Super hardening treatment technology for metal mold surface

Super hardening treatment technology for metal mold surface
1. Introduction of diffusion method metal carbide coating technology

1. Technical introduction    diffusion method metal carbide coating technology is to place the workpiece in a special medium, and form a metal carbide layer of several microns to tens of microns on the surface of the work piece by diffusion. The carbide layer has extremely high hardness, and the HV can reach 1600″3000 (determined by the type of carbide). In addition, the carbide layer is metallurgically combined with the substrate, which does not affect the surface finish of the workpiece, and has extremely high wear resistance and resistance. Occlusion (bonding), corrosion resistance, etc., can greatly increase the service life of molds and mechanical parts.

2. Compared with related technologies, the method of forming a superhard compound film on the surface of the workpiece can greatly improve its wear resistance, seizure resistance (anti-bonding), corrosion resistance and other properties, thereby greatly improving its service life. And the economical method. At present, the surface super-hardening treatment methods of workpieces mainly include physical vapor deposition (PVD), chemical vapor deposition (CVD), physical chemical vapor deposition (PCVD), and diffusion metal carbide layer technology. Among them, the PVD method has a low deposition temperature. The advantages of small deformation of the workpiece, but due to the poor bonding force between the film layer and the substrate, and the poor process winding and plating, it is often difficult to give play to the performance advantages of the superhard compound film layer.

The CVD method has outstanding advantages such as good film-base bonding and good process winding and plating properties. However, for a large number of steel materials, the subsequent hardening of the matrix is ​​more troublesome. If you are not careful, the film layer is easily damaged. Therefore, its application is mainly concentrated on materials such as cemented carbide. The PCVD method has a low deposition temperature, and the film base bonding force and process winding property are greatly improved compared with the PVD method. However, compared with the diffusion method, the film base bonding force still has a large gap.

In addition, the PCVD method is still plasma film formation Although the winding performance is improved compared with PVD method, it cannot be eliminated. The metal carbide coating formed by the diffusion method metal carbide coating technology forms a metallurgical bond with the substrate, and has a film-base bonding force that PVD and PCVD can’t match. Therefore, this technology can really give play to the performance advantages of the super hard film layer. , This technology does not have the problem of winding and plating, the subsequent hardening of the substrate is convenient, and the treatment can be repeated many times, which makes the applicability of this technology more extensive.

3. Technical advantages    diffusion method metal carbide coating technology is widely used in Japan, European countries, Australia, South Korea and other countries. According to investigations, many matching molds on imported equipment use this technology in large quantities. When these molds are made domestically, due to the lack of corresponding mature technology, the mold life is often low, and some of them cannot even be made domestically.

This technology has been studied in the 1970s in China, but due to various conditions, the process and equipment are often difficult to pass the test of batch and long-term production, so that some actual problems in the technology are not easy to expose or solve, and they are often abandoned halfway. . In the process of more than ten years of research and application, we have conducted in-depth research on the actual problems of the technology and equipment, and made effective improvements. The improved process and complete equipment have been able to meet the long-term The requirements of stable production, the life level of the molds handled have reached the life level of imported similar molds, and the rich production experience in practical application of various molds has been obtained, which has laid a solid technical foundation for the large-scale promotion and application of this technology.

4. Scope of application    diffusion metal carbide coating technology can be widely used in all kinds of molds or mechanical parts that fail due to wear and seizure. Among them, failures caused by wear (such as punching, cold heading, powder molding and other molds) can increase the service life by several to tens of times; product or mold strain problems caused by seizure (such as drawing die, flanging) Modulus, etc.) can be fundamentally solved.

Applicable materials: die steel, structural steel with carbon content greater than 0.3%, cast iron, cemented carbide.

2. Ultra-hardening treatment technology of stainless steel welded pipe mold surface

Stainless steel welded pipe is formed by rolling a stainless steel plate through several 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, making the mold easy to wear; on the other hand, stainless steel sheet It is easy to form adhesion (occlusion) with the mold surface, causing strain on the welded pipe and mold surface. Therefore, a good stainless steel forming mold must have extremely high wear resistance and anti-bonding (seizure) performance. Our analysis of imported welded pipe molds shows that the surface treatment of this type of mold is treated with superhard metal carbide or nitride coating.

Stainless steel welded pipe forming die material is generally made of Cr12MoV (or SRD11, D2, DC53) with high carbon and high chromium. At present, the following process flow is generally used to make molds in China: blanking%26rarr; rough machining%26rarr; heat treatment (high temperature quenching and high temperature tempering)%26rarr; finishing%26rarr; nitriding%26rarr; finished product (Note: To save costs, Generally, manufacturers now omit the two time-consuming and expensive processes of forging and spheroidizing annealing).

Because Cr12MoV materials belong to high-carbon and high-chromium alloy steels, there is a large segregation of components in the original structure (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 appearance is extremely uneven (HRC about 40 to 60). After nitriding treatment, the uneven surface of the mold cannot be eliminated. The hardness is even further reduced. In actual use, the surface of the mold and the welded pipe is easy to strain, and the mold life is low.

The ultra-hardening treatment technology of the mold surface that has been researched by a company from Hu has been successfully applied to the forming mold of stainless steel welded pipe. The mold treated 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 picking 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. The following is a comparison between the process mold and the nitriding mold.

1. Performance:    nitriding mold The surface hardness of the mold treated by this process: HV700″ about 1000 HV3000    matrix hardness: extremely uneven HRC58″62   HRC40″60

2. Process flow:    nitriding mold: blanking %26rarr; rough machining %26rarr; heat treatment (high quenching and high recovery) %26rarr; finishing %26rarr; nitriding %26rarr; finished product, this process mold: blanking %26rarr; All processed in place (no heat treatment required)% 26rarr; this process treatment (matrix hardening and surface treatment are completed at one time). %26rarr; Grinding inner hole %26rarr; The finished product can be seen from the process flow. This process can shorten the mold processing cycle.

3. Use effect:   The mold processed by this process can fundamentally solve the fuzz of the welded pipe compared with the nitriding mold, 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). Improve the service life of the mold and reduce the workload of after-sales service.

The mold surface super-hardening treatment technology developed by a Hunan company has been widely used in actual production. The life of the mold treated by this process is greatly improved compared with the traditional process such as nitriding, and it exceeds the performance of some molds. Foreign level, and the price is only 1/4″1/10 of the foreign equivalent.

The molds processed by this process include rolls, punches, color tube series cold work molds, standard parts molds, pyrophyllite molds, copper-aluminum profile extrusion molds, etc., which have produced high benefits for customers and made the mold cost-effective. Quality improvement.