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Vacuum heat treatment technology (5)

Categories: ZCMIM NewsStars: 3StarsVisit: -Release time: 2019-12-12 08:48:00
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Vacuum annealing of mold


Vacuum annealing of mold (module) is easy to achieve no oxidation, no decarburization heat treatment, is conducive to improve quality of mold surface and production efficiency, shorten process cycle, and make mold surface brightness and microstructure uniform.


1. General vacuum annealing process

Mold annealing adopts a vacuum furnace (such as WZT series single-chamber vacuum furnace with ultimate vacuum degree of 0.1pa). Module is slowly heated to 870℃ at speed of 60℃/h. Holding time (2 ~ 4h) is determined according to size of module. Pressure of insulation stage should be controlled at 0.1 ~ 10Pa. During cooling, furnace cooling can be carried out in a vacuum state. When temperature is below 500℃, high purity N2 of 1×105Pa or mixture of high purity N2 and other reducing gases (such as H2) can be filled for cooling to ensure no oxidation and no coloring on surface of module. After annealing, hardness of module was below 235HBW and structure was pearlite + uniformly distributed granular carbide.


2. H13 mold steel isothermal annealing process

Vacuum furnace pressure 0.1 ~ 10Pa, slowly rose to 875 ~ 890℃ at ≤200℃/h and maintained for 2 ~ 4h, fast cooling to 710 ~ 740℃ maintained for 3 ~ 4h, with high purity nitrogen cooled to less than 100℃ and out.


3. Cr12MoV mold steel isothermal annealing process

Vacuum furnace pressure 0.1 ~ 10Pa, slowly rose to 830 ~ 870℃ at ≤200℃/h and maintained for 2 ~ 4h, then fast cooled to 720 ~ 740℃ for 3 ~ 4h, cooled to 100℃ with high purity N2 and out.


4. Vacuum carburizing of mold

Vacuum carburizing is to heat mold in vacuum furnace to austenitizing state, carburizing in carburizing atmosphere, and then diffusion and with quenching treatment. Because mould is heated in vacuum, surface of mould is very smooth and clean, which is suitable for carburizing treatment of mould with high surface quality.

  

5. vacuum carbonitriding of mold

Vacuum carbonitriding is a chemical heat treatment process in which mold surface layer is heated under negative pressure in vacuum furnace and infiltrates into C and N elements at same time. Compared with single carburizing, mold surface hardness is higher, wear resistance is better, corrosion resistance is certain and fatigue strength is higher. Due to low co-osmosis temperature and direct quenching after osmosis, austenite grains are smaller than single carburizing, so toughness of core of mold is improved, co-osmosis layer structure has no grain boundary oxidation phenomenon, and mold performance is significantly improved.


6. Mold vacuum pulse nitrocarburizing

The advantages of vacuum pulse nitrogen-carbon co - osmosis are preserved, such as inner wall of deep hole and impassable hole is uniform, better wear resistance and anti-bite than that of vacuum pulse nitriding. And white light layer is less, brittleness is small, permeate layer is dense, permeate rate is fast, and can bear heavy load and impact load.



Keywords in the article: Vacuum heat treatment
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