Kazuyoshi Hoshino

Wear Loss and Life of Electrode Tips in Resistance Spot Welding of Aluminum-plated Steel.

Pb-8%Sn coated steel sheets are used for the fuel tanks of motor vehicles. Lead-free steel sheets are used to prevent pollution. Aluminum-coated steel sheets are used for vehicle, but the short life of electrodes used for spot welding of the steel sheets is a serious problem. Three kinds of copper alloy electrodes were manufactured and used for the investigation. They are Cu-Cr, Cu-Cr-Zr and alumina dispersed copper alloys. Both sides of aluminum-plated steel sheets 0.8 min in thickness were used for the study. The upper electrodes showed a convex shape and an penetration of aluminum and iron was observed. The lower electrodes showed a concave shape by reverse pick-up. Furthermore, the penetration of aluminum in depth was shorter than that of the upper electrodes and no iron was observed. The results obtained in continuous spot welding with 11 kA shows that the life of alumina dispersed copper alloy electrodes was 800 spots which is two times that of Cu-Cr alloy electrodes.

Effects of Rotational Stirring on Zn-0.05%Sn Alloy Castings

Tin is effective for reducing the grain size of pure zinc castings, but on the contrary causes intergranular corrosion of the castings when more than 0.05 % is added. The cast structure of Zn-0,05 % Sn alloy solidified in stirring was investigated. To observe the effects of stirring on the movement of liquid, a solution of water and 60 % glycerin with 66 nylon balls were stirred in an acryl vessel at various conditions. The results obtained are as follows. Granular crystals that had separated accumulated at the bottom of vessel when the effects of stirring on the water or solution were not observed at the bottom of vessel. But columnar crystals were seen to develop from the bottom of vessel when they were indicating, stirring at 2∼3 s -1 was effective for reducing grain size.

Damping capacity of ZnAl alloy sheets

The effect of cold rolling on the logarithmic decrement δ of Zn-Al/Zn-Al-0.02%Mg alloy containing less than 22% Al was investigated. A logarithmic decrement δ of 85% for cold rolled Zn-15%Al/Zn-15%Al-0.02%Mg alloy sheets was close in value to that of the same alloy sheets water quenched from 573 K. With an increase in rolling reduction, the value of δ was increased. As a result of tensile properties and hardness testing, the elongation was increased and the hardness was decreased with an increase in the rolling reduction for as-rolled alloys

Foundry Patterns Photofabricated Through Negative Film.

In order to obtain patterns for foundry, liquid photopolymer is cured by the exposure of ultraviolet rays through negative film. Single-and multiayer photopolymer patterns for foundry are investigated. The curing behavior of photopolymer is investigated through the relation between the exposure of UV rays and the curing of photopolymer at various spots. Positive and negative patterns in four layers are manufactured by the exposure of UV rays through four sheets of negative film. Applied examples of this process for civil castings in Kawaguchi are shown. The advantages and disadvantages of the process are discussed. Improvement of the exposure unit of UV rays and new photopolymers which have low viscosity, high sensitivity for UV rays and little shrinhage after curing are expected for further devolopment of the process.