1. Effect of heating speed

一般來說，淬火加熱時，加熱速度越快，則模具中產(chǎn)生的熱應(yīng)力越大，易于造成模具的變形開裂。尤其對于合金鋼及高合金鋼，因其導(dǎo)熱性差，尤需注意進(jìn)行預(yù)熱，對于一些形狀復(fù)雜的高合金模具，還需采取多次分級預(yù)熱。

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.

但在個別情況下，采用快速加熱有時反而可以減少變形，這時僅加熱模具的表面，而中間還保持冷態(tài)，所以相應(yīng)地減少了組織應(yīng)力和熱應(yīng)力，且中部變形抗力較大，從而減少了淬火變形，根據(jù)一些工廠經(jīng)驗，對于孔距變形方面有一定效果。

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、加熱溫度的影響

2. Effect of heating temperature

淬火加熱溫度的高低影響材料的淬透性，同時對奧氏體的成分與晶粒大小起作用。

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

(1) 從淬透性方面看，加熱溫度高，將使熱應(yīng)力變大，但同時使淬透性更高，因此組織應(yīng)力也變大，并逐漸占主要地位。例如，碳素工具鋼T8、T10、T12等，在一般淬火溫度淬火時，內(nèi)徑表現(xiàn)為縮的傾向，但若提高淬火溫度到≥850℃時，則由于淬透性更大，組織應(yīng)力逐漸占主要地位，因而內(nèi)徑可能表現(xiàn)為脹的傾向。

(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)從奧氏體成分看，淬火溫度提高使奧氏體含碳量增加，淬火后馬氏體的正方度更大(比容更大)，從而使淬火后體積更大。

(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)從對Ms點影響細(xì)看，淬火溫度高，則奧氏體晶粒粗大，將使零件的變形開裂傾向更大。

(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.

綜合上述，對所有的鋼種，尤其是某些高碳的中、高合金鋼，淬火溫度的高低會明顯影響模具的淬火變形，因此，正確選擇淬火加熱溫度是很重要的。

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.

一般來說，選擇過高的淬火加熱溫度對變形是沒有好處的。在不影響使用性能的前提下，總是采用較低的加熱溫度。但對一些淬火后有較多殘余奧氏體的鋼號(如Cr12MoV等)，也可通過調(diào)整加熱溫度，改變殘余奧氏體量，以調(diào)節(jié)模具的變形。

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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