What is the NM360 wear-resistant plate welding process?

Characteristics and attention points of NM360 wear-resistant plate welding

1. The characteristics of NM360 wear-resistant plate in welding, using oxygen-acetylene gas (or NAS gas) local preheating method, pay attention to the preheating temperature can not be too high, otherwise it will increase the high temperature residence time, slow down the cooling rate, and promote brittleness crack.

2.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. This type of cracking is cold cracking. When the shovel plate wear-resistant steel plate and the shovel tooth alloy cast steel are point-fixed, the point-fixing length is 40-60mm, and at the same time, it is fixed with a small current. Make the entire structure in a preheating state.

3.The welding of shovel plate wear-resistant steel plate and shovel tooth alloy cast steel adopts mixed gas shielded welding. Due to the stable arc of mixed gas shielded welding, the splash is small, it can realize the short-circuit transfer with stable droplet transfer frequency, and can weld fine-grained structural steel. Seam mechanical properties are better than pure Ar or CO2 gas shielded welding.

NM360 wear-resistant plates are widely used, so Ar+CO2 mixed gas shielded welding is used, where Ar is 70% to 80%, and CO2 is 20% to 30%. For the selection of welding heat input, the wear-resistant steel plate is a low-alloy steel, which is prone to produce a low-hardened structure in its heat-affected zone, leading to cold cracks.

In addition, the heat treatment state of the NM360 steel is from hot rolling, normalizing to quenching and tempering, the welding heat input is reduced, and the heat input has a significant impact on the cold crack resistance and mechanical properties of the weld metal. Therefore, from the starting point of reducing the tendency of hardening and cold cracking, avoiding the overheating of austenite during welding, and reducing the residence time in the high temperature zone, it is considered that the use of smaller heat input can reduce the generation of welding defects.