forming, the flat one-turn coil is adopted for the bulging of the SUS304-O sheet, when an aluminum sheet (0.3 mm thick) as a driving plate (driver) is used together. When an impulse current from an energy-storing capacitor bank passes through the flat one-turn coil, a high-density magnetic flux is suddenly generated around the coil. Eddy currents are induced in the driver placed on the coil. The SUS304-O sheet is pressed by an electromagnetic force generated in the driver, leading to bulge into a meandering groove with small concave shape. The bank energy required for the bulging of 12mm wide, 60mm long and 0.43mm high is about 4.5 kJ, and the obtained workpiece does not almost have wrinkles and curves.

Comparison between Simple Seam Welding and Adjacent Parallel Seam Welding by Magnetic Pulse Sheet-Welding Method

This paper describes the comparison between simple seam welding and adjacent parallel seam welding by a magnetic pulse welding method for Al-Al sheets. In the case of the parallel seam welding, the sheets collided at high speed in two parallel along a narrow central part of a one-turn flat coil. The central part had two parallel upper parts. The width of the central part was same as that of the simple seam welding. The increase of the parallel seam-weld zones was more than double in total in comparison with the simple seam-weld zones. Two inside parallel seam-weld zones were connected each other with a small cavity.

One-metre-long seam welding of aluminium sheets by applying magnetic pressure: introduction of new connection method of long sheet metal ends

Thin aluminium sheet, which is characteristically light and has high strength per unit weight and good workability, is widely used in, for example, industrial products, household products, and soft drink cans. In a production line capable of continuous surface treatment and heat treatment of thin aluminium sheet, it is necessary to join the rear end of the preceding aluminium sheet to the leading end of the next aluminium sheet coming onto the line. There are various methods of performing this joining technique, which is known as ‘sheet connection’. In many cases, the ends of the sheets are brought to a temporary halt to be joined. Electromagnetic seam welding – 8 is used for sheet connection and this has the extremely short welding time of 10ms. Here, we report on basic experiments in electromagnetic seam welding of long aluminium thin sheets of 1 m or longer, on various sheet connection methods, the fabrication of connections for experimental line treatment and, finally, on a new sheet connection method.