CN111500930A - Component control method of ultrapure stainless steel for nuclear power - Google Patents
Component control method of ultrapure stainless steel for nuclear power Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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Abstract
The invention discloses a component control method of a nuclear power ultra-pure stainless steel, which comprises the steps of molten steel smelting, AOD primary refining, L F refining, RH dehydrogenation and L F re-refining, wherein in the step of molten steel smelting, molten iron of a converter smelted by the converter and alloy mother liquor smelted by an intermediate frequency furnace are blended into raw material molten steel, in the step of AOD primary refining, the raw material molten steel is filled into an AOD furnace for primary refining, oxygen blowing and decarburization are carried out on the molten steel through an oxygen lance, after the oxidation period is finished, primary reduction and desulfurization are carried out, then secondary reduction and desulfurization are carried out through a slagging ultra-pure system, in the step of L F refining, the molten steel out of the AOD furnace is filled into a L F furnace for adjusting alloy components to be close to the target value of main components of the molten steel of smelting end point, in the step of RH dehydrogenation, the limit vacuum degree in the steel is controlled to be not more than 2mbar, argon is blown at the bottom, in the step of L F re-refining, and L F furnace is returned to carry out alloy micro-regulation and nitrogen increasing operation.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a component control method of a nuclear power ultra-pure stainless steel.
Background
In order to gradually accelerate the construction of nuclear power industry in China, the nuclear power steel material is more and more in demand, and the nuclear power plant has high quality requirements on nuclear power products due to high quality risk and extremely high safety level requirements in the operation process. At present, the 'fourth generation' nuclear power technology builds demonstration projects in China, and the fast reactor of the 'fast neutron reactor' belongs to the latest fourth generation nuclear power technology in the world, so that stainless steel materials for a fast reactor container structural member and an in-reactor structural member are required to have good high-temperature oxidation resistance, welding performance, cold processing performance and hot processing performance; high toughness and strength; the stainless steel material has extremely high nuclear stability, so the stainless steel material is required to be pure, has low content of boron, cobalt and vanadium, has extremely low content of inclusions, and has no defects such as cracks and the like.
From the aspect of safety of the reactor vessel, extremely high requirements are put on all indexes of materials. The stainless steel hot rolled plate type adopted by the fast reactor container structural member and the reactor internals is 316 austenitic stainless steel, the 316 austenitic stainless steel is more corrosion-resistant stainless steel developed on the basis of 304 stainless steel, 2-3% of Mo element is added into the steel, the mass fraction of carbon in the 316 austenitic stainless steel is 0.040% -0.050%, the steel belongs to high-carbon type stainless steel, carbide is easy to precipitate along a grain boundary when the steel is used under a high-temperature condition, and the precipitated carbide can become a main reason of the reduction of hydrogen embrittlement resistance, so that the risk of long-term operation of the material is increased. Therefore, the lower the mass fraction of hydrogen in the 316 austenitic stainless steel, the better. Meanwhile, the steel is used as a material for a main structural part of easy stacking and has excellent high-temperature strength, so that the mass fraction of nitrogen in 316 austenitic stainless steel is ensured while hydrogen is removed. For a conventional smelting process route of 316 austenitic stainless steel, no special control requirement is required on hydrogen content in component design, and the influence of nitrogen on final use performance is not considered, the hydrogen content in molten steel at the smelting end point of the conventional 316 austenitic stainless steel smelting process is about 6ppm, the nitrogen content is about 400ppm, and the requirement of stainless steel materials for nuclear power on purity is difficult to meet.
Meanwhile, the stainless steel for nuclear power is required to have a longer service life, and correspondingly, the product is required to have higher fatigue resistance, and the size and the type of inclusions in the steel are main factors influencing the fatigue performance of steel. In addition, the stainless steel material for nuclear power is required to have extremely high nuclear stability, so that the requirement on the content of impurity elements in molten steel is extremely high.
Therefore, it is a technical problem to be solved by those skilled in the art to develop a method for controlling components of a nuclear power ultra-pure stainless steel to obtain a nuclear power ultra-pure stainless steel satisfying the requirement of purity.
Disclosure of Invention
In order to solve the technical problems, the invention provides a component control method of a nuclear power ultra-pure stainless steel, wherein the target values of the main components of molten steel at the smelting end point of the method in percentage by mass are that C is 0.04-0.05%, Si is less than or equal to 0.6%, Mn is less than or equal to 1.5%, P is less than or equal to 0.030%, S is less than or equal to 0.003%, Cr is 16.0-18.0%, Ni is 10.0-13.0%, Mo is 2.0-3.0%, and N is 0.05-0.07%, the method comprises the following process steps of molten steel smelting, AOD primary refining, L F refining, RH dehydrogenation and L F re-refining, wherein:
(1) in the molten steel smelting step, molten iron of a converter prepared by smelting the converter and alloy mother liquor prepared by smelting the intermediate frequency furnace are mixed into raw molten steel;
(2) in the AOD primary refining step, raw material molten steel is filled into an AOD furnace, the molten steel is primarily refined in the AOD furnace, oxygen blowing and decarburization operations are carried out on the molten steel through an oxygen lance, after the oxidation period is finished, oxidation products and oxides oxidized into slag are subjected to primary reduction and desulfurization operations, secondary reduction and desulfurization operations are carried out through a slagging system, and the mass percent (%) range of AOD tapping components is controlled as follows:
| composition (I) | C | Si | Mn | P | S | Cr | Ni | Mo |
| Control range | 0.03～0.04 | 0.35～0.45 | 1.40～1.60 | ≤0.017 | ≤0.002 | 17.40～17.80 | 12.1～12.3 | 2.50～2.70 |
(3) L F, in the refining step, the molten steel discharged from the AOD furnace is put into a L F furnace to adjust the alloy components to be close to the target value of the main components of the molten steel at the smelting end point, wherein the adding amount of the alloy material is determined according to the measured components of the molten steel and the target value of the main components of the molten steel at the smelting end point, and the adding amount of the slag-making material is adjusted according to the slag condition;
(4) in the RH dehydrogenation step, after the steel ladle reaches a station, controlling the ultimate vacuum degree in the steel ladle to be less than or equal to 2mbar, carrying out bottom blowing argon gas stirring, controlling the flow of argon gas to be more than 1200N L/min, controlling the time of bottom blowing argon gas to be more than 30min, and controlling the temperature of molten steel to be more than or equal to 1600 ℃;
(5) l F, in the refining step, the molten steel returns to the L F furnace to perform alloy fine adjustment and nitrogen increasing operation, wherein the adding amount of the slag-making material is determined according to the thickening condition of the steel slag, and the adding amount of the alloy material is determined according to the measured components of the molten steel.
Preferably, in the step of the AOD primary refining, in order to ensure that carbon in molten steel is oxidized preferentially to chromium, the temperature in the AOD furnace is controlled to be more than or equal to 1600 ℃.
Preferably, in the AOD primary refining step, nitrogen gas is blown to the bottom side of the AOD furnace and the molten steel is stirred with the nitrogen gas during the primary reduction and desulfurization operation and the secondary reduction and desulfurization operation.
Preferably, in the AOD primary refining step, when oxygen blowing and decarburization operation is carried out on molten steel through an oxygen lance, the oxygen blowing amount is determined according to the content of carbon fed into a furnace and the amount of the molten steel; and in the later stage of oxygen blowing, sampling and detecting the carbon content in the molten steel, and determining the oxygen blowing amount in the later stage of oxygen blowing according to the sampling and detecting result.
Preferably, in the AOD primary refining step, the primary reduction and desulfurization operation includes reducing and desulfurizing a deoxidized product contained in the molten steel by adding ferrosilicon to the molten steel, and the Si content of the molten steel after the primary reduction and desulfurization operation is controlled to be 0.20 to 0.50%, and the slagging system of the secondary reduction and desulfurization operation includes adding slag formers, such as lime and fluorite, to the molten steel and increasing the basicity of the slag(CaO/SiO2) The control is 1.5-2.5.
Preferably, in the AOD primary refining step, the AOD tapping temperature is controlled to be more than or equal to 1600 ℃.
Preferably, in the L F refining step, after the alloy material and the slag former are added, argon gas with medium flow is adopted to stir the molten steel.
Preferably, in the L F refining step, the temperature of the molten steel is increased, so that the outlet temperature of L F is controlled to be more than or equal to 1600 ℃.
Preferably, in the RH dehydrogenation step, a clearance of more than or equal to 1100mm is kept above the steel ladle, and the molten steel is broken when the liquid level is stable after being fully stirred under the ultimate vacuum degree, and temperature measurement and sampling are carried out.
Preferably, in the step of refining the L F again, the temperature is raised after slag adjustment and gold component blending, the temperature of the molten steel is controlled to 1600 ℃, then nitrogen increasing operation is carried out by adopting the maximum nitrogen flow, sampling is carried out after nitrogen increasing is carried out for 5min, and after the components of the molten steel are qualified, argon is adopted for weak stirring and cooling to the tapping temperature of 1500 ℃.
As a specific embodiment, in the composition control method of the above ultra-pure stainless steel for nuclear power, after the L F re-refining step, a CCM casting step is performed to produce a continuous cast slab.
Preferably, in the CCM casting step, molten steel with qualified composition is cast into a continuous casting billet with the width of 2040mm and the thickness of 200 mm.
Preferably, in the method for controlling the components of the nuclear power ultra-pure stainless steel, the slagging material is lime, fluorite or dolomite.
By utilizing the component control method of the nuclear power ultra-pure stainless steel, the mass percent (%) of the main components in the molten steel at the smelting end point can reach the following target: 0.04-0.05% of C, less than or equal to 0.6% of Si, less than or equal to 1.5% of Mn, less than or equal to 0.030% of P, less than or equal to 0.003% of S, 16.0-18.0% of Cr, 10.0-13.0% of Ni, 2.0-3.0% of Mo and 0.05-0.07% of N; the impurity elements in the molten steel at the smelting end point can be controlled to the following levels: as is less than 0.005%, Sb is less than 0.005%, Bi is less than 0.005%, Sn is less than 0.005%, Pb is less than 0.005%, Al is less than 0.03%, B is less than 0.001%, Co is less than 0.06%, Se is less than 0.015%, V is less than 0.05%, and Zn is less than 0.01%; the hydrogen content in the molten steel at the smelting end point is less than 2ppm, and the total oxygen content is less than 25 ppm; the balance being Fe. Furthermore, the inclusions in the ultra-pure stainless steel continuous casting billet prepared by the method for controlling the components of the ultra-pure stainless steel for nuclear power are graded according to GB/T10561A, wherein four types A, B, C, D are respectively less than or equal to 1.0 grade, and the sum of the four types is not more than 2.0 grade. Therefore, the component control method of the nuclear power ultra-pure stainless steel can meet the requirement of the nuclear power stainless steel material on purity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The method for controlling the components of the nuclear power ultra-pure stainless steel adopts a special refining process route that a converter + an intermediate frequency furnace → an AOD (argon oxygen refining) → L F (ladle refining) → RH (vacuum cycle degassing) → L F → (continuous casting system), a blended alloy mother liquid is filled into an AOD furnace, primary refining is carried out in the AOD furnace, the alloy components are adjusted in a L F furnace to be close to the target components of the end point, dehydrogenation operation is carried out in the CCM furnace, fine adjustment of the alloy components and nitrogen addition operation are carried out in a L F furnace, the quality of the molten steel is qualified, and the stainless steel is finally cast into a nuclear power stainless steel.
Specifically, the method for controlling the components of the nuclear power ultra-pure stainless steel comprises the following process steps of molten steel smelting, AOD primary refining, L F refining, RH dehydrogenation, L F refining again and finally casting into a continuous casting billet with high quality through CCM, wherein:
(1) in the step of smelting molten steel, molten iron of a converter smelted by the converter and alloy mother liquor smelted by an intermediate frequency furnace are blended into raw molten steel, wherein the P content of the molten iron of the converter discharged from the furnace is controlled to be less than or equal to 0.015 percent, and the slag thickness is controlled to be less than or equal to 100 mm;
(2) in the AOD primary refining step, raw material molten steel is charged into an AOD furnace, the molten steel is primarily refined in the AOD furnace, oxygen blowing decarburization operation is performed on the molten steel through an oxygen lance, primary reduction and desulfurization operation are performed on oxidation products and oxides oxidized into slag after an oxidation period is finished, and secondary reduction and desulfurization operation are performed through a slagging system, wherein the primary reduction and desulfurization operation comprises reduction and desulfurization of deoxidation products in the molten steel by adding ferrosilicon into the molten steel, and Si content in the molten steel is controlled to be 0.20-0.50%, the slagging system of the secondary reduction and desulfurization operation comprises adding slagging materials such as lime, fluorite, dolomite and the like into the molten steel, and slag (CaO/SiO) is added into the slag2) Controlling the tapping temperature to be more than or equal to 1600 ℃, and controlling the mass percent (%) range of the AOD tapping components as follows:
| composition (I) | C | Si | Mn | P | S | Cr | Ni | Mo |
| Control range | 0.03～0.04 | 0.35～0.45 | 1.40～1.60 | ≤0.017 | ≤0.002 | 17.40～17.80 | 12.1～12.3 | 2.50～2.70 |
(3) L F, in the refining step, the molten steel discharged from the AOD furnace is put into a L F furnace to adjust the alloy components so as to be close to the target value of the main components of the molten steel at the smelting end point;
(4) in the RH dehydrogenation step, after the steel ladle reaches a station, controlling the ultimate vacuum degree in the steel ladle to be less than or equal to 2mbar, carrying out bottom blowing argon gas stirring, controlling the flow of argon gas to be more than 1200N L/min, controlling the time of bottom blowing argon gas to be more than 30min, and controlling the temperature of molten steel to be more than or equal to 1600 ℃;
(5) l F, in the refining step again, the molten steel returns to a L F furnace to carry out alloy fine adjustment and nitrogen increasing operation, and the nuclear power ultra-pure stainless steel with qualified components and purity is smelted;
(6) and in the CCM casting step, a continuous casting billet with high quality is prepared.
Preferably, in the AOD primary refining step, in order to ensure that carbon in the molten steel is oxidized preferentially to chromium, the temperature in the AOD furnace is controlled to be kept high enough to be more than or equal to 1600 ℃.
Preferably, in the above AOD primary refining step, nitrogen gas is blown to the bottom side of the AOD furnace during the primary and secondary reduction and desulfurization operations, whereby the molten steel is stirred with nitrogen gas, not only providing sufficient kinetic conditions for the reduction reaction, but also achieving the purpose of primary nitrogen addition.
Preferably, in the AOD primary refining step, when oxygen blowing and decarburization operation is performed on molten steel through an oxygen lance, the secondary model determines oxygen blowing amount according to the content of carbon entering the furnace and the amount of the molten steel; and in the later stage of oxygen blowing, measuring the temperature, sampling and detecting the carbon content in the molten steel, and determining the oxygen blowing amount in the later stage of oxygen blowing by the secondary model according to the sampling and detecting result.
Preferably, in the L F refining step, after the molten steel reaches the L F furnace, the adding amount of the alloy material is determined according to the measured components of the molten steel and the target value of the main components of the molten steel at the smelting end point, and the adding amount of the slagging material such as lime, fluorite, dolomite and the like is adjusted according to the slag condition so as to ensure good fluidity of the slag.
Preferably, in the L F refining step, the molten steel is stirred by argon gas with medium flow after the alloy materials and the slag-forming materials are added.
Preferably, in the L F refining step, the temperature of the molten steel is raised, so that the outlet temperature of L F is controlled to be more than or equal to 1600 ℃.
Preferably, in the RH dehydrogenation step, a clearance of more than or equal to 1100mm is kept above the steel ladle, and the molten steel is broken when the liquid level is stable after being fully stirred under the ultimate vacuum degree, and temperature measurement and sampling are carried out.
Preferably, in the L F re-refining step, the molten steel is subjected to temperature measurement, sampling and hydrogen determination, the addition amounts of slag-making materials such as lime and fluorite are determined according to the viscosity condition of the steel slag, the addition amount of alloy materials is determined according to actually measured components of the molten steel, slag and alloy components are adjusted and heated, the temperature of the molten steel is controlled to 1600 ℃, nitrogen increasing operation is performed by adopting the maximum nitrogen flow, sampling is performed after nitrogen increasing is performed for 5min, and after the components of the molten steel are qualified, the temperature is reduced to 1500 ℃ of tapping temperature by adopting argon weak stirring.
Preferably, in the CCM casting step, molten steel with qualified composition is cast into a continuous casting billet with the width of 2040mm and the thickness of 200 mm.
By utilizing the component control method of the nuclear power ultra-pure stainless steel, the mass percent (%) of the main components in the molten steel at the smelting end point can reach the following target: 0.04-0.05% of C, less than or equal to 0.6% of Si, less than or equal to 1.5% of Mn, less than or equal to 0.030% of P, less than or equal to 0.003% of S, 16.0-18.0% of Cr, 10.0-13.0% of Ni, 2.0-3.0% of Mo and 0.05-0.07% of N; the impurity elements in the molten steel at the smelting end point can be controlled to the following levels: as is less than 0.005%, Sb is less than 0.005%, Bi is less than 0.005%, Sn is less than 0.005%, Pb is less than 0.005%, Al is less than 0.03%, B is less than 0.001%, Co is less than 0.06%, Se is less than 0.015%, V is less than 0.05%, and Zn is less than 0.01%; the hydrogen content in the molten steel at the smelting end point is less than 2ppm, and the total oxygen content is less than 25 ppm; the balance being Fe.
For example, as a specific example of the method for controlling the components of the nuclear power ultra-pure stainless steel of the present invention, the mass percentages (%) of the components in the molten steel at the smelting end point can reach:
main elements:
| element name | C | Si | Mn | Cr | P | S | Ni | Mo | N |
| Percent by mass (%) | 0.045 | 0.40 | 1.46 | 17.62 | 0.015 | 0.001 | 12.25 | 2.64 | 0.07 |
Residual elements:
| names of elements of five harmful effects | As | Sb | Bi | Sn | Pb | / |
| Percent by mass (%) | 0.0041 | 0.001 | 0.0005 | 0.001 | 0.001 | / |
| Names of other elements | Al | B | Co | Se | V | Zn |
| Percent by mass (%) | 0.0041 | 0.00032 | 0.0238 | 0.002 | 0.031 | 0.001 |
Residual gas:
hydrogen (H) content: 1.79ppm, Total Oxygen (TO) content 22 ppm;
the balance being Fe.
In addition, A, B, C, D four types of inclusions in the ultra-pure stainless steel continuous casting billet prepared by the method for controlling the components of the ultra-pure stainless steel for nuclear power are respectively less than or equal to 1.0 grade, and the sum of the four types of inclusions is not more than 2.0 grade. For example, the ultra-pure stainless steel continuous casting billet prepared by the method for controlling the components of the ultra-pure stainless steel for nuclear power is rolled into 10 pieces (number 1-10) of hot-rolled stainless steel middle plates with the thickness of 35mm and 65mm, and the non-metallic inclusions of the steel plates are graded according to GB/T10561A, and the results are shown in the following table:
the following description will explain the composition control method of the ultra-pure stainless steel for nuclear power according to the present invention with reference to specific examples.
Example 1
The method for controlling the components of the nuclear power ultra-pure stainless steel in example 1 comprises the steps of converter and intermediate frequency furnace smelting, AOD primary refining, L F refining, RH dehydrogenation, L F secondary refining and slab casting, and the following steps are explained in detail:
1) adding 132 tons of low-phosphorus molten iron discharged from the converter and high-chromium molten iron discharged from the intermediate frequency furnace into the AOD furnace, measuring the temperature at 1460 ℃, starting top oxygen blowing and bottom side oxygen blowing, adding high-carbon ferrochrome, ferromolybdenum, a nickel plate and electrolytic manganese in the oxygen blowing process to perform alloying operation, and adding lime, fluorite and dolomite for slagging;
2) after top blowing oxygen for 20 minutes, stopping blowing oxygen, sampling, measuring the content of C to be 0.0145%, adding low-aluminum ferrosilicon, supplementing high-carbon ferrochrome according to earlier-stage sampling components, beginning a reduction period, sampling after 10 minutes, and controlling the range of the main components of the molten steel according to mass percent (%) at the moment:
| composition (I) | C | Si | Mn | P | S | Cr | Ni | Mo |
| Control range | 0.032 | 0.38 | 1.45 | 0.00164 | 0.001 | 17.60 | 12.15 | 2.58 |
The components meet the specification, the temperature of the molten steel is controlled to 1650 ℃, and the slag-removing and steel-tapping are carried out to a furnace of L F;
3) l F, measuring temperature in the furnace, continuing to heat up, adding lime, fluorite and aluminum powder to adjust slag, adding high-carbon ferromanganese, ferromolybdenum, a nickel plate and low-aluminum ferrosilicon to finely adjust alloy components, simultaneously requiring bottom blowing nitrogen, wherein the flow is 600N L/min, measuring temperature again and sampling, stopping power supply heating when the temperature reaches 1650 ℃, and controlling the range of main components of molten steel according to mass percent (%):
| composition (I) | C | Si | Mn | P | S | Cr | Ni | Mo |
| Control range | 0.049 | 0.44 | 1.52 | 0.00173 | 0.001 | 17.53 | 12.15 | 2.58 |
After the components are qualified, opening the ladle into an RH furnace for dehydrogenation operation;
4) after the RH furnace is fed, covering the furnace cover and performing vacuumizing operation, simultaneously blowing argon at the bottom to stir the molten steel, controlling the flow of the argon to be 1200N L/min, controlling the vacuum degree to be less than 2mbar after vacuumizing for 30 minutes, increasing the flow of the argon to be 1800N L/min, stirring for 30 minutes, breaking the air, and feeding the molten steel into a L F furnace for the second time;
5) measuring the temperature of 1550 ℃ after the steel enters the furnace of L F for the second time, sampling and detecting the components of the molten steel, wherein the range of the main components of the molten steel in percentage by mass (%) is controlled as follows:
| composition (I) | C | Si | Mn | P | S | Cr | Ni | Mo | N |
| Control range | 0.049 | 0.44 | 1.52 | 0.00173 | 0.001 | 17.53 | 12.15 | 2.58 | 0.028 |
And (3) electrically heating, when the temperature reaches 1600 ℃, bottom blowing nitrogen at the flow rate of 1200N L/min, sampling after 20 minutes, stopping blowing the nitrogen after the content of N in the molten steel is measured to be 0.0585%, then bottom blowing argon at the flow rate of 300N L/min, tapping when the temperature is reduced to 1500 ℃, and preparing for casting.
The above examples are only for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The method for controlling the components of the nuclear power ultra-pure stainless steel is characterized by comprising the following steps of molten steel smelting, AOD primary refining, L F refining, RH dehydrogenation and L F re-refining, wherein the target values of the main components of molten steel at the smelting end point of the method in percentage by mass are that C is 0.04-0.05%, Si is less than or equal to 0.6%, Mn is less than or equal to 1.5%, P is less than or equal to 0.030%, S is less than or equal to 0.003%, Cr is 16.0-18.0%, Ni is 10.0-13.0%, Mo is 2.0-3.0% and N is 0.05-0.07%, and the method for controlling the components of the nuclear power ultra-pure stainless steel comprises the steps of molten steel smelting, AOD primary:
(1) in the molten steel smelting step, molten iron of a converter prepared by smelting the converter and alloy mother liquor prepared by smelting the intermediate frequency furnace are mixed into raw molten steel;
(2) in the AOD primary refining step, raw material molten steel is filled into an AOD furnace, the molten steel is primarily refined in the AOD furnace, oxygen blowing and decarburization operations are carried out on the molten steel through an oxygen lance, after the oxidation period is finished, oxidation products and oxides oxidized into slag are subjected to primary reduction and desulfurization operations, secondary reduction and desulfurization operations are carried out through a slagging system, and the mass percent (%) range of AOD tapping components is controlled as follows:
(3) L F, in the refining step, the molten steel discharged from the AOD furnace is put into a L F furnace to adjust the alloy components to be close to the target value of the main components of the molten steel at the smelting end point, wherein the adding amount of the alloy material is determined according to the measured components of the molten steel and the target value of the main components of the molten steel at the smelting end point, and the adding amount of the slag-making material is adjusted according to the slag condition;
(4) in the RH dehydrogenation step, after the steel ladle reaches a station, controlling the ultimate vacuum degree in the steel ladle to be less than or equal to 2mbar, carrying out bottom blowing argon gas stirring, controlling the flow of argon gas to be more than 1200N L/min, controlling the time of bottom blowing argon gas to be more than 30min, and controlling the temperature of molten steel to be more than or equal to 1600 ℃;
(5) l F, in the refining step, the molten steel returns to the L F furnace to perform alloy fine adjustment and nitrogen increasing operation, wherein the adding amount of the slag-making material is determined according to the thickening condition of the steel slag, and the adding amount of the alloy material is determined according to the measured components of the molten steel.
2. The method for controlling the composition of an ultrapure stainless steel for nuclear power as recited in claim 1, wherein in the AOD primary refining step, the oxygen blowing amount is determined based on the carbon content of the charged steel and the amount of molten steel during the oxygen blowing and decarburization operation of the molten steel by the oxygen lance; and in the later stage of oxygen blowing, sampling and detecting the carbon content in the molten steel, and determining the oxygen blowing amount in the later stage of oxygen blowing according to the sampling and detecting result.
3. The method for controlling the composition of an ultrapure stainless steel for nuclear power as recited in claim 1, wherein in said AOD primary refining step, nitrogen gas is blown to the bottom side of the AOD furnace and the molten steel is stirred with nitrogen gas during the primary reduction and desulfurization operation and the secondary reduction and desulfurization operation.
4. The method for controlling the composition of an ultrapure stainless steel for nuclear power as claimed in claim 1, wherein in the AOD primary refining step, the primary reduction and desulfurization operation comprises reducing and desulfurizing a deoxidized product of a molten steel by adding ferrosilicon to the molten steel and controlling the Si content of the molten steel to 0.20 to 0.50%, and the slagging system of the secondary reduction and desulfurization operation comprises adding a slag-forming material to the molten steel and reducing the basicity of the slag (CaO/SiO) to the slag2) The control is 1.5-2.5.
5. The method for controlling the composition of an ultrapure stainless steel for nuclear power as claimed in claim 1, wherein in the AOD primary refining step, the temperature in the AOD furnace is controlled to be not less than 1600 ℃, and the AOD tapping temperature is controlled to be not less than 1600 ℃.
6. The method for controlling the components of the ultra-pure stainless steel for nuclear power as claimed in claim 1, wherein in the L F refining step, after the alloy material and the slag former are added, the molten steel is stirred by argon gas with medium flow.
7. The method for controlling the composition of an ultrapure stainless steel for nuclear power as claimed in claim 1 wherein in said L F refining step, the L F exit temperature is controlled to not less than 1600 ℃.
8. The method for controlling the components of the ultrapure stainless steel for nuclear power as recited in claim 1, wherein in the step of refining again at L F, the temperature is raised after slag adjustment and gold component blending, the temperature of the molten steel is controlled to 1600 ℃, then the nitrogen increasing operation is performed by adopting the maximum nitrogen flow, the sampling is performed after the nitrogen increasing operation is performed for 5min, and the temperature is reduced to 1500 ℃ of tapping temperature by adopting argon weak stirring after the molten steel components are qualified.
9. The composition control method of an ultrapure stainless steel for nuclear power as recited in any one of claims 1 to 8 wherein a CCM casting step is performed after the L F re-refining step to produce a continuous cast slab.
10. The method for controlling the composition of the nuclear power ultra-pure stainless steel according to any one of claims 1 to 8, wherein the slagging material is lime, fluorite or dolomite.
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