Production method for reducing and dephosphorizing refined deoxidized alloyed molten steel

Abstract

The invention discloses a production method for reducing and dephosphorizing refined and deoxidized alloyed molten steel. The production method comprises the steps of refining and slagging, refining and deoxidizing and controlling a vacuum process. A slag former for refining and slagging is calcium fluoride, a refining and deoxidizing agent for refining and deoxidizing is calcium carbide and aluminum, and in the vacuum process, a calcium core wire is added before vacuum, so that the high argon intensity retention time of which the vacuum degree is 0.3-0.5 MPa below 66Pa is prolonged. According to the method provided by the invention, the dephosphorization effect is achieved by promoting free phosphorus in the molten steel to be converted into phosphide inclusions and removing the phosphide inclusions by means of argon stirring flotation. The operation method is convenient and effective, the problem that the phosphorus element exceeds the standard in the production process can be solved with low cost, the method is particularly beneficial to production of steel with standard phosphorus being 0.015% or below, and the problem that phosphorus exceeds the standard due to rephosphorization or alloy phosphorus expansion in the refining process is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of clean steel production, and in particular relates to a production method for reducing and dephosphorizing refined deoxidized alloyed steel liquid. Background Art

[0002] During the steelmaking process, uncontrolled slag discharge or alloying additions in electric arc furnaces and converters can cause the phosphorus content in the molten steel to exceed standard requirements. Traditional production methods, operating under the conditions of low oxygen content and a strongly reducing atmosphere in the refined steel, are unable to achieve effective dephosphorization. This can only be addressed by changing the steel grade or remelting the steel, which is not only extremely costly but also severely impacts production. Reduction dephosphorization during refined, deoxidized, and alloyed steel is the only way to address this issue. Summary of the Invention

[0003] The present invention provides a production method for reduction dephosphorization of refined deoxidized alloyed steel liquid. By controlling the refining slag making, refining deoxidation and vacuum processes, the problem of excessive phosphorus caused by refining and phosphorus regeneration is effectively controlled at a relatively low cost.

[0004] In order to solve the above method problems, the method scheme adopted by the present invention is: A production method for reducing and dephosphorizing refined, deoxidized, alloyed molten steel includes refining and slagging, refining and deoxidation, and vacuum process control to promote the chemical reaction between calcium and phosphorus in the molten steel to form calcium phosphide inclusions that can float and be removed.

[0005] Preferably, the slagging agent used for refining slag is calcium fluoride.

[0006] Preferably, the refining deoxidizers used in the refining deoxidation are calcium carbide and aluminum.

[0007] Preferably, in the vacuum process, calcium core wire is added before vacuuming, and the high argon gas intensity holding time of 0.3-0.5 MPa of vacuum degree below 66 Pa is prolonged.

[0008] Preferably, calcium fluoride is added in an amount of 2.5-3.0 kg / ton of steel. The controlled refining slag-forming agent of the present invention, wherein calcium fluoride is added in an amount of 2.5-3.0 kg / ton of steel, can substantially improve the fluidity of the refining slag, effectively reduce the vapor pressure of calcium, and increase the reaction rate of calcium and phosphorus by 15-20%.

[0009] Preferably, calcium carbide is added in an amount of 2.5-3.0 kg / ton of steel to make the slag foaming index between 0.8 and 1.2.

[0010] Preferably, aluminum is added in an amount of 2.0-2.5 kg per ton of steel. The controlled refining deoxidizer of the present invention uses aluminum and calcium carbide as the main deoxidizers in the refining process. Adding aluminum at 2.0-2.5 kg per ton of steel allows for sufficient deep deoxidation and forms aluminum oxide, which increases the surface tension of the slag, thereby increasing the contact area between steel and slag. Adding calcium carbide at 2.5-3.0 kg per ton of steel allows for a slag foaming index of around 1.0, thereby creating a favorable reducing atmosphere and increasing the activity of calcium atoms. This operation can increase the probability of calcium-phosphorus reaction by 15-20%.

[0011] Preferably, 0.5-0.6 kg / ton of calcium core wire is added before vacuuming to increase the calcium content of the molten steel by 0.0015-0.002%.

[0012] Preferably, the high argon gas intensity holding time at a vacuum degree of 0.3-0.5 MPa below 66 Pa is extended to 12-15 minutes.

[0013] The controlled vacuum process of the present invention involves adding 0.5 to 0.6 kg of calcium core wire per ton of steel before vacuum, increasing the calcium content of the molten steel by 0.0015 to 0.002%, promoting an increase in the number of calcium-phosphorus reactions. The high argon gas intensity hold time of 0.3 to 0.5 MPa, at a vacuum level below 66 Pa, is extended to 12 to 15 minutes, providing favorable kinetic conditions and ample time for the calcium-phosphorus reaction. This operation can increase the probability of the calcium-phosphorus reaction by 35 to 45%.

[0014] Preferably, 15 to 30% by mass of phosphorus is removed from the refined, deoxidized and alloyed molten steel.

[0015] The beneficial effects of adopting the above control method are: The method provided by the present invention achieves dephosphorization by promoting the conversion of free phosphorus in molten steel into phosphide inclusions, which are then removed by argon agitation and flotation. This method is convenient and effective, and can solve the problem of excessive phosphorus in the production process at a low cost. It is particularly beneficial for the production of steel grades with a standard phosphorus content below 0.015%, and solves the problem of excessive phosphorus caused by phosphorus resorption during the refining process or phosphorus expansion in alloys. Specifically, it has the following four points: Using calcium fluoride as a slag-forming agent for refining slag is low-cost and can quickly improve the fluidity of the refining slag and reduce the vapor pressure of calcium, thereby promoting the reduction and dephosphorization reaction, quickly desulfurizing and removing inclusions, and improving the cleanliness of the molten steel.

[0016] Aluminum and calcium carbide are selected as the main deoxidizers in the refining process to increase the surface tension of the refining slag, improve the foaming index of the refining slag and the activity of calcium atoms, which can promote the reduction and dephosphorization reaction, and ensure good deoxidation and inclusion removal conditions and reducing atmosphere for the molten steel, which has an excellent effect on improving the cleanliness of the molten steel.

[0017] Adding calcium core wire before vacuum and extending the high argon intensity holding time of 0.3~0.5MPa below 66Pa can promote the reduction dephosphorization reaction, deform inclusions, improve the degassing effect, and greatly promote the cleanliness of molten steel.

[0018] After the refining, deoxidation and alloying, the dephosphorization success rate of the heats produced by the present invention is 100% for the phosphorus content exceeding the standard requirement by less than 0.005% due to phosphorus increase; the dephosphorization success rate is over 80% for the heats exceeding the standard requirement by less than 0.008% due to phosphorus increase; and the proportion of steel modification and remelting due to excessive phosphorus content is reduced by over 95%. DETAILED DESCRIPTION Example 1

[0019] In this embodiment, 30 steel plates with a standard phosphorus content of ≤0.015-0.018% and a phosphorus content of 0.020% after refining, deoxidation, and alloying are produced, and the weight of molten steel is 100 tons. The control method includes adding calcium fluoride at a rate of 2.5-3.0 kg / ton of steel during the refining and slag-making process, adding aluminum at a rate of 2.0-2.5 kg / ton of steel and calcium carbide at a rate of 2.5-3.0 kg / ton of steel during the refining and deoxidation process, adding calcium core wire at a rate of 0.5-0.6 kg / ton of steel before vacuuming, and extending the high-intensity argon gas holding time of 0.3-0.5 MPa below 66 Pa to 12-15 minutes. The details are as follows: Add 300kg of calcium fluoride; Add 200kg of aluminum wire and 300kg of calcium carbide; Before vacuuming, add 60kg of calcium core wire and maintain the high argon intensity of 0.45MPa below 66Pa for 12min.

[0020] The steel plate produced by the production method of this embodiment has a phosphorus content of 0.015% after rolling, a reduction dephosphorization content of 0.005%, and a dephosphorization ratio of 25%. Example 2

[0021] In this embodiment, 30 steel plates with a standard phosphorus content of ≤0.020% and a phosphorus content of 0.024% after refining, deoxidation, and alloying, and a molten steel weight of 105 tons were produced. The control method includes adding calcium fluoride at a rate of 2.5-3.0 kg / ton of steel during the refining and slag-making process, adding aluminum at a rate of 2.0-2.5 kg / ton of steel and calcium carbide at a rate of 2.5-3.0 kg / ton of steel during the refining and deoxidation process, adding calcium core wire at a rate of 0.5-0.6 kg / ton of steel before vacuuming, and extending the high argon gas intensity holding time of 0.3-0.5 MPa below 66 Pa to 12-15 minutes. The details are as follows: (1) Add 280 kg of calcium fluoride; (2) Add 230kg of aluminum wire and 310kg of calcium carbide; (3) Before vacuuming, add 65kg of calcium core wire and maintain the high argon intensity of 0.48MPa below 66Pa for 15min.

[0022] The steel plate produced by the production method of this embodiment has a phosphorus content of 0.020% after rolling, a reduction dephosphorization content of 0.004%, and a dephosphorization ratio of 17%. Example 3

[0023] In this embodiment, 40 steel plates with a standard phosphorus content of ≤0.015% and a phosphorus content of 0.022% after refining, deoxidation, and alloying, and a molten steel weight of 110 tons are produced. The control method includes adding calcium fluoride at a rate of 2.5-3.0 kg / ton of steel during the refining and slag-making process, adding aluminum at a rate of 2.0-2.5 kg / ton of steel and calcium carbide at a rate of 2.5-3.0 kg / ton of steel during the refining and deoxidation process, adding calcium core wire at a rate of 0.5-0.6 kg / ton of steel before vacuuming, and extending the high argon gas intensity holding time of 0.3-0.5 MPa below 66 Pa to 12-15 minutes. The details are as follows: (1) Add 320 kg of calcium fluoride; (2) Add 260kg of aluminum wire and 330kg of calcium carbide; (3) Before vacuuming, add 70kg of calcium core wire and maintain the high argon intensity of 0.5MPa below 66Pa for 15min.

[0024] After the steel plates were rolled using the production method of this embodiment, phosphorus analysis of 33 finished products was 0.015%, phosphorus analysis of 7 finished products was 0.016-0.018%, the reduction dephosphorization amount was 0.005-0.007%, and the average dephosphorization ratio was 30%. Example 4

[0025] In this embodiment, 38 steel plates with a standard phosphorus content of ≤0.025% and a phosphorus content of 0.027% after refining, deoxidation, and alloying, and 108 tons of molten steel are produced. The control method includes adding calcium fluoride at a rate of 2.5-3.0 kg / ton of steel during the refining and slag-making process, adding aluminum at a rate of 2.0-2.5 kg / ton of steel and calcium carbide at a rate of 2.5-3.0 kg / ton of steel during the refining and deoxidation process, adding calcium core wire at a rate of 0.5-0.6 kg / ton of steel before vacuuming, and extending the high-intensity argon gas holding time of 0.3-0.5 MPa below 66 Pa to 12-15 minutes. The details are as follows: (1) Add 290 kg of calcium fluoride; (2) Add 230kg of aluminum wire and 280kg of calcium carbide; (3) Before vacuuming, add 63kg of calcium core wire and maintain the high argon gas intensity of 0.3MPa below 66Pa for 15min.

[0026] After the steel plates were rolled using the production method of this embodiment, the phosphorus analysis of the finished products met the standard requirements, the reduction dephosphorization amount was 0.004%, and the dephosphorization ratio was 15%. Example 5

[0027] In this embodiment, 28 steel plates with a standard phosphorus content of ≤0.015% and a phosphorus content of 0.017% after refining, deoxidation, and alloying, and 105 tons of molten steel are produced. The control method includes adding calcium fluoride at a rate of 2.5-3.0 kg / ton of steel during the refining and slagging process, adding aluminum at a rate of 2.0-2.5 kg / ton of steel and calcium carbide at a rate of 2.5-3.0 kg / ton of steel during the refining and deoxidation process, adding calcium core wire at a rate of 0.5-0.6 kg / ton of steel before vacuuming, and extending the high argon gas intensity holding time of 0.3-0.5 MPa below 66 Pa to 12-15 minutes. The details are as follows: (1) Add 270 kg of calcium fluoride; (2) Add 240kg of aluminum wire and 290kg of calcium carbide; (3) Before vacuuming, add 60kg of calcium core wire and maintain the high argon gas intensity of 0.5MPa below 66Pa for 14min.

[0028] The phosphorus analysis of the steel plate after rolling produced by the production method of this embodiment meets the standard requirements, the reduction dephosphorization amount is 0.003%, and the dephosphorization ratio is 18%. Example 6

[0029] In this embodiment, 23 steel plates with a standard phosphorus content of ≤0.015% and a phosphorus content of 0.016% after refining, deoxidation, and alloying were produced, and the weight of the molten steel was 98 tons. The control method included adding calcium fluoride at a rate of 2.5-3.0 kg / ton of steel during the refining and slag-making process, adding aluminum at a rate of 2.0-2.5 kg / ton of steel and calcium carbide at a rate of 2.5-3.0 kg / ton of steel during the refining and deoxidation process, adding calcium core wire at a rate of 0.5-0.6 kg / ton of steel before vacuuming, and extending the high-intensity argon gas holding time of 0.3-0.5 MPa below 66 Pa to 12-15 minutes. The details are as follows: (1) Add 260 kg of calcium fluoride; (2) Add 220kg of aluminum wire and 290kg of calcium carbide; (3) Before vacuuming, add 60kg of calcium core wire and maintain the high argon gas intensity of 0.5MPa below 66Pa for 12min.

[0030] After the steel plates were rolled using the production method of this embodiment, the phosphorus analysis of the finished products met the standard requirements, the reduction dephosphorization amount was 0.004%, and the dephosphorization ratio was 25%.

[0031] Comparative Example 1 The difference between this comparative example and Example 1 is that the slagging agent used for refining slag is calcium oxide, and other conditions are the same.

[0032] The phosphorus content of the steel plate after rolling produced by the comparative example production method does not meet the standard requirements, the reduction dephosphorization amount is 0%, and the dephosphorization ratio is 0%.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is that the refining deoxidizers are carbon powder and aluminum, and other conditions are the same.

[0034] The phosphorus content of the steel plate after rolling produced by the comparative example production method does not meet the standard requirements, the reduction dephosphorization amount is 0%, and the dephosphorization ratio is 0%.

[0035] Comparative Example 3 The difference between this comparative example and Example 1 is that the refining deoxidizers are calcium carbide and ferrosilicon powder, and other conditions are the same.

[0036] The phosphorus content of the steel plate after rolling produced by the comparative example production method does not meet the standard requirements, the reduction dephosphorization amount is 0%, and the dephosphorization ratio is 0%.

[0037] Comparative Example 4 The difference between this comparative example and Example 1 is that no calcium core wire is added before vacuum, and other conditions are the same.

[0038] The phosphorus content of the steel plate after rolling produced by the comparative example production method does not meet the standard requirements, the reduction dephosphorization amount is 0.001%, and the dephosphorization ratio is 5%.

[0039] Comparative Example 5 The difference between this comparative example and Example 1 is that the high argon gas intensity of 0.5 MPa and vacuum degree below 66 Pa is maintained for 10 minutes, and other conditions are the same.

[0040] The phosphorus content of the steel plate after rolling produced by the comparative example production method does not meet the standard requirements, the reduction dephosphorization amount is 0.002%, and the dephosphorization ratio is 11%.

[0041] The above embodiments are only used to illustrate rather than limit the method scheme of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary method personnel in this field should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A production method for reducing and dephosphorizing refined deoxidized alloyed steel liquid, characterized in that: Including the control of refining slag making, refining deoxidation and vacuum process.

2. The method for reducing and dephosphorizing refined deoxidized alloyed steel according to claim 1, wherein: The slagging agent used for refining slag is calcium fluoride.

3. The method for reducing and dephosphorizing refined deoxidized alloyed steel according to claim 1, wherein: The refining deoxidizers used in the refining deoxidation are calcium carbide and aluminum.

4. The method for reducing and dephosphorizing refined deoxidized alloyed molten steel according to claim 1, wherein: The vacuum process includes adding a calcium core wire before vacuuming and prolonging the high argon gas intensity holding time of the vacuum degree below 66 Pa to 0.3-0.5 MPa.

5. The method for reducing and dephosphorizing refined deoxidized alloyed steel according to claim 2, wherein: The amount of calcium fluoride added is 2.5~3.0kg / ton of steel.

6. The method for reducing and dephosphorizing refined deoxidized alloyed steel according to claim 3, wherein: The amount of calcium carbide added is 2.5~3.0kg / ton of steel, so that the slag foaming index is 0.8~1.

2.

7. The method for reducing and dephosphorizing refined deoxidized alloyed steel according to claim 3, wherein: The amount of aluminum added is 2.0~2.5kg / ton of steel.

8. The method for reducing and dephosphorizing refined deoxidized alloyed molten steel according to claim 4, characterized in that: Before vacuuming, add 0.5~0.6kg / ton of calcium core wire to increase the calcium content of the molten steel by 0.0015~0.002%.

9. The method for reducing and dephosphorizing refined deoxidized alloyed molten steel according to claim 4, characterized in that: Extend the high argon gas intensity holding time of 0.3~0.5MPa at vacuum degree below 66Pa to 12~15min.

10. The method for reducing and dephosphorizing refined deoxidized alloyed molten steel according to any one of claims 1 to 9, characterized in that: 15~30% by mass of phosphorus is removed from the refined, deoxidized and alloyed molten steel.