A carbon-aluminum composite deoxidizer and its preparation method and method for producing low-carbon or ultra-low-carbon steel

Abstract

The invention discloses a method for preparing a carbon-aluminum composite deoxidizer under vacuum and producing low-carbon or ultra-low-carbon steel with the composite deoxidizer, and belongs to the field of steel manufacturing technology. The preparation comprises combining carbon powder and aluminum powder in proportion with a viscous material binder, mixing and stirring, pressing into pellets, and drying to obtain a carbon-aluminum ball composite deoxidizer. The use method comprises adding a carbon-aluminum ball composite deoxidizer to react with oxygen in molten steel to form carbon monoxide gas and aluminum oxide when an RH vacuum refining device is producing low-carbon or ultra-low-carbon steel. When an RH vacuum refining device is producing low-carbon or ultra-low-carbon steel, the residual oxygen in the steel is generally 0.03%, and the deoxidizing material is added accordingly. Under vacuum conditions, the reaction of carbon and oxygen has a gaseous product, and the limiting factor of the reaction is closely related to the partial pressure of the gas except for the temperature. The reaction follows the partial pressure law, and the reaction proceeds toward a positive reaction. Therefore, the carbon-oxygen reaction under vacuum conditions is used to remove part of the oxygen in the steel, reduce the total amount of deoxidized inclusion products by 45-55wt.%, and improve the quality of the molten steel.

Description

Technical Field

[0001] The invention relates to the field of steel manufacturing technology, in particular to a carbon-aluminum composite deoxidizer and a preparation method thereof and a method for producing low-carbon or ultra-low-carbon steel. Technical Background

[0002] In the steel industry, there are three types of deoxidation in the steelmaking process: precipitation deoxidation, diffusion deoxidation, and vacuum deoxidation. With the requirements of production efficiency and high efficiency of production capacity, a large number of steel companies are increasingly using precipitation deoxidation. Due to the deoxidation effect and efficiency of aluminum, most steel mills use aluminum as the main deoxidation material, but its deoxidation product, aluminum oxide, is a high-melting-point particle and is widely present in steel as an inclusion, affecting the purity of the steel. Its removal and modification have always been the main concerns of the industry.

[0003] The deoxidation efficiency of carbon is 0.0075%, which can remove 0.01% of free oxygen in steel. Its product is carbon monoxide, which is in gaseous state under the working conditions of steelmaking. It is discharged with the vacuum system and does not pollute the molten steel. It has no effect on the steel quality. The deoxidation efficiency of aluminum is 0.0113%. Aluminum can remove 0.01% of free oxygen in steel. Its product is aluminum oxide. Its high melting point characteristic leads to the existence of inclusions in the steel. It is the main factor affecting the cleanliness of molten steel and is also a problem of particular concern in the steelmaking process. Summary of the invention

[0004] A new composite deoxidizer and method are invented to improve the conventional single aluminum deoxidation process, and utilize the carbon deoxidation ability under vacuum conditions and the characteristics of not polluting molten steel to reduce the inclusion content of aluminum deoxidation.

[0005] The present invention provides a carbon-aluminum ball composite deoxidizer, which is a spherical composite material, and the composite deoxidizer is a pellet with a particle size of 30 to 60 mm; wherein, by weight percentage, the composite deoxidizer comprises 36% to 42% of carbon; 56% to 62% of aluminum; and 1.5% to 2% of an adhesive material binder; and the sum of the weight percentages of carbon, aluminum and the adhesive material binder in the composite deoxidizer is 100%.

[0006] Furthermore, the above technical solution includes the following steps: carbon powder and aluminum powder are mixed in proportion with a viscous material binder, stirred evenly, pressed into pellets of the particle size specification, and the pellets are dried to obtain a carbon-aluminum ball composite deoxidizer.

[0007] Furthermore, in the above technical solution, the adhesive material binder is phenolic resin.

[0008] The invention discloses a method for producing low-carbon or ultra-low-carbon steel. When the RH vacuum refining device produces low-carbon or ultra-low-carbon steel, the composite deoxidizer is added at the end of decarburization to react with oxygen in molten steel to form carbon monoxide gas and aluminum oxide, and deoxidation and alloying are started. The amount of the deoxidizer added is 0.26-3.3 kg / t to obtain the target molten steel.

[0009] Furthermore, in the above technical solution, the amount of the deoxidizer added is 0.94-2.8 kg / t.

[0010] Furthermore, in the above technical solution, the free oxygen content in the target molten steel is 0.0010-0.0030%; the Als component is 0.02-0.05wt.%; and the deoxidized inclusions are reduced by 45-55%.

[0011] Furthermore, in the above technical solution, when producing low-carbon or ultra-low-carbon steel, the vacuum degree of the RH vacuum refining device is between 90 and 110 Pa.

[0012] Furthermore, in the above technical solution, the C in the produced low carbon steel is ≤0.02wt.%; and the C in the produced ultra-low carbon steel is ≤0.0050wt.%.

[0013] Furthermore, in the above technical solution, at the end point of decarburization, the temperature of the molten steel is 1550-1750°C.

[0014] Furthermore, in the above technical solution, a carbon-aluminum composite deoxidizer is added to the molten steel, and the carbon and aluminum therein react with the free oxygen in the steel respectively, thereby ultimately achieving the purpose of deoxidizing the molten steel.

[0015] Furthermore, in the above technical solution, when the RH vacuum refining device produces low-carbon or ultra-low-carbon steel, the residual oxygen in the steel is generally 0.03%, and the deoxidizing material is added accordingly. Under vacuum conditions, the reaction of carbon and oxygen has a gaseous product, and the limiting factor of the reaction is closely related to the gas partial pressure except for the temperature. The reaction follows the partial pressure law, and the reaction proceeds towards a positive reaction. Therefore, the carbon-oxygen reaction under vacuum conditions is utilized to remove part of the oxygen in the steel, reduce the total amount of deoxidation inclusion products, and improve the quality of molten steel.

[0016] Beneficial Effects

[0017] (1) A carbon-aluminum composite deoxidizer is used with an addition amount of 0.094 kg / T, which can remove 0.01% of oxygen in the steel. For the RH vacuum refining device in the production of low-carbon or ultra-low-carbon steel, a carbon-aluminum composite deoxidizer is added during the deoxidation process at the end of decarburization to reduce the oxygen and achieve the purpose of removal. Subsequently, aluminum is used for conventional alloying and composition adjustment. Compared with the conventional precipitation deoxidation using aluminum, the total amount of deoxidation products is reduced, thereby achieving the purpose of improving the quality of molten steel.

[0018] (2) Carbon can participate in deoxidation under vacuum conditions. The ability of carbon-oxygen reaction depends on the partial pressure of the product CO. The product is a gas and does not produce solid deoxidation product inclusions, which does not pollute the molten steel. It can reduce the total amount of deoxidation inclusions in the molten steel and improve the purity of the molten steel.

[0019] Specific implementation content

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] Example 1

[0022] (1) Preparation of carbon-aluminum ball composite deoxidizer: 36 g of carbon powder and 62 g of aluminum powder are combined with 2 g of phenolic resin, mixed and stirred evenly, and pressed into pellets of the particle size specification. After the pellets are dried, 100 g of carbon-aluminum ball composite deoxidizer is obtained.

[0023] (2) Preparation method for producing ultra-low carbon steel: When using RH vacuum refining device to produce ultra-low carbon steel (C≤0.0050%), the vacuum degree of RH vacuum refining device is 100Pa, the free oxygen content in the steel is 0.03%, the temperature is 1600℃, and about 1.10kg / T of carbon aluminum ball composite deoxidizer is added during the deoxidation process at the end of decarburization, and the free oxygen content in the steel is 0.003%; then the aluminum particles in the composite deoxidizer are conventionally alloyed, and the Als content in the obtained target steel is 0.02-0.05%. At the same time, precipitation deoxidation reduces the total amount of deoxidation products by 45%, thereby achieving the purpose of improving the quality of molten steel.

[0024] Example 2

[0025] (1) Preparation of carbon-aluminum ball composite deoxidizer: 42g carbon powder and 56.5g aluminum powder are combined with 1.5g phenolic resin, mixed and stirred, and pressed into pellets of the particle size specification. After the pellets are dried, 100g of carbon-aluminum ball composite deoxidizer is obtained. (2) Preparation method for producing ultra-low carbon steel: When using RH vacuum refining device to produce ultra-low carbon steel (C≤0.0050wt.%), the vacuum degree of the RH vacuum refining device is 100Pa, the free oxygen content in the steel is 0.03%, the temperature is 1600℃, and at the end of decarburization, about 2.8kg / T of carbon-aluminum ball composite deoxidizer is added during the deoxidation process, and the free oxygen content in the steel is 0.001% at this time; then the aluminum particles in the composite deoxidizer are conventionally alloyed, and the Als content in the obtained target steel is 0.02-0.04%, and at the same time, precipitation deoxidation reduces the total amount of deoxidation products by 55%, thereby achieving the purpose of improving the quality of molten steel.

[0026] Example 3

[0027] (1) Preparation of carbon-aluminum ball composite deoxidizer: 40 g of carbon powder and 58 g of aluminum powder are combined with 2 g of phenolic resin, mixed and stirred evenly, and pressed into pellets of the particle size specification. After the pellets are dried, 100 g of carbon-aluminum ball composite deoxidizer is obtained.

[0028] (2) Preparation method for producing ultra-low carbon steel: When an RH vacuum refining device is used to produce ultra-low carbon steel (C≤0.0050wt.%), the vacuum degree of the RH vacuum refining device is 100Pa, the free oxygen content in the steel is 0.03%, and the temperature is 1600°C. At the end of decarburization, about 3.0kg / T of carbon-aluminum ball composite deoxidizer is added during the deoxidation process, and the free oxygen content in the steel is 0.001% at this time; then the aluminum particles in the composite deoxidizer are conventionally alloyed, and the Als content in the obtained target steel is 0.02-0.04%. At the same time, precipitation deoxidation reduces the total amount of deoxidation products by 50%, thereby achieving the purpose of improving the quality of molten steel.

Claims

1. A method for preparing low carbon or ultra-low carbon steel, characterized in that: When low carbon or ultra-low carbon steel is produced by RH vacuum refining device, a composite deoxidizer is added at the end of decarburization to perform deoxidation and alloying; the amount of the deoxidizer added is 0.26-3.3 kg / t to obtain the target molten steel; The composite deoxidizer is a carbon-aluminum composite deoxidizer, and the composite deoxidizer is a spherical composite ball; the composite deoxidizer is a pellet with a particle size of 30 to 60 mm; wherein, by weight percentage, the composite deoxidizer includes 36 to 42% carbon, 56 to 62% aluminum, and 1.5 to 2% adhesive material binder; The preparation method of the carbon-aluminum composite deoxidizer comprises the following steps: combining carbon powder and aluminum powder with a viscous material binder, mixing and stirring, and evenly pressing into pellets of the particle size specification, and drying the pellets to obtain a carbon-aluminum ball composite deoxidizer; The adhesive material binder is phenolic resin.

2. The method for preparing low carbon or ultra-low carbon steel according to claim 1, characterized in that: The free oxygen content in the target molten steel is 0.0010-0.0030%; the deoxidized inclusions are reduced by 45-55wt.%.

3. The method for preparing low carbon or ultra-low carbon steel according to claim 1, characterized in that: When producing low carbon steel or ultra-low carbon steel, the vacuum degree of the RH vacuum refining device is 90-110Pa.

4. The method for preparing low carbon or ultra-low carbon steel according to claim 1, characterized in that: In the low carbon steel, C is ≤0.02wt.% by weight; in the ultra-low carbon steel, C is ≤0.0050wt.% by weight.

5. The method for preparing low carbon or ultra-low carbon steel according to claim 1, characterized in that: At the end point of decarburization, the temperature of the molten steel is 1550-1750°C.