Method for producing carbon structural steel containing nickel, chromium and manganese

Abstract

The invention provides a method for manufacturing a carbon structural steel containing nickel, chromium and manganese. The chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.15-0.20Wt%, Si: 0.15-0.30Wt%, Mn: 0.50-0.70Wt%, Cr: 0.60-0.80Wt%, Ni: 0.35-0.45Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the balance is Fe and inevitable trace elements; the method for manufacturing the carbon structural steel containing nickel, chromium and manganese comprises the following process steps which are carried out in sequence: laterite nickel ore sintering ore→primary refining furnace→low nickel, chromium and manganese molten iron+steelmaking pig iron→AOD refining furnace smelting slag and oxygen blowing dephosphorization→ladle refining furnace refining treatment→double-stream slab continuous casting→hot rolling. The present invention breaks the process concept limitation of producing common carbon structural steel by traditional electric furnace or converter smelting, and solves the technical problem that AOD refining furnace smelting cannot dephosphorize.

Description

[0001] This invention is a divisional application. The name of the parent case is: A carbon structural steel containing nickel, chromium and manganese and its manufacturing method. The application date is October 18, 2022. The application number is 2022112714882. Technical Field

[0002] The invention relates to the field of steel smelting production, and in particular to a method for manufacturing carbon structural steel containing nickel, chromium and manganese. Background Art

[0003] At present, ordinary carbon structural steel uses blast furnace iron or scrap steel as the main raw material, and is smelted in oxygen converter or electric furnace through decarburization, desiliconization, dephosphorization and other smelting operations to produce qualified molten steel, whose chromium, nickel and copper content is not more than 0.3%. However, laterite nickel ore iron obtained by smelting laterite nickel ore in primary furnace is often not suitable for smelting ordinary carbon structural steel because it contains high chromium, manganese and nickel alloy elements; at the same time, AOD refining furnace is generally used for smelting and producing chromium-containing stainless steel because of its good decarburization and chromium preservation function. Since the whole process is always reacting in a reducing atmosphere, it has no dephosphorization ability at all.

[0004] In summary, the existing technology has the following problems: the nickel-chromium content of ordinary carbon structural steel is less than 0.3%, and it is all produced by traditional electric furnace or converter smelting; AOD refining furnace smelting technology cannot dephosphorize. Summary of the invention

[0005] The present invention provides a common carbon structural steel (carbon steel) and a method for manufacturing the same, in particular, a carbon structural steel containing nickel, chromium and manganese and a method for manufacturing the same, which breaks the process concept limitation of producing common carbon structural steel by traditional electric furnace or converter smelting, and solves the technical problem that dephosphorization cannot be performed by AOD refining furnace smelting.

[0006] To this end, the present invention provides a carbon structural steel containing nickel, chromium and manganese and a manufacturing method thereof, wherein the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.15-0.20Wt%, Si: 0.15-0.30Wt%, Mn: 0.50-0.70Wt%, Cr: 0.60-0.80Wt%, Ni: 0.35-0.45Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the balance is Fe and inevitable trace elements.

[0007] The nickel-chromium-manganese-containing carbon structural steel and the manufacturing method thereof use laterite nickel ore as a raw material, and include the following process steps performed in sequence:

[0008] Laterite nickel ore sintering → primary smelting furnace → low nickel chromium manganese iron water + steelmaking pig iron → AOD refining furnace smelting slag and oxygen blowing dephosphorization → ladle refining furnace refining treatment (LF refining treatment) → double-strand slab continuous casting → hot rolling;

[0009] Among them, the slag making and oxygen blowing dephosphorization of the AOD refining furnace include two steps: S1: in the early stage of smelting, the production raw materials are deoxidized, decarbonized and desiliconized to a certain stage, quicklime is added to make slag, and slag is removed and poured; S2: strong oxygen supply, quicklime is added after the slag is poured in S1 for secondary slag making, and then the slag is removed;

[0010] The secondary slag making comprises the following steps: firstly using the side gun as the main blower → after the lime to be added is melted, the top gun is used for re-blowing, and then the slag basicity is controlled through the oxidation period, wherein the dephosphorization is mainly carried out by increasing the oxidizability in the early and middle stages of oxidation, and the dephosphorization is carried out according to the carbon content in the final stage of oxidation.

[0011] Furthermore, the slag basicity is controlled at 3.5-4.5.

[0012] Furthermore, when the carbon content is ≤0.10%, the temperature is measured and samples are taken during the furnace pouring, and fluorite is added to adjust the final slag according to the fluidity of the slag; when the carbon content is ≤0.04%, the oxygen supply is stopped, a small amount of ferrosilicon is added to shallowly reduce the chromium-containing slag, the temperature is measured and samples are taken during the furnace pouring, and the slag removal operation is carried out after the phosphorus content meets the requirements.

[0013] Furthermore, the working parameters of the top gun are: working pressure is 6-8 kg, and the gun position is controlled at 1700-2000 mm.

[0014] Furthermore, after the slag discharge in S1 is completed, the amount of quicklime added is 6%-10% of the total loading amount.

[0015] Furthermore, the amount of fluorite added is ≤ 2% of the total loading amount.

[0016] Furthermore, the hot rolling process parameters are: preheating section temperature 700-800°C, heating section temperature 1220-1250°C, soaking section temperature 1200-1230°C, furnace time ≥180min; a four-stand rough rolling + nine-stand finishing hot rolling mill is used, the intermediate billet thickness is 36mm, the final rolling temperature is controlled at 940-1000°C, the curling temperature is 680-720°C, and air cooling is used.

[0017] Furthermore, the smelting in the AOD refining furnace includes: a steelmaking period, during which the weight of ordinary pig iron added at a time is ≤8 tons, which is added in 6 times. After adding materials such as ferrosilicon and silicon carbon balls and heating up, 8-8.5 tons of lime are added for slagging, and the amount of ferrosilicon + silicon carbon balls added is 3.2-3.5 tons; the slag is poured after slagging, and the basicity is controlled at 1.2-1.6. The temperature of the molten steel at the end of the steelmaking period is: 1700℃≤ΔTc+T≤1750℃, where ΔTc is the temperature difference of the molten steel corresponding to different carbon contents, and T is the initial temperature of the steelmaking period.

[0018] Furthermore, the AOD refining furnace smelting also includes: steel tapping, wherein: the composition and temperature of the molten steel reach the control target, the steel tapping temperature is 1580-1610°C, and 0.5kg / t ferrosilicon powder or 0.15kg / t high aluminum iron is added with the steel flow for deoxidation during the steel tapping process.

[0019] The present invention also provides a carbon structural steel containing nickel, chromium and manganese, which is made according to any one of the above steps. The chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.15-0.20Wt%, Si: 0.15-0.30Wt%, Mn: 0.50-0.70Wt%, Cr: 0.60-0.80Wt%, Ni: 0.35-0.45Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the balance is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0020] Furthermore, the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.15-0.17Wt%, Si: 0.15-0.24Wt%, Mn: 0.50-0.58Wt%, Cr: 0.60-0.67Wt%, Ni: 0.35-0.39Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the remainder is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0021] Furthermore, the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.17-0.18Wt%, Si: 0.24-0.2Wt%, Mn: 0.58-0.63Wt%, Cr: 0.67-0.72Wt%, Ni: 0.39-0.43Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the remainder is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0022] Furthermore, the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.18-0.20Wt%, Si: 0.25-0.30Wt%, Mn: 0.63-0.70Wt%, Cr: 0.72-0.80Wt%, Ni: 0.43-0.45Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the remainder is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0023] Furthermore, the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.18Wt%, Si: 0.24Wt%, Mn: 0.61Wt%, Cr: 0.71Wt%, Ni: 0.41Wt%, P: 0.034Wt%, S: 0.014Wt%, Alt: 0.006Wt%, N: 0.003Wt%; the remainder is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0024] Furthermore, the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.17Wt%, Si: 0.25Wt%, Mn: 0.58Wt%, Cr: 0.67Wt%, Ni: 0.39Wt%, P: 0.032Wt%, S: 0.013Wt%, Alt: 0.005Wt%, N: 0.005Wt%; the remainder is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0025] Furthermore, the chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.17Wt%, Si: 0.24Wt%, Mn: 0.63Wt%, Cr: 0.72Wt%, Ni: 0.43Wt%, P: 0.035Wt%, S: 0.014Wt%, Alt: 0.005Wt%, N: 0.006Wt%; the remainder is Fe and inevitable trace elements; the carbon structural steel containing nickel, chromium and manganese is a steel strip.

[0026] The beneficial effects of the present invention are as follows: the present invention breaks the process concept limitation of the traditional electric furnace or converter smelting to produce ordinary carbon structural steel, uses laterite nickel ore molten iron + steelmaking pig iron as the main raw material for the first time, adopts AOD refining furnace as the main smelting equipment, and develops the key technology of smelting dephosphorization in AOD refining furnace. The present invention reduces the nitrogen and argon pressures in the smelting process, ensures the oxygen blowing operation on the top side, forms an oxidizing atmosphere, and achieves the reaction atmosphere required for dephosphorization, and then creates thermodynamic conditions of high basicity, large slag volume, and high oxidizability. During this period, the effect of strong combined blowing of the top gun and the side gun is used to strengthen the reaction of the steel slag interface, forming better kinetic conditions, and finally removing the phosphorus element in the molten steel under the joint action of multiple conditions, thereby achieving the purpose of dephosphorization using the AOD refining furnace, and solving the problem of having to use electric furnace or converter smelting to produce ordinary carbon structural steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A metallographic photograph of the substrate structure of the present invention;

[0028] Figure 2 A metallographic photograph of the heat-affected zone structure of the present invention;

[0029] Figure 3 It is a metallographic photograph of the weld structure of the present invention. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the present invention is now described.

[0031] The invention provides a carbon structural steel containing nickel, chromium and manganese and a manufacturing method thereof. The hot-rolled product has a yield strength Rp0.2 of 400-420 MPa, a tensile strength Rm of 510-540 MPa, an elongation A≥27%, excellent cold bending and wide cold bending performance d=2a, and meets welding performance requirements.

[0032] The adopted technical solution is: a carbon structural steel containing nickel, chromium and manganese, the chemical composition weight percentage of the steel is C: 0.15-0.20Wt%, Si: 0.15-0.30Wt%, Mn: 0.50-0.70Wt%, Cr: 0.60-0.80Wt%, Ni: 0.35-0.45Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the balance is Fe and inevitable trace elements.

[0033] 1. AOD refining furnace smelting

[0034] AOD is the abbreviation of argon oxygen decarburization. The technical conditions for dephosphorization include high basicity, high oxidizability, large slag volume and low temperature, while the AOD refining furnace is commonly used for chromium-containing stainless steel smelting. Its reducing atmosphere process requirements for decarburization and chromium preservation do not have the efficiency of decarburization and desiliconization of converters or electric furnaces (arc furnaces), and cannot quickly produce high-FeO, high-basicity dephosphorization slag, and the dephosphorization effect is poor; at the same time, the raw material used in the AOD refining furnace is pre-treated primary molten steel, and its furnace design does not have slag-making space with high basicity and large slag volume after molten iron desiliconization, which is easy to splash. Therefore, the present invention develops a dephosphorization slag-making and oxygen supply system for the AOD refining furnace.

[0035] The slag making and oxygen blowing dephosphorization of the AOD refining furnace (AOD argon oxygen refining furnace) include two steps: S1: In the early stage of smelting, the production raw materials are deoxidized, decarbonized and desiliconized to a certain stage, and a small amount of scrap steel is added to digest the chemical heat generated by decarbonization and desiliconization. Quicklime is added to make slag and slag removal is performed to remove a large amount of SiO2 produced by desiliconization, creating conditions for the subsequent rapid production of high-basicity slag, and then the slag is dumped; S2: Strong oxygen supply for rapid decarbonization and desiliconization. Since a large amount of carbon and silicon are removed in the early stage, quicklime is added after the S1 slag dumping for secondary slag making, which can quickly produce high-basicity, high-oxidizability slag for rapid dephosphorization, and then the slag is dumped. The specific steps of AOD refining furnace smelting are as follows:

[0036] (1) Requirements for molten iron, scrap steel and energy medium: The composition, range and temperature of laterite nickel ore molten iron are shown in Table 1. The amount of laterite nickel ore molten iron added is 18 tons, and the steelmaking pig iron is 42 tons. The composition and range of steelmaking pig iron (ordinary pig iron) are shown in Table 2. The total loading is controlled at 60 tons. Silicon carbon balls or ferrosilicon are added to compensate for the heat for blowing and heating. The oxygen, nitrogen and argon pressure is 16-18Mpa.

[0037] Table 1: Laterite nickel ore molten iron conditions

[0038]

[0039] Table 2: Pig iron for steelmaking

[0040] Composition of steelmaking pig iron Si Mn P S scope(%) 0.3～0.7 0.1～0.3 1.1～1.3 0.1～0.3

[0041] (2) Steelmaking period: the weight of ordinary pig iron added at a time is ≤8 tons, which is added in 6 times. After adding ferrosilicon, silicon carbon balls and other materials and heating them up, 8-8.5 tons of lime are added for slagging. The amount of ferrosilicon + silicon carbon balls added is 3.2-3.5 tons. After slagging, the slag is poured out and the basicity is controlled at 1.2-1.6. The temperature of the molten steel at the end of the steelmaking period is: 1700℃≤ΔTc+T≤1750℃, where ΔTc is the temperature difference of the molten steel corresponding to different carbon contents, and T is the initial temperature of the steelmaking period.

[0042] (3) Oxidation period: mainly dephosphorization, the specific operation is as follows: after the S1 slag is poured, 4-6 tons of lime are added to carry out slag making and dephosphorization. During the secondary slag making, the side gun is mainly used. After the added lime is melted, the top and side combined blowing is used for blowing. Among them, the main focus is on creating an oxidizing atmosphere in the early and middle stages of oxidation. Carbon is not controlled at the end of the late oxidation stage, and dephosphorization is mainly carried out by increasing oxidizability. At the end of oxidation, when the carbon content is ≤0.10%, the furnace is poured and the temperature is measured and sampled, and fluorite is added according to the slag fluidity. Adjust the final slag, add fluorite at a rate of 0.8kg-1.2t; stop supplying oxygen when decarburization reaches ≤0.04%. Since the chromium oxide in the chromium-containing dephosphorization slag from the laterite nickel ore molten iron is not easy to remove, the slag is shallowly reduced before slagging, that is, a small amount of ferrosilicon or silicon carbon balls is added to shallowly reduce the chromium-containing slag to increase slag fluidity and improve the slag removal effect. At the same time, in order to prevent rephosphorization, the degree of shallow reduction must be strictly controlled, and then the furnace temperature is measured and sampled. After the phosphorus content meets the requirements, the slag is slagging.

[0043] The working parameters of the top gun are as follows: working pressure is 6-8 kg, and the gun position is controlled at 1700-2000 mm. The side gun mainly provides nitrogen or nitrogen-oxygen mixed gas to enhance stirring; the slag basicity during the oxidation period is controlled at 3.5-4.5.

[0044] (4) Reduction period: After slagging, ferrosilicon is added for deoxidation and alloying. The reduction temperature is controlled at 1620-1650℃, and the reduction is carried out for 3 minutes to take samples, measure the temperature and slag.

[0045] (5) LF refining treatment: LF refining for 3 minutes, and the steel is tapped after reaching the tapping conditions.

[0046] (6) Steel tapping: The composition and temperature of the molten steel reach the control target, the tapping temperature is 1580-1610℃, and 0.5kg / t ferrosilicon powder or 0.15kg / t high aluminum iron is added with the steel flow for deoxidation.

[0047] 2. Hot rolling (hot rolling)

[0048] The heating temperature system of the casting billet is as follows: the temperature of the preheating section is 700-800℃, the temperature of the heating section is 1220-1250℃, the temperature of the soaking section is 1200-1230℃, and the time in the furnace is ≥180min to ensure that the alloying elements are fully dissolved in the casting billet during the insulation time in the furnace; a four-stand rough rolling + nine-stand finishing hot rolling mill is used, the intermediate billet thickness is 36mm, the final rolling temperature is controlled at 940-1000℃, the coiling temperature is 680-720℃, and air cooling is used.

[0049] 3. Example

[0050] (1) The method for producing nickel-chromium-manganese-carbon structural steel of the present invention adopts the following composition ratios. Table 3 shows the chemical composition (by weight percentage) of the products of each embodiment.

[0051] Table 3: Chemical composition of each example (%)

[0052] Examples C Si Mn P S Alt N Ni Cr Example 1 0.18 0.24 0.61 0.034 0.014 0.006 0.003 0.41 0.71 Example 2 0.17 0.25 0.58 0.032 0.013 0.005 0.005 0.39 0.67 Example 3 0.17 0.24 0.63 0.035 0.014 0.005 0.006 0.43 0.72

[0053] (2) The specific process parameters for rolling nickel-chromium-manganese-carbon structural steel with a rolling specification of 2.5 mm×620 mm are shown in Table 4, which is the process parameters corresponding to the embodiments described in Table 3.

[0054] Table 4: Specific hot rolling process parameters of each embodiment

[0055]

[0056] (3) The carbon structural steel containing nickel, chromium and manganese in the present invention is a steel strip, and its detailed mechanical properties are shown in Table 5; the tensile strength Rm of the welded joint of the carbon structural steel strip containing nickel, chromium and manganese is 510-550Mpa, the yield strength Rp0.2 is 380-420Mpa, the bending test meets the standard, and the welding performance meets the requirements; the detailed mechanical properties of the welded joint of the carbon structural steel strip containing nickel, chromium and manganese are shown in Table 6. Tables 5 and 6 are the test results of samples randomly selected from the embodiments in Table 3.

[0057] Table 5: Properties of hot-rolled carbon structural steel strip containing nickel, chromium and manganese

[0058] Examples Tensile strength / Mpa Yield strength / Mpa Elongation A / % Cold bending, wide cold bending performance d = 2a Implementation 1 524 408 27.1 qualified Implementation 2 521 417 30.7 qualified Implementation 3 530 409 28.0 qualified

[0059] Table 6: Mechanical properties of welded joints of carbon structural steel strips containing nickel, chromium and manganese

[0060]

[0061] The metallographic structure and hardness results of the weld of the welded joint of the nickel-chromium-manganese carbon structural steel strip are shown in Table 7, which is the test results of the example in Table 6. Among them, P: pearlite; F: ferrite; B: bainite; AF: acicular ferrite, and the metallographic photos of the substrate structure are shown in Figure 1 , heat affected zone microstructure photo see Figure 2 , metallographic photos of weld structure are shown in Figure 3 .

[0062] Table 7: Metallographic structure and hardness of weld

[0063]

[0064] The present invention breaks the limitation of the traditional electric furnace or converter smelting process for producing carbon steel. It uses laterite nickel ore molten iron + steelmaking pig iron as the main raw materials for the first time, adopts AOD refining furnace as the main smelting equipment, and develops the key technology of smelting and dephosphorization in AOD refining furnace. This project reduces the nitrogen and argon pressures in the smelting process, ensures the oxygen blowing operation on the top side, forms an oxidizing atmosphere, and achieves the reaction atmosphere required for dephosphorization; then creates thermodynamic conditions of high alkalinity, large slag volume, and high oxidation; during this period, the effect of strong combined blowing of the top gun and the side gun is used to strengthen the reaction of the steel slag interface and form better kinetic conditions. Under the joint action of multiple conditions, the phosphorus element in the molten steel is finally removed, thereby achieving the purpose of dephosphorization using AOD refining furnace, and solving the problem of having to use electric arc furnace or converter smelting to produce carbon steel. The nickel-chromium-manganese carbon structural steel obtained by the present invention has a yield strength Rp0.2 of 400-420Mpa, a tensile strength Rm of 510-540Mpa, an elongation A≥27%, excellent cold bending and wide cold bending test (d=2a) performance, and welding performance that meets the requirements. The nickel-chromium-manganese carbon structural steel has high tolerance and can be applied to general structural steel.

[0065] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. The components of the present invention can be combined with each other without conflict, and any equivalent changes and modifications made by any technician in the field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for producing a carbon structural steel containing nickel, chromium and manganese, characterized in that: The chemical composition weight percentage of the carbon structural steel containing nickel, chromium and manganese is: C: 0.15-0.20Wt%, Si: 0.15-0.30Wt%, Mn: 0.50-0.70Wt%, Cr: 0.60-0.80Wt%, Ni: 0.35-0.45Wt%, P≤0.040Wt%, S≤0.015Wt%, Alt≤0.008Wt%, N≤0.008Wt%; the balance is Fe and inevitable trace elements; The method for manufacturing the carbon structural steel containing nickel, chromium and manganese uses laterite nickel ore as a raw material, and comprises the following process steps performed in sequence: Laterite nickel ore sintering → primary smelting furnace → low nickel chromium manganese iron water + steelmaking pig iron → AOD refining furnace smelting slag and oxygen blowing dephosphorization → ladle refining furnace refining treatment → double-strand slab continuous casting → hot rolling; Among them, the slag making and oxygen blowing dephosphorization of the AOD refining furnace include two steps: S1: in the early stage of smelting, the production raw materials are deoxidized, decarbonized and desiliconized to a certain stage, quicklime is added to make slag, and slag is removed and poured; S2: strong oxygen supply, quicklime is added after the slag is poured in S1 for secondary slag making, and then the slag is removed; The secondary slag making comprises the following steps: firstly using the side gun as the main blower → after the lime to be added is melted, using the top gun for double blowing for blowing, and then controlling the slag basicity through the oxidation period, wherein the dephosphorization is mainly carried out by increasing the oxidizability in the early and middle stages of oxidation, and the dephosphorization is carried out according to the carbon content in the final stage of oxidation; AOD refining furnace smelting includes: steelmaking period, during which the weight of ordinary pig iron added at a time is ≤8 tons, which is added in 6 times. After adding ferrosilicon and silicon carbon balls and heating up the materials, 8-8.5 tons of lime are added for slagging, and the amount of ferrosilicon + silicon carbon balls added is 3.2-3.5 tons; slag is poured after slagging, and the basicity is controlled at 1.2-1.

6. The temperature of the molten steel at the end of the steelmaking period is: 1700℃≤ΔTc+T≤1750℃, where ΔTc is the temperature difference of the molten steel corresponding to different carbon contents, and T is the initial temperature of the steelmaking period.

2. The method for manufacturing a nickel-chromium-manganese-containing carbon structural steel according to claim 1, characterized in that: The slag basicity is controlled at 3.5-4.

5.

3. The method for manufacturing a nickel-chromium-manganese-containing carbon structural steel according to claim 1, characterized in that: When the carbon content is ≤0.10%, the temperature of the furnace is measured and samples are taken, and fluorite is added to adjust the final slag according to the fluidity of the slag; when the carbon content is ≤0.04%, the oxygen supply is stopped, a small amount of ferrosilicon is added to shallowly reduce the chromium-containing slag, the temperature of the furnace is measured and samples are taken, and the slag removal operation is carried out after the phosphorus content meets the requirements.

4. The method for manufacturing a nickel-chromium-manganese-containing carbon structural steel according to claim 1, characterized in that: The working parameters of the top gun are: working pressure is 6-8 kg, and the gun position is controlled at 1700-2000mm.

5. The method for manufacturing a nickel-chromium-manganese-containing carbon structural steel according to claim 1, characterized in that: After the slag is discharged in S1, the amount of quicklime added is 6%-10% of the total loading amount.

6. The method for manufacturing a carbon structural steel containing nickel, chromium and manganese according to claim 3, characterized in that: The amount of fluorite added is ≤ 2% of the total loading amount.

7. The method for manufacturing a nickel-chromium-manganese-containing carbon structural steel according to claim 1, characterized in that: AOD refining furnace smelting includes: steelmaking period, during which the weight of ordinary pig iron added at a time is ≤8 tons, which is added in 6 times. After adding ferrosilicon and silicon carbon balls and heating up the materials, 8-8.5 tons of lime are added for slagging, and the amount of ferrosilicon + silicon carbon balls added is 3.2-3.5 tons; slag is poured after slagging, and the basicity is controlled at 1.2-1.

6. The temperature of the molten steel at the end of the steelmaking period is: 1700℃≤ΔTc+T≤1750℃, where ΔTc is the temperature difference of the molten steel corresponding to different carbon contents, and T is the initial temperature of the steelmaking period.

8. The method for manufacturing a nickel-chromium-manganese-containing carbon structural steel according to claim 1, characterized in that: AOD refining furnace smelting also includes: steel tapping, wherein: the composition and temperature of the molten steel reach the control target, the steel tapping temperature is 1580-1610°C, and 0.5kg / t ferrosilicon powder or 0.15kg / t high aluminum iron is added with the steel flow for deoxidation during the steel tapping process.

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