1. Effect of heating speed

一般来说，淬火加热时，加热速度越快，则模具中产生的热应力越大，易于造成模具的变形开裂。尤其对于合金钢及高合金钢，因其导热性差，尤需注意进行预热，对于一些形状复杂的高合金模具，还需采取多次分级预热。

Generally speaking, when quenching and heating, the faster the heating speed, the greater the thermal stress generated in the die, which is easy to cause the deformation and cracking of the die. Especially for alloy steel and high alloy steel, due to their poor thermal conductivity, special attention should be paid to preheating. For some high alloy molds with complex shapes, multiple staged preheating should be adopted.

但在个别情况下，采用快速加热有时反而可以减少变形，这时仅加热模具的表面，而中间还保持冷态，所以相应地减少了组织应力和热应力，且中部变形抗力较大，从而减少了淬火变形，根据一些工厂经验，对于孔距变形方面有一定效果。

However, in some cases, rapid heating can sometimes reduce deformation. At this time, only the surface of the die is heated, and the middle is still cold, so the organizational stress and thermal stress are reduced accordingly, and the deformation resistance in the middle is large, so the quenching deformation is reduced. According to some factory experience, it has a certain effect on solving the hole spacing deformation.

2、加热温度的影响

2. Effect of heating temperature

淬火加热温度的高低影响材料的淬透性，同时对奥氏体的成分与晶粒大小起作用。

The quenching heating temperature affects the hardenability of the material and the composition and grain size of austenite.

(1) 从淬透性方面看，加热温度高，将使热应力变大，但同时使淬透性更高，因此组织应力也变大，并逐渐占主要地位。例如，碳素工具钢T8、T10、T12等，在一般淬火温度淬火时，内径表现为缩的倾向，但若提高淬火温度到≥850℃时，则由于淬透性更大，组织应力逐渐占主要地位，因而内径可能表现为胀的倾向。

(1) From the aspect of hardenability, high heating temperature will increase the thermal stress, but at the same time, it will increase the hardenability, so the tissue stress will also increase and gradually occupy the main position. For example, when carbon tool steels T8, T10, T12, etc. are quenched at general quenching temperature, the inner diameter tends to shrink, but if the quenching temperature is increased to & Ge; At 850 ℃, due to the greater hardenability, the tissue stress gradually occupies the main position, so the inner diameter may show the tendency of swelling.

(2)从奥氏体成分看，淬火温度提高使奥氏体含碳量增加，淬火后马氏体的正方度更大(比容更大)，从而使淬火后体积更大。

(2) From the perspective of austenite composition, the increase of quenching temperature increases the carbon content of austenite, and the squareness of martensite after quenching is larger (specific volume is larger), so that the volume after quenching is larger.

(3)从对Ms点影响细看，淬火温度高，则奥氏体晶粒粗大，将使零件的变形开裂倾向更大。

(3) From the influence on MS point, if the quenching temperature is high, the austenite grain is coarse, which will make the deformation and cracking tendency of parts greater.

综合上述，对所有的钢种，尤其是某些高碳的中、高合金钢，淬火温度的高低会明显影响模具的淬火变形，因此，正确选择淬火加热温度是很重要的。

Based on the above, for all steel types, especially some high-carbon medium and high alloy steels, the quenching temperature will significantly affect the quenching deformation of the die. Therefore, it is very important to correctly select the quenching heating temperature.

一般来说，选择过高的淬火加热温度对变形是没有好处的。在不影响使用性能的前提下，总是采用较低的加热温度。但对一些淬火后有较多残余奥氏体的钢号(如Cr12MoV等)，也可通过调整加热温度，改变残余奥氏体量，以调节模具的变形。

Generally speaking, choosing too high quenching heating temperature is not good for deformation. On the premise of not affecting the service performance, always use a lower heating temperature. However, for some steel grades with more retained austenite after quenching (such as Cr12MoV), the amount of retained austenite can also be changed by adjusting the heating temperature to adjust the deformation of the die.

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