CN116341207A - Determination method for minimum value of solidification pressure for inhibiting looseness, application of determination method and preparation method of austenitic stainless steel cast ingot - Google Patents

Determination method for minimum value of solidification pressure for inhibiting looseness, application of determination method and preparation method of austenitic stainless steel cast ingot Download PDF

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CN116341207A
CN116341207A CN202310159583.1A CN202310159583A CN116341207A CN 116341207 A CN116341207 A CN 116341207A CN 202310159583 A CN202310159583 A CN 202310159583A CN 116341207 A CN116341207 A CN 116341207A
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temperature
pressure
solidification
ingot
value
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李花兵
朱红春
倪卓文
姜周华
王宇
冯浩
张树才
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Dongda Industrial Technology Research Institute Liaoning Shenfu Reform And Innovation Demonstration Zone
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces

Abstract

The invention belongs to the technical field of alloys, and particularly relates to a determination method for a minimum value of solidification pressure for inhibiting looseness, application of the determination method and a preparation method of an austenitic stainless steel cast ingot. The method provided by the invention can determine the minimum value of the solidification pressure required for inhibiting the loose defect by simulating the solidification process of the cast ingot without repeated experiments in actual production, and is accurate and efficient.

Description

Determination method for minimum value of solidification pressure for inhibiting looseness, application of determination method and preparation method of austenitic stainless steel cast ingot
Technical Field
The invention belongs to the technical field of alloys, and particularly relates to a determination method for a minimum value of solidification pressure for inhibiting looseness, application of the determination method and a preparation method of an austenitic stainless steel cast ingot.
Background
Because austenitic stainless steel has excellent corrosion resistance and mechanical properties, the austenitic stainless steel is widely applied to the fields of aerospace, petrochemical industry, ships, medical instruments, energy and the like. Loose defects are easily formed during solidification of austenitic stainless steel ingots. Loose defects are difficult to eliminate by subsequent thermo-mechanical treatment processes, which in turn lead to severe effects on the mechanical properties of the final product and even to direct rejection of the material.
At present, a method for eliminating loose defects in cast ingots is generally to change feeding conditions by adding a heat-preserving riser, but the method has low utilization rate of raw materials, and waste of resources is caused; or by changing the height-to-diameter ratio or the height-to-width ratio of the cast ingot, in order to eliminate solidification defects such as segregation, inclusion and the like, the austenitic stainless steel cast ingot is generally subjected to the treatment of the follow-up processes such as electroslag remelting, vacuum consumable consumption and the like, and the change of the height-to-diameter ratio or the height-to-width ratio of the cast ingot can cause the follow-up processes to be unable to be carried out. These methods are therefore not suitable for preventing the occurrence of loose defects in austenitic stainless steel ingots.
In view of the above problems, prevention of the occurrence of loose defects in an austenitic stainless steel ingot can be achieved by applying a solidification pressure to the ingot. By applying a gas-phase solidification pressure during casting solidification, the heat exchange conditions between the ingot and the casting mold can be changed, and the formation of loose is inhibited. Therefore, the determination of the solidifying pressure value is the key for producing austenitic stainless steel ingots, the too low solidifying pressure can not effectively inhibit loose defects, the too high solidifying pressure can increase the production difficulty, the production cost is increased, and safety accidents are easy to cause. At present, the minimum solidification pressure can be determined only by repeated tests in the actual production process, which is time-consuming and labor-consuming.
Disclosure of Invention
The invention aims to provide a method for determining the minimum value of solidification pressure for inhibiting loosening, application of the method and a method for preparing an austenitic stainless steel cast ingot.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for determining the minimum value of solidification pressure for inhibiting loosening, which comprises the following steps:
according to the setting time and setting pressure P of the target ingot Is provided with Determining an interface heat exchange coefficient h between the target ingot and the casting mould by using a formula 1;
according to the composition of the target ingot, calculating to obtain the enthalpy value change rate and the density value change rate of the target ingot along with the temperature in the solidification process by using a scheil solidification model in Thermo-Calc thermodynamic calculation software;
determining solidus temperature point T of target ingot Fixing device And liquidus temperature point T Liquid and its preparation method ；
According to the interface heat exchange coefficient h, the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T Fixing device Simulating the solidification process of the target ingot by adopting PROCAST software;
at T Fixing device Within the range of +/-1 ℃, a plurality of data points of the temperature of the core part of the target ingot with the position change are extracted, and the temperature gradient G of the core part of the target ingot is determined according to the formula 2 r ；
At T Fixing device Extracting a plurality of data points of temperature change of the core of the target ingot with time within the range of +/-1 ℃, and fitting to obtain a temperature-time relation linear equation, wherein the slope of the linear equation is the cooling rate v c ；
Obtaining a calculated value P of the coagulation pressure according to 3 s ；
When P s ≤P Is provided with At the time, the setting value P of the solidification pressure is Is provided with As the minimum value of the setting pressure;
when P s ＞P Is provided with In the process, the setting value P of the solidification pressure is increased Is provided with Repeating the above steps to obtain the calculated value P of the solidification pressure s Up to the P s ≤P Is provided with ；
Figure BDA0004093656430000021
Figure BDA0004093656430000022
Figure BDA0004093656430000023
Wherein P is Is provided with Setting the setting value of the solidification pressure in MPa; the setting pressure is setConstant value P Is provided with The value range of (2) is more than 0.1MPa;
h is the interface heat exchange coefficient, and the unit is w.m -2 ·℃ -1 ；
t is the solidification time, and the unit is s;
G r is a temperature gradient, with the unit of ℃/m;
v c cooling rate in ℃/s;
f L the value range is 0.8-0.9 for the volume fraction of the liquid phase among dendrites;
P s the calculated value of the solidification pressure is expressed in MPa.
Preferably, the solidus temperature point T is determined Fixing device And liquidus temperature T Liquid and its preparation method The method of (1) comprises the following steps:
a through hole vertically penetrating through the side wall of the casting mold is drilled at a position which is half of the vertical height of the outer wall of the cylindrical casting mold, and the diameter of the through hole is 8mm; placing a thermocouple in the through hole, wherein the radial distance between a temperature measuring point of the thermocouple and the inner wall of the cylinder casting mold is 10mm;
recording the temperature change curve of molten steel measured by a thermocouple in the solidification process, and differentiating the temperature change curve to obtain the solidus temperature T Fixing device And liquidus temperature T Liquid and its preparation method 。
Preferably, the simulating the solidification process of the target ingot by using PROCAST software comprises:
constructing a model with the same volume as that of a target cast ingot and a casting mould, setting casting mould materials in the model to cast iron, taking the interface heat exchange coefficient h as boundary conditions of the cast ingot and the casting mould in the model, and taking the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T Fixing device As material parameters for the ingot in the model; the heat exchange condition of the casting mould and the air in the model is set as air cooling, the air temperature is set as 20 ℃, and the casting temperature is set as liquidus temperature T Liquid and its preparation method +(50～60)℃。
The invention also provides application of the determination method in preparing austenitic stainless steel ingots.
The invention also provides a preparation method of the austenitic stainless steel cast ingot, which comprises the following steps:
sequentially melting, deoxidizing and nitriding the stainless steel raw material, and casting and solidifying the obtained molten steel under solidification pressure to obtain the austenitic stainless steel cast ingot;
the solidification pressure is the lowest solidification pressure value for inhibiting loosening, which is obtained by the determination method according to the technical scheme.
Preferably, the austenitic stainless steel cast ingot comprises the following components in percentage by mass: c is less than or equal to 0.2 percent, N:0.4 to 1.2 percent, mn: 13-20%, cr: 15-22%, si less than or equal to 1%, mo:0 to 4.5 percent, ni: 0-25%, and the balance being Fe.
Preferably, the deoxidizing agent used in the deoxidizing treatment includes electrolytic aluminum and nickel-magnesium alloy.
Preferably, the melting temperature is the liquidus temperature T Liquid and its preparation method The temperature is plus (60-80) DEG C, and the pressure is 4-10 Pa.
Preferably, the nitriding treatment is gas nitriding treatment;
the pressure of the gas nitriding treatment is 0.4-1.0 MPa, and the pressure maintaining time is 10-20 min.
Preferably, the casting temperature is the liquidus temperature T Liquid and its preparation method +(50～60)℃。
The invention provides a method for determining the minimum value of solidification pressure for inhibiting loosening, which comprises the following steps: according to the setting time and setting pressure P of the target ingot Is provided with Determining an interface heat exchange coefficient h between the target ingot and the casting mould by using a formula 1; according to the composition of the target ingot, calculating to obtain the enthalpy value change rate and the density value change rate of the target ingot along with the temperature in the solidification process by using a scheil solidification model in Thermo-Calc thermodynamic calculation software; according to the interface heat exchange coefficient h, the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T Fixing device Simulating the solidification process of the target ingot by adopting PROCAST software; at T Fixing device Extracting a plurality of target cast ingot core temperatures along with the position change within the range of +/-1 DEG CDetermining the temperature gradient G of the core of the target ingot according to equation 2 r The method comprises the steps of carrying out a first treatment on the surface of the At T Fixing device Extracting a plurality of data points of temperature change of the core of the target ingot with time within the range of +/-1 ℃, and fitting to obtain a temperature-time relation linear equation, wherein the slope of the linear equation is the cooling rate v c The method comprises the steps of carrying out a first treatment on the surface of the Obtaining a calculated value P of the coagulation pressure according to 3 s The method comprises the steps of carrying out a first treatment on the surface of the When P s ≤P Is provided with At the time, the setting value P of the solidification pressure is Is provided with As the minimum value of the setting pressure; when P s ＞P Is provided with In the process, the setting value P of the solidification pressure is increased Is provided with Repeating the above steps to obtain the calculated value P of the solidification pressure s Up to the P s ≤P Is provided with . The method provided by the invention can determine the minimum value of the needed solidification pressure for inhibiting the looseness by simulating the solidification process of the cast ingot without carrying out repeated tests in actual production, and is accurate and efficient.
Drawings
FIG. 1 is a graph showing the change in heat exchange coefficient and time obtained when the setting value of the setting pressure was 0.4MPa in example 1;
FIG. 2 is a graph showing the change in enthalpy value with temperature obtained at a setting value of 0.4MPa in example 1
FIG. 3 is a graph showing the change in the density value with temperature obtained when the setting value of the setting pressure was 0.4MPa in example 1;
FIG. 4 is a graph showing the change in heat exchange coefficient and time obtained when the setting value of the setting pressure was 0.6MPa in example 1;
FIG. 5 is a graph showing the change in enthalpy value with temperature obtained when the setting value of the setting pressure was 0.6MPa in example 1;
FIG. 6 is a graph showing the change in the density value with temperature obtained when the setting value of the setting pressure was 0.6MPa in example 1;
FIG. 7 is a physical view of the austenitic stainless steel ingot obtained in the verification test 1;
FIG. 8 is a physical view of the austenitic stainless steel ingot obtained in validation test 2;
fig. 9 is a flow chart of a determining method provided by the invention.
Detailed Description
The invention provides a method for determining the minimum value of solidification pressure for inhibiting loosening, which comprises the following steps:
according to the setting time and setting pressure P of the target ingot Is provided with Determining an interface heat exchange coefficient h between the target ingot and the casting mould by using a formula 1;
according to the composition of the target ingot, calculating to obtain the enthalpy value change rate and the density value change rate of the target ingot along with the temperature in the solidification process by using a scheil solidification model in Thermo-Calc thermodynamic calculation software;
determining solidus temperature point T of target ingot Fixing device And liquidus temperature point T Liquid and its preparation method ；
According to the interface heat exchange coefficient h, the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T Fixing device Simulating the solidification process of the target ingot by adopting PROCAST software;
at T Fixing device Within the range of +/-1 ℃, a plurality of data points of the temperature of the core part of the target ingot with the position change are extracted, and the temperature gradient G of the core part of the target ingot is determined according to the formula 2 r ；
At T Fixing device Extracting a plurality of data points of temperature change of the core of the target ingot with time within the range of +/-1 ℃, and fitting to obtain a temperature-time relation linear equation, wherein the slope of the linear equation is the cooling rate v c ；
Obtaining a calculated value P of the coagulation pressure according to 3 s ；
When P s ≤P Is provided with At the time, the setting value P of the solidification pressure is Is provided with As the minimum value of the setting pressure;
when P s ＞P Is provided with In the process, the setting value P of the solidification pressure is increased Is provided with Repeating the above steps to obtain the calculated value P of the solidification pressure s Up to the P s ≤P Is provided with ；
Figure BDA0004093656430000051
Figure BDA0004093656430000061
Figure BDA0004093656430000062
Wherein P is Is provided with Setting the setting value of the solidification pressure in MPa; the setting pressure set point P Is provided with The value range of (2) is more than 0.1MPa;
h is the interface heat exchange coefficient, and the unit is w.m -2 ·℃ -1 ；
t is the solidification time, and the unit is s;
G r is a temperature gradient, with the unit of ℃/m;
v c cooling rate in ℃/s;
f L the value range is 0.8-0.9 for the volume fraction of the liquid phase among dendrites;
P s the calculated value of the solidification pressure is expressed in MPa.
The flow chart of the determination method provided by the invention is shown in fig. 9.
In the present invention, the P Is provided with Preferably 0.4MPa.
In the present invention, the solidus temperature point T is determined Fixing device And liquidus temperature T Liquid and its preparation method Preferably comprising the steps of:
a through hole vertically penetrating through the side wall of the casting mold is drilled at a position which is half of the vertical height of the outer wall of the cylindrical casting mold, and the diameter of the through hole is 8mm; placing a thermocouple in the through hole, wherein the radial distance between a temperature measuring point of the thermocouple and the inner wall of the cylinder casting mold is 10mm;
recording the temperature change curve of molten steel measured by a thermocouple in the solidification process, and differentiating the temperature change curve to obtain the solidus temperature point T Fixing device And liquidus temperature T Liquid and its preparation method 。
In the present invention, the simulation of the solidification process of the target ingot using PROCAST software preferably includes:
constructing a model with the same volume as that of a target cast ingot and a casting mould, setting casting mould materials in the model to cast iron, taking the interface heat exchange coefficient h as boundary conditions of the cast ingot and the casting mould in the model, and taking the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T Fixing device As material parameters for the ingot in the model; the heat exchange condition of the casting mould and the air in the model is set as air cooling, the air temperature is set as 20 ℃, and the casting temperature is set as liquidus temperature T Liquid and its preparation method +(50～60)℃。
In the present invention, the temperature gradient G r Is the temperature change rate in the normal direction of the isothermal surface of the central part of the ingot.
In the present invention, when the setting pressure set point P is increased Is provided with In the case of performing the repeated verification, it is preferable to increase the pressure by 0.1MPa each time.
The invention also provides application of the determination method in preparing austenitic stainless steel ingots. According to the technical scheme, the minimum value of the solidification pressure for inhibiting the looseness is obtained, and casting and solidification are carried out under the condition of the minimum value of the solidification pressure.
The invention also provides a preparation method of the austenitic stainless steel cast ingot, which comprises the following steps:
sequentially melting, deoxidizing and nitriding the stainless steel raw material, and casting and solidifying the obtained molten steel under solidification pressure to obtain the austenitic stainless steel cast ingot;
the solidification pressure is the lowest solidification pressure value for inhibiting loosening, which is obtained by the determination method according to the technical scheme.
In the invention, the austenitic stainless steel casting ingot preferably comprises the following components in percentage by mass: c is less than or equal to 0.2 percent, N:0.4 to 1.2 percent, mn: 13-20%, cr: 15-22%, si less than or equal to 1%, mo:0 to 4.5 percent, ni: 0-25%, and the balance being Fe.
In the present invention, the stainless steel raw material preferably includes graphite, industrial silicon, industrial pure iron, metallic chromium, metallic molybdenum, metallic nickel, and metallic manganese. In the present invention, all raw materials are commercially available products well known to those skilled in the art unless specified otherwise.
In the present invention, the ingredients of the respective components in the raw materials are shown in table 1;
TABLE 1 ingredients (wt%) of the respective components in the raw materials
Figure BDA0004093656430000071
Figure BDA0004093656430000081
In the present invention, the melting temperature is preferably the liquidus temperature T Liquid and its preparation method ++ (60-80) DEG C; the pressure is preferably 4 to 10Pa, more preferably 5 to 9Pa, and still more preferably 6 to 8Pa. In the present invention, the melting is preferably performed under vacuum.
In the present invention, the deoxidizer used in the deoxidizing treatment preferably includes electrolytic aluminum and nickel-magnesium alloy. In the present invention, the mass of the electrolytic aluminum is preferably 0.06wt% of the mass of the austenitic stainless steel ingot; the mass of the nickel-magnesium alloy is preferably 0.1wt% of the mass of the austenitic stainless steel ingot. In the present invention, the deoxidization treatment is preferably performed in an argon atmosphere.
In the present invention, the nitriding treatment is preferably a gas nitriding treatment; the pressure of the gas nitriding treatment is preferably 0.4 to 1.0MPa, more preferably 0.5 to 0.9, still more preferably 0.6 to 0.8; the dwell time is preferably 10 to 20 minutes, more preferably 12 to 18 minutes, and still more preferably 13 to 15 minutes.
In the invention, the melting, deoxidizing treatment and nitriding treatment are all performed in a pressurized induction furnace.
In a specific embodiment of the present invention, the melting, deoxidizing and nitriding processes are preferably:
adding industrial pure iron, metallic chromium, metallic molybdenum and metallic manganese into a crucible of a pressurized induction furnace, and adding graphite, industrial silicon and deoxidizer into a charging bin of the pressurized induction furnace;
sealing and vacuumizing a pressurized induction furnace, and electrifying to heat and melt raw materials in the crucible to obtain a melt;
introducing argon into the pressurized induction furnace, adding raw materials in a feeding bin into the molten liquid, and carrying out deoxidization treatment to obtain deoxidized molten liquid;
and (3) introducing nitrogen into the pressurized induction furnace, and carrying out gas nitriding treatment on the deoxidized molten liquid to obtain molten steel.
In the specific embodiment of the invention, the rated charging capacity of the pressurizing induction furnace is 25kg, and the actual charging capacity is 20kg; the rated power of the power supply of the pressurizing induction furnace is 50kW; the ultimate vacuum degree of the pressurizing induction furnace is 0.1Pa, and the highest bearing pressure is 6MPa.
In the present invention, the casting temperature is preferably the liquidus temperature T Liquid and its preparation method ++ (50-60) deg.C. The time for casting and solidification is not particularly limited in the present invention, and may be known to those skilled in the art. In the present invention, the casting and solidification are both performed at the minimum value of the solidification pressure. In the present invention, the casting and solidification are performed in an argon atmosphere. In the present invention, the casting and solidification are performed in a pressurized induction furnace.
In a specific embodiment of the present invention, the casting and solidification process is preferably:
argon is introduced into the pressurizing induction furnace until the solidification pressure is the lowest, and the molten steel is cast and solidified in sequence.
After the solidification is completed, the present invention also preferably includes deflating the pressurized induction furnace and cooling the resulting product to room temperature. The process of the present invention for the air release and cooling is not particularly limited, and may be performed by a process well known to those skilled in the art.
For further explanation of the present invention, a method for determining the minimum value of solidification pressure for suppressing porosity, application thereof, and a method for producing an austenitic stainless steel ingot, which are provided by the present invention, will be described in detail with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of the present invention.
Example 1
In the embodiment, the austenitic stainless steel cast ingot is 19Cr14Mn4Mo, and the target components are shown in Table 2;
TABLE 2 composition control Range and control targets for Austenitic stainless Steel cast ingots
Figure BDA0004093656430000091
Setting the setting value of the solidification pressure to be 0.4MPa, and determining the interface heat exchange coefficient h= 651.77t between the target ingot and the casting mould according to the method 1 -0.12 The obtained change curve graph of the heat exchange coefficient and time is shown in figure 1;
according to the composition of the target ingot, calculating to obtain the change rate of the enthalpy value and the change rate of the density value of the target ingot along with the temperature in the solidification process by using a scheil solidification model in Thermo-Calc thermodynamic calculation software, wherein the change rate of the enthalpy value along with the temperature is shown in a graph 2, and the change rate of the density value along with the temperature is shown in a graph 3;
recording a temperature change curve measured by a thermocouple in the solidification process of molten steel, and differentiating the cooling curve to obtain the solidus temperature T of the target ingot Fixing device At 1336℃and liquidus temperature T Liquid and its preparation method 1390 ℃;
and simulating the solidification process of the target ingot by adopting PROCAST software: constructing a model with the same volume as that of a target cast ingot and a casting mould, setting casting mould materials in the model to cast iron, taking an obtained interface heat exchange coefficient h as boundary conditions of the cast ingot and the casting mould in the model, and obtaining enthalpy values according to the temperature change rate, the density values according to the temperature change rate and the solidus temperature T Fixing device As material parameters for the ingot in the model; the heat exchange condition of the casting mould and air in the model is set as air cooling, the air temperature is set as 20 ℃, and the casting temperature is set as 1450 ℃;
at T Fixing device Extracting a plurality of data points of the temperature of the core part of the target ingot with the position change and the root within the range of +/-1 DEG CCalculating the temperature gradient G of the core of the target ingot according to the method 2 r 24 ℃/m;
at T Fixing device Extracting a plurality of data points of temperature change of the core of the target ingot with time within the range of +/-1 ℃, fitting to obtain a temperature-time relation linear equation, and obtaining the cooling rate v according to the slope of the linear equation c 4.524 ℃/s;
the resulting temperature gradient G r And cooling rate v c Substituting into 3 to obtain the calculated value P of the solidification pressure s ≥0.51MPa；
The obtained calculated value P of the solidification pressure s Greater than the setting pressure P Is provided with Re-selecting the setting value of the solidification pressure to be 0.6MPa;
repeating the above process to obtain interface heat exchange absorption of h= 704.53t according to formula 1 -0.12 The obtained change curve graph of the heat exchange coefficient and time is shown in figure 4; calculating to obtain the change rate of the enthalpy value and the change rate of the density value of the target ingot casting with temperature in the solidification process by using a scheil solidification model in Thermo-Calc thermodynamic calculation software, wherein the change rate of the enthalpy value with temperature is shown in figure 5, and the change rate of the density value with temperature is shown in figure 6;
determining solidus temperature point T of target ingot in solidification simulation process Fixing device At 1336℃and liquidus temperature T Liquid and its preparation method 1390 ℃; the temperature gradient G obtained by simulation calculation r At a cooling rate v of 24.3 ℃/m c Is 4.925 ℃/s, and is substituted into 3 to obtain the calculated value P of the solidification pressure s ≥0.55MPa；
The obtained calculated value P of the solidification pressure s Less than the setting pressure P Is provided with The setting value of the solidification pressure is 0.6MPa, which is the minimum value of the solidification pressure required for inhibiting the loosening in the process of preparing the austenitic stainless steel casting ingot 19Cr14Mn4 Mo.
Verification test 1
According to target components of the austenitic stainless steel cast ingot 19Cr14Mn4Mo, adding 12119.07 simple substance iron, 3831.80g simple substance chromium, 800.0g simple substance molybdenum and 3109.08g simple substance manganese into a crucible of a pressurizing induction furnace, and adding 18.209g graphite, 89.834g simple substance silicon, 12.0g electrolytic aluminum and 20g nickel-magnesium alloy into a charging bin of the pressurizing induction furnace;
sealing and vacuumizing the pressurizing induction furnace to 5Pa, and electrifying to heat raw materials in the crucible to 1470 ℃ for melting to obtain a molten liquid;
introducing argon into the pressurized induction furnace to 0.02MPa, adding raw materials in a feeding bin into the molten liquid, and carrying out deoxidization treatment to obtain deoxidized molten liquid;
introducing nitrogen into the pressurizing induction furnace until the pressure is 0.4MPa, maintaining the pressure for 20min, and performing gas nitriding treatment on the deoxidized molten liquid to obtain molten steel;
casting at 1450 ℃ for 25s; solidifying for 30min, discharging air, and cooling to room temperature to obtain an austenitic stainless steel cast ingot;
the composition of the resulting austenitic stainless steel ingot is shown in table 3;
table 3 chemical composition of austenitic stainless steel ingot obtained
C N Si Mn Cr Mo Fe
Control objective/wt% 0.1 0.91 0.49 14.53 19.02 3.81 Allowance of
As can be seen from FIG. 7, the austenitic stainless steel ingot prepared under a solidification pressure of 0.4MPa has serious defects in loose solidification structure.
Verification test 2
Performing a test according to the method in the verification test 1, wherein argon is introduced until the solidification pressure is 0.6MPa, so as to obtain an austenitic stainless steel cast ingot;
the composition of the resulting austenitic stainless steel ingot is shown in table 4;
table 4 chemical composition of austenitic stainless steel ingot obtained
C N Si Mn Cr Mo Fe
Control objective/wt% 0.1 0.88 0.52 14.2 18.93 3.92 Allowance of
The obtained austenitic stainless steel ingot is shown in a longitudinal section physical diagram in fig. 8, and as can be seen from fig. 8, the solidification structure of the austenitic stainless steel ingot prepared under the solidification pressure of 0.6MPa is compact and has no looseness.
Although the foregoing embodiments have been described in some, but not all embodiments of the invention, other embodiments may be obtained according to the present embodiments without departing from the scope of the invention.

Claims (10)

1. A method of determining a minimum value of a coagulation pressure for inhibiting loosening, comprising the steps of:
according to the setting time and setting pressure P of the target ingot Is provided with Determining an interface heat exchange coefficient h between the target ingot and the casting mould by using a formula 1;
according to the composition of the target ingot, calculating to obtain the enthalpy value change rate and the density value change rate of the target ingot along with the temperature in the solidification process by using a scheil solidification model in Thermo-Calc thermodynamic calculation software;
determining solidus temperature point T of target ingot Fixing device And liquidus temperature point T Liquid and its preparation method ；
Heat exchange according to the interfaceCoefficient h, the enthalpy value rate of change with temperature, the density value rate of change with temperature and solidus temperature point T Fixing device Simulating the solidification process of the target ingot by adopting PROCAST software;
at T Fixing device Within the range of +/-1 ℃, a plurality of data points of the temperature of the core part of the target ingot with the position change are extracted, and the temperature gradient G of the core part of the target ingot is determined according to the formula 2 r ；
At T Fixing device Extracting a plurality of data points of temperature change of the core of the target ingot with time within the range of +/-1 ℃, and fitting to obtain a temperature-time relation linear equation, wherein the slope of the linear equation is the cooling rate v c ；
Obtaining a calculated value P of the coagulation pressure according to 3 s ；
When P s ≤P Is provided with At the time, the setting value P of the solidification pressure is Is provided with As the minimum value of the setting pressure;
when P s ＞P Is provided with In the process, the setting value P of the solidification pressure is increased Is provided with Repeating the above steps to obtain the calculated value P of the solidification pressure s Up to the P s ≤P Is provided with ；
Figure FDA0004093656420000011
Figure FDA0004093656420000012
Figure FDA0004093656420000013
Wherein P is Is provided with Setting the setting value of the solidification pressure in MPa; the setting pressure set point P Is provided with The value range of (2) is more than 0.1MPa;
h is the interface heat exchange coefficient, and the unit is w.m -2 ·℃ -1 ；
t is the solidification time, and the unit is s;
G r is a temperature gradient, with the unit of ℃/m;
v c cooling rate in ℃/s;
f L the value range is 0.8-0.9 for the volume fraction of the liquid phase among dendrites;
P s the calculated value of the solidification pressure is expressed in MPa.
2. The method according to claim 1, wherein the solidus temperature point T is determined Fixing device And liquidus temperature T Liquid and its preparation method The method of (1) comprises the following steps:
a through hole vertically penetrating through the side wall of the casting mold is drilled at a position which is half of the vertical height of the outer wall of the cylindrical casting mold, and the diameter of the through hole is 8mm; placing a thermocouple in the through hole, wherein the radial distance between a temperature measuring point of the thermocouple and the inner wall of the cylinder casting mold is 10mm;
recording the temperature change curve of molten steel measured by a thermocouple in the solidification process, and differentiating the temperature change curve to obtain the solidus temperature T Fixing device And liquidus temperature T Liquid and its preparation method 。
3. The method of determining according to claim 1, wherein simulating the solidification process of the target ingot using PROCAST software comprises:
constructing a model with the same volume as that of a target cast ingot and a casting mould, setting casting mould materials in the model to cast iron, taking the interface heat exchange coefficient h as boundary conditions of the cast ingot and the casting mould in the model, and taking the enthalpy value change rate with temperature, the density value change rate with temperature and the solidus temperature point T Fixing device As material parameters for the ingot in the model; the heat exchange condition of the casting mould and the air in the model is set as air cooling, the air temperature is set as 20 ℃, and the casting temperature is set as liquidus temperature T Liquid and its preparation method +(50～60)℃。
4. Use of the defined method of any one of claims 1-3 for the preparation of austenitic stainless steel ingots.
5. The preparation method of the austenitic stainless steel cast ingot is characterized by comprising the following steps of:
sequentially melting, deoxidizing and nitriding the stainless steel raw material, and casting and solidifying the obtained molten steel under solidification pressure to obtain the austenitic stainless steel cast ingot;
the setting pressure is the lowest setting pressure value obtained by the determination method according to any one of claims 1 to 3.
6. The method of claim 5, wherein the austenitic stainless steel ingot comprises the following components in percentage by mass: c is less than or equal to 0.2 percent, N:0.4 to 1.2 percent, mn: 13-20%, cr: 15-22%, si less than or equal to 1%, mo:0 to 4.5 percent, ni: 0-25%, and the balance being Fe.
7. The method according to claim 5, wherein the deoxidizing agent used in the deoxidizing treatment comprises electrolytic aluminum and nickel-magnesium alloy.
8. The method according to claim 5, wherein the melting temperature is the liquidus temperature T Liquid and its preparation method The temperature is plus (60-80) DEG C, and the pressure is 4-10 Pa.
9. The method according to claim 5, wherein the nitriding treatment is gas nitriding treatment;
the pressure of the gas nitriding treatment is 0.4-1.0 MPa, and the pressure maintaining time is 10-20 min.
10. The method according to claim 5, wherein the casting temperature is liquidus temperature T Liquid and its preparation method +(50～60)℃。
CN202310159583.1A 2023-02-24 2023-02-24 Determination method for minimum value of solidification pressure for inhibiting looseness, application of determination method and preparation method of austenitic stainless steel cast ingot Pending CN116341207A (en)

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