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China has the largest output of die forgings in the world. These die forgings mostly use hot die forging manufacturing. Auto die forgings output in China accounts for about 67% of total output of die forgings. In auto die forgings, hot die forgings still have high proportion. Hot die forgings have high cardinal number of proportion, so as to energy consumption. In recent years, the annual energy consumption of hot die forgings is above million tons of standard coal, causing billions of standard cubic of exhaust gas and dust. For this, green production of hot die forging is necessary. The followings are effective measures which can realize green production:

 

1. Choosing green materials

Preferentially choose continue casting direct rolling steel and non-tempered steel, which can save materials by 10-15% and it leaves out the energy consumption of reheating, reducing cost. Using forgings made of non-tempered steel can leave out energy consumption of reheating, quenching and high-temperature tempering. 

 

2. Reducing consumption of stub bar and waste

Due to high quality raw materials, raw materials have smooth fracture surface without rags. During baiting, end cropping is unnecessary. Residual materials can be reduced through supplying. Waste can also be decreased by using suit blanking.

 

3. Decreasing trimming

Metal can be distributed rationally through changing performing mold and increasing blanking technology or other technologies, making metal fulfill cavity of finishing die and reducing decreasing trimming. Utilization of materials is increased by 3-5%.

 

4. Closed-die forging

Closed-die forging can be carried out on hot die forging press, which can realize closed-die forging of rotator or other disc parts on hot die forging press. Closed-die forging can be used for manufacturing gear forgings. The utilization of materials is improved by 10-15%, decreasing consumption of raw materials and relevant heating energy consumption.

 

5. Reducing working allowance and technological accessorial block  

Through advanced mold manufacturing technology, scale-free heating for forging billet and improving top institution, working allowance of forgings and inclination of die forging can be reduced. Use hot extrusion to take place of punching which can save materials. Meanwhile, processing consumption of drilling process can be reduced.

 

6. Using waste heat after forging

Use waste heat after forging to quench in media and temper under appropriate temperature, instead of thermal refining. Remaining heat quenching after forging can improve hardenability of materials, having better temper resistance and adding adjusted room of heat treatment. It can save the processes of reheating and quenching of forgings. The technology also can be used for residual heat annealing and isothermal normalizing.

 

7. Using numerical simulation technology

Numerical simulation technology can take place of traditional technology and mold design method which is based on experience, formulas and data, highly improving technologies and technical level of mold design. The technology cannot only reduce development cycle of new products, but also improve quality of products, saving energy and materials, extending service life of mold.