I. Introduction of diffusion metal carbide coating technology
1. Technical introduction
Diffusion metal carbide coating technology is to place the workpiece in a special medium and diffuse on the surface of the workpiece to form a layer of metal carbides of several micrometers to several tens of micrometers.
The carbide layer has a very high hardness, HV can reach 1600~3000 (determined by the type of carbide), in addition, the carbide track layer is metallurgically bonded to the substrate, does not affect the surface finish of the workpiece, and has extremely high wear resistance and resistance. The properties of occlusion (bonding) and corrosion resistance can greatly improve the service life of tooling and mechanical parts.
2. Comparison with related technologies
The method of forming a superhard compound film layer on the surface of the workpiece is an effective and economical method for greatly improving the wear resistance, seizure resistance (anti-adhesion), corrosion resistance and the like, thereby greatly improving the service life thereof. At present, the surface hardening treatment methods of workpieces mainly include physical vapor deposition (PVD), chemical vapor deposition (CVD), physical chemical vapor deposition (PCVD), and diffusion metal carbide structure. Among them, the PVD method has a low deposition temperature. The advantage of small deformation of the workpiece, but due to the poor bonding force between the film layer and the substrate, the process is not good, and it is often difficult to exert the performance advantages of the superhard compound film layer. The CVD method has the advantages of good film-based bonding force and good process coating, but for a large number of steel materials, the subsequent matrix hardening treatment is troublesome, and the film layer is easily damaged. Therefore, its application is mainly concentrated on materials such as cemented carbide. The deposition temperature of PCVD method is low, the film-based bonding force and the process winding property are both improved compared with the PVD method. However, compared with the diffusion method, the film-based bonding force still has a large gap, and the PCVD method is still a plasma film formation. Although the winding property is improved compared with the PVD method, it cannot be eliminated.
The metal carbide coating formed by the diffusion metal carbide coating technology forms a metallurgical bond with the matrix and has a film-based bonding force unmatched by PVD and PCVD. Therefore, the technology can truly exert the performance advantages of the super-hard layer. The technique does not have the problem of the winding property, and the subsequent hardening treatment of the substrate is convenient, and the treatment can be repeated many times, so that the applicability of the technology is more extensive.
3. Technical advantages
Diffusion metal carbide coating technology is widely used in Japan, European countries, Australia, South Korea and other countries. According to the survey, a large number of matching molds on imported equipment have used this technology. When these molds are localized, due to the lack of corresponding mature technology, the mold life is often low, and some are not even domestically produced.
This technology has been studied in the 1970s. However, due to various conditions, processes and equipment are often difficult to pass the test of batch and long-term production, making some practical problems in the technology difficult to expose or difficult to solve, often halfway. . In the course of more than ten years of research and application, we have conducted in-depth research on the existing problems in the process and equipment of the technology, and carried out effective improvement. The improved process and complete sets of equipment have been able to meet the long-term requirements. The requirements of stable production, the life expectancy of the processed molds reached the life level of imported similar molds, and obtained a wealth of production experience of various types of molds, laying a solid technical foundation for the large-scale promotion and application of this technology.
4, the scope of application
Diffusion metal carbide coating technology can be widely used in various types of tooling or mechanical parts that cause failure due to wear and bite. Among them, failure due to wear (such as punching, cold heading, powder molding and other molds) can increase the life of several times to tens of times; the product or mold strain caused by the bite (such as extension die, flange Models, etc., can be fundamentally resolved.
Applicable materials:
Die steel, structural steel with carbon content greater than 0.3%, cast iron, hard alloy.
Second, stainless steel welded pipe mold surface super hardening treatment technology
The stainless steel welded pipe is formed on the welded pipe forming machine by a stainless steel plate through several molds and welded. Due to the high strength of the stainless steel and the structure of the 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 bear a large friction force, so that the mold is easy to wear; on the other hand, the stainless steel sheet It is easy to form a bond (bite) with the surface of the mold, causing strain on the surface of the welded pipe and the mold. Therefore, a good stainless steel forming mold must have extremely high wear resistance and anti-bonding (biting) properties. Our analysis of imported welded pipe molds shows that the surface treatment of these types of molds is treated with super hard metal carbide or nitride coating.
Stainless steel welded pipe mold materials are generally made of high carbon and high chromium Cr12MoV (or SRD11, D2, DC53). At present, the following process is commonly used in China to make molds: blanking → rough processing → heat treatment (high temperature quenching plus high temperature tempering) → finishing → nitriding → finished products (Note: in order to save costs, the general manufacturers now have saved the forging and Spheroidizing annealing is two time-consuming and costly processes). Since the Cr12MoV type material is a high carbon high chromium alloy steel, its original structure has a large composition segregation (this segregation cannot be eliminated even by 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 performance is extremely uneven in hardness (about 40 to 60 for HRC). 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 are easily pulled, and the life of the mold is low.
The mold surface superhardening treatment technology researched by Lake Company has been successfully applied to stainless steel welded pipe forming molds. The mold treated by the technology forms a metal carbide layer with a hardness of up to HV3000 on the surface thereof. The carbide layer is dense and tightly combined with the substrate, does not affect the surface finish of the workpiece, and has extremely high wear resistance and seizure resistance. It fundamentally solves the problem of pulling the welded pipe, reduces the workload of the subsequent polishing process of the pipe and improves the quality of the product, greatly improves the service life of the die, and reduces the workload of after-sales service. Practice has shown that this technology has extremely high use value. The following is a comparison of the process mold and the nitriding mold.
1, performance:
Nitriding mold
Surface hardness: HV700~1000 or so HV3000 or so
Matrix hardness: extremely uneven HRC58~62HRC40~60
2. Process flow:
Nitriding mold: blanking → roughing → heat treatment (high quenching and high recovery) → finishing → nitriding → finished product The process of processing the mold: cutting → all processing in place (no heat treatment required) → the process treatment (base hardening and surface treatment) Finished at once). → Grinding inner hole → finished product can be seen from the process flow, this process can shorten the processing cycle of the mold.
3, the effect of use:
Compared with the nitriding mold, the mold processed by the process can fundamentally solve the pulling of the welded pipe, thereby reducing the workload of the subsequent polishing process of the welded pipe and improving the product quality (the pipe wall is reduced due to a large amount of polishing), thereby greatly improving the service life of the die. Reduce after-sales service workload.
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