Method for producing ultralow-sulfur peritectic steel continuous casting round billet through full-scrap steel electric arc furnace

Abstract

The invention relates to the technical field of ultralow-sulfur peritectic steel smelting, and particularly discloses a method for producing an ultralow-sulfur peritectic steel continuous casting round billet through a full-scrap-steel electric arc furnace. According to the method for producing the ultra-low-sulfur peritectic steel continuous casting round billet through the full-scrap steel electric arc furnace, the corresponding conditions of burdening, electric arc furnace smelting, molten steel slagging and deoxidizing, LF refining, VD vacuum smelting and peritectic steel round billet continuous casting are controlled, a specific amount of low-sulfur scrap steel is selected, and the oxygen supply strength in the electric arc furnace smelting process is limited; the carbon content during tapping of an electric arc furnace is guaranteed in a carbon spraying mode, the adding opportunity of aluminum ingots, premelting refining slag, fluorite, lime and aluminum wires is limited in the molten steel slagging and deoxidizing process, the aluminum content of molten steel during LF refining is controlled, the top slag content of VD vacuum smelting is limited, a high-alkalinity low-sulfur carbon-free covering agent is added in the initial continuous casting stage of peritectic steel round billets, and the high-alkalinity low-sulfur carbon-free covering agent is added. The ultra-low-sulfur peritectic steel continuous casting round billet with excellent comprehensive performance is prepared, the surface is free of sunken and crack defects, and the defect rate is basically zero.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-low sulfur peritectic steel smelting, and in particular to a method for producing ultra-low sulfur peritectic steel continuous casting round billets in a full scrap steel electric arc furnace. Background Art

[0002] Ultra-low sulfur steel refers to steel with a sulfur content of <0.005%. It has good surface quality and high sizing rate. Its transverse ductility, Z-direction performance, notch toughness, low-temperature impact toughness, resistance to hydrogen-induced cracking and sulfide stress corrosion are better than those of conventional sulfur-containing steels. It can be used as oil and gas pipeline steel under acidic corrosive gases, drilling steel pipes and offshore platform structural steel, low-temperature steel, pressure vessel steel, ships, and rail steel.

[0003] Peritectic steel refers to carbon steel with a carbon content of 0.08% to 0.17%. When peritectic steel is cooled from liquid phase to 1495°C, a peritectic reaction will occur, δFe (solid) + L (liquid) → γFe (solid). Due to the large linear shrinkage during the peritectic reaction (about 9.8×10 -5 / ℃, while the linear shrinkage coefficient of δFe without peritectic reaction is about 2×10 -5 / ℃), air gaps are easily formed between the billet shell and the wall of the crystallizer. The premature formation of air gaps will lead to uneven shrinkage and uneven thickness of the billet shell, and cracks will form at weak points, which will easily cause steel leakage accidents and surface quality defects of the billet. Moreover, compared with billets of other shapes, the surface of the peritectic steel continuous casting round billet is more prone to surface depression, making it one of the more difficult steel types to be continuously cast in continuous casting production.

[0004] At present, the production process of ultra-low sulfur peritectic steel generally uses slag as raw material, and the converter uses blast furnace molten iron. The sulfur content in the molten iron is relatively low, the carbon content is relatively high, and the carbon-sulfur range is easy to adjust. However, for all scrap steel raw materials, only electric arc furnaces can be used for production. At present, when all-scrap steel electric arc furnaces are used to produce ultra-low sulfur peritectic steel continuous casting round billets, the ultra-low sulfur and peritectic steel characteristics of the steel produced lead to the following problems in the production process: (1) The uncontrollability of the steel entering the furnace leads to unstable original sulfur content of the steel discharged from the electric arc furnace, making desulfurization in the refining furnace difficult; (2) A large amount of oxygen is required for decarburization during electric arc furnace smelting, and the carbon content at the end of the steel is low, resulting in high oxygen content when the steel is discharged from the electric arc furnace, making deoxidation and desulfurization difficult during refining; (3) Ultra-low sulfur has extremely high requirements on the slag system of refining slag, making refining and desulfurization difficult, and subsequent vacuum smelting (VD) is prone to resulfurization problems; (4) VD ladle steel has resulfurization problems during continuous casting; (5) There are serious surface depression defects and cracks in the casting process of peritectic steel for continuous casting round billets, with a defect rate of more than 0.8%. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for producing ultra-low sulfur peritectic steel continuous casting round billets in an all-scrap steel electric arc furnace. By controlling the corresponding conditions of batching, electric arc furnace smelting, molten steel slag deoxidation, LF refining, VD vacuum smelting and continuous casting of peritectic steel round billets, ultra-low sulfur peritectic steel continuous casting round billets with excellent comprehensive performance are produced, and the surface has no depressions and cracks.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is: A method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace comprises the following steps: S1, ingredients: All scrap steel includes the following raw materials in percentage by mass: 40% to 55% of ordinary scrap steel and 45% to 60% of low-sulfur scrap steel; The sulfur content of the ordinary scrap steel is 0.01% to 0.03%, and the sulfur content of the low-sulfur scrap steel is ≤ 0.01%; S2, electric arc furnace smelting: The raw materials were smelted in an electric arc furnace with an oxygen supply intensity of 50 Nm 3 / (h·t)~110Nm 3 / (h·t); When the molten pool temperature is 1580℃~1610℃, carbon is sprayed; the carbon content of the molten steel is controlled to be 0.05%~0.07% during tapping; S3, slag making and deoxidation of molten steel: When the steel is tapped to 5% to 15% of the total mass of the molten steel, add aluminum ingots to the ladle; When the steel is tapped to 35% to 45% of the total mass of the molten steel, pre-melted refined slag and fluorite are added to the ladle, and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel reaches 45% to 55%, lime is added to the ladle; When the steel is tapped to 100% of the total mass of the molten steel, add aluminum wire to the ladle to control the aluminum content in the molten steel to ≥ 0.05% and the dissolved oxygen content to ≤ 0.0003%; S4, LF Refining: The molten steel in the ladle is transferred to a refining furnace, power is supplied and argon gas is introduced, lime, aluminum particles and silicon carbide are added to make white slag, and white slag refining is performed, and the aluminum content of the molten steel is controlled to be ≥0.03% during the refining process; When the sulfur content of the molten steel is ≤0.0008%, the aluminum content of the molten steel is adjusted to 0.04%~0.05%, the superheat is 120℃~140℃, and the steel is tapped; S5, VD vacuum smelting: 40wt% to 50wt% of the top slag of the molten steel after LF refining is poured off, and the molten steel is transferred to a vacuum smelting furnace, and argon gas is introduced for vacuum smelting; after breaking the air, calcium silicon wire is fed and soft-blown; S6, continuous casting of peritectic steel round billets: The soft-blown molten steel is transferred to a tundish, a high-basicity, low-sulfur, carbon-free covering agent is added, and continuous steel casting is performed. The steel is cooled to obtain an ultra-low-sulfur peritectic steel continuous casting round billet.

[0007] It should be noted that "breaking air" in the present invention refers to returning from a vacuum state to normal pressure.

[0008] Compared with the prior art, the method for producing ultra-low sulfur peritectic steel continuous casting round billets in an all-scrap steel electric arc furnace provided by the present invention selects a specific amount of low-sulfur scrap steel, which provides a low-sulfur prerequisite for the subsequent smelting process, can stabilize the sulfur content in the molten steel after smelting in the electric arc furnace, and is conducive to the smooth progress of subsequent refining and desulfurization; by limiting the oxygen supply intensity in the electric arc furnace smelting process, the reaction rate of carbon and oxygen is controlled, and then the carbon content in the molten steel is controlled; when the molten pool temperature of the electric arc furnace is 1580°C~1610°C, carbon and oxygen react violently, and the carbon in the molten steel decreases rapidly, and a carbon spraying method is used to ensure the carbon content when tapping; the present invention balances the carbon-oxygen relationship by controlling the carbon content when tapping the electric arc furnace, reducing The oxygen content of the molten steel at this time creates good conditions for subsequent refining and desulfurization, while ensuring the carbon content required for peritectic steel and avoiding segregation of carbon components; during the slag-making and deoxidation process of the molten steel, adding aluminum ingots at a specific time can ensure excellent yield and good deoxidation effect. The present invention has found through a large number of experiments that if the aluminum ingot is added too early, the molten steel in the ladle is less, resulting in a greatly reduced yield of the aluminum ingot; if the aluminum ingot is added too late, the lightweight aluminum ingot will float on the surface of the molten steel and will not achieve the best deoxidation effect; during the slag-making and deoxidation process of the molten steel, adding pre-melted refined slag at a specific time can effectively utilize the stirring kinetic energy in the steel-making process to mix the slag, thereby improving the chemical slag effect, and significantly improved the desulfurization effect; in the later stage of slag making and deoxidation of molten steel, the balance between acid-soluble aluminum and dissolved oxygen is adjusted by controlling the aluminum content in the molten steel, so as to better reduce the content of dissolved oxygen in the molten steel at this time, and provide the prerequisite for the rapid progress of subsequent refining and desulfurization; the aluminum ingots, pre-melted refined slag, fluorite, lime and aluminum wire added in the process of slag making and deoxidation of molten steel provide the prerequisite for the acquisition of the subsequent refining slag system; in the early stage of LF refining, white slag can be quickly made by adding lime, aluminum particles and silicon carbide, and the chemical composition of the refining slag system can be adjusted to improve the refining effect; the aluminum content of the molten steel is controlled within a specific range throughout the refining process, and the content of dissolved oxygen in the molten steel can be limited to an appropriate range ; The aluminum content of the molten steel will be reduced to a certain extent after VD vacuum smelting. Adjusting the aluminum content of the molten steel within a specific range in the later stage of LF refining can effectively prevent the segregation of aluminum content in the ultra-low sulfur peritectic steel continuous casting round billet; At the beginning of VD vacuum smelting, by controlling the content of the top slag and pouring out part of the refined slag system, the sulfur in the refined slag system during the vacuum smelting process can be prevented from returning to the molten steel again, reducing the possibility of resulfurization, and preventing the overflow of the refined slag system from causing accidents. In addition, the remaining amount of top slag can improve the effect of vacuum smelting and further improve the purity of the molten steel; At the beginning of continuous casting of peritectic steel round billets, by adding high-alkalinity, low-sulfur, carbon-free covering agents, the resulfurization problem in the continuous steel casting process can be effectively reduced.

[0009] The method for producing ultra-low sulfur peritectic steel continuous casting round billets in an all-scrap steel electric arc furnace provided by the present invention controls the corresponding conditions of batching, electric arc furnace smelting, molten steel slag deoxidation, LF refining, VD vacuum smelting and peritectic steel round billet continuous casting, so as to produce ultra-low sulfur peritectic steel continuous casting round billets with excellent comprehensive performance, without depressions and cracks on the surface, and with a defect rate of substantially zero.

[0010] Preferably, in S1, the low-sulfur scrap steel includes low-sulfur briquettes, and the mass of the low-sulfur briquettes accounts for 35% to 40% of the total scrap steel.

[0011] The invention uses low-sulfur briquettes with relatively large density to better control the sulfur content in the molten steel, reduce the pressure of the electric furnace, and create better conditions for steelmaking and smelting.

[0012] Preferably, in S2, when the molten pool temperature is ≤1560°C, the oxygen supply intensity is 50Nm 3 / (h·t)~70Nm 3 / (h·t); when the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 80Nm 3 / (h·t)~110Nm 3 / (h·t); when the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 50Nm 3 / (h·t)~70Nm 3 / (h·t).

[0013] During the arc furnace smelting process, the temperature of the molten pool is constantly rising. The oxygen supply temperature is adjusted accordingly according to the molten pool temperature, which can better control the reaction rate of carbon and oxygen. When the molten pool temperature is ≤1560℃, the reaction temperature is low, the oxygen supply intensity is weak, and the reaction rate is slow; when the molten pool temperature is 1560℃~1610℃, the reaction temperature is high, the oxygen supply intensity is increased, and carbon injection is carried out at the same time, and the reaction rate is intense; when the molten pool temperature is 1610℃~1650℃, in order to ensure the carbon content when tapping, the oxygen supply intensity is weakened.

[0014] Preferably, in S2, the carbon injection rate is 0.6 kg / (min·t) to 0.9 kg / (min·t).

[0015] Preferably, in S3, the amount of the aluminum ingot added is 3kg / t to 3.5kg / t.

[0016] For example, in S3, the purity of the aluminum ingot is ≥99.9%.

[0017] Preferably, in S3, the pre-melted refined slag comprises the following chemical components in percentage by mass: CaO 32% to 40%, SiO2≤10%, Al2O346% to 54% and MgO≤1%.

[0018] Preferably, in S3, the amount of the pre-melted refined slag added is 4kg / t to 5kg / t.

[0019] For example, in S3, the fluorite includes the following chemical components in mass percentage: CaF2≥80%, SiO2≤18% and S≤0.03%.

[0020] Preferably, in S3, the amount of fluorite added is 1.5kg / t~2kg / t.

[0021] For example, in S3 and S4, the lime includes the following chemical components in mass percentage: CaO ≥ 90%, SiO2 ≤ 3%, MgO ≤ 1% and S ≤ 0.03%.

[0022] Preferably, in S3, the amount of lime added is 5.5kg / t~6.5kg / t.

[0023] Preferably, in S3, the amount of the aluminum wire added is 0.3 kg / t to 0.5 kg / t.

[0024] For example, in S3, the purity of the aluminum wire is ≥99.9%.

[0025] Preferably, in S4, the flow rate of the argon gas is 230NL / min~270NL / min.

[0026] Preferably, in S4, the amount of lime added is 5kg / t to 5.5kg / t.

[0027] Preferably, in S4, the amount of aluminum particles added is 0.2kg / t to 0.3kg / t.

[0028] For example, in S4, the purity of the aluminum particles is ≥99.9%.

[0029] Preferably, in S4, the amount of silicon carbide added is 0.3 kg / t to 0.5 kg / t.

[0030] For example, in S4, silicon carbide includes the following chemical components in percentage by mass: SiC ≥ 75%, SiO2 ≤ 10% and C ≤ 10%.

[0031] Preferably, in S4, during the white slag refining process, the refined slag system includes the following chemical components in percentage by mass: CaO 59%~62.5%, SiO27%~10%, Al2O327%~29%, MgO 3%~5%, FeO+MnO≤0.5%.

[0032] The present invention uses a specific refined slag system to achieve the effect of deep desulfurization, so that the sulfur content of the molten steel reaches below 0.0008%, and the VD vacuum smelting does not cause the problem of back sulfur.

[0033] Preferably, in S4, the time for making white slag is 10 min to 15 min.

[0034] Preferably, in S4, the white slag refining time is ≥20 min, more preferably 30 min to 40 min.

[0035] Preferably, in S4, the LF refining time is 50 min to 55 min.

[0036] In the present invention, the longer the white slag is kept, the better the desulfurization effect is.

[0037] For example, in S4, when the power transmission temperature is ≥1560°C, a spectrum sample is taken for analysis, and each chemical composition is adjusted to a target composition.

[0038] Preferably, in S5, the vacuum smelting time is ≥15 min, more preferably 15 min to 20 min.

[0039] Preferably, in S5, when the vacuum degree is greater than 67 kPa, the flow rate of the argon gas is 6 NL / min to 16 NL / min; when the vacuum degree is less than or equal to 67 kPa, the flow rate of the argon gas is 40 NL / min to 80 NL / min.

[0040] The present invention can better achieve the degassing effect and effectively remove inclusions by limiting the relationship between the vacuum degree and the argon flow rate, thereby maximizing the purity of the molten steel. If the argon flow rate is too large, the bubbles will float up quickly during vacuum degassing, and the vacuum dehydrogenation and adsorption of inclusions cannot be achieved; if the argon flow rate is too small, the mixed impact reaction of the steel slag cannot be fully carried out, and the purpose of dehydrogenation and removal of inclusions cannot be achieved.

[0041] Preferably, in S5, the amount of calcium silicon wire added is 0.35kg / t to 0.5kg / t.

[0042] For example, in S5, the calcium silicon wire includes the following chemical components in mass percentage: Ca≥30% and Si≥55.

[0043] Preferably, in S5, the flow rate of the soft blowing is 3NL / min~6NL / min, and the soft blowing time is ≥20min.

[0044] In the later stage of VD vacuum smelting, soft blowing is used to promote the floating of inclusions in the molten steel, improve the cleanliness of the molten steel, and reduce the superheat of the molten steel. Under the premise of ensuring that the temperature of the molten steel is controllable, the longer the soft blowing time, the better.

[0045] Preferably, in S6, the superheat of the molten steel in the tundish is 18°C ​​to 28°C.

[0046] Preferably, in S6, the high basicity, low sulfur and carbon-free covering agent comprises the following chemical components in percentage by mass: CaO 33%~43%, SiO27%~17%, Al2O318%~28%, MgO 3.5%~7.5% and S≤0.2%.

[0047] Further preferably, in S6, the high basicity, low sulfur and carbon-free covering agent comprises the following chemical components in percentage by mass: CaO 38±2%, SiO212±2%, Al2O323±2%, MgO 5.5±1% and S≤0.2%.

[0048] Preferably, in S6, the added amount of the high basicity, low sulfur and carbon-free covering agent is 1.3 kg / t to 1.5 kg / t.

[0049] Preferably, in S6, the continuous casting speed of the continuous cast steel is 1.5m / min~1.75m / min.

[0050] Preferably, in S6, the continuous steel casting adopts a continuous casting crystallizer.

[0051] Further preferably, in S6, the protective slag of the continuous casting crystallizer includes the following chemical components in percentage by mass: CaO 33.8%~39.8%, SiO2 27.6%~33.6%, Al2O 35%~9%, and Na2O+K2O 2%~4%.

[0052] More preferably, in S6, the melting point of the protective slag is 1170° C. to 1270° C., and the viscosity of the protective slag is 0.43 Pa·s to 0.57 Pa·s.

[0053] Further preferably, in S6, the water flow rate of the continuous casting crystallizer is 105 Nm 3 / h~115Nm 3 / h.

[0054] Further preferably, in S6, the electromagnetic stirring current of the continuous casting crystallizer is 350A~370A, and the end electromagnetic stirring current is 380A~400A.

[0055] For example, in S6, the frequency of electromagnetic stirring is 4 Hz, and the stirring mode is continuous stirring; the frequency of terminal electromagnetic stirring is 10 H, and the stirring mode is 10s-2s-10s.

[0056] Preferably, in S6, during the continuous steel casting process, the specific water volume is 0.32L / kg~0.36L / kg, and the mass proportion of cooling water in the secondary cooling zone is 23.5%~34.5%, 33%~33.8%, 22.5%~23.5%, 11.5%~12.5% ​​and 7.4%~7.9%, respectively.

[0057] Further preferably, in S6, during the continuous steel casting process, the specific water amount is 0.34 L / kg, and the mass proportions of cooling water in the secondary cooling zone are 23.99%, 33.38%, 23.04%, 11.96% and 7.64% respectively.

[0058] Preferably, in S6, the diameter of the ultra-low sulfur peritectic steel continuous casting round billet is 180 mm to 220 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a low-magnification microstructure photograph of the 12MnV steel in Example 1 of the present invention. The diameter of the 12MnV steel in the figure is 200 mm. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0061] Unless otherwise specified, the contents in the present invention are all weight contents.

[0062] Example 1 This embodiment provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV steel in a full scrap steel electric arc furnace, comprising the following steps: S1, ingredients: The total scrap steel is composed of the following raw materials in percentage by mass: 48% ordinary scrap steel and 52% low-sulfur scrap steel; low-sulfur scrap steel includes low-sulfur briquettes, the mass of which accounts for 38% of the total scrap steel.

[0063] Among them, the sulfur content of ordinary scrap steel is 0.025%, and the sulfur content of low-sulfur scrap steel is 0.008%.

[0064] S2, electric arc furnace smelting: The raw materials are smelted in an electric arc furnace. When the molten pool temperature is ≤1560℃, the oxygen supply intensity is 60Nm 3 / (h·t); When the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 95Nm 3 / (h·t), while carbon is sprayed at a rate of 0.8kg / (min·t); When the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 60Nm 3 / (h·t), steel is tapped when the carbon content of the molten steel is 0.06%.

[0065] S3, slag making and deoxidation of molten steel: When the steel is tapped to 10% of the total mass of the molten steel, add 3.2kg / t aluminum ingots into the ladle; When the steel is tapped to 40% of the total mass of the molten steel, 4.5kg / t of pre-melted refined slag and 1.8kg / t of fluorite are added to the ladle. The pre-melted refined slag includes the following chemical components in percentage by mass: CaO 36%, SiO27%, Al2O350% and MgO0.7%; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel is 50%, add 6.0kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, 0.4kg / t of aluminum wire is added to the ladle to control the aluminum content in the molten steel to 0.055% and the dissolved oxygen content to 0.00026%.

[0066] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced at a flow rate of 250NL / min. 5.2kg / t lime, 0.25kg / t aluminum particles and 0.4kg / t silicon carbide are added to make white slag (12min). The chemical composition of the refining slag system is controlled (including CaO 59%, SiO27%, Al2O329%, MgO 4%, FeO+MnO=0.4%), and white slag refining is carried out for 35min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0067] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0008%, adjust the aluminum content of the molten steel to 0.04%, and the superheat is 130℃ before tapping.

[0068] S5, VD vacuum smelting: After LF refining, pour off 45wt% of the top slag of the molten steel and transfer it to a vacuum smelting furnace. Vacuum smelting is carried out for 18 minutes by introducing argon. When the vacuum degree is greater than 67kPa, the flow rate of the argon is 11NL / min; when the vacuum degree is less than or equal to 67kPa, the flow rate of the argon is 60NL / min. After breaking the air, feed 0.41kg / t silicon calcium wire and soft blow for 21 minutes (flow rate is 5NL / min).

[0069] S6, continuous casting of peritectic steel round billets: The soft-blown molten steel was transferred to the tundish (the superheat of the molten steel was 23°C), and 1.4 kg / t of high-basicity, low-sulfur, carbon-free covering agent was added (the high-basicity, low-sulfur, carbon-free covering agent includes the following chemical components by mass percentage: CaO 38%, SiO2 12%, Al2O3 23%, MgO 5.5% and S 0.15%). The continuous casting crystallizer was used for continuous casting, with a continuous casting speed of 1.65 m / min and a water flow rate of 110 Nm3 / h, the electromagnetic stirring current is 360A, and the end electromagnetic stirring current is 390A. The protective slag of the continuous casting crystallizer includes the following chemical components by mass percentage: CaO 36.8%, SiO230.6%, Al2O37.0%, Na2O+K2O3.0%; the melting point is 1250℃, and the viscosity is 0.5Pa·s. Cooling, the specific water volume is 0.34L / kg, and the mass proportions of cooling water in the secondary cooling zone are 23.98%, 33.38%, 23.04%, 11.96% and 7.64% respectively, and a Φ200mm ultra-low sulfur peritectic steel continuous casting round billet 12MnV steel (see Figure 1 , its chemical composition is shown in Table 1).

[0070] Example 2 This embodiment provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 14Mn in a full scrap steel electric arc furnace, comprising the following steps: S1, ingredients: The whole scrap steel is composed of raw materials with the following mass percentages: 40% ordinary scrap steel and 60% low-sulfur scrap steel; the low-sulfur scrap steel includes low-sulfur briquettes, and the mass of low-sulfur briquettes accounts for 35% of the whole scrap steel.

[0071] Among them, the sulfur content of ordinary scrap steel is 0.025%, and the sulfur content of low-sulfur scrap steel is 0.008%.

[0072] S2, electric arc furnace smelting: The raw materials are smelted in an electric arc furnace. When the molten pool temperature is ≤1560℃, the oxygen supply intensity is 50Nm 3 / (h·t); When the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 110Nm 3 / (h·t), while carbon was sprayed at a rate of 0.9kg / (min·t); When the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 50Nm 3 / (h·t), steel is tapped when the carbon content of the molten steel is 0.07%.

[0073] S3, slag making and deoxidation of molten steel: When the steel is tapped to 5% of the total mass of the molten steel, add 3kg / t of aluminum ingots into the ladle; When the steel is tapped to 35% of the total mass of the molten steel, 4kg / t of pre-melted refined slag and 2kg / t of fluorite are added to the ladle. The pre-melted refined slag includes the following chemical components in percentage by mass: CaO 40%, SiO28%, Al2O346% and MgO0.9%; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel is 45%, add 5.5kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, 0.3kg / t of aluminum wire is added to the ladle to control the aluminum content in the molten steel to 0.06% and the dissolved oxygen content to 0.00025%.

[0074] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced at a flow rate of 270NL / min. 5.5kg / t lime, 0.2kg / t aluminum particles and 0.5kg / t silicon carbide are added to make white slag (12min). The chemical composition of the refining slag system is controlled (including CaO 62.5%, SiO27%, Al2O327%, MgO 3%, FeO+MnO=0.3%), and white slag refining is carried out for 30min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0075] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0008%, adjust the aluminum content of the molten steel to 0.05%, and the superheat is 120℃ before tapping.

[0076] S5, VD vacuum smelting: After LF refining, pour off 40wt% of the top slag of the molten steel and transfer it to a vacuum smelting furnace. Vacuum smelting is carried out for 19 minutes by introducing argon. When the vacuum degree is greater than 67kPa, the flow rate of the argon is 6NL / min; when the vacuum degree is less than or equal to 67kPa, the flow rate of the argon is 40NL / min. After breaking the air, feed 0.35kg / t silicon calcium wire and soft blow for 23 minutes (flow rate is 3NL / min).

[0077] S6, continuous casting of peritectic steel round billets: The soft-blown molten steel was transferred to the tundish (the superheat of the molten steel was 18°C), and 1.3 kg / t of high-basicity, low-sulfur, carbon-free covering agent was added (the high-basicity, low-sulfur, carbon-free covering agent includes the following chemical components in mass percentage: CaO 40%, SiO2 10%, Al2O3 25%, MgO 4.5% and S 0.15%). The continuous casting crystallizer was used for continuous casting, with a continuous casting speed of 1.5 m / min and a water flow rate of 105 Nm 3 / h, the electromagnetic stirring current is 350A, and the end electromagnetic stirring current is 380A. The protective slag of the continuous casting crystallizer includes the following chemical components by mass percentage: CaO 34%, SiO231%, Al2O39%, Na2O+K2O 2%; the melting point is 1200℃, and the viscosity is 0.45Pa·s. Cooling, the specific water volume is 0.36L / kg, and the mass proportion of cooling water in the secondary cooling zone is 23.98%, 33.38%, 23.04%, 11.96% and 7.64% respectively, and the Φ200mm ultra-low sulfur peritectic steel continuous casting round billet 14Mn (its chemical composition is shown in Table 1).

[0078] Example 3 This embodiment provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet L245NCS in an all-scrap electric arc furnace, comprising the following steps: S1, ingredients: The whole scrap steel is composed of raw materials with the following mass percentages: 55% ordinary scrap steel and 45% low-sulfur scrap steel; the low-sulfur scrap steel includes low-sulfur briquettes, and the mass of low-sulfur briquettes accounts for 40% of the whole scrap steel.

[0079] Among them, the sulfur content of ordinary scrap steel is 0.025%, and the sulfur content of low-sulfur scrap steel is 0.008%.

[0080] S2, electric arc furnace smelting: The raw materials are smelted in an electric arc furnace. When the molten pool temperature is ≤1560℃, the oxygen supply intensity is 70Nm 3 / (h·t); When the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 82Nm 3 / (h·t), while carbon is sprayed at a rate of 0.6kg / (min·t); When the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 70Nm 3 / (h·t), steel is tapped when the carbon content of the molten steel is 0.05%.

[0081] S3, slag making and deoxidation of molten steel: When the steel is tapped to 15% of the total mass of the molten steel, add 3.5kg / t aluminum ingots into the ladle; When the steel is tapped to 45% of the total mass of the molten steel, 5kg / t of pre-melted refined slag and 1.5kg / t of fluorite are added to the ladle. The pre-melted refined slag includes the following chemical components in percentage by mass: CaO 32%, SiO28%, Al2O354% and MgO0.7%; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel reaches 55%, add 6.5kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, 0.5kg / t of aluminum wire is added to the ladle to control the aluminum content in the molten steel to 0.058% and the dissolved oxygen content to 0.00027%.

[0082] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced at a flow rate of 230NL / min. 5kg / t lime, 0.3kg / t aluminum particles and 0.3kg / t silicon carbide are added to make white slag (15min). The chemical composition of the refining slag system is controlled (including CaO 59.2%, SiO2 10%, Al2O3 27%, MgO 3%, FeO+MnO=0.3%), and white slag refining is carried out for 40min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0083] When the power supply temperature is 1570℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0007%, adjust the aluminum content of the molten steel to 0.04%, and the superheat is 140℃ before tapping.

[0084] S5, VD vacuum smelting: After LF refining, pour off 50wt% of the top slag of the molten steel and transfer it to a vacuum smelting furnace. Then, introduce argon gas for vacuum smelting for 20 minutes. When the vacuum degree is greater than 67kPa, the flow rate of the argon gas is 16NL / min; when the vacuum degree is less than or equal to 67kPa, the flow rate of the argon gas is 80NL / min. After breaking the air, feed 0.5kg / t silicon calcium wire and soft blow for 24 minutes (flow rate is 6NL / min).

[0085] S6, continuous casting of peritectic steel round billets: The soft-blown molten steel was transferred to the tundish (the superheat of the molten steel was 28°C), and 1.5 kg / t of high-basicity, low-sulfur, carbon-free covering agent was added (the high-basicity, low-sulfur, carbon-free covering agent includes the following chemical components in percentage by weight: CaO 36%, SiO2 14%, Al2O3 21%, MgO 6.5% and S 0.15%). The continuous casting crystallizer was used for continuous casting, with a continuous casting speed of 1.75 m / min and a water flow rate of 115 Nm 3 / h, the electromagnetic stirring current is 370A, and the end electromagnetic stirring current is 400A. The protective slag of the continuous casting crystallizer includes the following chemical components by mass percentage: CaO 39%, SiO228%, Al2O35%, Na2O+K2O 4%; the melting point is 1250℃, and the viscosity is 0.55Pa·s. Cooling, the specific water volume is 0.32L / kg, and the mass proportion of cooling water in the secondary cooling zone is 23.98%, 33.38%, 23.04%, 11.96% and 7.64% respectively, and the Φ200mm ultra-low sulfur peritectic steel continuous casting round billet L245NCS (its chemical composition is shown in Table 1).

[0086] Comparative Example 1 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap electric arc furnace, which is similar to Example 1, except that: in S1, the all-scrap steel is low-sulfur scrap steel. The remaining conditions are the same as in Example 1 and will not be repeated.

[0087] Comparative Example 2 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 14Mn (chemical composition of which is shown in Table 1) in an all-scrap electric arc furnace, which is similar to Example 2, except that: in S1, the all-scrap steel is composed of 65% ordinary scrap steel and 35% low sulfur briquettes. Specifically, the following steps are included: S1, ingredients: The whole scrap steel consists of the following raw materials in percentage by mass: 65% of ordinary scrap steel and 35% of low-sulfur briquettes.

[0088] Among them, the sulfur content of ordinary scrap steel is 0.025%, and the sulfur content of low-sulfur scrap steel is 0.008%.

[0089] S2~S3 are the same as those in Example 2 and will not be described in detail.

[0090] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced with a flow rate of 270NL / min. 5.5kg / t lime, 0.2kg / t aluminum particles and 0.5kg / t silicon carbide are added to make white slag (12min). The chemical composition of the refining slag system is controlled (including CaO 62.1%, SiO27.2%, Al2O327%, MgO 3.1%, FeO+MnO=0.35%), and white slag refining is carried out for 30min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0091] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0012%, adjust the aluminum content of the molten steel to 0.05%, and the superheat is 120℃ before tapping.

[0092] S5~S6 are the same as those in Example 2 and will not be described in detail.

[0093] Comparative Example 3 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap electric arc furnace, which is similar to Example 1, except that: in S2, when the molten pool temperature is 1560℃~1610℃, no carbon spraying is performed. Specifically, the following steps are included: S1, ingredients: same as in Example 1, no further details are given.

[0094] S2, electric arc furnace smelting: The raw materials are smelted in an electric arc furnace. When the molten pool temperature is ≤1560℃, the oxygen supply intensity is 60Nm 3 / (h·t); When the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 95Nm 3 / (h·t); When the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 60Nm 3 / (h·t); when tapping, the carbon content of the molten steel is 0.03%.

[0095] S3, slag making and deoxidation of molten steel: When the steel is tapped to 10% of the total mass of the molten steel, add 3.2kg / t aluminum ingots into the ladle; When the steel is tapped to 40% of the total mass of the molten steel, 4.5kg / t of pre-melted refined slag and 1.8kg / t of fluorite are added to the ladle. The pre-melted refined slag includes the following chemical components in percentage by mass: CaO 36%, SiO27%, Al2O350% and MgO0.7%; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel is 50%, add 6.0kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, 0.4kg / t of aluminum wire is added to the ladle to control the aluminum content in the molten steel to 0.055% (at this time, the dissolved oxygen content is 0.00045%).

[0096] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced at a flow rate of 250NL / min. 5.2kg / t lime, 0.25kg / t aluminum particles and 0.4kg / t silicon carbide are added to make white slag (12min), and the chemical composition of the refining slag system is controlled (including CaO 59.3%, SiO27%, Al2O328.4%, MgO 4.1%, FeO+MnO=0.4%). White slag refining is carried out for 35min, and the aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0097] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0010% (the sulfur content of the molten steel cannot reach below 0.0008%), adjust the aluminum content of the molten steel to 0.04%, the superheat is 130℃, and the steel is tapped.

[0098] S5~S6 are the same as those in Example 1 and will not be described in detail.

[0099] Comparative Example 4 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet L245NCS (its chemical composition is shown in Table 1) in an all-scrap steel electric arc furnace, which is similar to Example 3, except that: in S2, the oxygen supply intensity is 40Nm 3 / (h·t). Specifically, it includes the following steps: S1, ingredients: same as in Example 3, no further details are given.

[0100] S2, electric arc furnace smelting: The raw materials are smelted in an electric arc furnace. When the molten pool temperature is ≤1560℃, the oxygen supply intensity is 40Nm 3 / (h·t); When the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 40Nm 3 / (h·t), while carbon is sprayed at a rate of 0.6kg / (min·t); When the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 40Nm 3 / (h·t), steel is tapped when the carbon content of the molten steel is 0.045% (the carbon content of the molten steel cannot reach above 0.05%).

[0101] S3, slag making and deoxidation of molten steel: When the steel is tapped to 15% of the total mass of the molten steel, add 3.5kg / t aluminum ingots into the ladle; When the steel is tapped to 45% of the total mass of the molten steel, 5kg / t of pre-melted refined slag and 1.5kg / t of fluorite are added to the ladle. The pre-melted refined slag includes the following chemical components in percentage by mass: CaO 32%, SiO28%, Al2O354% and MgO0.7%; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel reaches 55%, add 6.5kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, 0.5kg / t of aluminum wire is added to the ladle to control the aluminum content in the molten steel to 0.058% (at this time, the dissolved oxygen content is 0.00035%).

[0102] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced with a flow rate of 230NL / min. 5kg / t lime, 0.3kg / t aluminum particles and 0.3kg / t silicon carbide are added to make white slag (15min). The chemical composition of the refining slag system is controlled (including CaO 59.1%, SiO27.6%, Al2O327.3%, MgO 5%, FeO+MnO=0.3%), and white slag refining is carried out for 40min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0103] When the power supply temperature is 1570℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0010% (the sulfur content of the molten steel cannot reach below 0.0008%), adjust the aluminum content of the molten steel to 0.04%, the superheat is 140℃, and the steel is tapped.

[0104] S5~S6 are the same as those in Example 3 and will not be described in detail.

[0105] Comparative Example 5 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap steel electric arc furnace, which is similar to Example 1, except that: in S3, the timing of adding aluminum ingots is when the steel is tapped to 20% of the total mass of the molten steel. Specifically, the following steps are included: S1~S2 are the same as those in Example 1 and will not be described in detail.

[0106] S3, slag making and deoxidation of molten steel: When the steel is tapped to 20% of the total mass of the molten steel, add 3.2kg / t aluminum ingots into the ladle; When the steel is tapped to 40% of the total mass of the molten steel, 4.5kg / t of pre-melted refined slag and 1.8kg / t of fluorite are added to the ladle. The pre-melted refined slag includes the following chemical components in percentage by mass: CaO 36%, SiO27%, Al2O350% and MgO0.7%; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel is 50%, add 6.0kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, 0.4kg / t of aluminum wire is added to the ladle to control the aluminum content in the molten steel to 0.05% (at this time, the dissolved oxygen content is 0.00045%).

[0107] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced with a flow rate of 250NL / min. 5.2kg / t lime, 0.25kg / t aluminum particles and 0.4kg / t silicon carbide are added to make white slag (12min). The chemical composition of the refining slag system is controlled (including CaO 60%, SiO27.8%, Al2O327.9%, MgO 3.4%, FeO+MnO=0.4%), and white slag refining is carried out for 35min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0108] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0012% (the sulfur content of the molten steel cannot reach below 0.0008%), adjust the aluminum content of the molten steel to 0.04%, the superheat is 130℃, and the steel is tapped.

[0109] S5~S6 are the same as those in Example 1 and will not be described in detail.

[0110] Comparative Example 6 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap electric arc furnace, which is similar to Example 1, except that: in S3, the timing of adding pre-melted refined slag is when the steel is tapped to 25% of the total mass of the molten steel. Specifically, the following steps are included: S1~S2 are the same as those in Example 1 and will not be described in detail.

[0111] S3, slag making and deoxidation of molten steel: When the steel is tapped to 10% of the total mass of the molten steel, add 3.2kg / t aluminum ingots into the ladle; When the steel is tapped to 25% of the total mass of the molten steel, 4.5kg / t of pre-melted refined slag is added to the ladle. The pre-melted refined slag includes the following chemical components by mass percentage: CaO 36%, SiO27%, Al2O350% and MgO0.7%; When the steel is tapped to 40% of the total mass of the molten steel, 1.8kg / t of fluorite is added to the ladle; and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel is 50%, add 6.0kg / t lime into the ladle; When the steel is tapped to 100% of the total mass of the molten steel, add 0.4kg / t of aluminum wire into the ladle to control the aluminum content in the molten steel to 0.055% and the dissolved oxygen content to 0.00026%.

[0112] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced at a flow rate of 250NL / min. 5.2kg / t lime, 0.25kg / t aluminum particles and 0.4kg / t silicon carbide are added to make white slag (12min). The chemical composition of the refining slag system is controlled (including CaO 59.1%, SiO27.2%, Al2O328.5%, MgO 4.3%, FeO+MnO=0.5%), and white slag refining is carried out for 35min. The aluminum content of the molten steel during the refining process is controlled to be 0.03%~0.04%.

[0113] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0013% (the sulfur content of the molten steel cannot reach below 0.0008%), adjust the aluminum content of the molten steel to 0.04%, the superheat is 130℃, and the steel is tapped.

[0114] S5~S6 are the same as those in Example 1 and will not be described in detail.

[0115] Comparative Example 7 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (its chemical composition is shown in Table 1) in an all-scrap steel electric arc furnace, which is similar to Example 1, except that: in S4, the aluminum content of the molten steel during the refining process is controlled to be 0.07%. Specifically, the following steps are included: S1~S3 are the same as those in Example 1 and will not be described in detail.

[0116] S4, LF Refining: The molten steel in the ladle is transferred to the refining furnace, and power is supplied and argon is introduced with a flow rate of 250NL / min. 5.2kg / t lime, 0.25kg / t aluminum particles and 0.4kg / t silicon carbide are added to make white slag (12min). The chemical composition of the refining slag system is controlled (including CaO 59.9%, SiO27.6%, Al2O327.9%, MgO 4%, FeO+MnO=0.4%), and white slag refining is carried out for 35min. The aluminum content of the molten steel during the refining process is controlled to be 0.02%.

[0117] When the power supply temperature is 1560℃, take a spectrum sample for analysis and adjust the chemical composition to the target composition. When the sulfur content of the molten steel is 0.0008%, adjust the aluminum content of the molten steel to 0.07%, and the superheat is 130℃ before tapping.

[0118] S5~S6 are the same as those in Example 1 and will not be described in detail.

[0119] Comparative Example 8 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap electric arc furnace, which is similar to Example 1, except that: in S5, the top slag of the molten steel after LF refining is not treated. Specifically, the following steps are included: S1 to S4 are the same as those in Example 1 and will not be described in detail.

[0120] S5, VD vacuum smelting: The molten steel after LF refining was transferred to a vacuum smelting furnace, and argon was introduced for vacuum smelting for 18 minutes. When the vacuum degree was > 67 kPa, the flow rate of the argon was 11 NL / min; when the vacuum degree was ≤ 67 kPa, the flow rate of the argon was 60 NL / min. After breaking the air, 0.41 kg / t silicon calcium wire was fed and soft blowing was performed for 21 minutes (flow rate was 5 NL / min).

[0121] S6, continuous casting of peritectic steel round billets: same as in Example 1, no further details are given.

[0122] Comparative Example 9 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap electric arc furnace, which is similar to Example 1, except that: in S5, 60wt% of the top slag of the molten steel after LF refining is poured out. Specifically, the method comprises the following steps: S1 to S4 are the same as those in Example 1 and will not be described in detail.

[0123] S5, VD vacuum smelting: 60wt% of the top slag of the molten steel after LF refining was poured off and transferred to a vacuum smelting furnace. Argon was introduced for vacuum smelting for 18 minutes. When the vacuum degree was > 67kPa, the flow rate of the argon was 11NL / min; when the vacuum degree was ≤ 67kPa, the flow rate of the argon was 60NL / min. After breaking the air, 0.41kg / t silicon calcium wire was fed and soft-blown for 21 minutes (flow rate was 5NL / min).

[0124] S6, continuous casting of peritectic steel round billets: same as in Example 1, no further details are given.

[0125] Comparative Example 10 This comparative example provides a method for producing ultra-low sulfur peritectic steel continuous casting round billet 12MnV (chemical composition of which is shown in Table 1) in an all-scrap steel electric arc furnace, which is similar to Example 1, except that: in S6, no high basicity low sulfur carbon-free covering agent is added. The other conditions are the same as in Example 1 and will not be repeated.

[0126] Table 1 Chemical composition of ultra-low sulfur peritectic steel continuous casting round billet in the examples and comparative examples (%)

[0127] Verification test The inclusion conditions and low-power mass conditions of the ultra-low sulfur peritectic steel continuous casting round billets provided in Examples 1 to 4 and Comparative Examples 1 to 10 were tested with reference to GB / T 10561-2023 and YB / T 4149-2018, respectively. The test results are shown in Tables 2 to 3.

[0128] Table 2 Inclusions in the ultra-low sulfur peritectic steel continuous casting round billets of the embodiments and comparative examples

[0129] Table 3 Macrostructure rating results of ultra-low sulfur peritectic steel continuous casting round billets of the embodiments and comparative examples

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace, characterized in that: The following steps are involved: S1, ingredients: All scrap steel includes the following raw materials by mass percentage: 40%~55% of ordinary scrap steel and 45%~60% of low-sulfur scrap steel; The sulfur content of the ordinary scrap steel is 0.01% to 0.03%, and the sulfur content of the low-sulfur scrap steel is ≤ 0.01%; S2, electric arc furnace smelting: The raw materials were smelted in an electric arc furnace with an oxygen supply intensity of 50 Nm 3 / (h·t)~110Nm 3 / (h·t); When the molten pool temperature is 1580℃~1610℃, carbon spray is performed; the carbon content of the molten steel is controlled to be 0.05%~0.07% during tapping; S3, slag making and deoxidation of molten steel: When the steel is tapped to 5% to 15% of the total mass of the molten steel, add aluminum ingots to the ladle; When the steel is tapped to 35% to 45% of the total mass of the molten steel, pre-melted refined slag and fluorite are added to the ladle, and silicon-manganese alloy and high-manganese alloy are added to adjust the chemical composition; When the total mass of molten steel reaches 45% to 55%, lime is added to the ladle; When the total mass of the molten steel reaches 100%, add aluminum wire into the ladle to control the aluminum content in the molten steel to ≥ 0.05% and the dissolved oxygen content to ≤ 0.0003%; S4, LF Refining: The molten steel in the ladle is transferred to a refining furnace, power is supplied and argon is introduced, lime, aluminum particles and silicon carbide are added to make white slag, and white slag refining is performed, and the aluminum content of the molten steel is controlled to be ≥0.03% during the refining process; When the sulfur content of the molten steel is ≤0.0008%, the aluminum content of the molten steel is adjusted to 0.04%~0.05%, the superheat is 120℃~140℃, and the steel is tapped; S5, VD vacuum smelting: 40wt% to 50wt% of the top slag of the molten steel after LF refining is poured off, and the molten steel is transferred to a vacuum smelting furnace, and argon gas is introduced for vacuum smelting; after breaking the air, calcium silicon wire is fed and soft-blown; S6, continuous casting of peritectic steel round billets: The soft-blown molten steel is transferred to a tundish, a high-basicity, low-sulfur, carbon-free covering agent is added, and continuous steel casting is performed. The steel is cooled to obtain an ultra-low-sulfur peritectic steel continuous casting round billet.

2. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1, characterized in that: In S1, the low-sulfur scrap steel includes low-sulfur briquettes, and the mass of the low-sulfur briquettes accounts for 35% to 40% of the total scrap steel.

3. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1, characterized in that: In S2, when the molten pool temperature is ≤1560℃, the oxygen supply intensity is 50Nm 3 / (h·t)~70Nm 3 / (h·t); when the molten pool temperature is 1560℃~1610℃, the oxygen supply intensity is 80Nm 3 / (h·t)~110Nm 3 / (h·t); when the molten pool temperature is 1610℃~1650℃, the oxygen supply intensity is 50Nm 3 / (h·t)~70Nm 3 / (h·t); In S2, the carbon injection rate is 0.6 kg / (min·t) to 0.9 kg / (min·t).

4. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1, characterized in that: In S3, the pre-melted refined slag includes the following chemical components in percentage by mass: CaO 32%-40%, SiO2≤10%, Al2O346%-54% and MgO≤1%; In S4, during the white slag refining process, the refined slag system includes the following chemical components in percentage by mass: CaO 59%~62.5%, SiO2 7%~10%, Al2O3 27%~29%, MgO 3%~5%, FeO+MnO≤0.5%; In S6, the high basicity, low sulfur and carbon-free covering agent includes the following chemical components in percentage by mass: CaO 33%~43%, SiO2 7%~17%, Al2O3 18%~28%, MgO 3.5%~7.5% and S≤0.2%.

5. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1 or 4, characterized in that: In S3, the amount of the aluminum ingot added is 3kg / t to 3.5kg / t; In S3, the amount of pre-melted refined slag added is 4kg / t~5kg / t; In S3, the amount of fluorite added is 1.5kg / t~2kg / t; In S3, the amount of lime added is 5.5kg / t~6.5kg / t; In S3, the amount of the aluminum wire added is 0.3kg / t to 0.5kg / t.

6. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1 or 4, characterized in that: In S4, the flow rate of the argon gas is 230NL / min~270NL / min; In S4, the amount of lime added is 5kg / t~5.5kg / t; In S4, the amount of aluminum particles added is 0.2kg / t to 0.3kg / t; In S4, the amount of silicon carbide added is 0.3kg / t to 0.5kg / t; In S4, the time for making white slag is 10min~15min; In S4, the white slag refining time is ≥20 min.

7. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1, characterized in that: In S5, when the vacuum degree is greater than 67 kPa, the flow rate of the argon gas is 6 NL / min to 16 NL / min; when the vacuum degree is less than or equal to 67 kPa, the flow rate of the argon gas is 40 NL / min to 80 NL / min.

8. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1 or 7, characterized in that: In S5, the vacuum smelting time is ≥15min; In S5, the amount of calcium silicon wire added is 0.35kg / t~0.5kg / t; In S5, the flow rate of the soft blowing is 3NL / min~6NL / min, and the soft blowing time is ≥20min.

9. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 1 or 4, characterized in that: In S6, the superheat of the molten steel in the tundish is 18°C ​​to 28°C; In S6, the addition amount of the high basicity, low sulfur and carbon-free covering agent is 1.3kg / t to 1.5kg / t; In S6, the continuous casting speed of the continuous cast steel is 1.5m / min~1.75m / min; the diameter of the ultra-low sulfur peritectic steel continuous casting round billet is 180mm~220mm; In S6, during the continuous steel casting process, the specific water volume is 0.32L / kg~0.36L / kg, and the mass proportion of cooling water in the secondary cooling zone is 23.5%~34.5%, 33%~33.8%, 22.5%~23.5%, 11.5%~12.5% ​​and 7.4%~7.9% respectively.

10. The method for producing ultra-low sulfur peritectic steel continuous casting round billets using a full scrap steel electric arc furnace as claimed in claim 9, characterized in that: In S6, the continuous steel casting adopts a continuous casting crystallizer; The protective slag of the continuous casting crystallizer includes the following chemical components in percentage by mass: CaO 33.8% to 39.8%, SiO2 27.6% to 33.6%, Al2O3 5% to 9%, Na2O+K2O 2% to 4%; the melting point of the protective slag is 1170° C. to 1270° C., and the viscosity of the protective slag is 0.43 Pa·s to 0.57 Pa·s; The water flow rate of the continuous casting crystallizer is 105Nm 3 / h~115Nm 3 / h; The electromagnetic stirring current of the continuous casting crystallizer is 350A~370A, and the terminal electromagnetic stirring current is 380A~400A.

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