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Method for controlling low-melting-point inclusion in high-strength low-alloy steel

A technology for high-strength low-alloy and low-alloy steel, which is applied in the field of steelmaking and refining, and can solve the problems of reduced HIC resistance, impact on service performance, and low high strength.

Inactive Publication Date: 2014-12-17
UNIV OF SCI & TECH BEIJING
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  • Description
  • Claims
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Problems solved by technology

[0005] These calcium aluminates with low melting point will also be extended into long strips in the subsequent rolling, resulting in reduced ductility and HIC resistance of high-strength low-alloy steel sheets, seriously affecting their performance

Method used

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  • Method for controlling low-melting-point inclusion in high-strength low-alloy steel
  • Method for controlling low-melting-point inclusion in high-strength low-alloy steel

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specific Embodiment 1

[0033] Step 1: Tap steel from a 210-ton oxygen top-bottom combined blowing converter to the ladle. During the tapping process, add 1100kg of aluminum and iron, of which the aluminum content in the aluminum-iron alloy is 40wt%, 900kg of lime, and 240kg of fluorite. It is completed at 1 / 4; the aluminum content in the molten steel is 0.04wt% after tapping.

[0034] Step 2. The basicity of slag in the LF refining process (i.e. CaO / SiO 2 Ratio) is 3.5-5; the composition of slag at the end of slagging (taking the average value of eight heats in this embodiment) is: CaO: 54.79wt%; SiO 2 : 12.31wt%; Al 2 o 3 : 21.37wt%; MgO: 7.82wt%; T.Fe+MnO: 0.52wt%.

[0035] Step 3: After the slagging is completed, carry out desulfurization by blowing Ar gas at the bottom of the ladle with strong agitation, the flow rate of Ar is 1200 Nl / min, and the time of bottom blowing is 15 minutes. At the end of LF refining, the sulfur content of molten steel in eight heats was between 0.0006% and 0.0018%. ...

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Abstract

The invention provides a method for controlling a low-melting-point inclusion in high-strength low-alloy steel, which comprises the following steps: 1, tapping into a ladle, and adding additives into molten steel in the ladle after the start of tapping, wherein the additives include an iron alloy, aluminum deoxidizer, slow release deoxidizer and lime; 2, performing LF (ladle furnace) refinement in the ladle, wherein the basicity range of slag in the refinement process is 3-6; the refining slag subjected to LF slagging comprises the following components in percentage by mass: 50-65% of CaO, 6-12% of MgO, 13-26% of Al2O3, 9-19% of SiO2 and less than 0.5% of (FeO+MnO); 3, after slagging, blowing Ar gas from the bottom of the ladle, and desulfurizing while strongly stirring; and 4, in the strongly stirring process and the subsequent process, reacting the slag, the molten steel and an inclusion. The invention has the following advantages: favorable deoxidization and desulfurization effect is achieved, and simultaneously, the composition of the non-metallic inclusion in the steel is controlled to be in a high-melting-point region of a CaO-MgO-Al2O3(-SiO2) phase diagram, so that the inclusion is less prone to polymerization, and less deformation is caused in the subsequent rolling process, thereby achieving the purpose of controlling the large strip-shaped inclusion in a high-strength low-alloy steel plate.

Description

technical field [0001] The invention belongs to the technical field of steelmaking and refining, and in particular provides a method for controlling low-melting-point inclusions in high-strength low-alloy steel. Background technique [0002] High-strength low-alloy steel (HSLA) is widely used in high-rise buildings, offshore platforms, long-span bridges, pipeline steel plates, etc., and has high requirements for strength, low-temperature impact toughness, and hydrogen-induced cracking (HIC) resistance. Non-metallic inclusions, especially long inclusions have a great influence on its performance. This is mainly because: (1) strip-shaped inclusions have a significant impact on the properties of the steel plate in the non-rolling direction, resulting in anisotropy of the steel; (2) HIC cracks are mostly formed at the strip (or string) inclusions, And this expansion will eventually lead to product failure. [0003] MnS inclusions are easily extended into long strips during rol...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21C7/076C21C7/06C21C7/064
CPCY02P10/20
Inventor 于会香王新华姜敏黄福祥王万军
Owner UNIV OF SCI & TECH BEIJING
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