阅读说明：本技术 一种通过施加界面电场防止稀土钢水口脱碳及反应行为的方法 (Method for preventing decarburization and reaction behavior of rare earth steel nozzle by applying interface electric field ) 是由 田晨 袁磊 李延 温天朋 姚形龙 刘震丽 于景坤 于 2020-12-10 设计创作，主要内容包括：本发明涉及连铸领域,具体涉及一种通过施加界面电场防止稀土钢水口脱碳及反应行为的方法。本方法具体包括步骤(1)提前将高温导线均匀的埋入水口内部；(2)再连接电源；(3)水口在线预热烘烤；(4)插入锆碳质耐材棒形成闭合回路；(5)全程通电处理,构建界面电场。利用本发明所述方法不仅可以有效地抑制含碳水口材料的脱碳行为,同时还可以有效地抑制水口与稀土等活泼合金元素间的反应。在有效地保护水口材料不被破坏的同时也避免了水口内壁出现结瘤的问题。(The invention relates to the field of continuous casting, in particular to a method for preventing the decarburization and the reaction behavior of a rare earth steel nozzle by applying an interface electric field. The method specifically comprises the steps of (1) uniformly burying a high-temperature lead into a water gap in advance; (2) then connecting with a power supply; (3) preheating and baking the water gap on line; (4) inserting a zirconium carbon refractory bar to form a closed loop; (5) and carrying out whole-process electrifying treatment to construct an interface electric field. The method of the invention can effectively inhibit the decarbonization of the material containing the carbon nozzle, and can also effectively inhibit the reaction between the nozzle and active alloy elements such as rare earth and the like. The problem of nodulation on the inner wall of the water gap is avoided while the water gap material is effectively protected from being damaged.)

1. A method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interface electric field is characterized by comprising the following steps of:

(1) high-temperature wires are uniformly embedded into the water gap in advance: when the water gap is produced, the high-temperature conducting wire is uniformly inserted into the water gap in advance, and a special water gap with the embedded conducting wire is directly obtained after compression molding;

(2) connecting a power supply: connecting and fixing a high-temperature lead pre-embedded into the water gap and one end of an epitaxial lead, connecting the other end of the epitaxial lead to the positive electrode of a power supply, and connecting the negative electrode of the power supply with a zirconium-carbon refractory rod through the epitaxial lead;

(3) and (3) carrying out online preheating baking on the water gap connected in the step (2) before continuous casting.

(4) During continuous casting, a zirconium-carbon refractory bar is vertically inserted into molten steel to form a complete closed loop with a water gap;

(5) constructing an interface electric field: in the casting process, a stable forward electric field is applied to the inner wall of the nozzle in the whole process, so that decarburization, erosion and nodulation of the nozzle are prevented.

2. The method of claim 1, wherein the nozzle in step (1) comprises a long nozzle and a submerged nozzle, and the nozzle is made of a refractory material containing carbon, including alumino-carbon, magnesia-carbon or zirconia-carbon.

3. The method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interfacial electric field according to claim 1, wherein the high temperature wire of step (1) has a diameter of 1.0 to 3.0mm and is made of a metal material having a relatively high melting point, including platinum, molybdenum, tantalum or iron; the embedding depth of the high-temperature lead is 0.5-1.5cm away from the outer wall of the water gap.

4. The method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interfacial electric field according to claim 1, wherein the epitaxial wire in step (2) is a ferrous or copper metal wire.

5. The method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interfacial electric field according to claim 1, wherein in the step (2), the diameter of the zirconium-carbon refractory rod is not less than 3cm, the content of zirconia in the zirconium-carbon refractory rod is not less than 70%, and the content of graphite is not less than 20%.

6. The method for preventing the decarburization and the reaction behavior of a rare earth steel nozzle by applying an interfacial electric field according to claim 1, wherein the insertion depth of the zirconium carbon refractory rod in step (4) is 5 to 10cm beyond the mold flux; when selecting the long nozzle for use, the refractory material stick of zirconium carbon inserts equipment and is the pouring basket, when selecting the immersion nozzle for use, refractory material stick of zirconium carbon inserts equipment and is the crystallizer.

7. The method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interfacial electric field according to claim 1, wherein the electric field in the step (5) is a pulsed electric field or a steady direct current electric field; the output voltage is not higher than 36V, and the output current is controlled between 2A and 200A according to the type and content of the added rare earth; when a pulsed electric field is used, the pulse frequency is between 1000Hz-50000 Hz.

8. The method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interfacial electric field according to claim 1, wherein the step (1) of uniformly embedding the high temperature wire into the interior of the nozzle in advance can also be a step of grooving the outer wall of the already formed nozzle: uniformly and symmetrically grooving from below 10cm of the top of the water gap to above a slag line of the water gap, embedding a lead, sealing the groove by using a carbon-containing high-temperature binder, and then wrapping refractory cotton for sealing.

Technical Field

The invention relates to the field of continuous casting, in particular to a method for preventing the decarburization and the reaction behavior of a rare earth steel nozzle by applying an interface electric field.

Background

The large-scale popularization and popularization of the continuous casting process obviously improve the overall production efficiency of ferrous metallurgy. With the progressive maturity of continuous casting processes, more and more steel grades have also been transformed from the initial traditional die casting production to efficient continuous casting production.

However, in the actual continuous casting process, inclusions in steel and molten steel can continuously generate adhesion and reaction behaviors on the inner wall of the nozzle, and some active alloy elements in the steel can also generate strong chemical reactions with the nozzle material to further accelerate the nodulation speed. For example: the rare earth has stronger deoxidizing capacity than aluminum in steel, can modify inclusions and the like, so that the quality and the performance of the rare earth steel are better than those of the traditional aluminum killed steel. Therefore, in the smelting process of many high-end steel products, some rare earth is added to improve the quality of the steel products. However, in the current smelting process of rare earth steel, rare earth metals and rare earth inclusions thereof are easy to adhere and react on the wall surface of a nozzle to cause nozzle nodulation and blockage. This may cause a change in the flow field inside the nozzle, which may seriously affect the flow trajectory of the molten steel and the flow state of the molten steel. Not only greatly influences the final quality of steel, but also restricts the yield and development of rare earth steel.

At present, however, the existing conventional nozzle nodulation solution mostly prevents nodulation by means of changing materials such as adjusting process parameters of a smelting process, blowing Ar protection, changing the shape of a nozzle, calcification treatment, adding a zirconium-containing slag line and the like. However, these solutions have little effect on the actual continuous casting of rare earth steel, and the current situation of extremely low rare earth yield is not changed. Especially when the rare earth feeding amount is too high, the reaction behavior between the rare earth element and the water gap can not be controlled. The fundamental reason for this is that the reaction between the rare earth element and the nozzle cannot be suppressed. In addition, both long and submerged entry nozzles are carbon-containing refractory materials. In the continuous casting process, the carbon element can continuously generate decarburization action to gradually roughen the inner wall of the nozzle, and the rare earth and the inclusions thereof can be promoted to be more easily contacted and reacted with the nozzle. Becomes another great hidden trouble influencing the safe and efficient service of the water gap.

As for rare earth metals, the rare earth metals have extremely strong oxidizing capability, and are easy to react with materials in a water gap to produce rare earth compounds, so that nodules are formed. The surface of the nodules is rough, so that rare earth and inclusions in steel can be easily adhered and reacted on the nodules generated before, and the rare earth nodules grow up continuously. The conventional steel grade nodulation is mainly caused by the adhesion and aggregation of related inclusions on the inner wall of the nozzle.

Therefore, if a technical method capable of effectively protecting the structure and functionality of the nozzle during the continuous casting production process to prevent the nozzle from decarbonization and reaction is developed, it becomes a key to restrict and limit the wide application of rare earth in the continuous casting process and improve the continuous casting production quality of rare earth steel.

Disclosure of Invention

In order to solve the problems, the invention provides a method for preventing the decarburization and the reaction behavior of a rare earth steel nozzle by applying an interface electric field. The method of the invention can effectively inhibit the decarbonization of the carbon-containing nozzle material, and can also effectively inhibit the reaction between the nozzle and active alloy elements such as rare earth, and the like, thereby effectively protecting the nozzle material from being damaged and avoiding the problem of nodulation on the inner wall of the nozzle.

The specific technical scheme of the invention is as follows:

a method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interface electric field comprises the following steps:

(1) high-temperature wires are uniformly embedded into the water gap in advance: when the water gap is produced, the high-temperature conducting wire is uniformly inserted into the water gap in advance, and a special water gap with the embedded conducting wire is directly obtained after compression molding;

(2) connecting a power supply: and (3) connecting and fixing a high-temperature lead pre-embedded in the water gap and one end of an epitaxial lead, connecting the other end of the epitaxial lead to the positive electrode of a power supply, and connecting the negative electrode of the power supply with the zirconium-carbon refractory rod through the epitaxial lead.

(3) And (3) carrying out online preheating baking on the water gap connected in the step (2) before continuous casting.

(4) During continuous casting, a zirconium-carbon refractory bar is vertically inserted into molten steel to form a complete closed loop with a water gap;

(5) constructing an interface electric field: in the casting process, a stable forward electric field is applied to the inner wall of the nozzle in the whole process, so that decarburization, erosion and nodulation of the nozzle are prevented.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interface electric field, the nozzle in the step (1) comprises a long nozzle and a submerged nozzle, and the nozzle is made of a refractory material containing carbon, including aluminum carbon, magnesium carbon or zirconium carbon.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interface electric field, in the step (1), the diameter of the high-temperature wire is 1.0-3.0mm, and the material is a metal material with a higher melting point, including metal platinum, metal molybdenum, metal tantalum or metal iron, preferably metal molybdenum; the embedding depth of the high-temperature lead is 0.5-1.5cm away from the outer wall of the water gap.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interface electric field, the epitaxial lead in the step (2) is an iron or copper metal lead.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interface electric field, the diameter of the zirconium-carbon refractory rod in the step (2) is more than or equal to 3cm, the content of zirconium oxide in the zirconium-carbon refractory rod is more than or equal to 70%, and the content of graphite is more than or equal to 20%.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interface electric field, the insertion depth of the zirconium carbon refractory rod in the step (4) is 5-10cm beyond the mold flux; when selecting the long nozzle for use, the refractory material stick of zirconium carbon inserts equipment and is the pouring basket, when selecting the immersion nozzle for use, refractory material stick of zirconium carbon inserts equipment and is the crystallizer.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interface electric field, the electric field in the step (5) adopts a pulse electric field or a stable direct current electric field, preferably a pulse electric field; the output voltage is not higher than 36V, and the output current is controlled between 2A and 200A according to the type and content of the added rare earth; when a pulsed electric field is used, the pulse frequency is between 1000Hz-50000 Hz.

Further, in the method for preventing the decarburization and the reaction of the rare earth steel nozzle by applying the interfacial electric field, the step (1) of uniformly embedding the high-temperature wire into the nozzle in advance can also be a step of performing grooving treatment on the outer wall of the formed nozzle: uniformly and symmetrically grooving from below 10cm of the top of the water gap to above a slag line of the water gap, embedding a lead, sealing the groove by using a carbon-containing high-temperature binder, and then wrapping refractory cotton for sealing.

The invention has the beneficial effects that:

the technical method of the invention can enable the whole water gap-molten steel-zirconium carbon refractory rod to form a stable loop, and during the electrifying process, the method can enable the wall surface of the water gap to form a stable positive electric field, although the stable electric field can not directly prevent the chemical reaction behavior between the water gap material and the rare earth element, under the regulation and control of the specific electric field parameters of the invention, the newly generated reactant can be more stable and firm, and further a brand new light, thin, stable, uniform and compact rare earth nodulation protective layer can be formed on the inner wall of the water gap. On one hand, the protective layer can effectively prevent carbon elements such as graphite and the like in the water gap from permeating, dissolving and oxidizing into molten steel; on the other hand, the protective layer has good chemical stability, and under the action of the positive electric field, the protective layer does not have any chemical reaction with rare earth alloy, rare earth inclusions and other inclusions in steel, the adhesion phenomenon of the inclusions is reduced, even if the adhesion of the inclusions occurs, the adhered objects become more uniform and stable under the action of the electric field, the phenomenon that the inclusions adhere to the wall surface of a water gap to cause extremely large surface roughness when the positive electric field is not applied is avoided, the phenomenon that the inclusions are easy to be washed off for the second time is avoided, and the phenomena that the structure of nodules formed after the adhesion and the reaction inside the water gap are more loose, the surface roughness is extremely large and the like are avoided. The reaction effect and the nodulation rate of the water gap under the regulation and the protection of the electric field are obviously reduced and improved, the phenomena that the rare earth continuously reacts with the inner wall of the water gap and the rare earth nodulation thereof when the electric field is not applied and the thickness of the rare earth nodulation continuously increases until the water gap is completely blocked can not occur as the existing production conditions, and the normal operation of continuous casting is effectively ensured.

Detailed Description

A method for preventing the decarburization and the reaction of a rare earth steel nozzle by applying an interface electric field comprises the following steps:

(1) high-temperature wires are uniformly embedded into the water gap in advance: when the water gap is produced, the high-temperature conducting wire is uniformly inserted into the water gap in advance, and a special water gap with the embedded conducting wire is directly obtained after compression molding; or grooving the outer wall of the formed water gap: uniformly and symmetrically grooving from below 10cm of the top of the water gap to above a slag line of the water gap, embedding a lead, sealing the groove by using a carbon-containing high-temperature binder, and then wrapping refractory cotton for sealing. The water gap comprises a long water gap and an immersed water gap, and is made of carbon materials including aluminum carbon, magnesium carbon or zirconium carbon. The diameter of the high-temperature lead is 1.0-3.0mm, the material is a metal material with a higher melting point, and the metal material comprises metal platinum, metal molybdenum, metal tantalum or metal iron, and preferably metal molybdenum; the embedding depth of the high-temperature lead is 0.5-1.5cm away from the outer wall of the water gap.

(2) Connecting a power supply: and (3) connecting and fixing a high-temperature lead pre-embedded in the water gap and one end of an epitaxial lead, connecting the other end of the epitaxial lead to the positive electrode of a power supply, and connecting the negative electrode of the power supply with the zirconium-carbon refractory rod through the epitaxial lead. The diameter of the zirconium-carbon refractory rod is more than or equal to 3cm, the content of zirconium oxide in the zirconium-carbon refractory rod is more than or equal to 70%, and the content of graphite is more than or equal to 20%; the extension lead is an iron or copper metal lead.

(3) And (3) carrying out moderate online preheating baking on the water gap connected in the step (2) before continuous casting.

(4) During continuous casting, a zirconium-carbon refractory bar is vertically inserted into molten steel to form a complete closed loop with a water gap; the insertion depth of the zirconium carbon refractory material rod is 5-10cm after the zirconium carbon refractory material rod passes through the covering slag; when selecting the long nozzle for use, the refractory material stick of zirconium carbon inserts equipment and is the pouring basket, when selecting the immersion nozzle for use, refractory material stick of zirconium carbon inserts equipment and is the crystallizer.

(5) Constructing an interface electric field: in the casting process, a stable forward electric field is applied to the inner wall of the nozzle in the whole process, so that the nozzle is prevented from decarbonizing and reacting. The electric field adopts a pulse electric field or a stable direct current electric field, and preferably a pulse electric field; the output voltage is not higher than 36V, and the output current is controlled between 2A and 200A according to the type and content of the added rare earth; when a pulsed electric field is used, the pulse frequency is between 1000Hz-50000 Hz.

Example 1

In this example, a large billet of rare earth steel was continuously cast as an experimental subject. The main components of the cast steel grade are shown in the following table 1, and rare earth cerium with the rare earth content of 0.1 percent is fed.

TABLE 1 Steel species main Components

Element(s)	C	Si	Mn	P	S
						Content (%)	0.95-1.05	0.15-0.30	0.25-0.45	≤0.015	≤0.002

In the experimental process, an aluminum-carbon submerged nozzle with serious nodulation in the original casting process is selected as a regulating object. Firstly, grooving the outer wall of a formed submerged nozzle, wherein the grooving mode is that uniform symmetrical grooving is carried out from the position below 10cm of the top of the nozzle to the position above a nozzle slag line, then a lead is embedded, the lead is made of molybdenum, the embedding depth of the lead is 1.0cm away from the outer wall of the nozzle, the diameter of the high-temperature lead is 1.5mm, and then a groove is sealed by a carbon-containing high-temperature adhesive and then is wrapped by refractory cotton for sealing. And then, the embedded wire on the water gap is fixedly connected with one section of the extension wire, and the other end of the extension wire is connected with the anode of the power supply. The negative pole of the power supply is connected with the zirconium carbon refractory bar through an extension lead. The epitaxial lead is an iron metal lead, the diameter of the zirconium-carbon refractory rod is 4cm, the content of zirconium oxide in the zirconium-carbon refractory rod is 72.35%, and the content of graphite in the zirconium-carbon refractory rod is 25.01%. And after the connection is finished, carrying out online preheating baking on the connected water gap. And when the continuous casting starts, vertically inserting the zirconium-carbon refractory bar into the molten steel in the crystallizer so as to form a complete closed loop between the zirconium-carbon refractory bar and the water gap. Wherein the insertion depth of the zirconium carbon refractory material rod exceeds the covering slag and is inserted into the molten steel for 5 cm. And in the casting process, a stable positive pulse electric field is applied to the inner wall of the nozzle to prevent the nozzle from decarbonizing and reacting. The output voltage of the pulse electric field is 15V, the pulse frequency is 15000Hz, and the output current is 50A.

No abnormality occurs in the casting process. And after the casting is finished, taking out the water gap for sampling and observing. The inner wall of the water gap is relatively compact and smooth, and the obvious water gap nodulation phenomenon does not occur inside the water gap. And no quality problem is found in the quality detection of the casting blank.

Example 2

In this embodiment, a certain square billet of rare earth stainless steel is continuously cast as an experimental object. The main components of the cast steel grade are shown in the following table 2, and rare earth cerium with the rare earth content of 0.2 percent is fed.

TABLE 2 Steel species main Components

Element(s)

C

Si

Mn

P

S

Cr

Content (%)

0.15-0.25

0.60-0.70

0.35-0.40

≤0.02

≤0.02

12.5-13.0

In the experimental process, an aluminum zirconium carbon long nozzle with serious nodulation in the original casting process is selected as a regulating object. Firstly, when the water gap is produced, the conducting wire is uniformly inserted in advance, and after the water gap is pressed and formed, a special water gap with the embedded conducting wire is directly obtained. Wherein the wire material is molybdenum, and the embedding degree of depth of wire should be apart from mouth of a river outer wall 1.3cm, and the high temperature wire diameter is 2 mm. And then, the embedded wire on the water gap is fixedly connected with one section of the extension wire, and the other end of the extension wire is connected with the anode of the power supply. The negative pole of the power supply is connected with the zirconium carbon refractory bar through an extension lead. Wherein the extension lead is an iron metal lead, the diameter of the zirconium carbon refractory rod is 5cm, the content of zirconium oxide in the zirconium carbon refractory rod is 75%, and the content of graphite is 22.37%. And after the connection is finished, carrying out online preheating baking on the connected water gap. And when the continuous casting starts, vertically inserting the zirconium-carbon refractory bar into the molten steel in the tundish to form a complete closed loop with the nozzle. Wherein the insertion depth of the zirconium carbon refractory material rod exceeds the covering slag and is inserted into the molten steel for 6.5 cm. And in the casting process, a stable positive pulse electric field is applied to the inner wall of the nozzle to prevent the nozzle from decarbonizing and reacting. The output voltage of the pulse electric field is 25V, the pulse frequency is 20000Hz, and the output current is 100A.

No abnormality occurs in the casting process. And after the casting is finished, taking out the water gap for sampling and observing. The inner wall of the water gap is relatively compact and smooth, and the obvious water gap nodulation phenomenon does not occur inside the water gap. And no quality problem is found in the quality detection of the casting blank.

Example 3

In this example, a slab of rare earth steel was continuously cast as an experimental subject. The main components of the cast steel grade are shown in the following table 3, and rare earth cerium with the rare earth content of 0.075% is fed.

TABLE 3 Steel species main Components

Element(s)	C	Si	Mn	P	S
						Content (%)	0.15-0.25	0.35-0.45	1.80-1.90	≤0.03	≤0.02

In the experimental process, an aluminum-carbon submerged nozzle with serious nodulation in the original casting process is selected as a regulating object. Firstly, carrying out slotting treatment on the outer wall of a formed submerged nozzle, wherein the slotting mode is that conducting uniform symmetrical slotting from the position below 10cm of the top of the nozzle to the position above a nozzle slag line and then embedding a lead, the lead is made of molybdenum, the embedding depth of the lead is 0.8cm away from the outer wall of the nozzle, and the diameter of the high-temperature lead is 2 mm. Then the groove is sealed by carbon-containing high-temperature binder, and then is wrapped by refractory cotton for sealing. And then, the embedded wire on the water gap is fixedly connected with one section of the extension wire, and the other end of the extension wire is connected with the anode of the power supply. The negative pole of the power supply is connected with the zirconium carbon refractory bar through an extension lead. The epitaxial lead is an iron metal lead, the diameter of the zirconium-carbon refractory rod is 3.5cm, the content of zirconium oxide in the zirconium-carbon refractory rod is 73.11%, and the content of graphite in the zirconium-carbon refractory rod is 23.88%. And after the connection is finished, carrying out online preheating baking on the connected water gap. And when the continuous casting starts, vertically inserting the zirconium-carbon refractory bar into the molten steel in the crystallizer so as to form a complete closed loop between the zirconium-carbon refractory bar and the water gap. Wherein the insertion depth of the zirconium carbon refractory material rod exceeds the covering slag and is inserted into the molten steel by 5.5 cm. And in the casting process, a stable positive direct current electric field is applied to the inner wall of the nozzle, so that the nozzle is prevented from decarbonizing and reacting. The output voltage of the DC electric field is 30V, and the output current is 115A.

No abnormality occurs in the casting process. And after the casting is finished, taking out the water gap for sampling and observing. The inner wall of the water gap is relatively compact and smooth, and the obvious water gap nodulation phenomenon does not occur inside the water gap. And no quality problem is found in the quality detection of the casting blank.