Regarding the preheating temperature of Cr-Mo steel tube sections
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Why must the preheating temperature for surfacing 309 on Cr-Mo steel tube sections be lower than that for submerged arc surfacing of Co-Mo material protrusions on Cr-Mo steel tube sections? Also, why is the preheating temperature higher when V is added compared to when it is not added? How is the welding strip transmission system (such as the conductive blocks) at the head of the electroslag surfacing welder adjusted? It’s not good if it’s too loose or too tight – what problems can arise in either case? How do you solve this issue? It seems quite troublesome for the workers to adjust the tightness
This post was last edited by zhangjuhua on 2015-10-22 at 22:47. Titanium has a strong affinity for carbon, ammonia, and oxygen, forming stable compounds with them. Vanadium exists in steel mainly in the form of carbides. Its main function is to refine the structure and grains of steel, thereby reducing its strength and toughness. When dissolved in a solid solution at high temperatures, the hardenability increases ； Conversely, when present in the form of carbides, it reduces hardenability. Vanadium increases the temper stability of quenched steel and induces a secondary hardening effect. The vanadium content in steel is generally not more than 0.5%, except in high-speed tool steels. Vanadium is often used in structural steel alloys in combination with elements such as manganese, chromium, molybdenum, and tungsten, as it reduces hardenability under normal heat treatment conditions. In quenched and tempered steel, vanadium primarily enhances the strength and yield ratio of the steel, refines the grain structure, and reduces its sensitivity to overheating. In carburized steel, it can refine the grain structure, allowing the steel to be quenched directly after carburizing without the need for a second quenching step. Copied from the internet
I thought about it and it seems to make some sense, but it’s not entirely accurate, what do you think?
The above is copied from the Internet; in short, it’s a guess that adding V improves thermal stability, which is why a higher preheating temperature is required
You say that in general, welding by surfacing requires starting the arc with a low current – is that because it’s easier to do so with a low current?
I’m sorry, I don’t know much about welding; I only know that a lower current might result in less deformation and stress
I see. It’s actually a limitation of the equipment – since a welding current of around 1200A is required for 75mm solder strips, there’s a concern that the equipment may not be able to reach such a high current level.