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A method for modifying carbides of martensitic valve steel

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

Active Publication Date: 2022-06-21
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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  • A method for modifying carbides of martensitic valve steel
  • A method for modifying carbides of martensitic valve steel
  • A method for modifying carbides of martensitic valve steel

Examples

Experimental program
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Embodiment 1

[0060] The present embodiment provides a method for modifying carbides of martensitic gas valve steel, which includes the following steps: sequentially electric furnace smelting, AOD furnace smelting, LF furnace refining, continuous casting, rolling and Pickling to obtain the modified martensitic gas valve steel; among them, in the final stage of molten steel refining in the LF furnace, after the molten steel temperature and composition are adjusted in place, the addition process of magnesium-containing cored wire is carried out, and in the 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 at the end of the AOD furnace smelting is less than 100ppm.

[0061] At the end of LF furnace refining, before the magnesium-containing cored wire is fed, the basicity of the steel slag layer is 4.5. At the same time, the white slag production t...

Embodiment 2

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

[0067] At the end of the smelting stage of the LF furnace, the basicity of the slag layer was 4.5, and the time for making white slag was 30 minutes. At the end of the smelting stage of the LF furnace, the oxygen activity of the molten steel during tapping was 4.5ppm.

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

Embodiment 3

[0070] The method for modifying the carbides of martensitic gas valve steel in this embodiment includes the following steps: sequentially smelting the martensitic gas valve steel raw materials by electric furnace, AOD furnace smelting, LF furnace refining, continuous casting, rolling and Pickling to obtain the modified martensitic valve steel; the difference between this implementation and Example 1 is:

[0071] At the end of the LF furnace refining, the basicity of the slag layer is 3. When the steel is tapped at the end of the LF refining, the oxygen activity of the 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 high oxygen activity during tapping, and the average size of carbides in the produced heat-resistant steel is 15-35 μm.

[0073] It can be seen from Example 2 and Example 3 that the higher the basicity of the slag in the final stage of LF furna...

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Abstract

The invention discloses a method for modifying carbides of martensitic gas valve steel. The method comprises the following steps: the raw material of martensitic gas valve steel is smelted in electric furnace, smelted in AOD furnace, refined in LF furnace, continuous casting, Rolling and pickling to obtain modified martensitic gas valve steel; wherein, the magnesium-containing cored wire is fed into the LF furnace at the end of refining, and the molten steel slag layer is maintained before feeding the magnesium-containing cored wire The temperature is 3.0-5.0, and the white slag production time is greater than 25 minutes; the weight of the molten steel slag layer is not less than 3.5% of the molten steel weight, the steel temperature is controlled at 1467-1497°C, and the oxygen activity of the molten steel is 2.2-4.8ppm. In the martensitic gas valve steel prepared by the method for modifying the carbides of the martensitic gas valve steel, the average size of the carbides therein is reduced from greater than 50 μm to less than 20 μm, effectively improving the segregation situation, and making the carbide size Has been greatly refined, segregation has been greatly improved.

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 gas valve steel. Background technique [0002] Valve steel is a kind of heat-resistant steel used to manufacture key components of gasoline and diesel engines. Its working conditions are harsh, and it is subject to frequent mechanical stress in high temperature, high pressure and corrosive environment, and needs to serve in high temperature, generally above 600 ℃, with durable strength, good high temperature oxidation resistance and good corrosion resistance. The steel grades are very demanding on the purity of the material. Heat-resistant steel should have two properties, namely high temperature chemical stability and high temperature strength. Heat-resistant steels are usually divided into thermally stable steels with excellent oxidation resistance or high temperature medium corrosion resistance at high temperat...

Claims

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Application Information

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Patent Type & Authority Patents(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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