摘要
冲击功是评价H11模具钢服役性能的重要特征之一。针对国内某钢厂生产的H11模具钢出现冲击功波动较大的现象,结合微观组织分析、夹杂物表征及对比分析和热力学理论计算,探究了导致H11具钢冲击功波动的主要原因和Ca对MgO·Al_(2)O_(3)夹杂物的转变机理。研究结果表明,大尺寸的Ds类夹杂物是导致H11模具钢冲击功较低且波动较大的主要因素(试验钢室温无缺口冲击吸收功平均值由(327±3.4)J降低至(233±26.1)J),确定了钢中的Ca含量是导致D/Ds类夹杂物超标的主要原因。结合商业热力学软件FactSage 8.2计算结果可知,当试验钢中Ca质量分数较低(<0.0005%)时,H11模具钢中夹杂物以高熔点MgO·Al_(2)O_(3)类夹杂物为主,此类夹杂物不容易聚合长大;但当试验钢中Ca质量分数较高(0.0009%)时,由于Ca对MgO·Al_(2)O_(3)夹杂物的改性作用导致钢中夹杂物以容易聚合长大的低熔点CaO-MgO-Al_(2)O_(3)类夹杂物为主,但是此类夹杂物很难从钢液中去除,导致了H11模具钢中Ds类夹杂物超标。同时发现,在冲击载荷作用下,大尺寸夹杂物(>10μm)会首先从基体中脱粘并引起微裂纹,微孔周围内应力的局部集中导致了裂纹萌生和裂纹扩展,进而降低了试验钢的冲击吸收功。最后,提出通过优化冶炼工艺过程降低Ca含量是解决H11模具钢中大尺寸夹杂物超标问题的主要攻关方向。
Impact absorbing energy is an important feature in evaluating the service performance of H11 die steel.Aiming at the phenomenon of large fluctuation of impact absorbing energy of H11 die steel produced by a domestic iron and steel company,combined with microstructure characterization,nonmetallic inclusion characterization and comparative analysis and thermodynamic theoretical calculation,the main reasons leading to the fluctuation of impact absorbing energy of H11 die steel and the transformation mechanism of Ca to MgO·Al_(2)O_(3) inclusions were explored.The results showed that the large size of Ds inclusions was the main factor leading to the low and fluctuating impact absorbing energy of H11 die steel(the average value of unnotched impact absorbing energy at room temperature decreased from(327±3.4)J to(233±26.1)J).It was determined that the Ca content in steel was the main reason cause of the exceeding of D/Ds inclusions.Combined with the calculation results of commercial thermodynamic software FactSage 8.2,it can be seen that when the Ca in the experimental steel is low(<0.0005%),the inclusions in the H11 die steel are dominated by high melting point MgO·Al_(2)O_(3) inclusions,which are difficult to polymerize and grow.However,when the Ca in the experimental steel is high(0.0009%),the inclusions in the steel are dominated by low melting point CaO-MgO-Al_(2)O_(3) inclusions,which are easy to polymerize and grow due to the modifying effect of Ca on MgO·Al2O3inclusions.Furthermore,it is difficult to remove the inclusions from the molten steel,which leads to excessive Ds inclusions in H11 die steel.It was found that under impact loading,largesize inclusions(>10μm)would first debonding from the matrix and produce microcracks,and the local concentration of internal stress around the micropores would lead to crack initiation and crack propagation,thus reducing the impact absorbing energy of the experimental steel.Finally,it is proposed that reducing the Ca content by optimizing the smelting process is the main
作者
董君伟
李吉航
田家龙
姜周华
DONG Junwei;LI Jihang;TIAN Jialong;JIANG Zhouhua(School of Metallurgy,Northeastern University,Shenyang 110819,Liaoning,China)
出处
《钢铁》
CAS
CSCD
北大核心
2024年第5期125-133,160,共10页
Iron and Steel
基金
国家自然科学基金资助项目(U1908223)。
关键词
H11模具钢
冲击功
非金属夹杂物
裂纹萌生
Ca处理
H11 die steel
impact absorbing energy
nonmetallic inclusion
crack initiation
calcium treatment
