奥氏体化温度对低碳低裂纹敏感性海工钢组织与性能的影响

研究了不同奥氏体化温度对690 MPa低碳低裂纹敏感性海工钢的奥氏体晶粒度、变体选择和韧脆转变温度的影响。结果表明:当奥氏体化温度大于930℃时,韧脆转变温度与奥氏体晶粒尺寸呈Cottrell-Petch关系,具体为:TB=-0.46-521.56d^-1/2,原始奥氏体晶粒可代表有效晶粒;当奥氏体化温度为880℃时,原奥氏体内部的变体选择对大角度晶界密度有明显贡献,Block界面和Packet界面所影响的晶体结构单元(有效晶粒)与韧脆转变温度呈现对应关系。临界奥氏体化温度(880℃)明显地影响了相变组织的变体选择,提高了Block和Packet晶界密度,使得韧脆转变温度明显降低。

Effect of austenitizing temperature on microstructure and properties of low carbon and low crack sensitivity offshore steel

The effects of different austenitizing temperatures on austenite grain size and ductile-brittle transition temperature of 690 MPa low carbon and low crack sensitivity offshore steel after quenching and tempering heat treatment were studied. The results show that when the austenitizing temperature is more than 930 ℃, the ductile-brittle transition temperature has a Cottrell-Petch relationship with the austenite grain size, which is as follows: TB=-0.46-521.56d^-1/2, and the primary austenite grain can represent the effective grain. When the austenitizing temperature is 880 ℃, the selection of variants in the primary austenite has an obvious contribution to the large angle grain boundary density, and the crystal structure unit(effective grain) affected by Block interface and Packet interface has a correspondence with ductile-brittle transition temperature. The critical austenitizing temperature(880 ℃) obviously affects the variation selection of phase transition microstructure, increases the grain boundary density of Block and Packet, and decreases the ductile-brittle transition temperature.