Views: 1 Author: Site Editor Publish Time: 2023-05-25 Origin: Site
Everyone will have some welding problems when using square tubes. The welding process of square tubes has always been a difficult step in the square tube process, especially when welding. If the cooling rate is too fast during welding, it is easy to cause cracks, so you should avoid being wet by rainwater and welding at the vent when welding; when welding medium/high carbon steel or alloy steel, it is necessary to determine whether to welding can only be carried out by taking heating and heat preservation measures.
Improper welding sequences also easy to cause cracks. When the welding sequence is improper, it will form a dead knot of welding shrinkage force, which will hinder the natural shrinkage of the weld, resulting in large shrinkage stress and weld cracks.
The general cause of welding cracks is related to the chemical composition, crystallization structure, and smelting method of the square tube raw materials; for example, the higher the carbon content of the steel or the higher the alloy content, the higher the hardness of the steel, and the easier it is usually to occur during welding. crack.
During the welding operation, the temperature of the surrounding environment is low or the heat dissipation conditions such as vents are too good, resulting in excessive heat dissipation, which can also cause cracks.
The welding rods used for welding square tubes contain sulfur, phosphorus, and high-carbon welds are also prone to cracks; sulfur and phosphorus are harmful elements, and high-sulfur-containing welds have thermal brittleness, high-phosphorus-containing welds have cold brittleness, and welding rods containing sulfur The amount of phosphorus must be controlled below 0.0035. Most of the problems with square rectangular tubes are related to the welding method and the temperature during welding. The welding environment temperature is low and the cooling rate is too fast. Whether it is a straight rectangular tube that is formed at one time, or a square tube that is round and then square, the square tube will generate internal stress during the forming process, and the existence of internal stress in the high temperature season will not cause too much trouble , and in winter when the temperature is low, the existence of internal stress is more obvious. For example, cracking may occur during loading, unloading and welding. The best solution is to heat-treat the produced square tube (that is, the above-mentioned heating and heat preservation measures obtained); the heat treatment process of the square rectangular tube, firstly, the square rectangular tube is sampled and tested to understand the mechanical properties (yield, tensile strength, etc.) The square rectangular tube is put into the trolley furnace, and the furnace temperature is changed according to the prescribed heating system. Heating-constant temperature-insulation-cooling is carried out in the furnace. After heat treatment, the internal stress of the steel tube itself can be eliminated, and the probability of cracking can be greatly reduced.
Tips: Do not rush to weld when the temperature is very low; preheat the position to be welded with a flame or other methods before welding, which will greatly reduce cracks in the cold winter If boiling water is poured directly into a cold glass, the glass may burst due to a large temperature difference. For example, pour warm water into the glass to increase the temperature of the glass, then pour boiling water into the glass, and the crack Is the situation greatly reduced?)