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Die - Casting Mould Conventional Heat Treatment Process
Jul 06, 2017

  Die - casting mould conventional heat treatment process

  Heat treatment process in the manufacture of die-casting mould is widely used, it can improve the use of mould parts performance, extend the service life of the mould. In addition, the heat treatment can also improve the processing of die-casting mould performance, improve processing quality and reduce tool wear, therefore, in the mould manufacturing occupies a very important position.

  Die-casting moulds mainly made of steel, the manufacturing process in the conventional heat treatment: ball annealing, stabilization treatment, quenching and tempering, Die - casting mould tempering. Through these heat treatment process to change the steel structure, so that die-casting mould to obtain the required organization and performance.

  Pre-processing

  Forging die die after forging, must be used ball annealing or quenching and tempering heat treatment, on the one hand to eliminate the stress to reduce the hardness, easy to cut, while the final heat treatment to do tissue preparation. After annealing, get a uniform structure and dispersion of the distribution of carbide, Die - casting mould in order to improve the strength of die steel. Since the effect of quenching and tempering treatment is superior to spheroidizing annealing, the moulds with high toughness and toughness are often used instead of spheroidizing annealing.

  2. Stabilized

  Die-casting moulds are generally more complex, in the rough processing will produce a greater internal stress, in the quenching will produce deformation. In order to eliminate the stress, generally after roughing should be stress-annealed, that is, stabilized.

  The process is: heating temperature 650 ℃ -680 ℃, insulation 2-4h after the baked air cooled. The shape of the more complex die-casting mould to be cold to 400 ℃ below the baked air-cooled. Die - casting mould Die quenching and tempering after the EDM, the processing surface will produce metamorphic layer, easy to cause wire cutting cracks, should also be lower temperature stress relief annealing.

  3. Quenching and preheating

  Die casting mould steel for the high alloy steel, because of its poor thermal conductivity, quenching in the heating must be slow, often take preheating measures. For the anti-deformation requirements of the mould is not high, Die - casting mould in the case of no cracking, the number of preheat can be less, but the anti-deformation requirements of high mould, must be preheated several times. Preheat at lower temperatures (400 ° C to 650 ° C), usually carried out in air furnaces. Preheating at higher temperatures should be carried out with a salt bath. The warm-up time is still at 1 min / mm.

  4. Quenching heating

  For a typical die-casting mould steel, high quenching temperature is conducive to improving the thermal stability and anti-softening ability to reduce the thermal fatigue tendency, but will cause grain growth and grain boundary formation of carbides, toughness and plasticity decreased, Leading to severe cracking. Therefore, the die-casting mould requires a higher toughness, often using low-temperature quenching, and require a high temperature strength, the use of higher temperature quenching.

  In order to obtain good high temperature performance, to ensure that the carbides can be fully dissolved, get the composition of the austenite, die casting mould quenching and holding time are relatively long, generally in the salt bath heating coefficient of 0.8-1.0 min / mm.

  5. Quenching and cooling

  For the shape is simple, anti-deformation requirements of the die-casting mould is not high oil and cold; and the shape of complex, anti-deformation requirements of high die-casting mould using grading quenching. In order to prevent deformation and cracking, no matter what the cooling method, are not allowed to cool to room temperature, generally should be cold to 150 ℃ -180 ℃, soaking immediately after a certain time tempering, soaking time can be 0.6 min / mm basis.

  6. Tempering

  Die casting mould must be fully tempered, generally tempered three times. The first tempering temperature selected in the secondary hardening temperature range; the second tempering temperature selection to make the mould to achieve the required hardness; third tempering lower than the second l0 ℃ -20 ℃. After the tempering are used oil or air cooling, tempering time of not less than 2 h.