Carbon deoxidation process for RH cold-rolled base material

Abstract

The invention discloses an RH cold-rolled base material carbon deoxidation process which comprises the following steps: starting natural reaction between free oxygen in molten steel and carbon in the molten steel by adopting vacuum treatment, adding high-carbon ferromanganese in the middle and later periods of RH decarburization and after the initial carbon-oxygen reaction is finished, increasing the gas flow by 300-500NL / min, carrying out circulation for 2-4 minutes, then determining oxygen, and carrying out deoxidation according to the residual oxygen value; and deoxidation alloying is conducted according to the final decarburization residual oxygen value. According to the process, the carbon-oxygen reaction is fully utilized in the RH treatment process, the molten steel deoxidation treatment is not performed by purely adopting aluminum particles or a deoxidizing agent, and the molten steel heating treatment is performed by utilizing the aluminum-oxygen reaction, so that the use amount of the aluminum particles or the deoxidizing agent and the alloy can be effectively reduced, and the smelting cost of the low-carbon steel is reduced; and by optimizing the process, the content of inclusions in the molten steel can be reduced, and the purity of the molten steel is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and in particular relates to a RH cold-rolled base material carbon deoxidation process. Background Art

[0002] The RH furnace produces cold-rolled base material according to the characteristics of low-carbon, low-silicon, aluminum-killed steel. The converter endpoint uses low-carbon, high-oxygen steelmaking (converter endpoint target oxygen 400-800ppm, endpoint carbon ≤0.06%). The RH furnace often has excess oxygen. The conventional process uses the "aluminum deoxidation" process. The deoxidation product is solid Al2O3. After deoxidation, medium-carbon ferromanganese is used for alloying. The RH excess oxygen is completely deoxidized by aluminum, which is bound to produce a large amount of Al2O3, increasing the residual amount of aluminum inclusions in the molten steel. The residual aluminum inclusions gather in the molten steel to form chain inclusions, affecting the purity and castability of the molten steel, as well as the quality of the rolled material, and the cost is relatively high. Summary of the invention

[0003] In order to overcome the defects of the above-mentioned prior art, the present invention reduces the consumption of aluminum alloys, improves the quality of ingots, reduces the alloy consumption cost; further improves the purity of molten steel and enhances product quality.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides a RH cold-rolled base material carbon deoxidation process, and the process of producing the cold-rolled base material in the RH furnace comprises the following steps:

[0005] ① At the beginning of vacuum treatment, the free oxygen in the molten steel reacts naturally with the carbon content in the molten steel. In the early stage of vacuum decarburization, the free oxygen in the molten steel reacts naturally with the carbon in the molten steel to reduce the free oxygen content. The free oxygen content is 50-500ppm.

[0006] ② In the middle and late stages of RH decarburization, high carbon ferromanganese is added after the initial carbon-oxygen violent reaction is completed to avoid splashing in the vacuum chamber caused by the intensified carbon-oxygen reaction in the early stage. The carbon content of the high carbon ferromanganese is 6% to 7%. After the initial carbon-oxygen reaction is completed, the amount of high carbon ferromanganese added is determined according to the steel grade composition requirements.

[0007] ③ After adding high carbon ferromanganese, increase the lifting gas flow rate by 300-500NL / min, increase the circulation rate of molten steel, improve the decarburization effect, determine the oxygen after circulating for 2-4 minutes, and deoxidize according to the residual oxygen value. After adding high carbon ferromanganese, increase the dynamic conditions of molten steel under vacuum conditions to increase the gas flow rate and increase the carbon-oxygen reaction rate. The lifting gas flow rate is preferably 350-450NL / min. When the residual oxygen value is 50-150ppm, add 20-60kg of high carbon ferromanganese; when the residual oxygen value is greater than 150ppm, add 40-80kg of high carbon ferromanganese.

[0008] ④ Deoxidation and alloying are carried out according to the final decarburization residual oxygen value, and the target temperature at the end of RH treatment is controlled to be 1540℃~1650℃.

[0009] In the RH treatment process, the carbon-oxygen reaction is fully utilized, not just the simple use of aluminum particles or deoxidizers to deoxidize the molten steel and the aluminum-oxygen reaction to heat the molten steel. This can effectively reduce the use of aluminum particles or deoxidizers and alloys, and reduce the smelting cost of low-carbon steel. By optimizing the process, the inclusion content in the molten steel can also be reduced, and the purity of the molten steel can be improved.

[0010] According to the thermodynamic equation of carbon-oxygen reaction:

[0011] [C]+[O]={CO}(△G0=-25-0.0379T kJ / mol)

[0012] Among them, the reaction equilibrium constant K = PCO / (fC×WC×fO×WO); when smelting low-carbon steel, the concentration of carbon and oxygen in the molten steel is reduced to a very small level, then fC and fO can be regarded as 1, and the formula becomes: K = PCO / (WC×WO); when the temperature remains unchanged, K is a constant. If PCO is a constant, then the product of WC and WO is also a constant. This shows that when the molten steel circulates in the RH vacuum chamber, the carbon in the molten steel reacts with free oxygen to produce a carbon-oxygen reaction, and the ability of the carbon-oxygen reaction increases with the increase of the vacuum degree. Therefore, the deoxidation ability of carbon in RH exceeds that of aluminum, and the generated CO is discharged with the exhaust gas, which greatly reduces the inclusion amount of Al2O3, improves the purity of the molten steel, and reduces the cost. If carbon particles are used alone for deoxidation under vacuum, the carbon-oxygen reaction under low vacuum is very violent, and splashing accidents are prone to occur.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] In order to reduce the splashing accidents caused by carbon-oxygen reaction, the present invention adopts the method of adding high carbon ferromanganese in the middle and late stages of RH decarburization, making full use of the carbon content in high carbon ferromanganese for deoxidation, which can effectively reduce the residual oxygen content after decarburization. There is a certain price difference between high carbon ferromanganese and medium carbon ferromanganese, and the consumption of deoxidized aluminum is reduced, while the alloy cost is reduced. The "carbon deoxidation" process makes the operation simple and stable, and the technical effect is remarkable; the total amount of Al2O3 inclusions is significantly reduced, the purity of molten steel is improved, and the castability is significantly improved, ensuring the continuity of production. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0016] Example

[0017] A RH cold-rolled base material carbon deoxidation process, the specific process flow is:

[0018] ① At the beginning of vacuum treatment, the free oxygen in the molten steel reacts naturally with the carbon in the molten steel; the free oxygen content is 100ppm.

[0019] ② In the middle and late stages of RH decarburization, high carbon ferromanganese is added after the initial carbon-oxygen reaction is completed; the carbon content of the high carbon ferromanganese is 6.5%;

[0020] ③ After adding high carbon ferromanganese, increase the lifting gas flow rate to 400NL / min, circulate for 3 minutes, determine the oxygen, and deoxygenate according to the residual oxygen value; if the residual oxygen value is 85ppm, add 40kg of high carbon ferromanganese.

[0021] ④ Deoxidation and alloying are carried out according to the final decarburization residual oxygen value, and the target temperature at the end of RH treatment is controlled to 1580℃.

[0022] In the embodiment, an average of 264 kg of high carbon ferromanganese is used per furnace, wherein the carbon content is 6.5%, the pure carbon content is 17.2 kg, 126 ppm of deoxidation can be achieved, the deoxidation aluminum consumption is reduced by 31.5 kg, and the cost can be reduced by 3.58 yuan / ton of steel; the price of medium carbon ferromanganese is 8557.31 yuan / ton, and the price of high carbon ferromanganese is 6853.91 yuan / ton. The use of 264 kg of high carbon ferromanganese can reduce the alloy cost by 0.9 yuan / ton of steel; the economic benefit is remarkable.

[0023] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A RH cold-rolled base material carbon deoxidation process, characterized in that: The process comprises the following steps: ① The vacuum treatment begins, using the natural reaction between free oxygen in the molten steel and carbon in the molten steel; ② In the middle and late stages of RH decarburization, high carbon ferromanganese is added after the initial carbon-oxygen reaction is completed; ③ After adding high carbon ferromanganese, increase the lifting gas flow rate to 300-500NL / min, circulate for 2-4 minutes, determine the oxygen, and deoxygenate according to the residual oxygen value; ④ Carry out deoxidation alloying according to the final decarburization residual oxygen value.

2. The process according to claim 1, characterized in that The free oxygen content in step ① is 50 to 500 ppm.

3. The process according to claim 1, characterized in that The carbon content of the high carbon ferromanganese in step ② is 6% to 7%.

4. The process according to claim 1, characterized in that The lifting gas flow rate in step ③ is 350-450 NL / min.

5. The process according to claim 1, characterized in that In step ③, when the residual oxygen value is 50-150 ppm, 20-60 kg of high carbon ferromanganese is added; when the residual oxygen value is greater than 150 ppm, 40-80 kg of high carbon ferromanganese is added.

6. The process according to claim 1, characterized in that The target temperature at the end of the RH treatment is controlled to be 1540°C to 1650°C.