H220BD超低碳烘烤硬化钢耐时效性能

Aging resistance performance of H220BD ultra-low carbon baking hardening stee

采用光学显微镜观察了H220BD烘烤硬化钢在不同退火温度和不同炉内露点条件下的显微组织,对不同露点样品的表面形貌进行了光学显微镜和扫描电镜观察,并测试了不同退火温度和炉内露点的力学性能以及时效性能。结果表明:炉内露点对表面形貌和基板晶粒无影响;炉内露点低时,脱碳程度低,BH值高,时效性差;当炉内露点升高时,时效性能好,但BH值会随之降低;晶粒尺寸和烘烤硬化值随着退火温度的升高而增大,当退火温度820℃,炉内露点为-20℃时,此时BH值和时效性能达到最佳,时效性能可满足6个月以上。

Microstructure of H220BD steel was observed by OM with different annealing temperature and different dew point conditions in furnace,surface morphology was observed by OM and SEM with different different dew point,its mechanical properties and aging performance with different annealing temperature and different dew point were tested.The results show that the dew point in the furnace has no effect on the surface morphology and grain size.When the dew point in the furnace is low,the degree of decarburization is low,BH value is high,and aging performance is poor.When the dew point in the furnace increases,aging performance is good,but BH value decreases accordingly.Grain size and BH value increase as annealing temperature increases,when the annealing temperature is 820℃,dew point in the furnace is-20℃,BH value and aging performance can reach the best,and aging performance can meet more than six months.