plastic mould, injection mould

Mold Heat Treatment and prevention of defects

1. Mold surface has soft spots

    After heat treatment, surface mold soft spots, mold will affect the wear resistance and reduce die life.

    (1) causes

    1) die in the heat treatment before the surface oxide skin, pitting and local decarburization.

    2) die quenching heating, cooling quenching medium the inappropriate choice of quenching impurities in the medium too much or aging.

    (2) Preventive measures

    1) The mold should be removed before heat treatment oxide skin, pitting, in the quenching adequate protection when heated mold surface, should maximize the use of a vacuum furnace, salt bath furnace and the protection of the atmosphere oven.

    2) die quenching heated cooling, they should choose a suitable cooling medium, cooling medium to the long-term use should always be filtered, or periodic replacement. 2. Die poor organization before heat treatment

    Mold the final ball of the organization coarse uneven, the ball of imperfect organization mesh, ribbon and chain carbon, which will die in quenched easy to crack, resulting in mold scrapped.

    (1) causes

    1) die steel materials, the original organizations, there are serious carbide segregation.

    2) The forging process poor, such as forging heating temperature is too high, distortion is small, stop forging temperatures are high, and slow cooling rate after forging to forging the organization and a coarse mesh, ribbon, and chain-like carbon exists, so that the ball annealing it difficult to eliminate.

    3) spheroidizing poor, such as the annealing temperature is too high or too low, such as temperature and shorter annealing time, annealing can cause the ball or the ball of the organization inequality bad.

    (2) Preventive measures

    1) The general conditions of work should be based on the mold, the production volume and material toughening its own performance, as we choose a good quality mold steel.

    2) Improving the forging process or prepared using normalizing heat treatment, to eliminate the raw material in the mesh and chain carbide and carbide heterogeneity.

    3) can not be forged high-carbon carbide segregation serious die steel can be refined solution heat treatment.

    4) after the die forging billet formulate the correct spheroidizing specification, can be used quenched and tempered heat treatment and rapid absorption fine ball annealing work.

    5) reasonable loading furnace to ensure that mold billet furnace temperature uniformity. 3. Mold produces quenching cracks

    Die in die after quenching cracks is the biggest drawback of the process of heat treatment will make a good mold scrap processing, production and caused great economic losses.

    (1) the causes

    1) mold material there is a serious mesh carbide segregation.

    2) the existence of mold machining or cold plastic deformation of stress.

    3) improper operation mold heat treatment (heating or cooling too fast, the inappropriate choice of quenching medium, cooling the temperature is too low, cooling time is too long, etc.).

    4) The mold shape of the complex, uneven thickness, with sharp corners, and threaded holes, so that thermal stress and organizational stress is too large.

    5) die quenching heating temperature is too hot or too burned produced.

    6) The mold is not timely or tempering after quenching tempering heat preservation time is insufficient.

    7) when heated mold rework quenching without intermediate annealing and quenching heat again.

    8) mold heat treatment, grinding process improper.

    9) After heat treatment, EDM die, the hardened layer in the presence of high tensile stress and micro-cracks. (2) Preventive measures

    1) strict control over the intrinsic quality of raw materials, mold

    2) Improvement of forging and the spheroidization annealing process, eliminating mesh, ribbon, chain-like carbide, to improve the uniformity of the ball of the organization. ,

    3) In the post-machining or cold plastic deformation of the mold should be conducted to stress annealing (> 600 ) and then heated quenching.

    4) The complex shape of the mold should be used to plug screw holes of asbestos, dressing dangerous section and thin-walled office, and to adopt a classification quenching or austempering.

    5) repairing or renewing die when in need of high-temperature annealing, or tempering.

    6) mold in the quenching should be taken to preheat heating and cooling to take pre-cooling measures, and choose a suitable quenching medium.

    7) should be strictly controlled quenching heating temperature and time, to prevent overheating and over-burning mold.

    8) die promptly after quenching tempering, heat preservation time should be adequate, high-alloy complex molds should be tempered 2-3 times.

    9) Select the correct grinding process and the right wheel.

    10) Improvement of mold EDM process, and conduct to the stress of temper. 4. Die quenched coarse Organization

    Die after quenching the organization thick, will seriously affect the mechanical properties of the mold, will be used to make molds crack, seriously affect the die life.

    (1) the causes

    1) die steel confusion, the actual temperature is far below the requirements of steel hardened mold material of the quenching temperature (if the GCr15 steel as 3Cr2W8V steel).

    2) die steel hardened before the ball is not correctly processing technology, the ball of the organization bad.

    3) die quenching heating temperature is too high or too long holding time.

    4) die in the furnace improper placement, in the area near the electrodes or the heating element easy to produce overheating.

    5) changes in the larger cross-section mold, hardening heating process parameters properly, in thin sections and sharp corners at produce overheating.

    (2) Preventive measures

    1) The steel should be strictly tested before storage, prevent misplacing steel confusion.

    2) die quenching should be carried out before the proper forging and annealing the ball in order to ensure a good ball of the organization.

    3) the right to develop mold quenching heating process specifications, strict control of quenching heating temperature and holding time.

    4) periodic testing and calibration Thermometer to ensure the instrument work properly.

    5) The mold should be heated in the furnace with the electrodes or the heating element to maintain an appropriate distance.



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