Smelting method of high-cleanliness steel

Abstract

The invention provides a smelting method of high-cleanliness steel, which comprises the following steps: A) converter process: coating a steel ladle wall with inclusion modifier slurry before tapping, and then tapping and deoxidizing and alloying; wherein the inclusion modifier slurry comprises powder and a solvent; the powder comprises the following components in percentage by mass: 61%-79% of CaO; 15.5% to 19.5% of Al2O3 (aluminum oxide); 0%-4.5% of SiO2; 0%-4.5% of MgO; the content of CC is 5.1%-9.5%; the balance is unavoidable impurities; b) argon blowing: after tapping in the step A) is finished, carrying out bottom argon blowing on the steel ladle; c) a continuous casting process: after the argon blowing process in the step B) is finished, carrying out continuous casting; wherein argon blowing is accompanied in the casting drainage process of the continuous casting ladle. According to the method, the problems of insufficient reaction and large slag consumption caused by a conventional short-process slag washing process are effectively avoided, and the steel cleanliness and the production efficiency are improved.

Description

Technical Field

[0001] The invention relates to the field of steelmaking, and in particular to a method for smelting high-cleanliness steel. Background Art

[0002] The steelmaking production process mainly includes the following steps: hot metal pretreatment step → converter steelmaking step → refining step (usually LF refining) → continuous casting step. As my country's energy conservation and emission reduction work continues to deepen, more and more steelmaking companies are exploring the elimination of the LF step to achieve economical and efficient production of steel grades. For non-special purpose steels such as low-carbon aluminum killed steel and ordinary carbon steel, more and more manufacturers are using the short process of "converter-continuous casting" to produce them.

[0003] However, for low-carbon aluminum series steel, due to the low control of carbon content of converter steel, high oxygen activity in steel and high oxidation of converter final slag, the amount of deoxidation alloy added is large, resulting in more non-metallic oxide inclusions generated by deoxidation. It is difficult to achieve full and effective floating of inclusions under the short process; in addition, due to the lack of strong stirring in the LF process, the steel-slag reaction is not sufficient, and the Al2O3 inclusions in the steel have not been effectively modified and still exist in large quantities in the molten steel; due to the large surface tension of Al2O3 inclusions, they are very easy to aggregate during the continuous casting process, causing nodules and even interruption of casting; and the clustered Al2O3 inclusions remaining in the steel are very easy to form product surface defects during the cold rolling process.

[0004] Therefore, in order to solve the above problems when using the "converter-continuous casting" short process to produce low-carbon aluminum series steel, steelmaking companies often use the process of adding lime and other modifiers during the converter steel-making process to modify the inclusions in the steel, and at the end of steel-making, argon is blown from the bottom of the ladle to promote the floating of inclusions. However, since the melting point of lime is as high as 2572℃ and its density is much lower than that of molten steel, a large amount of unmelted lime still floats on the ladle surface at the end of steel-making, and the inclusions in the steel are not effectively modified. Summary of the invention

[0005] In view of this, the present invention provides a method for smelting high-cleanliness steel. The method of the present invention can effectively avoid the problems of insufficient reaction and large slag consumption caused by the conventional short-process slag washing process, and improve the cleanliness of steel and production efficiency.

[0006] The present invention provides a method for smelting high-cleanliness steel, comprising the following steps:

[0007] A) Converter process:

[0008] Before tapping, the inclusion modifier slurry is applied to the ladle wall, and then the steel is tapped and deoxidized and alloyed;

[0009] in,

[0010] The inclusion modifier slurry comprises powder and solvent;

[0011] In terms of mass percentage, the powder comprises the following components:

[0012] CaO: 61%~79%;

[0013] Al2O3: 15.5%~19.5%;

[0014] SiO2: 0%~4.5%;

[0015] MgO: 0%~4.5%;

[0016] C: 5.1%~9.5%;

[0017] The rest are unavoidable impurities;

[0018] B) Argon blowing process:

[0019] After the steel is tapped in step A), argon is blown from the bottom of the ladle;

[0020] C) Continuous Casting Process:

[0021] After the argon blowing process in step B) is completed, continuous casting is carried out; wherein the continuous casting ladle is opened for pouring and draining accompanied by argon blowing.

[0022] Preferably, the powder is prepared by the following preparation method:

[0023] S1, melting a CaO raw material, an Al2O3 raw material, a SiO2 raw material and a MgO raw material to form a pre-molten slag;

[0024] S2, mixing and grinding the pre-melted slag and carbon powder to obtain powder.

[0025] Preferably, the fineness of the powder is 700nm to 50μm.

[0026] Preferably, in the inclusion modifier slurry, the mass of the solvent is 35% to 60% of the mass of the powder.

[0027] Preferably, the solvent is water;

[0028] After the inclusion modifier slurry is coated on the ladle wall, baking is also performed; the baking temperature is 900-1100° C. and the time is 24-48 hours.

[0029] Preferably, in step A), the coating thickness is 5 to 12 mm.

[0030] Preferably, in step A), the process of tapping and deoxidation alloying specifically includes: adding aluminum-iron alloy and inclusion modifier balls to the ladle when 1 / 7 to 1 / 6 of the steel is tapped, and then adding other ferroalloys to alloy the molten steel after 20 to 40 seconds;

[0031] Wherein, the inclusion modifier ball includes powder;

[0032] In terms of mass percentage, the powder comprises the following components:

[0033] CaO: 61%~79%;

[0034] Al2O3: 15.5%~19.5%;

[0035] SiO2: 0%~4.5%;

[0036] MgO: 0%~4.5%;

[0037] C: 5.1%~9.5%;

[0038] The rest are inevitable impurities.

[0039] Preferably, the inclusion modifier ball is added in an amount of 0.5 to 2.5 kg / t steel;

[0040] The inclusion modifier ball is prepared by the following preparation method: powder, binder and water are mixed, pressed into balls, and dried to obtain the inclusion modifier ball.

[0041] Preferably, in step B), the flow rate of the bottom blowing argon is 120-150 NL / min, and the time is 5-8 min.

[0042] Preferably, in step C), the argon blowing comprises: after the ladle starts pouring, the argon blowing flow rate of the ladle bottom is 120-150NL / min, when the ladle is poured 1 / 4-1 / 3, the argon blowing flow rate of the ladle bottom is reduced to 80-120NL / min, and when the ladle pouring amount is 2 / 3-3 / 4, the bottom argon blowing is turned off.

[0043] The smelting method provided by the present invention is a smelting method of low-cost high-cleanliness steel. The composition and modification method of the inclusion modifier are designed. The inclusion modifier slurry containing ultrafine powder is sprayed onto the inner wall of the ladle before tapping. A certain amount of inclusion modifier balls are added during the tapping process. Argon is blown at the bottom of the ladle after tapping and during the continuous casting process. During the tapping-continuous casting process, the modifier fully reacts with inclusions such as SiO2 and Al2O3 in the steel, expands the reaction area between the modifier and the molten steel, and continuously and comprehensively reacts with the contact reaction, effectively avoiding the problems of insufficient reaction and large slag consumption caused by the conventional short-process slag washing process. The above method effectively achieves the improvement of steel cleanliness under the short process, the number of continuous casting furnaces in the middle ladle is increased by more than 55%, and the number of inclusions larger than 5μm in the ingot is reduced by more than 57%, which has significant economic and social benefits. DETAILED DESCRIPTION

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0045] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0046] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] Herein, when it comes to numerical ranges, unless otherwise specified, the numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0048] In this article, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 5-12mm means that the units of the left endpoint "5" and the right endpoint "12" are both mm.

[0049] The present invention provides a method for smelting high-cleanliness steel, comprising the following steps:

[0050] A) Converter process:

[0051] Before tapping, the inclusion modifier slurry is applied to the ladle wall, and then the steel is tapped and deoxidized and alloyed;

[0052] in,

[0053] The inclusion modifier slurry comprises powder and solvent;

[0054] In terms of mass percentage, the powder comprises the following components:

[0055] CaO: 61%~79%;

[0056] Al2O3: 15.5%~19.5%;

[0057] SiO2: 0%~4.5%;

[0058] MgO: 0%~4.5%;

[0059] C: 5.1%~9.5%;

[0060] The rest are unavoidable impurities;

[0061] B) Argon blowing process:

[0062] After the steel is tapped in step A), argon is blown from the bottom of the ladle;

[0063] C) Continuous Casting Process:

[0064] After the argon blowing process in step B) is completed, continuous casting is carried out; wherein the continuous casting ladle is opened for pouring and draining accompanied by argon blowing.

[0065] The smelting method provided by the present invention comprises a process flow of a converter process-argon blowing process-continuous casting process; the converter process comprises uniformly spraying an inclusion modifier on the wall of a ladle before tapping, tapping the steel and performing deoxidation and alloying; the argon blowing process blows a small amount of argon to the bottom of the molten steel so that non-metallic oxides in the steel react fully with the inclusion modifier on the inner wall of the ladle, thereby achieving effective modification of Al2O3 inclusions in the steel; in the continuous casting process, argon is blown at the bottom of the ladle to promote the floating removal of inclusions in the steel, and further modify the residual Al2O3 inclusions in the steel to obtain molten steel with higher cleanliness.

[0066] [About Step A]:

[0067] A) Converter process: before tapping, the inclusion modifier is applied to the ladle wall, and then the steel is tapped and deoxidized and alloyed.

[0068] The actual implementation process of converter steelmaking mainly includes: charging → blowing → tapping (accompanied by deoxidation and alloying) → slag splashing, furnace protection and slag pouring. Specifically, the raw materials are loaded into the converter and then the oxygen lance is lowered to start blowing oxygen. When the blowing end is reached, the lance is lifted to pour the furnace, the temperature is measured and the composition is sampled for testing. If the temperature and composition of the molten steel meet the target, the steel is tapped. Otherwise, the oxygen lance is lowered for re-blowing until it is qualified, and then the steel is tapped; tapping is the process of pouring the molten steel in the furnace into the ladle. During the tapping process, deoxidizers and ferroalloys are added for deoxidation and alloying to obtain converter molten steel.

[0069] In the present invention, before the steel tapping operation in the converter process, preparatory work is first performed, that is, inclusion modifier slurry is coated on the ladle wall before steel tapping, so that when steel tapping, the molten steel is sent into the ladle with the inclusion modifier coated on the ladle wall.

[0070] In the present invention, the inclusion modifier slurry comprises powder and solvent.

[0071] Wherein, the powder includes the following components in percentage by mass:

[0072] CaO: 61%~79%;

[0073] Al2O3: 15.5%~19.5%;

[0074] SiO2: 0%~4.5%;

[0075] MgO: 0%~4.5%;

[0076] CC: 5.1%-9.5%;

[0077] The rest are inevitable impurities.

[0078] The content of CaO can be specifically 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%. The CaO component is derived from a raw material containing CaO.

[0079] The content of Al2O3 can be specifically 15.5%, 15.6%, 15.7%, 15.8%, 15.9%, 16.0%, 16.1%, 16.2%, 16.3%, 16.4%, 16.5%, 16.6%, 16.7%, 16.8%, 16.9%, 17.0%, 17.1%, 17.2%, 17.3%, 17.4%, 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18.0%, 18.1%, 18.2%, 18.3%, 18.4%, 18.5%, 18.6%, 18.7%, 18.8%, 18.9%, 19.0%, 19.1%, 19.2%, 19.3%, 19.4%, 19.5%, 19.6%, 19.7%, 19.8%, 19 ... .4%, 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18.0%, 18.1%, 18.2%, 18.3%, 18.4%, 18.5%, 18.6%, 18.7%, 18.8%, 18.9%, 19.0%, 19.1%, 19.2%, 19.3%, 19.4%, 19.5%.

[0080] The content of SiO2 can specifically be 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, and 4.5%.

[0081] The content of MgO can be specifically 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, and 4.5%.

[0082] The C content can specifically be 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, 9.2%, 9.3%, 9.4%, and 9.5%.

[0083] Except the above ingredients, the rest are inevitable impurities.

[0084] In one embodiment of the present invention, the compositions of the powders in the inclusion modifier slurry and the inclusion modifier balls are as follows: CaO: 61%, carbon powder: 9.5%, Al2O3: 19.5%, SiO2: 4.5%, MgO: 0%, and the rest are inevitable impurities. In another embodiment of the present invention, the compositions of the powders in the inclusion modifier slurry and the inclusion modifier balls are as follows: CaO: 79%, carbon powder: 5.1%, Al2O3: 15.5%, SiO2: 0%, MgO: 4.5%, and the rest are inevitable impurities.

[0085] In the present invention, the powder is preferably obtained by the following preparation method: S1: melting a CaO raw material, an Al2O3 raw material, a SiO2 raw material and a MgO raw material to form a pre-melted slag; S2: mixing and grinding the pre-melted slag with carbon powder to obtain a powder.

[0086] The CaO supplying raw material is a raw material containing CaO or a raw material that can decompose CaO, preferably at least one of CaO (commonly known as quicklime) and calcium carbonate.

[0087] The Al2O3 raw material is a raw material containing Al2O3 or a raw material that can decompose Al2O3, preferably at least one of Al2O3, corundum slag, Al2O3 premelt and bauxite, and can also be other industrial raw materials or ores containing Al2O3.

[0088] The SiO2 raw material is a raw material containing SiO2 or a raw material that can decompose SiO2, preferably at least one of SiO2, a pre-melted material containing SiO2 and quartz sand.

[0089] The MgO supplying raw material is a raw material containing MgO or a raw material that can decompose MgO, preferably at least one of MgO, a pre-melted material containing MgO, dolomite and magnesia.

[0090] The carbon powder is preferably a carbonaceous material having a carbon content greater than 85%, and more preferably at least one of petroleum coke, graphite, and anthracite.

[0091] In the present invention, the amount of each raw material is matched based on the ratio of each component in the target powder, that is, the amount of each raw material is calculated based on the ratio of each component in the target powder. The unavoidable impurities mentioned above are some unavoidable impurities brought by the above raw materials.

[0092] In step S1, the melting can be carried out in an induction furnace, that is, the raw materials for CaO, Al2O3, SiO2 and MgO are put into an induction furnace for melting to prepare pre-molten slag. The melting temperature is preferably 1700-1900°C, specifically 1700°C, 1750°C, 1800°C, 1850°C, 1900°C. After all the raw materials are completely melted, they are water-cooled, dried and crushed before being put into the next step.

[0093] In step S2, the mixed grinding method is not particularly limited and can be any conventional grinding method in the art, such as ball milling, etc. The goal of grinding is preferably to grind into ultrafine powder with a fineness of 700nm to 50μm.

[0094] In the present invention, after the powder is obtained, it is mixed with a solvent to form a slurry. In the present invention, the solvent is preferably water. The mass of the solvent is preferably 35% to 60% of the mass of the powder, specifically 35%, 40%, 45%, 50%, 55%, 60%. The preparation process of the slurry can be specifically as follows: the powder and the solvent are mixed evenly to obtain a slurry, that is, the inclusion modifier slurry. The mixing can be performed by a pulping machine, that is, the powder and the solvent are added to the pulping machine, stirred evenly, and the slurry is obtained.

[0095] In the present invention, before steel is tapped, the inclusion modifier slurry is applied to the ladle wall. The coating method is not particularly limited, and it can be a conventional coating method, preferably spraying. In the present invention, the coating thickness is preferably 5 to 12 mm, specifically 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm. In the present invention, after the inclusion modifier is applied to the ladle wall, the ladle is preferably baked to form a firm coating on the inner wall of the ladle. The baking temperature is preferably 900 to 1100 ° C, specifically 900 ° C, 950 ° C, 1000 ° C, 1050 ° C, 1100 ° C; the baking time is preferably 24 to 48 h, specifically 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h.

[0096] In the present invention, the inclusion modifier coating is applied to the ladle wall before steel tapping to form an inclusion modifier coating, and then steel tapping and deoxidation alloying are performed. In the present invention, the process of steel tapping and deoxidation alloying preferably specifically includes: when 1 / 7 to 1 / 6 of the steel is tapped, aluminum-iron alloy and inclusion modifier balls are added to the ladle, and then other iron alloys are added after a period of time to alloy the molten iron. Among them, 1 / 7 to 1 / 6 of steel tapping means that 1 / 7 to 1 / 6 of the amount of molten steel (the amount is measured by mass) is poured out when the converter taps, that is, the ratio of the amount of molten steel poured out / the total amount of molten steel = 1 / 7 to 1 / 6, which can be specifically 1 / 7 or 1 / 6. When the above amount of steel is tapped, aluminum-iron alloy and inclusion modifier balls are added to the ladle.

[0097] In the present invention, the inclusion modifier ball includes powder. The components and the content selection range of each component in the powder are consistent with the powder in the inclusion modifier slurry described in the above technical solution, and the preparation method of the powder is also consistent with that described in the above technical solution, which will not be repeated here.

[0098] In the present invention, the inclusion modifier ball is prepared by the following preparation method: mixing powder, binder and water, pressing into balls, drying, and obtaining inclusion modifier balls. Among them, the type of the binder is not particularly limited, and it can be a conventional inorganic binder and / or an organic binder. The inorganic binder includes but is not limited to clay and bentonite. The mass of the binder accounts for 3% to 10% of the total mass of the powder and the binder, and can be specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. The mass of the water accounts for 10% to 20% of the total mass of the powder and the binder, and can be specifically 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%. The mixing method is not particularly limited, and the materials can be mixed evenly by the conventional mixing method in the field, such as stirring evenly by a mixer. The pressing into balls can be achieved by a ball press. The particle size of the inclusion modifier balls is preferably 10 to 30 mm.

[0099] In the present invention, the dosage of the inclusion modifier ball is preferably 0.5-2.5 kg / t steel, specifically 0.5 kg / t steel, 0.6 kg / t steel, 0.7 kg / t steel, 0.8 kg / t steel, 0.9 kg / t steel, 1.0 kg / t steel, 1.1 kg / t steel, 1.2 kg / t steel, 1.3 kg / t steel, 1.4 kg / t steel, 1.5 kg / t steel, 1.6 kg / t steel, 1.7 kg / t steel, 1.8 kg / t steel, 1.9 kg / t steel, 2.0 kg / t steel, 2.1 kg / t steel, 2.2 kg / t steel, 2.3 kg / t steel, 2.4 kg / t steel, 2.5 kg / t steel. After adding the above materials, a period of time is preferably 20-40 seconds, specifically 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds. Then other iron alloys (such as ferrosilicon, ferromanganese, etc.) are added to alloy the molten steel. In the above process, aluminum-iron alloys and other iron alloys (such as ferrosilicon, ferromanganese, etc.) are added. The present invention has no special restrictions on the types and amounts of these iron alloys. They can be conventional iron alloys and amounts used in steelmaking processes in the field of steelmaking for deoxidation and alloying. After the above alloying, steel is continuously tapped until all the molten steel is tapped.

[0100] [About step B]:

[0101] B) Argon blowing process: After the steel tapping in step A is completed, argon is blown from the bottom of the ladle.

[0102] In the present invention, after the steel is tapped in step A), argon is blown from the bottom of the ladle to promote the reaction of inclusions in the steel with the ladle wall and the modifier on the steel liquid surface, thereby modifying the inclusions in the steel. In the present invention, the flow rate of the bottom blowing argon is preferably 120-150NL / min, specifically 120NL / min, 125NL / min, 130NL / min, 135NL / min, 140NL / min, 145NL / min, 150NL / min. The time of the bottom blowing argon is preferably 5-8min, specifically 5min, 6min, 7min, 8min.

[0103] [About Step C]:

[0104] C) Continuous casting process: After the argon blowing process in step B) is completed, continuous casting is carried out; wherein the continuous casting ladle pouring and drainage process is accompanied by argon blowing.

[0105] The continuous casting process is a process of sending refined molten steel into a continuous casting machine for continuous casting to form continuous casting billets. Specifically, the ladle filled with refined molten steel is transported to the pouring position, and the molten steel in the ladle is continuously poured into the tundish, and after being diverted by the tundish, it is injected into each crystallizer of the continuous casting machine for cooling and solidification to obtain a cast billet.

[0106] In the present invention, the above-mentioned continuous casting ladle pouring and drainage process is accompanied by argon blowing, specifically argon blowing from the bottom of the ladle. In the present invention, the argon blowing from the bottom of the ladle in the continuous casting process is preferably: after the ladle pouring, the argon blowing flow rate of the ladle bottom is 120-150NL / min, when the ladle pours 1 / 4-1 / 3, the argon blowing flow rate of the ladle bottom is reduced to 80-120NL / min, and when the ladle pours 2 / 3-3 / 4, the bottom argon blowing is turned off.

[0107] Among them, after the ladle starts pouring, the argon blowing flow rate at the bottom of the ladle is 120-150NL / min, specifically 120NL / min, 125NL / min, 130NL / min, 135NL / min, 140NL / min, 145NL / min, 150NL / min. When the ladle is poured 1 / 4-1 / 3, the argon blowing flow rate is lowered to 80-120NL / min, specifically 80NL / min, 85NL / min, 90NL / min, 95NL / min, 100NL / min, 105NL / min, 110NL / min, 115NL / min, 120NL / min; compared with the previous stage, the argon blowing flow rate is lowered, so the argon blowing flow rates of the two stages are not 120NL / min at the same time. Among them, ladle pouring 1 / 4 to 1 / 3 means that 1 / 4 to 1 / 3 of the molten steel in the ladle (the amount is measured by mass) is poured out, that is, the ratio of the amount of molten steel poured out of the ladle / the initial total amount of molten steel in the ladle = 1 / 4 to 1 / 3, which can be specifically 1 / 4 or 1 / 3. When the ladle pouring amount is 2 / 3 to 3 / 4, turn off the bottom argon blowing; wherein, the ladle pouring amount of 2 / 3 to 3 / 4 has the same meaning as above, and so on, which will not be repeated here; the 2 / 3 to 3 / 4 can specifically be 2 / 3 or 3 / 4. After the continuous casting process, the ingot is obtained.

[0108] The smelting method provided by the present invention is a smelting method of low-cost high-cleanliness steel. The composition and modification method of the inclusion modifier are designed. The inclusion modifier slurry containing ultrafine powder is sprayed onto the inner wall of the ladle before tapping. A certain amount of inclusion modifier balls are added during the tapping process. Argon is blown at the bottom of the ladle after tapping and during the continuous casting process. During the tapping-continuous casting process, the modifier fully reacts with inclusions such as SiO2 and Al2O3 in the steel, expands the reaction area between the modifier and the molten steel, and continuously and comprehensively reacts with the contact reaction, effectively avoiding the problems of insufficient reaction and large slag consumption caused by the conventional short-process slag washing process. The above method effectively achieves the improvement of steel cleanliness under the short process, the number of continuous casting furnaces in the middle ladle is increased by more than 55%, and the number of inclusions larger than 5μm in the ingot is reduced by more than 57%, which has significant economic and social benefits.

[0109] The method of the present invention can be widely applied to high-quality steels such as pipeline steel, SPHC, STB series, etc. The technology is also suitable for inclusion modification of long-process steel grades, stable control of inclusions in steel, and low-cost clean production of steel grades.

[0110] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0111] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available or can be prepared by known methods. The instruments are all conventionally selected in the art. The experimental methods without specific conditions in the examples are carried out according to conventional conditions, such as the conditions described in the literature, books or the methods recommended by the manufacturer.

[0112] In the embodiment, the inclusion modifier slurry is prepared by the following method: S1, calcium carbonate, corundum slag, quartz sand and magnesia are placed in an induction furnace to melt and prepare pre-melted slag. Then water-cooled, dried and crushed. S2, the material obtained in step S1 is mixed evenly with graphite and ground into ultrafine powder with a fineness of 700nm~50μm. S3, the obtained ultrafine powder is added to a pulping machine, and then water accounting for 50% of the total weight of the powder is added, and stirred evenly to obtain the inclusion modifier slurry. Among them, the amount of each raw material used in steps S1 to S2 is calculated by reverse calculation according to the proportion of each component in the target powder. The inclusion modifier ball is prepared by the following method: S1, calcium carbonate, corundum slag, quartz sand and magnesia are placed in an induction furnace to melt and prepare pre-melted slag. Then water-cooled, dried and crushed. S2, the material obtained in step S1 is mixed evenly with graphite and ground into ultrafine powder with a fineness of 700nm~50μm. S3, the obtained ultrafine powder, clay (the amount of which accounts for 5% of the total mass of the ultrafine powder and the binder) and water (the amount of which accounts for 15% of the total mass of the ultrafine powder and the binder) are put into a mixer and stirred evenly, and then pressed into balls with a particle size of 10 to 30 mm by a ball press, and dried to obtain inclusion modifier balls. Among them, the amount of each raw material used in steps S1 to S2 is calculated by reverse calculation according to the proportion of each component in the target powder.

[0113] Comparative Example 1

[0114] The molten steel smelting adopts the process flow of "converter process - argon blowing after the furnace - continuous casting process" for low-carbon aluminum series steel. The product composition is shown in Table 1:

[0115] Table 1: Main component requirements of steel grades / wt%

[0116] C Yes Mn P S Al 0.01～0.03 ≤0.030 0.15～0.25 ≤0.015 ≤0.015 0.015～0.055

[0117] Converter process: When 1 / 3 of the steel is tapped from the converter, add 6kg / ton of steel into the ladle (the modifier is composed of 78% CaO, 15% CaF2, and the rest are unavoidable impurities). After 30 seconds of circulation, add ferroaluminum, ferrosilicon, ferromanganese, etc. to deoxidize and alloy the molten steel.

[0118] Argon blowing after the furnace: After the steelmaking is completed, the molten steel is strongly stirred by blowing argon, the argon flow rate is 300NL / min, and the argon blowing time is 6min.

[0119] Continuous casting process: During the continuous casting process, argon is not blown from the bottom of the ladle.

[0120] Example 1

[0121] The molten steel smelting adopts the process flow of "converter process - argon blowing after the furnace - continuous casting process". The product composition is the same as that of comparative example 1 (ie, as shown in Table 1).

[0122] Preparation before steel tapping: Before steel tapping, spray 5mm thick inclusion modifier slurry on the inner wall of the ladle, where the powder composition is: CaO: 61%, C: 9.5%, Al2O3: 19.5%, SiO2: 4.5%, MgO: 0%, and the rest are inevitable impurities. After spraying, the ladle is baked for 48 hours at a baking temperature of 900℃.

[0123] A) Converter process:

[0124] The steel is tapped using a baked ladle sprayed with an inclusion modifier coating. When the converter taps 1 / 7 of the steel, inclusion modifier balls and aluminum-iron alloy are added to the steel at the same time. The amount of inclusion modifier balls added is 2kg / ton of steel. After the addition is completed, ferrosilicon, ferromanganese and other alloys are added to the steel 20 seconds later to alloy the molten steel.

[0125] The composition of the powder used in the inclusion modifier ball is: CaO: 61%, C: 9.5%, Al2O3: 19.5%, SiO2: 4.5%, MgO: 0%, and the rest are inevitable impurities.

[0126] B) Argon blowing process:

[0127] After the steel is tapped in step A), argon is blown from the bottom of the ladle. The bottom blowing argon flow rate is 120 NL / min and the blowing time is 8 min.

[0128] C) Continuous Casting Process:

[0129] After the argon blowing process in step B) is completed, continuous casting is carried out; wherein the continuous casting ladle is accompanied by argon blowing at the bottom of the ladle during the pouring and drainage process; specifically, the argon blowing flow rate at the bottom of the ladle is 120NL / min after the ladle starts pouring, and when the ladle is poured 1 / 4, the bottom blowing flow rate of the ladle is adjusted to 80NL / min, and when the ladle pouring amount is 2 / 3, the bottom argon blowing is turned off.

[0130] Example 2

[0131] The molten steel smelting adopts the process flow of "converter process - argon blowing after the furnace - continuous casting process". The product composition is the same as that of comparative example 1 (ie, as shown in Table 1).

[0132] Preparation before steel tapping: Spray the inner wall of the ladle with a thickness of 12mm of inclusion modifier slurry, where the powder composition is: CaO: 79%, C: 5.1%, Al2O3: 15.5%, SiO2: 0%, MgO: 4.5%, and the rest are inevitable impurities. After spraying, bake the ladle for 24 hours at a baking temperature of 1100℃.

[0133] A) Converter process:

[0134] The steel is tapped using a baked ladle sprayed with inclusion modifier. When 1 / 6 of the converter is tapped, inclusion modifier and aluminum-iron alloy are added to the steel at the same time. The amount of inclusion modifier added is 0.5kg / ton of steel. After the addition is completed, ferrosilicon, ferromanganese and other alloys are added to the steel 40 seconds later to alloy the molten steel.

[0135] The composition of the powder used in the inclusion modifier ball is: CaO: 79%, C: 5.1%, Al2O3: 15.5%, SiO2: 0%, MgO: 4.5%, and the rest are inevitable impurities.

[0136] B) Argon blowing process:

[0137] After the steel is tapped in step A), the ladle is bottom-blown with argon at a flow rate of 150 NL / min and a blowing time of 5 min.

[0138] C) Continuous Casting Process:

[0139] After the argon blowing process in step B) is completed, continuous casting is carried out; wherein the continuous casting ladle is accompanied by argon blowing at the bottom of the ladle during the pouring and drainage process; specifically, the argon blowing flow rate at the bottom of the ladle is 150NL / min after the ladle starts pouring, and when the ladle is poured 1 / 3, the bottom blowing flow rate of the ladle is adjusted to 120NL / min, and when the ladle pouring amount is 3 / 4, the bottom argon blowing is turned off.

[0140] The steel cleanliness, auxiliary material consumption, and number of continuous casting furnaces of Examples 1-2 and Comparative Example 1 were investigated respectively. The results are shown in Table 2.

[0141] Table 2: Test results

[0142]

[0143] It can be seen from the test results in Table 2 that the free CaO content of the ladle slag at the end of the argon blowing station of the method of the present invention is less than 1.5%, the modifier consumption is less than 2.5kg / t steel, the number of continuous casting furnaces of the tundish is more than 14, and the number of inclusions larger than 5μm in the ingot is less than 10 / cm 2 The present invention achieves an improvement in steel cleanliness under a short process, the number of tundish continuous casting furnaces is increased by more than 55%, the number of inclusions larger than 5 μm in the ingot is reduced by more than 57%, the consumption of modifiers is reduced, and product quality and production efficiency are improved.

[0144] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for smelting high-cleanliness steel, characterized in that: The following steps are involved: A) Converter process: Before tapping, the inclusion modifier slurry is applied to the ladle wall, and then the steel is tapped and deoxidized and alloyed; in, The inclusion modifier slurry comprises powder and solvent; In terms of mass percentage, the powder comprises the following components: CaO: 61%~79%; Al2O3: 15.5%~19.5%; SiO2: 0%~4.5%; MgO: 0%~4.5%; C：5.1％～9.5％； The rest are unavoidable impurities; B) Argon blowing process: After the steel is tapped in step A), argon is blown from the bottom of the ladle; C) Continuous Casting Process: After the argon blowing process in step B) is completed, continuous casting is carried out; wherein the continuous casting ladle is opened for pouring and draining accompanied by argon blowing.

2. The smelting method according to claim 1, characterized in that: The powder is prepared by the following preparation method: S1, melting a CaO raw material, an Al2O3 raw material, a SiO2 raw material and a MgO raw material to form a pre-molten slag; S2, mixing and grinding the pre-melted slag and carbon powder to obtain powder.

3. The smelting method according to claim 1, characterized in that: The fineness of the powder is 700nm-50μm.

4. The smelting method according to claim 1, characterized in that: In the inclusion modifier slurry, the mass of the solvent is 35% to 60% of the mass of the powder.

5. The smelting method according to claim 1 or 4, characterized in that: The solvent is water; After the inclusion modifier slurry is coated on the ladle wall, baking is also performed; the baking temperature is 900-1100° C. and the time is 24-48 hours.

6. The smelting method according to claim 1, characterized in that: In step A), the coating thickness is 5 to 12 mm.

7. The smelting method according to claim 1, characterized in that: In step A), the process of tapping and deoxidation alloying specifically includes: adding aluminum-iron alloy and inclusion modifier balls into the ladle when 1 / 7 to 1 / 6 of the steel is tapped, and then adding other ferroalloys to alloy the molten steel after 20 to 40 seconds; Wherein, the inclusion modifier ball includes powder; In terms of mass percentage, the powder comprises the following components: CaO: 61%~79%; Al2O3: 15.5%~19.5%; SiO2: 0%~4.5%; MgO: 0%~4.5%; C：5.1％～9.5％； The rest are inevitable impurities.

8. The smelting method according to claim 7, characterized in that: The amount of inclusion modifier balls added is 0.5-2.5 kg / t steel; The inclusion modifier ball is prepared by the following preparation method: powder, binder and water are mixed, pressed into balls, and dried to obtain the inclusion modifier ball.

9. The smelting method according to claim 1, characterized in that: In step B), the flow rate of bottom blowing argon is 120-150 NL / min, and the time is 5-8 min.

10. The smelting method according to claim 1, characterized in that: In step C), the argon blowing includes: after the ladle starts pouring, the argon blowing flow rate of the ladle bottom is 120-150NL / min, when the ladle is poured 1 / 4-1 / 3, the argon blowing flow rate of the ladle bottom is reduced to 80-120NL / min, and when the ladle pouring amount is 2 / 3-3 / 4, the bottom argon blowing is turned off.

Images