A control method for low-carbon aluminum-killed steel direct-up continuous casting

Abstract

The present application belongs to the technical field of steelmaking, and specifically discloses a control method for low-carbon aluminum killed steel direct-up continuous casting, which comprises the following steps: desulfurizing the molten iron, then carrying out converter oxygen blowing smelting, adding the slag forming agent according to the slag basicity and MgO content in the slag, adding silicon-calcium alloy to the ladle bottom, starting to add silicon-calcium alloy when tapping, carrying out middle stirring argon blowing treatment, adding aluminum particles to the steel slag surface, adding a deoxidizer according to the end oxygen content of the molten iron in the ladle, then sending the ladle into the argon blowing station, and using strong stirring to quickly complete the top slag reforming. In the treatment process of the three modes, additional equipment is required, which leads to the increase of production cost and operation complexity. In the present application, the silicon-calcium alloy is used to replace the carbide to carry out pre-deoxidation treatment on the molten iron, so that the phenomenon of carbon increase caused by the carbide in the deoxidation process is eliminated, and the silicon-calcium alloy + aluminum particles are used to carry out deoxidation on the molten steel and the steel slag, the argon station does not carry out wire feeding treatment, and the alloy cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steelmaking, in particular to a control method for low-carbon aluminum-killed steel direct-up continuous casting. BACKGROUND

[0002] Low-carbon aluminum-killed steel is one of the main steel grades for producing cold-rolled sheet, which is widely used in the automobile, household appliance, packaging and other industries. In order to obtain good formability, it needs to have the properties of low carbon, low silicon and low nitrogen, and the strict control of silicon content is particularly important. Although the increase of silicon content in molten steel can improve the strength of the sheet, it will reduce the stamping performance, and when the silicon content is high, the surface of the cold-rolled sheet is easy to generate oxide "red rust", which brings difficulties to the subsequent process production.

[0003] In the traditional production process, low-carbon aluminum-killed steel usually requires a certain amount of aluminum content to improve the organizational structure and eliminate subcutaneous bubbles. In addition, the number of inclusions in the steel should be small, the size should be small and plastic. A large amount of aluminum is used for deoxidation in production, which will produce a large amount of spherical A1203 due to the excess oxygen in the molten steel. In order to ensure the purity of the molten steel and make the spherical inclusions effectively float, LF+calcium treatment, CAS+calcium treatment or LF+calcium-free treatment and other methods are usually used for treatment.

[0004] However, the above treatment methods need to control the amount of calcium added during the refining process in the LF furnace, otherwise it will lead to unsatisfactory control of the inclusion form, affecting the quality of the steel, and if not properly controlled, it may also produce new types of inclusions, thereby not only increasing the cost of equipment, but also increasing the complexity of operation. SUMMARY

[0005] The purpose of the present application is to provide a control method for low-carbon aluminum-killed steel direct-up continuous casting, to solve the problem of additional equipment, increased production cost and operation complexity in the treatment process of the three methods.

[0006] To achieve the above purpose, the basic scheme provided by the present application is: a control method for low-carbon aluminum-killed steel direct-up continuous casting, comprising the following steps:

[0007] S1, desulfurization treatment is performed on the molten iron, and slagging treatment is performed on the molten iron, and the slagging standard is that the molten iron 3 / 4 liquid surface is exposed;

[0008] S2, pour 108-115t of desulfurized molten iron into the converter, and add 15-20t of scrap steel, and perform oxygen blowing smelting, the addition amount of slagging agent is added according to the target slag basicity and MgO content in the slag, to ensure that the TFe content in the final slag is ≤16%;

[0009] S3, after the blowing is completed, 90-110 kg of silicon-calcium alloy is added into the ladle without molten iron before tapping, and then the tapping is carried out, the oxygen is determined during the tapping, and the temperature is sampled, 40-60 kg of silicon-calcium alloy is added into the ladle before the alloy is added, and the middle stirring argon treatment is carried out, the middle stirring time is 4-6 min, and after the tapping is completed, 40-60 kg of aluminum particles is added to the surface of the molten steel in the ladle;

[0010] S4, the deoxidizer is added according to the terminal oxygen content of the molten steel in the ladle, when the oxygen is determined abnormally, the deoxidizer is added according to the terminal carbon content, and the target aluminum content of the molten steel is 0.03-0.05%;

[0011] S5, the ladle is sent into the argon blowing station again, the top slag is changed and modified rapidly by using strong stirring, the strong stirring time is greater than or equal to 5 min, after the top slag in the surface of the ladle is deoxidized, soft blowing treatment is carried out, and the soft blowing time is greater than or equal to 8 min;

[0012] S6, finally, the molten steel is sent into the continuous casting machine for casting.

[0013] The beneficial effects of the present application are that: the silicon-calcium alloy is used to replace the carbide for the pre-deoxidation treatment of the molten steel, on the one hand, the phenomenon of carbon increase caused by the carbide in the deoxidation process is avoided, on the other hand, the residual Ca element in the alloy enters the molten steel to provide a certain Ca content of the molten steel, and the appropriate Ca / Al ratio can effectively improve the castability of the molten steel and ensure the continuous production of continuous casting; at the same time, the silicon-calcium alloy+aluminum particles are used for the deoxidation of the molten steel and the steel slag, the argon station does not carry out wire feeding treatment, the temperature of the converter tapping is reduced, the erosion of the high-temperature low-carbon high-oxygen slag on the lining is reduced, the addition amount of aluminum-iron alloy is reduced, the alloy cost is reduced, and at the same time, the argon station does not carry out wire feeding treatment, after the new process of deoxidation of low-carbon low-silicon steel, the operation process of the converter process is stabilized, the production of the on-site furnace machine is more matched, and the production efficiency is further improved.

[0014] Scheme two, which is a preferred embodiment of the basic scheme, in S1, the composition of the molten iron into the furnace: the Si content is 0.10-0.85%, the Mn content is 0.20-0.50%, the P content is less than 0.120%, the S content is less than 0.045%, and the temperature of the molten iron is greater than 1280 DEG C.

[0015] Scheme three, which is a preferred embodiment of the basic scheme, in S2, the target basicity R of the slag is 3.0-3.5, and the target MgO content in the slag is 9-10%.

[0016] Scheme four, which is a preferred embodiment of the basic scheme, in S2, the blowing gun position is 1300-1500 mm away from the liquid surface, the oxygen supply flow rate is 27500-28500 m 3 / h, the gun position in the carbon fire stage is adjusted to be 1650-1750 mm away from the liquid surface, and the oxygen supply flow rate is reduced to 25500-26500 m 3 / h, the oxygen lance position in the middle of oxygen blowing is 1600-1800 mm from the liquid surface, and the oxygen supply flow rate is 25500-26500 m 3 / h, the oxygen lance position in the middle of oxygen blowing is 1600-1800 mm from the liquid surface, and the oxygen supply flow rate is 25500-26500 m 3 / h, the oxygen lance position in the middle of oxygen blowing is 1600-1800 mm from the liquid surface, and the oxygen supply flow rate is 25500-26500 m

[0017] In the scheme five, which is a preferred scheme of the basic scheme, in S3, the tapping temperature is 1655-1670 DEG C, and the tapping time is 3-5.5 min.

[0018] In the scheme six, which is a preferred scheme of the basic scheme, in S3, the silicon-calcium alloy composition is as follows: the carbon content is 0.03-0.05%, the silicon content is 20.15-22.15%, the sulfur content is 0.006-0.08%, the phosphorus content is 0.033-0.53%, and the calcium content is 30-32%. Through the suitable alloy composition, the silicon-calcium alloy can better play the roles of deoxidation and improving the castability of the molten steel.

[0019] In the scheme seven, which is a preferred scheme of the basic scheme, the strong stirring opening diameter is 500-600 mm, the medium stirring opening diameter is 300-400 mm, and the soft blowing opening diameter is 150-200 mm. DETAILED DESCRIPTION

[0020] The application will be further described in detail through specific embodiments:

[0021] A control method of low-carbon aluminum-killed steel straight-up continuous casting, comprising the following steps:

[0022] S1, desulfurization treatment is performed on the molten iron, and slagging treatment is performed on the molten iron, the slagging standard is that the molten iron 3 / 4 liquid surface is exposed, the composition of the molten iron entering the furnace is as follows: the silicon content is 0.30%, the manganese content is 0.20%, the phosphorus content is 0.10%, the sulfur content is 0.038%, and the molten iron temperature is 1300 DEG C;

[0023] S2, 110 t of the desulfurized molten iron is poured into a converter, 15 t of scrap steel is added, high-sulfur scrap steel such as slag, oil stains, and heating fins is prohibited to be added into the converter, oxygen blowing smelting is performed, the addition amount of the slagging agent is added according to the target slag basicity R=3.2 and the MgO content in the slag being 9.5%, the TFe content in the final slag is ensured to be 15%, the oxygen lance position in the beginning of oxygen blowing is 1400 mm from the liquid surface, and the oxygen supply flow rate is 28000 m 3 / h, the oxygen lance position in the middle of oxygen blowing is 1600-1800 mm from the liquid surface, and the oxygen supply flow rate is 25500-26500 m3 / h, the lance position in the middle of oxygen blowing is 1700mm from the liquid surface, and the oxygen supply flow is 26000m 3 / h, the lance position in the carbon pulling stage is lowered to 1000mm from the liquid surface, the oxygen supply flow is 28000m3 / h, the carbon pulling lance lowering time is 38s, and the endpoint C is judged according to the flame shape;

[0024] S3, after the blowing is completed, 100kg of silicon-calcium alloy is added into the ladle without molten iron before tapping, and then the tapping is performed, the oxygen is determined during the tapping, the temperature is measured and sampled, 50kg of silicon-calcium alloy is added into the ladle before the alloy is added before the tapping is started, the intermediate stirring and argon blowing treatment is performed, the intermediate stirring opening diameter is 400mm, the intermediate stirring time is 5min, after the tapping is completed, 50kg of aluminum particles is added to the surface of the molten steel in the ladle, the slag blocking mode is the slide plate slag blocking, and the silicon-calcium alloy composition is that the carbon content is 0.04%, the silicon content is 21.15%, the sulfur content is 0.07%, the phosphorus content is 0.43%, and the calcium content is 31%;

[0025] Table 1: Alloy type and dosage

[0026] consumption pre-deoxidizer (silicon-calcium alloy low-carbon ferromanganese (alloy) deoxidizer (aluminum-iron) top-slag modifier (aluminum particles) single-hearth kg 150 50-100 350-500 50 ton steel kg / t 1.25 0.4-0.8 2.9-4.2 0.42

[0027] Table 2: Tapping temperature control requirements of each steel grade

[0028] casting condition tapping °c (reference) ar station °c top-pouring temperature °c tundish (superheat 20-30 °c) continuous casting 1660 1615 1595 1550-1555 start-up / insertion 1670 1620 1600 1550-1560

[0029] S4, the deoxidizer is added according to the endpoint oxygen content of the molten steel in the ladle, when the oxygen is determined, the deoxidizer is added according to the endpoint carbon content (see Table 3 for details), and the target aluminum content of the molten steel is 0.04%;

[0030] Table 3: Endpoint oxygen content / carbon content and deoxidizer addition amount table

[0031] end-point [c] % end-point temperature °c end-point [o] ppm deoxidizer addition kg 0.04 1660 738 300 0.045 1660 665 300 0.05 1660 599 280 0.055 1660 544 250 0.06 1660 499 250 0.065 1660 461 250 0.07 1660 428 200 0.075 1660 400 200 0.08 1660 375 200

[0032] S5, the ladle is sent to the argon blowing station again, the top slag modification is quickly completed by using the strong stirring, the strong stirring opening diameter is 600mm, the strong stirring time is 5min, after the top slag deoxidation of the inner surface of the ladle is completed, the soft blowing treatment is performed, the soft blowing opening diameter is 200mm, the soft blowing time is 8min, and the ladle turnover time is 1.5h;

[0033] S6, finally, the molten steel is sent to the continuous casting machine for casting.

[0034] A low-carbon aluminum killed steel calcium-free treatment direct operation method is adopted, the silicon-calcium alloy+aluminum ingot is used for molten steel and slag deoxidation, the argon station does not perform wire feeding treatment, after the new deoxidation process of low-carbon low-silicon steel, the converter process operation flow is stabilized, the on-site furnace machine production is more matched, and the production efficiency is further improved.

[0035] The above-mentioned are only embodiments of the present application, and the common knowledge of specific structures and characteristics in the scheme is not described too much. It should be pointed out that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, which will not affect the effect and practicality of the patent. The protection scope claimed in this application should be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. A control method for direct continuous casting of low-carbon aluminum killed steel, characterized in that, Includes the following steps: S1. Desulfurize the molten iron and remove the slag. The standard for removing slag is to expose 3 / 4 of the molten iron surface. S2. Pour 108-115t of desulfurized molten iron into the converter, add 15-20t of scrap steel, and carry out oxygen blowing smelting. The amount of slag-forming agent added is based on the target slag basicity and MgO content in the slag to ensure that the TFe content in the final slag is ≤16%. S3. After the blowing is completed, 90-110 kg of silicon-calcium alloy is added to the ladle before tapping. Then the ladle is turned over and tapped. During the turning, oxygen is controlled and temperature is measured and sampled. From the start of tapping until the alloy is added, another 40-60 kg of silicon-calcium alloy is added to the ladle. Argon blowing is carried out during the intermediate stirring. The intermediate stirring time is 4-6 minutes. After tapping, 40-60 kg of aluminum particles are added to the surface of the molten steel in the ladle. S4. Add deoxidizer according to the final oxygen content of the molten steel in the ladle. If the oxygen content is abnormal, add deoxidizer according to the final carbon content. The target aluminum content of the molten steel is 0.03-0.05%. S5. Then send the ladle into the argon blowing station and use strong stirring to quickly complete the top slag modification. The strong stirring time is ≥5min. After the top slag on the inner surface of the ladle is deoxidized, perform soft blowing treatment. The soft blowing time is ≥8min. S6. Finally, the molten steel is sent to the continuous casting machine for casting.

2. The control method for direct continuous casting of low-carbon aluminum killed steel according to claim 1, characterized in that, In S1, the composition of the molten iron fed into the furnace is as follows: Si content is 0.10-0.85%, Mn content is 0.20-0.50%, P content is <0.120%, S content is <0.045%, and the molten iron temperature is >1280℃.

3. The control method for direct continuous casting of low-carbon aluminum killed steel according to claim 1, characterized in that, In S2, the target basicity of the slag R is 3.0 to 3.5, and the target MgO content in the slag is 9 to 10%.

4. The control method for direct continuous casting of low-carbon aluminum killed steel according to claim 1, characterized in that, In S2, the blow gun is positioned 1300–1500 mm from the liquid surface, and the oxygen supply flow rate is 27500–28500 m³ / h. 3 During the charcoal-fire stage, the lance position is adjusted to 1650–1750 mm above the liquid surface, and the oxygen supply flow rate is reduced to 25500–26500 m³ / h. During the middle stage of oxygen blowing, the lance position is 1600–1800 mm above the liquid surface, and the oxygen supply flow rate is 25500–26500 m³ / h. 3 During the carbon extraction stage, the gun position is lowered to 950–1050 mm from the liquid surface, and the oxygen supply flow rate is 27,500–28,500 m³ / h. 3 / h, carbon removal time ≤40s.

5. The control method for direct continuous casting of low-carbon aluminum killed steel according to claim 1, characterized in that, In S3, the tapping temperature is 1655~1670℃, and the tapping time is 3min~5.5min.

6. The control method for direct continuous casting of low-carbon aluminum killed steel according to claim 1, characterized in that, In S3, the silicon-calcium alloy composition is as follows: carbon content is 0.03-0.05%, silicon content is 20.15-22.15%, sulfur content is 0.006-0.08%, phosphorus content is 0.033-0.53%, and calcium content is 30-32%.

7. The control method for direct continuous casting of low-carbon aluminum killed steel according to claim 1, characterized in that, The diameter of the strong stirring and blowing is 500-600mm, the diameter of the medium stirring and blowing is 300-400mm, and the diameter of the soft blowing and blowing is 150-200mm.