Reasons and Countermeasures for Insufficient Hardness of Furniture Mould

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The heat treatment hardness of Furniture Mould(FURNITUREMOULD) is a very important mechanical property index, and unqualified hardness is a very serious defect. The inadequate or uneven hardness of furniture dies after heat treatment will reduce the wear resistance and fatigue strength of furniture dies, which will lead to Early failure of furniture dies and seriously reduce the service life of furniture dies.

1. Cause

(1) The furniture mould has a large cross-section, and the hardenability of the steel is poor. For example, a large mould has steel with low hardenability.

(2) Carbide segregation or coarse structure in the original structure of furniture mould steel, segregation and aggregation of graphite carbon and carbide in steel.

(3) The forging process of furniture mould is not correct. After the forging, the spheroidizing annealing is not performed well, and the spheroidized structure of the mould steel is poor.

(4) The decarburization layer produced on the surface of the furniture mould is not cleaned or quenched.

(5) The quenching temperature of the furniture mould is too high, and the amount of retained austenite is too much after quenching; or the quenching temperature is too low, the heating and holding time is insufficient, and the phase transformation of the mould steel is incomplete.

(6) The cooling speed of the furniture mould after quenching is too slow, the grading and isothermal temperature are too high or the time is too long, and the quenching cooling medium is improperly selected.

(7) The alkali bath has too little moisture, or the quenching cooling medium contains too many impurities, or the quenching cooling medium is aged.

(8) When the furniture mould is quenched and cooled, the temperature of the quenching cooling medium is too high and the cooling is insufficient.

(9) Insufficient tempering and excessive tempering temperature.

2. Countermeasures

(1) Correct selection of furniture mould steel, large moulds should use high alloy mould steel with high hardenability.

(2) Strengthen the inspection of raw materials to ensure that raw materials meet the standards. Reasonable forging of the raw material steel and spheroidizing annealing to ensure good organization. Carbon tool steels are not easily annealed multiple times to prevent graphitization.

(3) Strictly perform the forging process and the spheroidizing annealing process to ensure a good preliminary heat treatment structure.

(4) Before heat treatment, thoroughly remove the rust and scale on the surface of the furniture mould, and pay attention to the protection during heating. Try to use vacuum heating quenching or protective atmosphere to heat and quench. When the salt bath is heated, it should be well deoxidized.

(5) Correctly formulate the process parameters of the furniture mould quenching heating to ensure sufficient phase change, and rapidly cool at a cooling rate greater than the critical cooling rate to obtain a qualified metallographic structure.

(6) Correctly select the quenching cooling medium and cooling method, and strictly control the classification and isothermal temperature and time.

(7) To strictly control the moisture content of the alkali bath, the quenching and cooling medium used for a long time should be regularly filtered and periodically replaced, and kept clean, and the quenching cooling characteristic curve is periodically checked.

(8) For large-sized furniture mould, properly extend the time of immersion in the quenching cooling medium to prevent the temperature of the quenching cooling medium from being too high.

(9) After the furniture mould is quenched, it should be tempered in time and fully, and the tempering temperature should be prevented from being too high.

(10) Furniture mould with high hardness requirements can be subjected to cryogenic treatment (eg -110 to -196 C).

(11) Surface strengthening treatment.

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