This article first appeared in Practical Engineering 1940 Vol1 No19. The information within the publication is therefore correct as of 1940. The article provides an account of developments within Metallurgy.
One of the latest developments in metallurgy is a small compact device for surface-hardening metals. The apparatus is a Russian invention and it utilises a gas pressure of 10cm. of water. With it, non-ferrous metals and steels can be given treatments corresponding to carbonising, nitriding, cyaniding and bright annealing.
For some time France has been carrying out research in the welding of nickel-chromium air-hardened and case-hardened steel in an effort to find a process that will eliminate brittleness. It is now claimed that they have solved the problem. A non-hardening metal, such as austenitic stainless steel of the nickel-chromium type, is first deposited on the surfaces of the chamfers to a depth somewhat greater than the thickness of the base metal. By annealing the treated part, the zone of brittleness is removed. The parts are then hardened and tempered, if this is desired, so as to give the desirable mechanical properties.
After this, assembly of the parts takes place, and the joints are welded, austenitic electrodes being used. The weld is made entirely upon the deposited coating. In this way all necessity for re-heat treating the base metal is avoided.
New Case-Hardening Process
A new surface-hardening process has been originated by America. The process is intended for plain and alloy steels, such as nickel steel and nickel chromium steel, and is known as "dry cyaniding." Continuous nitriding and continuous gas carburising are the essentials, embodied in this process. The case is similar to that given by normal cyaniding. The principle of the method is the use of ammonia combined with other gas carbonising mixtures.