Induction furnace bottom blowing device for pressurizing gas phase nitriding and increasing nitrogen by bottom blowing nitrogen and high-nitrogen steel preparation method

Abstract

The invention relates to an induction furnace bottom blowing device for pressurized gas phase nitriding and bottom blowing nitrogen increasing and a high-nitrogen steel preparation method. The bottom blowing device sequentially comprises a pressure reducing valve, a one-way valve, a stop valve, a flow meter and a parallel pipeline from nitrogen output, namely a pipeline where an electromagnetic valve connected with a furnace chamber is located and a bottom blowing pipeline connected with a vent plug. The preparation method of the high-nitrogen steel comprises the steps that after alloy materials are completely molten, an electromagnetic valve is opened, a furnace chamber is filled with nitrogen from an air vent to target pressure, and pressure balance in the furnace chamber and a bottom blowing pipeline can be guaranteed through opening of the electromagnetic valve; after the pressure of the nitrogen is stable, closing the electromagnetic valve, and sequentially opening the pressure reducing valve to the flow meter so as to carry out pressurized bottom blowing; and after nitriding is completed, the pressure reducing valve is sequentially closed to the flowmeter, the electromagnetic valve is opened, and pressurized bottom blowing is stopped. According to the method, the nitrogen increasing rate of the molten steel is remarkably increased, the smelting period is shortened, efficient preparation of the high-nitrogen steel is achieved, and meanwhile the phenomena of ventilation plug blocking and steel leakage are effectively avoided.

Description

Technical Field

[0001] The invention relates to the technical field of high nitrogen steel preparation, and in particular to 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. Background Art

[0002] As a microalloying element, nitrogen is a more effective solid solution strengthener than carbon. It can significantly improve fine grain strengthening. It is also a strong austenite stabilizer, thereby reducing the nickel content required for stabilization and significantly improving pitting resistance. As a special type of high-nitrogen stainless steel, high nitrogen steel has a nitrogen content that exceeds the limit that this type of steel can reach under normal pressure. Thanks to its high strength and toughness, good corrosion resistance, and low or even no magnetism, high nitrogen steel has become a very important new engineering material and has been successfully used 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 affinity for nitrogen can significantly increase the 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 smelting method, (2) pressurized induction furnace smelting method, (3) reverse pressure casting method, (4) pressurized electroslag remelting method, (5) pressurized plasma smelting method, etc. Among them, the pressurized induction furnace smelting method is currently the most promising smelting method for the 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 uneven distribution of nitrogen in the steel. The other is through the gas-melt interface reaction "N2(g)→2[N]", in which N2 gas molecules dissociate to generate nitrogen atoms and enter the melt; pressurized gas phase nitrogen alloying is an efficient, low-cost, pollution-free nitrogen addition technology, which can significantly increase the nitrogen addition rate by increasing the nitrogen pressure and gas-liquid contact area. In addition to pressurized gas phase nitriding on the surface of molten steel, in order to achieve efficient preparation of high nitrogen steel, pressurized bottom blowing nitrogen technology can effectively increase the gas phase nitriding rate and significantly shorten the smelting cycle by increasing the nitrogen-molten steel contact area, enhancing the molten steel convection, and accelerating the mass transfer of nitrogen in the molten 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. In order to deal with this problem, bottom blowing is used to remove the blockage and perform bottom blowing.

[0005] The pressurized bottom blowing nitrogen technology can effectively speed up 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 the introduction of nitrogen into the furnace chamber to the target pressure first: (1) Avoiding denitrification of the molten steel surface due to the low nitrogen pressure in the furnace chamber during pressurized bottom blowing, which affects the gas phase nitriding rate and makes 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 and leaking of the gas plug and the efficient preparation of high nitrogen steel. 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 of use required for using pressurized gas phase 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 the high nitrogen pressure on the surface of the molten steel.

[0008] (II) Technical solution

[0009] To this end, the first aspect of the present invention mentions 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, the temperature is raised and the vacuum is evacuated 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, the solenoid valve is opened, and nitrogen is filled into the furnace chamber from the vent of the induction furnace to the target pressure, and the steel liquid surface pressurized gas phase nitriding stage is entered, and the nitrogen pressure in the bottom blowing pipeline is adjusted to keep the nitrogen pressure in the furnace chamber balanced with the nitrogen pressure in the bottom blowing pipeline;

[0012] Step 3: After the nitrogen pressure is stable, close the solenoid valve, and open the pressure reducing valve, the one-way valve, the stop valve and the 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 charged into the molten steel through the bottom blowing pipeline from the air permeable plug;

[0013] Step 4: After the pressurized gas phase 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 the pressurized bottom blowing.

[0014] Furthermore, the calculation formula for the pressure reducing valve to control the nitrogen pressure 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] Among them, P 减压阀 The pressure reducing valve 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;

[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 addition and the smelting time.

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

[0020] The second aspect of the present application mentions an induction furnace bottom blowing device 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 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] (III) 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 a method for using the device, comprising: after the alloy material is loaded into the crucible, the temperature is increased and the vacuum is evacuated 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, and nitrogen is filled into the furnace chamber from the air vent of the induction furnace to the target pressure, and the pressurized gas phase nitriding stage of the molten steel surface is entered, and the nitrogen pressure in the bottom blowing pipeline is adjusted to maintain the nitrogen pressure in the furnace chamber Balance with the nitrogen pressure in the bottom blowing pipeline; after the nitrogen pressure is stable, close the solenoid valve, and open the pressure reducing valve, one-way valve, stop valve and flow meter in sequence to carry out 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 the pressurized bottom blowing.

[0023] This application ensures that the bottom blowing can be carried out stably and accurately with the design parameters through the synergistic effect of the pressure reducing valve, the one-way valve, the stop valve, the flow meter and the parallel pipeline in the bottom blowing device, and also designs a reasonable bottom blowing pressure and flow rate, completes the precise control and matching of the bottom blowing pressure and flow rate, and realizes the efficient preparation of high nitrogen steel. At the same time, a reasonable use method matching the bottom blowing device is adopted to effectively avoid the blockage of the air plug and the leakage of steel during the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase process in the pressurized induction furnace. The bottom blowing device and the use method of the induction furnace 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 blockage of the air plug and the leakage of steel during 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 A schematic flow chart of a method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement mentioned in the present application;

[0025] Figure 2 This is a schematic diagram of an induction furnace bottom blowing device for pressurized gas phase 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. Check 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 modes in conjunction with the accompanying drawings.

[0029] When amount, concentration or other value or parameter is represented by range, preferred range or a series of upper preferred value and lower preferred value, 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, regardless of whether the range is disclosed separately. For example, when disclosing range "1-5", described range should be interpreted as including range "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, the range is intended to include its end value and all integers and fractions within the range.

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

[0031] refer to Figure 1 The present application mentions a pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increasing induction furnace bottom blowing device and use method thereof, comprising:

[0032] Step 1: After the alloy material is loaded into the crucible 112, the temperature is increased and the crucible is evacuated 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 type of steel, target nitrogen content and smelting temperature), enter 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 stage of pressurized gas phase nitriding on the surface of the molten steel, the electromagnetic valve 120 is in an open state, and other devices in the bottom blowing device are in a closed state. By opening the electromagnetic valve 120, the bottom blowing pipeline and the furnace chamber are in a connected state, and the pressure in the bottom blowing pipeline is equal to the pressure in the furnace chamber, so as to avoid the blockage of the air plug 111 or the occurrence of steel leakage caused by the nitrogen pressure on the surface of the molten steel being much greater than the pressure in the bottom blowing pipeline.

[0035] Step 3: After the nitrogen pressure is stable, 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, and enter the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase stage, wherein the pressure reducing valve 160 is adjusted to control the bottom blowing nitrogen pressure, the flow meter 130 controls the bottom blowing nitrogen flow, and the nitrogen is filled into the molten steel from the air 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 through the bottom blowing pipeline from the air plug 111, 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 gas phase 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 safely and quickly stop the bottom blowing operation and prepare 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 nitrogen into the furnace chamber for pressurized gas phase nitriding of the steel liquid 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. Among them, the pressure reducing valve 160, the one-way valve 150, the stop valve 140, the flow meter 130 and the solenoid valve 120 and other components work together to ensure the accurate supply and control of the bottom blowing nitrogen pressure and flow rate, and keep the pressure in the furnace balanced with the pressure of the bottom blowing pipeline.

[0040] The present invention provides a bottom blowing device for a pressurized induction furnace 110 for pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increase, comprising: in the process of pressurized bottom blowing nitrogen gas 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 nitrogen delivery direction 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, so as to adjust the pressure in the bottom blowing pipeline and keep the pressure in the furnace balanced with the pressure in the bottom blowing pipeline; a breathable plug 111 is rammed and fixed at the bottom center of a crucible 112 by using magnesia, and a good seal is used to avoid steel leakage. By utilizing the above-mentioned bottom blowing device, the blockage or leakage of molten steel at the air plug 111 caused by the nitrogen pressure in the furnace chamber can be effectively reduced. At the same time, the bottom blowing pressure and flow rate can be accurately and efficiently controlled to achieve 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 the present 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] The present 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 bottom blowing flow rate of nitrogen in the bottom blowing device is closely related to the actual amount of molten steel, the amount of nitrogen addition and the smelting time. The bottom blowing flow rate of nitrogen in the bottom blowing device is within the range of 25 to 150 mL / (min·kg), which can effectively avoid the violent splashing of molten steel caused by excessive flow rate, and at the same time, it also helps to ensure the stability and safety of the bottom blowing device.

[0047] In order 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. On the contrary, 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] Embodiment 1

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

[0050] The vent plug 111 is made of alumina and has a vent hole diameter of 1 to 1.5 mm. The flow meter 130 controls the flow rate to be 0.525 to 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 (0.2 MPa) when nitrogen passes through the pipeline, in order to ensure the safety of the equipment, the pressure reducing valve 160 controls the pressure to be 0 to 2.50 MPa, the pressure in the furnace chamber to be 0 to 2.24 MPa, and the bottom blowing nitrogen pressure to be 0 to 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 and 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 gas phase nitriding stage of the molten steel surface is 0.48MPa, and the time is 3min; the bottom blowing nitrogen pressure in the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increasing stage is 0.50MPa (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 12min.

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

[0056] Step 2: After the alloy material is completely melted, first open the solenoid valve 120, and then fill the furnace cavity with nitrogen to 0.48MPa (3min) from the vent 113 of the pressurized induction furnace 110 to enter the pressurized gas phase nitriding stage of the molten steel surface. The nitrogen pressure in the bottom blowing pipeline can be adjusted to keep the nitrogen pressure in the furnace cavity balanced with the nitrogen pressure in the bottom blowing pipeline, effectively avoiding blockage or steel leakage of the pressurized vent plug 111;

[0057] Step 3: After the nitrogen pressure is stable, 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, and enter the pressurized gas 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 0.50MPa, and the flow meter 130 controls the bottom blowing nitrogen flow rate to 2.00L / min, and the nitrogen is charged into the molten steel from the air plug 111 through the bottom blowing pipeline for 12 minutes;

[0058] Step 4: After the pressurized gas phase 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 ingot prepared by smelting method 1

[0060] C Si Mn Cr Mo Ni N S P Fe 0.31 0.49 0.50 15.01 1.00 0.22 0.4021 0.005 0.006 margin

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

[0062] Smelting method 2:

[0063] The induction furnace bottom blowing device for increasing nitrogen by pressurized gas phase nitriding and bottom blowing nitrogen of the present invention is used, but the corresponding high nitrogen steel preparation method is not used, resulting in blockage of the air permeable plug 111, and pressurized bottom blowing cannot be performed. Therefore, in order to prepare 30Cr15Mo1N high nitrogen stainless steel with a target nitrogen content of 0.40%, only pressurized gas phase nitriding on the surface of molten steel is used in the whole process to prepare high nitrogen steel, the nitrogen pressure in the furnace chamber is 0.48MPa, and the time is 28min.

[0064] Step 1: After the alloy material is loaded into the crucible 112, the temperature is raised and the crucible is evacuated to remove water vapor and air, and then the smelting temperature is controlled to be about 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 0.48 MPa (3 min), and the pressurized gas phase nitriding stage of the molten steel surface is entered. The high nitrogen pressure on the surface of the molten steel causes the vent plug 111 to be blocked, and pressurized bottom blowing cannot be performed;

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

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

[0068] C Si Mn Cr Mo Ni N S P Fe 0.30 0.49 0.49 15.01 1.00 0.22 0.4043 0.005 0.006 margin

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

[0070] Embodiment 2

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

[0072] The vent plug 111 is made of alumina and has a vent hole diameter of 1 to 1.5 mm. The flow meter 130 controls the flow rate to be 2.50 to 15.00 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 (0.15 MPa), in order to ensure the safety of the equipment, the pressure reducing valve 160 controls the pressure to be 0 to 1.0 MPa, the pressure in the furnace chamber to be 0 to 0.86 MPa, and the bottom blowing nitrogen pressure to be 0 to 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 and 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 gas phase nitriding stage of the molten steel surface is 0.50MPa, and the time is 3min; the bottom blowing nitrogen pressure in the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increasing stage is 0.54MPa (P 静压力 =0.02MPa, P 损失 =0.15MPa, P 减压阀 =0.74MPa), bottom blowing flow rate is 10.00L / min, and time is 14min.

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

[0077] Step 2: After the alloy material is completely melted, first open the solenoid valve 120, and then fill the furnace cavity with nitrogen to 0.50MPa (3min) from the vent 113 of the pressurized induction furnace 110 to enter the pressurized gas phase nitriding stage of the molten steel surface. The nitrogen pressure in the bottom blowing pipeline can be adjusted to keep the nitrogen pressure in the furnace cavity balanced with the nitrogen pressure in the bottom blowing pipeline, effectively avoiding blockage or steel leakage of the pressurized air plug 111;

[0078] Step 3: After the nitrogen pressure is stable, 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, and enter the pressurized gas 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 0.50MPa, and the flow meter 130 controls the bottom blowing nitrogen flow rate to 10.00L / min, and the nitrogen is charged into the molten steel from the air plug 111 through the bottom blowing pipeline for 14 minutes;

[0079] Step 4: After the pressurized gas phase 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] C Si Mn Cr Mo Ni N S P Fe 0.29 0.49 0.50 15.00 1.01 0.22 0.4012 0.005 0.007 margin

[0082] It can be seen from Table 3 that 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] Embodiment 3

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

[0085] The vent plug 111 is made of alumina and has a vent hole diameter of 1 to 1.5 mm. The flow meter 130 controls the flow rate to be 12.5 to 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 of nitrogen when passing through the pipeline (0.30 MPa), in order to ensure the safety of the equipment, the pressure reducing valve 160 controls the pressure to be 0 to 2.0 MPa, the pressure in the furnace chamber to be 0 to 1.67 MPa, and the bottom blowing nitrogen pressure to be 0 to 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 and 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 gas phase nitriding stage of the molten steel surface is 0.52MPa, and the time is 4min; the bottom blowing nitrogen pressure in the pressurized gas phase nitriding and bottom blowing nitrogen nitrogen increasing stage is 0.57MPa (P 静压力 =0.03MPa, P损失 =0.30MPa, P 减压阀 =0.87MPa), bottom blowing flow rate is 53.00L / min, and time is 15min.

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

[0090] Step 2: After the alloy material is completely melted, first open the solenoid valve 120, and then fill the furnace cavity with nitrogen to 0.52MPa (4min) from the vent 113 of the pressurized induction furnace 110 to enter the pressurized gas phase nitriding stage of the molten steel surface. The nitrogen pressure in the bottom blowing pipeline can be adjusted to keep the nitrogen pressure in the furnace cavity balanced with the nitrogen pressure in the bottom blowing pipeline, effectively avoiding blockage or steel leakage of the pressurized vent plug 111;

[0091] Step 3: After the nitrogen pressure is stable, 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, and enter the pressurized gas 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 0.57MPa, and the flow meter 130 controls the bottom blowing nitrogen flow rate to 53.00L / min, and the nitrogen is charged into the molten steel from the air plug 111 through the bottom blowing pipeline for 15min;

[0092] Step 4: After the pressurized gas phase 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] C Si Mn Cr Mo Ni N S P Fe 0.32 0.50 0.51 15.00 1.01 0.24 0.4015 0.005 0.007 margin

[0095] It can be seen from Table 4 that Example 3 can efficiently and accurately obtain 30Cr15Mo1N high-nitrogen stainless steel ingots 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 technician in the field 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 the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

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

[0099] In the present invention, unless otherwise clearly specified and limited, when a first feature is “on” or “below” a second feature, it may be 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. Moreover, when a first feature is “above”, “above” or “above” a second feature, it may be that the first feature is directly above or obliquely above the second feature, or it may simply mean that the first feature is higher in level than the second feature. When a first feature is “below”, “below” or “below” a second feature, it may be that the first feature is directly below or obliquely below the second feature, or it may simply mean that the first feature is lower in level than the second feature.

[0100] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations 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 the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0101] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of 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 to increase nitrogen, characterized in that: include: Step 1: After the alloy material is loaded into the crucible, the temperature is raised and the vacuum is evacuated 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, the solenoid valve is opened, and nitrogen is filled into the furnace chamber from the vent of the induction furnace to the target pressure, and the steel liquid surface pressurized gas phase nitriding stage is entered, and the nitrogen pressure in the bottom blowing pipeline is adjusted to keep the nitrogen pressure in the furnace chamber balanced with the nitrogen pressure in the bottom blowing pipeline; Step 3: After the nitrogen pressure is stable, close the solenoid valve, and open the pressure reducing valve, the one-way valve, the stop valve and the 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 charged into the molten steel through the bottom blowing pipeline from the air permeable plug; Step 4: After the pressurized gas phase 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 the pressurized bottom blowing.

2. The method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement 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 an 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 nitrogen enhancement according to claim 1, characterized in that: The calculation formula for the nitrogen pressure controlled by the pressure reducing valve is: P 减压阀 =P 底吹 +P 损失 =(1.02~1.10)×(P 氮气 +P 静压力 )+P 损失 ; Among them, P 减压阀 The pressure reducing valve 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; 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. The method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement according to claim 1, characterized in that: 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.

5. The method for preparing high nitrogen steel by pressurized vapor nitriding and bottom blowing nitrogen nitrogen enhancement according to claim 4, characterized in that: The bottom blowing flow rate is 25 to 150 mL / (min·kg).

6. An induction furnace bottom blowing device for pressurized gas phase nitriding and bottom blowing nitrogen to increase nitrogen, used in a method for preparing high nitrogen steel by pressurized gas phase nitriding and bottom blowing nitrogen to increase nitrogen as claimed in any one of claims 1 to 5, characterized in that: The bottom blowing device comprises: a pressure reducing valve, a one-way valve, a stop valve, a flow meter and a parallel pipeline; The parallel pipeline includes 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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