Process for smelting precipitation hardening steel for smelting austenitic stainless steel

Abstract

The invention discloses a process for smelting precipitation hardening steel for smelting austenitic stainless steel. The process comprises the following steps: molten iron pretreatment: carrying out double-slag pretreatment on molten iron by adopting a medium-frequency induction furnace; aOD refining: adding the pretreated molten iron into an AOD furnace, and decarburizing by adopting a three-section dynamic gas ratio; lF secondary refining, wherein the AOD molten steel is subjected to slag pulling and then transferred into an LF furnace; vD vacuum treatment is conducted, specifically, a stepped vacuum system is adopted, the vacuum degree of the forevacuum stage is 10-100 torr, the vacuum degree of the deep vacuum stage is 0.1-0.3 torr, and pulse type bottom argon blowing stirring is matched; titanium alloying: adding a titanium-aluminum alloy wire through a wire feeding method after VD treatment, and dynamically adjusting the wire feeding speed by using an online component analysis system; and soft argon blowing purification: adopting a bubble atomization and electromagnetic stirring composite technology, and controlling the soft blowing time to be 15-30 minutes. The method has the beneficial effects that according to the technical scheme, the titanium recovery rate is increased to 85% or above from 60%-70% through wire feeding after vacuum and online control, and the alloy consumption cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of steel production technology, and in particular to a process for smelting precipitation-hardening steel for smelting austenitic stainless steel. Background Technology Summary of the Invention

[0002] The main technical problem solved by this invention is to provide a process for smelting precipitation hardening steel for smelting austenitic stainless steel, thereby solving one or more of the above-mentioned prior art problems.

[0003] To solve the above-mentioned technical problems, the present invention adopts a technical solution as follows: a process for smelting precipitation-hardening steel for smelting austenitic stainless steel, the innovation of which lies in including the following steps:

[0004] (1) Hot metal pretreatment: Hot metal is pretreated by double slag method in medium frequency induction furnace to control the hot metal composition to meet the following requirements: P≤0.025%, S≤0.015%, Cr 15.50%~17.50%, Ni 3.5%~5.0%, Cu 3.0%~5.0%, Nb 0.15%~0.45%, temperature ≥1580℃, and CaO-MgO-Al2O3 composite powder is sprayed for deep dephosphorization and desulfurization.

[0005] (2) AOD refining: The pretreated molten iron is added to the AOD furnace and decarburized using a "three-stage dynamic gas ratio". 90-100 kg of lime, 8 kg of ferrosilicon and CaO-C composite powder are added per ton of molten iron to control the final carbon content to 0.020%-0.025%.

[0006] (3) LF secondary refining: After slag removal, the AOD molten steel is transferred to the LF furnace, and aluminum-calcium alloy, silicon-calcium-barium composite deoxidizer and rare earth elements are added in sequence through the gradient deoxidation process, and the refining time is controlled at 60-70 minutes.

[0007] (4) VD vacuum treatment: A stepped vacuum system is adopted, with a vacuum degree of 10 to 100 Torr in the pre-vacuum stage and 0.1 to 0.3 Torr in the deep vacuum stage, combined with pulse bottom blowing argon stirring;

[0008] (5) Titanium alloying: After VD treatment, titanium-aluminum alloy wire is added by wire feeding method. The wire feeding speed is dynamically adjusted by online composition analysis system to ensure that the titanium recovery rate is ≥85%.

[0009] (6) Soft blowing argon purification: The combined technology of bubble atomization and electromagnetic stirring is adopted to control the soft blowing time to 15-30 minutes, so that the oxygen content in the molten steel is ≤15PPM and the nitrogen content is ≤100PPM.

[0010] In some embodiments, the dual-slag pretreatment in step (1) includes: first, making an oxidizing slag to remove 80% of phosphorus, and then making a reducing slag for desulfurization. The particle size of the CaO-MgO-Al2O3 composite powder injected is 50-100μm, and the dosage is 8-12kg / t.

[0011] In some implementations, the three-stage dynamic gas ratio in step (2) is specifically as follows:

[0012] Initial setup: Oxygen-argon ratio 6:1, oxygen flow rate 1000 m³ / h 3 / H;

[0013] Interim: Oxygen-argon ratio 3:1, oxygen flow rate 600M 3 / H;

[0014] Final stage: Pure argon blowing, flow rate 400 MJ / L 3 / H;

[0015] The CaO-C composite powder has a CaO to C mass ratio of 5:1, a particle size of <30μm, and a dosage of 3-5kg / t.

[0016] In some embodiments, the gradient deoxygenation process in step (3) includes:

[0017] Initially, 2 kg / t of aluminum-calcium alloy is added to reduce the oxygen content to below 30 PPM;

[0018] Add 4 kg / t of silicon-calcium-barium composite deoxidizer (Si:Ca:Ba = 60:20:20) during the intermediate stage;

[0019] At the end of the process, 0.05-0.1 kg / t of Ce-La mixed rare earth elements were added to control the inclusion size to ≤5 μm.

[0020] In some implementations, the stepped vacuum regime described in step (4) specifically refers to:

[0021] Pre-vacuum stage: The vacuum level is reduced from 100 Torr to 10 Torr, and the bottom blowing argon pressure is 4-6 MPa;

[0022] Deep vacuum stage: The vacuum level is increased to 0.1-0.3 Torr, and pulsed argon gas stirring with a frequency of 1-2 Hz and a pressure fluctuation of 2-4 MPa is applied. The temperature of the molten steel is maintained at 1600-1620℃.

[0023] In some embodiments, the Ti:Al mass ratio of the titanium-aluminum alloy wire in step (5) is 7:3, the diameter is 12 mm, the surface is covered with a CaO-MgO protective layer, and the wire feeding speed is 1-3 m / s; the online composition analysis system uses laser-induced breakdown spectroscopy to control the titanium content in real time with an accuracy of ±0.005%.

[0024] In some embodiments, the bubble atomization and electromagnetic stirring composite technology in step (6) includes: bottom blowing argon with a porous permeable brick with a pore size of 0.5 to 1 mm, combined with an electromagnetic stirring device with a top frequency of 5 to 10 Hz and a magnetic field strength of 0.1 to 0.2 T, to control the bubble size to 1 to 3 mm and the total content of inclusions to ≤ 0.005%.

[0025] In some embodiments, the molten iron pretreatment in step (1) further includes spraying an As-Sn scavenger at a dosage of 3-5 kg / t, so that As ≤ 0.010% and Sn ≤ 0.005% in the molten steel.

[0026] The beneficial effects of this invention are:

[0027] Significantly improved purity: oxygen content ≤15PPM (reduced by 30%), nitrogen content ≤100PPM (reduced by 40%), and harmful elements As and Sn controlled below 0.01%, improving the toughness and corrosion resistance of steel;

[0028] Improved titanium recovery rate: Vacuum post-feeding and online control increase the titanium recovery rate from 60%-70% to over 85%, reducing alloy consumption costs;

[0029] Refined control of inclusions: Rare earth metamorphism and composite soft blowing make the inclusion size ≤5μm and spherical, avoiding the risk of cracking caused by stress concentration;

[0030] Enhanced process stability: Technologies such as dynamic gas ratio and stepped vacuum reduce composition fluctuations, increasing the product qualification rate from 85% to 98%.

[0031] High level of intelligence: LIBS online analysis and closed-loop control replace manual sampling, shortening the smelting cycle by 15% and reducing labor intensity. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0033] Figure 1 This is a flow chart of a process for smelting precipitation-hardening steel for smelting austenitic stainless steel according to the present invention. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] A process for smelting precipitation-hardening steel for smelting austenitic stainless steel, the specific steps of which are as follows:

[0037] 1. Hot metal pretreatment

[0038] The molten iron is poured into a medium-frequency induction furnace for double-slag pretreatment:

[0039] Oxidizing slag stage: Add 50 kg / t CaO and 15 kg / t SiO2 (CaO / SiO2 = 3.3), introduce oxygen and stir for 20 minutes to remove 80% of phosphorus (P decreases from 0.045% to 0.009%).

[0040] Reducing slag stage: Add 30 kg / t CaO, 10 kg / t Al2O3, and 5 kg / t MgO to form a CaO-Al2O3-MgO slag system. Inject 10 kg / t of CaO-MgO-Al2O3 composite powder (particle size 80 μm, CaO:MgO:Al2O3 = 6:2:2) and bottom blow argon stirring for 30 minutes, controlling S≤0.015%.

[0041] Harmful element control: Inject 4 kg / t of CaO-Fe2O3-based As-Sn scavenger to ensure As ≤ 0.008% and Sn ≤ 0.004%;

[0042] Pretreatment endpoint: molten iron composition (mass percentage): Cr 16.5%, Ni 4.2%, Cu 4.0%, Nb 0.30%, P 0.009%, S 0.012%, temperature 1590℃.

[0043] 2. AOD Refining

[0044] The pretreated molten iron is added to the AOD furnace, with 95 kg of lime, 8 kg of ferrosilicon, and 4 kg / t of CaO-C composite powder (CaO:C = 5:1, particle size 25 μm) added per ton of molten iron for three-stage decarburization:

[0045] Initial stage (carbon content 0.4%): oxygen-argon ratio 6:1, oxygen flow rate 1000 m³ / h 3 / H, lasting 30 minutes;

[0046] Intermediate stage (carbon content 0.2%): oxygen-argon ratio 3:1, oxygen flow rate 600M3 / H, lasting 25 minutes;

[0047] Final stage (carbon content 0.08%): pure argon blowing, flow rate 400M 3 / H, lasting 15 minutes;

[0048] Endpoint control: carbon content 0.022%, temperature 1690℃, sampling and testing O=35PPM, N=280PPM.

[0049] 3. LF Secondary Refining

[0050] After 80% slag removal, the molten steel is transferred to the LF furnace for gradient deoxidation.

[0051] Initial deoxidation: Add 2 kg / t of aluminum-calcium alloy, stir for 10 minutes, and the oxygen content drops to 28 PPM;

[0052] Intermediate deoxidation: Add 4 kg / t of silicon-calcium-barium composite deoxidizer (Si:Ca:Ba=60:20:20), and stir for 15 minutes after the slag turns white;

[0053] Rare earth treatment: Add 0.08 kg / t of Ce-La mixed rare earth (Ce:La = 7:3), stir continuously for 20 minutes, and control the size of inclusions to ≤4 μm;

[0054] Refining endpoint: temperature 1685℃, composition adjusted to Si = 0.25% and Mn = 0.35%.

[0055] 4. VD vacuum treatment

[0056] Molten steel is hoisted into the VD vacuum chamber, where a stepped vacuum regime is applied.

[0057] Pre-vacuum stage: The vacuum level is reduced from 100 Torr to 10 Torr within 5 minutes, the bottom blowing argon pressure is 5 MPa, and large particle inclusions are removed by stirring;

[0058] Deep vacuum stage: The vacuum level is increased to 0.2 Torr, and pulsed argon gas stirring is applied (frequency 1.5 Hz, pressure fluctuation 3 MPa) for 18 minutes;

[0059] Air puncture detection: H = 0.9 PPM, N = 120 PPM, temperature 1610℃.

[0060] 5. Titanium alloying

[0061] Titanium-aluminum alloy wire (Ti:Al = 7:3, diameter 12mm, surface coated with CaO-MgO protective layer) was fed into the molten steel using a wire feeder, and the titanium content was monitored in real time using a LIBS online analysis system.

[0062] Initial titanium content 0.01%, wire feeding speed 2m / s, wire feeding amount 3.8kg / t;

[0063] The final titanium content was 0.32%, and the recovery rate was 88%.

[0064] 6. Soft-blown argon purification

[0065] A porous, breathable brick (0.8mm pore size) is installed at the bottom of the ladle, and electromagnetic stirring (8Hz frequency, 0.15T magnetic field strength) is applied to the top.

[0066] The soft blowing argon flow rate was 8 L / min·t, lasting for 25 minutes, with a bubble size of 2 mm.

[0067] Final test results: Oxygen content 12 PPM, nitrogen content 90 PPM, total impurities 0.004%.

[0068] Example 2

[0069] A process for smelting precipitation-hardening steel for smelting austenitic stainless steel, the specific steps of which are as follows:

[0070] 1. Hot metal pretreatment

[0071] Oxidizing slag stage: Add 55 kg / t CaO and 14 kg / t SiO2 (CaO / SiO2 = 3.9), stir with oxygen for 18 minutes, and P decreases from 0.048% to 0.008%;

[0072] Reducing slag stage: Add 28 kg / t CaO, 12 kg / t Al2O3, and 6 kg / t MgO, and spray 12 kg / t of CaO-MgO-Al2O3 composite powder (particle size 50 μm, CaO:MgO:Al2O3 = 5:3:2), bottom blow argon stirring for 25 minutes, S ≤ 0.014%;

[0073] Harmful element control: Inject 5 kg / t of CaO-Fe2O3-based scavenger, As ≤ 0.007% and Sn ≤ 0.004%;

[0074] Pretreatment endpoint: Cr 17.0%, Ni 4.8%, Cu 4.5%, Nb 0.40%, P 0.008%, S 0.013%, temperature 1600℃.

[0075] 2. AOD Refining

[0076] Add 100 kg / t of lime, 8 kg / t of ferrosilicon, and 5 kg / t of CaO-C composite powder (particle size 20 μm, CaO:C = 4:1) for three-stage decarburization:

[0077] Initial stage (carbon 0.45%): oxygen-argon ratio 5:1, oxygen flow rate 950 m³ / h 3 / H, lasting 25 minutes;

[0078] Intermediate stage (0.15% carbon): Oxygen-argon ratio 2.5:1, oxygen flow rate 550M 3 / H, lasting 30 minutes;

[0079] Final stage (carbon 0.07%): Pure argon flow rate 450 MJ / L 3 / H, lasting 12 minutes;

[0080] Endpoint control: carbon 0.020%, temperature 1700℃, O = 32PPM, N = 270PPM.

[0081] 3. LF Secondary Refining

[0082] Initial deoxidation: 2.2 kg / t of aluminum-calcium alloy, stirred for 12 minutes, O decreased to 26 PPM;

[0083] Intermediate deoxidation: 4.5 kg / t of silicon-calcium-barium composite deoxidizer (Si:Ca:Ba = 55:25:20), stirred for 18 minutes;

[0084] Rare earth treatment: Ce-La mixed rare earth 0.1kg / t, stirred for 22 minutes, inclusion size ≤3.5μm;

[0085] Refining endpoint: Si = 0.30%, Mn = 0.45%, temperature 1690℃.

[0086] 4. VD vacuum treatment

[0087] Pre-vacuum stage: The vacuum level drops from 100 Torr to 8 Torr within 6 minutes, and the bottom-blown argon pressure is 5.5 MPa;

[0088] Deep vacuum stage: vacuum degree 0.15 Torr, pulse stirring (frequency 2Hz, pressure fluctuation 3.5MPa), lasting for 20 minutes;

[0089] Air puncture detection: H = 0.8 PPM, N = 110 PPM, temperature 1620℃.

[0090] 5. Titanium alloying

[0091] The wire feeding speed is 2.5 m / s, the wire feeding amount is 4.0 kg / t, the titanium content is 0.35% as monitored by LIBS online, and the recovery rate is 90%.

[0092] 6. Soft-blown argon purification

[0093] The porous breathable brick has a pore size of 0.6 mm, is electromagnetically stirred (frequency 10 Hz, magnetic field strength 0.18 T), and the soft blowing flow rate is 9 L / min·t for 20 minutes.

[0094] Final test results: Oxygen 11 PPM, Nitrogen 85 PPM, Total impurities 0.0035%.

[0095] Example 3

[0096] A process for smelting precipitation-hardening steel for smelting austenitic stainless steel, the specific steps of which are as follows:

[0097] 1. Hot metal pretreatment

[0098] Oxidizing slag stage: CaO 45kg / t, SiO2 12kg / t (CaO / SiO2=3.75), oxygen stirring for 18 minutes, P decreases to 0.009%;

[0099] Reducing slag stage: CaO 28kg / t, Al2O3 8kg / t, MgO 6kg / t, sprayed composite powder (particle size 100μm, CaO:MgO:Al2O3=7:2:1) 9kg / t, stirred for 28 minutes, S≤0.012%;

[0100] Harmful element control: 3.5 kg / t of trapping agent, As ≤ 0.009%, Sn ≤ 0.005%;

[0101] Pretreatment endpoint: Cr 15.8%, Ni 3.8%, Cu 3.5%, Nb 0.20%, temperature 1580℃.

[0102] 2. AOD Refining

[0103] Add 90 kg / t of lime, 8 kg / t of ferrosilicon, and 3.5 kg / t of CaO-C composite powder (particle size 30 μm, CaO:C = 6:1) for three-stage decarburization:

[0104] Initial stage (carbon 0.35%): oxygen-argon ratio 6.5:1, oxygen flow rate 1050 m³ / h 3 / H, lasting 22 minutes;

[0105] Intermediate stage (0.12% carbon): Oxygen-argon ratio 3.5:1, oxygen flow rate 650 MJ / L 3 / H, lasting 28 minutes;

[0106] Final stage (0.06% carbon): Pure argon flow rate 380 MJ / L 3 / H, lasting 15 minutes;

[0107] Endpoint control: carbon 0.025%, temperature 1685℃, O = 38PPM, N = 290PPM.

[0108] 3. LF Secondary Refining

[0109] Initial deoxidation: 1.8 kg / t of aluminum-calcium alloy, stirred for 10 minutes, O decreased to 30 PPM;

[0110] Intermediate deoxidation: 3.5 kg / t of silicon-calcium-barium composite deoxidizer (Si:Ca:Ba = 65:15:20), stirred for 15 minutes;

[0111] Rare earth treatment: Ce-La mixed rare earth 0.08kg / t, stirred for 18 minutes, inclusion size ≤4.5μm;

[0112] Refining endpoint: Si = 0.20%, Mn = 0.30%, temperature 1680℃.

[0113] 4. VD vacuum treatment

[0114] Pre-vacuum stage: The vacuum level drops from 100 Torr to 12 Torr within 8 minutes, and the bottom-blown argon pressure is 4.5 MPa;

[0115] Deep vacuum stage: vacuum degree 0.3 Torr, pulse stirring (frequency 1Hz, pressure fluctuation 2.5MPa), lasting 16 minutes;

[0116] Air puncture detection: H = 1.0 PPM, N = 130 PPM, temperature 1600℃.

[0117] 5. Titanium alloying

[0118] The wire feeding speed was 1.8 m / s, the wire feeding amount was 3.5 kg / t, the titanium content was 0.28% as monitored by LIBS online, and the recovery rate was 86%.

[0119] 6. Soft-blown argon purification

[0120] The porous breathable brick has a pore size of 1.0 mm, is electromagnetically stirred (frequency 6 Hz, magnetic field strength 0.12 T), and the soft blowing flow rate is 7 L / min·t for 30 minutes.

[0121] Final test results: Oxygen 14 PPM, Nitrogen 95 PPM, Total impurities 0.0045%.

[0122] Comparison Table of Key Process Parameters and Performance Indicators in Examples 1-3

[0123]

[0124]

[0125] The above table explains

[0126] Differences in process parameters: By adjusting parameters such as powder particle size (50-100μm), gas ratio (5:1-6.5:1), and vacuum degree (0.15-0.3 Torr), the adaptability of the process to different raw material conditions was verified.

[0127] Performance stability: All three examples achieved oxygen ≤15PPM, nitrogen ≤100PPM, titanium recovery rate ≥85%, and harmful element As / Sn controlled below 0.01%, indicating good process stability;

[0128] Optimization direction: Example 2 obtained the lowest oxygen and nitrogen content (11PPM / 85PPM) by refining the powder particle size (50μm) and extending the vacuum time (20 minutes), which is the optimal parameter combination.

[0129] The working principle of this technical solution is as follows:

[0130] This process improves the purity of molten steel through full-process collaborative control. The core mechanism is as follows:

[0131] Pretreatment stage: The dual-slag method is combined with composite powder injection to rapidly dephosphorize through oxidizing slag and deeply desulfurize through reducing slag, supplemented by As-Sn scavenging agent to remove low-melting-point harmful elements, laying a pure foundation for subsequent refining;

[0132] AOD refining: The three-stage dynamic gas ratio adjusts the oxygen-argon ratio in real time according to the carbon content. The high oxygen stage is used for rapid decarbonization, and the low oxygen stage is used to inhibit nitrogen absorption. The ultra-fine CaO-C powder is used to enhance decarbonization and compensate for temperature loss.

[0133] LF Refining: Gradient deoxidation utilizes aluminum-calcium alloy to rapidly reduce oxygen, silicon-calcium-barium alloy to refine inclusions, and rare earth elements to spheroidize inclusions, achieving a synergistic effect of "deoxidation-purification-modification".

[0134] VD vacuum treatment: Stepped vacuum and pulse stirring destroy the gas-liquid interface layer, promote the diffusion and escape of hydrogen and nitrogen, and reduce the gas content;

[0135] Titanium alloying: Vacuum feeding avoids high-temperature oxidation of titanium, and LIBS online analysis accurately controls the composition, improving alloy utilization.

[0136] Soft blowing purification: The combination of bubble atomization and electromagnetic stirring technology increases the probability of impurity collision, promotes the floating of fine impurities, and ultimately achieves ultra-low oxygen and nitrogen.

[0137] The advantages of this technical solution are:

[0138] Significantly improved purity: oxygen content ≤15PPM (reduced by 30%), nitrogen content ≤100PPM (reduced by 40%), and harmful elements As and Sn controlled below 0.01%, improving the toughness and corrosion resistance of steel;

[0139] Improved titanium recovery rate: Vacuum post-feeding and online control increase the titanium recovery rate from 60%-70% to over 85%, reducing alloy consumption costs;

[0140] Refined control of inclusions: Rare earth metamorphism and composite soft blowing make the inclusion size ≤5μm and spherical, avoiding the risk of cracking caused by stress concentration;

[0141] Enhanced process stability: Technologies such as dynamic gas ratio and stepped vacuum reduce composition fluctuations, increasing the product qualification rate from 85% to 98%.

[0142] High level of intelligence: LIBS online analysis and closed-loop control replace manual sampling, shortening the smelting cycle by 15% and reducing labor intensity.

[0143] This process, through multi-stage innovation and collaboration, breaks through the purity bottleneck of traditional precipitation-hardening steel smelting, and is especially suitable for high-end aerospace, marine engineering and other fields with stringent material performance requirements.

[0144] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for smelting a precipitation hardening steel for smelting an austenitic stainless steel, characterized in that: The method comprises the following steps: (1) Hot metal pretreatment: using a medium-frequency induction furnace to pretreat the hot metal by double-slag method, controlling the composition of the hot metal to meet P≤0.025%, S≤0.015%, Cr 15.50%-17.50%, Ni 3.5%-5.0%, Cu 3.0%-5.0%, Nb 0.15%-0.45%, and the temperature≥1580℃, and spraying CaO-MgO-Al2O3 composite powder to deeply remove phosphorus and sulfur; (2) AOD refining: pouring the pretreated hot metal into an AOD furnace, using "three-stage dynamic gas proportioning" to remove carbon, adding 90-100 kg of lime, 8 kg of ferrosilicon and CaO-C composite powder per ton of hot metal, and controlling the final carbon content to be 0.020%-0.025%; (3) LF secondary refining: after the AOD molten steel is drained, it is transferred into an LF furnace, aluminum-calcium alloy, silicon-calcium-barium composite deoxidizer and rare earth elements are added in sequence through gradient deoxidation process, and the refining time is controlled to be 60-70 minutes; (4) VD vacuum treatment: using a stepwise vacuum system, the vacuum degree is 10-100 torr in the pre-vacuum stage and 0.1-0.3 torr in the deep vacuum stage, and pulse-type bottom-blowing argon stirring is used in cooperation; (5) Titanium alloying: after VD treatment, titanium-aluminum alloy wire is added through wire feeding method, the wire feeding speed is dynamically adjusted by using an online composition analysis system, and the titanium recovery rate is ensured to be≥85%; (6) Soft argon blowing purification: using bubble atomization and electromagnetic stirring composite technology, the soft blowing time is controlled to be 15-30 minutes, so that the oxygen content in the molten steel is≤15 PPM and the nitrogen content is≤100 PPM.

2. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel according to claim 1, characterized in that: The double-slag method pretreatment in step (1) comprises: first making an oxidizing slag to remove 80% of phosphorus, and then making a reducing slag to remove sulfur, the CaO-MgO-Al2O3 composite powder has a particle size of 50-100 μm and is used in an amount of 8-12 kg / t.

3. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel according to claim 1, characterized in that: The three-stage dynamic gas proportioning in step (2) is specifically as follows: Initial: Oxygen to argon ratio 6:1, oxygen flow 1000 M 3 / H; Mid-term: Oxygen to argon ratio 3:1, oxygen flow 600 M 3 / H; End: Pure argon blowing, flow 400 M 3 / H; The mass ratio of CaO to C in the CaO-C composite powder is 5:1, the particle size is <30 μm, and the amount used is 3-5 kg / t.

4. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel according to claim 1, characterized in that: The gradient deoxidation process in step (3) comprises: In the initial stage, 2 kg / t of aluminum-calcium alloy is added to reduce the oxygen content to below 30 PPM; In the middle stage, 4 kg / t (Si:Ca:Ba=60:20:20) of silicon-calcium-barium composite deoxidizer is added; In the final stage, 0.05-0.1 kg / t of Ce-La mixed rare earth is added to control the inclusion size to≤5 μm.

5. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel as claimed in claim 1, wherein: The stepwise vacuum system in step (4) is specifically as follows: In the pre-vacuum stage, the vacuum degree is reduced from 100 torr to 10 torr, and the bottom-blowing argon pressure is 4-6 MPa; In the deep vacuum stage, the vacuum degree is increased to 0.1-0.3 torr, pulse-type argon stirring with a frequency of 1-2 Hz and a pressure fluctuation of 2-4 MPa is applied, and the molten steel temperature is maintained at 1600-1620℃.

6. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel as claimed in claim 1, wherein: The titanium-aluminum alloy wire in step (5) has a Ti:Al mass ratio of 7:3, a diameter of 12 mm, a CaO-MgO protective layer on the surface, and a wire feeding speed of 1-3 m / s; the online composition analysis system uses laser-induced breakdown spectroscopy to control the titanium content in real time with an accuracy of±0.005%.

7. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel as claimed in claim 1, wherein: The bubble atomization and electromagnetic stirring complex technology in step (6) comprises: using a porous gas brick with a pore diameter of 0.5-1 mm to blow argon from the bottom, cooperating with an electromagnetic stirring device with a frequency of 5-10 Hz and a magnetic field strength of 0.1-0.2 T, controlling the bubble size to be 1-3 mm, and controlling the total content of inclusions to be ≤0.005%.

8. A process for smelting a precipitation hardening steel for smelting austenitic stainless steel as claimed in claim 1, wherein: The molten iron pretreatment in step (1) further comprises spraying an As-Sn capturing agent, and the amount is 3-5 kg / t, so that As in the molten steel is ≤0.010%, and Sn is ≤0.005%.

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