Pistons and piston rings are located at the heart of th […]
Pistons and piston rings are located at the heart of the engine, and the quality of their work directly affects the performance of the engine. The pistons of modern engines are mostly made of aluminum alloy. Its main advantages are light weight and good thermal conductivity. The piston and the piston ring are a pair of friction. In order to optimize its working performance, in the selection of raw materials and coating materials for the working surface, the compatibility between the two should be considered first. For example, if the end face of the piston ring is chemically passivated, the piston should use AEB5 eutectic aluminum (5% Cu content) as the material, and the piston ring groove should be phosphated. With the continuous improvement of engine power and the continuous extension of piston working life, ordinary aluminum alloy pistons cannot meet the requirements, and many new materials with better performance are used in pistons. The performance of aluminum-based composite materials has reached the level of Ni-resist, the best material used, cast iron, and the quality of pistons and piston rings is greatly reduced after being made, and its high temperature strength and thermal fatigue resistance are significantly improved compared with ordinary aluminum alloy materials , And has a low coefficient of linear expansion. It can increase the service life of pistons, reduce fuel consumption and exhaust gas emissions, and increase engine power.
Ductile iron materials have been normalized to improve strength in the past. With the maturity of production technology, as-cast pearlitic ductile iron crankshafts have gradually replaced normalized ductile iron crankshafts. As the number of graphite balls increases and the matrix structure is all pearlite, high mechanical properties can be obtained in the as-cast state. The as-cast crankshaft does not need normalizing heat treatment, which not only simplifies the production process, reduces energy consumption and production costs, but also avoids the internal stress caused by human factors, thereby reducing the tendency of deformation of the crankshaft during surface hardening and strengthening treatment after cutting. Take the production of EQl092 automobile crankshaft as an example. As long as the pearlite content of the as-cast matrix is not less than 75%, the quenching hardness of the journal surface is higher than that of platinum HRC, and the deformation is less than 0.3mm. After quenching, the crankshaft deforms greatly and is unstable, with an average of 15ma and a maximum of 3.5mm.