Selection of heat treatment furnace for large gray iron casting

Heat treatment furnace is mainly divided into gas furnace, electric heating furnace and gas electric heating furnace.

1. Gas furnace

The gas furnace uses a burner to ignite natural gas or gas and introduce high-pressure air to ensure sufficient combustion and heat circulation in the furnace and stable temperature in the furnace. The gas furnace mainly heats the casting through heat convection and heat exchange, and the temperature rise of each part of the casting is relatively uniform.

2. Electric heating furnace

Electric heating furnace refers to the use of resistance wire to heat the inside of the electric furnace. Electric heating furnace mainly heats castings through thermal radiation. It has high thermal efficiency and accurate temperature control. It is suitable for castings with simple structure. However, for large and complex castings, it is easy to form temperature difference on the surface and inside, which is not conducive to stress elimination.

3. Gas electric heating furnace

The gas electric heating furnace uses gas for heating in the heating stage and electric heating for insulation in the insulation stage, which effectively solves the problems of low heating efficiency of pure gas, high temperature control cost and low temperature control accuracy, as well as the fact that pure electric heating is not suitable for large castings, poor high temperature performance and limited by power supply, but the equipment cost is high. Heating characteristics and thermal efficiency of gas furnace, electric furnace and gas electric heating furnace.

According to the characteristics of the enterprise, after selecting the type of furnace, the furnace temperature uniformity of the heat treatment furnace shall be tested periodically according to GB / t30824 – 2014 test method for uniformity of gas heat treatment furnace before heat treatment. The furnace temperature uniformity of large gas heat treatment furnace can be improved by improving the burner form, furnace loading mode, burner state and the layout position of temperature control thermocouple, The accuracy of furnace temperature uniformity detection is ensured by adjusting and correcting the error of the test system. Through reasonable design and daily monitoring of furnace temperature uniformity, large gas furnace can effectively ensure furnace temperature uniformity and meet the high quality requirements of large heat treatment parts.