Cold cracks are cracks formed during the cooling stage of the welded joint during welding. The thermal stress generated during welding will remain in the joint after the weld pool solidifies. As the joint cools, the thermal stress will gradually release. When the thermal stress exceeds the tensile strength of the material, cracks will occur.
Cold cracks are mainly divided into the following three categories:
1. Intergranular cracks: Intergranular cracks mainly occur in certain alloy materials, such as stainless steel, nickel alloys, etc. This type of crack occurs between grains because the welding thermal cycle and changes in material composition lead to intergranular corrosion and brittleness.
2. Penetration cracks: Penetration cracks occur in the weld pool of the weld, usually due to excessive heat input during welding, resulting in excessive amounts of dissolved metal, causing the weld pool to solidify excessively, thus forming cracks.
3. Heat-affected zone cracks: Heat-affected zone cracks occur in the weld heat-affected zone, that is, the area around the weld joint. The heat input during welding changes the structure and properties of the material, resulting in increased brittleness in these areas, thus forming cracks.

NM400 is a kind of wear-resistant steel plate. NM400 has a very high mechanical strength; its mechanical properties are 3 to 5 times that of ordinary low-alloy steel plates; it can significantly improve the wear resistance of mechanical-related parts; thus increasing the service life of the machinery; and reducing production costs. The surface hardness of this product usually reaches 360~450HB.

1. High manganese steel plate, such as high manganese steel (ZGMn13), high manganese alloy (ZGMn13Crmn), ultra-high manganese alloy (ZGMn18CR2MoRe), etc. It must be noted that high manganese wear-resistant steel plate must be subjected to severe impact or high pressure to produce work hardening on the surface and show its high wear resistance, otherwise high manganese wear-resistant steel is not wear-resistant.
2. Wear-resistant chromium iron steel plate, such as high, medium, and low chromium alloy cast iron (Cr15MOZCu), etc.
3. Alloy wear-resistant steel plate, such as low alloy steel plate after heat treatment, JFE-EH400, JFE-EH500, DILLIDUR 450, etc.