Heat Treatment Process and Application of Ductile Iron Piston Castings

Abstract

The invention relates to a heat treatment process for ductile iron piston castings. a. Put the ductile iron piston castings at room temperature into an electric furnace, heat them to 620-680°C, and keep them warm for 1-2 hours; b. Reheat them to 920±10°C and keep them warm. 2±0.5h; c. Cool down to 850-880°C and keep warm for 1±0.1h; d. Put it into the water solvent cooling medium immediately after being out of the furnace, and control the rapid cooling time at 10-20s to cool the ductile iron piston casting to 600- 750°C, take it out of the water solvent cooling medium; e, place the ductile iron piston casting in the air, and cool it naturally; g, temper the ductile iron piston casting after air cooling to room temperature, and obtain the matrix structure of the ductile iron piston Ductile iron piston castings with pearlite content above 90%. The invention is a heat treatment process for ductile iron castings with complex structure, uneven wall thickness and extremely high pearlite content.

Description

technical field [0001] The invention relates to a heat treatment process of a ductile iron piston casting and an application thereof, and belongs to the technical field of heat treatment process of a ductile iron casting. Background technique [0002] Pearlitic ductile iron has high strength, wear resistance, and low toughness, and is suitable for parts with high strength requirements, and is widely used in vehicle structural parts. [0003] The pearlite strengthening of conventional ductile iron usually adopts the normalizing process, that is, after the austenitization of the ductile iron, after a period of heat preservation, it is immediately air-cooled, air-cooled or fog-cooled after being released from the furnace, so that the matrix is ​​transformed into a pearlite structure. , to achieve the effect of improving hardness, strength and wear resistance. The normalizing heating temperature of graphite cast iron is generally controlled at 800-900°C. Excessively high normal...

AI Technical Summary

Problems solved by technology

[0008] 1. After heat treatment, the matrix structure of the ductile iron piston casting is not pearlite structure, and its structure and performance are far from the requirements. Due to the insufficient pearlite content of the piston casting, the surface of the ring groove of the piston casting has high frequency after semi-finishing. The hardness of induction hardening is generally lower than the specified standard, which reduces the wear resistance of the piston

[0009] 2. Due to the complex structure and uneven wall thickness of ductile iron piston castings, the tendency of deformation and cracking during quenching is very large, and quenching cracks are easily produced, resulting in a decline in the pass rate of ductile iron piston castings

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