As-cast pearlite ductile iron material for crankshaft, and preparation method of the same

Abstract

The invention relates to an as-cast pearlite ductile iron material for crankshaft, and a preparation method of the same. The material is composed of the following elements by mass percent: C: 3.40-3.75%, Si: 2.25-2.60%, Mn: 0.15-0.35%, S: less than 0.015%, P: less than 0.04%, Cu: 0.9-1.1%, Sn: 0.01-0.03%, Mg: 0.03-0.05%, and the balance of Fe. The material is prepared by the steps of using Q10 cast iron, scrap returns and steel scrap as the raw materials for smelting, performing spheroidizing and ladle inoculation, performing metal-stream inoculation while casting, and then, cooling naturally. The obtained material is steady in texture; for the material, the impact value is not less than 40J / cm2, the strength of extension is not less than 850MPa, the yield strength is not less than 480MPa, the ductility is not less than 5.5%, the hardness is HB250-310, the rate of spheroidization is not less than 85% and the pearlite content is not less than 90%; the material can be used for manufacturing gasoline engine turbocharging high-effect crankshafts for cars.

Description

technical field [0001] The invention relates to an as-cast pearlitic nodular iron material for a crankshaft and a preparation method thereof, belonging to the field of casting materials. Background technique [0002] As-cast pearlite ductile iron material refers to the ductile iron material whose as-cast matrix is ​​mainly pearlite. Usually, the pearlite content is more than 80%, and the tensile strength is about 700-850MPa. It is widely used in automobile crankshafts. For pearlitic ductile iron materials, there is no impact toughness requirement in domestic and foreign standards. At present, the production of crankshafts with as-cast pearlitic ductile iron tensile strength up to 850MPa is mainly realized by high-carbon and low-silicon, alloying and sand-coated iron molds. [0003] The as-cast pearlitic ductile iron crankshaft produced by high carbon and low silicon, alloying and sand-coated iron mold is characterized by high strength and low toughness. The reason is that l...

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Problems solved by technology

[0003] The as-cast pearlitic ductile iron crankshaft produced by high carbon and low silicon, alloying and sand-coated iron mold is characterized by high strength and low toughness. The reason is that low silicon reduces graphite precipitation and carbon exists more in the form of compounds. ;Alloying and sand-covered iron molds increase the supercooling degree of molten iron after pouring, and the amount of pearlite is large, and the distance between cementite sheets is small, that is, the cementite sheets are dense, and the cementite is very hard and brittle , so the toughness is greatly reduced

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