2 solutions

Stainless steel sheet deep drawing process occurs seizing tumor has been plagued by production site, to producers a great deal of trouble, but because the adhesive neoplasia related to tribology and other issues affecting many factors. Currently, we can only propose measures to prevent the formation from different angles and to reduce the bond tumors.

2.1 mold work portion of the material selection and heat treatment

For bond tumor problem, select the mold material close relationship should note two points according to the pro-stainless steel sheet and the mold material: Choose one anti-adhesion and strong, and second, anti-friction wear-resistant mold material. In general, the metal lattice type, lattice spacing, electron density, electrochemical properties interlinked metal, which attract each other, dissolving ability, easy to adhere together, the results of the friction coefficient becomes large. Cr, Ni and Fe miscibility big, so when using steel deep drawing, bonding tumor phenomenon more likely. Practice has proved that: use aluminum bronze, aluminum bronze hard sticking better; the use of Steel bonded tungsten carbide manufacturing die than raise with Cr12Mov Nitrocarburising manufacturing die life several times, and non-stick mode; if using code 3054 alloy cast iron, just mold surface flame hardening, the mold surface will not bond tumors. Also in vulnerable parts of the mold can be used carbide inserts, it has excellent compression performance, superior wear resistance and long-lasting surface roughness and dimensional feeling of control. However, due to the price, the production used less.

Selection by factory limits, if the general high-carbon, high-chromium tool steel used stainless steel sheet drawing die, heat treatment hardness should reach more than 60HRC, the surface can be soft nitriding. As for improving the wear resistance of the mold and then increase the hardness of the steel in the drawing and will not bring improved adhesion phenomena. The key is to be in the heat treatment to remove residual austenite as possible, such as Cr12 a class of high hardness materials haggard fire using conventional technology, even if the limit range of hardness HRC62-64, the organization is still a considerable amount of residual austenite. Austenite both mold soft points, compared with martensite and affinity with the active agent in the lubricant is weak, difficult to establish a lubricating film. Therefore, after the heat treatment of these materials may be used to cool the fire approaches Cui low temperature, so that the residual austenite into martensite thereby improving the anti-adhesive matrix. In addition, to deal with stainless steel drawing die mold surface treatment to improve wear resistance, adhesion. For alloy cast iron or non-ferrous alloy materials molds take nitriding surface hardening process, the better the results.

2.2 mold surface finish working part

Stainless steel drawing die surface high quality requirements. Low surface roughness can play friction and improve the anti-adhesion effect therefore. After drawing die during the grinding process, more importantly, it is to eliminate machining marks. In the mold it is often overlooked grinding and polishing process. It should be noted. In the entire mold process, polishing workload should account for one third, due to the appearance of quality steel products depends largely on the mold polishing techniques. Mold surface roughness was reduced, a corresponding reduction in the number of grinding mold, die life is improved accordingly.

If the mold surface polishing is not enough, in addition to stainless steel sheet drawing characteristic of the bond can lead to tumors, thus drawing out of the product scratches serious. And that this scratches on the product with a polishing process to solve time-consuming and not achieve results. Therefore, we should step up and down in the mold polishing great effort, only the mold surface machining accuracy is improved in order to reduce scratches, mold repair mold life can be greatly improved. In recent years, there have been all kinds of polishing and polishing tools of new technology, the development of ultrasound, electrolytic polishing, abrasive blasting, extrusion honing new techniques and new equipment. According to information on CrWMo, 3Cr12W8V, Cr12 mold test three materials Electrochemical polishing, polishing in just 5-10 minutes to prove that you can make the mold cavity surface roughness from the original Ra3.2-Ra1.6 reduce to Ra0.4-RaO.2 basis. While by electrochemical polishing may improve the surface hardness to improve wear resistance. In another example, ultrasonic polishing machine can be used by Nitrocarbarizing cavity fine polish, it can avoid the shortcomings hand-polished easily damaged nitride film. For new polishing techniques we should take active steps to use and summary.

2.3 Lubrication Technology

Drawing properties seen from stainless steel to form an adhesive sheet because the tumor occurs in direct contact with the mold, it is an indisputable fact that in theory, so choose the first point lubricant or coating agent is in the sheet metal deep drawing process Throughout the lubricating film does not rupture and act as a lubricant. "Sticking down Mount" is the choice of lubricant basic starting point.

The general increase in the lubricant certain percentage of extreme pressure additives or using a solid lubricant can achieve better results. This is mainly to improve the lubricant for lubricating the metal surface of the ability to produce a sulfur adsorption capacity, phosphorus, chlorine compound with a metal surface at a high temperature from a chemical reaction to produce iron sulfide, iron chloride, etc. to strengthen and enhance the film strength , preferably lubricated mold with the product surface. The solid lubricant is filled in the metal surface small pit, and the dry frictional contact points reduced to a minimum, while the solid lubricant has a high stability at high temperatures can also play a lubricating role, less prone to die bonding. Typically in the production of products based on the degree of deformation and actual selection and formulation (manual can be found stamped on the relevant recipe).

In addition, the fat, mineral oil, synthetic oil, grease, soap can also be composed of a lubricant, and the stainless steel shallow drawing better. Organic and mineral oil-containing aqueous emulsions, or oil may also be used to dilute the shallow drawing. Join graphite lubricant can play the role of anti-adhesion but more difficult to clean graphite added after. Such as the selection code 3054 alloy cast production molds, so the choice of lubricant effects are generally good.

According to the data sheet can be obtained by a metal salt treatment soft mode (such as copper, zinc, lead) on the surface, deep drawing process does not appear the phenomenon of stick mode. Further, in recent years developed a polyvinyl butyral as the main lubricating film of an organic polymer, treated rough surface to obtain a layer of an organic lubricant film, which together with the sheet of deformable material, which not only avoids the mold Direct contact with the sheet to prevent the sticky mode, to ensure that the product surface quality. But also greatly reduced the friction of the mold and the sheet metal, and play a good lubrication, experiments show good results.