Mg脱氧夹杂物对大线能量焊接HAZ组织的影响

Influence of inclusions with Mg deoxidation on the microstructure in the heat-affected zone of steel plates after high-heat-input welding

研究了夹杂物对Mg脱氧钢焊接热影响区(HAZ)组织及冲击韧性的影响.研究结果表明,MgO–MnS复合夹杂物形貌随着Al的添加发生显著变化.当Al质量分数为0.001%时,由中心单一MgO粒子与外围MnS相组成;当Al质量分数为0.020%时,其形貌为夹杂物中多个细小的MgO粒子嵌入MnS相中.前者可诱发晶内针状铁素体(IAF)形核,而后者不具备该能力,故HAZ中主要晶内组织分别为塑性IAF、脆性侧板条铁素体.因此,未添加Al钢的400 kJ·cm−1大线能量焊接HAZ韧性优于添加Al钢.

The effects of inclusions on the microstructure and toughness of the heat-affected zone(HAZ)in steel plates with Mg deoxidation after high-heat-input welding were investigated in the present study.The results indicate that the morphologies of MgO–MnS complex inclusions in steel are changed obviously with the addition of Al.When containing 0.001%Al(mass fraction),the inclusions consist of a central single MgO particle and an outside MnS phase.When containing 0.020%Al,they are comprised of several small MgO particles entrapped by the MnS phase.Because the former inclusion can nucleate intragranular acicular ferrites(IAFs)and the latter is non-nucleant,the main intragranular microstructures in the HAZs are ductile IAFs and brittle ferrite side plates,respectively.Therefore,the HAZ toughness of the steel plate without Al addition after a high-heat-input welding of 400 kJ·cm−1 is significantly better than that of the steel plate with Al addition.