Technical Data

Metallurgical Terms

Sulphur Print.

A macrographic method of examination for the distribution of impurities. A sheet of bromide paper, after being soaked in dilute sulphuric acid, is placed upon the plane polished surface to be examined. The sulphides in the steel react with the acid, liberating hydrogen sulphide which reacts with the silver salt in the paper, leaving a dark brown stain, thus indicating the distribution of the sulphur.

Superplasticity.

A property brought about by heat treatment or controlled work which enables certain alloys to be extensively deformed by small forces and without risk of fracture. The alloys exhibiting superplasticity have an extremely fine grain size. Some non-ferrous alloys can be made superplastic at room temperature, for others, including steel, high temperatures are needed.

Surface Hardening.

This may be achieved by various methods which are described under their respective headings:- nitriding, carbon case hardening, gas carburizing, flame hardening and induction hardening.

Swaging.

A process by which metal is worked into the desired shape by a series of blows rapidly applied by suitably shaped dies to produce close tolerances in cylindrical or tapered bars or tubes. In hand swaging, the bar or tube is rotated. In machine or rotary swaging, the dies, usually two in number but sometimes four on  large machines, reciprocate rapidly as the spindle on which they are mounted rotates. This means that the finished work must be round, but within this limitation swaging can be applied to a wide variety of pointing, tapering, sizing and reducing operations.

Swarf.

Fine particles of metal (usually iron or steel) produced in machining or grinding.