Alloy ductile iron crankshaft and heat treatment process thereof

Abstract

The invention relates to an alloy ductile iron crankshaft and a heat treatment process thereof. The heat treatment process comprises the following steps: the carbon structural steel or the tool steel is taken as the raw material, carburant and ferrosilicon are added during the smelting process of an electric furnace in sequence, and the alloy ductile iron crankshaft comprises the following components (weight percentage): C accounts for 3.50-4.00, Si accounts for 1.6-2.5, Mn accounts for 0.3-0.9, P is less than 0.040, S is less than 0.03, Cr accounts for 0.03-0.07, Cu accounts for 0.2-0.5, Mg is less than 0.08, Ti is less than 0.02 and the balance is Fe. The austenization processing temperature is 840-920 DEG C, the heat preservation is carried out for 0.5-2.5 h, the three-phase region processing is performed at the temperature of 770-850 DEG C along with furnace cooling, and the time for the three-phase region processing is 1-3 h. The invention improves the nodularizing effect and the inoculation quality of the crankshaft, has low Ti content and effectively inhibits the influence of the heredity of the molten iron to the quality of the casting part; the heat treatment is added in the three-phase region processing; and the tensile strength of the alloy ductile iron crankshaft is equal to or more than 900 MPa, the yield strength is equal to or more than 500 MPa, the elongation rate is larger than or equal to 5 percent, and the alloy ductile iron crankshaft has excellent comprehensive properties and can be manufactured into high-trademark QT900-5 crankshaft.

Description

Technical field [0001] The invention relates to the field of metallurgy and cast iron alloys, in particular to an alloy ductile iron crankshaft and its heat treatment process. Background technique [0002] We know that the crankshaft is one of the important machine parts. Its structure and force are complex, the work load is large, and the requirements for internal metallurgical materials, casting quality and forming accuracy are very high. Compared with steel shafts, traditional ductile iron crankshafts have the characteristics of easy cutting and good lubrication. The best material for normalized crankshafts is ductile iron 900-2. The tensile strength of the crankshaft body is ≥900Mpa, and the elongation is ≥2%. , The overall hardness is low, below HB300. The metallographic structure of the austempered ductile iron ADI material is austempered ductile iron, the tensile strength is ≥900Mpa, the elongation is ≥2%, and the overall hardness is above HB300, which makes ADI crankshaft...

AI Technical Summary

Problems solved by technology

The metallographic structure of the austempered ductile iron ADI material is Aobei ductile iron, the tensile strength is ≥900Mpa, the elongation is ≥2%, and the overall hardness is above HB300, which makes it difficult to process the ADI crankshaft and the fillet rolling effect is not very ideal. And the cost is relatively high, so the process of producing high-grade nodular iron crankshafts by austempering has been difficult to promote in my country

Chinese patent 03111574.8 discloses an ultra-high-strength rare metal alloy ductile iron crankshaft, which is mainly to solve the problems of low tensile strength and low elongation of the existing crankshaft

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