阅读说明：本技术 一种中频炉熔炼方法 (intermediate frequency furnace smelting method ) 是由 毛凯田 程鹏 李栋 张松灿 寇联邦 陈艳萍 于 2019-09-06 设计创作，主要内容包括：本发明公开了钢水的一种中频炉熔炼方法。该熔炼方法包括冶炼和出钢,冶炼使用包括渣线层和透气塞的炉衬,出钢时采用上表面盖板遍布惰性气体出口的出钢小车。熔炼方法包括以下步骤：1)造还原渣；2)合金化,底吹氩净化钢水；3)惰性气体由出钢小车惰性气体出口排出；4)关闭氧气管和煤气管；5)钢渣混出,扒渣后加入保护渣。采用该熔炼方法,实现了钢水净化,为铸造行业生产优质铸件提供了条件。另外,该熔炼方法使得钢水中的气体含量和硫磷含量达到精炼水平,也使得合金元素的收得率大大提高。(the invention discloses a method for smelting molten steel in an intermediate frequency furnace. The smelting method comprises smelting and tapping, wherein a furnace lining comprising a slag line layer and a ventilation plug is used for smelting, and a tapping trolley with an upper surface cover plate extending over an inert gas outlet is adopted during tapping. The smelting method comprises the following steps: 1) making reducing slag; 2) alloying, bottom blowing argon to purify molten steel; 3) the inert gas is discharged from an inert gas outlet of the steel tapping trolley; 4) closing the oxygen pipe and the gas pipe; 5) mixing the steel slag, removing slag and adding the covering slag. By adopting the smelting method, the molten steel purification is realized, and conditions are provided for producing high-quality castings in the casting industry. In addition, the smelting method ensures that the gas content and the sulfur-phosphorus content in the molten steel reach the refining level and also greatly improves the yield of the alloy elements.)

1. The smelting method of the intermediate frequency furnace comprises smelting and tapping, and is characterized in that: the medium frequency furnace lining used for smelting comprises a slag line layer (2) and a ventilation plug (3), wherein the ventilation plug (3) is positioned in the center of the furnace bottom, and the slag line layer (2) is positioned at the upper part of the furnace lining and is built by magnesia carbon bricks; the steel tapping adopts a steel tapping trolley, the upper part of the steel tapping trolley is of a sandwich structure of an inert gas cavity (7), an inert gas outlet (8) is distributed on a cover plate on the upper surface of the sandwich layer, the inert gas cavity (7) is connected with an inert gas pipe (10), and a gas pipe (11) and an oxygen pipe (12) are installed at the rear part of the steel tapping trolley and are communicated with a ladle baking device of a steel ladle; the smelting method comprises the following steps:

1) After the molten steel is melted, making reducing slag, wherein the liquid level of the molten steel is higher than the bottommost line of the slag line layer (2), and the thickness of the slag layer of the reducing slag is not less than 50mm and is within the height range of the slag line layer (2);

2) Alloying in a reducing slag state, and blowing argon by a furnace bottom ventilating plug (3) to purify molten steel;

3) The tapping trolley moves to the front of the intermediate frequency furnace, inert gas enters an inert gas cavity (7) through an inert gas pipe (10) and is discharged from an inert gas outlet (8);

4) closing the oxygen pipe (12), and closing the gas pipe (11) when the mouth of the steel ladle has no flame;

5) Mixing the steel slag, removing slag and adding the covering slag.

2. The intermediate frequency furnace smelting method according to claim 1, characterized by comprising the following steps: and 2) during argon blowing in the step 2), the reducing slag cannot be exposed from the molten steel.

3. the intermediate frequency furnace smelting method according to claim 1, characterized by comprising the following steps: before the step 1), the following steps can be added: melting metal raw materials, tapping molten steel into a hand shaking ladle, blowing oxygen to remove phosphorus through a steel pipe, removing oxidation slag in the hand shaking ladle, and pouring the molten steel into an intermediate frequency furnace.

Technical Field

The invention is applied to the field of casting, and particularly relates to a method for smelting molten steel by using an intermediate frequency furnace.

Background

The cast steel smelting of the casting industry mostly adopts an intermediate frequency furnace. Because of the restriction of the furnace lining of the intermediate frequency furnace, in general, only deoxidation before tapping is carried out, desulfurization and deoxidation cannot be carried out, molten steel is always in contact with air and is in an oxidizing environment in the smelting and tapping processes, so that the content of easily-oxidized elements in the molten steel is unstable, the content of impurities and gas is high, and high-quality steel castings cannot be produced.

The furnace lining of the intermediate frequency furnace is generally divided into an acid furnace lining, a neutral furnace lining and an alkaline furnace lining. The acidic furnace lining takes silicon oxide as a main component, the neutral furnace lining takes aluminum oxide as a main component, and the alkaline furnace lining takes magnesium oxide as a main component. Because the melting point of the acid furnace lining is low and the thermal shock property of the basic furnace lining is poor, the neutral furnace lining or the magnesium aluminate spinel basic furnace lining is mostly adopted for the smelting of cast steel. However, the neutral alumina lining cannot be used for slagging and purifying molten steel, so that a magnesia-alumina spinel basic lining is required. Even if the service life of the furnace lining is very short, under the general condition that other parts of the furnace lining are good, the furnace lining is extremely seriously corroded at the slag line position for slagging, and a furnace leakage accident can be caused by one furnace, so that the intermediate frequency furnace can not make steel from the casting industry.

Disclosure of Invention

The technical problem solved by the invention is as follows: the smelting method of the intermediate frequency furnace is provided, so that smelting of reducing slag in the furnace and inert gas protection in the tapping process are realized, molten steel is purified, and the requirement of high-quality steel casting production is met.

The technical scheme adopted by the invention is as follows: the smelting method of the intermediate frequency furnace comprises smelting and tapping operations, wherein a furnace lining of the intermediate frequency furnace used for smelting comprises a slag line layer and a vent plug, the vent plug is arranged in the center of a furnace bottom, the slag line layer is positioned on the upper part of the furnace lining, and the slag line layer is built by adopting magnesia carbon bricks. The steel tapping trolley is adopted during steel tapping, the upper part of the steel tapping trolley is of a sandwich structure with an inert gas cavity, an inert gas outlet is distributed on a cover plate on the upper surface of a sandwich layer, the inert gas cavity is connected with an inert gas pipe, and a gas pipe and an oxygen pipe are arranged at the rear part of the steel tapping trolley and are communicated with a ladle baking device of a steel ladle. The smelting method of the intermediate frequency furnace comprises the following steps:

1) After molten steel is melted, the liquid level of the molten steel is higher than the bottommost line of the slag line layer, slagging auxiliary materials such as lime and the like are added for melting, and simultaneously deoxidizer is added for producing reducing slag, the thickness of the reducing slag is not less than 50mm, and the thickness of the slag layer is within the height range of the slag line layer;

2) Alloying in the state of reducing slag, blowing argon by a ventilating plug at the bottom of the furnace to purify the molten steel, and preventing the molten steel from exposing the reducing slag when blowing argon. After the components of the molten steel are adjusted to be qualified, heating and tapping;

3) the tapping trolley runs to the front of the intermediate frequency furnace, the inert gas enters the inert gas cavity through the inert gas pipe and is discharged from the inert gas outlet;

4) Closing the oxygen pipe, and closing the gas pipe when the mouth of the steel ladle has no flame;

5) Mixing the steel slag, removing slag and adding the covering slag.

further, before the step 1), an oxidation period can be increased, after the metal raw materials are melted, molten steel is tapped into a hand shaking ladle, oxygen is blown to the steel pipe to remove phosphorus, oxidation slag in the hand shaking ladle is removed, and the molten steel is poured into an intermediate frequency furnace.

The invention has the beneficial effects that: by adopting the smelting method, the content of inclusions and gas in the molten steel is greatly reduced, the purification purpose is achieved, and conditions are provided for producing high-quality castings in the casting industry. In addition, the yield of the alloy elements is greatly improved, and the content of harmful elements in the molten steel reaches the refining level.

Drawings

FIG. 1 is a schematic diagram of a furnace lining structure of an intermediate frequency furnace;

FIG. 2 is a top view of a slag line brick;

FIG. 3 is a front view of a slag line brick;

FIG. 4 is a schematic plan view of a slag line brick furnace lining;

FIG. 5 is a schematic structural view of the tapping trolley;

FIG. 6 is a schematic drawing of tapping of an intermediate frequency furnace;

Wherein: 1-furnace lining body, 2-slag line layer, 3-ventilating plug, 4-bump, 5-groove, 6-convex tip, 7-inert gas cavity, 8-inert gas outlet, 9-ladle seat, 10-inert gas pipe, 11-gas pipe, 12-oxygen pipe, 13-intermediate frequency furnace and 14-steel ladle.

Detailed Description

the smelting of molten steel in the intermediate frequency furnace needs slagging and inert gas introduction, so the furnace lining of the intermediate frequency furnace needs to be modified to meet the requirement of producing reducing slag. The attached figure 1 is a structural schematic diagram of a furnace lining of an intermediate frequency furnace meeting the slagging requirement, and the furnace lining of the intermediate frequency furnace consists of a furnace lining body 1, a slag line layer 2 and a ventilation plug 3. In order to meet the requirements of high-temperature smelting and cost of cast steel, the furnace lining body 1 is made of magnesium aluminate spinel, the slag line layer is made of slag line bricks with the structures shown in the attached figures 2-3, the slag line bricks are magnesia carbon bricks, the slag line bricks are resistant to corrosion of reducing slag, smelting of reducing slag produced by a medium-frequency furnace can be realized, and deoxidation and desulfurization in the reduction period can be realized. The air-permeable plug 3 is made of high-alumina refractory material, is dispersedly ventilated, is positioned in the center of the furnace bottom, and blows inert gas from the middle-frequency furnace bottom, thereby being beneficial to promoting the purification and the degassing of molten steel.

The attached drawings 2 and 3 are respectively a top view and a front view of the slag line brick, the slag line brick is respectively provided with a convex block 4 and a groove 5 which are matched with each other on an installation plane, preferably two convex blocks 4 or two grooves 5 are arranged on the installation plane, the schematic plane of a furnace lining formed by the matched installation of the convex blocks 4 and the grooves 5 is shown in the attached drawings 4, the matching between the convex blocks 4 and the grooves 5 has the positioning function and also has the function of increasing the sealing function, and the molten steel is prevented from penetrating through a slag line layer to cause steel leakage. The included angle of the two installation planes is 15 degrees, and the included angle of 15 degrees ensures that the slag line bricks can be combined into a closed perfect circle. The difference value of the two arc radiuses of the slag line brick is the thickness of the furnace lining, the size of the outer arc is consistent with that of the outer circle of the furnace lining body 1, and the size of the inner arc is consistent with that of the inner circle of the furnace lining body 1. The convex tips 6 are uniformly distributed on the plane contacted with the upper and lower furnace lining bodies, and the convex tips 6 can increase the binding force with the upper and lower furnace lining bodies.

the magnesia carbon brick is not resistant to oxidation slag corrosion, the medium frequency furnace is preferably not smelted in an oxidation period, and the molten steel is preferably dephosphorized by oxidation in a hand ladle. Tapping molten steel into a manual ladle, oxidizing and slagging off, pouring the dephosphorized molten steel into an intermediate frequency furnace, making reducing slag, and alloying and bottom blowing argon for purification. The smelting steps comprise: 1) and (4) an oxidation period. Melting metal raw materials, tapping molten steel into a hand ladle, adding slagging auxiliary materials such as lime and the like, and blowing oxygen to remove phosphorus through a steel pipe. Removing oxidation slag in the hand shaking ladle, and pouring the deoxidized molten steel into an intermediate frequency furnace; 2) and (4) a reduction period. Before the molten steel is used for manufacturing reducing slag, the liquid level of the molten steel is not lower than the bottommost line of a slag line layer. Adding slagging auxiliary materials such as lime and the like for melting, and simultaneously adding a deoxidizing agent for producing reducing slag, wherein the thickness of the reducing slag is not less than 50mm, and the thickness of a slag layer is within the height range of the slag line brick; 3) alloying purification period. Sampling and analyzing in the state of reducing slag, adding alloy material for alloying, blowing argon at the bottom of the furnace for purifying molten steel, wherein the stirred molten steel can not expose the reducing slag layer, and in the stirring process of the molten steel, impurities in the molten steel float upwards along with the stirring of the molten steel, and react with the reducing slag at a steel slag interface to realize deoxidation and desulfurization, and other impurities are bonded with the reducing slag and separated from the molten steel, thereby achieving the purpose of reducing the impurities such as oxides, sulfides and the like in the molten steel. Meanwhile, the inert gas blown into the molten steel can adsorb the gas in the molten steel and carry the gas out of the molten steel, thereby realizing the function of reducing the gas content in the molten steel. After the components of the molten steel are adjusted to be qualified, heating to prepare for tapping.

If the molten steel is smelted without oxidation treatment in the oxidation period, the oxygen blowing oxidation in a ladle can be removed in the smelting step, reducing slag is directly produced after the molten steel is smelted, argon is blown at the bottom of the furnace, and the molten steel is purified.

air oxidation is prevented when molten steel smelted by the intermediate frequency furnace is tapped, the tapping trolley shown in the attached drawing 5 is used for tapping, the left side in the drawing is the front part of the tapping trolley, and the right side is the rear part of the tapping trolley. An inert gas pipeline interface is designed at the rear part of the steel tapping trolley and is connected with an inert gas pipeline. An inert gas pipe 10 is installed in the steel tapping trolley, the upper surface of the steel tapping trolley is of a sandwich structure to form an inert gas cavity 7, and the inert gas pipe 10 is communicated with the inert gas cavity 7. Inert gas outlets 8 are uniformly arranged on the upper surface cover plate of the steel tapping trolley, and the inert gas outlets 8 are distributed on the upper surface cover plate of the trolley. The middle part of the upper surface of the steel tapping trolley is provided with a concave ladle seat 9 for placing a steel ladle. The rear part of the steel tapping trolley is also provided with a gas pipe 11 and an oxygen pipe 12 which are communicated with a ladle baking device of the steel ladle and used for baking the ladle. The track of the tapping trolley is connected with the ladle baking area and the tapping area in front of the intermediate frequency furnace.

before tapping, the ladle 14 is placed into the ladle seat 9 of the tapping trolley, and after stable placement, the ladle is baked in a ladle baking area. When the intermediate frequency furnace finishes smelting and tapping, the tapping trolley 12 moves to the front of the furnace, as shown in the attached figure 6. The steel tapping operation comprises the following steps: opening an inert gas pipeline valve, and allowing the inert gas to enter an inert gas cavity 7 through an inert gas pipe 10 and be discharged from an inert gas outlet 8. Because the upper cover plate of the steel tapping trolley is distributed over the inert gas outlet, the inert gas can exhaust the air around the ladle 14, surround the ladle 14 and isolate the air; secondly, the valve of the oxygen pipe 12 is closed, when the mouth of the steel ladle 14 has no flame, the valve of the gas pipe 11 is closed, and no air exists in the steel ladle 14; and tilting the intermediate frequency furnace 13 to tap steel. During tapping, molten steel flows into the ladle 14 in an air-free environment and is not oxidized.

During tapping, the steel slag is preferably mixed out, the molten steel is fully contacted with the interface of the reducing slag, the reaction, desulfurization and deoxidation of the steel slag are facilitated, and impurities are further taken out. Meanwhile, the reducing slag protects the surface of the molten steel, and the reducing slag is prevented from contacting with air in the lifting process of the steel ladle, so that the molten steel is protected. And reducing slag can be removed after tapping to avoid resulfurization, covering slag is added, and the liquid level of the molten steel is isolated from air by the covering slag to play a role in protection.

By adopting the smelting method, the molten steel is always isolated from the air in the reduction period and the tapping process, the smelting quality of the molten steel is improved, the inclusion content is greatly reduced, the molten steel is purified, and the guarantee is provided for producing high-quality castings. The gas content and the content of harmful elements are greatly reduced, and the following table 1 shows that the gas content and the sulfur-phosphorus content of molten steel in a ladle are almost the same as those of refined steel-making when low alloy steel is smelted. Therefore, the smelting quality of the molten steel reaches the refining level by adopting the intermediate frequency furnace smelting method.

TABLE 1 gas and Sulfur phosphorus content

Element(s)	N/ppm	H/ppm	O/ppm	P/%	S/%
						content (wt.)	80-180	1.2-2.2	30-110	0.015-0.025	0.004-0.009

in addition, when high alloy steel is smelted, the yield of each alloy element in alloying is shown in table 2, and it can be seen that not only the content of Ti and Al easily-oxidizable elements is stable, but also the yield is obviously improved, and is improved by more than 2 times compared with the conventional yield of 30%. The yield of Cr and Mo alloy elements is 100 percent, which is higher than the conventional yield of 90-96 percent.

TABLE 2 yield of alloying elements

The magnesia carbon brick furnace lining and the steel tapping trolley, particularly the use of the magnesia carbon brick, change the traditional view that the intermediate frequency furnace can not make steel, realize dephosphorization in the oxidation period, deoxidation and desulfurization in the reduction period, protective gas purification before steel tapping and the like of smelting, and steel tapping in an oxygen-free environment, complete molten steel purification and protective steel tapping, improve the molten steel melting quality of the intermediate frequency furnace, and provide conditions for producing high-quality castings in the casting industry. In particular to the use of magnesia carbon bricks, which lays an equipment foundation for the refining of an intermediate frequency furnace. By adopting the smelting method, the yield of the alloy elements is greatly improved, and the gas content and the sulfur-phosphorus content in the molten steel reach the refining level.