Smelting method of clean steel

Abstract

The invention belongs to the technical field of smelting, and particularly relates to a smelting method of clean steel. Specifically, the smelting method is a method for controlling oxygen and phosphorus components of clean steel at the same time, and metal Zr is added in the RH vacuum refining process to serve as a phosphorus and oxygen element content control agent, so that the two purposes of deoxidation and dephosphorization in molten steel can be achieved at the same time. The smelting method is easy and convenient to operate, and the smelting yield can be effectively increased.

Description

Technical Field

[0001] The invention belongs to the technical field of smelting, and in particular relates to a method for smelting clean steel. Background Art

[0002] The clean steel in the present invention is also called high-C ultra-low-S, low-P, and low-Al steel, and generally requires the content of some non-ferrous elements therein to be: carbon (C): about 0.05 to about 0.80 mass%, sulfur (S): about ≤0.0012 mass%, aluminum (Al): about ≤0.008 mass%, phosphorus (P): about ≤0.003 mass%, and total oxygen (O): about ≤0.0025 mass%.

[0003] This type of steel is generally produced by converter smelting + LF (Ladle Furnace) refining + RH (Ruhrstahl and Hereaeus) vacuum refining + continuous casting process. Since the finished steel is not required to have too much sulfur, desulfurization is required during the production process, and a large amount of Al needs to be added during desulfurization. Specifically, after the converter is tapped, the molten steel is deeply desulfurized with Al in the LF furnace. The strong reducing conditions in the LF furnace will cause the molten steel that has been dephosphorized in the converter to rephosphorize to a certain extent, resulting in the phosphorus content in the molten steel out of the LF furnace exceeding the standard, and it cannot be reduced during RH refining, resulting in a downgrade.

[0004] In addition, the finished clean steel product is required not to contain too much Al, and oxygen needs to be used to remove the excess Al during the smelting process. Therefore, after LF furnace refining, during RH vacuum refining, it is necessary to blow in excess oxygen relative to the residual Al in the molten steel to oxidize the Al in the steel. However, the oxygen content in the finished steel is required to be very low. It is well known that when there is no Al in the molten steel, the oxygen content in the steel will increase relatively. This will cause the oxygen in the finished steel to exceed the standard requirements and be reduced during continuous casting production due to poor refractory materials or protective casting. This makes the production of clean steel extremely difficult. Summary of the invention

[0005] Purpose of the Invention In view of the problems existing in the prior art described in the above background technology part, an object of the present invention is to provide a method for smelting clean steel.

[0006] Technical Solution In order to achieve the above object, the present invention adopts the following technical solutions: Scheme 1: A method for smelting clean steel, wherein the clean steel comprises, by mass percentage: about 0.05 to about 0.80 mass % of C element, About 0.05 to about 1.20 mass % of Si element, And the balance of iron (Fe) and inevitable impurity elements, Among them, as unavoidable impurity elements The content of S is about 0.0012 mass % or less, preferably about 0.0010 mass % or less, The Al content is about 0.008 mass % or less, preferably about 0.007 mass % or less, The content of O is less than about 0.0025 mass %, and The content of P is less than about 0.003 mass %, The smelting method comprises providing crude molten steel, LF furnace refining, RH refining and continuous casting steps, wherein metal zirconium (Zr) is used as a phosphorus and oxygen content controller in the RH refining step.

[0007] Aspect 2: The smelting method according to aspect 1 above, wherein the content of manganese (Mn), an unavoidable impurity element, contained in the clean steel is about 0.05 mass % or less.

[0008] Scheme 3: The smelting method according to Scheme 1 or 2 above, wherein the smelting method comprises the following steps: Step 1: providing crude molten steel, wherein the crude molten steel comprises, by mass percentage: about 0.05 to about 0.80 mass % of C element, About 0.05 to about 1.20 mass % of Si element, About 0.015 mass % or less of S element, and About 0.0025 mass % or less of P element; Step 2: subjecting the crude molten steel from step 1 to LF furnace refining, adding metal Al during the LF furnace refining process, so that the molten steel after the LF furnace refining contains, by mass percentage: About 0.05 to about 0.80 mass % or less of C element, About 0.05 to about 1.20 mass % of Si element, About 0.0012 mass % or less, preferably about 0.0010 mass % or less of S element, About 0.0035 mass % or less of P element, and About 0.010 mass % or more, preferably about 0.010 to 0.020 mass %, more preferably about 0.010 to about 0.018 mass % of Al element; Step 3: The molten steel refined by the LF furnace in step 2 is subjected to RH refining. During the RH refining, a vacuum cycle is first performed for about 3 to about 10 minutes, and then about 1 to about 1.5 Nm Al per kg Al in the molten steel is added. 3Oxygen is blown into the molten steel in an amount of 1000 g / cm2, and then the molten steel is vacuumed for about 3 to about 10 minutes, and then metal Zr is added as a phosphorus and oxygen content controller, so that the molten steel contains the following by mass percentage: about 0.05 to about 0.80 mass % of C element, About 0.05 to about 1.20 mass % of Si element, About 0.0012 mass % or less, preferably about 0.0010 mass % or less of S element, About 0.008 mass % or less, preferably about 0.007 mass % or less of Al element, About 0.003 mass % or less of P element, and About 0.0008 mass % or less of O element, Finally, vacuum cycle for about 4 to about 12 minutes; Step 4: Continuously casting the RH refined molten steel obtained in step 3 to obtain the clean steel.

[0009] Option 4: According to the smelting method described in Option 3 above, the crude molten steel in step 1 contains Mn element in an amount of about 0.05 mass % or less by mass.

[0010] Option 5: A smelting method according to Option 3 or 4 above, wherein the crude molten steel in step 1 is provided by converter smelting.

[0011] Option 6: The smelting method according to any one of options 3 to 5 above, wherein the temperature of the crude molten steel in step 1 is at least about 1630°C.

[0012] Option 7: A smelting method according to any one of the above options 3 to 6, wherein during the LF furnace refining process in step 2, the amount of metallic Al added is at least about 3 kg, preferably about 3 to about 6 kg, per ton of molten steel.

[0013] Solution 8: The smelting method according to any one of the above solutions 3 to 7, wherein the metal Al is used in the form of an aluminum alloy, and the aluminum alloy contains, by mass percentage: about 98% by mass or more, preferably about 99% by mass or more of Al element, and The balance includes Fe, Si, copper (Cu), calcium (Ca), magnesium (Mg) and zinc (Zn), and inevitable impurity elements.

[0014] Option 9: The smelting method according to Option 8 above, wherein the aluminum alloy comprises, by mass percentage: About <0.80 mass% Si element, About <0.05 mass% Cu element, About <0.05 mass% of Ca element, about <0.05 mass% of Mg, and About <0.04 mass% Zn element.

[0015] Scheme 10: A smelting method according to any one of Schemes 3 to 9 above, wherein during the LF furnace refining process in step 2, the temperature of the molten steel is controlled within the range of about 1600 to about 1660°C.

[0016] Scheme 11: A smelting method according to any one of Schemes 3 to 10 above, wherein during the RH refining process of step 3, the amount of metal Zr added is at least about 0.15 kg per ton of molten steel, preferably about 0.15 to about 0.70 kg.

[0017] Scheme 12: A smelting method according to any one of Schemes 3 to 11 above, wherein during the RH refining process of step 3, the temperature of the molten steel is controlled within the range of about 1530 to about 1600°C.

[0018] Scheme 13: A smelting method according to any one of the above schemes 1 to 12, wherein the metal Zr as a phosphorus and oxygen content controller is used in the form of a zirconium alloy, and the zirconium alloy contains, by mass percentage: about 90% by mass or more, preferably about 99% by mass or more, of Zr, and The balance is Fe, tin (Sn), chromium (Cr) and nickel (Ni) elements, and inevitable impurity elements.

[0019] Option 14: According to the smelting method described in Option 13 above, the content of unavoidable impurity elements in the zirconium alloy is each less than about 0.1% by mass. Technical Effects The clean steel smelting method provided by the present invention is a method for simultaneously controlling the oxygen and phosphorus components of clean steel. Specifically, the present invention provides a composition control method for double dephosphorization and deoxidation using metal Zr in the smelting process of clean steel. Adding metal Zr as a phosphorus and oxygen element content control agent during RH vacuum refining can achieve simultaneous reduction of oxygen and phosphorus in steel. The production method of the present invention is simple to operate and can effectively improve the smelting rate. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without paying creative work belong to the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on normal conditions.

[0021] The endpoints of the scope disclosed in the present invention and any value are not limited to this accurate scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. The term "about" used in the present invention represents that the numeral modified by it can fluctuate within the range of ± 20%, ± 15%, ± 10%, ± 5% or ± 2% of this numeral. For numerical range, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between the separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in the present invention.

[0022] The present invention provides a clean steel smelting method, which is a composition control method for double dephosphorization and deoxidation of clean steel.

[0023] The clean steel targeted by the smelting method of the present invention comprises, by mass percentage: about 0.05 to about 0.80 mass %, for example, about 0.10 mass %, about 0.20 mass %, about 0.30 mass %, about 0.40 mass %, about 0.50 mass %, about 0.60 mass % or about 0.70 mass % of the C element, About 0.05 to about 1.20 mass %, for example, about 0.10 mass %, about 0.30 mass %, about 0.50 mass %, about 0.70 mass %, about 0.90 mass %, about 1.00 mass % or about 1.10 mass % of silicon (Si) element, And the balance of Fe and unavoidable impurity elements, Among them, as unavoidable impurity elements The content of S is about 0.0012 mass % or less, preferably about 0.0010 mass % or less, The Al content is about 0.008 mass % or less, preferably about 0.007 mass % or less, The content of O is less than about 0.0025 mass %, and The P content is about 0.003 mass % or less.

[0024] In some preferred embodiments of the present invention, the clean steel targeted by the smelting method of the present invention may further contain Mn as an unavoidable impurity element. In this case, the content of Mn is generally below about 0.05 mass %.

[0025] In order to achieve the element content requirements of clean steel as described above, metal Zr needs to be used as a phosphorus and oxygen content controller in the smelting method of the present invention. Specifically, the smelting method generally may include providing crude molten steel, LF furnace refining, RH refining and continuous casting steps, wherein metal Zr is used as a phosphorus and oxygen content controller in the RH refining step.

[0026] In an exemplary embodiment of the present invention, the clean steel smelting method of the present invention includes the following steps 1 to 4.

[0027] The step 1 comprises providing crude molten steel, wherein the crude molten steel comprises, by mass percentage: about 0.05 to about 0.80 mass %, for example, about 0.10 mass %, about 0.20 mass %, about 0.30 mass %, about 0.40 mass %, about 0.50 mass %, about 0.60 mass % or about 0.70 mass % of the C element, about 0.05 to about 1.20 mass %, for example, about 0.10 mass %, about 0.30 mass %, about 0.50 mass %, about 0.70 mass %, about 0.90 mass %, about 1.00 mass % or about 1.10 mass % of Si element, about 0.015 mass % or less, for example about 0.012 mass % or less, preferably about 0.009 mass % or less of S element, and About 0.0025 mass % or less of the P element.

[0028] In fact, the crude molten steel provided by the present invention is always mixed with a small amount of slag produced in the process of roughing the molten steel, so the crude molten steel mentioned in the present invention refers to the molten steel mixed with the slag.

[0029] In some exemplary embodiments, the crude molten steel provided in step 1 may further contain, for example, 0.05 mass % or less of Mn element as an unavoidable impurity.

[0030] Here, the P content in the crude steel water of step 1 is about 0.0025% by mass or less, which is lower than the P content of about 0.003% by mass or less required in the finished steel. There are many causes for the phenomenon of increased phosphorus content in this finished steel, such as the presence of phosphorus-containing impurities in the materials added later, and the corrosion of phosphorus-containing refractory materials into the molten steel. However, the main reason is that during the LF furnace refining process, the phosphorus-containing slag remaining in the molten steel provided by the converter may be dissolved in the molten steel again under the reducing conditions of the LF furnace, and "rephosphorization" occurs, thereby increasing the phosphorus content in the molten steel at the end of the LF furnace smelting.

[0031] In some exemplary embodiments, the crude molten steel provided in step 1 may be, for example, molten steel provided by converter smelting. In addition, some metal Al may be added during the converter smelting process in step 1 to control the oxidizing atmosphere and prevent important elements such as Fe and C in the molten steel from being oxidized. In some exemplary embodiments of the present invention, the Al content in the crude molten steel is controlled to be less than about 0.05 mass %, for example, between about 0.03 mass % and about 0.04 mass %.

[0032] Generally, the crude molten steel provided in step 1 may have a temperature of about 1630° C. or above.

[0033] The step 2 comprises subjecting the crude molten steel from the step 1 to LF furnace refining, wherein metal Al needs to be added during the refining process to reduce the sulfur content in the molten steel to below the desired value. For example, after the LF furnace refining, the molten steel preferably contains, by mass percentage: about 0.05 to about 0.80 mass %, for example, about 0.10 mass %, about 0.20 mass %, about 0.30 mass %, about 0.40 mass %, about 0.50 mass %, about 0.60 mass % or about 0.70 mass % of the C element, about 0.05 to about 1.20 mass %, for example, about 0.10 mass %, about 0.30 mass %, about 0.50 mass %, about 0.70 mass %, about 0.90 mass %, about 1.00 mass % or about 1.10 mass % of Si element, About 0.0012 mass % or less, preferably about 0.0010 mass % or less, for example, about 0.0008 mass % or less of the element S, About 0.0035 mass % or less of P element, and About 0.010 mass % or more, preferably about 0.010 to 0.020 mass %, more preferably about 0.010 to 0.018 mass % of Al element.

[0034] Here, generally speaking, the reference standard of Al addition is first calculated based on the sulfur content in molten steel, but in reality, the amount of Al added is much greater than the standard amount. As mentioned above, the extremely low sulfur content of the clean steel is the standard to be achieved first, so the added Al is preferably significantly excessive, otherwise it may easily lead to an excessively high sulfur content in the obtained steel, resulting in a reduction in judgment and a significant increase in production costs.

[0035] For example, in an exemplary embodiment of the present invention, during the LF furnace refining process of step 2, the amount of metallic Al added to the crude molten steel obtained from step 1 above is set to at least about 3 kg, such as about 4 kg, about 5 kg or about 6 kg per ton of molten steel.

[0036] In the molten steel obtained in step 2, the content of Al element should be maintained at more than about 0.010 mass % to ensure that the S element in the molten steel is removed as completely as possible after smelting in the LF furnace. However, the content of Al element should not be too high, for example, it should not exceed about 0.020 mass %, preferably should not exceed about 0.014 mass %, about 0.015 mass % or about 0.018 mass %, otherwise more oxygen needs to be introduced in the subsequent RH process to remove the excess Al element, which on the one hand leads to an increase in production costs, and on the other hand may also lead to excessive resulfurization.

[0037] In a particularly preferred embodiment of the present invention, the metal Al is used in the form of an aluminum alloy, wherein the aluminum alloy contains, by mass percentage: about 98% by mass or more, preferably about 99% by mass or more of Al element, and The balance is Fe, Si, Cu, Ca, Mg and Zn elements, and inevitable impurity elements.

[0038] In a further preferred embodiment, the aluminum alloy comprises, by mass percentage: <0.80 mass% Si element, <0.05 mass% Cu element, <0.05 mass% Ca element, <0.05 mass% of Mg element, and <0.04 mass% Zn element.

[0039] The step 3 includes subjecting the molten steel from the above step 2 to RH refining.

[0040] The RH refining process includes blowing oxygen into the molten steel after a vacuum cycle of about 3 to about 10 minutes, then vacuuming for another 3 to about 10 minutes, adding metal Zr as a phosphorus and oxygen content controller, and finally vacuuming for another 4 to 12 minutes.

[0041] During the RH refining, the amount of oxygen blown into the molten steel is about 1 to about 1.5 Nm / kg Al element in the molten steel. 3 Here, the amount of oxygen blown in should not be too large, for example, should not exceed about 1.5 Nm 3 / kgAl, otherwise too much oxygen may lead to excessive resulfurization on the one hand, and may also lead to excessive metal Zr required for subsequent deoxygenation on the other hand, which will increase the cost; the amount of oxygen blown in should not be too low, for example, it should not be less than about 1 Nm 3 / kgAl, otherwise the excess oxygen will be insufficient, which may lead to insufficient removal of Al element in the molten steel and excessive Al element in the finished steel.

[0042] In addition, during the RH refining process, the amount of metal Zr added as a phosphorus and oxygen content controller is such that the molten steel contains, by mass percentage: about 0.05 to about 0.80 mass %, for example, about 0.10 mass %, about 0.20 mass %, about 0.30 mass %, about 0.40 mass %, about 0.50 mass %, about 0.60 mass % or about 0.70 mass % of the C element, about 0.05 to about 1.20 mass %, for example, about 0.10 mass %, about 0.30 mass %, about 0.50 mass %, about 0.70 mass %, about 0.90 mass %, about 1.00 mass % or about 1.10 mass % of Si element, About 0.0012 mass % or less, preferably about 0.0010 mass % or less of S element, About 0.008 mass % or less, preferably about 0.007 mass % or less of Al element, About 0.003 mass % or less of P element, and About 0.0008 mass % or less of O element.

[0043] Here, generally speaking, the amount of oxygen and phosphorus in the molten steel can be used as a reference standard for the amount of Zr added. However, in reality, the amount of Zr added will be greater than the standard amount. As mentioned above, the oxygen and phosphorus content of the clean steel is the standard to be reached first. Therefore, the added Zr is preferably excessive, otherwise it may easily lead to excessive oxygen and phosphorus content in the resulting steel, resulting in a reduction in judgment and greatly increasing production costs. However, although the presence of the Zr element will greatly improve the performance of the finished steel, the cost of adding Zr must also be considered.

[0044] For example, in an exemplary embodiment of the present invention, during the RH refining process of step 3, the amount of metal Zr added to the oxygen-blown molten steel is at least about 0.15 kg per ton of molten steel, such as about 0.2 kg, about 0.3 kg, about 0.4 kg, about 0.5 kg, about 0.6 kg or about 0.7 kg. Here, on the one hand, the amount of Zr added should not be less than about 0.15 kg per ton of molten steel, otherwise the dideoxidation and dephosphorization effect on the molten steel may not be sufficient; on the other hand, the amount of Zr added should not be too high, for example, it should not be higher than about 0.7 kg per ton of molten steel, because Zr metal is expensive, and excessive use causes a significant increase in production costs.

[0045] In a particularly preferred embodiment of the present invention, the metal Zr is used in the form of a zirconium alloy, wherein the zirconium alloy contains, by mass percentage: about 90% by mass or more, preferably about 95% by mass or more, more preferably about 99% by mass or more of Zr element, and The balance is Fe, Sn, Cr and Ni elements, and inevitable impurity elements, wherein the content of each of the inevitable impurity elements is preferably less than 0.1% by mass.

[0046] For example, in some specific exemplary embodiments, the metallic Zr may be used in the form of Zr-1, R60700, Zr-3 and / or R60702.

[0047] In addition, in the molten steel obtained in step 3, the content of oxygen element should be maintained below about 0.0008 mass % to ensure that when the molten steel is continuously cast later, the steel will not have an excessive oxygen content in the finished product due to the inevitable addition of a small amount of oxygen.

[0048] It should also be noted that the time and temperature of the RH furnace refining process generally vary greatly due to different carbon mass percentages in the steel, and those skilled in the art can adjust the relevant parameters according to the actual conditions of the element content in the molten steel. For example, in some exemplary embodiments of the present invention, the temperature of the molten steel refined in the RH furnace is controlled within a range of about 1530°C to 1600°C, and the time of the refining process is mainly determined by the molten steel composition to be limited. It will not be stopped until it reaches a predetermined range.

[0049] The step 4 comprises continuously casting the molten steel obtained from the step 3 to obtain the clean steel.

[0050] The present invention is further described in detail below with reference to specific embodiments and comparative examples.

[0051] Example 1 Clean steel is produced based on a converter output of 80 tons, using the following process route: converter smelting → LF refining → RH vacuum refining → continuous casting.

[0052] (1) Steelmaking in a converter, wherein the mass percentage content of each element in the crude molten steel made from the converter is as follows: It should be noted that the converter mainly has an oxidizing atmosphere, and a large amount of oxygen will be top-blown for dephosphorization. At this time, Al is added to control the oxidizing atmosphere to prevent important elements such as Fe and C in the molten steel from being oxidized, which is not helpful for desulfurization.

[0053] (2) LF deep desulfurization, in which the Al content is at least 99.7% by mass of metallic Al is added during the LF furnace refining process. The amount added can be determined based on the composition obtained by sampling and testing during the smelting process. The specific amount added is about 4.5 kg Al per ton of molten steel. The mass percentage content of each element in the molten steel after leaving the station is as follows: From the data in the table above, it can be seen that the C content may be slightly increased due to the peeling of graphite electrodes during LF furnace smelting. In addition, due to the reducing atmosphere in the LF furnace, some elements Mn, Si and P in the slag return to the molten steel, so the content of Mn, Si and P also increases slightly. Among them, the reflux of phosphorus has a greater impact on the molten steel, so it needs to be controlled in the subsequent process steps.

[0054] In addition, since there is no oxygen in the LF furnace, the atmosphere becomes a reducing atmosphere, and the Al element begins to remove S in the molten steel.

[0055] (3) Entering the RH station, during the RH refining process, after 3 minutes of vacuum circulation, the pressure is about 1Nm per kg of Al in the molten steel. 3 Oxygen is blown into the molten steel in an amount of about 1000 μg / m2, and then the vacuum cycle is carried out for about 3 minutes. At this time, the fixed oxygen value is about 18 mass ppm. Then, zirconium alloy Zr-1 with a Zr content of more than 99 mass % is added in an amount of about 0.30 kg per ton of molten steel to control the end-point composition. The vacuum cycle is carried out for about 6 minutes. The mass percentage content of each element after the molten steel leaves the station is as follows: The removal of S element usually needs to be carried out in a reducing atmosphere, while the oxidizing atmosphere in the RH refining process will cause a small amount of S element in the slag to re-enter the molten steel, which may cause the S element content here to increase slightly.

[0056] (4) Continuous casting, wherein the mass percentage content of each element in the finished steel billet after continuous casting is as follows: It can be seen from the data in the above table that some oxygen will inevitably be mixed into the molten steel during continuous casting, which will cause the Al and Zr elements to be oxidized and separated from the molten steel system, possibly forming inclusions, and at the same time increasing the oxygen content.

[0057] Example 2 Clean steel is produced based on a converter output of 200 tons, and the process route adopted is converter smelting → LF refining → RH vacuum refining → continuous casting.

[0058] (1) Steelmaking in a converter, wherein the mass percentage content of each element in the crude molten steel made from the converter is as follows: It should be noted that the converter mainly has an oxidizing atmosphere, and a large amount of oxygen will be top-blown for dephosphorization. At this time, Al is added to control the oxidizing atmosphere to prevent important elements such as Fe and C in the molten steel from being oxidized, which is not helpful for desulfurization.

[0059] (2) LF deep desulfurization, in which Al content of at least 99.7% by mass of metallic Al is added during the LF furnace refining process. The amount of Al added can be determined based on the composition obtained by sampling and testing during the smelting process. The specific amount of Al added is about 5 kg Al per ton of molten steel. The mass percentage content of each element in the molten steel after leaving the station is as follows: From the data in the table above, it can be seen that the C content may be slightly increased due to the peeling of graphite electrodes during LF furnace smelting and the addition of carbon alloy to increase carbon. In addition, due to the reducing atmosphere in the LF furnace, some elements Mn, Si and P in the slag return to the molten steel, and the content of Mn, Si and P also increases. Among them, the reflux of phosphorus has a greater impact on the molten steel, so it needs to be controlled in the subsequent process steps.

[0060] In addition, since there is no oxygen in the LF furnace, the atmosphere becomes a reducing atmosphere, and the Al element begins to remove S in the molten steel.

[0061] (3) Entering the RH station, during the RH refining process, after 4 minutes of vacuum circulation, the pressure is about 1.2 Nm per kg of Al in the steel. 3 Oxygen was blown into the molten steel in an amount of about 100%, and the vacuum cycle was continued for about 4 minutes. At this time, the fixed oxygen value was about 16 mass ppm. Zirconium alloy R60702 (sponge Zr) with a Zr content of more than 99 mass % was added in an amount of about 0.25 kg per ton of molten steel for endpoint composition control. The vacuum cycle was continued for about 8 minutes. The mass percentage content of each element after the molten steel left the station is as follows: The removal of S element needs to be carried out in a reducing atmosphere, while the oxidizing atmosphere in the RH refining process will cause a small amount of S element in the slag to re-enter the molten steel, which may cause the S element content here to increase slightly.

[0062] (4) Continuous casting, wherein the mass percentage content of each element in the finished steel billet after continuous casting is as follows: From the data in the table above, it can be seen that some oxygen will inevitably be mixed into the molten steel during continuous casting, which will cause Al and Zr elements to be oxidized and separated from the molten steel system, which may form inclusions and increase the oxygen content. In addition, the changes in the content of C, Mn and Si elements may be caused by measurement errors or the shedding of refractory materials in the tundish.

[0063] Comparative Example 1 Clean steel is produced based on a converter output of 80 tons, using the following process route: converter smelting → LF refining → RH vacuum refining → continuous casting.

[0064] (1) Steelmaking in a converter, wherein the mass percentage content of each element in the crude molten steel made from the converter is as follows: (2) LF deep desulfurization, in which the Al content is at least 99.7% by mass of metallic Al is added during the LF furnace refining process. The amount added can be determined based on the composition obtained by sampling and testing during the smelting process. The specific amount added is about 4.5 kg Al per ton of molten steel. The mass percentage content of each element in the molten steel after leaving the station is as follows: (3) Entering the RH station, during the RH refining process, after 3 minutes of vacuum circulation, the pressure is about 1Nm per kg of Al in the molten steel. 3 The oxygen is blown into the molten steel in an amount of about 100%, and then the vacuum cycle is carried out for about 3 minutes. At this time, the fixed oxygen value is about 18 mass ppm. Then, about 0.04 kg of barium-magnesium alloy is added per ton of molten steel for final deoxidation. The vacuum cycle is carried out for about 6 minutes. The mass percentage content of each element after the molten steel leaves the station is as follows: (4) Continuous casting, wherein the mass percentage content of each element in the finished steel billet after continuous casting is as follows: Comparative Example 2 Clean steel is produced based on a converter output of 200 tons, and the process route adopted is converter smelting → LF refining → RH vacuum refining → continuous casting.

[0065] (1) Steelmaking in a converter, wherein the mass percentage content of each element in the crude molten steel made from the converter is as follows: (2) LF deep desulfurization, in which Al content of at least 99.7% by mass of metallic Al is added during the LF furnace refining process. The amount of Al added can be determined based on the composition obtained by sampling and testing during the smelting process. The specific amount of Al added is about 5 kg Al per ton of molten steel. The mass percentage content of each element in the molten steel after leaving the station is as follows: (3) Entering the RH station, during the RH refining process, after 4 minutes of vacuum circulation, the pressure is about 1.2 Nm per kg of Al in the steel. 3 The oxygen is blown into the molten steel in an amount of about 100%, and the vacuum cycle is continued for about 4 minutes. At this time, the fixed oxygen value is about 16 mass ppm. About 0.06 kg of barium-magnesium alloy is added per ton of molten steel to control the end point composition. The vacuum cycle is continued for about 8 minutes. The mass percentage content of each element after the molten steel leaves the station is as follows: (4) Continuous casting, wherein the mass percentage content of each element in the finished steel billet after continuous casting is as follows: From the comparison of the results of the above Examples 1 to 2 with Comparative Examples 1 to 2, it can be seen that in the smelting process of the present invention, the use of zirconium alloy as a phosphorus and oxygen content controller in the RH refining step achieves the purpose of double dephosphorization and deoxidation in the clean steel smelting process, while the magnesium-barium alloy used in the comparative example can only achieve the purpose of deoxidation and has no effect on removing the phosphorus content.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions claimed to be protected by the present invention.

Claims

1. A method for smelting clean steel, wherein the clean steel comprises, by mass percentage: 0.05 to 0.80 mass% of C element, 0.05 to 1.20 mass% of Si element, And the balance of Fe and unavoidable impurity elements, Among them, as unavoidable impurity elements The S content is 0.0012 mass % or less, The Al content is less than 0.008 mass %, The content of O is 0.0025 mass % or less, and The content of P is less than 0.003 mass %, It is characterized in that The smelting method comprises providing crude molten steel, LF furnace refining, RH refining and continuous casting steps, wherein metal Zr is used as a phosphorus and oxygen content controller in the RH refining step.

2. The smelting method according to claim 1, characterized in that: The content of Mn as an inevitable impurity element contained in the clean steel is 0.05 mass % or less.

3. The smelting method according to claim 1, characterized in that: The smelting method comprises the following steps: Step 1: providing crude molten steel, wherein the crude molten steel comprises, by mass percentage: 0.05 to 0.80 mass% of C element, 0.05 to 1.20 mass% of Si element, 0.015 mass% or less of S element, and 0.0025 mass% or less of P element; Step 2: subjecting the crude molten steel from step 1 to LF furnace refining, adding metal Al during the LF furnace refining process, so that the molten steel after the LF furnace refining contains, by mass percentage: 0.05 to 0.80 mass % or less of C element, 0.05 to 1.20 mass% of Si element, 0.0012 mass% or less of S element, 0.0035 mass% or less of P element, and 0.010 mass % or more of Al element; Step 3: The molten steel refined by the LF furnace in step 2 is subjected to RH refining. During the RH refining, a vacuum cycle is first performed for 3 to 10 minutes, and then 1 to 1.5 Nm Al per kg Al in the molten steel is added. 3 Oxygen is blown into the molten steel in an amount of 200 μg / min, and then the molten steel is vacuumed for 3 to 10 minutes, and then metal Zr is added as a phosphorus and oxygen content controller, so that the molten steel contains the following by mass percentage: 0.05 to 0.80 mass% of C element, 0.05 to 1.20 mass% of Si element, 0.0012 mass% or less of S element, 0.008 mass % or less of Al element, 0.003 mass% or less of P element, and 0.0008 mass % or less of O element, Finally, vacuum cycle for another 4 to 12 minutes; Step 4: Continuously casting the RH refined molten steel obtained in step 3 to obtain the clean steel.

4. The smelting method according to claim 3, characterized in that: The crude molten steel in step 1 contains 0.05 mass % or less of Mn element in terms of mass percentage; and / or The crude molten steel in step 1 is provided by converter smelting; and / or The temperature of the crude molten steel in step 1 is at least 1630°C.

5. The smelting method according to claim 3, characterized in that: During the LF furnace refining process in step 2, the amount of added metal Al is at least 3 kg per ton of molten steel; and / or The metal Al is used in the form of an aluminum alloy, wherein the aluminum alloy contains, by mass percentage: 98 mass % or more of Al, and The balance is Fe, Si, Cu, Ca, Mg and Zn elements, and inevitable impurity elements.

6. The smelting method according to claim 3, characterized in that: During the LF furnace refining process in step 2, the temperature of the molten steel is controlled within the range of 1600 to 1660°C.

7. The smelting method according to claim 3, characterized in that: During the RH refining process of step 3, the amount of added metal Zr is at least 0.15 kg per ton of molten steel.

8. The smelting method according to claim 3, characterized in that: During the RH refining process of step 3, the temperature of the molten steel is controlled within the range of 1530 to 1600°C.

9. The smelting method according to any one of claims 1 to 8, characterized in that: The metal Zr as the phosphorus and oxygen content controller is used in the form of a zirconium alloy, and the zirconium alloy contains, by mass percentage: 90 mass % or more of Zr element, and The balance is Fe, Sn, Cr and Ni elements, and inevitable impurity elements.

10. The smelting method according to claim 9, characterized in that: The contents of inevitable impurity elements in the zirconium alloy are each less than 0.1% by mass.

Images