B质量分数对620℃时效中FB2钢组织和力学性能的影响

Effect of B mass fraction on microstructure and mechanical properties of FB2 steel aged at 620℃

通过扫描电镜、拉伸性能测试和硬度测试等对620℃长期时效中不同B质量分数的FB2钢进行组织观察和力学性能分析。研究结果表明:在FB2钢620℃长期时效中,M_(23)C_(6)相的平均尺寸随时效时间的延长逐渐增大,其平均尺寸随B质量分数的增加而逐渐减小;Laves相在时效1000 h后析出,并且随着时效时间的延长不断长大粗化,其平均尺寸随B质量分数的增加而逐渐减小;BN夹杂物的析出量随B质量分数的增加而逐渐增大。FB2钢的拉伸性能随着时效时间的延长而逐渐减弱,随B质量分数的增加先增强后减弱,并且在B质量分数为0.010%时拉伸性能达到最强。FB2钢的硬度随着时效时间的延长而逐渐减小,随B质量分数的增加先增大后减小,并且在B质量分数为0.010%时硬度达到最大。当B质量分数由0增加到0.010%时,拉伸性能和硬度的增大是M_(23)C_(6)相和Laves相的平均尺寸的减小所引起的;当B质量分数由0.010%增加到0.030%时,拉伸性能和硬度的减小是BN夹杂物析出量的增加所导致的。为充分发挥钢中B、N的强化作用,同时提高FB2钢的高温性能及稳定性,钢中较优的B质量分数控制在0.010%左右。

The organization observation and mechanical property analysis of FB2 steel with different B mass fractions in long-term aging at 620℃were performed by scanning electron microscopy,tensile property test and hardness test.The results show that the average size of M_(23)C_(6)phase gradually increases with the increase of aging time,and its average size gradually decreases with the increase of B mass fraction;the Laves phase precipitates after aging for 1000 h,and grows and coarsens with the increase of aging time,and its average size gradually decreases with the increase of B mass fraction;the precipitation of BN inclusions gradually increases with the increase of B mass fraction.The tensile properties of FB2 steel gradually decrease with the increase of aging time,increasing first and then decreasing with the increase of B mass fraction,and the tensile properties reach the maximum at 0.010%of B mass fraction.The hardness of FB2 steel gradually decreases with the increase of aging time,increasing first and then decreasing with the increase of B mass fraction,and reaches the maximum at 0.010%of B mass fraction.When the B mass fraction increases from 0 to 0.010%,the increase of tensile properties and hardness is caused by the decrease of the average size of M_(23)C_(6)and Laves phases;when the B mass fraction increases from 0.010%to 0.030%,the decrease of tensile properties and hardness is caused by the increase of BN inclusions precipitation.In order to give full play to the strengthening effect of B and N in steel,and at the same time improve the high temperature performance and stability of FB2 steel,the better control of B mass fraction in steel is around 0.010%.