The welding of NM500

    
    NM500 steel is a high-strength abrasion-resistant steel commonly used in structural applications such as excavator buckets, crushers, and conveyor systems. Welding NM500 steel can be a challenge due to its higher hardness and tensile strength when compared to standard mild steels. However, it can be done successfully if the right welding procedure, joint design, and known pre- and post-weld treatments are used.
    
    For best results, an experienced welder should use a combination of pre-heating, edged prepping, and interpass temperature control for welding NM500 steel. Pre-heating helps alleviate or reduce problems with shrinkage and cracking by decreasing the overall cooling rate. A preheat temperature of 250°F (121°C) should be used for all steel thicknesses up to 1” (25.4 mm). For thicker plate, the preheat temperature should not exceed 600°F (316°C). Temperature should be verified with a temperature indicator before welding.
    
    An edged joint is recommended for all NM500 steel welds because it provides a greater joint strength than any other joint design, including butt joints and fillet joints. Additionally, using a double-V bevel provides better penetration and allows for more efficient use of filler metal. When preparing the joint, it is important that the bevel is at least 1⁄16” (1.6 mm) wide, with a maximum gap distance of 0.09” (2.3 mm).
    
    The interpass temperature should also be closely monitored during welding. This is the temperature of the steel between passes of the weld and impacts the weld quality and performance. An acceptable interpass temperature should not exceed 300°F (149°C). If the temperature goes above 300°F (149°C), the weld should be stopped and the excess heat should be allowed to cool before restarting the weld.
    
    To ensure the best results, the welded joint should be inspected for its integrity and strength immediately after the weld is completed. It is also recommended that post-heating and post-weld treatments be used for extra stress relief. Post-heating can help prevent excessive shrinkage and improve toughness, as can cold treatment and peening. This helps reduce the risk of bracket or plate failure from internal stresses.
    
    Welding NM500 steel can be a challenge due to its increased hardness and strength. However, when the right welding procedure, joint design, and pre- and post-weld treatments are used, the weld can be successful. Experienced welders should take the proper precautions to ensure the best quality weld possible.