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Method for increasing nitrogen content in vanadium-containing steel bar

A technology of nitrogen content and steel bars, applied in the field of steelmaking, can solve the problems of large fluctuations in nitrogen content, large amount of deoxidizer added, high production cost, etc., and achieve the effect of reducing the amount of alloy added, improving steel quality, and improving steel performance

Active Publication Date: 2015-06-03
HEBEI IRON AND STEEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that it is required to add a deoxidizer during the tapping process to make the oxygen activity of molten steel in the ladle reach below 10ppm. The amount of deoxidizer added is relatively large, and the production cost is high. It is only suitable for the production of nitrogen-containing steel that requires lower oxygen content. At the same time, the nitrogen content in the steel is controlled between 100-230ppm, and the nitrogen content fluctuates greatly

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  • Method for increasing nitrogen content in vanadium-containing steel bar
  • Method for increasing nitrogen content in vanadium-containing steel bar
  • Method for increasing nitrogen content in vanadium-containing steel bar

Examples

Experimental program
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Effect test

Embodiment 1

[0024] The nitrogen blowing flow at the bottom of the ladle during the converter tapping process is 0.5m 3 / min, the tapping temperature is 1680℃, the amount of vanadium slag added is 456kg, the oxygen activity of the molten steel is 28ppm, and the nitrogen content of the molten steel is 83.0ppm on the platform behind the furnace.

[0025] During the refining process of the LF furnace, according to the vanadium content of the molten steel in the early stage of refining, iron vanadium nitride is added to adjust the vanadium in the molten steel to the requirements of the steel grade. 3 / min, the heating time is 12min, the nitrogen blowing flow at the bottom of the ladle is 0.6m when the molten steel is stirred 3 / min, the refining time is 23min, and finally a molten steel with a nitrogen content of 179.2ppm is obtained, and the final molten steel composition is shown in Table 1.

[0026] Table 1 Example 1 Composition of molten steel (wt %)

[0027]

Embodiment 2

[0029] The flow rate of nitrogen blowing at the bottom of the ladle in the converter tapping process is 0.6m 3 / min, the tapping temperature is 1649℃, the amount of vanadium slag added is 430kg, the oxygen activity of the liquid steel is 23.3ppm, and the nitrogen content of the liquid steel is 80.6ppm on the platform behind the furnace.

[0030] During the refining process of the LF furnace, according to the vanadium content of the molten steel in the early stage of refining, iron vanadium nitride is added to adjust the vanadium in the molten steel to the requirements of the steel grade. 3 / min, the heating time is 13min, the nitrogen blowing flow rate at the bottom of the ladle is 0.5m when the molten steel is stirred 3 / min, the refining time is 29min, and finally the molten steel with a nitrogen content of 158.1ppm is obtained, and the final molten steel composition is shown in Table 2.

[0031] Table 2 Example 2 Composition of molten steel (wt %)

[0032]

Embodiment 3

[0034] The nitrogen blowing flow rate at the bottom of the ladle during the converter tapping process is 0.65m 3 / min, aluminum, manganese, calcium, iron is added for deoxidation, the tapping temperature is 1679°C, the amount of vanadium slag added is 414kg, the oxygen activity of liquid steel after deoxidation is 28ppm, and the nitrogen content of liquid steel is 90.0ppm on the platform behind the furnace.

[0035] During the refining process of the LF furnace, according to the vanadium content of the molten steel in the early stage of refining, iron vanadium nitride is added to adjust the vanadium in the molten steel to the steel grade requirements. When the molten steel is heated, the nitrogen flow rate at the bottom of the ladle is 0.21 m 3 / min, the heating time is 9min, the nitrogen blowing flow at the bottom of the ladle is 0.6m when the molten steel is stirred 3 / min, the refining time is 25min, and finally molten steel with a nitrogen content of 198.75ppm is obtained. The ...

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Abstract

The invention discloses a method for increasing the nitrogen content in a vanadium-containing steel bar. The method comprises the following steps: performing ladle bottom nitrogen blowing stirring in the converter tapping process, adding a deoxidant in the steel ladle in the tapping process to control the oxygen activity of the molten steel to below 30 ppm, and adding the converter vanadium-containing slag to perform vanadium alloying so that the nitrogen content of the molten steel is 70-90 ppm before LF refining; in the LF converter refining process, adding ferrovanadium nitride to adjust the vanadium content in the molten steel, simultaneously stirring the molten steel by adopting the ladle bottom nitrogen blowing to substitute the bottom argon blowing to finally control the nitrogen content in the molten steel to 130-220 ppm. The nitrogen content is increased in the converter tapping-LF refining process so that the nitrogen content in the steel is controlled to 130-220 ppm; the vanadium alloying is performed by the converter vanadium-containing slag so that separation out of vanadium nitride from the steel is promoted. The steel performance is obviously increased, the alloy adding amount is reduced and simultaneously the production cost of the vanadium-containing steel bar is reduced.

Description

Technical field [0001] The invention relates to the technical field of steelmaking, in particular to a method for increasing the nitrogen content in vanadium-containing steel bars. Background technique [0002] Nitrogen is regarded as a harmful element in most steel grades. The presence of nitrogen in steel reduces the toughness and plasticity of steel, causing steel to produce strain aging, aging precipitation hardening or aging brittleness, resulting in blue brittleness and cold brittleness of steel. It has a significant impact on the mechanical properties of steel. But for vanadium-containing steel bars, nitrogen has a strong affinity with vanadium. Vanadium not only forms VN to inhibit the adverse effects of nitrogen, but also uses nitrogen to optimize the precipitation reaction. Increasing the nitrogen content in vanadium-containing steel can increase the supersaturation of ferrite and promote faster nucleation of V (C, N) particles, giving full play to the effects of grain...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C7/076C21C7/00C21C7/072
CPCY02P10/20
Inventor 白瑞国张兴利国富兴韩春良靳刚强张俊粉
Owner HEBEI IRON AND STEEL
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