材料期刊网

研究了两种成分的马氏体时效不锈钢。测定了钢中回火奥氏体含量与回火温度、回火时间、淬火温度的关系.两种钢经850℃淬火后回火,奥氏体含量随回火温度升高开始增加随后又下降,在610℃左右达到峰值约24％。奥氏体含量随回火时间的延长而增加,是一扩散控制过程。奥氏体含量与淬火温度有明显关系。在同一温度(580℃)回火,奥氏体含量与淬火温度之间存在最低值:两种钢各在1000℃和950℃淬火后回火,其奥氏体含量下降至零值附近。 测定了不同淬火温度、回火温度、回火时间对钢中微观应变△a/a的影响。经不同热处理后,△a/a的变化与马氏体二奥氏体相变过程有关。分析了钢的组织与力学性能之间的关系。回火奥氏体的存在使强度下降,估计10％的奥氏体使强度损失约10kg/mm~2。但较软的回火奥氏体沿板条状马氏体边界形成改善钢的韧性,使冲击韧性a_K提高。从钢的强度和韧性的配合考虑,采用适当的回火处理以产生5—10％稳定的回火奥氏体是可取的。

The volume fractions of austenite have been determined on two maragingstainless steels with respect to tempering temperature and time or quenching tem-perature. When the specimens were quenched from 850℃ and tempered under dif-ferent temperatures for 4h, the reverted austenite began to appear at a temperingtemperature of about 550℃, reached its peak value of 24% volume fraction atabout 610℃ and disappeared over 700℃. Under certain definite tempering temper-ature their volume fractions were increased as prolonging the tempering time.And the process seems to be of diffusion controlling. The minimum volume frac-tion of austenite, being near zero, was resulted by being quenched at 1000 or950℃ under same tempering temperature of 580℃ for 4h. The effect of different heat treatment on the microstrain Δα/α of the steels,closely related to phase transformation process of M?A, has also been investigatedby means of X-ray diffraction. The presence of austenite at any 10% would causeloss of strength of both steels about 10 kg/mm~2, however, their toughness mightbe actually improved by these softer austenites formed along the boundaries oflath martensite. In view of combining both strength and toughness of the steelsthe proper heat treatment process to form 5-10% stable reverted austenite wouldperhaps be desirable.