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Inclusion control method of ultralow temperature steel

A control method and technology for inclusions, which are applied in the field of metallurgy to achieve the effects of prolonging service life, improving impact performance and improving performance qualification rate

Active Publication Date: 2015-08-19
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The above patents all improve various properties of steel through the control of inclusions, but do not involve the impact of inclusions in ultra-low temperature steel on the impact properties of steel and the control of inclusions

Method used

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  • Inclusion control method of ultralow temperature steel

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Embodiment Construction

[0019] This embodiment provides a method for controlling inclusions in steel for ultra-low temperature. Taking 9Ni steel for ultra-low temperature as an example, the main process steps are as follows:

[0020] (1) Converter smelting, using single slag smelting, the temperature at the end of the converter is controlled between 1620 and 1660 °C.

[0021] (2) Deoxidation is carried out after the converter furnace, and a deoxidizer is added to the ladle after the furnace. The deoxidizer uses aluminum blocks of 1.5-1.7kg / ton to create conditions for molten steel refining.

[0022] (3) LF furnace refining. Refining the molten steel in LF furnace, according to the temperature conditions, put the ladle into the LF furnace for heating treatment, the temperature is controlled at 1650°C, transport the ladle to the slag discharge position and lift it, put the steel ladle below it, and start refining for 10-15 minutes The slag-making process is completed within the temperature rise. By...

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Abstract

The invention relates to an inclusion control method of ultralow temperature steel, which comprises the steps of firstly performing powerful deoxidation by adopting aluminum blocks of 1.5-1.7kg / ton behind a furnace to create conditions for liquid steel refining; then performing LF furnace refining treatment on the liquid steel and finishing heating up slagging in 10-15 minutes after the refining is started, wherein the top slag alkalinity is controlled within 6-8 and the slag amount is controlled within 14-17kg / ton; the method also comprises a calcium treatment process, in which the feeding amount of calcium is controlled according to S content in the liquid steel, calcium aluminum ratio in the refined slag top slag and yield of Ca, and the calcium sulfur ratio in the liquid steel is controlled within 1.0-1.6, and the calcium aluminum ratio in the refined slag is controlled within 1.5-1.8. By optimizing a calcium treatment process, inclusion types generated by the liquid steel are controlled, enriched inclusions in the liquid steel in the prior art are converted to tiny dispersion, difference between a thermal expansion coefficient of the inclusions and a steel base body is reduced by improving the inclusion types, the influence of the inclusions on the low temperature impact performance of the steel is reduced, so that the impact performance of the ultralow temperature steel is effectively reduced, performance pass rate is improved and the service life is prolonged.

Description

technical field [0001] The invention belongs to the field of metallurgy and relates to a method for controlling inclusions in a steelmaking process, in particular to a method for controlling inclusions in ultra-low temperature steel. Background technique [0002] With the adjustment of the energy structure, the use of clean energy such as natural gas and methane is becoming more and more extensive. In order to facilitate transportation and storage, these gases are generally liquefied, and the main structural material of the tank body for transportation and storage is nickel-based ultra-low temperature steel plates represented by 9Ni and 5Ni. In order to ensure the safety of the steel plate, nickel-based steels require ultra-low temperature impact, such as 9Ni and 5Ni require low-temperature impact at -196°C and -125°C, respectively. Due to the lower temperature used in the impact test, there is a difference between the thermal expansion coefficient of the inclusions and...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C7/06
Inventor 王攀峰靳星谢章龙聂真来
Owner NANJING IRON & STEEL CO LTD
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