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Analysis of heat treatment process of cast iron in casting foundry
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Release time:
2024-05-20
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The hardness of white cast iron is high, it cannot be machined, and it is very brittle, so it is rarely used directly to make machine parts. Generally speaking, it is very important to select a reasonable heat treatment process according to the chemical composition and working conditions of cast iron. Generally, the commonly used heat treatment processes are stress relief annealing, softening annealing or normalizing, quenching and tempering, etc. Most other white cast iron parts are billets of malleable cast iron. Graphitization annealing is required to decompose most or all cementite to form floc (or spherical) graphite, conversion of white cast iron to malleable cast iron.
It is mostly used for high silicon and high chromium alloy white cast iron. Due to the large internal stress of casting, if the remaining internal stress is not eliminated in time for self-made parts, it will constitute self-cracking in the process of vibration or environmental changes. Generally, the annealing heating of cast iron parts is relatively low, while for high-alloy white-mouthed cast iron parts, the white-mouthed cast iron structure is relatively stable, so the annealing temperature is relatively high. the selected process specification is 800~900 ℃ × 1~4h. after the heat preservation, the cast iron parts are cooled to 100~150 ℃ and discharged into the furnace for air cooling.
On some of the hardenability of the larger alloy white cast iron, cast iron has a lot of martensite, but less cementite, high hardness, selection of parts made of this kind of material requirements for cutting, it is necessary to use softening annealing process to transform martensite into pearlite, and then reduce the hardness of cast iron to the extent that can be processed.
It is mostly used for high silicon and high chromium alloy white cast iron. Due to the large internal stress of casting, if the remaining internal stress is not eliminated in time for self-made parts, it will constitute self-cracking in the process of vibration or environmental changes. Generally, the annealing heating of cast iron parts is relatively low, while for high-alloy white-mouthed cast iron parts, the white-mouthed cast iron structure is relatively stable, so the annealing temperature is relatively high. the selected process specification is 800~900 ℃ × 1~4h. after the heat preservation, the cast iron parts are cooled to 100~150 ℃ and discharged into the furnace for air cooling.
On some of the hardenability of the larger alloy white cast iron, cast iron has a lot of martensite, but less cementite, high hardness, selection of parts made of this kind of material requirements for cutting, it is necessary to use softening annealing process to transform martensite into pearlite, and then reduce the hardness of cast iron to the extent that can be processed.
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