Austempering processes via cold liquids

The paper discusses austempering process performed at the first step in cold environment friendly liquid and then, at the second step, quenched products go immediately for tempering at a temperature equal or higher of martensite start temperature Ms. The new technology is based on discovered new characteristics of transient nucleate boiling process where surface temperature maintains at the level of boiling point of a liquid relatively a long time. In the paper three variants of austempering processes are considered: austempering process with use of cold water salt solutions of high concentration; austempering process with use of cold water solutions of inverse solubility polymers; austempering process with use of cold plain water under pressure. It is shown that core cooling rates of austempered by new technology products are 2 – 3 times larger as compared with conventional austempering in melted salts and alkalis. The new technology has several advantages. It is possible governing austempering temperature within 100oC and 450oC to provide optimal condition for achieving fine microstructure of highly strengthened bainite. The aim of elaboration is extending significantly size of products suitable for austempering, increasing mechanical properties of a material and making technology green.