Effect of Heat Input on Microstructure and Properties of Welded Joint of Low Temperature High Manganese Steel

With CHW-SMn submerged arc welding wire and CHF610 flux, low temperature high manganese steel was welded by submerged arc welding under different heat inputs (12.0, 16.0, 20.0 kJ · cm⁻¹). The effect of heat input on the microstructure and properties of the joint was studied. The results show that under different heat inputs, the weld microstructures were all composed of columnar crystal + precipitate, and the microstructures of the heat affected zone were austenite with a small amount of inclusions and precipitetes. With the increase of heat input, the microstructure of the heat affected zone was coarsened and the width of the coarse-grained zone increased. With the increase of heat input, the strength and toughness of the welded joint decreased, and the microhardness of the weld decreased first and then increased. When the heat input was 12.0 kJ · cm⁻¹ and 16.0 kJ · cm⁻¹, no cracks were observed on the weld surface of the welded joint after bending, but cracks appeared when the heat input was 20.0 kJ · cm⁻¹. The tensile and impact fracture of the joints under different heat inputs showed dimple morphology, and the fracture modes were all ductile fracture. When the heat input was 12.0 kJ · cm⁻¹, the mechanical properties of the welded joint were relatively good.