High-chromium Or Rust-proof Steel
Category: ALLOYS AND THEIR EFFECT UPON STEEL
High-chromium, or what is called stainless steel containing from
11 to 14 per cent chromium, was originally developed for cutlery
purposes, but has in the past few years been used to a considerable
extent for exhaust valves in airplane engines because of its resistance
to scaling at high temperatures.
Carbon 0.20 to 0.40
Manganese, not to exceed 0.50
Phosphorus, not to exceed 0.035
Sulphur, not to exceed 0.035
Chromium 11.50 to 14.00
Silicon, not to exceed 0.30
The steel should be heated slowly and forged at a temperature above
1,750 deg.F. preferably between 1,800 and 2,200 deg.F. If forged at temperatures
between 1,650 and 1,750 deg.F. there is considerable danger of rupturing
the steel because of its hardness at red heat. Owing to the
air-hardening property of the steel, the drop-forgings should be
trimmed while hot. Thin forgings should be reheated to redness
before trimming, as otherwise they are liable to crack.
The forgings will be hard if they are allowed to cool in air. This
hardness varies over a range of from 250 to 500 Brinell, depending
on the original forging temperature.
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