The control of the structure and properties of the weld metal is critical to the quality of the weld. There are several factors to consider to control the structure and performance of weld metal, including welding process parameters, welding material selection, heat treatment, etc. Here are some commonly used methods and considerations:
Control of welding process parameters:
Welding current and voltage: Current and voltage are the most basic parameters in the welding process. The right current and voltage can affect the welding speed, penetration depth, and the structure of the deposited metal.
Welding speed: The adjustment of welding speed can affect the solidification time and grain growth rate of the weld, which can affect the refinement of the structure and the improvement of performance.
Selection of welding materials:
Wire and flux selection: Different wires and fluxes have an impact on the chemical composition of the weld metal and the formation of solid solutions. Choosing the right welding material can help control the structure and properties of the metal.
Substrate selection: The choice of substrate can also have an impact on the structure of the weld metal. Ensure that the chemical composition and properties of the substrate match the welding material when welding.
Heat Treatment: Normalization Treatment: Normalization treatment can adjust the structure of the weld metal and improve the strength and toughness through a proper heating and cooling process.
Ageing: For some special materials, ageing can be carried out after welding to optimize the structure and performance.
Preheating and post-heat treatment:
Preheating: For some large or thick weldments, preheating can slow down the cooling rate and help reduce the tendency of the weld area to harden.
Post-heat treatment: For some high-strength alloys, post-heat treatment can be performed after welding to eliminate residual stress and improve microstructure stability.
Reasonable design of welded joints:
Design the right joint geometry: Proper joint design can reduce stress concentrations, slow down weld distortion, and help control the performance of the weld metal.
Avoid excessive weld distortion: Excessive weld distortion may lead to residual stress and damage to the microstructure, so appropriate measures need to be taken to control the weld distortion.
By comprehensively considering the above factors and making reasonable control in the actual welding process, the structure and properties of the weld metal can be effectively controlled and the welding quality can be improved. At the same time, in order to ensure the reliability of welding, proper testing and quality control are also required.