Last time, there are 4 factors that affect the performance of metal welding, including material factors. Today, let’s take a look at the other three factors.
2. Process factors
Process factors include welding method, welding process parameters, welding sequence, preheating, post-heating and post-welding heat treatment. The welding method used by the automatic welding tracking system has a great influence on the weldability, which is mainly manifested in the characteristics of the heat source and the protection conditions.
Different welding methods have very different heat sources in terms of power, energy density, and maximum heating temperature. Metals welded under different heat sources will show different welding performance. For example, the power of electroslag welding is very high, but the energy density is very low, the maximum heating temperature is not high, the heating is slow during welding, and the high temperature residence time is long, which makes the heat-affected zone grain coarse and the impact toughness is significantly reduced. It must be normalized. improve. In contrast, methods such as electron beam welding and laser welding have low power, but high energy density and rapid heating. The high temperature residence time is short, the heat-affected zone is very narrow, and there is no danger of grain growth.
Adjust the welding process parameters, take preheating, post-heating, multi-layer welding and control the interlayer temperature and other process measures to adjust and control the welding thermal cycle, thereby changing the weldability of the metal. If measures such as preheating before welding or heat treatment after welding are taken, it is completely possible to obtain welded joints without crack defects and meeting performance requirements.
If you want to make bright stainless steel industrial pipes, post-weld heat treatment is more recommended. Because even though the steel has been heat-treated before forming, the stress of the material still increases after a series of bending and forming. However, the on-line heat treatment after welding can not only ensure the air tightness and the shielding gas atmosphere, but also improve the quality of the weld and increase the softness of the material. If the material heat treatment is relatively high, you can consider Hangao Tech (SEKO Machinery) heat preservation type bright annealing machine of induction heating . It has more heat preservation area than ordinary annealing, which can give the metal better ductility and tensile resistance.
3. Structural factors
Mainly refers to the design form of welded structure and welded joints, such as the influence of structural shape, size, thickness, joint groove form, weld layout and cross-sectional shape, etc. on weldability. Its influence is mainly manifested in the heat transfer and the state of force. Different plate thicknesses, different joint forms or groove shapes have different heat transfer speed directions and heat transfer speeds, which will affect the crystallization direction and grain growth of the molten pool. The switch of the structure, the thickness of the plate and the layout of the welding seam, etc., determine the stiffness and restraint of the joint, and affect the stress state of the joint. Poor crystalline morphology, severe stress concentration and excessive welding stress are the basic conditions for the formation of welding cracks. In the design, reducing joint stiffness, reducing cross welds, and reducing various factors that cause stress concentration are important measures to improve weldability.
4. Conditions of use
Refers to the working temperature, load conditions and working medium of the welded structure during service. These working environment and operating conditions require the welded structure to have corresponding performance. For example, welded structures that work at low temperatures must have brittle fracture resistance; structures that work at high temperatures must have creep resistance; structures that work under alternating loads have good fatigue resistance; work in acid, alkali or salt media The welded container should have high corrosion resistance and so on. In short, the harsher the use conditions, the higher the quality requirements for the welded joints, and the less likely it is to ensure the weldability of the materials.
