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Method for modifying martensite gas valve steel carbide

A martensitic and valve steel technology, applied in the field of modified martensitic valve steel carbides, can solve the problems of reducing structure and hardness uniformity, increasing deformation and cracking tendency, deteriorating mechanical properties, etc., and achieving segregation improvement , improve quality and increase yield

Active Publication Date: 2021-07-09
上大新材料(泰州)研究院有限公司 +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These carbide defects increase the deformation and cracking tendency of the billet during quenching, reduce the uniformity of structure and hardness after final heat treatment, and deteriorate the mechanical properties, etc.
[0006] The martensitic valve steel produced in the existing preparation process often has coarse carbides with a size of more than 50 μm, and the maximum size reaches 100 μm, such as figure 1 As shown, seriously affect the properties of steel

Method used

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  • Method for modifying martensite gas valve steel carbide
  • Method for modifying martensite gas valve steel carbide
  • Method for modifying martensite gas valve steel carbide

Examples

Experimental program
Comparison scheme
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Embodiment 1

[0060] This embodiment provides a method for modifying carbides of martensitic gas valve steel, which includes the following steps: sequentially smelting the raw material of martensitic gas valve steel in electric furnace, smelting in AOD furnace, refining in LF furnace, continuous casting, rolling and pickling to obtain modified martensitic gas valve steel; among them, at the end of LF furnace molten steel refining, when the molten steel temperature and composition are adjusted in place, the addition process of magnesium-containing cored wire is carried out. During electric furnace smelting, The oxygen content of the molten steel is reduced to below 300ppm; when the AOD furnace is smelting, the basicity of the steel slag is greater than 5, and the active oxygen is less than 100ppm at the end of the AOD furnace smelting.

[0061] At the end of LF furnace refining, before feeding the magnesium-containing cored wire, the alkalinity of the slag layer is 4.5. At the same time, the ...

Embodiment 2

[0066] The method for modifying carbides of martensitic gas valve steel in this embodiment comprises the following steps: sequentially smelting the raw material of martensitic gas valve steel in electric furnace, smelting in AOD furnace, refining in LF furnace, continuous casting, rolling and Pickling to obtain modified martensitic valve steel. The difference between this implementation and embodiment 1 is:

[0067] At the end of LF furnace smelting, the basicity of the slag layer is 4.5. At the same time, the white slag production time is 30 minutes. At the same time, at the end of LF furnace smelting, the oxygen activity of the molten steel when tapping is 4.5ppm.

[0068] In this example, the oxygen activity of molten steel at the end of LF refining is higher than that of Example 1, and most of the carbides in the produced heat-resistant steel are distributed in the range of 12-30 μm.

Embodiment 3

[0070] The method for modifying carbides of martensitic gas valve steel in this embodiment comprises the following steps: sequentially smelting the raw material of martensitic gas valve steel in electric furnace, smelting in AOD furnace, refining in LF furnace, continuous casting, rolling and Pickling, obtains the improved martensitic valve steel; The difference between this implementation and embodiment 1 is:

[0071] At the end of LF furnace refining, the basicity of the slag layer is 3, and when the steel is tapped at the end of LF refining, the oxygen activity of molten steel is 5.5ppm.

[0072] In this example, the basicity of the slag layer during the refining period of the LF furnace is lower than that of Example 1, resulting in higher oxygen activity during tapping, and the average size of carbides in the produced heat-resistant steel is 15-35 μm.

[0073] From Examples 2 and 3, it can be seen that the higher the basicity of slag in the final stage of LF furnace refini...

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Abstract

The invention discloses a method for modifying martensite gas valve steel carbide. The method comprises the following step of sequentially performing electric furnace smelting, AOD furnace smelting, LF refining, continuously casting, rolling and pickling on martensite gas valve steel raw materials to obtain modified martensite gas valve steel, wherein in the final stage of LF refining, a magnesium-containing core-spun yarn is fed, before the magnesium-containing core-spun yarn is fed, the alkalinity of a molten steel slag layer is kept to be 3.0-5.0, the white slag making time is longer than 25 min, the weight of a slag layer of molten steel is not lower than 3.5% of the weight of the molten steel, the steel temperature is controlled to be 1467-1497 DEG C, and the oxygen activity of the molten steel is 2.2-4.8 ppm. According to the martensitic gas valve steel prepared through the method for modifying the martensite gas valve steel carbide, the average size of the carbide is reduced to 20 micrometers or below from over 50 micrometers, the segregation condition is effectively relieved, the size of the carbide is greatly refined, and segregation is greatly relieved.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for modifying carbides of martensitic valve steel. Background technique [0002] Valve steel is a kind of heat-resistant steel used to manufacture gas valves, key components of gasoline and diesel engines. Its working conditions are harsh, and it bears frequent mechanical stress in high temperature, high pressure, and corrosive environments. It needs to serve in high temperature environments, generally above 600°C. It has durable strength, good high temperature oxidation resistance, and good corrosion resistance. The steel grades have very high requirements on the purity of the material. Heat-resistant steel should have two properties, namely high temperature chemical stability and high temperature strength. Heat-resistant steel is usually divided into heat-stable steel with excellent oxidation resistance or high-temperature medium corrosion resistanc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C7/072C21C5/52C21C7/00
CPCC21C7/072C21C7/0056C21C5/52Y02P10/20
Inventor 付建勋曹晨巍
Owner 上大新材料(泰州)研究院有限公司
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