奥氏体不锈钢应变强化工艺及性能研究

针对奥氏体不锈钢延性好但屈服强度低的问题,提出采用应变强化工艺来提高材料屈服强度。分析应变强化工艺中两个关键工艺参数——应变速度和应变量对材料力学行为的影响,指出应变速度不宜过慢,否则会出现锯齿形屈服行为,对材料性能造成不利影响。经应变强化后的奥氏体不锈钢在显著提高强度的同时,仍能保持较好的韧性。通过金相组织分析、马氏体体积分数测定等结果表明,将应变量控制在10%以下,强化后奥氏体组织仅发生少量的α′马氏体相变,对材料的力学性能影响不大,且材料的微观组织也没有明显变化。研究结果表明,采用应变强化技术在大幅提高奥氏体不锈钢屈服强度的同时,对材料的其他力学性能均不造成大的影响,从而为压力容器的安全运行提供有力保证,可实现压力容器的轻型化设计,经济和社会效益显著,应用前景广阔。

Study on Technique and Properties of Cold Stretching for Austenitic Stainless Steels

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.