Abstract: Cold stretching technique is proposed in order to overcome the shortcomings of low yield strength of austenitic stainless steels. The key parameters for cold stretching are strain rate and strain level, their influence on material properties is analyzed. It is pointed out that excessively small strain rate will lead to occurrence of serrated yielding and plastic instability will be caused, thus the appropriate strain rate is very important for cold stretching. The strength of stretched steels can be improved significantly while its toughness still maintains a high level. Metallographic structure analysis and content of α′ martensite test show that when select reasonable strain level, only a little α′ martensite can be transformed but has no detrimental effect on material properties, and microstructure of pre and post cold stretched steels do not change obviously as well. The results show that the yield stress of austenitic stainless steels can be greatly increased when using cold stretching technique and other mechanical properties are not obviously influenced to guarantee safe running for pressure equipment. With this technique the weight of vessel can be lighten, which can bring remarkable economic benefit and with wide prospect of application.

Key words: Austenitic stainless steels, Cold stretching, Deformation martensite, Serrated yielding, Strength, Toughness