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Medium carbon alloy spring steel is the basic steel grade for standard cold heading punches. This steel has the advantages of yield strength, high fatigue limit, high hardenability, large plasticity, good plasticity, low price and simple heat treatment operation process. This steel has obvious decarburization tendency, which will significantly damage the wear resistance and fatigue resistance. It is also susceptible to overheating and quenching cracks.
Processing technology
When the steel is used as the main part of the mold, it must be forged first to avoid longitudinal cracking. However, in order to eliminate the stress after forging and make the internal carbides of the steel uniform, spheroidizing annealing must be performed to increase the service life of the die steel. However, the steel does not need to be spheroidized annealed when used to make springs.
If rapid spheroidization process heat treatment is used to replace the traditional spheroidization annealing process, the spheroidization structure can be made more uniform, the spheroidization rate can be increased, product quality can be improved, and the production cycle can be shortened by half. The use of low-carbon martensite high-temperature quenching is beneficial to extending the life of cold work dies.
You can obtain more low-carbon martensite structure by increasing the austenitization temperature to increase the point of the steel, improve the strength and toughness of the mold, and have higher fracture toughness, impact toughness and excellent wear resistance. The hardness of the mold after quenching and tempering is r. The metallographic structure is flake tempered martensite + retained austenite. The sensitivity to microcracks is high, so the toughness is low, and it is easy to break during use.
Compared with ordinary quenching, the hardness obtained by the austempering process is only different by r, but the bending strength and toughness are greatly improved.
Process specifications
Specifications for softening treatment of cold-pressed blanks: temperature ~ ℃ holding time ~ cooling speed of ~ ℃ / with the furnace down to temperature ℃ out of the furnace air cooling. Hardness before treatment and hardness after treatment.
Quenching and tempering specifications: quenching temperature ℃, oil cooling and tempering temperature ℃℃.
Isothermal quenching and tempering specifications: temperature ℃, keep warm, come out of the furnace, oil-cooled, immediately put into ℃ nitrate salt bath, isothermal, come out of the furnace, air-cooled.
Best heat treatment specifications: Preparatory heat treatment: ℃ oil cooling quenching ℃ heating and insulation quenching to ℃ insulation furnace cooling to ℃ air cooling out of the furnace.
Final heat treatment process: quenching temperature ℃ isothermal temperature ℃ isothermal time
Critical point temperature (approximate value) ℃℃r =℃r =℃=℃.
Hot working specifications: initial forging temperature ℃, final forging temperature ℃.
Typical application examples
The service life of the steel cold heading nut punching die after high-temperature quenching, -℃ quenching and tempering is about three times longer than that of the mold quenched at normal temperature.
The main parts of a non-standard gasket cold stamping die for a dump truck require high hardness, high strength, good impact resistance and good toughness, and are generally made of cold stamping die. However, the price of this steel is high, and the supply and heat treatment are difficult, so we have to use steel to make cold stamping dies. However, due to the poor toughness and high brittleness of steel, the left and right punching parts of each mold are damaged. The steel is used to make the main parts of the cold punching die and is quenched and tempered to greatly extend the life of the mold.
This steel can be used for internal and external hexagonal bolt forming cold heading punches, carbide die prestressed sleeves (-r), medium-thick steel plate piercing punches, etc.
The service life of cold heading punches made of hexagon socket screws using this steel exceeds .
, mostly used in the manufacturing of cold stamping, cold heading punches, nut cold heading dies, punching dies, etc. in small enterprises.
, It is the basic material for various punching and shearing tools, extrusion dies, and cold heading dies
This steel can be used to punch gaskets after spheroidizing annealing, quenching, and tempering according to traditional heat treatment processes. -. Ten thousand pieces of mold punchable gaskets using rapid spheroidization process and isothermal quenching. The service life of more than ten thousand pieces has been doubled.
Using the spheroidizing annealing process on the steel, the service life of the cold punched film can be doubled.
Using rapid spheroidization process and performing ℃ austenitization and ℃ isothermal quenching, the life of the grinding tool can be doubled compared with the traditional heat treatment process.
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