Abstract: The solid sulfurizing treatment process can improve the wear resistance of the cold pier mold, basically eliminate the sticking phenomenon in use and improve the service life of the mold.
Our company used the GCrl5 overall mold cold pier roller when the life is generally about 2000 grains, and there are obvious swelling and padding phenomenon at around 1000 grains. In order to improve the life of the mold and reduce the consumption of the mold, the newly designed mold was trial-produced. In order to reduce the cost of the mold, the medium mold and the core were made of 7Cr7Mo2V2Si steel, and the others were all made of GCrl5 steel, as shown in Figure 1. During the trial, the material was found to be tacky, resulting in the mold core not being damaged when the pier was less than 300. However, due to the sticking, the roller blank appeared severely falling off, the blank size was too poor, and the mold was scrapped.
After a large number of tests, it was found that the solid sulfurizing treatment process can improve the wear resistance of the mold and at the same time increase the surface roughness by 1-2. After sulphurization treatment, a 0.1-0.3mm thick FeS film is formed on the surface of the metal, which has good self-lubricating properties. At the same time, due to the porous property of FeS, the lubricating oil can be adsorbed, and the oil film which is not easily crushed is easily formed, thereby reducing The bite force between the molecules during rubbing substantially eliminates the sticking phenomenon and greatly improves the service life of the mold. The process also has the advantages of simple operation and no harm to the human body. The process is as follows:
(1) Preparation work. Before the sulphurization treatment, the mold is subjected to degreasing, and after drying in hot water, it is dried. The lye chemical degreasing method can be used as needed.
(2) Method of compounding. The composition of the solid sulfurizing agent is 94% iron sulfide, 3% ammonium chloride and 3% graphite (powdered graphite prevents the mold surface and the sulfurizing agent from sticking together). During the preparation, the iron sulfide is crushed into a powder, sieved with a 50-100 mesh sieve, stirred uniformly with the powdered graphite, and finally ammonium chloride is added. In the second preparation, the ratio of new and old osmium flux is 1:4.
(3) Specific steps.
1 When packing, first sprinkle a layer of 20-30mm thick sulphurizing agent on the bottom of the box, then put the mold on the mold, the mold is separated by 15-20mm, and the lid is closed with refractory mud.
2 furnace temperature 540-560 ° C, insulation 3-4h. After the sulphur treatment, the whole box is taken out and air cooled. When the temperature is lowered to below 100 °C, the mold is taken out and the mold is cleaned in hot water.
3 Heat in hot oil at 110-125 ° C for 5-10 min to prevent corrosion, then wipe the mold with sawdust.
4 temper at 200-220 ° C, 2-3h to reduce the temper brittleness of the mold.
After sulphurization, the surface of the mold is gray and the hardness is generally increased by 1-2 HRC. No sticking phenomenon was found in the mold pier to more than 10,000 pieces, and the cold pier blank was normal, the quality was qualified, the dimensional change was small, and the die life was significantly improved.
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