阅读说明：本技术 一种防结瘤高硫非调质钢冶炼工艺 (Anti-nodulation high-sulfur non-quenched and tempered steel smelting process ) 是由 徐必靖 任振海 陈占领 朱富强 赵阳 李亚 刘泽 于 2020-06-19 设计创作，主要内容包括：本发明属于非调质钢冶炼技术领域,具体涉及一种防结瘤高硫非调质钢冶炼工艺。为了解决本发明特定钢成分的在冶炼过程中,钢中的夹杂物最终是以高熔点的镁铝尖晶石类夹杂物裹合硫化钙形成的复合夹杂的问题,明确了关键操作工艺精炼渣的控制,如精炼中控制炉渣二元碱度(CaO/SiO<Sub>2</Sub>)2.5-3.5,是增加炉渣对该类夹杂物的吸附性能；通过控制三元碱度来调节炉渣的流动性,两者相互协同后才能保证控制连铸浇注过程结瘤的关键因子,本发明还明确VD真空处理后喂线顺序及时间要求,有效控制氧化物夹杂向低熔点夹杂物转变,同时防止高熔点硫化物夹杂的大量生成,最终使钢水在连铸浇注过程中,浇注曲线平稳,液面无波动。(The invention belongs to the technical field of non-quenched and tempered steel smelting, and particularly relates to an anti-nodulation high-sulfur non-quenched and tempered steel smelting process. In order to solve the problem that the inclusion in the steel is finally a composite inclusion formed by wrapping calcium sulfide with high-melting-point magnesium aluminate spinel type inclusion in the smelting process of specific steel components, the invention defines the control of the refining slag of key operation process, such as the control of the binary basicity (CaO/SiO) of the slag in the refining process 2 )2.5-3.5, which is to increase the adsorption performance of slag on the impurities; the invention also defines the wire feeding sequence and time requirements after VD vacuum treatment, effectively controls the transformation of oxide inclusions to low-melting-point inclusions, and simultaneously prevents a large amount of high-melting-point sulfide inclusions from being generated, thereby finally ensuring that the pouring curve of the molten steel is stable and the liquid level has no fluctuation in the continuous casting pouring process.)

1. A smelting process of anti-caking high-sulfur non-quenched and tempered steel is characterized by comprising the following steps of: the anti-nodulation high-sulfur non-quenched and tempered steel comprises the following components in percentage by weight: 0.40 to 0.45 percent of carbon, 0.30 to 0.50 percent of silicon, 1.20 to 1.50 percent of manganese, less than or equal to 0.030 percent of phosphorus, 0.035 to 0.075 percent of sulfur, less than or equal to 0.25 percent of chromium, less than or equal to 0.25 percent of nickel, less than or equal to 0.20 percent of copper, 0.010 to 0.040 percent of aluminum, 0.06 to 0.10 percent of vanadium, less than or equal to 0.25 percent of molybdenum, 0.02 to 0.04 percent of niobium, 0.0100 to 0.0150 percent of nitrogen, and the balance of iron;

the smelting process of the anti-nodulation high-sulfur non-quenched and tempered steel comprises the following steps:

(1) electric furnace smelting: controlling the carbon content of the steel in the electric furnace smelting, controlling the carbon content to be 0.08-0.25%, simultaneously controlling the steel tapping temperature to be more than 1600 ℃, controlling the phosphorus requirement at the smelting end point of the electric furnace to be less than or equal to 0.018%, and strictly prohibiting slag discharging in the steel tapping process;

(2) deoxidizing and adding aluminum blocks in the electric furnace tapping process, adding the aluminum blocks in two times, and adding the aluminum blocks in the second time together with the alloy and other auxiliary materials in the tapping process;

(3) ladle refining: controlling the binary basicity (CaO/SiO) of slag during refining₂) 2.5-3.5; controlling the ternary alkalinity (CaO/(SiO) of the slag₂+Al₂O₃))1.10-1.25；

(4) VD vacuum refining: the pressure maintaining time of VD vacuum treatment high vacuum (<67Pa) is more than or equal to 10 minutes, the argon flow is adjusted in the high vacuum pressure maintaining process, after the VD vacuum treatment is broken, the thread feeding amount is adjusted according to the sampling result, and the thread feeding sequence is aluminum thread → manganese nitrogen thread → calcium silicon thread → sulfur thread;

(5) the continuous casting adopts full-protection casting, the long nozzle and the tundish are sealed by argon, and the tundish uses an alkaline covering agent.

2. The process for smelting the nodulation-preventing high-sulfur non-quenched and tempered steel according to claim 1, wherein: in the electric furnace smelting in the step (1), the proportion of the ladle slag charge is 500kg lime and 550kg slagging agent per furnace in the tapping process, so that the condition that the molten steel is refined and the ladle slag is melted is good, and no slag charge is accumulated.

3. The process for smelting the nodulation-preventing high-sulfur non-quenched and tempered steel according to claim 1, wherein: in the ladle refining in the step (3), the refining furnace controls the aluminum content in the steel in the smelting process, the tapping aluminum is controlled to be 0.030-0.040%, and the temperature rise in large gears is strictly forbidden before tapping.

4. The process for smelting the nodulation-preventing high-sulfur non-quenched and tempered steel according to claim 1, wherein: in the VD vacuum refining in the step (4), the flow of argon is adjusted to be 30-80ml// min in the vacuum pressure maintaining process.

5. The process for smelting the nodulation-preventing high-sulfur non-quenched and tempered steel according to claim 1, wherein: in the VD vacuum refining in the step (4), after the silicon-calcium wire is fed, argon gas is required to be soft-blown for more than 10 minutes, then the sulfur wire is fed, and after the sulfur wire is fed, the soft-blowing time is required to be ensured for more than 15 minutes, and then the steel wire can be hung on a ladle for continuous casting and pouring.

6. The process for smelting the nodulation-preventing high-sulfur non-quenched and tempered steel according to claim 1, wherein: in the continuous casting procedure in the step (5), the drawing speed is 0.85-0.95m/min, the electric stirring parameter of the crystallizer is 200A/2.5Hz, and medium-carbon sulfur-containing steel casting powder is used.

Technical Field

The invention belongs to the technical field of non-quenched and tempered steel smelting, and particularly relates to an anti-nodulation high-sulfur non-quenched and tempered steel smelting process.

Background

The non-quenched and tempered steel is a green energy-saving steel developed along with international energy shortage in the 70 th century, and the non-quenched and tempered steel omits quenching and high-temperature tempering processes, so that the production process is simplified, the energy consumption is reduced, and the non-quenched and tempered steel is widely applied to automobile parts. Wherein the high-sulfur non-quenched and tempered steel belongs to an important variety of S-containing Al-containing free-cutting non-quenched and tempered steel, and the non-quenched and tempered steel has higher contentThe sulfur and the aluminum are easy to generate high-melting-point composite impurities in the casting process, namely, the impurities are gathered on the inner wall of the water gap, have the characteristics of high melting point, no deformation and the like, and are easy to gather and grow on the inner wall of the water gap to cause nodulation and blockage, so that the liquid level of a crystallizer fluctuates, the stability of a casting curve is poor, a large amount of waste products are generated, and the defects of subcutaneous slag inclusion and the like of a subsequent rolled material are easy to cause. For different specific steel types, the types of inclusions in steel are different, and the control means is naturally different. For the steel grade with the components within the limited range of the invention, the formed inclusions are finally composite inclusions (CaO-Al) formed by wrapping calcium sulfide with high-melting-point magnesium aluminate spinel type inclusions₂O₃MgO-CaS), and because the wire feeding treatment of various wires is involved in the VD vacuum treatment, the quantity of inclusions in the steel is easily increased or the inclusions are not completely denatured to cause the nozzle nodulation in the continuous casting process, and the complexity degree is far higher than that of the conventional aluminum-containing sulfur-containing steel, so how to remove the high-melting-point composite inclusions of the specific type and avoid the nodulation phenomenon in the continuous casting process is the technical problem to be solved by the invention.

The invention provides an effective smelting operation process, which can effectively prevent the high-sulfur non-quenched and tempered steel from generating nodulation in the continuous casting and pouring process, thereby stabilizing the pouring curve, reducing the product quality defects, improving the product percent of pass and improving the product quality.

Disclosure of Invention

In order to solve the technical problems, the invention provides an anti-nodulation high-sulfur non-quenched and tempered steel smelting process, in which the invention controls the binary basicity (CaO/SiO) of slag₂) The ternary alkalinity, the wire feeding sequence in the soft blowing and the like are controlled, so that the pouring curve of the molten steel is stable, the liquid level is free from fluctuation in the continuous casting and pouring process, the product scrap rate is greatly reduced, and the product quality is improved.

In order to achieve the technical purpose, the invention adopts the technical scheme that:

an anti-nodulation high-sulfur non-quenched and tempered steel comprises the following components in percentage by weight: 0.40 to 0.45 percent of carbon, 0.30 to 0.50 percent of silicon, 1.20 to 1.50 percent of manganese, less than or equal to 0.030 percent of phosphorus, 0.035 to 0.075 percent of sulfur, less than or equal to 0.25 percent of chromium, less than or equal to 0.25 percent of nickel, less than or equal to 0.20 percent of copper, 0.010 to 0.040 percent of aluminum, 0.06 to 0.10 percent of vanadium, less than or equal to 0.25 percent of molybdenum, 0.02 to 0.04 percent of niobium, 0.0100 to 0.0150 percent of nitrogen and the balance of iron.

The smelting process flow comprises the following steps: electric furnace blowing → ladle refining → VD vacuum refining → continuous casting protective pouring;

(1) the carbon content of the steel is controlled by electric furnace smelting, the carbon is controlled to be 0.08-0.25 percent, the aim is to reduce the oxygen activity of molten steel at the smelting end point of the electric furnace and reduce the deoxidation difficulty of the next procedure, and meanwhile, the steel tapping temperature is required to be more than 1600 ℃. The phosphorus requirement of the electric furnace smelting end point is less than or equal to 0.018 percent, slag is strictly forbidden to be discharged in the tapping process, and the phosphorus of the finished product is ensured to be less than or equal to 0.020 percent.

(2) And adding 120kg of aluminum blocks per furnace in deoxidation in the electric furnace tapping process, wherein the aluminum blocks are added in twice, 30kg of aluminum blocks are added when 30 tons of steel are placed for the first time, and 90kg of aluminum blocks are added together with the alloy, lime and slag melting agent auxiliary materials in the tapping process for the second time. The proportion of the ladle slag charge to 500kg lime plus 550kg slagging agent/furnace in the tapping process ensures that the slag melting condition of the ladle after molten steel is refined is good and no slag charge is accumulated.

(3) The refining furnace supplements and adjusts slag charge according to the condition of the slag in the smelting process in a small amount, improves the diffusion deoxidation efficiency of the slag surface of the ladle by using aluminum particles, and controls the alkalinity and the fluidity of the slag. Control of the binary basicity (CaO/SiO) of the slag₂)2.5-3.5, ensuring that the slag has good adsorption performance on the impurities; controlling the ternary alkalinity (CaO/(SiO) of the slag₂+Al₂O₃) 1.05-1.25) to ensure good flow properties of the slag.

Further, the refining furnace controls the aluminum content in the steel in the smelting process and controls the argon gas to adjust. The argon is controlled to be 15 minutes at the early stage of refining, the flow is controlled to be 400 ml/min, the flow is controlled to be 50-150 ml/min at the middle and later stages, long-time large argon stirring is avoided, the tapping aluminum is controlled to be 0.030% -0.040%, large gear temperature rise is strictly forbidden before tapping, and the influence on slag is avoided.

The inclusion in steel is continuously changed along with the smelting process in the refining process, and in the process of the invention, the inclusion in steel is finally wrapped by the inclusion of high-melting-point magnesium aluminate spinelComposite inclusion (CaO-Al) formed by calcium sulfide₂O₃-MgO-CaS). The binary basicity (CaO/SiO) of the slag is controlled in the process of the invention₂)2.5-3.5, the adsorption performance of the slag on the inclusions is increased, the ternary alkalinity is cooperatively controlled to adjust the fluidity of the slag, and the expected effect of removing the inclusions can be achieved only after the slag is mutually cooperated.

(4) The pressure maintaining time of VD vacuum treatment high vacuum (67 Pa) is more than or equal to 10 minutes, the flow of argon is adjusted in the high vacuum pressure maintaining process, the molten steel is slightly turned out of the slag surface in the high vacuum treatment process, and the large-flow stirring of the steel slag is avoided. Before the vacuum treatment is finished, the flow of argon is adjusted to be 30-80 ml/min (preferably 50 ml/min), so that the slag surface slightly creeps after the vacuum is broken, and the molten steel does not turn over the slag surface.

(5) After VD vacuum processing is broken, sampling, adjusting the wire feeding amount according to the result, wherein the wire feeding sequence is aluminum wire → nitrogen-manganese wire → calcium silicon wire → sulfur wire, the wire feeding time of the aluminum wire, the nitrogen-manganese wire and the calcium silicon wire is vacuum broken, and then wire feeding processing is carried out according to the wire feeding sequence according to the components of molten steel, after the calcium silicon wire is fed, the molten steel must be fed into the iron sulfur wire after argon soft blowing for more than 10 minutes (preferably 15 minutes), and after the sulfur wire is fed, the soft blowing time must be ensured for more than 15 minutes (preferably 15-25 minutes) before continuous casting on a ladle is carried out for pouring.

Further, after VD is broken, feeding a calcium silicate wire, controlling the wire feeding speed to be 150 plus 180 m/min, adding a covering agent to weakly stir the molten steel for more than 10 min, and then feeding a pure sulfur wire. The purpose is as follows: the wire feeding speed control of the calcium-silicon wire is mainly used for preventing calcium from effectively entering molten steel due to too low feeding speed, and the wire feeding speed is too high, so that the local calcium concentration in the molten steel is easily too high, and a large amount of calcium sulfide impurities are produced.

The VD vacuum treatment in the invention relates to the wire feeding treatment of 4 kinds of silk wires, the treatment is more complex compared with the conventional vacuum treatment, and the aluminum wire → the nitrogen-manganese wire → the silicon-calcium wire → the sulfur wire must be strictly arranged according to the wire feeding sequence in the step, otherwise, the number of inclusions in steel is increased or the inclusions are not completely denatured, so that the nozzle nodulation is caused in the continuous casting process. After the treatment is carried out according to the silk thread feeding sequence, the soft blowing time of the molten steel is controlled to be 15-20 minutes, and the soft blowing is not required to be carried out for a long time (preferably 30-60 minutes), so that the waste on the production cost is caused.

The continuous casting adopts full-protection casting, the long nozzle and the tundish are sealed by argon, and the tundish uses an alkaline covering agent.

The invention has the following advantages:

1. the invention defines the control of the refining slag of the key operation process: binary basicity (CaO/SiO) of slag₂)2.5-3.5, ternary basicity of slag (CaO/(SiO)₂+Al₂O₃) 1.05-1.20 while ensuring good adsorption of slag on inclusions and good flow properties of the slag. The alkalinity of the slag is very critical to the adsorption and removal of oxide and sulfide inclusions and is a key factor for controlling nodulation in the continuous casting process.

2. The invention defines the wire feeding sequence and time requirements after VD vacuum treatment, effectively controls the transformation of oxide inclusions to low-melting-point inclusions, prevents the high-melting-point sulfide inclusions from generating in large quantity, and is also a key factor for controlling nodulation in the continuous casting and pouring process.

3. The molten steel smelted according to the method has stable pouring curve and no fluctuation of the liquid level in the continuous casting pouring process, thereby greatly reducing the product scrap and improving the product quality.

The scheme is simple, effective and easy to implement, can save energy consumption and reduce production cost, and provides a method for solving the technical problem for producing similar steel grades.

Drawings

FIG. 1 is a graph of the continuous casting process of example 1.

As can be seen from FIG. 1, the molten steel smelted by the process of the present invention has a stable casting curve and no fluctuation of the liquid level during the continuous casting process.

FIG. 2 shows the inner wall of the tundish immersion nozzle of embodiment 1 after the use of the lower line.

As can be seen from FIG. 2, in the molten steel produced by the process of the present invention, the inner diameter of the nozzle before the use of the tundish submerged nozzle was 40mm, and the inner wall after the use was not clogged with flocs and was not changed.

FIG. 3 is a graph showing the continuous casting process of comparative example 1.

As can be seen from FIG. 3, in the continuous casting of the molten steel of comparative example 1, the unstable fluctuation of the casting curve is significant, the fluctuation of the liquid level, the rising of the stopper rod and the serious nodulation are observed.

Detailed Description