Heating speed and heating time of steel forging

The heating speed indicates how fast the temperature rises when the metal is heated. It is expressed by the temperature rise per unit time (℃/h), and it can also be expressed by the thickness of the metal layer that is heated per unit time (mm/min). The main factors affecting the heating rate are furnace temperature, steel chemical composition, furnace loading method, steel size, etc.

1) The higher the furnace temperature, the faster the heating rate of steel.

2) The chemical composition of steel determines the thermal conductivity of steel. The higher the carbon content, the worse the thermal conductivity; the higher the alloy content, the worse the thermal conductivity.

3) The denser the furnace is, the more uneven the heating degree of each steel material.

4) The larger the size of the steel, the greater the temperature difference between the inner and outer layers of the steel under the same heating rate. In order to prevent the metal from cracking during the heating process and the temperature difference between the inside and outside of the furnace is too large, the heating speed should be limited. Generally, in the case of ensuring that the steel does not appear overheating, overburning and cracking, the furnace loading temperature should be increased as much as possible. This not only improves the productivity, but also avoids the oxidation, decarburization and grain growth of the steel. Carbon steel, alloy structural steel billets and non-ferrous metal materials, even if the heating speed is fast, will not form large thermal stress or cause internal cracks, so the heating speed is not limited. For steel ingots, high-carbon steel, and high-alloy steel, due to the large cross-section size or low thermal conductivity, too fast heating speed will cause a large temperature difference between the inside and outside of the metal, forming internal cracks, so the heating speed must be slow, or use Two-stage and three-stage heating method.