Why is the forging process currently irreplaceable?

The car and some of the drive shafts must be forged, mainly crankshaft components. Forging is a processing method in which a block and a bar-shaped steel material are struck to form. Forging by heating the forging billet to a temperature above the recrystallization temperature is called hot forging. Hot forging produces the forging blank close to the shape of the product while changing the mechanical properties of the forging. Crankshafts, camshafts, sprocket gears, etc., which are required to have high rigidity in automobile parts, are hot forgings. The automobile crankshaft is a shaft type component that converts the linear motion of the drive piston into a rotary engine. The crankshaft consists of a main shaft fixed to the engine, a piston connecting rod, a connecting rod pin, and a balance weight. According to the type of vehicle and the requirements of use, the crankshaft of the automobile has various forms such as in-line 3-cylinder, in-line 4-cylinder, in-line 6-cylinder, V-type 6-cylinder, and V-type 8-cylinder. The shape is very complicated.

In the past, automotive forged crankshaft materials were generally heat-treated materials of carbon steel and Cr-Mo steel (tempering treatment). After the 1970s, in order to reduce material costs, the development of non-quenched and tempered steel was promoted. Now, non-quenched and tempered steels such as carbon steel (high fatigue strength steel) and V-free carbon steel have become automotive forged crankshafts. Mainstream steel grades for materials.

Further, in order to change the fatigue strength of the crankshaft, after the crankshaft is machined, the dangerous parts such as the link pin of the crankshaft and the rounded corner of the crankshaft are subjected to high-frequency quenching, soft nitriding, rolling processing, or the like to change the strength of these portions.

When forging the automobile crankshaft, it is generally the case that the forging billet is heated to about 1200 ° C and then hot forged. In this way, a small forging device can be used to apply a small load for good precision forging. When manufacturing forged crankshafts, not only quality management of forging is required, but also strict quality control is required from the crankshaft material design, crankshaft shape design, steelmaking to forging system processes. Crankshaft or axle products processed with bars are prone to quality problems with forging and cracking.