Thursday, June 5, 2008

Welding Metals


An elaborate account is given in the Bulletin de l'Academie Royale de Belgique of Spring's remarkable researches in the welding of metallic bodies by simple pressure at temperatures far below their fusing point.

The metals were put in the shape of cylinders bounded by plane surfaces, great care being taken as to their purity, and having been mounted in a stirrup and pressed together by means of a hand screw they were placed in a heating oven and kept at a constant temperature between 200 degrees and 400 degrees for from 3 to 12 hours.

The most perfect joints were produced with gold, lead and tin, and the worst with bismuth and antimony. Two cylinders thus welded together could be put in a lathe, one of them only being held in the chuck, while the other was being worked upon by a cutting tool, without coming apart. They could be separated with the aid of pinchers, but then a rough breakage was produced which did not coincide with the original plane of separation.

It appeared that the more crystalline the bodies the less do they exhibit this phenomenon of incipient liquefaction, which begins to show in the case of platinum, for instance, at 1,600 degrees below its fusing point, and that such a liquefaction or softening actually takes place was proved by cutting a delicate spiral 0.2 mm. deep on the end surface of a piece of copper weighing 130 grams and placing it upon a sheet of mica. After keeping it at 400 degrees for eight hours the spiral had entirely disappeared.

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