Study On The Weldability Of NMG300Wear Resistant Steel Plate

According to the good matching attribute between SQJ707wire and NMG300wear-resistant steel plate, SQJ707wire is selected as deposited metal to weld NMG300wear-resistant steel plate in order to study the welded joint performance.In this paper, line energy input of manual arc welding and CO2gas shielded welding is firstly used for contrast test. From the aspects of line energy, there is a certain relationship in NMG300wear-resistant steel plate of the toughness of the welded joint and the size of heat input. It is determined that CO2gas shielded welding is superior to manual arc welding when the welding NMG300wear-resistant steel plate. Secondly, in order to improve the NMG300wear-resistant steel plate welded joint of the critical fracture stress, reduce the cold cracking sensitivity, NMG300wear-resistant steel plate must be preheated before welding, in order to reduce the hardening tendency. In this article, we combined the carbon equivalent method, the bolt test and inclined Y groove test to study welding cold cracking sensitivity of the12mm thick NMG300wear-resistant steel plate. Under a constant line energy, the microstructure and mechanical properties of the welded joint of NMG300wear-resistant steel plate in CO2gas shielded is studied under five different preheating conditions, i.e. no preheating, preheating to150℃,200℃,250℃and300℃, respectively.Research found that the NMG300wear-resistant steel plate welded joint weld area organization as the proeutectoid ferrite and acicular ferrite, coarse grain zone of heat affected zone(HAZ), organization for plate strip martensite and granular bainite, back to the fire area organization for tempering martensite, these materials to ensure the NMG300wear-resistant steel plate welding joint strength and toughness. Preheating before welding of the welded joint has a certain influence, these effects include weld hardness drop, hardening tendency of decreased, but the tensile strength remains the same, this is because the preheating before welding temperature increase, will cause the weld center of acicular ferrite increases, in the HAZ coarse grained OuDeBei austenite increase, decrease martensite. The toughness of welded joint is close to the parent metal when the line energy is within18.4KJ·cm-1. After the confirmation of the optimized welding parameters, indexes like strength and toughness can meet production requirements. Finally welding procedure specification is proposed and welding preheating temperature is230℃～280℃for NMG300wear-resistant steel plate.