Analysis of Some Basic Knowledge about Hot Forging Process

Forging can be divided into hot forging, warm forging, and cold forging according to the deformation temperature. Hot forging and warm forging require heating, while cold forging does not require heating. Heating, heating temperature and holding time, initial and final forging temperatures have a significant impact on the quality of forgings and cost reduction. At present, most industries use hot forgings, while warm and cold forgings are mostly used in mass production of parts such as automobiles and general machinery.

Why heat up?

Heating can reorganize and recrystallize the metal lattice, improve metal plasticity, reduce deformation resistance, facilitate metal deformation, and obtain good forged microstructure and mechanical properties. Heating makes a significant contribution to improving forging productivity, ensuring forging quality, and saving energy consumption. Direct forging without heating requires larger tonnage equipment and can easily cause lattice distortion of the material, generate internal stress, and lead to cracks or fractures in the forging.

What are the heating methods?

According to the different heat sources used, the commonly used heating methods in forging production are divided into two categories: flame heating and electric heating.

Flame heating:

Method: In a flame heating furnace, fuel (solid coal, coke, etc., liquid heavy oil, diesel, etc., or gas such as coal gas, natural gas, etc.) is burned to produce high-temperature gas (flame) containing a large amount of heat energy. The heat energy is transferred to the heating method of the blank through convection and radiation. When the heating temperature is below 600-700 ℃, the heating of the blank mainly relies on convective heat transfer; After the heating temperature reaches 700-800 ℃, the heating of the blank mainly relies on radiation heat transfer.

Advantages: The heating furnace has a simple structure, a wide range of fuel sources, low costs, and a wide range of adaptability to raw materials, making it easy to widely adopt;

Disadvantages: Poor working conditions, slow heating speed, difficult to control the atmosphere, temperature, and heating quality inside the furnace, and low thermal efficiency;

Application: The flame heating method is widely used for heating various large, medium, and small billets.

Classification of flame heating: intermittent loading, continuous loading

Electric heating

Method: The method of converting electrical energy into thermal energy to heat the blank.

Advantages: Fast heating speed, easy control of furnace temperature, less oxidation and decarbonization, good working conditions, easy implementation of mechanization and automation production, etc;

Disadvantages: There are certain limitations and requirements on the shape and size of the blank, the equipment structure is complex, the investment cost is relatively high, and the technical requirements for operation and use are high.

Application: Mainly used for heating high demand forging and precision forging, non-ferrous metal alloys, and some high-temperature alloys.

Classification of electric heating: According to heat transfer methods, it can be divided into resistance furnace heating, contact electric heating, salt bath furnace heating, and induction electric heating.

Heating method selection:

Determine based on various factors such as forging requirements, local energy situation, investment benefits, and environmental protection.

Large forgings are generally heated by flame; Small and medium-sized forgings can choose flame heating and electric heating; It is recommended to choose induction heating or other non oxidation heating methods for precision forging.

Heating precautions:

1. Under the conditions of permissible thermal conductivity and internal stress of metal materials, heat at a faster rate to the predetermined temperature, improve efficiency, and save energy;