Method for increasing hardness of large high-grade gray-cast-iron diesel engine body

A high-grade, gray cast iron technology, applied in the field of casting technology, can solve the problems of lower product qualification rate, lower body quality, body cracking, etc., and achieve the effect of improving body qualification rate, improving body quality, and reducing casting stress and brittleness

Inactive Publication Date: 2020-06-19
SHANNXI DIESEL ENGINE HEAVY IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

During the forming process of the gray cast iron body, through the control of the melting process parameters currently used, the as-cast state cannot meet the requirements of the hardness range of the body body. Only by controlling the process parameters such as the chemical composition of the body before the furnace, multi-stage inoculation, and boxing time, etc. Make the hardness of the body in the as-cast state reach the range of 140-160HB, and then reach the range of 180HB-240HB through normalizing treatment, but how to control the above process parameters is still a difficult problem. If the process parameters are not properly controlled, it is easy to cause the body to crack , reduce the quality of the machine body and reduce the qualified rate of products

Method used

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  • Method for increasing hardness of large high-grade gray-cast-iron diesel engine body

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Embodiment 1

[0025] Embodiment 1: The method for improving the hardness of a large-scale high-grade gray cast iron diesel engine body body includes the following steps;

[0026] Step 1: Ingredients: Determine the chemical composition of the furnace ingredients according to the principle of high carbon equivalent, high carbon and low silicon, wherein the weight percentage of each chemical component is: C: 3.0-3.5, Si: 1.5-2.5, Mn: 0.7 ~1.00, P: <0.1, S: <0.15, Sn: 0.060~0.080, the rest is Fe, and the carbon equivalent is in the range of 3.6~4.0;

[0027] Step 2: Smelting the raw materials configured in step 1, wherein, on the premise that the total amount of Si is guaranteed to be constant, add Si in two times. Volume reduced by 0.5%;

[0028] Step 3: Inoculation treatment: adopt the inoculation method of pouring into the front of the furnace, and add an inoculant during the process of pouring the molten iron into the ladle for inoculation treatment. The inoculant used in the front of the ...

Embodiment 2

[0039] Embodiment 2: This embodiment is based on Embodiment 1. In the above step six, for the large-scale high-grade gray cast iron diesel engine body, the air-cooled fan is used for cooling, and the specific fan uses two power 2.2 KW、18700m 3 An axial-flow fan with an air volume per hour and a speed of 1440 rpm. The fan can be placed in a position that can cover the body and ensure that the air around the body is unobstructed, simplifying the structure of the air-cooling process.

[0040] In the present invention, the machine body first obtains a certain range of body hardness in the cast state, and then obtains a higher body hardness in the normalizing state, thereby ensuring that the body of a large-scale high-grade gray cast iron diesel engine can meet the hardness requirements and avoid gray cast iron. Airframe heat treatment cracking risk and other quality issues, improve the quality of the body, improve the pass rate of the body.

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Abstract

The invention provides a method for increasing the hardness of a large high-grade gray-cast-iron diesel engine body. According to the casting process, under the condition of selecting a high carbon equivalent, high carbon and low silicon, and multi-stage enhanced inoculation treatment, the microscopic structure and performance of cast iron are improved through as-cast inoculation, the generation of undercooled graphite and free cementite is reduced, molten iron is promoted to be solidified according to stable-system co-crystallization, the casting stress and brittleness of gray cast iron are reduced, the body obtains a body hardness in a certain range under an as-cast condition, and then a high body hardness is obtained through a normalized state, so that the quality problems of heat treatment cracking risk and the like of the gray-cast-iron body can also be avoided on the premise of ensuring that the large high-grade gray-cast-iron diesel engine body achieves a hardness requirement, the quality of the body is improved, and the qualification rate of the body is increased.

Description

technical field [0001] The invention belongs to the technical field of casting technology, and in particular relates to a method for increasing the hardness of a large-scale high-grade gray cast iron diesel engine body. Background technique [0002] Large-scale high-grade gray cast iron EY26 body, weighing 9 tons, material is HT300, the tensile strength of the sample before the furnace is required to be 300-350Mpa, the hardness is <260HB, and the body hardness after heat treatment reaches 180HB-240HB. During the molding process of the gray cast iron body, the as-cast state cannot meet the requirements of the hardness range of the body body through the control of the melting process parameters currently used. Only by controlling the process parameters such as the chemical composition of the body before the furnace, multi-stage inoculation, and boxing time, Make the hardness of the body in the as-cast state reach the range of 140-160HB, and then reach the range of 180HB-240...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C33/08C22C37/10B22D1/00C21D1/18C21D9/00C21D11/00
CPCB22D1/00C21D1/18C21D9/0068C21D11/005C21D2211/009C22C33/08C22C37/10
Inventor 晁革新郭敏李飞
Owner SHANNXI DIESEL ENGINE HEAVY IND
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