阅读说明：本技术 一种减少铸坯表面氧化铁皮的冶炼方法 (Smelting method for reducing iron oxide scale on surface of casting blank ) 是由 常运合 吴伟勤 陈从俊 于 2020-07-10 设计创作，主要内容包括：本发明公开一种减少铸坯表面氧化铁皮的冶炼方法,通过调整优化连铸二冷工艺,将连铸二次冷却强度比水量平均值由0.60 L/Kg提高到0.70 L/Kg,控制铸机上部至下部各区冷却水量比例波动幅度,提高浇铸方向上铸坯冷却均匀性,通过减少喷嘴堵塞实现良好的二冷喷水雾化效果,铸坯表面氧化铁皮厚度明显减少,平均厚度由1.45mm降低到0.65mm,提高了连铸钢水回收率,经济效益显著。(The invention discloses a smelting method for reducing iron oxide scales on the surface of a casting blank, which improves the average value of the ratio of the secondary cooling intensity of continuous casting to the water amount from 0.60L/Kg to 0.70L/Kg by adjusting and optimizing a secondary cooling process of continuous casting, controls the fluctuation range of the ratio of the cooling water amount of each area from the upper part to the lower part of a casting machine, improves the cooling uniformity of the casting blank in the casting direction, realizes good secondary cooling water spray atomization effect by reducing nozzle blockage, obviously reduces the thickness of the iron oxide scales on the surface of the casting blank, reduces the average thickness from 1.45mm to 0.65mm, improves the recovery rate of continuous casting molten steel, and has obvious economic benefit.)

1. The smelting method for reducing the iron oxide scale on the surface of the casting blank is characterized by mainly reducing the average thickness of the iron oxide scale on the surface of the casting blank to 0.65mm by optimizing a production flow, optimizing a secondary cooling water pipeline, improving the secondary cooling strength water ratio and improving the secondary cooling uniformity, and specifically comprises the following steps:

(1) before production, the water leakage condition in the fan-shaped section of the casting machine is overhauled, and the secondary cooling nozzle is inspected and cleaned once every two days;

(2) the secondary cooling water pipeline is a stainless steel pipeline;

(3) the secondary cooling strength ratio water quantity average value is improved from 0.60L/Kg to 0.70L/Kg;

(4) and controlling the proportional fluctuation range of the cooling water quantity of each area from the upper part to the lower part of the casting machine, and reducing the local temperature return of the surface of the casting blank.

2. The method according to claim 1, wherein 10 zones are controlled from the upper part to the lower part of the casting machine, and the water content ratio of each zone is 13%: 13%: 15%: 13%: 12%: 11%: 10%: 8%: 3%: 2 percent.

3. The method of reducing scale on the surface of a casting slab of claim 1 wherein the slab surface temperature is controlled to between 8 ℃ and 30 ℃.

4. The smelting method for reducing iron oxide scale on the surface of a casting blank according to claim 1, wherein the temperature of secondary cooling cold water is controlled to be less than or equal to 30 ℃.

5. The smelting method for reducing the iron oxide scale on the surface of the casting blank according to claim 1, wherein the operation principle of 'small amount, large amount and black slag' is adopted, so that the molten steel on the liquid surface of the crystallizer is not exposed, the covering slag is uniformly spread on the liquid surface of the crystallizer, and the fluctuation of the liquid surface of the crystallizer is controlled.

6. The smelting method for reducing the iron oxide scale on the surface of the casting blank according to claim 1, wherein the components of the molten steel supplied to the continuous casting by the converter are strictly controlled, and the carbon content of the molten steel is increased to the maximum extent on the premise of ensuring the quality of the molten steel and reducing the cost during the smelting by the converter.

Technical Field

The invention relates to the technical field of metallurgy, in particular to a smelting method for reducing iron oxide scales on the surface of a casting blank.

Background

The iron scale on the surface of the continuous casting billet is generated by the reaction of iron elements on the surface of the continuous casting billet at high temperature and oxidizing gas oxygen and water in the environment. The iron oxide content on the surface of the continuous casting billet is too high, the molten steel yield is influenced, and unnecessary waste of the molten steel is caused. The influence factors of the generation amount of the iron scale on the surface of the casting blank and the key points of the process control comprise:

1. secondary water distribution process for continuous casting

The casting blank is uniformly cooled in the casting direction, the secondary cooling water spraying atomization effect is good, and the evaporated proportion is high so as to ensure the maximum cooling efficiency; the secondary cooling water which is not evaporated is prevented from staying on the casting blank for a long time; the casting blank is cooled as strongly as possible on the premise of not influencing the surface quality of the casting blank, and the generation of iron scale is reduced.

2. Surface temperature of casting blank

Stabilize low superheat degree, avoid high superheat degree and reduce the surface temperature of the casting blank.

According to related data, when the surface temperature of the casting blank is 700 ℃, iron oxide scales are not obvious, when the surface temperature of the casting blank is 900 ℃, the iron oxide scales on the surface of the casting blank are obviously increased, and when the casting blank is at 1000 ℃ for a long time, the iron oxide scales on the surface of the casting blank are rapidly increased, so that on the premise of not influencing the surface quality of the casting blank, the surface cooling strength of the casting blank is increased, the condition that the casting blank is at a high temperature for a long time is reduced, and the generation amount of the iron.

3. Secondary cooling water temperature

The secondary cooling water temperature is too high to achieve the normal cooling effect, the surface temperature of the casting blank is high, the surface temperature of the casting blank is too high, and the generation amount of iron scale is increased.

4. Composition of steel grade

Carbon, silicon, nickel, copper and sulfur promote the generation of iron scale, and manganese, aluminum and chromium can slow down the generation of iron scale.

5. Casting powder is rolled into

The liquid level of the crystallizer is ensured to be stable, and the covering slag is prevented from being involved. According to the characteristics of the steel grade, the casting powder with proper alkalinity, viscosity and melting speed is selected to prevent the casting powder from sinking, so that inclusions on the surface layer of the casting blank are formed, and the continuity of iron scales is cut off.

Disclosure of Invention

The invention aims to provide a smelting method, which optimizes and adjusts a continuous casting secondary cooling process and reduces the surface temperature of a casting blank, thereby controlling the contact oxidation of the surface of the casting blank and air and reducing the generation amount of iron oxide scales.

The invention specifically adopts the following technical scheme:

the smelting method for reducing the iron oxide scale on the surface of the casting blank is characterized by mainly reducing the average thickness of the iron oxide scale on the surface of the casting blank to 0.65mm by optimizing a production flow, optimizing a secondary cooling water pipeline, improving the secondary cooling strength water ratio and improving the secondary cooling uniformity, and specifically comprises the following steps:

(1) before production, the water leakage condition in the fan-shaped section of the casting machine is overhauled, and the secondary cooling nozzle is inspected and cleaned once every two days;

(2) the secondary cooling water pipeline is a stainless steel pipeline;

(3) the secondary cooling strength ratio water quantity average value is improved from 0.60L/Kg to 0.70L/Kg;

(4) and controlling the proportional fluctuation range of the cooling water quantity of each area from the upper part to the lower part of the casting machine, and reducing the local temperature return of the surface of the casting blank.

According to the invention, through research evaluation, the continuous casting secondary cooling process is adjusted and optimized, the average value of the continuous casting secondary cooling strength ratio water amount is improved to 0.70L/Kg from 0.60L/Kg, the proportional fluctuation range of the cooling water amount in each region from the upper part to the lower part of the casting machine is controlled, the casting blank cooling uniformity in the casting direction is improved, the good secondary cooling water spraying atomization effect is realized by reducing the nozzle blockage, the thickness of the iron scale on the surface of the casting blank is obviously reduced, the thickness of the iron scale on the surface of the casting blank is comparatively evaluated, the average thickness is reduced to 0.65mm from 1.45mm, the recovery rate of continuous casting molten steel is improved.

Detailed Description

The process of the present invention is described in further detail below with reference to specific examples.

Aiming at the problem of excessive thickness of the iron scale on the surface of the casting blank, the casting machine and the steel type are divided to carry out actual measurement and evaluation on the iron scale on the surface of the casting blank, and the technical scheme for reducing the thickness of the iron scale on the surface of the casting blank is as follows:

1) in the aspect of production operation, the water leakage condition in the fan-shaped section of the casting machine is overhauled before production. And the secondary cooling nozzles are checked and cleaned every two days, and the blocking quantity of the nozzles at different positions is recorded. The industrial water has more impurities, the nozzle is easy to block, the water spraying uniformity is influenced, and the regular cleaning is favorable for reducing the nozzle blockage. Meanwhile, a secondary cooling water pipeline is transformed, a stainless steel pipeline is used, the problem that a nozzle is blocked by water pipe corrosion is reduced, and the uniformity of casting blank surface cooling is improved.

2) Aiming at a slab caster, the size of a slab is 260mm (2070mm-2570mm), and after the average value of the secondary cooling strength ratio water quantity is improved from 0.60L/Kg to 0.70L/Kg through repeated research and comparative tests, the thickness of iron scale on the surface of the casting slab is obviously reduced, the secondary cooling strength is improved, the surface temperature of the casting slab is reduced, and the oxidation effect between the surface of the casting slab and air is reduced.

3) In the aspect of secondary cooling water quantity distribution, a cooling water quantity uniform reduction strategy is adopted from the upper part to the lower part of the casting machine, and the casting blank is ensured to be uniformly cooled from top to bottom by calculating the water flow density value of each cooling area. The water quantity proportion of each original zone (zone 1-zone 10) of the slab continuous casting machine is 13%: 13%: 15%: 12%: 8.5%: 13%: 9.5%: 12%: 2%: 2%, wherein, 5 district and 7 district's water content proportion compare with 4 districts and 6 districts, and the reduction range is great, easily causes the local excessive temperature return of casting blank and produces thermal stress, has increased the formation of casting blank surface iron scale simultaneously, and each district water content proportion is 13% after optimizing the adjustment: 13%: 15%: 13%: 12%: 11%: 10%: 8%: 3%: 2 percent.

4) The superheat degree is controlled to be 8-30 ℃, the superheat degree is stabilized to be low, the high superheat degree is avoided, and the surface temperature of the casting blank is reduced.

5) The temperature of the secondary cooling water is controlled to be less than or equal to 30 ℃, and the secondary cooling water is prevented from being overhigh and poor in cooling effect.

6) The operating principle of 'a small amount, more adding and black slag' is adopted, so that molten steel on the liquid surface of the crystallizer is not exposed, the protective slag is uniformly spread on the liquid surface of the crystallizer, and meanwhile, a self-adaptive control system for the liquid surface of the crystallizer is added aiming at the problem of large fluctuation of the liquid surface of the crystallizer, so that the liquid surface fluctuation is prevented from being too large.

7) The components of molten steel supplied to the continuous casting by the converter are strictly controlled, and during smelting by the converter, the carbon content of the molten steel is improved to the maximum extent on the premise of ensuring the quality of the molten steel and reducing the cost, so that the iron oxide scale content of a casting blank is reduced.