Welding Performance Of Q355D Seamless Square Tube
Leave a message
The welding of the Q355D seamless square tube needs to be preheated first because the carbon content is relatively high.
1. The purpose of preheating is to prevent cold cracks. Cold cracking is directly related to carbon equivalent. Therefore, to distinguish the carbon equivalent of the material, the carbon equivalent of Q355A and Q355D seamless square tubes are the same. The carbon equivalent of Q355 is less than 0.3%, so it can be said that the weldability is not bad (generally speaking, the sensitivity to cold cracks increases when the carbon equivalent is above 0.4%). So Q355A usually does not warm up. But when the plate is very thick, it still needs to be preheated due to the rapid cooling. 20# steel was cracked by J422 (E4303) welding. If the plate thickness is above 70mm, the risk of not preheating is very high. 2. By the way, the difference between this Q355D seamless square tube and the Q355A we usually use is that there are fewer impurities S and P, and better low-temperature impact performance. From the welding point of view, when there are fewer impurity elements in the base metal, it is good for controlling welding hot cracks. 3. Of course, since the base material is Q355D material, it is generally said that it has a special purpose, so the welding material will not be selected casually. It is best to use it according to the welding material manual. If the welding rod manual says to preheat the base metal, then preheat. Because the welding material is not used according to the manufacturer's instructions, the performance of the weld will be greatly reduced.
Q355A, B, C, D, E steel comparison
Q355A contains less than or equal to 0.045% phosphorus and sulfur
Q355B contains less than or equal to 0.040% phosphorus and sulfur
Q355C contains less than or equal to 0.035% phosphorus and sulfur
Q355D contains less than or equal to 0.030% phosphorus and sulfur
Q355E contains less than or equal to 0.025% phosphorus and sulfur
The more phosphorus and sulfur impurity elements in the steel, the worse the impact toughness
Q355A - Q355B aKV not less than 34 at 20 degrees Celsius
Q355C aKV is not less than 34 at 0 degrees Celsius
Q355D aKV not less than 34 at -20 degrees Celsius
Q355E aKV not less than 27 at -40 degrees Celsius
