Analysis of technical application status in cemented carbide mould industry
The carbide blank of Huicong Hardware Net has a long service life and a short service life after being processed into a mold. After anatomical analysis, the problem is found in design, processing, assembly and welding.
1. technical condition of cemented carbide mold design
Wire drawing die is a relatively simple mold. Before the 1980s, China has been using the Soviet Union's "straight line" theory design, after the 1980s, some manufacturers quoted the "smooth transition" technology theory put forward in the 1950s.
In recent years, Chinese scholars have designed the angle of drawing die and analyzed the theory of ring groove wear, put forward the concept of maximum and minimum drawing angle, and analyzed the mechanism of uneven wear of metal in the process of drawing deformation. Researchers at Guangdong Institute of Technology dissected and analyzed the carbide die for small size cold pier screws. The secret of low life of domestic die (2-4 million times) and high life of Japanese die (9-10 million times) was found. The key technology was angle design. That is, the Japanese mold is designed with the double convex surface at the bottom of the mold core and the center contact part of the inner hole of the mold sleeve. Its advantage is that it can make the center of the maximum force to ensure tight pressure, and the space left around can be used for interference fit, storage of excess metal extruded from the hole wall. The cemented carbide die for Ml2 nut of cold pier in Shenyang Bridge Works was changed from hexagonal design to six-petal knitting and inserting. The average life of the die is 500,000 pieces/die, and the height is 1.2 million pieces/die. The author thinks that this design is reasonable. First, it saves cemented carbide compared with the integral structural design die. Second, it is easy to assemble. Third, it is easy to replace the die and can replace the damaged one.
2. The influence of machining and assembling technology on cemented carbide dies Dimensional and positional accuracy of cemented carbide dies is achieved by grinding. The grinding force of cemented carbide is 2-3 times the grinding force of general steel. Therefore, the power of the grinder to be large, rigid to be high, as far as China's current level of machine tools, there is no special grinder for processing cemented carbide. It often causes machining errors, and the cumulative effect of errors will seriously damage the service life of dies. In the process of EDM, due to the action of high temperature and liquid medium up to 10000 C, the surface microstructure of dies will change, carburizing (carbon in working fluid), metal carburizing (copper-tungsten electrode), and even micro-cracks will undoubtedly affect the life of dies. Inserts are designed to enable the alloy to withstand greater impact and extrusion load, whether hot-pressed or cold-pressed inserts, the gap requirements are very strict. Normally, the interference of 0.03-0.05 mm is chosen for cold-pressed insert, 0.08-0.1 Omm for hot-pressed insert, 700-800 C for cavity and 300 C for cemented carbide. After hot pressing, heat the 2h in the 600 box furnace to eliminate stress.
Cemented carbide welding is also a key technology. Brazing is usually used. The Hunan Institute of Metallurgical Materials has developed a kind of nickel-based brazing filler metal for Xi'an Aircraft Engine Manufacturing Company. It has achieved good results in brazing cemented carbide in vacuum furnace.
Application Status of Non-standard Cemented Carbide and New-type Cemented Carbide Dies 1. Application Status of Non-standard Cemented Carbide Die Blanks The so-called Non-standard Cemented Carbide Die Blanks refer to the profiled blanks not listed in the national standards. In this respect, magnetic and progressive dies are used more frequently. Non magnetic modules are usually made of YGl5 or YG2O cemented carbide. For example, the 899 factory in Sichuan uses YGl5 to make soft magnetic die. The Jiangxi optical instrument factory uses YG2O and YG2OC as soft magnetic mirror punching dies. When the Ni-base alloy IJ5O is impacted, the mirror parallelism is 0.0O5mm and the roughness Ra is 0.2Um. The efficiency of the impacted Ni-base alloy is several times higher than that of the lapped Ni-base alloy. Zigong radio No. 1 factory uses YWC non-magnetic cemented carbide as the soft magnetic material forming die with a life span of 50-100 million times. YGl5, YG2O and YG2OC are the main selection for single or multi-position progressive dies, and steel bonding alloy is also selected. For example, the combined progressive die for the wheel slices made of cemented carbide in Shanghai Watch Factory works 2.16 million times at 300-400 times per minute, producing 4 million qualified products with high precision. The stator progressive die also produces nearly 1 million qualified products at a rate of 300 /min. The stator and rotor iron core of the motor in Nanjing Changjiang Machinery Plant can be punched 500,000 times at one time, with a total life of 50-60 million times. The multi-position progressive die for cemented carbide of Jiangsu Huajing Electronics Group has a total life of about 50 million times when the lead frame material is punched at 400-600 times per minute. The progressive blanking die for the electrical appliances plug-in products of Dalian Electric Machinery Works has been replaced by domestic cemented carbide. Its service life is over 70 million times and the time is over 2 years. In recent years, cemented carbide materials have been used in forming die for powder metallurgy products. For example, the YG8 die can be pressed 700 thousand products per ton, while the steel die is only I000 times plant vice high chrome steel vice. YG8 is used as the shaping die for bimetal axle sleeve in Shanghai Changjiang Machinery Factory. The life of the die is over 100 square pieces, while that of GCrl5 is only 1000 pieces.
2. The development of new cemented carbide die materials in the development of new cemented carbide materials, in recent years to replace cobalt with iron nickel hot. For example, the high strength and toughness cemented carbide equivalent to YG15, YG2O and YG25 developed by Hunan Metallurgical Materials Research Institute has achieved good results in cold pier dies and cold extrusion dies. The Tianjin Cemented Carbide Research Institute has also developed GY (15-20) cemented carbide die materials by replacing cobalt with iron-nickel, which are used in rolling forging of standard parts and cold piers with steel balls. It works well with YG2O. In recent years, new research focuses on fine-grained, ultrafine grains, and even nanocrystalline hard bonding.