An induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen and a method for preparing high nitrogen steel

Abstract

The present invention mentions an induction furnace bottom blowing device for pressurized gas phase nitriding and bottom blowing nitrogen to increase nitrogen, and a high nitrogen steel preparation method. The bottom blowing device is composed of a pressure reducing valve, a one-way valve, a stop valve, a flow meter and a parallel pipeline, which are sequentially connected to the nitrogen output, namely the pipeline where the solenoid valve connected to the furnace chamber is located, and the bottom blowing pipeline connected to the vent. The high nitrogen steel preparation method comprises: after the alloy material is completely melted, the solenoid valve is opened, and nitrogen is filled into the furnace chamber from the vent to the target pressure. The opening of the solenoid valve can ensure the pressure balance between the furnace chamber and the bottom blowing pipeline; after the nitrogen pressure stabilizes, the solenoid valve is closed, and the pressure reducing valve is opened to the flow meter in sequence to perform pressurized bottom blowing; after the nitriding is completed, the pressure reducing valve is closed to the flow meter in sequence, the solenoid valve is opened, and the pressurized bottom blowing is stopped. The present invention significantly improves the nitrogen increase rate of molten steel, shortens the smelting cycle, and realizes the efficient preparation of high nitrogen steel. At the same time, it also effectively avoids the occurrence of vent plug blockage and steel leakage.

Description

Technical Field

[0001] The present invention relates to the technical field of high nitrogen steel preparation, in particular to an induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen, and a high nitrogen steel preparation method. Background Art

[0002] As a microalloying element, nitrogen is a more effective solid solution strengthener than carbon, significantly enhancing grain refinement. It also acts as a strong austenite stabilizer, thereby reducing the nickel content required for stabilization and significantly improving pitting corrosion resistance. High-nitrogen steel, a special type of high-nitrogen stainless steel, has a nitrogen content exceeding the maximum achievable for this type of steel at atmospheric pressure. Thanks to its high strength and toughness, excellent corrosion resistance, and low or even no magnetism, high-nitrogen steel has become a very important new engineering material, successfully applied in oil and gas extraction, energy, aerospace, and other fields.

[0003] The nitrogen solubility of molten steel depends on temperature, nitrogen pressure and alloy composition. Among them, adding alloying elements with high nitrogen affinity can significantly increase nitrogen solubility, but the cost is high. Only by increasing the nitrogen pressure can the nitrogen solubility be significantly increased and the preparation cost of high nitrogen steel be controlled. With the development of high-pressure smelting technology, a series of smelting methods for the preparation of high nitrogen steel have been proposed: (1) hot isostatic pressing melting method, (2) pressurized induction furnace melting method, (3) reverse pressure casting method, (4) pressurized electroslag remelting method, (5) pressurized plasma melting method, etc. Among them, pressurized induction furnace melting method is currently the most promising smelting method for industrial production of high nitrogen steel. Nitrogen is transferred to the melt through two basic mechanisms: the traditional nitrogen alloying method increases nitrogen by adding nitriding alloys, but it will pollute the molten steel and cause the nitrogen to be unevenly distributed in the steel. Another method is through the gas-melt interface reaction "N2(g)→2[N]," in which N2 gas molecules dissociate to form nitrogen atoms that enter the melt. Pressurized vapor-phase nitrogen alloying is an efficient, low-cost, and pollution-free nitrogen addition technology that significantly increases the nitrogen addition rate by increasing nitrogen pressure and gas-liquid contact area. In addition to pressurized vapor-phase nitriding of the molten steel surface, pressurized bottom-blown nitrogen technology can effectively increase the vapor-phase nitriding rate and significantly shorten the smelting cycle by increasing the nitrogen-molten steel contact area, enhancing molten steel convection, and accelerating nitrogen mass transfer in the molten steel to achieve efficient production of high-nitrogen steel.

[0004] At present, nitrogen bottom blowing technology has been successfully applied in the smelting process of nitrogen-containing stainless steel in AOD / VOD furnace to improve preparation efficiency and reduce costs. However, it is not a pressurized smelting equipment, so there is no pressurized nitrogen atmosphere on the surface of the molten steel. However, the high static pressure of the molten steel caused by the high depth of the molten steel will cause the molten steel to flow into the breathable bricks and cause blockage. To address this problem, bottom blowing is used to remove the blockage and restore the flow.

[0005] The pressurized bottom blowing nitrogen technology can effectively accelerate the gas phase nitriding rate and significantly shorten the smelting cycle by increasing the contact area between nitrogen and molten steel, enhancing the convection of molten steel, and accelerating the mass transfer of nitrogen in molten steel. However, the use of pressurized bottom blowing nitrogen technology in a pressurized induction furnace requires that nitrogen be introduced into the furnace chamber to the target pressure first: (1) It is avoided that the denitrification of the molten steel surface due to the low nitrogen pressure in the furnace chamber during the pressurized bottom blowing nitrogen addition will affect the gas phase nitriding rate and make it impossible to accurately control the nitrogen content of the molten steel; (2) Compared with the static pressure of the molten steel, the high nitrogen pressure in the furnace chamber exerts a greater nitrogen pressure on the surface of the molten steel, which is more likely to cause the molten steel to block the gas plug and even leak steel. Therefore, based on the pressurized induction furnace, it is very important to develop an induction furnace bottom blowing device and a method of using pressurized gas phase nitriding and bottom blowing nitrogen to prevent the blockage of the gas plug and leak steel, and to prepare high nitrogen steel efficiently. Summary of the Invention

[0006] (1) Technical issues to be resolved

[0007] The technical problem to be solved by the present invention is to design a pressurized bottom blowing device and a method for using pressurized vapor nitriding and bottom blowing nitrogen nitrogen increase technology in a pressurized induction furnace, while efficiently and accurately controlling the bottom blowing pressure and flow rate, avoiding the occurrence of molten steel blocking the permeable plug and steel leakage caused by high nitrogen pressure on the surface of the molten steel.

[0008] (2) Technical solution

[0009] To this end, the first aspect of the present invention provides a method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen, comprising:

[0010] Step 1: After the alloy material is loaded into the crucible, it is heated and vacuumed to remove the water vapor and air in the pressurized induction furnace, and then the smelting temperature is controlled according to the target steel grade;

[0011] Step 2: After the alloy material is completely melted, open the solenoid valve and fill nitrogen into the furnace chamber from the vent of the induction furnace to the target pressure, entering the steel liquid surface pressurized gas phase nitriding stage, and adjust the nitrogen pressure in the bottom blowing pipeline to keep the nitrogen pressure in the furnace chamber and the nitrogen pressure in the bottom blowing pipeline balanced;

[0012] Step 3: After the nitrogen pressure stabilizes, close the solenoid valve, and open the pressure reducing valve, one-way valve, stop valve and flow meter in sequence to perform pressurized bottom blowing, entering the pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve is adjusted to control the bottom blowing nitrogen pressure, the flow meter controls the bottom blowing nitrogen flow, and the nitrogen is charged into the molten steel from the air plug through the bottom blowing pipeline;

[0013] Step 4: After the pressurized vapor nitriding and bottom blowing nitrogen nitrogen increase stages are completed, close the pressure reducing valve, one-way valve, stop valve and flow meter in sequence, open the solenoid valve, and stop pressurized bottom blowing.

[0014] Furthermore, the calculation formula for the nitrogen pressure controlled by the pressure reducing valve is:

[0015] P 减压阀 = P 底吹 + P 损失 =(1.02~1.10)×( P 氮气 + P 静压力 )+ P 损失 ;

[0016] in, P 减压阀 To control nitrogen pressure with pressure reducing valve, P 底吹 is the bottom blowing nitrogen pressure, P 损失 is the pressure loss of nitrogen when passing through the pipeline, P 氮气 is the nitrogen pressure in the furnace chamber, P 静压力 is the static pressure of molten steel;

[0017] The bottom blowing nitrogen pressure is greater than the sum of the nitrogen pressure in the furnace chamber and the static pressure of the molten steel.

[0018] Furthermore, the flow rate of bottom blowing nitrogen is related to the actual amount of molten steel, the amount of nitrogen added and the smelting time.

[0019] Furthermore, the bottom blowing flow coefficient is 25 ~ 150 mL / (min·kg).

[0020] The second aspect of the present application mentions a bottom blowing device for an induction furnace for pressurized gas phase nitriding and bottom blowing nitrogen to increase nitrogen, which is used in a high nitrogen steel preparation method for pressurized gas phase nitriding and bottom blowing nitrogen to increase nitrogen as described in the first aspect above. The bottom blowing device includes: a pressure reducing valve, a one-way valve, a stop valve, a flow meter and a parallel pipeline; wherein the parallel pipeline includes a pipeline where the solenoid valve connected to the furnace chamber is located, and a bottom blowing pipeline connected to the air plug.

[0021] (3) Beneficial effects

[0022] The beneficial effects of the present invention are as follows: the present invention mentions an induction furnace bottom blowing device for pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase and its use method, comprising: after the alloy material is loaded into the crucible, the temperature is increased and vacuumed to remove the water vapor and air in the induction furnace, and then the smelting temperature is controlled according to the target steel grade; after the alloy material is completely melted, the solenoid valve is opened, nitrogen is filled into the furnace cavity from the air vent of the induction furnace to the target pressure, and the steel liquid surface is entered into the pressurized gas phase nitriding stage, and the nitrogen pressure in the bottom blowing pipeline is adjusted to maintain the nitrogen pressure in the furnace cavity. Balance with the nitrogen pressure in the bottom blowing pipeline; after the nitrogen pressure stabilizes, close the solenoid valve, and open the pressure reducing valve, one-way valve, stop valve and flow meter in sequence to perform pressurized bottom blowing, and enter the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve is adjusted to control the bottom blowing nitrogen pressure, the flow meter controls the bottom blowing nitrogen flow, and the nitrogen is filled into the molten steel through the bottom blowing pipeline from the air plug; after the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase stage are completed, close the pressure reducing valve, one-way valve, stop valve and flow meter in sequence, open the solenoid valve, and stop pressurized bottom blowing.

[0023] The present application ensures that it can perform stable and accurate bottom blowing with design parameters through the synergistic effect of the pressure reducing valve, one-way valve, stop valve, flow meter and parallel pipeline in the bottom blowing device, and also designs a reasonable bottom blowing pressure and flow, completes the precise control and matching of the bottom blowing pressure and flow, and realizes the efficient preparation of high nitrogen steel. At the same time, a reasonable use method matched with the bottom blowing device is adopted to effectively avoid the vent plug clogging and steel leakage in the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase process in the pressurized induction furnace. The induction furnace bottom blowing device and the use method using pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase significantly improve the nitrogen increase rate of the molten steel, shorten the smelting cycle, and realize the efficient preparation of high nitrogen steel. At the same time, it also effectively avoids the vent plug clogging and steel leakage in the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase process in the pressurized induction furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic flow chart of a method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen mentioned in this application;

[0025] Figure 2 This is a schematic diagram of an induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen mentioned in this application.

[0026] Description of Reference Numerals

[0027] 110. Pressurized induction furnace; 111. Ventilation plug; 112. Crucible; 113. Vent; 120. Solenoid valve; 130. Flow meter; 140. Stop valve; 150. One-way valve; 160. Pressure reducing valve. DETAILED DESCRIPTION

[0028] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0029] When amount, concentration or other value or parameter are represented with range, preferred range or the range that a series of upper preferred value and lower preferred value limit are expressed, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope " 1-5 ", described scope should be interpreted as including scope " 1-4 ", " 1-3 ", " 1-2 ", " 1-2 and 4-5 ", " 1-3 and 5 " etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within this range.

[0030] In these embodiments, unless otherwise specified, the parts and percentages are all calculated by mass. "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1 g or 3.527 g. If we say that the mass parts of component A are a parts and the mass parts of component B are b parts, then the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass parts of all components is not limited to 100 parts. "And / or" is used to indicate that one or both of the situations described may occur. For example, A and / or B includes (A and B) and (A or B).

[0031] refer to Figure 1 This application mentions a pressurized vapor nitriding and bottom blowing nitrogen nitrogen increase induction furnace bottom blowing device and use method mentioned in the present invention, including:

[0032] Step 1: After the alloy material is loaded into the crucible 112, the temperature is increased and vacuumed to remove the water vapor and air in the pressurized induction furnace 110, and then the appropriate smelting temperature is controlled according to the target steel grade.

[0033] Step 2: After the alloy material is completely melted, open the solenoid valve 120 and fill nitrogen into the furnace chamber from the vent 113 of the pressurized induction furnace 110 to the target pressure (designed according to the steel type, target nitrogen content and smelting temperature), entering the pressurized gas phase nitriding stage on the surface of the molten steel, and adjust the nitrogen pressure in the bottom blowing pipeline to keep the nitrogen pressure in the furnace chamber balanced with the nitrogen pressure in the bottom blowing pipeline.

[0034] It should be noted that during the pressurized vapor nitriding stage of the molten steel surface, solenoid valve 120 is open, while the other devices in the bottom blowing apparatus are closed. Opening solenoid valve 120 connects the bottom blowing pipeline to the furnace chamber, and the pressure within the bottom blowing pipeline equalizes with the pressure within the furnace chamber. This prevents clogging of the vent plug 111 or steel leakage caused by the nitrogen pressure on the molten steel surface being much greater than the pressure within the bottom blowing pipeline.

[0035] Step 3: After the nitrogen pressure stabilizes, close the solenoid valve 120, and open the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 in sequence to perform pressurized bottom blowing, entering the pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve 160 is adjusted to control the bottom blowing nitrogen pressure, and the flow meter 130 controls the bottom blowing nitrogen flow rate, and the nitrogen is charged into the molten steel from the vent plug 111 through the bottom blowing pipeline.

[0036] It should be noted that by adjusting the pressure of the pressure reducing valve 160 to control the bottom blowing nitrogen pressure, the flow meter 130 accurately controls the bottom blowing nitrogen flow rate, and nitrogen is filled into the molten steel from the air plug 111 through the bottom blowing pipeline, which can significantly increase the gas phase nitriding area and enhance the stirring effect, accelerate the gas phase nitriding speed, and realize pressurized gas phase nitriding and bottom blowing nitrogen efficient nitrogen increase.

[0037] Step 4: After the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enrichment stages are completed, the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 are closed in sequence, the solenoid valve 120 is opened, and the pressurized bottom blowing is stopped.

[0038] This process can stop the bottom blowing operation safely and quickly, while preparing for the next batch of smelting.

[0039] refer to Figure 2 The pressurized induction furnace 110 is a smelting device, the crucible 112 is a vessel for melting metal, and the vent 113 is a gas inlet for filling the furnace chamber with nitrogen for pressurized vapor nitriding of the molten steel surface. In this technical solution, the bottom blowing device includes: a pressure reducing valve 160, a one-way valve 150, a stop valve 140, a flow meter 130, a solenoid valve 120, and a vent plug 111. The pressure reducing valve 160, the one-way valve 150, the stop valve 140, the flow meter 130, and the solenoid valve 120 work together to ensure the accurate supply and control of the bottom blowing nitrogen pressure and flow rate, maintaining a balance between the furnace pressure and the bottom blowing pipeline pressure.

[0040] The present invention provides a bottom blowing device for a pressurized induction furnace 110 for pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase, comprising: in the process of pressurized bottom blowing nitrogen vapor phase nitriding, a pressure reducing valve 160 is used to control the nitrogen pressure of the bottom blowing; a one-way valve 150 and a stop valve 140 are installed to ensure the direction of nitrogen delivery to avoid damage to pipelines and equipment caused by backflow; a flow meter 130 is installed to accurately control the bottom blowing flow rate; the pipeline where the solenoid valve 120 is located is connected in parallel with the bottom blowing pipeline and connected to the pressurized induction furnace 110 to adjust the pressure in the bottom blowing pipeline and maintain the pressure in the furnace balanced with the pressure in the bottom blowing pipeline; a breathable plug 111 is rammed with magnesia and fixed to the bottom center of the crucible 112 to ensure a good seal and prevent steel leakage. The above-mentioned bottom blowing device can effectively reduce the blockage or leakage of molten steel at the air plug 111 caused by the nitrogen pressure in the furnace chamber, and at the same time accurately and efficiently control the bottom blowing pressure and flow rate, thereby realizing pressurized gas phase nitriding of molten steel and efficient nitrogen increase by bottom blowing nitrogen during the smelting process of the pressurized induction furnace 110.

[0041] In this technical solution, further, the calculation formula for controlling the nitrogen pressure by the pressure reducing valve 160 is:

[0042] P 减压阀 = P 底吹 + P 损失 =(1.02~1.10)×( P 氮气 + P 静压力 )+ P 损失 ; (1)

[0043] In formula (1), P 减压阀 The pressure reducing valve 160 controls the nitrogen pressure. P 底吹 is the bottom blowing nitrogen pressure, P 损失 is the pressure loss of nitrogen when passing through the pipeline, P 氮气 is the nitrogen pressure in the furnace chamber, P 静压力 is the static pressure of molten steel;

[0044] Specifically, the bottom blowing nitrogen pressure is the nitrogen pressure filled into the molten steel through the bottom blowing pipeline, wherein the bottom blowing nitrogen pressure is greater than the sum of the nitrogen pressure in the furnace chamber and the static pressure of the molten steel.

[0045] This application clarifies the relationship between the controlled nitrogen pressure of the pressure reducing valve 160 and the bottom blowing nitrogen pressure, the static pressure of the molten steel and the pressure loss when the nitrogen passes through the pipeline. The pressure reducing valve 160 can be controlled according to actual conditions to ensure the stable output of the bottom blowing pressure and avoid adverse effects of excessive or low pressure on the bottom blowing device and smelting.

[0046] In this technical solution, the nitrogen flow rate in the bottom-blowing unit is closely related to the actual amount of molten steel, the amount of nitrogen added, and the smelting time. A nitrogen flow coefficient within the bottom-blowing unit of 25 to 150 mL / (min·kg) effectively prevents violent splashing of molten steel caused by excessive flow, while also helping to ensure the stability and safety of the bottom-blowing unit.

[0047] To better understand the technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0048] Example 1

[0049] The smelting equipment used is a 25 kg pressurized induction furnace 110 with an ultimate vacuum of 0.5 Pa, a maximum operating pressure of 2.5 MPa, and a furnace load of 21 kg;

[0050] The vent plug 111 is made of alumina, and the diameter of its vent hole is 1 ~ 1.5 mm; the flow meter 130 controls the flow rate to be 0.525 ~ 3.15 L / min; based on the formula [1], the maximum operating pressure of the pressurized induction furnace 110, the static pressure of the molten steel and the pressure loss of nitrogen when passing through the pipeline (0.2 MPa), in order to ensure the safety of the equipment, the pressure reducing valve 160 controls the pressure to be 0 ~ 2.50 MPa, the pressure in the furnace chamber to be 0 ~ 2.24 MPa, and the bottom blowing nitrogen pressure to be 0 ~ 2.30 MPa.

[0051] The mass fractions of the alloy raw materials are as follows: C: 0.32%, Si: 0.50%, Mn: 0.52%, Cr: 15.01%, Mo: 1.00%, Ni: 0.23% and Fe (balance);

[0052] The target composition of 30Cr15Mo1N high nitrogen stainless steel is: C: 0.25 ~ 0.35%, Si: ≤1.00%, Mn: ≤1.00%, Cr: 14.00 ~ 16.00%, Mo: 0.85 ~ 1.10%, Ni: ≤0.50%, N: 0.30 ~ 0.50% and Fe (balance);

[0053] Smelting method 1:

[0054] The induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement and the high nitrogen steel preparation method of the present invention are used to prepare 30Cr15Mo1N high nitrogen stainless steel with a target nitrogen content of 0.40%. The smelting temperature is about 1540 ° C, the nitrogen pressure in the pressurized vapor nitriding stage on the surface of the molten steel is 0.48 MPa, and the time is 3 min; the bottom blowing nitrogen pressure in the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement stage is 0.50 MPa ( P 静压力 =0.01MPa, P 损失 =0.20MPa, P 减压阀 =0.7MPa), bottom blowing flow rate is 2.00L / min, and time is 12 min.

[0055] Step 1: After the alloy material is loaded into the crucible 112, the crucible is heated and evacuated to remove water vapor and air, and the smelting temperature is then controlled to be approximately 1540°C;

[0056] Step 2: After the alloy material is completely melted, the solenoid valve 120 is first opened, and then nitrogen is filled into the furnace chamber from the vent 113 of the pressurized induction furnace 110 to 0.48 MPa (3 minutes), entering the stage of pressurized gas phase nitriding on the surface of the molten steel. The nitrogen pressure in the bottom blowing pipeline can be adjusted to maintain the nitrogen pressure in the furnace chamber and the nitrogen pressure in the bottom blowing pipeline in balance, effectively avoiding blockage or steel leakage of the pressurized vent plug 111;

[0057] Step 3: After the nitrogen pressure stabilizes, close the solenoid valve 120, and open the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 in sequence to perform pressurized bottom blowing, entering the pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve 160 is adjusted to control the bottom blowing nitrogen pressure to 0.50 MPa, and the flow meter 130 is adjusted to control the bottom blowing nitrogen flow to 2.00 L / min, and nitrogen is charged into the molten steel from the vent plug 111 through the bottom blowing pipeline for 12 minutes;

[0058] Step 4: After the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enrichment stages are completed, the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 are closed in sequence, the solenoid valve 120 is opened, and the pressurized bottom blowing is stopped.

[0059] Table 1 shows the composition (%) of 30Cr15Mo1N high nitrogen stainless steel ingots prepared by smelting method 1

[0060]

[0061] As can be seen from Table 1, smelting method 1 can efficiently and accurately obtain 30Cr15Mo1N high nitrogen stainless steel ingots with target nitrogen content, and the vent plug 111 is not blocked.

[0062] Smelting method 2:

[0063] The induction furnace bottom blowing apparatus of the present invention, utilizing both pressurized vapor nitriding and bottom-blown nitrogen nitrogen enrichment, but without the corresponding high-nitrogen steel preparation method, resulted in clogging of the vent plug 111, preventing pressurized bottom blowing. Therefore, to prepare 30Cr15Mo1N high-nitrogen stainless steel with a target nitrogen content of 0.40%, the entire process involved only pressurized vapor nitriding of the molten steel surface. The nitrogen pressure in the furnace chamber was 0.48 MPa, and the duration was 28 minutes.

[0064] Step 1: After the alloy material is loaded into the crucible 112, the crucible is heated and evacuated to remove water vapor and air, and the smelting temperature is then controlled to be approximately 1540°C;

[0065] Step 2: After the alloy material is melted, without opening the solenoid valve 120, nitrogen is then charged into the furnace chamber from the vent 113 of the pressurized induction furnace 110 to a pressure of 0.48 MPa (3 minutes), entering the pressurized vapor phase nitriding stage on the surface of the molten steel. The high nitrogen pressure on the surface of the molten steel causes the vent plug 111 to become blocked, making pressurized bottom blowing impossible;

[0066] Step 3: To complete the preparation of high nitrogen steel, continue pressurized vapor nitriding of the steel liquid surface for 25 min.

[0067] Table 2 shows the composition (%) of 30Cr15Mo1N high nitrogen stainless steel ingots prepared by smelting method 2

[0068]

[0069] As can be seen from Table 2, smelting method 2 can more accurately obtain 30Cr15Mo1N high-nitrogen stainless steel ingots with the target nitrogen content, but it will cause the vent plug 111 to be blocked, and high-nitrogen steel can only be prepared by surface pressurized vapor nitriding. Compared with smelting method 1, the preparation cycle is greatly extended.

[0070] Example 2

[0071] The smelting equipment used is a 100 kg pressurized induction furnace 110, with an ultimate vacuum of 0.5 Pa, a maximum operating pressure of 1.0 MPa, and a furnace load of 95 kg;

[0072] The vent plug 111 is made of alumina, and the diameter of its vent hole is 1 ~ 1.5 mm; the flow meter 130 controls the flow rate to 2.50 ~ 15.00 L / min; based on formula [1], the maximum operating pressure of the pressurized induction furnace 110, the static pressure of the molten steel and the pressure loss when nitrogen passes through the pipeline (0.15 MPa), in order to ensure the safety of the equipment, the pressure reducing valve 160 controls the pressure to 0 ~ 1.0 MPa, the pressure in the furnace chamber to 0 ~ 0.86 MPa, and the bottom blowing nitrogen pressure to 0 ~ 0.90 MPa.

[0073] The mass fractions of the alloy raw materials are as follows: C: 0.30%, Si: 0.50%, Mn: 0.51%, Cr: 15.00%, Mo: 1.01%, Ni: 0.22% and Fe (balance);

[0074] The target composition of 30Cr15Mo1N high nitrogen stainless steel is: C: 0.25 ~ 0.35%, Si: ≤1.00%, Mn: ≤1.00%, Cr: 14.00 ~ 16.00%, Mo: 0.85 ~ 1.10%, Ni: ≤0.50%, N: 0.30 ~ 0.50% and Fe (balance);

[0075] The induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement and the high nitrogen steel preparation method of the present invention are used to prepare 30Cr15Mo1N high nitrogen stainless steel with a target nitrogen content of 0.40%. The smelting temperature is about 1550 ° C, the nitrogen pressure in the pressurized vapor nitriding stage on the surface of the molten steel is 0.50 MPa, and the time is 3 min; the bottom blowing nitrogen pressure in the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement stage is 0.54 MPa ( P 静压力 =0.02MPa, P 损失 =0.15MPa, P 减压阀 =0.74MPa), bottom blowing flow rate is 10.00 L / min, and time is 14 min.

[0076] Step 1: After the alloy material is loaded into the crucible 112, the crucible is heated and vacuumed to remove water vapor and air, and the smelting temperature is then controlled to be approximately 1550°C;

[0077] Step 2: After the alloy material is completely melted, the solenoid valve 120 is first opened, and then nitrogen is filled into the furnace chamber from the vent 113 of the pressurized induction furnace 110 to 0.50 MPa (3 minutes), entering the stage of pressurized gas phase nitriding on the surface of the molten steel. The nitrogen pressure in the bottom blowing pipeline can be adjusted to maintain the nitrogen pressure in the furnace chamber and the nitrogen pressure in the bottom blowing pipeline in balance, effectively avoiding blockage or steel leakage of the pressurized vent plug 111;

[0078] Step 3: After the nitrogen pressure stabilizes, close the solenoid valve 120, and open the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 in sequence to perform pressurized bottom blowing, entering the pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve 160 is adjusted to control the bottom blowing nitrogen pressure to 0.50 MPa, and the flow meter 130 controls the bottom blowing nitrogen flow to 10.00 L / min, and nitrogen is charged into the molten steel from the vent plug 111 through the bottom blowing pipeline for 14 minutes;

[0079] Step 4: After the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enrichment stages are completed, the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 are closed in sequence, the solenoid valve 120 is opened, and the pressurized bottom blowing is stopped.

[0080] Table 3 shows the composition (%) of the 30Cr15Mo1N high nitrogen stainless steel ingot prepared in Example 2

[0081]

[0082] As can be seen from Table 3, Example 3 can efficiently and accurately obtain a 30Cr15Mo1N high-nitrogen stainless steel ingot with a target nitrogen content, and the air plug 111 is not blocked.

[0083] Example 3

[0084] The smelting equipment used is a 500 kg pressurized induction furnace 110 with an ultimate vacuum of 0.5 Pa, a maximum operating pressure of 2.0 MPa, and a furnace load of 480 kg;

[0085] The vent plug 111 is made of alumina, and the diameter of its vent hole is 1 ~ 1.5 mm; the flow meter 130 controls the flow rate to 12.5 ~ 75 L / min; based on the formula [1], the maximum operating pressure of the pressurized induction furnace 110, the static pressure of the molten steel and the pressure loss when the nitrogen passes through the pipeline (0.30 MPa), in order to ensure the safety of the equipment, the pressure reducing valve 160 controls the pressure to 0 ~ 2.0 MPa, the pressure in the furnace chamber to 0 ~ 1.67 MPa, and the bottom blowing nitrogen pressure to 0 ~ 1.70 MPa.

[0086] The mass fractions of the alloy raw materials are as follows: C: 0.33%, Si: 0.52%, Mn: 0.52%, Cr: 15.01%, Mo: 1.01%, Ni: 0.24% and Fe (balance);

[0087] The target composition of 30Cr15Mo1N high nitrogen stainless steel is: C: 0.25 ~ 0.35%, Si: ≤1.00%, Mn: ≤1.00%, Cr: 14.00 ~ 16.00%, Mo: 0.85 ~ 1.10%, Ni: ≤0.50%, N: 0.30 ~ 0.50% and Fe (balance);

[0088] The induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement and the high nitrogen steel preparation method of the present invention are used to prepare 30Cr15Mo1N high nitrogen stainless steel with a target nitrogen content of 0.40%. The smelting temperature is about 1550 ° C, the nitrogen pressure in the pressurized vapor nitriding stage on the surface of the molten steel is 0.52 MPa, and the time is 4 min; the bottom blowing nitrogen pressure in the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement stage is 0.57 MPa ( P 静压力 =0.03MPa, P 损失 =0.30MPa, P 减压阀 =0.87MPa), the bottom blowing flow rate is 53.00 L / min, and the time is 15 min.

[0089] Step 1: After the alloy material is loaded into the crucible 112, the crucible is heated and evacuated to remove water vapor and air, and the smelting temperature is then controlled to be approximately 1550°C;

[0090] Step 2: After the alloy material is completely melted, the solenoid valve 120 is first opened, and then nitrogen is filled into the furnace chamber from the vent 113 of the pressurized induction furnace 110 to 0.52 MPa (4 minutes), entering the stage of pressurized gas phase nitriding on the surface of the molten steel. The nitrogen pressure in the bottom blowing pipeline can be adjusted to maintain the nitrogen pressure in the furnace chamber and the nitrogen pressure in the bottom blowing pipeline in balance, effectively avoiding blockage or steel leakage of the pressurized vent plug 111;

[0091] Step 3: After the nitrogen pressure stabilizes, close the solenoid valve 120, and open the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 in sequence to perform pressurized bottom blowing, entering the pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve 160 is adjusted to control the bottom blowing nitrogen pressure to 0.57 MPa, and the flow meter 130 is adjusted to control the bottom blowing nitrogen flow to 53.00 L / min, and nitrogen is charged into the molten steel from the vent plug 111 through the bottom blowing pipeline for 15 minutes;

[0092] Step 4: After the pressurized vapor nitriding and bottom blowing nitrogen nitrogen enrichment stages are completed, the pressure reducing valve 160, the one-way valve 150, the stop valve 140 and the flow meter 130 are closed in sequence, the solenoid valve 120 is opened, and the pressurized bottom blowing is stopped.

[0093] Table 4 shows the composition (%) of the 30Cr15Mo1N high nitrogen stainless steel ingot prepared in Example 3

[0094]

[0095] As can be seen from Table 4, Example 3 can efficiently and accurately obtain a 30Cr15Mo1N high-nitrogen stainless steel ingot with a target nitrogen content, and the air plug 111 is not blocked.

[0096] The above describes the basic principles, main features, and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any person skilled in the art without departing from the technical solution of the present invention should be included in the patent scope of the present invention.

[0097] In the description of the present invention, each embodiment focuses on the differences from other embodiments, and reference can be made to the same or similar parts between the embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0098] In the description of the present invention, relational terms such as first and second are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined. Moreover, the term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements includes not only those elements, but also includes other elements not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the statement "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements.

[0099] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0100] In the description of this specification, the terms "one embodiment", "some embodiments", "embodiments", "examples", "specific examples" or "some examples" refer to the specific features, structures, materials or characteristics described in conjunction with the embodiment or example and included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0101] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen, characterized in that: include: Step 1: After the alloy material is loaded into the crucible, it is heated and vacuumed to remove the water vapor and air in the pressurized induction furnace, and then the smelting temperature is controlled according to the target steel grade; Step 2: After the alloy material is completely melted, open the solenoid valve and fill nitrogen into the furnace chamber from the vent of the induction furnace to the target pressure, entering the steel liquid surface pressurized gas phase nitriding stage, and adjust the nitrogen pressure in the bottom blowing pipeline to keep the nitrogen pressure in the furnace chamber and the nitrogen pressure in the bottom blowing pipeline balanced; Step 3: After the nitrogen pressure stabilizes, close the solenoid valve, and open the pressure reducing valve, one-way valve, stop valve and flow meter in sequence to perform pressurized bottom blowing, entering the pressurized vapor phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve is adjusted to control the bottom blowing nitrogen pressure, the flow meter controls the bottom blowing nitrogen flow, and the nitrogen is charged into the molten steel from the air plug through the bottom blowing pipeline; The calculation formula for the nitrogen pressure controlled by the pressure reducing valve is: ； in, P 减压阀 To control nitrogen pressure with pressure reducing valve, P 底吹 is the bottom blowing nitrogen pressure, P 损失 is the pressure loss of nitrogen when passing through the pipeline, P 氮气 is the nitrogen pressure in the furnace chamber, P 静压力 is the static pressure of molten steel; The flow rate of bottom blowing nitrogen is related to the actual amount of molten steel, the amount of nitrogen added and the smelting time. The bottom blowing flow coefficient is 25 ~ 150mL / (min·kg); Step 4: After the pressurized vapor nitriding and bottom blowing nitrogen nitrogen increase stages are completed, close the pressure reducing valve, one-way valve, stop valve and flow meter in sequence, open the solenoid valve, and stop pressurized bottom blowing.

2. The method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen according to claim 1, characterized in that: During the pressurized gas phase nitriding stage on the surface of the molten steel, the solenoid valve is in the open state, so that the bottom blowing pipeline and the furnace chamber are in a connected state, and the nitrogen pressure in the furnace chamber is equal to the nitrogen pressure in the bottom blowing pipeline.

3. The method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen according to claim 1, characterized in that: The bottom blowing nitrogen pressure is greater than the sum of the nitrogen pressure in the furnace chamber and the static pressure of the molten steel.

4. An induction furnace bottom blowing device for pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen, used in a method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen to increase nitrogen according to any one of claims 1 to 3, characterized in that: The bottom blowing device includes: a pressure reducing valve, a one-way valve, a stop valve, a flow meter and parallel pipelines; The parallel pipelines include a pipeline where the solenoid valve is located and connected to the furnace chamber, and a bottom blowing pipeline connected to the air plug.

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