Control method for preventing nitrogen increasing in LF refining treatment

Abstract

The invention discloses a control method for preventing nitrogen increasing in LF refining treatment. The control method comprises: before refining, performing submerged-arc heating via replenishing slag materials; in an initial stage of refining, producing white slag via ladle bottom high-flow-argon blowing, and adopting a low-current and low-voltage power supply; in an intermediate stage of refining, adopting a high-current and high-voltage power supply, and reducing frequency of heating and frequency of opening a furnace door for temperature measurement and sampling in order to improve the temperature raising efficiency; and in a later stage of refining, adopting ladle bottom small-flow-argon blowing, and the low-current and low-voltage power supply. The control method adopts the ways above for preventing nitrogen increasing, so that nitrogen increasing of an LF during a working process is effectively prevented; the average amount of nitrogen increasing is controlled in a range of 3-5ppm; and the quality of molten steel is further improved.

Description

technical field [0001] The invention relates to an LF furnace refining process, in particular to a control method for preventing nitrogen increase in the LF furnace refining process. Background technique [0002] Nitrogen in steel is a harmful element for most steel products. High nitrogen content in steel can easily lead to aging and blue brittleness of steel; when nitrogen exceeds a certain content, it will also cause slab bubbles and loose center; in addition, nitrogen also reduces the toughness, plasticity and welding performance of steel. Since nitrogen is the main substance in the air, it is easily inhaled by molten steel during steelmaking and difficult to remove by conventional methods. Therefore, it is particularly important to prevent nitrogen increase in the various processes of steelmaking. [0003] The ladle refining furnace (hereinafter referred to as LF furnace) adopts the bottom blowing argon stirring process in the process of processing molten steel. In th...

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Problems solved by technology

[0005] 1) Situation of slag material: add appropriate amount of lime, appropriate amount of high alumina deoxidizer, the speed of slag is slow

[0006] 2) Power supply system: When the LF furnace is heated, high voltage is used, the arc is long, and the noise is large

[0007] 3) The atmosphere in the furnace cover is not considered, and the opening of the dust removal valve is random

[0012] 1. The thickness of the slag layer on the top of the molten steel is not enough to carry out effective submerged arc heating

[0013] 2. During the heating process of LF furnace, the choice of power supply system is unreasonable

[0014] 3. The flow control of ladle bottom blowing is not standardized, resulting in the exposure of molten steel to absorb nitrogen

[0015] 4. The heating time of molten steel is too long, the more nitrogen is added

[0016] 5. Improper control of the atmosphere in the LF furnace, resulting in nitrogen increase in molten steel

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