Low-alloy steel, has very low carbon contents, most of which are less than 0.2%, and contains a small amount of Si, Mn, Cu, Ti, Mo, Nb, P and other alloying elements. Low alloy steel has high strength and toughness, and also has good performance in corrosion resistance, wear resistance, and low temperature resistance. Generally speaking, the weldability of low alloy steel is good, which can be welded by various welding methods such as gas welding.
For the low alloy steel of 300-350MPa strength grade, gas welding is often used. This type of steel has better weldability, especially the 300MPa grade steel. Therefore, the welding of these low alloy steel generally does not use flux and can be welded with the same welding specifications as the low carbon steel, which means that there is no special process requirement.
For the low alloy steel above 350MPa, due to the increased strength level and a certain amount of alloying elements, the hardening tendency is lower for carbon steels. Therefore, at this time, it is necessary to slightly preheat the welding area with a heat source such as a gas welding flame, and appropriately increase the number and length of the positioning points to prevent cracks.
