改良型T23钢CGHAZ再热裂纹开裂特征

Characteristics of reheat cracking in CGHAZ of modified T23 steel

为了分析国产改良型T23钢粗晶热影响区(CGHAZ)再热裂纹的开裂特征,在Gleeble-3500热力耦合试验机进行了CGHAZ的制备和STF(strain to fracture)试验,获得了不同试验温度下的断裂试样,并采用SEM及EBSD在断口剖面试样上展开微区的特征分析。结果表明:空洞在晶界M3C上形核,随着应力松弛,空洞增加并聚集形成微裂纹。不同试验温度下,空洞形核和裂纹扩展时,晶界及晶内应变的集中程度非常不同,反映了它们各自塑性变形能力的不同,是造成不同温度下T23钢CGHAZ再热裂纹开裂特征不同的原因。

Coarse grained heat affected zone（ CGHAZ） preparation and strain-to-fracture（ STF） tests were performed by means of Gleeble-3500 thermo-mechanical simulator to analyze the characteristics of reheat cracking in the CGHAZ of the domestic T23 steel. Electronic backscattered diffraction（ EBSD） and scanning electron microscopy（ SEM） were used to carry out microanalysis in the section of failure samples. The results show that cavities nucleate at M3 C carbides at grain boundary. More cavities form and gather during stress relief,thus the cracks forms and propagates. The strain concentration is different at grain boundaries and inside grains during cavity formation and crack propagation under different test temperatures. It reflects the different plastic deformation capacity of grain boundaries and grain interior,which results in various characteristics of reheat cracking in the CGHAZ of T23 steel under different temperatures.