690 MPa级以上高强钢焊接熔敷金属微观组织及其联合贝氏体的研究进展

Research Progress on Microstructure and Coalesced Bainite of Welded Deposited Metal to High-Strength Steel with Tensile Strength above 690 MPa

690 MPa级以上高强钢的发展和工程应用受限于缺乏与其强韧性相匹配的焊接材料,其根本原因是以针状铁素体为主的690 MPa级以下高强钢熔敷金属的强韧化理论已经不能指导新一代高强钢焊接熔敷金属的设计。因此,解决该问题的关键是寻求最佳的熔敷金属微观组织结构。综述了690 MPa级以上高强钢焊接熔敷金属中出现的联合贝氏体和其它各类微观组织对其强韧性的影响。其中,由不同形貌贝氏体相和针状铁素体相组成的复相分割结构可使焊接熔敷金属实现良好的强韧性匹配;然而,联合贝氏体作为下贝氏体的一种,其大尺寸的特点会显著降低高强钢焊接熔敷金属的强韧性;此外,可以通过物理冶金改善高强钢焊接熔敷金属的性能。

The development and application of high-strength steel whose tensile strength is above 690 MPa are limited to lacking of welded materials with matching strength-toughness.The welded deposited metal to high-strength steel whose tensile strength is below 690 MPa,mainly consists of acicular ferrite.The theory of strengthening-toughening for it is not suitable for welded deposited metal of new generation high-strength steel.Therefore,the key to solve the problem is to obtain the ideal microstructure of welded deposited metal.The effect of coalesced bainite and other various microstructures on strength-toughness of welded deposited metal to high-strength steel whose tensile strength is above 690 MPa,was reviewed.It is found that the interlace multiphase microstructure composed by different bainites and acicular ferrite can make welded deposited metal achieve good strength-toughness matching.However,due to its large grain size,coalesced bainite,as a kind of lower bainite,can significantly decrease the strength-toughness of welded deposited metal to high-strength steel.Moreover,the properties of welded deposited metal to high-strength steel can be improved by physical metallurgy.