A titanium-containing stainless steel smelted by a single-nozzle refining furnace and its refining method

Abstract

The present invention provides a titanium-containing stainless steel smelted by a single-nozzle refining furnace and a refining method thereof. The refining method is to perform vacuum refining on the primary molten steel of stainless steel that meets certain conditions by using a single-nozzle refining furnace with a specific furnace type. The specific vacuum refining is to sequentially perform the treatment processes of decarburization, reduction, slag removal, deep deoxidation, on-line calcium treatment, titanium alloying, and weak argon stirring on the primary molten steel. The present invention performs vacuum slag removal, deep deoxidation, and calcium treatment on the molten steel before titanium alloying to create a low-oxygen condition for titanium alloying, and high-purity stainless steel liquid can be obtained. Compared with the traditional smelting method, the method of the present invention has the application advantages of fast refining efficiency and high titanium recovery rate, and can be used as an effective smelting method for smelting high-purity steel.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel smelting, and particularly to a titanium-containing stainless steel smelted by a single-nozzle refining furnace and a refining method thereof.

Background Art

[0002] Titanium-containing austenitic stainless steel has better high-temperature corrosion resistance than conventional 304 austenitic stainless steel and is widely used as a material for heat-resistant and pressure-resistant pipelines in the fields of petroleum, natural gas, nuclear power, etc. After adding a certain amount of titanium to stainless steel, the intergranular corrosion resistance and strength at high temperatures can be improved. The addition amount is related to the carbon and nitrogen contents in the steel and is usually 5.5 - 7(C + N). However, titanium has strong reducibility and is prone to combine with elements such as O, S, N, and C in the molten steel to form high-melting-point inclusions. Among them, titanium oxide-based and TiN inclusions are the most harmful to smelting and product quality. These high-melting-point inclusions are prone to agglomeration during smelting and solidification, which easily leads to problems such as caking of the protective slag and nodulation of the tundish nozzle; it also reduces product quality, such as surface line scale defects of plates and pipe penetration and delamination defects of bars. Therefore, the smelting control of titanium-containing austenitic stainless steel is a recognized technical difficulty in the industry.

[0003] Appropriate timing of titanium alloying and low-N control of the molten steel during the smelting process are the keys to reducing the generation of high-melting-point titanium-containing inclusions, and the smelting method and process of titanium-containing stainless steel are crucial for inclusion control. Currently, the main smelting methods for titanium-containing stainless steel are the AOD method and the VOD method. There are mainly three difficulties in smelting by the AOD method: 1. Difficult nitrogen control. The denitrification depth is limited during the smelting process under non-vacuum conditions, and nitrogen absorption is inevitable during the tapping process; 2. A large amount of inclusions are generated during the strong slag-steel mixing during the tapping process, reducing the cleanliness of the molten steel; 3. It is difficult to accurately control the slag composition during the subsequent LF process. Although the VOD method has reliable nitrogen control ability, the equipment cost and production cost are high, and feeding and on-line sampling and detection cannot be carried out during the smelting process, reducing the stability of end-point control.

[0004] The single-nozzle refining furnace, abbreviated as "single-nozzle furnace", is a steel liquid vacuum secondary refining device originally developed in China. Long-term industrial batch tests have proved that this furnace type has technical advantages such as high refining efficiency, low production cost, and simple equipment in the smelting of varieties such as electrical steel and bearing steel. Applying the smelting technical advantages of the single-nozzle refining furnace to the smelting of titanium-containing stainless steel is an innovative smelting method. The present invention proposes a smelting method for titanium-containing stainless steel using a single-nozzle refining furnace, which further reduces the number of titanium-containing inclusions in the steel and has a higher titanium recovery rate compared with the existing technical methods.

[0005] Therefore, it is necessary to study a titanium-containing stainless steel smelted by a single-nozzle refining furnace and a refining method thereof to address the deficiencies of the existing technology and solve or alleviate one or more of the above problems.

Summary of the Invention

[0006] In view of this, the present invention provides a titanium-containing stainless steel smelted by a single-nozzle refining furnace and its refining method. Before titanium alloying, the molten steel is subjected to vacuum slag removal, deep deoxidation and calcium treatment to create a low-oxygen condition for titanium alloying, and high-purity stainless steel molten steel can be obtained. Compared with the traditional smelting method, the method of the present invention has the application advantages of fast refining efficiency and high titanium recovery rate, and can be used as an effective smelting method for smelting high-purity steel.

[0007] On the one hand, the present invention provides a refining method for a titanium-containing stainless steel smelted by a single-nozzle refining furnace. The refining method is to carry out vacuum refining on the stainless steel primary molten steel that meets certain conditions by using a single-nozzle refining furnace with a specific furnace type; the specific vacuum refining is to sequentially perform the treatment processes of decarburization, reduction, slag removal, deep deoxidation, on-line calcium treatment, titanium alloying and weak argon stirring on the primary molten steel.

[0008] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The single-nozzle refining furnace with a specific furnace type includes an immersion tube and a ladle. The immersion tube and the ladle are arranged eccentrically. Two independent bottom-blowing porous plugs are assembled at the bottom of the ladle, namely the main porous plug and the auxiliary porous plug. The main porous plug is located directly below the immersion tube and is used for vacuum circulation stirring of the molten steel. The auxiliary porous plug is located below the gap between the immersion tube and the ladle and is used for stirring the molten steel around the immersion tube.

[0009] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The specific conditions that the stainless steel primary molten steel that meets certain conditions satisfies are: the molten steel entering the station: w[C]=0.40-0.70%, w[Si]<0.3%, w[S]<0.005%, the ladle slag thickness ≤ 30mm, and the molten steel temperature is 1550-1580°C.

[0010] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The specific slag removal treatment process is: after the reduction is completed, adjust the vacuum tank pressure to 50-80 kPa, reduce the immersion tube insertion depth to 0.2-0.3 m, increase the blowing intensity of the main porous plug to 8-15 NL / min / ton, continuously stir for 3-8 min, and discharge the top slag in the vacuum tank outside the immersion tube.

[0011] In the above-mentioned aspect and any possible implementation manner, a further implementation manner is provided. The specific deep deoxidation treatment process is: after the slag removal is completed, pump the vacuum pressure to an extremely high vacuum, adjust the insertion depth to 0.3-0.5 m, add aluminum blocks through the vacuum bin for deep deoxidation of the molten steel, and the addition amount is calculated according to the w[Al]0.03-0.05% received by the molten steel, and continuously stir for 2-3 min to complete the deep deoxidation treatment.

[0012] For the aspects and any possible implementation manners as described above, a further implementation manner is provided. A wire feeder is provided on one side of the single-nozzle refining furnace of a specific furnace type. The on-line calcium treatment process specifically involves feeding post-calcium wire into designated areas W1 or W2 on the ladle liquid surface through the wire feeder after the deep deoxidation is completed. The feeding amount is controlled at 3-5 kg per ton of molten steel, and stirring is carried out for 2-5 minutes after wire feeding to complete the on-line calcium treatment.

[0013] For the aspects and any possible implementation manners as described above, a further implementation manner is provided. The titanium alloying treatment process is completed in two steps: rough alloying in a bin and fine control by wire feeding. Among them;

[0014] The rough alloying in the bin specifically involves: adding titanium alloy through a vacuum bin to roughly allocate the Ti content of the molten steel. The addition amount is calculated according to 90% of the lower limit of the preset composition requirements, and the Ti content is determined by sampling 3-5 minutes after addition;

[0015] The fine control by wire feeding specifically involves: for the part where the Ti content in the result of rough alloying in the bin is insufficient for the preset composition requirements, feeding titanium wire into designated areas W1 or W2 of the ladle through the wire feeder to make the Ti content of the molten steel reach the target composition.

[0016] For the aspects and any possible implementation manners as described above, a further implementation manner is provided. The treatment process of weak argon stirring specifically involves: after the titanium alloying treatment, stirring for 2-3 minutes and then reducing the argon blowing amount to 70-80 NL / min, and then soft stirring for 4-6 minutes and then breaking the vacuum.

[0017] For the aspects and any possible implementation manners as described above, a further implementation manner is provided. A titanium-containing stainless steel smelted by a single-nozzle refining furnace has higher purity, and the probability of defects such as delamination and cracking during the rolling process is significantly reduced.

[0018] For the aspects and any possible implementation manners as described above, a further implementation manner is provided. A titanium-containing stainless steel smelted by a single-nozzle refining furnace has production advantages such as high efficiency, strong nitrogen control ability, and high titanium alloy recovery rate, and at the same time brings advantages such as high cleanliness of molten steel and stable product quality.

[0019] Compared with the existing methods for smelting titanium-containing stainless steel, the beneficial effects that can be achieved by the process of the present invention are mainly as follows:

[0020] 1): High titanium recovery rate and few titanium oxide inclusions; the slag removal, deep deoxidation and calcium treatment of the molten steel before titanium alloying in the method of the present invention make the molten steel in a low-oxygen state, effectively inhibiting the oxidation and burning loss of titanium during the titanium alloying process, improving the titanium recovery rate, and at the same time significantly reducing the generation amount of titanium oxide inclusions in the molten steel

[0021] 2): Less titanium nitride inclusions; after the molten steel undergoes vacuum decarburization and degassing treatment, the carbon and nitrogen contents are at a relatively low level. Correspondingly, the required titanium content to be added is also relatively low, fundamentally reducing the generation amount of titanium nitride inclusions;

[0022] 3): The smelting process is simple and more operable; the single-nozzle refining furnace can complete decarburization, Al deoxidation, Ca treatment, and titanium alloying treatment simultaneously at one station, and the treatment effect of each process is controllable.

[0023] Of course, it is not necessary for any product implementing the present invention to achieve all the above-described technical effects simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 is a flowchart provided by an embodiment of the present invention;

[0026] Figure 2 is a structural diagram of the single-nozzle furnace provided by an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the wire feeding area of the wire feeder provided by an embodiment of the present invention.

[0028] Among them, in the figure:

[0029] 1 - ladle, 2 - immersion tube, 3 - main tuyere brick, 4 - auxiliary tuyere brick, 5 - top blowing oxygen lance, 6 - immersion tube insertion depth, 7 - vacuum bin feeding pipe, 8 - vacuum top slag, 9 - wire feeder, 10 - alloy wire, 11 - feeding area W1, 12 - feeding area W2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to better understand the technical solutions of the present invention, the following will describe the embodiments of the present invention in detail with reference to the drawings.

[0031] It should be clear that the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise.

[0033] The present invention provides a titanium-containing stainless steel smelted by a single-nozzle refining furnace and a refining method thereof. The single-nozzle refining furnace used has a specific furnace type structure, such as Figure 2 shown, the ladle 1 and the immersion tube 2 are arranged eccentrically, and there is a certain eccentricity δE between their centers. Two independent bottom-blowing porous plugs are provided at the bottom of the ladle. The main porous plug 3 is located directly below the immersion tube and is used for vacuum circulation stirring of the molten steel. The auxiliary porous plug 4 is located below the gap between the immersion tube and the ladle and is used for stirring the molten steel around the immersion tube. The molten steel is processed through refining processes such as oxygen blowing decarburization, reduction, slag discharging through the immersion tube, deep deoxidation, on-line calcium treatment, on-line titanium alloying, and weak argon stirring in sequence by using the single-nozzle furnace with the above specific structure, such as Figure 1 shown, high-purity stainless steel molten steel can be obtained. The technical descriptions of each process are as follows:

[0034] S0. Control of the conditions of the molten steel entering the station

[0035] Before the single-nozzle furnace treatment, the molten steel entering the station needs to meet certain conditions. The carbon content should meet w[C] 0.4 - 0.7%, the silicon content meets w[Si] < 0.2%, the sulfur content meets w[S] < 0.05%, the ladle slag thickness ≤ 30 mm, and the temperature is 1550 - 1580 °C;

[0036] S1. Vacuum decarburization

[0037] After evacuating, the vacuum pressure is reduced to 10 - 25 kPa, and then forced decarburization treatment of the molten steel is carried out through the top oxygen lance 5, and the insertion depth 6 of the immersion tube into the molten steel is controlled at 0.5 - 0.7 m; when the carbon content drops below 0.15% - 0.20%, the vacuum pressure is further reduced to 1 - 5 kPa, and the insertion depth 6 is controlled at 0.3 - 0.5 m; when the carbon content drops to 0.005 - 0.04%, stop blowing oxygen; the vacuum pressure is reduced to extremely high vacuum (< 66 Pa) for natural decarburization treatment of the molten steel, and the extremely high vacuum treatment time is not less than 5 min, and [N] < 120 ppm is controlled.

[0038] S2. Ferrosilicon reduction

[0039] After decarburization is completed, ferrosilicon alloy is first added into the vacuum chamber through the vacuum bin 7 for reduction treatment. The addition amount of ferrosilicon is calculated according to [Si]=0.2-0.5% in the steel after reduction. After addition, lime is added into the vacuum chamber and stirred for 3-5 min. Adding lime can promote the reduction of chromium oxide in the slag and reduce the erosion of the top slag on the refractories at the same time. The addition amount is controlled within the range of w(CaO) / w(SiO2)=1.5-2.5 according to the basicity R of the top slag after reduction.

[0040] S3. Slag discharging from the dipping tube

[0041] After the reduction is completed, a relatively thick low-basicity slag 8 will float above the molten steel in the vacuum ladle. If it is not discharged, the subsequent titanium yield will be reduced. Slag discharging from the dipping tube means that the top slag 8 in the vacuum ladle is rolled out of the dipping tube 2 by strong stirring with blowing through the main tuyere brick 3; its characteristic lies in that after the reduction is completed, the pressure in the vacuum ladle is adjusted to 50-80 kPa, the insertion depth 6 of the dipping tube is reduced to 0.2-0.3 m, and at the same time the blowing intensity is increased to 8-15 NL / min / ton, and continuous stirring is carried out for 3-8 min, so that most of the top slag in the vacuum ladle can be discharged out of the dipping tube.

[0042] S4. Deoxidation with Al

[0043] Deep deoxidation treatment of the molten steel is the key to obtaining a high Ti yield subsequently. After the slag discharging is completed, the vacuum pressure is pumped to an extremely high vacuum (<66 Pa), the insertion depth is adjusted to 0.3-0.5 m, and aluminum blocks are added through the vacuum bin 7 for deep deoxidation of the molten steel. The addition amount is calculated according to w[Al]0.03-0.05% in the molten steel, and stirring is carried out for 2-3 min to complete the deep deoxidation treatment.

[0044] S5. On-line calcium treatment

[0045] During the deep deoxidation process, a certain amount of high-aluminum inclusions will be generated in the molten steel. Plasticizing them through calcium treatment can effectively avoid the generation of high-melting-point Al-Ti inclusions during the subsequent titanium alloying process. A wire feeder 9 is equipped beside the single-nozzle furnace for on-line calcium treatment, and on-line wire feeding operation can be carried out on the molten steel during the vacuum treatment of the molten steel, as Figure 3 shown. When feeding the wire, the calcium wire 10 needs to be fed into the designated areas W1(11) or W2(12) on the molten steel surface in the ladle. After being fed from this area, the calcium wire can smoothly enter the bottom of the ladle along the downward molten steel flow field, thus ensuring the effectiveness of wire feeding. The feeding amount of the calcium wire should be controlled at 3-5 kg / ton of steel, and stirring is carried out for 2-5 min after wire feeding to complete the on-line calcium treatment.

[0046] S6. On-line titanium alloying

[0047] The titanium alloying of molten steel is completed in two steps: rough alloying in the batching bin and fine control by wire feeding. Rough alloying means adding titanium alloy through the vacuum bin 7 to roughly match the Ti content of the molten steel. The addition amount is calculated according to 90% of the lower limit of the component requirements. After adding for 3 - 5 minutes, a sample is taken to determine the Ti content. The insufficient part is fed into the designated area W1(11) or W2(12) of the ladle by the wire feeder 9 with titanium wire to make the Ti content of the molten steel reach the target component.

[0048] Example 1:

[0049] In Example 1, the steel grade selected for smelting is TP321. The internal control components for smelting this steel grade are shown in Table 1, and the liquidus temperature is 1452 °C. The production of this steel grade is carried out using the "EAF + AOD + SSRF + LF + IC" process flow.

[0050] Table 1 Requirements for internal control components of titanium-containing austenitic stainless steel

[0051]

[0052] (1) The electric arc furnace provides the rough molten steel: the amount of molten steel is 26.2 t, and a steel sample ① is taken after pouring into the AOD.

[0053] (2) AOD refining: Lime, pure nickel, high-chromium and other alloys are added during the decarburization period; ferrosilicon is added during the reduction period, and the slag is skimmed after stirring for 5 minutes; after the slag is completely skimmed, lime and fluorite are added for desulfurization, and a steel sample ② is taken after stirring for 3 minutes and then the slag is drained, and then 29.8 t of steel is tapped.

[0054] (3) Vacuum refining in the single-nozzle refining furnace:

[0055] S0. Initial conditions: A steel sample ③ is taken when the ladle enters the station, the temperature is measured at 1565 °C, and the slag thickness is 25 mm;

[0056] S1. Oxygen blowing for decarburization: When the vacuum pressure drops to 14 kPa, the oxygen lance is lowered to blow oxygen, the oxygen blowing flow rate is 420 m3 / h. After a cumulative oxygen blowing of 85.6 m3, the vacuum pressure is reduced to 6 kPa; the argon blowing amount is increased to 138 NL / min, and the oxygen blowing flow rate is reduced to 310 m 3 / h. After a cumulative oxygen blowing of 152.3 m 3 3, the vacuum pressure is continuously reduced to 1.2 kPa; the argon blowing amount is increased to 156 NL / min, and the oxygen blowing flow rate is reduced to 240 m 3 / h. After a cumulative oxygen blowing of 176.6 m 3 3, oxygen blowing is stopped, a steel sample ④ is taken, and the temperature is measured at 1683 °C;

[0057] S2. Vacuum reduction: The ultimate vacuum is pumped. When the pressure is less than 67 Pa, 196 kg of ferrosilicon is added through the bin. After 2 minutes, 200 kg of lime and 60 kg of fluorite are added, and stirring is carried out for 4 minutes;

[0058] S3. Dross removal from the dipping tube: Adjust the pressure in the vacuum chamber to 62.5 kPa, adjust the lifting height of the ladle so that the insertion depth of the dipping tube is 0.22 m, increase the argon blowing flow rate to 186 NL / min, and continuously stir for 3 min;

[0059] S4 - S5. Deep deoxidation of the molten steel and Ca treatment: Evacuate the electrode to vacuum, lift the ladle and adjust the insertion depth of the dipping tube to 0.33 m, reduce the argon blowing flow rate to 121 NL / min. When the pressure drops to 18 kPa, add 53 kg of aluminum blocks and 158 kg of ferromanganese through the bunker, stir for 3 min, and then feed 68 m of calcium wire through the wire feeder;

[0060] S6. Add 184 kg of pure titanium blocks through the bunker, increase the argon blowing amount to 154 NL / min, stir for 3 min and then take sample ⑤, measure the temperature at 1586 °C; the titanium content in the sample is 0.22%, and feed 12 m of titanium wire through the wire feeder;

[0061] After stirring for 2 min, reduce the argon blowing amount to 71 NL / min, perform soft stirring for 5 min and then break the vacuum.

[0062] (4) LF refining: Take sample ⑥ when entering the station, energize to raise the temperature, add 20 kg of microchromium and 18 kg of ferromanganese, take the molten steel sample ⑦ and lift the ladle after 45 min of refining, measure the temperature at 1542 °C;

[0063] The chemical composition of the molten steel samples during the smelting process is shown in Table 2.

[0064] Table 2 Changes in the composition of the molten steel during the smelting process of the example, %

[0065]

[0066] Table 3 shows the smelting effects of batch production of titanium-containing stainless steel using the process of the example. It can be seen from the table that by using the process of the present invention, the average recovery rate of titanium during the smelting process can be controlled to the level of 90%, and the low titanium burning loss effectively reduces the generation of titanium-containing high-melting-point inclusions; the average smelting time < 90 min, and the refining efficiency is high; the B-type inclusions in the titanium-containing steel are stably controlled to below the level of 1.0.

[0067] Table 3 Ti recovery rate and steel purity effects (mean value) during the SSRF smelting process of the example

[0068]

[0069] Note: Type A is sulfide inclusions, Type B is alumina inclusions, Type C is silicate inclusions, Type D is spherical oxide inclusions, the rating range is from 0 to 3, and the level increases with the increase of the length, quantity, and diameter of the inclusions. For the detailed rating method, see GB / T 10561 - 2005.

[0070] The above has introduced in detail a titanium-containing stainless steel smelted by a single-nozzle refining furnace and its refining method provided by the embodiments of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation of the present application.

[0071] As used in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As mentioned throughout the specification and claims, the terms "comprising" and "including" are open-ended terms, so they should be interpreted as "comprising / including but not limited to". "Substantially" means within an acceptable error range. Those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. The subsequent description in the specification is the preferred implementation manner for implementing the present application, but the description is for the purpose of explaining the general principles of the present application and is not used to limit the scope of the present application. The protection scope of the present application shall be subject to what is defined by the appended claims.

[0072] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a commodity or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such commodity or system. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of another identical element in the commodity or system including the said element.

[0073] It should be understood that the term "and / or" used herein is only a relationship describing associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0074] The above description shows and describes several preferred embodiments of the present application. However, as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge in related fields. And the modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present application should all be within the protection scope of the appended claims of the present application.

Claims

1. A refining method for titanium-containing stainless steel smelted by a single-nozzle refining furnace, characterized in that, The refining method is to perform vacuum refining on the primary molten stainless steel that meets certain conditions using a single-nozzle refining furnace with a specific furnace type; the specific vacuum refining is to sequentially perform the treatment processes of decarburization, reduction, slag removal, deep deoxidation, on-line calcium treatment, titanium alloying, and weak argon stirring on the primary molten steel. The single-nozzle refining furnace with a specific furnace type includes an immersion tube and a ladle, and the immersion tube and the ladle are arranged eccentrically. Two independent bottom-blowing porous plugs are assembled at the bottom of the ladle, namely the main porous plug and the auxiliary porous plug. The main porous plug is located directly below the immersion tube and is used for vacuum circulation stirring of the molten steel. The auxiliary porous plug is located below the gap between the immersion tube and the ladle and is used for stirring the molten steel around the immersion tube. The specific conditions that the primary molten stainless steel meeting certain conditions satisfies are: the molten steel entering the station: w[C]=0.40~0.70%, w[Si]<0.3%, w[S]<0.005%, the thickness of the ladle slag ≤ 30mm, and the temperature of the molten steel is 1550~1580°C. The specific decarburization process is: after vacuum pumping, the vacuum pressure is reduced to 10~25 kPa, and then the molten steel is forced to decarburize by a top-blowing oxygen lance, and the insertion depth of the immersion tube into the molten steel is controlled at 0.5~0.7 m; when the carbon content drops below 0.15%~0.20%, the vacuum pressure is further reduced to 1~5 kPa, and the insertion depth is controlled at 0.3~0.5 m; when the carbon content drops to 0.005~0.04%, stop blowing oxygen; reduce the vacuum pressure to an ultra-high vacuum < 66 Pa to perform natural decarburization treatment on the molten steel, and the ultra-high vacuum treatment time is not less than 5 min, and control [N]<120 ppm. The specific deep deoxidation treatment process is: after slag removal is completed, the vacuum pressure is pumped to an ultra-high vacuum, the insertion depth is adjusted to 0.3~0.5 m, and aluminum blocks are added through a vacuum bin for deep deoxidation of the molten steel. The addition amount is calculated according to w[Al] 0.03~0.05% of the molten steel received, and continuous stirring for 2~3 min completes the deep deoxidation treatment.

2. The refining method according to claim 1, characterized in that, The specific process of weak argon stirring is: after titanium alloying treatment, stir for 2 - 3 min, then reduce the argon blowing amount to 70 - 80 NL / min, and perform soft stirring for 4 - 6 min before breaking the vacuum.

3. The refining method according to claim 1, characterized in that, The specific slag removal treatment process is: after reduction is completed, adjust the pressure in the vacuum tank to 50~80 kPa, reduce the insertion depth of the immersion tube to 0.2~0.3 m, increase the blowing intensity of the main porous plug to 8~15 NL / min / ton, and continuously stir for 3~8 min to discharge the top slag in the vacuum tank outside the immersion tube.

4. A titanium-containing stainless steel smelted by a single-nozzle refining furnace, characterized in that, The titanium-containing stainless steel is obtained by the refining method described in any one of claims 1 - 3 above.

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