Smelting method for reducing nitrogen increase of molten steel in converter process

A smelting method and converter technology, applied in the field of iron and steel metallurgy, can solve the problems of steel toughness, plasticity, deep drawing, hot working and welding performance degradation, intergranular corrosion, slab cracking and other problems, and achieve novel methods and reduce molten steel. The effect of nitrogen absorption and reduction of contact frequency

Pending Publication Date: 2022-06-17
WUHAN IRON & STEEL GRP ECHENG IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] Nitrogen is a harmful element for most steel types. High nitrogen content is the key factor for a series of problems caused by purity, fluidity, slab surface quality and performance fluctuations, which can easily cause slab cracking and intergranular corrosion. In addition, the precipitation of steel nitrides will lead to aging and blue embrittlement, resulting in the decline of toughness, plasticity, deep drawing, hot working and welding of steel.

Method used

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  • Smelting method for reducing nitrogen increase of molten steel in converter process
  • Smelting method for reducing nitrogen increase of molten steel in converter process

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Embodiment 1

[0022] In this embodiment, the smelting of high-strength steel Q960D is taken as an example to explain the technical solution of the present invention in detail. In this embodiment, W[N] of molten steel is required to be less than or equal to 40×10 -4 %. The specific implementation process is as follows:

[0023] (1) Loading system: molten iron + scrap steel is used for smelting, of which the proportion of molten iron is 82% and the proportion of scrap steel is 18%; it is not allowed to use molten molten steel for smelting;

[0024] (2) Scrap quality: the source of scrap is not limited, and w[N] in scrap is 100×10 -4 %; the length × width × thickness of the scrap steel is 1.5m × 1.5m × 0.3m, and it is completely dissolved in the early stage of smelting;

[0025] (3) Requirements for argon blowing at the bottom of the converter: in the early stage of smelting, due to the violent reaction of C-O in the molten pool, the molten pool has good nitrogen removal capacity. Therefore...

Embodiment 2

[0032] In this embodiment, the smelting of high-strength steel Q960D is taken as an example to explain the technical solution of the present invention in detail. In this embodiment, W[N] of molten steel is required to be less than or equal to 40×10 -4 %. The specific implementation process is as follows:

[0033] (1) Loading system: molten iron + scrap steel is used for smelting, of which the proportion of molten iron is 83% and the proportion of scrap steel is 17%; it is not allowed to use molten molten steel for smelting;

[0034] (2) Scrap quality: select high-quality low-nitrogen scrap, and w[N] in the scrap is 90×10 -4 %; the length × width × thickness of the scrap steel is 1.4m × 1.4m × 0.28m, and it is completely dissolved in the early stage of smelting;

[0035] (3) Requirements for argon blowing at the bottom of the converter: in the early stage of smelting, due to the violent reaction of C-O in the molten pool, the molten pool has a good ability to remove nitrogen...

Embodiment 3

[0042] In this embodiment, the smelting of high-strength steel Q960D is taken as an example to explain the technical solution of the present invention in detail. In this embodiment, W[N] of molten steel is required to be less than or equal to 40×10 -4 %, the specific implementation process is as follows:

[0043] (1) Loading system: molten iron + scrap steel is used for smelting, of which the proportion of molten iron is 85% and the proportion of scrap steel is 15%; it is not allowed to use molten molten steel for smelting;

[0044] (2) Scrap quality: select high-quality low-nitrogen scrap, and w[N] in the scrap is 80×10 -4 %; the length × width × thickness of scrap steel is 1.3m × 1.3m × 0.25m, and it is completely dissolved in the early stage of smelting;

[0045] (3) Requirements for argon blowing at the bottom of the converter: in the early stage of smelting, due to the violent reaction of C-O in the molten pool, the molten pool has a good ability to remove nitrogen, so ...

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Abstract

The invention relates to a smelting method for reducing nitrogen increase in molten steel in a converter process. The smelting method comprises the following steps: limiting the nitrogen content and size of a waste steel raw material, changing bottom argon blowing in the early stage of a converter into nitrogen-argon combined blowing, increasing the gas flow, adopting bottom pure argon blowing in the middle and later stages of smelting, and increasing the bottom blowing gas flow; the smelting final temperature is smaller than or equal to 1630 DEG C, an oxygen lance is switched into argon, and argon is blown into the converter for 10-30 s; in the tapping process, 1.0 Kg/t to 1.2 Kg/t of calcium carbide is added to the bottom of a steel ladle in advance before tapping, 0.5 Kg/t to 1.0 Kg/t of calcium carbide is thrown in a steel flow impact area in the tapping process, CO generated by calcium carbide deoxidation is used for forming an air curtain, molten steel is isolated from air, and nitrogen absorption of the molten steel is reduced; the content of [O] in the molten steel in the tapping process is controlled to be (200-400) * 10 <-4 >%; bottom argon blowing of the steel ladle is started 20 seconds before tapping, air in the steel ladle is emptied, argon is stopped immediately after tapping is finished from 20 seconds before tapping to the end of tapping, and the steel ladle is covered for heat preservation to prevent molten steel from being exposed to increase nitrogen; the method is simple and clear in technological process, high in operability and easy to control.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy and converter smelting, in particular to a smelting method for reducing the nitrogen increase of molten steel in the converter process. Background technique [0002] Nitrogen is a harmful element for most steel grades. High nitrogen content is a key factor in a series of problems such as purity, fluidity, surface quality and performance fluctuations of the slab. It is easy to cause cracking of the slab and cause intergranular corrosion. In addition, the precipitation of steel nitrides will lead to aging and blue brittleness, resulting in a decline in the toughness, plasticity, deep drawing, hot working and welding of steel. Since nitrogen will deteriorate the performance of steel, most steel grades have strict control requirements for smelting w[N]. -4 %, w[N]≤50×10 in low nitrogen steel -4 %, or even lower. The partial pressure of nitrogen in the general atmosphere is 0.79Kg / ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C5/28C21C5/34C21C7/06C21C7/00
CPCC21C5/28C21C5/34C21C5/562C21C7/06C21C7/0068C21C7/0075
Inventor 汪晛夏金魁方建红金海兵黄道昌
Owner WUHAN IRON & STEEL GRP ECHENG IRON & STEEL CO LTD
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