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• Time of issue:2021-11-12
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(Summary description)1. Welding problems occur in low alloy steel during welding

Low-alloy high-strength steels with lower strength grades, such as 300-400MPa grade, have good weldability due to the low content of alloying elements in the steel, which is close to low-carbon steel. With the increase of alloying elements in steel, the strength level increases, and the weldability of steel gradually deteriorates. The main problems that arise are:

1. Hardening tendency of heat-affected zone Steel grades with less carbon content and lower strength grades, such as 09Mn2, 09Mn2Si, 09MnV steel, etc., have little hardening tendency.

With the increase of the strength level, the tendency of hardening also begins to increase. For example, when 16Mn, 15MnV steel is welded, rapid cooling will result in the appearance of martensite structure in the heat-affected zone.

2. Cold cracks When welding low-alloy high-strength steels, the tendency of cold cracks in the heat-affected zone is increased, and such cold cracks often have a delayed nature, which is very harmful. For example, a large container with a wall thickness of 115 mm made of 18MnMoNb steel, due to insufficient preheating temperature, formed a large number of cold cracks in the heat-affected zone after welding.



The tack welds of low-alloy high-strength steels are easy to crack. The reason is that the welds are small in size, short in length, and fast in cooling. Such cracks are cold cracking.

3. Hot cracks Generally, hot-rolled and normalized steels with strength grades of 294 to 392 MPa have a low tendency of hot cracking. Hot cracks will also appear in the multi-layer submerged arc welding bead.

During electroslag welding, if the carbon content of the base material is too high and contains nickel, hot cracks in the shape of a figure eight may appear in the electroslag weld.

Medium-carbon quenched and tempered steel (such as 30CrMnSiA steel) with strength grade of 800~1176MPa is more sensitive to hot cracking during welding.