Microstructure and Mechanical Properties of GMAW Weld Metal of 890 MPa Class Steel

摘要

The relationship between microstructure and mechanical properties of gas metal arc weld metal with strength over 890 MPa is discussed. The microstructure of the weld metals is characterized with OM, SEM, TEM and EBSD. The microstructure of the weld metals is mainly composed of martensie and bainite. Experiment results show that the microstructure with predominantly fine lath bainite possess good toughness of 77 J, while its yield strength is less than 800 MPa. The microstructure of coarse lath martensite and bainite has the lowest toughness of 43 J and its yield strength is 820 MPa. The mixtured microstructure with fine martensite, bainite and retained austenite films bears good combination of toughness and yield strength (62 J and 880 MPa, respectively). It is concluded that fine effective grain size and ductile phase of austenite films are two main factors to achieve good mechanical properities.