Method for improving impact strength of large high-strength high-toughness nodular cast iron diesel engine body

Abstract

The invention belongs to the technical field of cast iron casting and heat treatment, and discloses a method for improving the impact strength of a large high-strength high-toughness nodular cast irondiesel engine body. The method comprises the following steps of determining stokehole chemical components according to the principles of high carbon equivalent, high carbon, low silicon, Mn and S control, P and Ti limitation, and addition of an additive Sb to eliminate distorted graphite; and conducting spheroidizing and inoculating again, primarily measuring the impact strength, performing low-temperature graphitization heat treatment, and measuring the impact strength again.ai According to the method, in the casting process, the principles of the high carbon equivalent, high carbon, low silicon, Mn and S control, P and Ti limitation, multi-stage inoculation and addition of the additive Sb to eliminate the distorted graphite is selected, generation of supercooled graphite and free cementite is reduced, and solidification of molten iron according to stable system eutectic is promoted; and meanwhile, pearlite is eliminated through low-temperature graphitization annealing, the ferrite content of the engine body structure is increased to 90% or above, and therefore the purpose of improving the impact strength of the engine body is achieved.

Description

technical field [0001] The invention belongs to the technical field of cast iron casting and heat treatment, in particular to a method for improving the impact strength of a large high-strength ductile iron diesel engine body. Background technique [0002] At present, a certain type of large-scale high-strength ductile iron diesel engine body is made of QT400-18A, the mechanical properties (attached casting sample) tensile strength ≥ 390 (MPa), yield strength ≥ 250 (MPa), elongation > 15%, cloth Hardness = 140-180 (HBS), impact strength: Kv average ≥ 14 joules, Kv individual ≥ 11 joules. Graphite form: Ⅴ~Ⅵ, size: 4~5. Substrate: ferrite ≥ 90%. In the prior art, through the control of melting process parameters, the as-cast state cannot meet the requirements of the impact strength range of the machine body, resulting in insufficient impact strength of the large high-strength ductile iron body body. [0003] Through the above analysis, the existing problems and defects o...

AI Technical Summary

Problems solved by technology

In the prior art, through the control of melting process parameters, the as-cast state cannot meet the requirements of the impact strength range of the machine body, resulting in insufficient impact strength of the large-scale high-strength ductile iron body body

[0003] Through the above analysis, the existing problems and defects of the existing technology are: the prior art cannot meet the requirements of the impact strength range of the machine body in the as-cast state through the control of the melting process parameters, resulting in insufficient impact strength of the large high-strength ductile iron body body

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