As-cast high-strength nodular cast iron for crankshaft and preparation method of as-cast high-strength nodular cast iron

Abstract

The invention provides as-cast high-strength nodular cast iron for a crankshaft and a preparation method of the as-cast high-strength nodular cast iron. The as-cast high-strength nodular cast iron consists of the following elements by weight percent: more than or equal to 4.2 and less than or equal to 4.5 of CE, 3.5-3.9% of C, 1.8-2.2% of Si, less than or equal to 0.5% of Mn, less than or equal to0.03% of P, 0.005-0.02% of S, 0.4-0.8% of Cu, 0.002-0.01% of Sb and the balance of Fe and inevitable micro-elements. The as-cast high-strength nodular cast iron has the tensile strength of 800-850 Mpa, the ductility of more than or equal to 6% and the nodularity of 90%. A metallographic structure has the matrix of more than or equal to 90% of pearlite. Cementite and iron phosphide eutectic are less than or equal to 2%. The nodularity is 2-level or above. The sizes of graphite nodules are 5-8 levels. The tensile strength Rm is more than or equal to 800 MPa. The elongation is more than or equalto 6%. Such key parts as the crankshaft prepared by the preparation method are reliable in quality and superior in performance.

Description

technical field [0001] The invention belongs to the technical field of nodular cast iron materials, in particular to an as-cast high-strength nodular cast iron for crankshafts and a preparation method thereof. Background technique [0002] Since the early 1950s, ductile iron materials have gradually been popularized and applied due to their good comprehensive mechanical properties and process properties. They have the characteristics of high strength, impact resistance, and good toughness. The advantages of heat, crack resistance, vibration reduction, and low cost have replaced forged steel as the applied material for crankshafts. Especially since the 1970s, the application of ductile iron crankshafts has developed rapidly. However, with the continuous improvement of the power and speed of diesel engines, especially the wide application of turbocharging technology, the requirements for the crankshaft, the heart part of diesel engines, are getting higher and higher. The high-...

AI Technical Summary

Problems solved by technology

However, with the continuous improvement of the power and speed of diesel engines, especially the wide application of turbocharging technology, the requirements for the crankshaft, the heart part of diesel engines, are getting higher and higher. The high-grade ductile iron in the existing national standards is especially in the In terms of toughness, it has been unable to meet the performance requirements of key components of crankshafts for automobiles, tractors and other products. Therefore, high-grade, low-cost, and excellent performance have become the breakthrough direction for ductile iron crankshafts

[0003] At present, the grades covered by the national standard are QT600-3, QT700-2, QT800-2 and non-standard QT800-3 ductile iron with high strength and toughness. Although it has the characteristics of simple casting process and easy molding, the above grades prepared The tensile strength and elongation of the crankshaft are not high enough, it is difficult to meet the performance requirements of the crankshaft in terms of engine power, and it is not suitable for ductile iron with higher requirements for materials

[0004] Theoretically speaking, the tensile strength of QT800-6 as-cast crankshaft material is greater than 800MPa, and the elongation is greater than 6%. The production cost has been reduced by about 30%, and it is a new choice for engine crankshafts. However, in fact, there is currently no suitable process to produce QT800-6 as-cast crankshaft materials.

Images