冷却过程H2含量对800 MPa级热镀锌双相钢性能及表面质量的影响

针对目前热镀锌双相钢在生产过程中随着合金元素的添加而出现的表面质量问题,对热镀锌双相钢表面出现小黑点以及麻面缺陷进行了显微组织分析,研究了不同冷却段H₂含量对800 MPa级热镀锌双相钢力学性能及表面质量的影响。结果表明,随着热镀锌冷却段H₂含量的不断增加,试样的屈服强度及抗拉强度明显升高,主要因为H₂含量增加造成试样在冷却过程中马氏体转变量的增加,从而提高了综合力学性能;同时表面小黑点及麻面缺陷数量明显减少,试样在冷却过程中得到了还原,减少了Mn、Si等元素氧化物,保证了试样形成致密的抑制层,但H₂含量超过10%后对表面质量影响变小并且伸长率下降明显,所以考虑能耗,冷却段H₂投入量应控制在10%。

Effect of H2 content in cooling stage on properties and surface quality of 800 MPa grade hot dip galvanized dual phase steel

Aim at surface quality problem arose in the production process of hot galvanized dual phase steel which caused by adding alloying elements,such as small black spots and piping defect,the microstructure of the 800 MPa grade hot galvanized dual phase steel was analyzed and the effect of H₂content in hot dip galvanization cooling section on mechanical properties and surface quality was studied.The results show that with the increase of H₂content in cooling section,the yield strength and tensile strength of the specimen increase significantly,mainly because the increasing of H₂content increases martensitic transformation amount in the process of cooling,so that improves the comprehensive mechanical properties.At the same time,the quantity of surface textured defect and small black spots decreases significantly,the specimen gets reduction in the cooling process so that the surface Mn and Si oxides are decreased,which ensures the formation of dense inhibition layer.However,the influence on surface quality is small and the elongation decreases significantly when the H₂content is more than 10%,so considering the energy consumption,the H₂input of cooling section should be controlled at 10%.