Method for determining the minimum solidification pressure of a loose inhibition and its application, method for producing an austenitic stainless steel ingot

Abstract

The present application belongs to the technical field of alloy, and particularly relates to a method for determining the minimum value of solidification pressure for inhibiting porosity and application thereof, and a preparation method of austenitic stainless steel ingot. The method provided by the present application can determine the minimum value of solidification pressure required for inhibiting porosity defects without repeatedly testing in actual production, and the solidification process of the ingot is simulated, and the method is accurate and efficient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alloys, and particularly relates to a method for determining the minimum value of solidification pressure for inhibiting porosity and application thereof and a preparation method of austenitic stainless steel ingot. BACKGROUND

[0002] The austenitic stainless steel is widely applied in the fields of aerospace, petrochemical industry, ship, medical instrument and energy due to excellent corrosion resistance and mechanical performance. However, the porosity defect is easily formed in the solidification process of the austenitic stainless steel ingot. The porosity defect is difficult to be eliminated through subsequent thermal mechanical treatment process, and further causes the mechanical performance of the final product to be seriously affected, and even causes the material to be directly scrapped.

[0003] At present, the method for eliminating the porosity defect in the ingot is generally to add a holding riser to change the feeding condition. However, the method is not high in utilization rate of raw materials, and causes waste of resources. Or the method is to change the height-diameter ratio or height-width ratio of the ingot. However, in order to eliminate the segregation, inclusions and other solidification defects, the austenitic stainless steel ingot generally needs to be treated through subsequent processes such as electroslag remelting and vacuum consumable, and the change of the height-diameter ratio or height-width ratio of the ingot causes the subsequent processes to be unable to be performed. Therefore, the methods are not suitable for preventing the porosity defect in the austenitic stainless steel ingot.

[0004] In view of the above problems, the porosity defect in the austenitic stainless steel ingot can be prevented by applying a solidification pressure to the ingot. The heat exchange condition between the ingot and the mold can be changed and the formation of the porosity can be inhibited by applying a gas-phase solidification pressure in the process of casting and solidification. Therefore, the determination of the solidification pressure value is the key to produce the austenitic stainless steel ingot. The solidification pressure is too low to effectively inhibit the porosity defect, and the solidification pressure is too high to increase the production difficulty, improve the production cost and easily cause safety accidents. At present, the minimum solidification pressure can be determined only through repeated tests in the actual production process, which is time-consuming and laborious. SUMMARY

[0005] The application aims to provide a method for determining the minimum value of solidification pressure for inhibiting porosity and application thereof and a preparation method of austenitic stainless steel ingot. The method provided by the application can determine the minimum value of solidification pressure required for inhibiting the porosity defect without multiple tests in the actual production, and the method is accurate and efficient.

[0006] In order to achieve the above object, the application provides the following technical scheme.

[0007] The application provides a method for determining the minimum value of solidification pressure for inhibiting porosity, comprising the following steps.

[0008] According to the solidification time and the solidification pressure set value P of the target ingot 设 , the interface heat transfer coefficient h between the target ingot and the mold is determined by formula 1;

[0009] According to the composition of the target ingot, the enthalpy value and the density value change rate with temperature during the solidification process of the target ingot are calculated using the Scheil solidification model in the Thermo-Calc thermodynamic calculation software;

[0010] The solidus temperature point T 固 and the liquidus temperature point T 固 of the target ingot are determined;

[0011] According to the interface heat transfer coefficient h, the enthalpy value and the density value change rate with temperature, and the solidus temperature point T r , the solidification process of the target ingot is simulated by PROCAST software;

[0012] Within the range of T 固 ±1℃, several data points of the temperature change with position in the center of the target ingot are extracted, and the temperature gradient G c of the target ingot is determined according to formula 2;

[0013] Within the range of T s ±1℃, several data points of the temperature change with time in the center of the target ingot are extracted, and the temperature-time relationship straight line equation is fitted, and the slope of the straight line equation is the cooling rate v s ;

[0014] The solidification pressure calculation value P 设 is obtained according to formula 3;

[0015] When P 设 ≤P s , the solidification pressure set value P 设 is taken as the minimum value of the solidification pressure;

[0016] When P 设 >P s , the solidification pressure set value P s is increased, the process of obtaining the solidification pressure calculation value P 设 is repeated until P 设 ≤P 设 ;

[0017]

[0018]

[0019]

[0020] P 设 is a solidification pressure set value, in MPa; the solidification pressure set value P 设 is in the range of > 0.1 MPa;

[0021] h is an interface heat exchange coefficient, in w·m -2 ·℃ -1 ;

[0022] t is a solidification time, in s;

[0023] G r is a temperature gradient, in ℃ / m;

[0024] v c is a cooling rate, in ℃ / s;

[0025] f L is a liquid phase volume fraction between dendrites, in the range of 0.8-0.9;

[0026] P s is a solidification pressure calculation value, in MPa.

[0027] Preferably, the method for determining the solidus temperature point T 固 and the liquidus temperature T 液 comprises the following steps:

[0028] a vertical through-hole is punched at the position of half of the vertical height of the outer wall of the cylindrical mold, the diameter of the through-hole is 8 mm; a thermocouple is placed in the through-hole, the temperature measuring point of the thermocouple is 10 mm away from the radial direction of the inner wall of the cylindrical mold;

[0029] the temperature change curve of the molten steel in the solidification process measured by the thermocouple is recorded, and the temperature change curve is differentiated to obtain the solidus temperature T 固 and the liquidus temperature T 液 .

[0030] Preferably, the method for simulating the solidification process of the target ingot by using the PROCAST software comprises:

[0031] a model with the same volume as the target ingot and the mold is constructed, the mold material in the model is set as cast iron, the interface heat exchange coefficient h is set as the boundary condition of the ingot and the mold in the model, the enthalpy value, the density value and the solidus temperature point T 固 are set as the material parameters of the ingot in the model; the heat exchange condition of the mold and air in the model is set as air cooling, the air temperature is set as 20℃, and the pouring temperature is set as the liquidus temperature T 液 +(50-60)℃.

[0032] The application further provides application of the determination method in the preparation of the austenitic stainless steel ingot.

[0033] The application further provides a preparation method of the austenitic stainless steel ingot, comprising the following steps:

[0034] The stainless steel raw material is sequentially subjected to melting, deoxidation treatment and nitriding treatment, and the obtained molten steel is subjected to casting and solidification under a solidification pressure to obtain the austenitic stainless steel ingot.

[0035] The solidification pressure is the lowest value of the solidification pressure for inhibiting porosity obtained by the determination method.

[0036] Preferably, the austenitic stainless steel ingot comprises the following components in mass percentage: C≤0.2%, N: 0.4-1.2%, Mn: 13-20%, Cr: 15-22%, Si≤1%, Mo: 0-4.5%, Ni: 0-25%, and the balance is Fe.

[0037] Preferably, the deoxidizing agent used in the deoxidation treatment comprises electrolytic aluminum and nickel-magnesium alloy.

[0038] Preferably, the temperature of the melting is liquidus temperature T 液 +(60-80)℃, and the pressure is 4-10 Pa.

[0039] Preferably, the nitriding treatment is gas nitriding treatment.

[0040] The pressure of the gas nitriding treatment is 0.4-1.0 MPa, and the pressure holding time is 10-20 min.

[0041] Preferably, the temperature of the casting is liquidus temperature T 液 +(50-60)℃.

[0042] The application provides a determination method of the lowest value of the solidification pressure for inhibiting porosity, comprising the following steps: according to the solidification time and the solidification pressure set value P 设 of a target ingot, determining the interface heat transfer coefficient h between the target ingot and a mold by formula 1; according to the composition of the target ingot, calculating the enthalpy value change rate with temperature and the density value change rate with temperature in the solidification process of the target ingot by using the scheil solidification model in the Thermo-Calc thermodynamic calculation software; according to the interface heat transfer coefficient h, the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T 固 , simulating the solidification process of the target ingot by using the PROCAST software; within the range of T 固 ±1℃, extracting a plurality of data points of the temperature change with position in the core of the target ingot, and determining the temperature gradient G of the core of the target ingot according to formula 2.r ; in T 固 Within the range of ±1°C, several data points of the target ingot core temperature change over time are extracted and fitted to obtain the temperature-time relationship linear equation. The slope of the linear equation is the cooling rate v c According to formula 3, the calculated value of solidification pressure P is obtained. s When P s ≤P 设 When the solidification pressure is set to P 设 As the lowest value of solidification pressure; when P s >P 设 When the solidification pressure setting value P is increased 设 Repeat the above to get the calculated value of solidification pressure P s The process until the P s ≤P 设 The method provided by the present invention does not require multiple repeated tests in actual production, and the minimum value of the solidification pressure required to inhibit porosity can be determined by simulating the solidification process of the ingot. The method is accurate and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Graph showing the change in heat transfer coefficient versus time when the solidification pressure setting value is 0.4 MPa in Example 1;

[0044] Figure 2 The enthalpy value obtained when the solidification pressure setting value is 0.4 MPa in Example 1 is a curve diagram of the change with temperature

[0045] Figure 3 This is a curve diagram of density values ​​versus temperature obtained when the solidification pressure setting value is 0.4 MPa in Example 1;

[0046] Figure 4 Graph showing the change in heat transfer coefficient versus time when the solidification pressure setting value is 0.6 MPa in Example 1;

[0047] Figure 5 1 is a curve diagram showing the change of enthalpy value with temperature when the solidification pressure setting value is 0.6 MPa in Example 1;

[0048] Figure 6 This is a curve diagram of density values ​​versus temperature obtained when the solidification pressure setting value is 0.6 MPa in Example 1;

[0049] Figure 7 This is a physical picture of the austenitic stainless steel ingot obtained in verification test 1;

[0050] Figure 8 This is a physical picture of the austenitic stainless steel ingot obtained in verification test 2;

[0051] Figure 9 The figure is a flow chart of the determination method provided by the present invention. DETAILED DESCRIPTION

[0052] The present invention provides a method for determining a minimum value of solidification pressure for inhibiting porosity, comprising the following steps:

[0053] Set the value P according to the target ingot solidification time and solidification pressure 设 , use Equation 1 to determine the interface heat transfer coefficient h between the target ingot and the mold;

[0054] According to the composition of the target ingot, the scheil solidification model in the Thermo-Calc thermodynamic calculation software is used to calculate the enthalpy value change rate with temperature and the density value change rate with temperature of the target ingot during the solidification process;

[0055] Determine the solidus temperature point T of the target ingot 固 and liquidus temperature point T 液 ;

[0056] According to the interface heat transfer coefficient h, the enthalpy value with temperature change rate, the density value with temperature change rate and the solidus temperature point T 固 , PROCAST software was used to simulate the solidification process of the target ingot;

[0057] In T 固 Within the range of ±1°C, extract several data points of target ingot core temperature changes with position, and determine the target ingot core temperature gradient G according to formula 2. r ;

[0058] In T 固 Within the range of ±1°C, several data points of the target ingot core temperature change over time are extracted and fitted to obtain the temperature-time relationship linear equation. The slope of the linear equation is the cooling rate v c ;

[0059] According to formula 3, the calculated value of solidification pressure P is obtained. s ;

[0060] When P s ≤P 设 When the solidification pressure is set to P 设 As the lowest value of solidification pressure;

[0061] When P s >P 设 When the solidification pressure setting value P is increased 设 Repeat the above to get the calculated value of solidification pressure P s The process until the P s ≤P 设;

[0062]

[0063]

[0064]

[0065] wherein P 设 is a solidification pressure set value, in MPa; the solidification pressure set value P 设 is in the range of > 0.1 MPa;

[0066] h is an interface heat exchange coefficient, in w·m -2 ·℃ -1 ;

[0067] t is a solidification time, in s;

[0068] G r is a temperature gradient, in ℃ / m;

[0069] v c is a cooling rate, in ℃ / s;

[0070] f L is a liquid phase volume fraction between dendrites, in the range of 0.8-0.9;

[0071] P s is a solidification pressure calculation value, in MPa.

[0072] A flowchart of the determination method provided by the application is shown in Figure 9 .

[0073] In the application, the initial input value of P 设 is preferably 0.4 MPa.

[0074] In the application, the method for determining the solidus temperature point T 固 and the liquidus temperature T 液 preferably comprises the following steps:

[0075] A vertical through-hole penetrating the side wall of the mold is punched at a position of half the vertical height of the outer wall of the cylindrical mold, the diameter of the through-hole is 8 mm; a thermocouple is placed in the through-hole, the temperature measuring point of the thermocouple is 10 mm away from the radial direction of the inner wall of the cylindrical mold;

[0076] The temperature change curve of the molten steel in the solidification process measured by the thermocouple is recorded, and the temperature change curve is differentiated to obtain the solidus temperature point T 固 and the liquidus temperature T 液 .

[0077] In the present application, the simulation of the solidification process of the target ingot by the PROCAST software preferably comprises:

[0078] A model with the same volume as the target ingot and the mold is constructed, the mold material in the model is set as cast iron, the interfacial heat exchange coefficient h is taken as the boundary condition of the ingot and the mold in the model, and the enthalpy variation rate with temperature, the density variation rate with temperature and the solidus temperature point T 固 as the material parameters of the ingot in the model; the heat exchange condition of the mold and air in the model is set as air cooling, the air temperature is set as 20℃, and the pouring temperature is set as the liquidus temperature T 液 +(50-60)℃.

[0079] In the present application, the temperature gradient G r is the temperature variation rate in the normal direction of the isothermal surface of the center part of the ingot.

[0080] In the present application, when the solidification pressure set value P 设 is increased, preferably by 0.1MPa each time.

[0081] The present application also provides the application of the determination method in the preparation of the austenitic stainless steel ingot. The lowest value of the solidification pressure for suppressing porosity is obtained according to the above technical solution, and the pouring and solidification are carried out under the condition of the lowest value of the solidification pressure.

[0082] The present application also provides a preparation method of an austenitic stainless steel ingot, comprising the following steps:

[0083] melting, deoxidizing treatment and nitriding treatment to obtain the austenitic stainless steel ingot;

[0084] The solidification pressure is the lowest value of the solidification pressure for suppressing porosity obtained by the determination method.

[0085] In the present application, the austenitic stainless steel ingot preferably comprises the following components with mass percentage: C≤0.2%, N: 0.4-1.2%, Mn: 13-20%, Cr: 15-22%, Si≤1%, Mo: 0-4.5%, Ni: 0-25%, and the balance is Fe.

[0086] In the present application, the stainless steel raw material preferably comprises graphite, industrial silicon, industrial pure iron, metallic chromium, metallic molybdenum, metallic nickel and metallic manganese. In the present application, all raw materials are commercially available products well known to those skilled in the art unless otherwise specified.

[0087] In the present application, the components of each component in the raw material are shown in Table 1.

[0088] Table 1 Components of each component in the raw material (wt%)

[0089]

[0090]

[0091] In the present application, the temperature of the melting is preferably the liquidus temperature T 液 +(60-80)℃; the pressure is preferably 4-10 Pa, further preferably 5-9 Pa, and more preferably 6-8 Pa. In the present application, the melting is preferably carried out under vacuum.

[0092] In the present application, the deoxidizing agent used in the deoxidizing treatment preferably includes electrolytic aluminum and a nickel-magnesium alloy. In the present application, the mass of the electrolytic aluminum is preferably 0.06 wt% of the mass of the austenitic stainless steel ingot; and the mass of the nickel-magnesium alloy is preferably 0.1 wt% of the mass of the austenitic stainless steel ingot. In the present application, the deoxidizing treatment is preferably carried out in an argon atmosphere.

[0093] In the present application, the nitriding treatment is preferably a gas nitriding treatment; the pressure of the gas nitriding treatment is preferably 0.4-1.0 MPa, further preferably 0.5-0.9, and more preferably 0.6-0.8; and the pressure holding time is preferably 10-20 min, further preferably 12-18 min, and more preferably 13-15 min.

[0094] In the present application, the melting, the deoxidizing treatment, and the nitriding treatment are all carried out in a pressurized induction furnace.

[0095] In a specific embodiment of the present application, the process of the melting, the deoxidizing treatment, and the nitriding treatment is preferably as follows:

[0096] The industrial pure iron, the metal chromium, the metal molybdenum, and the metal manganese are added to a crucible of the pressurized induction furnace, and the graphite, the industrial silicon, and the deoxidizing agent are added to a charging bin of the pressurized induction furnace;

[0097] The pressurized induction furnace is sealed and vacuumized, and the raw material in the crucible is heated and melted by electrification to obtain a molten liquid;

[0098] Argon is introduced into the pressurized induction furnace, and the raw material in the charging bin is added to the molten liquid to carry out a deoxidizing treatment, thereby obtaining a deoxidized molten liquid;

[0099] Nitrogen is introduced into the pressurized induction furnace, and the deoxidized molten liquid is subjected to a gas nitriding treatment to obtain a steel liquid.

[0100] In the embodiment of the present application, the rated charging capacity of the pressurized induction furnace is 25 kg, and the actual charging capacity is 20 kg; the rated power of the power supply of the pressurized induction furnace is 50 kW; the limit vacuum degree of the pressurized induction furnace is 0.1 Pa, and the highest bearing pressure is 6 MPa.

[0101] In the present application, the temperature of the casting is preferably the liquidus temperature T 液 +(50-60)℃. The present application does not have special limitation on the time of the casting and solidification, and the time known by those skilled in the art can be used. In the present application, the casting and solidification are both carried out at the lowest solidification pressure. In the present application, the casting and solidification are carried out in an argon atmosphere. In the present application, the casting and solidification are carried out in a pressurized induction furnace.

[0102] In the embodiment of the present application, the process of the casting and solidification is preferably as follows:

[0103] The argon is introduced into the pressurized induction furnace to the lowest solidification pressure, and the molten steel is sequentially casted and solidified.

[0104] After the solidification is completed, the present application further preferably includes the processes of degassing the pressurized induction furnace and cooling the obtained product to room temperature. The present application does not have special limitation on the processes of degassing and cooling, and the processes known by those skilled in the art can be used.

[0105] In order to further illustrate the present application, one kind of determination method of the lowest solidification pressure of the loose inhibition and its application, and one kind of preparation method of the austenitic stainless steel ingot are described in detail below in combination with the drawings and the embodiments, but they cannot be understood as the limitation on the protection scope of the present application.

[0106] Example 1

[0107] In this embodiment, the austenitic stainless steel ingot is 19Cr14Mn4Mo, and the target composition is shown in Table 2.

[0108] Table 2 Composition control range and control target of the austenitic stainless steel ingot

[0109]

[0110] The solidification pressure setting value is taken as 0.4 MPa, the interfacial heat transfer coefficient h between the target ingot and the mold is determined according to formula 1, h = 651.77t -0.12 , and the obtained heat transfer coefficient and time change curve is shown in Figure 1 ;

[0111] According to the composition of the target ingot, the enthalpy rate of change with temperature and the density rate of change with temperature of the target ingot during solidification are calculated using the Scheil solidification model in the Thermo-Calc thermodynamic calculation software, wherein the enthalpy rate of change with temperature is as shown in Figure 2 , and the density rate of change with temperature is as shown in Figure 3 ;

[0112] The temperature change curve of the molten steel during solidification is recorded by the thermocouple, and the solidus temperature T 固 of the target ingot is obtained by differentiating the cooling curve, and the liquidus temperature T 液 is 1390℃;

[0113] The solidification process of the target ingot is simulated by using the PROCAST software: a model with the same volume as the target ingot and the mold is constructed, the mold material in the model is set as cast iron, the obtained interfacial heat transfer coefficient h is taken as the boundary condition of the ingot and the mold in the model, the obtained enthalpy rate of change with temperature, the density rate of change with temperature and the solidus temperature T 固 are taken as the material parameters of the ingot in the model; the heat transfer conditions of the mold and the air in the model are set as air cooling, the air temperature is set as 20℃, and the pouring temperature is set as 1450℃;

[0114] In the range of T 固 ±1℃, several data points of the temperature change with position of the core of the target ingot are extracted, and the temperature gradient G r of the core of the target ingot is calculated according to formula 2, and the temperature gradient G r is 24℃ / m;

[0115] In the range of T 固 ±1℃, several data points of the temperature change with time of the core of the target ingot are extracted, and the temperature-time relationship linear equation is fitted, and the cooling rate v c is calculated according to the slope of the linear equation, and the cooling rate v c is 4.524℃ / s;

[0116] The obtained temperature gradient G r and the cooling rate v c are substituted into formula 3 to obtain the calculated value P s of the solidification pressure, and the calculated value P s of the solidification pressure is greater than 0.51MPa;

[0117] The calculated value P s of the solidification pressure is greater than the set value P 设 of the solidification pressure, and the set value of the solidification pressure is reselected as 0.6MPa;

[0118] The above process is repeated, the interfacial heat transfer absorption h obtained according to formula 1 is h=704.53t -0.12 , and the change curve of the heat transfer coefficient and time is as shown in Figure 4The enthalpy rate of change with temperature and the density rate of change with temperature of the target ingot during solidification process were calculated using Scheil solidification model in Thermo-Calc thermodynamic calculation software, wherein the enthalpy rate of change with temperature is as shown in Figure 5 the density rate of change with temperature is as shown in Figure 6 ;

[0119] The solidus temperature point T 固 of the target ingot during solidification simulation process was determined to be 1336℃, and the liquidus temperature T 液 was determined to be 1390℃; the temperature gradient G r calculated by simulation was 24.3℃ / m, the cooling rate v c was 4.925℃ / s, and the calculated solidification pressure P s was greater than 0.55MPa.

[0120] The calculated solidification pressure P s was less than the solidification pressure setting value P 设 , and the solidification pressure setting value of 0.6MPa was taken as the minimum solidification pressure required for inhibiting porosity in the process of preparing the austenitic stainless steel ingot 19Cr14Mn4Mo.

[0121] Verification Test 1

[0122] According to the target composition of the austenitic stainless steel ingot 19Cr14Mn4Mo, 12119.07g of elemental iron, 3831.80g of elemental chromium, 800.0g of elemental molybdenum and 3109.08g of elemental manganese were added to the crucible of the pressurized induction furnace, and 18.209g of graphite, 89.834g of elemental silicon, 12.0g of electrolytic aluminum and 20g of nickel-magnesium alloy were added to the charging bin of the pressurized induction furnace;

[0123] The pressurized induction furnace was sealed and vacuumized to 5Pa, and the raw materials in the crucible were heated to 1470℃ for melting by power supply, to obtain a molten liquid;

[0124] Argon was introduced into the pressurized induction furnace to 0.02MPa, and the raw materials in the charging bin were added to the molten liquid for deoxidation treatment, to obtain a deoxidized molten liquid;

[0125] Nitrogen was introduced into the pressurized induction furnace to a pressure of 0.4MPa, and the pressure was maintained for 20min, and the deoxidized molten liquid was subjected to gas nitriding treatment to obtain a steel liquid;

[0126] The casting was carried out at 1450℃ for 25s; the gas was released after solidification for 30min, and the obtained austenitic stainless steel ingot was cooled to room temperature;

[0127] The composition of the obtained austenitic stainless steel ingot is shown in Table 3;

[0128] Chemical composition of the obtained austenitic stainless steel ingot

[0129] C N Si Mn Cr Mo Fe Control target / wt% 0.1 0.91 0.49 14.53 19.02 3.81 Balance

[0130] The longitudinal section photograph of the obtained austenitic stainless steel ingot is shown in Fig. 2, from which it can be seen that the solidification structure of the austenitic stainless steel ingot prepared under the solidification pressure of 0.4 MPa is loose and has serious defects. Figure 7 Figure 7

[0131] Verification test 2

[0132] The test was carried out according to the method in verification test 1, in which argon was introduced to a solidification pressure of 0.6 MPa, to obtain an austenitic stainless steel ingot;

[0133] The composition of the obtained austenitic stainless steel ingot is shown in Table 4;

[0134] Chemical composition of the obtained austenitic stainless steel ingot

[0135] C N Si Mn Cr Mo Fe Control target / wt% 0.1 0.88 0.52 14.2 18.93 3.92 Balance

[0136] The longitudinal section photograph of the obtained austenitic stainless steel ingot is shown in Fig. 4, from which it can be seen that the solidification structure of the austenitic stainless steel ingot prepared under the solidification pressure of 0.6 MPa is dense and has no loose defects. Figure 8 Figure 8

[0137] Although the above embodiment has made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiment without creativity, which all belong to the protection scope of the present application.​​​​

Claims

1. A method of determining a minimum solidification pressure of a loose formation, characterized by, The method comprises the following steps: According to the solidification time of the target ingot and the solidification pressure set value P 设 , the interface heat exchange coefficient h between the target ingot and the mold is determined by formula 1; According to the composition of the target ingot, the rate of change of enthalpy and the rate of change of density of the target ingot with temperature during solidification are calculated using the Scheil solidification model in Thermo-Calc thermodynamic calculation software; determining a solidus temperature point T of the target ingot 固 and a liquidus temperature point T 液 ; According to the interface heat exchange coefficient h, the enthalpy value rate of change with temperature, the density value rate of change with temperature and the solidus temperature point T 固 The solidification process of the target ingot is simulated by using PROCAST software. In T 固 ±1℃, extract several target ingot core temperature with location variation data points, determine the temperature gradient G of the target ingot core according to formula 2 r ; In T 固 ±1℃, extract several target ingot core temperature with time varying data points, fitting to get temperature-time relationship linear equation, the slope of the linear equation is the cooling rate v c ; According to formula 3, the solidification pressure calculation value P is obtained s ; When P s ≤ P 设 , the coagulation pressure set value P 设 is set as the minimum value of the coagulation pressure. When P s > P 设 , the coagulation pressure set value P 设 is increased, the process of obtaining the coagulation pressure calculation value P s is repeated until P s ≤ P 设 ; wherein P 设 is a solidification pressure set value in MPa; the solidification pressure set value P 设 has a value in the range > 0.1 MPa; h is the interfacial heat transfer coefficient in w-m -2 • C -1 ; t is the solidification time, in seconds; G r G is the temperature gradient in °C / m; v c for the cooling rate, in °C / s; f L is the volume fraction of interdendritic liquid, and the value range is 0.8-0.9; P s The coagulation pressure is calculated as a value in MPa.

2. The determination method according to claim 1, characterized in that, said determining the solidus temperature point T 固 and the liquidus temperature T 液 comprises the following steps: A vertical through-hole is punched at the half height of the outer wall of the cylindrical mold, the diameter of the through-hole is 8mm, a thermocouple is placed in the through-hole, and the radial distance between the temperature measuring point of the thermocouple and the inner wall of the cylindrical mold is 10mm; The temperature change curve of the molten steel during solidification is recorded by a thermocouple. The solidus temperature T is obtained by differentiating the temperature change curve 固 and the liquidus temperature T 液 .

3. The determination method according to claim 1, characterized in that, The simulation of the solidification process of the target ingot using PROCAST software comprises: A model of the same volume as the target ingot and mold is constructed, the mold material in the model is set to cast iron, the interface heat exchange coefficient h is set as the boundary condition of the ingot and mold in the model, the enthalpy value temperature change rate, the density value temperature change rate and the solidus temperature point T 固 are set as the material parameters of the ingot in the model; the heat exchange condition of the mold and air in the model is set to air cooling, the air temperature is set to 20℃, and the pouring temperature is set to the liquidus temperature T 液 +(50-60)℃.

4. Use of the determination method according to any one of claims 1 to 3 in the preparation of an austenitic stainless steel ingot.

5. A method for preparing an austenitic stainless steel ingot, characterized in that: The method comprises the following steps: The raw material of stainless steel is sequentially subjected to melting, deoxidation treatment and nitriding treatment, the obtained molten steel is cast and solidified under a solidification pressure to obtain the austenitic stainless steel ingot; The solidification pressure is the lowest value of the solidification pressure obtained according to the determination method of any one of claims 1 to 3.

6. The preparation method according to claim 5, characterized in that The austenitic stainless steel ingot comprises the following components with mass percentage: C≤0.2%, N: 0.4-1.2%, Mn: 13-20%, Cr: 15-22%, Si≤1%, Mo: 0-4.5%, Ni: 0-25%, and the balance is Fe.

7. The preparation method according to claim 5, characterized in that The deoxidizer used in the deoxidation treatment comprises electrolytic aluminum and nickel-magnesium alloy.

8. The preparation method according to claim 5, characterized in that The temperature of the melting is the liquidus temperature T 液 + (60 to 80) °C, and the pressure is 4 to 10 Pa.

9. The preparation method according to claim 5, characterized in that The nitriding treatment is gas nitriding treatment; The pressure of the gas nitriding treatment is 0.4-1.0MPa, and the pressure holding time is 10-20min.

10. The method of claim 5, wherein, The temperature of the casting is the liquidus temperature T 液 + (50-60) °C.

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