The products of mechanical manufacturing plants, such as press machine bodies, machine tool beds, hydraulic cylinder barrels, and gearbox bodies, have extreme requirements for dimensional accuracy and stability. Welding heat treatment is a key process to ensure that these products do not deform or fail during processing and use.
Industry characteristics
The core contradiction of heat treatment in mechanical factories is the confrontation between welding stress and machining accuracy. Residual stress is released during mechanical processing, which can cause deformation of the workpiece and result in the scrapping of precision parts. Therefore, the direct purpose of its heat treatment is very pure: to minimize welding stress before precision machining.
Key points to note
Preheating before welding: Preheating is crucial for welding repair of medium carbon steel or cast iron parts, with the aim of reducing the cooling rate difference between the welding area and the base metal, preventing white microstructure and quenching cracks.
• Hydrogen elimination treatment: When welding high-strength steel (such as 40Cr, 34CrNiMo6) for welding machinery, if the hydrogen content of the welding material is not strictly controlled, hydrogen elimination treatment must be carried out to prevent hydrogen induced delayed fracture during service.
Post weld heat treatment:
1. Stress relief annealing: This is the most commonly used process. The temperature is usually below the Ac1 point (usually 550-650 ° C), and it is cooled slowly after insulation. The goal is to reduce residual stress to a level that does not affect mechanical processing and use, rather than changing the material structure.
2. Integrity: To ensure uniform stress relief, the workpiece should undergo overall furnace heat treatment as much as possible. The furnace loading method should be reasonable, supported by shims to prevent the workpiece from deforming due to its own weight at high temperatures.
3. Coordination with processing sequence: The heat treatment process must be closely integrated into the manufacturing process. Usually arranged after rough machining and before precision machining to eliminate some of the stress released by rough machining.
Product Application
Our company's standard ceramic heating plates and cost-effective temperature control machine provide perfect stress relief annealing solutions for mechanical manufacturing customers. For workpieces such as machine tool beds and press frames, overall heat treatment can be carried out in the furnace after rough machining. Our heating plate provides a uniform and stable heat source, while the temperature control box can accurately perform a stress relief annealing process at 550-650 ° C, and automatically execute a slow cooling program after insulation is completed. The entire process is fully automated, eliminating human operation errors and ensuring that the internal stress of the workpiece is minimized before precision machining, thereby ensuring the final assembly accuracy and long-term stability of use.