A smelting method for high nitrogen stainless steel

Abstract

The invention discloses a smelting method of high-nitrogen stainless steel, belongs to the technical field of high-nitrogen stainless steel, and solves the problem that the nitrogen pressure value set during the smelting of high-nitrogen stainless steel in the prior art does not match the nitrogen pressure value actually required at different stages of the alloy component smelting process. The target composition of high nitrogen stainless steel is consistent with the nitrogen filling pressure required to be controlled at the melting temperature: P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T; where P(N2) is the predicted nitrogen pressure during melting; w(C), w(Si), w(Mn), w(Cr), w(N) are the mass percentages of C, Si, Mn, Cr and N elements respectively; T is the melting temperature; the value range of A is ‑11~‑6, the value range of k1 is 0.16~1.8, the value range of k2 is 0.6~0.9, the value range of k3 is 0.18~0.25, the value range of k4 is 0.4~0.6, the value range of k5 is 8~13, and the value range of k6 is 0.009~0.012. The method of the invention can realize the whole process precise control of nitrogen pressure in the smelting process.

Description

Technical Field

[0001] The invention relates to the technical field of high-nitrogen stainless steel, and in particular to a smelting method of high-nitrogen stainless steel. Background Art

[0002] High nitrogen stainless steel stabilizes austenite by increasing the nitrogen content instead of expensive nickel, and has the advantages of environmental protection, energy saving, and low cost. Precise control of the nitrogen content of high nitrogen stainless steel is a key control factor in production. With the advancement of pressure smelting technology and analytical detection technology, the nitrogen content of high nitrogen steel grades has been effectively improved, and the role of nitrogen in steel has become clearer. Domestic and foreign scholars have carried out a large number of basic research on the preparation process and performance of high nitrogen steel through metallurgical thermodynamic calculations, simulation software, hot experiments and testing. However, how to effectively guide enterprises to efficiently and accurately control the nitrogen content when smelting high nitrogen steel is still a problem that needs to be solved. At present, when enterprises use vacuum induction pressure to smelt high-nitrogen stainless steel, they generally add pure iron (rods, plates, blocks, etc.) to melt first, and then add alloy materials for alloying. In this process, the nitrogen pressure required for dissolving nitrogen in the molten pool varies with the different contents of various metal elements in the molten pool and the different temperatures of induction heating. However, when enterprises are producing and smelting, they often use too high a pressure based on the smelting experience due to the need for stable control of high nitrogen content according to the nitrogen content requirements of the steel grade. The nitrogen charging pressure value usually set does not match the nitrogen pressure value actually required at different stages of the alloy component smelting process (the set value is greater than the required value), resulting in the disadvantages of long charging process time, nitrogen waste, and long exhaust time. Summary of the invention

[0003] In view of the above situation, the present invention aims to provide a smelting method of high-nitrogen stainless steel, which is used to solve the problem that the nitrogen pressure value set during the existing high-nitrogen stainless steel smelting does not match the nitrogen pressure value actually required at different stages of the alloy component smelting process (the set value is greater than the required value), resulting in a long inflation process, nitrogen waste, and a long exhaust time.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] The present invention provides a smelting method for high-nitrogen stainless steel. In the smelting method, the nitrogen filling pressure after breaking the vacuum is controlled according to the target composition and smelting temperature of the high-nitrogen stainless steel.

[0006] The target composition of high nitrogen stainless steel and the nitrogen filling pressure required to be controlled at the melting temperature conform to the following relationship:

[0007] P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T;

[0008] Wherein, P(N2) is the predicted nitrogen pressure during smelting, in atm; w(C), w(Si), w(Mn), w(Cr), and w(N) are the mass percentages of C, Si, Mn, Cr, and N elements, respectively, in wt%; T is the smelting temperature, in °C; the value range of A is -11 to -6, the value range of k1 is 0.16 to 1.8, the value range of k2 is 0.6 to 0.9, the value range of k3 is 0.18 to 0.25, the value range of k4 is 0.4 to 0.6, the value range of k5 is 8 to 13, and the value range of k6 is 0.009 to 0.012.

[0009] Furthermore, the value range of T is 1400-1650°C.

[0010] Furthermore,

[0011] When 1450℃<T≤1500℃, the nitrogen filling pressure meets the formula 1: P(N2)=-10.9083+0.8639w(C)+0.7270w(Si)-0.1989w(Mn)-0.4357w(Cr)+12.3417w(N)+0.009738T;

[0012] When 1500℃<T≤1550℃, the nitrogen filling pressure meets Formula 2: P(N2)=-8.3464+1.7301w(C)+0.7002w(Si)-0.2015w(Mn)-0.4762w(Cr)+8.1506w(N)+0.010841T;

[0013] When 1550℃<T≤1600℃, the nitrogen filling pressure meets Formula 3: P(N2)=-6.9387+0.9606w(C)+0.6885w(Si)-0.2177w(Mn)-0.4922w(Cr)+9.0772w(N)+0.009901T;

[0014] When 1600℃<T≤1650℃, the nitrogen filling pressure conforms to Formula 4: P(N2)=-8.2448+0.1635w(C)+0.8469w(Si)-0.2314w(Mn)-0.5475w(Cr)+10.3213w(N)+0.010843T.

[0015] Furthermore, the components of the high nitrogen stainless steel include, by mass percentage, C≤0.12%, Si≤0.80%, Mn: 17.5%-20.0%, Cr: 17.5%-20.0%, N≥0.47%, and the remainder is Fe and unavoidable impurities.

[0016] Further, the smelting method comprises:

[0017] Step 1: Purge the furnace of the pressurized induction furnace clean and set aside;

[0018] Step 2: weigh and batch the raw materials according to the target requirements of smelting composition;

[0019] Step 3: Place the weighed carbon powder and pure iron into the crucible of the pressurized induction furnace;

[0020] Step 4: Close the furnace of the pressurized induction furnace and start to evacuate. When the vacuum degree is lower than 10Pa, power on to start induction heating, maintain the vacuum, and remove the oxygen and hydrogen brought in by the raw materials. Then increase the power supply to accelerate the melting of the charge.

[0021] Step 5: Break the vacuum and fill with nitrogen according to the nitrogen filling pressure formula of P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T;

[0022] Step 6: After the charge is completely melted, reduce the power, add ferrosilicon, metallic chromium and metallic manganese in batches, add nitrogen-containing alloy after the nitrogen filling pressure reaches P (N2), increase the power after the alloy is melted, and add deoxidizer for deoxidation;

[0023] Step 7: Measure temperature, take samples, and after the components are tested to be qualified, reduce the power and adjust the temperature or shut down the power to cool down and prepare for casting;

[0024] Step 8: Before casting, increase the nitrogen filling pressure and maintain it for 1min to 0.3*M min, and then cast;

[0025] Step 9: After the casting is completed (0.1-0.5)*M / n min, the ingot is removed and cooled for storage; wherein n is the number of ingots cast per smelting furnace;

[0026] M is the total mass of the raw materials.

[0027] Furthermore, in step 4, when the induction heating is started by power-on, the power of the induction heating is Q=(0.5-1.5)*M, in kW.

[0028] Furthermore, in step 4, the vacuum is maintained for 0.1 h to 0.5*M h.

[0029] Furthermore, in step 4, the power supply is increased to Q=(1.5-4)*M to accelerate the melting of the charge.

[0030] Furthermore, in step 8, the nitrogen filling pressure is increased to P(N2)+0.1~1atm and maintained for 1min~0.3*M min.

[0031] Furthermore, in step 9, when the calculated result of (0.1-0.5)*M / n is less than 5, the reaction is performed after 5 minutes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The smelting method of high nitrogen stainless steel of the present invention can realize the precise control of the nitrogen pressure in the whole smelting process by designing the process correlation between the nitrogen filling pressure and the target composition and the smelting temperature, avoid blindly controlling the excessive nitrogen filling pressure, save metal materials and gas source medium, and the nitrogen content of the product can be stabilized within ±5% of the target value.

[0034] 2) The high nitrogen stainless steel smelting method of the present invention ensures the smelting temperature requirements of different raw materials by accurately controlling the heating power at different stages, while being able to save energy, improve production efficiency and reduce production costs.

[0035] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents particularly pointed out in the written description and claims. DETAILED DESCRIPTION

[0036] The present invention provides a smelting method for high nitrogen stainless steel. In the smelting method, the target composition of the high nitrogen stainless steel and the nitrogen filling pressure required to be controlled at the smelting temperature meet the following relationship:

[0037] P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T;

[0038] Wherein, P(N2) is the predicted nitrogen pressure during smelting, in atm; w(C), w(Si), w(Mn), w(Cr), w(N) are the mass percentages of C, Si, Mn, Cr and N elements, respectively, in wt%; T is the smelting temperature, in °C; the value range of A is -11 to -6, the value range of k1 is 0.16 to 1.8, the value range of k2 is 0.6 to 0.9, the value range of k3 is 0.18 to 0.25, the value range of k4 is 0.4 to 0.6, the value range of k5 is 8 to 13, and the value range of k6 is 0.009 to 0.012.

[0039] Specifically, the value range of T is 1400-1650°C.

[0040] Specifically, when 1450°C<T≤1500°C, the nitrogen filling pressure conforms to Formula 1: P(N2)=-10.9083+0.8639w(C)+0.7270w(Si)-0.1989w(Mn)-0.4357w(Cr)+12.3417w(N)+0.009738T.

[0041] Specifically, when 1500°C<T≤1550°C, the nitrogen filling pressure conforms to Formula 2: P(N2)=-8.3464+1.7301w(C)+0.7002w(Si)-0.2015w(Mn)-0.4762w(Cr)+8.1506w(N)+0.010841T.

[0042] Specifically, when 1550°C<T≤1600°C, the nitrogen filling pressure conforms to Formula 3: P(N2)=-6.9387+0.9606w(C)+0.6885w(Si)-0.2177w(Mn)-0.4922w(Cr)+9.0772w(N)+0.009901T.

[0043] Specifically, when 1600°C<T≤1650°C, the nitrogen filling pressure conforms to Formula 4: P(N2)=-8.2448+0.1635w(C)+0.8469w(Si)-0.2314w(Mn)-0.5475w(Cr)+10.3213w(N)+0.010843T.

[0044] Specifically, the components of the high nitrogen stainless steel include, by mass percentage, C≤0.12%, Si≤0.80%, Mn: 17.5%-20.0%, Cr: 17.5%-20.0%, N≥0.47%, and the remainder is Fe and unavoidable impurities.

[0045] Preferably, the components of the high nitrogen stainless steel include, by mass percentage, C: 0.05% to 0.12%, Si: 0.2% to 0.8%, Mn: 17.5% to 20.0%, Cr: 17.5% to 20.0%, N: 0.6% to 1.2%, and the remainder is Fe and unavoidable impurities.

[0046] Specifically, the smelting method of the high nitrogen stainless steel comprises:

[0047] Step 1: Use compressed air to clean the furnace of the pressurized induction furnace and set it aside;

[0048] Step 2: weigh and batch the raw materials according to the target requirements of smelting composition;

[0049] Step 3: Place the weighed carbon powder and pure iron into the crucible of the pressurized induction furnace;

[0050] Step 4: Close the furnace of the pressurized induction furnace and start to evacuate. When the vacuum degree is lower than 10Pa, power on to start induction heating. Maintain the vacuum to remove oxygen and hydrogen brought in by the raw materials. Increase the power supply to accelerate the melting of the charge.

[0051] Step 5: Break the vacuum and fill with nitrogen according to the nitrogen filling pressure formula of P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T;

[0052] Step 6: After the charge is completely melted, reduce the power, add ferrosilicon, metallic chromium and metallic manganese in batches, add nitrogen-containing alloy after the nitrogen filling pressure reaches P (N2), increase the power after the alloy is melted, and add deoxidizer for deoxidation;

[0053] Step 7: Measure temperature, take samples, and after the components are tested to be qualified, reduce the power and adjust the temperature or shut down the power to cool down and prepare for casting;

[0054] Step 8: Before casting, increase the nitrogen filling pressure to P(N2)+0.1~1atm and maintain it for 1min~0.3*Mmin, and then cast;

[0055] Step 9: After the casting is completed (0.1~0.5)*M / n min, the ingot is broken, and the ingot is removed for cooling and storage; n is the number of ingots cast in each smelting furnace. When the calculated result of (0.1~0.5)*M / n is less than 5, the ingot is broken after 5 min.

[0056] Specifically, in the above step 2, the raw materials include carbon powder, ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride, a deoxidizer and pure iron.

[0057] Specifically, in the above step 2, the total mass of the raw materials is M, in kg; when weighing the ingredients, the mass percentage of each element in each raw material component is controlled according to the law of conservation of mass. (x) =m x / M should be within the material composition requirements, where m x is the weight of element x in kg, where x is C, Si, Mn, Cr, N, P, or S.

[0058] Specifically, in the above step 3, the weighed carbon powder and pure iron are placed into the crucible of the pressurized induction furnace in a top-loose and bottom-tight mode.

[0059] Specifically, in the above step 3, the charge can be added and melted all at once or in batches.

[0060] Specifically, in the above step 4, when the induction heating is started by power-on, the power of the induction heating is Q=(0.5-1.5)*M, in kW.

[0061] Specifically, in the above step 4, the vacuum is maintained for 0.1 h to 0.5*M h to remove oxygen and hydrogen brought into the raw materials.

[0062] Specifically, the above-mentioned pressurized induction furnace has a continuous temperature measurement function, or a temperature measuring head can be used to measure the temperature.

[0063] Specifically, in the above step 4, the power supply is increased to Q=(1.5-4)*M to accelerate the melting of the charge.

[0064] Specifically, the material processing situation in the furnace can be observed through the peephole on the top of the pressurized induction furnace.

[0065] Specifically, in the above step 5, the smelting temperature T is controlled to be 1400-1650°C.

[0066] Specifically, in the above step 6, the power Q=(1-2)*M is reduced, and low-carbon ferrosilicon, metallic chromium and metallic manganese are added in batches.

[0067] Specifically, in the above step 6, the nitrogen-containing alloy includes ferrochromium nitride and / or manganese nitride.

[0068] Specifically, in the above step 6, the power is increased to Q=(1.5-2.5)*M and a deoxidizer is added for deoxidation.

[0069] Specifically, in the above step 6, during the actual production process, P(N2) may have a deviation within +0.15 atm.

[0070] Specifically, in the above step 7, if the element content in the sample analysis is not within the specified range, additional alloy is added and the sample is tested again until the composition is qualified.

[0071] Compared with the prior art, the smelting method of high nitrogen stainless steel of the present invention can realize the precise control of nitrogen pressure in the whole smelting process by designing the process correlation relationship between nitrogen filling pressure, target composition and smelting temperature, avoid blindly controlling excessive nitrogen filling pressure, save metal materials and gas source medium, and the nitrogen content of the product can be stabilized within ±5% of the target value.

[0072] The high-nitrogen stainless steel smelting method of the present invention ensures the smelting temperature requirements of different raw materials by accurately controlling the heating power at different stages, and can save energy, improve production efficiency and reduce production costs.

[0073] Example 1

[0074] This embodiment provides a smelting method for high nitrogen stainless steel. The target composition and smelting temperature of the high nitrogen stainless steel in this embodiment are shown in Table 1 below. The specific implementation steps and process control parameters are as follows:

[0075] Step 1: Use compressed air to clean the furnace of the pressurized induction furnace and set it aside;

[0076] Step 2: Weigh and mix the raw materials such as carbon powder, ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride, deoxidizer, pure iron, etc. according to the target requirements of smelting composition, with a total mass of about 38kg;

[0077] Step 3: Put the weighed carbon powder, pure iron and other raw materials into the crucible of the pressurized induction furnace in a loose upper and tight lower mode; the charge can be added and melted in batches;

[0078] Step 4: Close the hearth of the pressurized induction furnace, start to evacuate, and when the vacuum degree is lower than 10Pa, start the induction heating with power of about 50kW, and maintain the vacuum for 0.5h to remove oxygen and hydrogen brought in by the raw materials; the power supply is increased to about 70kW to accelerate the melting of the charge;

[0079] Step 5: Break the vacuum, control the melting temperature between 1540 and 1550°C, observe the material situation in the furnace through the peephole on the top of the pressurized induction furnace, control the nitrogen filling pressure in different temperature ranges according to Formula 2, and calculate that P(N2) is 2.14atm when the melting temperature is 1550°C (the actual control value is about 2.2atm);

[0080] Step 6: After the charge is completely melted, reduce the power to about 50kW, add low-carbon ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride and other alloys in batches, and when the alloy is melted, increase the power to about 60kW and add deoxidizer for deoxidation;

[0081] Step 7: After finishing steps 5 and 6, measure temperature, take samples, and after the components are tested to be qualified, turn off the power to cool down and prepare for casting;

[0082] Step 8: Before casting, increase the nitrogen filling pressure to 2.3 atm and maintain it for 2 minutes before casting;

[0083] Step 9: 7 minutes after casting, remove the steel ingot and cool it for storage.

[0084] Example 2

[0085] This embodiment provides a smelting method for high nitrogen stainless steel. The target composition and smelting temperature of the high nitrogen stainless steel in this embodiment are shown in Table 1 below. The specific implementation steps and process control parameters are as follows:

[0086] Step 1: Use compressed air to clean the furnace of the pressurized induction furnace and set it aside;

[0087] Step 2: Weigh and mix the raw materials such as carbon powder, ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride, deoxidizer, pure iron, etc. according to the target requirements of smelting composition, with a total mass of about 38kg;

[0088] Step 3: Put the weighed carbon powder, pure iron and other raw materials into the crucible of the pressurized induction furnace in a loose upper and tight lower mode; the charge can be added and melted in batches;

[0089] Step 4: Close the hearth of the pressurized induction furnace, start to evacuate, and when the vacuum degree is lower than 10Pa, start the induction heating with power of about 50kW, and maintain the vacuum for 0.5h to remove oxygen and hydrogen brought in by the raw materials; the power supply is increased to about 70kW to accelerate the melting of the charge;

[0090] Step 5: Break the vacuum, control the melting temperature between 1530 and 1550°C, observe the material situation in the furnace through the peephole on the top of the pressurized induction furnace, control the nitrogen filling pressure in different temperature ranges according to Formula 2, and calculate that the P(N2) when the melting temperature is 1550°C is 2.8atm (the actual control value is about 2.8atm);

[0091] Step 6: After the charge is completely melted, reduce the power to about 50kW, add low-carbon ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride and other alloys in batches, and when the alloy is melted, increase the power to about 60kW and add deoxidizer for deoxidation;

[0092] Step 7: After finishing steps 5 and 6, measure temperature, take samples, and after the components are tested to be qualified, turn off the power to cool down and prepare for casting;

[0093] Step 8: Before casting, increase the nitrogen filling pressure to 3.1 atm and maintain it for 2 minutes before casting;

[0094] Step 9: 7 minutes after casting, remove the steel ingot and cool it for storage.

[0095] Example 3

[0096] This embodiment provides a smelting method for high nitrogen stainless steel. The target composition and smelting temperature of the high nitrogen stainless steel in this embodiment are shown in Table 1 below. The specific implementation steps and process control parameters are as follows:

[0097] Step 1: Use compressed air to clean the furnace of the pressurized induction furnace and set it aside;

[0098] Step 2: Weigh and mix the raw materials such as carbon powder, ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride, deoxidizer, pure iron, etc. according to the target requirements of smelting composition, with a total mass of about 38kg;

[0099] Step 3: Put the weighed carbon powder, pure iron and other raw materials into the crucible of the pressurized induction furnace in a loose upper and tight lower mode; the charge can be added and melted in batches;

[0100] Step 4: Close the hearth of the pressurized induction furnace, start to evacuate, and when the vacuum degree is lower than 10Pa, start the induction heating with power of about 50kW, and maintain the vacuum for 0.5h to remove oxygen and hydrogen brought in by the raw materials; the power supply is increased to about 70kW to accelerate the melting of the charge;

[0101] Step 5: Break the vacuum, control the melting temperature between 1560 and 1570°C, observe the chemical conditions in the furnace through the peephole on the top of the pressurized induction furnace, control the nitrogen filling pressure in different temperature ranges according to Formula 3, and calculate that P(N2) is 4.1atm when the melting temperature is 1560°C (the actual control value is about 4.1atm);

[0102] Step 6: After the charge is completely melted, reduce the power to about 50kW, add low-carbon ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride and other alloys in batches, and when the alloy is melted, increase the power to about 60kW and add deoxidizer for deoxidation;

[0103] Step 7: After finishing steps 5 and 6, measure temperature, take samples, and after the components are tested to be qualified, turn off the power to cool down and prepare for casting;

[0104] Step 8: Before casting, increase the nitrogen filling pressure to 4.2 atm and maintain it for 2 minutes before casting;

[0105] Step 9: 7 minutes after casting, remove the steel ingot and cool it for storage.

[0106] The control values ​​and measured values ​​of the design composition, smelting temperature, smelting nitrogen pressure and other parameters of the high nitrogen stainless steel of Examples 1-3 are shown in Table 1 below. It can be seen that the high nitrogen stainless steel smelting method of the present invention is used to control the nitrogen filling pressure, which can achieve accurate control of the nitrogen pressure in the entire smelting process. The nitrogen filling pressure does not need to be too high to ensure that the nitrogen content of the product can be stabilized within ±5% of the target value.

[0107] Table 1 Composition / main parameter setting values ​​and actual values ​​of Examples 1-3

[0108]

[0109] Comparative Example 1

[0110] This comparative example uses original experience to smelt high nitrogen stainless steel, and the chemical composition of the comparative steel is the same as that of Example 3. The smelting method includes:

[0111] Step 1: Use compressed air to clean the furnace of the pressurized induction furnace and set it aside;

[0112] Step 2: Weigh and mix the raw materials such as carbon powder, ferrosilicon, metallic chromium, metallic manganese, ferrochrome nitride, manganese nitride, deoxidizer, pure iron, etc. according to the target requirements of smelting composition, with a total mass of about 38kg;

[0113] Step 3: Put the weighed carbon powder, pure iron and other raw materials into the crucible of the pressurized induction furnace in a loose upper and tight lower mode; the charge can be added and melted in batches;

[0114] Step 4: Close the furnace of the pressurized induction furnace, start to evacuate, and when the vacuum degree is lower than 10Pa, turn on the power to start induction heating, the power is about 50kW, and the vacuum is maintained for 0.5 hours to remove the oxygen and hydrogen brought in by the raw materials;

[0115] Step 5: Break the vacuum, control the target temperature between 1550 and 1600°C, observe the material chemical situation in the furnace through the peephole on the top of the pressurized induction furnace, control the nitrogen pressure to 4.5atm based on experience, and increase the nitrogen pressure to 4.8atm during casting.

[0116] The composition / main parameter setting values ​​and actual values ​​of the steel in this comparative example are shown in Table 2 below.

[0117] Table 2 Main components / main parameter setting values ​​and actual values ​​of comparative example 1

[0118]

[0119] By comparing Table 1 and Table 2, it can be seen that the method of the present invention can more accurately control the nitrogen pressure values ​​required for different components and different temperatures, save energy and materials, reduce production consumption costs, and save nitrogen filling time.

[0120] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for smelting high nitrogen stainless steel, characterized in that: In the smelting method, the nitrogen filling pressure after breaking the vacuum is controlled according to the target composition of the high nitrogen stainless steel and the smelting temperature; The target composition of high nitrogen stainless steel and the nitrogen filling pressure required to be controlled at the melting temperature conform to the following relationship: P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T; Wherein, P(N2) is the predicted nitrogen pressure during smelting, in atm; w(C), w(Si), w(Mn), w(Cr), and w(N) are the mass percentages of C, Si, Mn, Cr, and N elements, respectively, in wt%; T is the smelting temperature, in °C; the value range of A is -11 to -6, the value range of k1 is 0.16 to 1.8, the value range of k2 is 0.6 to 0.9, the value range of k3 is 0.18 to 0.25, the value range of k4 is 0.4 to 0.6, the value range of k5 is 8 to 13, and the value range of k6 is 0.009 to 0.

012.

2. The smelting method according to claim 1, characterized in that: The value range of T is 1400~1650℃.

3. The smelting method according to claim 1, characterized in that: When 1450℃<T≤1500℃, the nitrogen filling pressure meets the formula 1: P(N2)=-10.9083+0.8639w(C)+0.7270w(Si)-0.1989w(Mn)-0.4357w(Cr)+12.3417w(N)+0.009738T; When 1500℃<T≤1550℃, the nitrogen filling pressure meets Formula 2: P(N2)=-8.3464+1.7301w(C)+0.7002w(Si)-0.2015w(Mn)-0.4762w(Cr)+8.1506w(N)+0.010841T; When 1550℃<T≤1600℃, the nitrogen filling pressure meets Formula 3: P(N2)=-6.9387+0.9606w(C)+0.6885w(Si)-0.2177w(Mn)-0.4922w(Cr)+9.0772w(N)+0.009901T; When 1600℃<T≤1650℃, the nitrogen filling pressure conforms to Formula 4: P(N2)=-8.2448+0.1635w(C)+0.8469w(Si)-0.2314w(Mn)-0.5475w(Cr)+10.3213w(N)+0.010843T.

4. The smelting method according to claim 1, characterized in that: The components of the high nitrogen stainless steel include, by mass percentage, C≤0.12%, Si≤0.80%, Mn: 17.5%-20.0%, Cr: 17.5%-20.0%, N≥0.47%, and the remainder is Fe and unavoidable impurities.

5. The smelting method according to claim 2, characterized in that: The smelting method comprises: Step 1: Purge the furnace of the pressurized induction furnace clean and set aside; Step 2: weigh and batch the raw materials according to the target requirements of smelting composition; Step 3: Place the weighed carbon powder and pure iron into the crucible of the pressurized induction furnace; Step 4: Close the furnace of the pressurized induction furnace and start to evacuate. When the vacuum degree is lower than 10Pa, power on to start induction heating, maintain the vacuum, and remove the oxygen and hydrogen brought in by the raw materials. Then increase the power supply to accelerate the melting of the charge. Step 5: Break the vacuum and fill with nitrogen according to the nitrogen filling pressure formula of P(N2)=A+k1w(C)+k2w(Si)-k3w(Mn)-k4w(Cr)+k5w(N)+k6T; Step 6: After the charge is completely melted, reduce the power, add ferrosilicon, metallic chromium and metallic manganese in batches, add nitrogen-containing alloy after the nitrogen filling pressure reaches P (N2), increase the power after the alloy is melted, and add deoxidizer for deoxidation; Step 7: Measure temperature, take samples, and after the components are tested to be qualified, reduce the power and adjust the temperature or shut down the power to cool down and prepare for casting; Step 8: Before casting, increase the nitrogen filling pressure and maintain it for 1min to 0.3*M min, and then cast; Step 9: After the casting is completed (0.1-0.5)*M / n min, the ingot is removed and cooled for storage; wherein n is the number of ingots cast per smelting furnace; The M is the total mass of the raw materials.

6. The smelting method according to claim 5, characterized in that: In step 4, when the induction heating is started by power-on, the power of the induction heating is Q=(0.5-1.5)*M, in kW.

7. The smelting method according to claim 5, characterized in that: In the step 4, the vacuum is maintained for 0.1 h to 0.5*Mh.

8. The smelting method according to claim 5, characterized in that: In step 4, the power supply is increased to Q=(1.5-4)*M to accelerate the melting of the charge.

9. The smelting method according to claim 5, characterized in that: In step 8, the nitrogen filling pressure is increased to P(N2)+0.1-1 atm and maintained for 1 min-0.3*M min.

10. The smelting method according to any one of claims 5 to 9, characterized in that: In step 9, when the calculated result of (0.1-0.5)*M / n is less than 5, the mixture is broken after 5 minutes.

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