阅读说明：本技术 底吹电弧炉返回吹氧法冶炼特钢的方法 (Method for smelting special steel by bottom-blowing electric arc furnace returning oxygen blowing method ) 是由 付建辉 张健 刘庭耀 陈琦 于 2019-10-28 设计创作，主要内容包括：本发明公开了一种底吹电弧炉返回吹氧法冶炼特钢的方法,配料：采用本钢种及类似钢种的返回料作为原料；熔化期：对电弧炉通电将钢水加热,底吹气体,将废钢熔清；氧化期：当炉内钢液温度满足要求时,底吹气体并吹氧助熔至炉料全部熔化；还原期：加入还原剂,底吹气体,观察炉内气氛,当炉内脱氧良好、炉渣变白时,取样,调整成分温度；出钢,浇铸。本发明通过在返回吹氧冶炼工艺中底吹气体进行搅拌,可以改善电弧炉冶炼特钢的动力学条件,促使电弧炉内金属熔池的传热、传质速度加快,均匀金属熔液的温度和成分,降低渣中Cr<Sub>2</Sub>O<Sub>3</Sub>的含量,提高合金收得率,缩短冶炼特钢时间,降低生产成本,从而提高电弧炉冶炼特钢的能力。(The invention discloses a method for smelting special steel by a bottom-blowing electric arc furnace returning oxygen blowing method, which comprises the following steps: adopting the return materials of the steel grade and similar steel grades as raw materials; melting period: electrifying the electric arc furnace to heat the molten steel, blowing gas at the bottom, and melting down the scrap steel; and (3) oxidation period: when the temperature of the molten steel in the furnace meets the requirement, bottom blowing gas and blowing oxygen for fluxing until the furnace burden is completely melted; and (3) reduction period: adding a reducing agent, bottom blowing gas, observing the atmosphere in the furnace, sampling when the deoxidation in the furnace is good and the slag turns white, and adjusting the component temperature; tapping and casting. The invention can improve the dynamic condition of smelting special steel in the electric arc furnace by stirring the bottom blowing gas in the oxygen blowing smelting process, accelerate the heat transfer and mass transfer speed of the metal melting pool in the electric arc furnace, homogenize the temperature and components of the molten metal, and reduce the Cr in the slag 2 O 3 The content of the alloy improves the alloy yield, shortens the time for smelting special steel, reduces the production cost, thereby improving the smelting of an electric arc furnaceThe ability of special steel.)

1. The method for smelting special steel by returning to the oxygen blowing method in the bottom-blowing electric arc furnace is characterized by comprising the following steps of: the method comprises the following steps:

step one, batching:

adopting the return materials of the steel grade and similar steel grades as raw materials;

step two, a melting period:

electrifying the electric arc furnace to heat the molten steel, blowing gas at the bottom, and melting down the scrap steel;

step three, oxidation period:

when the temperature of the molten steel in the furnace meets the requirement, bottom blowing gas and blowing oxygen for fluxing until the furnace burden is completely melted;

step four, a reduction period:

adding a reducing agent, bottom blowing gas, observing the atmosphere in the furnace, sampling when the deoxidation in the furnace is good and the slag turns white, and adjusting the component temperature;

and fifthly, tapping and casting.

2. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: the adding amount of the return material in the first step is 45-60%.

3. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: in the second step, the gas adopted by bottom blowing is nitrogen, the flow rate of the bottom blowing nitrogen is controlled to be 15NL/min, and the molten steel is heated to 1580-1600 ℃.

4. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: controlling the oxygen blowing pressure to be 0.8-1.8 Mpa in the third step; argon is used as the gas for bottom blowing, and the flow rate of the argon for bottom blowing is controlled to be 20 NL/min.

5. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: in the fourth step, the addition amount of the reducing agent per ton of steel is 3.5-4.5 kg; the gas adopted by bottom blowing is argon, the early-stage control flow rate is 25-35 NL/min when the argon is blown from the bottom, and the control flow rate is 15NL/min when deoxidation in the furnace is good and slag becomes white.

6. The bottom-blowing electric arc furnace return oxygen blowing process for producing special steel according to claim 1 or 5, wherein: the reducing agent is one or two of ferrosilicon, aluminum blocks and fluorite.

7. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: in the third step, the oxygen blowing temperature is controlled to be 1600-1680 ℃.

8. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: the electric arc furnace is a 40 ton EBT furnace.

9. The method for smelting special steel by the bottom-blowing arc furnace return oxygen blowing method according to claim 1, characterized by comprising the following steps: the bottom blowing position is the center circle of the bottom of the electric arc furnace, double bottom blowing holes are adopted, and an included angle of 120 degrees is formed between the two bottom blowing holes.

Technical Field

The invention relates to the technical field of special steel smelting, in particular to a method for smelting special steel by a bottom-blowing electric arc furnace returning oxygen blowing method.

Background

At present, the world electric furnace steel accounts for about 34 percent of the steel yield, and the electric furnace steel making in China has great development in recent years. In the production field of smelting stainless steel, die steel and other special steel, an electric arc furnace is mainly used for smelting and producing nickel-chromium series special steel by an oxygen blowing method, and the purpose of the method is mainly to recover high-value metal elements such as chromium, nickel, molybdenum and the like in waste alloy steel so as to reduce the production cost.

However, in the electric arc furnace steelmaking, three electrodes distributed on a pole center circle are used for heating scrap steel and the surface of a molten pool, and the whole molten pool is heated by slag and metal, because the electric arc is heated from the top, the production technology of the current industry is that the surface temperature of the metal molten pool is high, the convection heat transfer is poor, the dynamic condition of the electric furnace smelting method is obviously insufficient, the internal temperature and the concentration of molten steel are not uniform enough, and particularly, Cr in slag is not uniform when smelting special steel₂O₃High content, poor molten steel fluidity, low metal yield, long smelting time and the like. The enterprise where the applicant is located mainly obtains the mother liquid through electric arc furnace smelting in the aspects of producing alloy steel, die steel, stainless steel and the like, but the smelting period is long, the temperature of molten steel components is uneven, and Cr in slag is₂O₃High content, low alloy yield and high production cost.

The invention discloses a process for smelting stainless steel by an electric arc furnace return oxygen blowing method, which is applied to the process for smelting stainless steel by the Chinese invention patent with the application number of 201410361792.5. Aiming at some problems in the production of stainless steel, the invention adopts the process technologies and operation means of high silicon (silicon is adjusted to 1.0-1.5%), high nickel (controlled to about 10%), high temperature and high pressure (1.5-1.8 MPa), double-pipe continuous oxygen blowing for 18-22 minutes, timely alloying and rapid reduction of the temperature of molten steel in a furnace, reasonable power supply and the like, so that the utilization rate of the high alloy steel return material during smelting reaches over 90%, the recovery rate of chromium in the whole smelting process reaches over 95%, and the oxygen blowing time during smelting is shortened by about 40 minutes. However, the patent only discloses the smelting process technology of the return oxygen blowing method, and does not disclose the specific process of bottom blowing.

The invention discloses a Chinese patent application with the application number of 201910241419.9, namely a method for smelting stainless steel by bottom blowing CO2, and relates to bottom blowing CO₂A method of smelting stainless steel comprising: (1) adding dephosphorized molten iron into converter, top-blowing O by oxygen gun₂Bottom blowing of bottom lance O₂And CO₂The mixed gas of (3); (2) adding furnace burden for alloying and slagging in the smelting process; (3) when the carbon content of the converter molten pool is 0.2-0.5%, the oxygen lance and the bottom lance stop blowing O₂The bottom lance continues to blow CO from the bottom₂(ii) a (4) And adding a reducing material into the molten pool for reduction, and transferring into a VOD furnace for refining when the components of the molten steel meet the requirements. Bottom blowing CO of the invention₂The method for smelting stainless steel uses CO as the inert gas blown from bottom of converter₂Not only reduces the smelting cost, but also avoids bottom blowing N₂The content of nitrogen element in the molten steel is increased, and the stability of the physical and chemical properties of the stainless steel is ensured. The invention is that the converter is added with dephosphorized molten iron, the oxygen lance blows oxygen from the top, blows oxygen from the bottom and CO₂The production route of the mixed gas of (2) is different from that of the present invention.

The above patent application also does not solve the problems of long smelting period, uneven temperature of molten steel components and Cr in slag in the production of special steel₂O₃High content, low alloy yield and the like.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method for smelting the special steel by the bottom-blowing electric arc furnace returning oxygen blowing method is provided, and the efficiency of smelting the special steel and the quality of finished products can be effectively improved.

In order to solve the technical problems, the invention adopts the technical scheme that: the method for smelting special steel by returning to the oxygen blowing method in the bottom-blowing electric arc furnace comprises the following steps:

step one, batching:

adopting the return materials of the steel grade and similar steel grades as raw materials;

step two, a melting period:

electrifying the electric arc furnace to heat the molten steel, blowing gas at the bottom, and melting down the scrap steel;

step three, oxidation period:

when the temperature of the molten steel in the furnace meets the requirement, bottom blowing gas and blowing oxygen for fluxing until the furnace burden is completely melted;

step four, a reduction period:

adding a reducing agent, bottom blowing gas, observing the atmosphere in the furnace, sampling when the deoxidation in the furnace is good and the slag turns white, and adjusting the component temperature;

and fifthly, tapping and casting.

Further, the method comprises the following steps: the adding amount of the return material in the first step is 45-60%.

Further, the method comprises the following steps: in the second step, the gas adopted by bottom blowing is nitrogen, the flow rate of the bottom blowing nitrogen is controlled to be 15NL/min, and the molten steel is heated to 1580-1600 ℃.

Further, the method comprises the following steps: controlling the oxygen blowing pressure to be 0.8-1.8 Mpa in the third step; argon is used as the gas for bottom blowing, and the flow rate of the argon for bottom blowing is controlled to be 20 NL/min.

Further, the method comprises the following steps: in the fourth step, the addition amount of the reducing agent per ton of steel is 3.5-4.5 kg; the gas adopted by bottom blowing is argon, the early-stage control flow rate is 25-35 NL/min when the argon is blown from the bottom, and the control flow rate is 15NL/min when deoxidation in the furnace is good and slag becomes white.

Further, the method comprises the following steps: the reducing agent is one or two of ferrosilicon, aluminum blocks and fluorite.

Further, the method comprises the following steps: in the third step, the oxygen blowing temperature is controlled to be 1600-1680 ℃.

Further, the method comprises the following steps: the electric arc furnace is a 40 ton EBT furnace.

Further, the method comprises the following steps: the bottom blowing position is the center circle of the bottom of the electric arc furnace, double bottom blowing holes are adopted, and an included angle of 120 degrees is formed between the two bottom blowing holes.

The invention has the beneficial effects that: the invention adopts the return materials of the steel grade and similar steel grades as smelting raw materials, and the dynamic conditions of the electric arc furnace for smelting special steel can be improved by stirring the bottom blowing gas in the return oxygen blowing smelting process, so that the heat transfer and mass transfer speed of a metal melting pool in the electric arc furnace is accelerated,the temperature and the components of the molten metal are uniform, and the Cr in the slag is reduced₂O₃The content of the alloy improves the alloy yield, shortens the special steel smelting time, reduces the production cost, and thus improves the special steel smelting capability of an electric arc furnace.

Drawings

FIG. 1 is a schematic view of the arrangement of bottom-blowing holes in the present invention;

labeled as: 1-arc furnace pole center circle, 2-electrode, 3-bottom blowing hole.

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be further described with reference to the accompanying drawings and examples.

The method for smelting special steel by returning the bottom-blowing electric arc furnace to the oxygen blowing method comprises the following steps:

preparing materials: the return material of the steel grade and similar steel grades is used as raw materials, the rest raw materials are scrap steel meeting the component requirements required by smelting the steel grade, and the addition amount of the return material is 45-60% of the total amount of the raw materials;

melting period: heating molten steel after electrifying a 40-ton EBT furnace, blowing nitrogen at the bottom while heating, wherein the flow of the nitrogen is 15NL/min, melting down the scrap steel, and heating the molten steel to 1580-1600 ℃;

and (3) oxidation period: when the temperature of the molten steel in the electric arc furnace meets the requirement, namely reaches 1580-1600 ℃, two oxygen blowing pipes are adopted to blow oxygen from a furnace door opening for fluxing until furnace materials are completely melted, the carbon content meets the requirement of smelting steel seeds, the pressure of oxygen blowing is controlled to be 0.8-1.8 Mpa, the temperature of oxygen blowing is controlled to be 1600-1680 ℃, argon is blown at the bottom while oxygen blowing, and the flow of argon blown at the bottom is controlled to be 20 NL/min;

and (3) reduction period: adding a reducing agent, wherein the reducing agent is one or two of ferrosilicon, aluminum blocks and fluorite, the adding amount of the reducing agent per ton of steel is 3.5-4.5 kg, bottom blowing argon is performed, the early-stage control flow is 25-35 NL/min when the argon is bottom blown, observing the atmosphere in the furnace, controlling the flow to be 15NL/min when the deoxidation in the furnace is good and the slag is whitened, sampling, and adjusting the component temperature;

tapping and pouring.

As shown in figure 1, three electrodes 2 in the electric arc furnace are uniformly distributed at the center circle 1 of the electric arc furnace at the bottom of the electric arc furnace in an annular shape, the process of bottom blowing gas is added in the process of smelting special steel by a return oxygen blowing method, a double-bottom blowing hole mode is adopted, two bottom blowing holes 3 are arranged on an annular ring formed by the three electrodes 2, an included angle of 120 degrees is formed between the two bottom blowing holes 3, bottom blowing gas is stirred through the two bottom blowing holes 3, the heat transfer speed and the mass transfer speed of a metal molten pool in the electric arc furnace are accelerated, the temperature and the components of molten metal are uniform, the time for smelting the special steel is shortened, the production cost is reduced, and the capacity of the electric arc furnace for smelting the special steel is improved.