High-strength, high-elasticity modulus and low-stress gray cast iron and manufacturing method thereof

Abstract

The invention discloses high-strength, high-elasticity modulus and low-stress gray cast iron and a manufacturing method thereof; and under the conditions of improving the carbon equivalent and the silicon-carbon ratio, the gray cast iron with excellent comprehensive performances is obtained through optimizing the raw material ratio by combining with the alloying, the smelting improvement, the inoculation and the aging treatment process. The gray cast iron comprises the components of 3.15-3.25% of C, 1.80-2.00% of Si, 3.75-3.90% of CE, 0.70-1.00% of Mn, P not more than 0.07%, 0.06-0.10% of S, 0.50-0.70% of Cu, and 0.20-0.30% of Cr; and the gray cast iron has the structure and the performance as follows: the pearlite content is not lower than 95%; the length of A type graphite is 4-5 grade; the content of cementite and iron phosphide eutectic is lower than 0.5%; the tensile strength is not higher than 300 MPa; the elasticity modulus is not higher than 120 GPa; the hardness HB is 190-220; and the internal stress is not lower than 20 MPa. The gray cast iron solves the technical difficulty that a gray iron casting for a machine tool is difficult to synchronously achieve high strength, high elasticity modulus and low stress, and effectively reduces the deformation and the rupture of the casting caused by the release of residual stress along with the time.

Description

technical field [0001] The invention relates to gray cast iron, in particular to a high-strength, high-elastic-modulus, low-stress gray cast iron suitable for manufacturing machine tool castings, and also relates to a manufacturing method of the gray cast iron. Background technique [0002] With the continuous development of CNC machine tools towards high precision, powerful cutting, high-speed cutting, large-scale, thin-walled, etc., the material of machine tool castings is required to have high strength, high stiffness, low stress and high precision retention. At present, most of machine tool castings are gray cast iron. Practices at home and abroad have proved that gray cast iron with high carbon equivalent and high strength is the development direction of gray cast iron. It is an important way to achieve the comprehensive balance of these three aspects. [0003] According to the survey, most domestic machine tool casting manufacturers achieve high strength by greatly re...

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Problems solved by technology

[0004] In the existing gray cast iron production method, by adding an appropriate amount of Cu, Sn, Sb, Cr and other alloying elements to refine the eutectic group and strengthen the matrix to obtain gray cast iron with a tensile strength ≥ 300 MPa, but this production method has the following Problem: 1. It is difficult to achieve high strength and high elastic modulus at the same time. When the tensile strength is ≥300MPa, the elastic modulus of the casting is generally 100~115GPa, which is at a relatively low level, and almost The performance index of elastic modulus is not controlled; 2. The inoculation treatment method is relatively extensive, and the inoculant mostly uses 75# ferrosilicon, and only inoculates in the bag and floating silicon inoculates. The effect inspection is lacking, and the breeding decline is difficult to prevent; 3. The residual stress of the casting is not measured, and the residual stress is not used as a control index, and the residual stress of the casting varies greatly (50~250MPa); 4. No thermal aging treatment, or The process parameters such as annealing temperature, heating and cooling speed, and holding time during thermal aging are not carried out according to the specifications, resulting in the residual stress of the casting rising instead of falling, which seriously leads to deformation or even cracking of the casting

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