Method for hot rolling steel products

Abstract

A method for hot rolling a steel semi-finished product, comprising the step of producing molten steel, wherein the production step comprises melting steel scrap containing copper, estimating the amounts of copper %Cuest, and optionally tin %Snest, antimony %Sbest, and sulfur %Sest in the produced molten steel, casting the molten steel to produce a semi-finished product, reheating the semi-finished product to a reheating temperature TR, and hot rolling the reheated semi-finished product. The method further comprises calculating optimized amounts of tin, antimony, and sulfur.

Description

[Technical Field]

[0001] This invention relates to a method for hot-rolling steel products, wherein the steel is manufactured using steel scrap. [Background technology]

[0002] Steelmaking requires the use of iron-containing materials such as scrap, directly reduced iron (DRI), or pig iron. Today, scrap is commonly used in the steelmaking process to produce molten steel. The scrap can be used at different stages and with different steelmaking tools along the steelmaking process. Converters, basic oxygen furnaces (BOF), electric arc furnaces (EAF), and molten furnaces (SF) are some of the tools that can be used in production, particularly in steelmaking.

[0003] There is a global trend towards using more scrap in steel production to reduce the CO2 footprint of global steelmaking processes. However, such scrap can be of different types, particularly depending on its origin, and therefore can have different qualities, especially in terms of shape, density, chemical properties, and the presence of impurities. Steel scrap contains residual elements such as copper, chromium, molybdenum, nickel, tin, antimony, zinc, and / or arsenic. Therefore, the use of steel scrap is not widespread for all steel grades because these residual elements can have detrimental effects on the properties of the steel.

[0004] When steel is produced using directly reduced iron and / or pig iron, small amounts of residual elements inevitably remain in the molten metal. When steel scrap is used, the amount of residual elements is much greater than in the case of pig iron or directly reduced iron coming from a blast furnace.

[0005] Recently, the inventors have observed that when steel is produced using a considerable amount of steel scrap, problems arise during several manufacturing steps, such as hot rolling.

[0006] Among the impurities contained in steel scrap, the impurity that is difficult to remove in the steelmaking process is copper. Copper is more noble than iron, and is enriched at the interface between steel and iron oxide when iron is oxidized at high temperature. The copper-rich liquid phase formed in this manner, also referred to as a copper phase, eventually penetrates the steel along austenite grain boundaries, weakens the bonds, and induces surface cracking during hot working. This cracking phenomenon is known as hot brittleness. SUMMARY OF THE INVENTION

[0007] Accordingly, there is a need for a method of producing hot-rolled steel using steel scrap, in which the risk of hot brittleness is reduced and further suppressed. i) This problem is solved by the method according to the present invention, the method comprising the step of producing molten steel, wherein said producing step comprises melting steel scrap containing copper, the step of estimating the copper content %Cu in the produced molten steel est , the step of casting the molten steel to produce a semi-finished product, and the step of reheating the semi-finished product to a reheating temperature T R , the step of hot rolling the reheated semi-finished product, and between the estimating step and the casting step, calculating an optimized amount of tin %Sn Opt , antimony %Sb Opt and sulfur %S Opt , wherein said optimized amount satisfies the formula α(T R ).%Sn Opt +ε(T R ).%Sb Opt +η(T R ).%S Opt +Δ(T R )≧%Cu est , wherein in the formula, α(T R ), ε(T R ), η(T R ) are coefficients representing the respective effects of tin, antimony, and sulfur on the solubility of copper at the reheating temperature T R , and Δ(T R ) is a coefficient related to the solubility of copper at the reheating temperature T RA step is performed to adjust the final amounts of tin, antimony, and sulfur in the molten steel to match the step, which is a coefficient representing the effect of the calculated optimized amount.

[0008] The method of the present invention may also include the following optional features, which may be considered separately or in all possible technical combinations: - The molten steel produced contains at least 0.1% copper by weight, -In the manufacturing step, the scrap is melted with molten iron and / or directly with reduced iron. - The estimation step includes estimating the amounts of tin (%Sn), antimony (%Sb), and sulfur (%S) in the molten steel to be produced. - The resulting molten steel has the following composition: %Sb≦0.01%, %As≦0.1%, %Sn≦0.05%, %Si≦0.9%, %Ni≦4.5%, %P≦0.46%, %S≦0.008%, %Mo≦2.2%, %Cr≦4.5%, %Mn≦2.5%, %Al≦0.6%, %C≦0.21%, %Nb≦0.21%, %Ti≦0.21%, %V≦0.21%, %B≦0.002%, and %Cu≧0.1%, with the remainder being iron and unavoidable impurities, all amounts expressed in weight percent. - The amount of copper in the molten steel is 0.1 to 0.3% by weight. -Reheating temperature T R The temperature range is 1100℃ to 1350℃. - The semi-finished product is a slab. -α(T R )=-0.0003752.T R -0.112106, ε(T R )=0.00044767.T R -1.53167, η(T R )=-0.0016517.T R +1.02667 and Δ(T R )=0.0001998.T R The value is -0.04817. - The estimation step is carbon %C est Boron %B est Aluminum %Al est and vanadium %V estFurther including estimation of the quantity, - The calculation step is optimized for the amount of carbon %C Opt Aluminum %Al Opt Boron %B Opt and vanadium %V Opt The calculation includes the following, and the optimized quantity satisfies the following equation: -α(T R ).%Sn Opt +γ(T R ).%C Opt +ε(T R ).%Sb Opt +η(T R ).%S Opt +κ(T R ).%Al Opt +λ(T R ).%V Opt +σ(T R ).%B Opt +Δ(T R )≧%Cu est In the formula, α(T R ), γ(T R ), ε(T R ), η(T R ), κ(T R ), λ(T R ), σ(T R ) is a coefficient that represents the respective influence of tin, carbon, antimony, sulfur, aluminum, vanadium, and boron on the solubility of copper at the reheating temperature, and Δ(T R ) is a coefficient that represents the effect of reheating temperature on the solubility of copper, -α(T R )=-0.0003752.T R -0.112106, γ(T R )=-0.0003549.T R +0.2229, ε(T R )=0.00044767.T R -1.53167, η(T R )=-0.0016517.T R +1.02667, κ(T R )=-0, 0001236.T R +0.12294, λ(T R )=-4.5172E-05.TR +0.02392, σ(T R )=-0.001334.T R +1.5078 and Δ(T R )=0.000393.T R -0.27398 - the estimating step further comprises estimating the amounts of nickel %Ni est , molybdenum %Mo est , manganese %Mn est , silicon %Si est , chromium %Cr est , arsenic %As est , phosphorus %P est , niobium %Nb est , and titanium %Ti est , - the calculating step comprises calculating optimized amounts of tin %Sn Opt , nickel %Ni Opt , molybdenum %Mo Opt , manganese %Mn Opt , carbon %C Opt , antimony %Sb Opt , silicon %Si Opt , sulfur %S Opt , chromium %Cr Opt , aluminum %A Opt l, vanadium %V Opt , arsenic %As Opt , phosphorus %P Opt , niobium %Nb Opt , titanium %Ti Opt , boron %B Opt , wherein the optimized amounts satisfy the following formula, -α(T R ).%Sn Opt +β(T R ).%Ni Opt +χ(T R ).%Mo Opt +δ(T R ).%Mn Opt +γ(T R ).%C Opt +ε(T R ).%Sb Opt +φ(T R ).%Si Opt +η(T R ).%SOpt +φ(T R ).%Cr Opt +κ(T R ).%Al Opt +λ(T R ).%V Opt +μ(T R ).%As Opt +ν(T R ).%P Opt +θ(T R ).%Nb Opt +ρ(T R ).%Ti Opt +σ(T R ).%B Opt +Δ(T R )≧%Cu est In the formula, α(T R ), β(T R ), χ(T R ), δ(T R ), γ(T R ), ε(T R ), φ(T R ), η(T R ), φ(T R ), κ(T R ), λ(T R ), μ(T R ), ν(T R ), θ(T R ), ρ(T R ), σ(T R ) is a coefficient that represents the influence of tin, nickel, molybdenum, manganese, carbon, antimony, silicon, sulfur, chromium, aluminum, vanadium, arsenic, phosphorus, niobium, titanium, and boron on the solubility of copper at the reheating temperature, and Δ(T R This coefficient represents the effect of reheating temperature on the solubility of copper. -α(T R )=-0.0003752.T R -0.112106, β(T R )=-2.395E-05.T R +0.02462, χ(T R )=-0,0002872.T R +0.01797, δ(T R )=-0, 0001287.T R+0.14394, γ(T R )=-0.0003549.T R +0.2229, ε(T R )=0.00044767.T R -1.53167, φ(T R )=-5.6944E-05.T R +0.008839, η(T R )=-0.0016517.T R +1.02667, φ(T R )=5.6556E-06.T R -0.01346, κ(T R )=-0, 0001236.T R +0.12294, λ(T R )=-4.5172E-05.T R +0.02392, μ(T R )=-3.6111E-05.T R +0.04027, ν(T R )=-0,758E-06.T R +0.00343, θ(T R )=-7.033E-06.T R +0.00207, ρ(T R )=1.289E-06.T R +0.01007, σ(T R )=-0.001334.T R +1.5078 and Δ(T R )=0.0008089.T R -0.80722, -In step B, the composition of the molten steel produced is estimated using a model. - The model uses the composition of raw materials containing copper-containing steel scraps, which are molten to produce molten steel, as input data. - The composition of the molten steel is estimated by analyzing a lollipop-type sample of the molten steel.

[0009] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, and are illustrative and not limiting. [Brief explanation of the drawing]

[0010] [Figure 1] This shows a plant that manufactures hot-rolled steel sheets. [Modes for carrying out the invention]

[0011] The elements in the diagram are illustrative and may not be drawn to scale.

[0012] Figure 1 shows a plant for manufacturing hot-rolled steel products. Molten steel 1 contained in a ladle 2 is poured into a tundish 3, which then allows the molten steel to flow through a nozzle into the mold. This molten steel begins to solidify along the casting machine 4, and eventually solidifies completely, is cut, and forms a semi-finished product 5. This semi-finished product 5 is generally left to cool at ambient temperature, stored in a slab yard, and then sent to a hot-rolling plant 6. This hot-rolling plant 6 is equipped with a reheating furnace 7, where the semi-finished product 5 is reheated and then transferred to a rolling mill 8, where it is rolled and transformed into a steel product that is coiled to form hot-rolled steel coils 9.

[0013] Figure 1 shows an embodiment of a plant for manufacturing hot-rolled steel sheets, but the method according to the present invention can be carried out in other plants, enabling the molten steel to be transformed into semi-finished products such as billets, blanks, bars, ingots, slabs, or blooms, and these semi-finished products to be transformed into steel products 9 in a hot-rolling plant 6, which includes a reheating furnace 7 adapted for reheating the semi-finished products 5.

[0014] In another embodiment of a plant for manufacturing hot-rolled steel products, which is not shown here, the cast semi-finished products 5 are sent directly to a hot-rolling plant, where they are subjected to a heating step before rolling. This heating step may be carried out in a tunnel furnace. This plant is called a continuous plant or a direct casting and rolling plant.

[0015] In the method according to the present invention, the production of molten steel 1 involves melting copper-containing steel scrap. Various production routes can be used, and the scrap may be melted in an electric arc furnace (EAF) with pig iron and directly reduced iron (DRI) of any choice, to obtain molten steel which is then subjected to a refining step before being poured into a tundish. The scrap may also be melted in a smelting furnace (SF) with pig iron and / or DRI, and the resulting molten metal is sent to a converter or BOF for decarburization and conversion to molten steel. This molten steel may then be subjected to refining steps such as dephosphorization and / or desulfurization steps and / or secondary metallurgical steps. The scrap may also be fed into a BOF.

[0016] For example, usable scrap steel is referred to in the EU-21 scrap steel specification as old scrap (E1 or E3), new scrap (E8), shredded scrap (E40), or fragmented scrap (E46).

[0017] In the method according to the present invention, the composition of the molten steel produced is estimated to be copper % Cu est Preferably tin %Sn est Antimony %Sb est and sulfur %S est This includes estimating the amount of carbon %C. In a preferred embodiment, the estimate is carbon %C est Boron %B est Aluminum %Al est and vanadium %V est This also includes estimating the amount of nickel. In the most preferred embodiment, this estimation is nickel%Ni est , molybdenum%Mo est Manganese %Mn est chromium%Cr est , silicon %Si est , arsenic %As est , phosphorus%P est Niobium %Nb est and titanium%Ti est This further includes estimation of the quantity. All percentages are expressed as weight percentages.

[0018] The steel composition of the molten steel can be estimated at the end of the refining step and before the casting step. The steel composition is preferably estimated by analyzing lollipop-shaped samples taken from the casting tundish 3 or the ladle 2 used to fill the ingot mold and obtain semi-finished products. This estimation can also be performed using a model.

[0019] Preferably, in step A of molten steel production, 100 to 1000 kg of scrap steel is used per ton of molten iron. Preferably, in step A, 100 to 950 kg of scrap steel is used per ton of molten iron. Preferably, in step A, 100 to 900 kg of scrap steel is used per ton of molten iron. Preferably, in step A, 100 to 800 kg of scrap steel is used per ton of molten iron. Preferably, in step A, 25 kg of scrap steel is used per ton of molten iron, ranging from 100 to 600 kg. Preferably, in step A, 100 to 500 kg of scrap steel is used per ton of molten iron. Even more preferably, in step A, 200 to 400 kg of scrap steel is used per ton of molten iron.

[0020] In this patent, residual elements are undesirable elements derived from steel scrap. Inevitable impurities originate from the refining process, such as oxides and nitrides.

[0021] Once the molten steel is refined, it is poured into a tundish 3 and then cast in a casting machine 4 to produce semi-finished products 5. As previously mentioned, these semi-finished products 5 are generally left to cool to ambient temperature, stored in a warehouse, and then sent to a hot rolling plant 6. After that, the semi-finished products 5 are sent to a reheating furnace 7.

[0022] The use of copper-containing scrap results in the presence of a copper-rich phase on the surface of the semi-finished product. A copper-rich or copper phase refers to a phase containing more than 75% copper by weight, with the remainder being mainly iron and other alloys, as well as residual elements present in the molten steel. This copper-rich phase penetrates the steel along the austenite grain boundaries, causing the problem of hot brittleness.

[0023] Classically, the semi-finished product to be rolled is filled into the inlet of the reheating furnace 7, where it is pushed forward on the hearth by a pusher device. The semi-finished product is typically preheated, heated, and soaked as it passes through the preheating, heating, and soaking zones of the reheating furnace. At the end of the soaking zone of the furnace, the semi-finished product is ejected from the furnace by an ejector for subsequent rolling in the rolling mill. The temperature of the semi-finished product at ejection is T. R The temperature can vary in the range of 1100°C to 1350°C depending on several factors. The reheating furnace 7 is preferably a continuous reheating furnace such as a pusher furnace, a walking hearth furnace, or a walking beam furnace.

[0024] If the manufacturing plant is a continuous plant or a direct casting and rolling plant, the reheating temperature T R This should be understood as the temperature of the semi-finished product 5 at the exit of the heating step before rolling.

[0025] In the method according to the present invention, before casting, an optimized amount of tin %Sn is added so as to satisfy the following formula. Opt Antimony %Sb Opt and sulfur %S Opt This is calculated. (Formula 1)α(T R ).%Sn Opt +ε(T R ).%Sb Opt +η(T R ).%S Opt +Δ(T R )>%Cu est In the formula, α(T R ), ε(T R ) and η(T R ) is a coefficient that represents the respective effects of tin, antimony, and sulfur on the solubility of copper at the reheating temperature, and Δ(T R This coefficient represents the effect of reheating temperature on the solubility of copper.

[0026] Equal to means equal to + / - 10%, or even + / - 5%, or even + / - 2%.

[0027] In another embodiment of the method according to the present invention, an optimized amount of tin %Sn satisfies the following formula. Opt , carbon%C Opt Antimony %Sb Opt , sulfur %S Opt Aluminum %Al Opt Vanadium %V Opt and boron %B Opt This is calculated. (Formula 2)α(T R ).%Sn Opt +γ(T R ).%C Opt +ε(T R ).%Sb Opt +η(T R ).%S Opt +κ(T R ).%Al Opt +λ(T R ).%V Opt +σ(T R ).%B Opt +Δ(T R )>%Cu est In the formula, α(T R ), γ(T R ), ε(T R ), η(T R ), κ(T R ), λ(T R ) and σ(T R ) is a coefficient representing the respective influence of tin, carbon, antimony, sulfur, aluminum, vanadium, and boron on the solubility of copper at different reheating temperatures. Δ(T R This coefficient represents the effect of reheating temperature on the solubility of copper.

[0028] In another embodiment of the method according to the present invention, an optimized amount of tin %Sn Opt Nickel%Ni Opt , molybdenum%Mo Opt Manganese %Mn Opt , carbon%C Opt Antimony %Sb Opt , silicon %Si Opt , sulfur %S Opt chromium%Cr Opt Aluminum %AOpt l, vanadium %V Opt , arsenic %As Opt , phosphorus%P Opt Niobium %Nb Opt Titanium %Ti Opt , and boron %B Opt However, it is calculated to satisfy the following equation, (Formula 3)α(T R ).%Sn Opt +β(T R ).%Ni Opt +χ(T R ).%Mo Opt +δ(T R ).%Mn Opt +γ(T R ).%C Opt +ε(T R ).%Sb Opt +φ(T R ).%Si Opt +η(T R ).%S Opt +φ(T R ).%Cr Opt +κ(T R ).%Al Opt +λ(T R ).%V Opt +μ(T R ).%As Opt +ν(T R ).%P Opt +θ(T R ).%Nb Opt +ρ(T R ).%Ti Opt +σ(T R ).%B Opt +Δ(T R )>%Cu est In the formula, α(T R ), β(T R ), χ(T R ), δ(T R ), γ(T R ), ε(T R ), φ(T R ), η(T R ), φ(T R ), κ(T R ), λ(T R ), μ(T R ), ν(T R), θ(T R ), ρ(T R ), σ(T R ) is a coefficient representing the respective influence of tin, nickel, molybdenum, manganese, carbon, antimony, silicon, sulfur, chromium, aluminum, vanadium, arsenic, phosphorus, niobium, titanium, and boron on the solubility of copper at the reheating temperature. Δ(T R This coefficient represents the effect of reheating temperature on the solubility of copper.

[0029] Examples of coefficients for each equation are shown in Table 1 below. In all texts, the symbol "E" represents "×10 n It must be understood as such, for example, 9.96E-6 is 9.96 × 10⁻⁶. -6 Alternatively, it must be understood as 0.00000996.

[0030] [Table 1] Table 1

[0031] These coefficients are given as examples and were determined using Thermocalc(R) software, with the Ssol4 database used for antimony and arsenic, and TCFe12 for other elements, based on the compositional range defined below. Naturally, other software and / or other compositions can be used, which will result in slight modifications to the coefficients.

[0032] Once these optimized quantities are calculated, the composition of the molten steel is adjusted accordingly, and the molten steel with the adjusted composition is cast to produce semi-finished products.

[0033] This composition can be adjusted by removing or adding tin, antimony, and / or sulfur, or by maintaining the amount of one or more of each of these elements if a calculated optimized amount is already present. Addition can be carried out by filling the molten metal with material, preferably in the form of wire. Removal can be carried out by appropriate techniques known to those skilled in the art. For example, iron can be added to the tank in the form of molten pig iron, pig iron, or direct reduced iron to dilute the other components of the molten steel. Sulfur can be removed by adding limestone or other Ca-containing materials. Tin and / or antimony can also be captured by changing the composition of the slag. Other processes may also be used, such as the injection of NH3 for tin removal.

[0034] The molten steel produced preferably has a composition of %Sb≦0.01%, %As≦0.1%, %Sn≦0.05%, %Si≦0.9%, %Ni≦4.5%, %P≦0.46%, %S≦0.005%, %Mo≦2.2%, %Cr≦4.5%, %Mn≦2.5%, %Al≦0.6%, %C≦0.21%, %Nb≦0.21%, %Ti≦0.21%, %V≦0.21%, %B≦0.002%, and %Cu≧0.1%, with the remainder being iron and unavoidable impurities, all amounts expressed in weight percent. The amount of copper is preferably 0.1-0.3% by weight.

[0035] In the method of the present invention, the composition of the molten steel is adjusted so that the copper content on the steel surface is less than the limit of copper dissolution, thereby preventing or at least suppressing the penetration of copper into the steel along the austenite grain boundaries and, consequently, the occurrence of hot brittleness.

[0036] The tests were conducted using three steel samples S1-S2 having the compositions defined in Table 2, with the remainder being iron and unavoidable impurities. The solid samples were heated to a temperature equivalent to 1235°C. R The sample was subjected to a heating step, simulating the reheating step of industrial equipment, and microscopic observation was performed to identify the presence of infiltration in the steel bulk. The results are also included in Table 2.

[0037] N means that no infiltration was observed, while Y means that infiltration of the copper-rich phase was observed in the steel bulk.

[0038] Next, according to the present invention, optimized amounts of tin, sulfur, and antimony were calculated using Equation 1 and the coefficients shown in Table 1. Then, the composition of the molten steel was adjusted, and new samples named S1-bis and S2-bis, respectively, were cast and subjected to the same heating steps and observations as previously described.

[0039] [Table 2] Table 2

[0040] It can be observed that infiltration is observed in samples S1 and S2 that do not conform to the present invention, but no infiltration is observed in samples S1 and S2 that have been calculated and implemented with optimized compositions and thus produced by the method according to the present invention.

Claims

1. A method for hot rolling a steel semi-finished product, A. A step of producing molten steel (1), wherein the production step includes melting steel scrap containing copper, B. Copper % Cu in the molten steel (1) produced above ｅｓｔ Steps to estimate the quantity C. A step of casting molten steel (1) to produce a semi-finished product (5), D. Reheat semi-finished product (5) at temperature T Ｒ The step of reheating, E. The process includes the step of hot-rolling the reheated semi-finished product, Between Step B and Step C, perform the following steps: ii) Optimized amount of tin %Sn Ｏｐｔ Antimony %Sb Ｏｐｔ and sulfur %S Ｏｐｔ A step of calculating the optimized quantity, wherein the optimized quantity satisfies the following equation: a (T) Ｒ ).%S. Ｏｐｔ +e(T Ｒ ).%Sb Ｏｐｔ +h(T Ｒ ).%S Ｏｐｔ +Δ(T Ｒ )≧%Cu ｅｓｔ In the formula, α(T Ｒ ), ε(T Ｒ ), η(T Ｒ ) is the reheating temperature T Ｒ These are coefficients representing the respective effects of tin, antimony, and sulfur on the solubility of copper. Δ(T) Ｒ ) is the reheating temperature T with respect to the solubility of copper. Ｒ The step is a coefficient that represents the influence of the effect. iii) The final amounts of tin, antimony, and sulfur in the molten steel are adjusted to match the calculated optimized amounts.

2. The method according to claim 1, wherein the molten steel (1) produced contains at least 0.1% by weight of copper.

3. Step B is the tin % Sn in the molten steel (1) produced. ｅｓｔ Antimony %Sb ｅｓｔ and sulfur %S ｅｓｔ The method according to either claim 1 or 2, including the estimation of the amount of.

4. The method according to any one of claims 1 to 3, wherein in manufacturing step A, the scrap is melted together with molten iron and / or directly with reduced iron.

5. The method according to any one of claims 1 to 4, wherein the molten steel produced has a composition of %Sb≦0.01%, %As≦0.1%, %Sn≦0.05%, %Si≦0.9%, %Ni≦4.5%, %P≦0.46%, %S≦0.008%, %Mo≦2.2%, %Cr≦4.5%, %Mn≦2.5%, %Al≦0.6%, %C≦0.21%, %Nb≦0.21%, %Ti≦0.21%, %V≦0.21%, %B≦0.002%, and %Cu≧0.1%, with the remainder being iron and unavoidable impurities, all amounts expressed in weight percent.

6. The method according to any one of claims 1 to 5, wherein the amount of copper in the molten steel is 0.1 to 0.3% by weight.

7. Reheating temperature T Ｒ The method according to any one of claims 1 to 6, wherein the temperature is 1100°C to 1350°C.

8. The method according to any one of claims 1 to 7, wherein the semi-finished product is a slab.

9. α(T) Ｒ )=-3.75E-04. T Ｒ -0.11211, ε(T Ｒ )=4.48E-04. T Ｒ -1.53167, η(T Ｒ )=-1.65E-03. T Ｒ +1.02667 and Δ(T Ｒ )=2.00E-04. T Ｒ The method according to any one of claims 1 to 8, wherein the value is -0.04817.

10. Calculation step Ei) is carbon % C Ｏｐｔ Aluminum % Al Ｏｐｔ Boron % B Ｏｐｔ and vanadium %V Ｏｐｔ This includes the calculation of an optimized quantity, wherein the optimized quantity satisfies the following equation: a (T) Ｒ ).%S. Ｏｐｔ +γ(T Ｒ ).%C Ｏｐｔ +e(T Ｒ ).%Sb Ｏｐｔ +h(T Ｒ ).%S Ｏｐｔ +k (T) Ｒ ).%All Ｏｐｔ +λ(T Ｒ ).%V Ｏｐｔ +σ(T) Ｒ ).%B Ｏｐｔ +Δ(T Ｒ )≧%Cu ｅｓｔ In the formula, α(T Ｒ ), γ(T Ｒ ), ε(T Ｒ ), η(T Ｒ ), κ(T Ｒ ), λ(T Ｒ ), σ(T Ｒ These are coefficients that represent the respective effects of tin, carbon, antimony, sulfur, aluminum, vanadium, and boron on the solubility of copper at different reheating temperatures. Δ(T) Ｒ The method according to any one of claims 1 to 9, wherein ) is a coefficient representing the effect of reheating temperature on the solubility of copper.

11. Step B estimation is carbon%C ｅｓｔ Boron % B ｅｓｔ Aluminum % Al ｅｓｔ and vanadium %V ｅｓｔ The method according to claim 10, including the estimation of the amount of.

12. α(T) Ｒ )=-3.75E-04. T Ｒ -0.11211, γ(T Ｒ )=-3.55E-04. T Ｒ +0.2229, ε(T Ｒ )=4.48E-04. T Ｒ -1.53167, η(T Ｒ )=-1.65E-03. T Ｒ +1.02667, κ(T Ｒ )=-1.24E-04. T Ｒ +0.12294, λ(T Ｒ )=-4.52E-05. T Ｒ +0.02392, σ(T Ｒ )=-1.33E-03. T Ｒ +1.5078 and Δ(T Ｒ )=3.95E-04. T Ｒ The method according to claim 10 or 11, wherein the value is -0.27398.

13. said calculation step Ei) comprises tin %Sn Ｏｐｔ , nickel %Ni Ｏｐｔ , molybdenum %Mo Ｏｐｔ , manganese %Mn Ｏｐｔ , carbon %C Ｏｐｔ , antimony %Sb Ｏｐｔ , silicon %Si Ｏｐｔ , sulfur %S Ｏｐｔ , chromium %Cr Ｏｐｔ , aluminum %A Ｏｐｔ l, vanadium %V Ｏｐｔ , arsenic %As Ｏｐｔ , phosphorus %P Ｏｐｔ , niobium %Nb Ｏｐｔ , titanium %Ti Ｏｐｔ , boron %B Ｏｐｔ calculation of optimized amounts of, wherein said optimized amounts satisfy the following formula, a (T) Ｒ ).%S. Ｏｐｔ +β(T Ｒ ).%% / Ｏｐｔ +x(T Ｒ ).%Mo Ｏｐｔ +δ(T Ｒ ).%M. Ｏｐｔ +γ(T Ｒ ).%C Ｏｐｔ +e(T Ｒ ).%Sb Ｏｐｔ +φ(T Ｒ ).%Si Ｏｐｔ +h(T Ｒ ).%S Ｏｐｔ +φ(T Ｒ ).%Cr Ｏｐｔ +k (T) Ｒ ).%All Ｏｐｔ +λ(T Ｒ ).%V Ｏｐｔ +μ(T Ｒ ).%%s Ｏｐｔ +n(T Ｒ ).%P Ｏｐｔ +θ(T Ｒ ).%Nb Ｏｐｔ +r(T Ｒ ).%% Ｏｐｔ +σ(T) Ｒ ).%B Ｏｐｔ +Δ(T Ｒ )≧%Cu ｅｓｔ In the formula, α(T Ｒ ), β(T Ｒ ), χ(T Ｒ ), δ(T Ｒ ), γ(T Ｒ ), ε(T Ｒ ), φ(T Ｒ ), η(T Ｒ ), φ(T Ｒ ), κ(T Ｒ ), λ(T Ｒ ), μ(T Ｒ ), ν(T Ｒ ), θ(T Ｒ ), ρ(T Ｒ ), σ(T Ｒ ) is a coefficient representing the respective influence of tin, nickel, molybdenum, manganese, carbon, antimony, silicon, sulfur, chromium, aluminum, vanadium, arsenic, phosphorus, niobium, titanium, and boron on the solubility of copper at the reheating temperature. Δ(T) Ｒ The method according to any one of claims 10 to 12, wherein ) is a coefficient representing the effect of reheating temperature on the solubility of copper.

14. The estimation in step B is nickel % Ni ｅｓｔ Molybdenum % Mo ｅｓｔ Manganese % Mn ｅｓｔ Silicon % Si ｅｓｔ chromium%Cr ｅｓｔ , arsenic %As ｅｓｔ Phosphorus %P ｅｓｔ Niobium %Nb ｅｓｔ , and titanium %Ti ｅｓｔ The method according to claim 13, further comprising estimating the amount of.

15. α(T) Ｒ )=-3.75E-04. T Ｒ -0.11211, β(T Ｒ )=-2.40E-07. T Ｒ +0.02462, χ(T Ｒ )=-2.87E-05. T Ｒ +0.01797, δ(T Ｒ )=-1.29E-04. T Ｒ +0.14394, γ(T Ｒ )=-3.55E-04. T Ｒ +0.2229, ε(T Ｒ )=4.48E-04. T Ｒ -1.53167,φ(T Ｒ )=-5.69E-05. T Ｒ +0.00884, η(T Ｒ )=-1.65E-03. T Ｒ +1.02667,φ(T Ｒ )=5.66E-06. T Ｒ -0.01346, κ(T Ｒ )=-1.24E-04. T Ｒ +0.12294 λ(T Ｒ )=-4.52E-05. T Ｒ +0.02392,μ(T Ｒ )=-3.61E-05. T Ｒ＋ 0.04027, ν(T Ｒ )=-7.58E-06. T Ｒ +0.00343, θ(T Ｒ )=-7.03E-06. T Ｒ +0.00207, ρ(T Ｒ )=1.29E-06. T Ｒ +0.01007, σ(T Ｒ )=-1.33E-03. T Ｒ +1.5078 and Δ(T Ｒ )=8.09E-04. T Ｒ The method according to claim 13 or 14, wherein the coefficient is -0.80722.

16. The method according to any one of claims 1 to 15, wherein in step B, the composition of the molten steel (1) produced is estimated using a model.

17. The method according to claim 16, wherein the model uses as input data the composition of raw materials comprising copper-containing steel scrap that was melted to produce molten steel (1).

18. The method according to any one of claims 1 to 15, wherein the composition of the molten steel is estimated by analyzing a lollipop-type sample of the molten steel (1).

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