The kinds of steel used where elasticity is desired are known as spring steel, blister steel, and shear or double-shear steel, although, for small springs, steel of the tool-steel class is often employed.
The word temper, as used by the manufacturer of steel, means the percentage of carbon it contains, the following being the most useful tempers of cast steel.
Razor Temper (11⁄2 per cent. carbon).—This steel is so easily burnt by being overheated that it can only be placed in the hands of a very skilful workman. When properly treated it will do twice the work of ordinary tool steel for turning chilled rolls, &c.
Saw-file Temper (13⁄8 per cent. carbon).—This steel requires careful treatment, and although it will stand more fire than the preceding temper should not be heated above a cherry red.
Tool Temper (11⁄4 per cent. carbon).—The most useful temper for turning tools, drills, and planing-machine tools in the hands of ordinary workmen. It is possible to weld cast steel of this temper, but not without care and skill.
Spindle Temper (11⁄8 per cent. carbon).—A very useful temper for mill picks, circular cutters, very large turning tools, taps, screwing dies, &c. This temper requires considerable care in welding.
Chisel Temper (1 per cent. carbon).—An extremely useful temper, combining, as it does, great toughness in the unhardened state, with the capacity of hardening at a low heat. It may also be welded without much difficulty. It is, consequently, well adapted for tools, where the unhardened part is required to stand the blow of a hammer without snipping, and where a hard cutting edge is required, such as cold chisels, hot salts, &c.
Set Temper (7⁄8 per cent. carbon).—This temper is adapted for tools where the chief punishment is on the unhardened part, such as cold sets, which have to stand the blows of a very heavy hammer.
Die Temper (3⁄4 per cent. carbon).—The most suitable temper for tools where the surface only is required to be hard, and where the capacity to withstand great pressure is of importance, such as stamping or pressing dies, boiler cups, &c. Both the last two tempers may be easily welded by a mechanic accustomed to weld cast steel.
The preference of an expert temperer for a particular brand of steel is, by no means, to be taken as proof of the superiority of that steel for the specific purpose. It may be that, under his conditions of manipulation, it is the best, but it may also be that, under a slight variation of treatment, other brands would be equal or even superior. It may be accepted as a rule that the reputation of a steel for a particular purpose is a sufficient guarantee of its adaptability to that purpose, and all that is necessary to a practical man is to be guided by the reputation of the brand of steel, and only change when he finds defects in the results, or ascertains that others are using a different steel with superior results.