MECHANICAL-PROPERTIES OF 0.40 PCT C-NI-CR-MO HIGH-STRENGTH STEEL HAVING A MIXED STRUCTURE OF MARTENSITE AND BAINITE
MECHANICAL-PROPERTIES OF 0.40 PCT C-NI-CR-MO HIGH-STRENGTH STEEL HAVING A MIXED STRUCTURE OF MARTENSITE AND BAINITE
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DOI：
10.1007/bf02656714
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发表时间：
1985-01-01
期刊：
影响因子：
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通讯作者：
OKABAYASHI, K
中科院分区：
文献类型：
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作者：
TOMITA, Y;OKABAYASHI, K
本文系统地研究了贝氏体对具有马氏体和贝氏体混合组织的日本0. 40% C-Ni-Cr-Mo高强度钢（AISI 4340型）力学性能的影响。等温转变下贝氏体在593 K，出现在针状的形式和分区的原奥氏体晶粒，与回火马氏体提供了一个更好的组合的强度和断裂韧性，提高真缺口拉伸强度（TNTS）和断裂外观转变温度（FATT）在夏比冲击试验。无论下贝氏体存在的体积分数和/或用于在两相之间产生强度差异的回火条件如何，都会发生这种情况。在673 K等温转变的上贝氏体以大量的形式出现，填充原奥氏体晶粒，对钢的强度和断裂塑性有非常不利的影响。显着的损害发生TNTS和FATT，无论上贝氏体的体积分数和/或回火条件时，上贝氏体与回火马氏体。然而，当上述两种类型的贝氏体以相同的尺寸、形状和分布出现在回火马氏体中，大致等于贝氏体的强度时，在混合组织的拉伸性能和贝氏体的体积分数之间观察到类似的趋势或显著的相似性。从上述结果可以推测，具有马氏体和贝氏体的混合结构的高强度钢的机械性能受马氏体内贝氏体的尺寸、形状和分布的影响比受马氏体和贝氏体之间的强度差或存在的混合贝氏体的类型的影响更大。本文从混合物修正定律、金相检验和应力-应变图分析等方面简要讨论了马氏体中贝氏体的大小、形状和分布对钢的力学性能的显著影响。
A study has been systematically made of the effect of bainite on the mechanical properties of a commercial Japanese 0.40 pct C-Ni-Cr-Mo high strength steel (AISI 4340 type) having a mixed structure of martensite and bainite. Isothermal transformation of lower bainite at 593 K, which appeared in acicular form and partitioned prior austenite grains, in association with tempered marprovided provided a better combination of strength and fracture ductility, improving true notch tensile strength (TNTS) and fracture appearance transition temperature (FATT) in Charpy impact tests. This occurred regardless of the volume fraction of lower bainite present and/or the tempering conditions employed to create a difference in strength between the two phases. Upper bainite which was isothermally transformed at 673 K appeared as masses that filled prior austenite grains and had a very detrimental effect on the strength and fracture ductility of the steel. Significant damage occurred to TNTS and FATT, irrespective of the volume fraction of upper bainite present and/or the tempering conditions employed when the upper bainite was associated with tempered martensite. However, when the above two types of bainite appeared in the same size, shape, and distribution within tempered martensite approximately equalized to the strength of the bainite, a similar trend or a marked similarity was observed between the tensile properties of the mixed structures and the volume fraction of bainite. From the above results, it is assumed that the mechanical properties of high strength steels having a mixed structure of martensite and bainite are affected more strongly by the size, shape, and distribution of bainite within martensite than by the difference in strength between martensite and bainite or by the type of mixed bainite present. The remarkable effects of the size, shape, and distribution of bainite within martensite on the mechanical properties of the steel are briefly discussed in terms of the modified law of mixtures, metallographic examinations, and the analyses of stress-strain diagrams.