Analysis of super-hardening treatment technology on the surface of stainless steel welded pipe mould

The stainless steel welded pipe is formed by rolling a stainless steel plate through a number of molds on a welded pipe forming machine and then welded. Due to the high strength of stainless steel and its structure is a face-centered cubic lattice, it is easy to form work hardening, so that when the welded pipe is formed: on the one hand, the mold has to withstand greater friction, which makes the mold easy to wear; on the other hand, the stainless steel sheet It is easy to form adhesion (occlusion) with the surface of the mold, causing strain on the welded pipe and the surface of the mold. Therefore, a good stainless steel forming mold must have extremely high wear resistance and anti-bonding (seizure) performance. The analysis of the imported welded pipe mold by Huaxia Mould Network shows that the surface treatment of this kind of mold is treated with superhard metal carbide or nitride coating. (Guide: Detailed explanation of stamping die materials and heat treatment process)

Stainless steel welded pipe forming mold material is generally made of high carbon and high chromium Cr12MoV (or SRD11, D2, DC53). At present, the following process flow is generally used to make molds in China: blanking → rough machining → heat treatment (high temperature quenching and high temperature tempering) → finishing → nitriding → finished product (Note: In order to save costs, general manufacturers now omit forging and Two spheroidizing annealing processes are time-consuming and costly). Since Cr12MoV materials are high-carbon and high-chromium alloy steels, there is a large segregation of components in the original structure (this segregation cannot be eliminated even in general forging). In this way, the internal structure of the mold after heat treatment (high quenching and high recovery) is extremely uneven, and the macroscopic appearance is extremely uneven (HRC about 40 to 60). After nitriding treatment, the unevenness of the mold surface cannot be eliminated. The hardness is even further reduced. In actual use, the surface of the mold and the welded pipe is easy to be strained, and the mold life is low.

The ultra-hardening treatment technology of the mold surface has been successfully applied to the stainless steel welded pipe forming mold. The mold processed by this technology forms a metal carbide layer with a hardness of about HV3000 on its surface. The carbide layer is dense and closely combined with the substrate. It does not affect the surface finish of the workpiece. It has extremely high wear resistance and seizure resistance. Fundamentally solve the problem of roughening of welded pipes, reduce the workload of the subsequent polishing process of pipe making and improve product quality, greatly increase the service life of the mold, and reduce the workload of after-sales service. Practice shows that this technology has extremely high use value.

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