Several methods for reducing the formation of bond nodules during the deep drawing of stainless stee

Due to the problem that the stainless steel plate is prone to sticking lumps during the deep drawing process, it has always troubled the producer, causing great trouble in production. However, because the formation of sticking lumps involves tribology and other issues, there are many influencing factors. The following measures are proposed from different angles to avoid and reduce the formation of sticky nodules.

There are mainly the following points.
The first is to select the appropriate material for the working part of the mold and carry out the corresponding heat treatment
In terms of mold materials, on the one hand, you can choose a mold material with strong adhesion resistance, and on the other hand, you can choose a mold material with wear resistance and friction reduction. Generally, metals with the same lattice type, lattice spacing, electron density, and electrochemical properties have mutual attraction and strong solubility, and are easy to stick together, which will increase the friction coefficient. The mutual solubility of chromium, nickel and iron is relatively large, so when using a steel die to draw, it is more likely to produce sticking nodules. It has been proved by practice that the selection of cast aluminum bronze, hard aluminum bronze and other materials has a better anti-stick effect; the use of tungsten carbide steel bonded cemented carbide to manufacture a die is several times longer than that of Cr12Mov soft nitriding to manufacture a die, and it is not sticky. Mold; if the code name is 3054 alloy cast iron, as long as the corresponding flame quenching is performed on the mold surface, the mold surface will not produce sticking nodules. In addition, cemented carbide inserts can be used in the easily damaged parts of the mold, which have excellent compression resistance, wear resistance and good surface roughness and dimensional control. But the disadvantage is that it is more expensive.

Restricted by the factory's selection of materials, if ordinary high-carbon and high-chromium tool steel is used as a stainless steel sheet drawing die, the heat treatment hardness must reach 60HRC or more, and the surface can be nitrocarburized. If the hardness is increased to enhance the wear resistance of the die, the bonding phenomenon in the deep drawing of stainless steel will not be improved. The key point is to remove as much retained austenite structure as possible during heat treatment. For example, high hardness materials such as Cr12 use the ordinary haggard process. Even if the limit hardness range of HRC62-64 is reached, a considerable amount of austenite will remain in the structure. body. Austenite is not only a soft spot in the mold, but also has a weaker affinity with the active agent in the lubricant compared with martensitic stainless steel, so it is not easy to build a lubricating oil film. Therefore, the heat treatment of this material can use a low-temperature treatment method after annealing and cooling, so that the retained austenite is transformed into martensite to improve the adhesion resistance of the matrix. In addition, the surface treatment of the stainless steel deep drawing die is also required to enhance the wear resistance and adhesion resistance of the die. Surface strengthening processes such as nitriding are used for molds made of alloy cast iron or non-ferrous alloy materials, and the use effect is better.

The second is to perform appropriate surface processing on the working part of the mold
The surface quality requirements of the deep drawing die for stainless steel plates are very high. Relatively low surface roughness can reduce friction and enhance adhesion resistance. Therefore, after the corresponding grinding process of the drawing die, it is more important to remove the processing marks. In mold manufacturing, grinding and polishing processes are usually ignored. It should be pointed out that in the entire mold processing process, the polishing workload accounts for about one-third, because the appearance quality of the stainless steel plate product is largely affected by the mold polishing technology. The surface roughness of the mold is reduced, the number of mold repairs will be reduced accordingly, and the service life of the mold will be increased accordingly.

The third is to use process lubrication
From the deep drawing characteristics of the stainless steel sheet, it can be seen that the reason for the formation of the sticking tumor is that the sheet metal and the die are in direct contact, so the first point of choosing a lubricant or coating agent is that the lubricating film will not be broken from the beginning to the end during the sheet metal deep drawing process. And can play a lubricating role. Therefore, the principle of selecting lubricants is to prevent viscosity and reduce friction.

Usually adding a certain proportion of extreme pressure additives to the lubricant or using solid lubricants can achieve relatively good results. This is mainly to enhance the lubricating ability of the lubricant to the metal surface, which is used to generate compounds containing sulfur, phosphorus and chlorine to chemically react with the metal surface at high temperature to generate iron sulfide, iron chloride, etc. to strengthen the oil film strength and enhance the adsorption capacity. , better lubricate the mold and product surface. The solid lubricant is filled into the small pits on the metal surface to minimize the dry friction contact points. In addition, the solid lubricant has high stability and good lubrication at high temperatures, and it is not easy to produce mold bonding.