CN114410923A - Full solid solution and multiple variable temperature alternate aging composite heat treatment method starting from low temperature - Google Patents
Full solid solution and multiple variable temperature alternate aging composite heat treatment method starting from low temperature Download PDFInfo
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- C21D6/00—Heat treatment of ferrous alloys
- C21D6/02—Hardening by precipitation
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/78—Combined heat-treatments not provided for above
- C21D1/785—Thermocycling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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Abstract
The invention provides a compound heat treatment method for full solid solution and multiple variable temperature alternate aging starting from low temperature. The method comprises the following steps: the full solid solution heat treatment process and the full start of the low-temperature multiple temperature-changing alternating aging composite heat treatment process. The scheme of the invention can solve the problems of poor quality stability, low qualified product rate, low hardness, low mechanical property, poor consistency, long heating time, low efficiency, poor heating reliability of heat treatment equipment, low service life of high-temperature components and high cost of 'one-long-one-high-three-difference-five-low' specific heat treatment technology theory and practice of austenitic stainless steel solid solution and aging heat treatment.
Description
Technical Field
The invention relates to the technical field of material heat treatment, in particular to a composite heat treatment method for fully dissolving solid solution and starting from low temperature for multiple times of temperature change and alternating aging.
Background
The heat treatment principle of austenitic stainless steel (see GB/T1220, GB/T1221, GB/T12773 and the like) is quite different from that of structural alloy steel (see GB/T3077 and the like): the alloy structural steel can generate high-temperature austenite structure transformation under the high-temperature condition, so that the alloy structural steel is very easy to greatly improve the hardness (or mechanical property) of the material by quenching and tempering heat treatment methods; however, austenitic stainless steel cannot generate high-temperature austenitic structure transformation (only can an alloying element strengthening phase be dissolved and precipitated) under high-temperature conditions, so that the austenitic stainless steel is extremely difficult to greatly improve the hardness (or mechanical property) of the material by a solid solution and aging heat treatment method.
The meaning of solution heat treatment is: heating austenitic stainless steel to a certain temperature and keeping the temperature, fully dissolving the excess phase, then rapidly cooling to obtain a supersaturated solid solution, obtaining a supersaturated reinforced solid solution, preparing a structure for precipitation hardening treatment, eliminating stress and carrying out work hardening between forming procedures; the meaning of the aging heat treatment is: after the workpiece is subjected to solution treatment, the workpiece is kept at room temperature or over room temperature, a solute atom segregation area is formed in a supersaturated solid solution, and/or a heat treatment process is carried out, wherein the second phase particles are precipitated, dispersed, distributed and excessive, and are precipitated, so that the material is hardened.
The main strengthening phase of austenitic stainless steel is alloy carbide, and the weakening term is intermetallic compound (such as Fe)2W、Fe2Mo, CuO, FeS, FeO, MnS, etc.); strengthening of different materials even of the same metal elementThe type, amount, size, shape, distribution, melting point, brittleness, hardness and the like of the phases are different according to the adopted solid solution and aging heat treatment methods, and the more the alloy elements are, the larger the difference is.
The relative stability of carbides formed by alloy elements such as nickel, chromium, tungsten, molybdenum, vanadium, titanium, aluminum, niobium and the like in steel is arranged from high to low in the sequence: hf, Zr, Ti, Ta, Nb, V, W, Mo, Cr, Mn, Fe, Co, Ni, whereby dissolution of the above-mentioned alloying elements in the steel results in limited dissolution of (Fe, Cr)3C、(Fe，Cr)7C3、(W，Mo)6C and (Fe, Cr, Ni, Mn, W, Mo)23C6Isoalloyed cementite and fully miscible Mn3C、Fe3C、(Fe，Mn)3C、VC、Ta、NbC、(V，Ta，Nb)C、Mo2C、W2C、Fe3W3C、Fe3Mo3C、Fe3(W，Mo)3C, and the like; when the solid solution temperature is more than or equal to 1000 ℃ and more than or equal to 1050 ℃, most carbide phases are respectively basically dissolved and completely dissolved (the aging process is correspondingly influenced); the most important point is that the heating temperature of the existing traditional mainstream austenitic stainless steel solid solution technology is the highest theoretical solid solution temperature, and ideal types and amounts of solid solution dissolved carbide strengthening phases and intermetallic compound strengthening phases cannot be obtained. Therefore, the rapid solid solution temperature is not a simple constant single-point temperature value, but a complex and variable multi-point temperature range.
The traditional mainstream austenitic stainless steel solution heat treatment method is a one-stage single-point fixed isothermal solution heat treatment method under the condition that the heating temperature (the highest theoretical solution temperature) and the time are the only conditions. The prior mainstream solution heat treatment method for austenitic stainless steel can only effectively improve the solution dissolving capacity, range, quality, efficiency and the like of one or a few alloy element strengthening phases in austenitic stainless steel, can not greatly improve the solution dissolving capacity, range, quality, efficiency and the like of most other alloy element strengthening phases, even if the solid solution time is increased, the effect is very small (after the time reaches a certain degree, the solid solution dissolving capacity, range, quality, efficiency and the like of the solid solution strengthening phase of one or a few alloy elements reach a limit saturation state), the solid solution dissolving capacity, range, quality, efficiency and the like of the solid solution strengthening phase of the alloy elements can only reach a very limited state, therefore, the conventional mainstream austenitic stainless steel solution heat treatment method is a one-stage fixed limited solution heat treatment method, and is a heat treatment method which is considered as a ' comprehensive non- ' overall ' in a biased manner.
The austenitic stainless steel mainly precipitates the extremely small needle-like carbide with larger grain size at the aging temperature of lower than 500 ℃ and mainly precipitates (Fe, Cr, Ni, Mn, W, Mo) at the temperature of 550-740 DEG C23C6Carbide of the same composite alloy is mainly precipitated (Fe, Cr, Ni, Mn, W, Mo) at 625-670 deg.C23C6The carbide of the compound alloy is uniformly distributed in the crystal, the carbide begins to grow sharply at the temperature of about 700 ℃, and is mainly precipitated at the temperature of 800 ℃ (Fe, Cr, Ni, Mn, W, Mo)7C6When the temperature of the composite alloy carbide is higher than 900 ℃, the precipitation amount of the precipitated lamellar carbide is increased to influence the metal hardness and the mechanical property; the most important point is that the aging heating temperature of the traditional mainstream austenitic stainless steel is the highest aging theoretical temperature, and the aging precipitation carbide strengthening phase and the intermetallic compound strengthening phase with ideal type and quantity cannot be obtained. Therefore, the aging temperature is not a simple constant single-point temperature value, but a complex and variable multi-point temperature range.
The traditional mainstream austenitic stainless steel aging heat treatment method is a one-stage single-point fixed isothermal aging heat treatment method under the condition that the heating temperature (the highest aging theoretical temperature) and the time are the only conditions. The existing traditional mainstream austenitic stainless steel aging heat treatment method can only effectively improve the aging precipitation capability, range, quality, efficiency and the like of one or a few alloy element strengthening phases in austenitic stainless steel, can not effectively improve the aging precipitation capability, range, quality, efficiency and the like of most other alloy element strengthening phases, even if the aging time is increased, the effect is very small (after the time reaches a certain degree, the aging precipitation capacity, the range, the quality, the efficiency and the like of the solid solution strengthening phase or the minor alloy elements can reach a limit saturation state), the alloy element strengthening phase can only reach very limited aging precipitation capacity, range, quality, efficiency and the like, therefore, the conventional main flow austenitic stainless steel aging heat treatment method is a one-stage single-point fixed limited aging heat treatment method, and is a heat treatment method which is considered as a whole in a non-overall manner in a biased approximation manner.
The heat treatment manufacturability of the austenitic stainless steel is directly influenced by the following complex factors, particularly different hot working methods such as smelting, steel rolling, forging, heat treatment and the like of raw materials in steel plants and manufacturing plants: the comprehensive actions of the raw material quality, chemical composition (such as the characteristics and content of alloy elements such as C, Ti, Ta, Nb, V, W, Mo, Cr, Mn, Fe, Co, Ni, Cu) and the specification, batch state, hot working state and original heat treatment delivery state, including the hot working state parameters such as the starting and finishing temperature, heating time, operating time and cooling medium of the raw material forging, hot rolling or smelting related to the furnace batch, and the hot treatment delivery state including the original annealing, solution, aging, quenching and tempering) related to the hot working such as the forging and heat treatment related to the manufacturing plant, the forging deformation degree, the starting and finishing temperature, the heating time, the cooling medium, the type and condition of the heating equipment, the field environment temperature and other hot working methods directly influence the heat treatment manufacturability of the austenitic stainless steel.
Based on the above complex influence factors, the conventional mainstream austenitic stainless steel solid solution and aging heat treatment technology is difficult to solve the following special heat treatment technical theory and practice problems of 'one long one high three difference five low':
firstly, the heat treatment quality stability is poor, the qualified product rate is low: when the heat treatment quality stability is good, the primary heat treatment qualified product rate can only reach 99 percent (especially, the hardness value and the mechanical property can only reach the lower limit value even if the primary heat treatment qualified product rate is qualified); when the heat treatment quality stability is poor, the primary heat treatment yield is highly likely to fail by 100%.
Secondly, the hardness (or mechanical property) of the heat treatment is low and the consistency is poor: the solid solution and aging heat treatment can easily reach the middle and low hardness value of 20.0 HRC-26.5 HRC, can hardly reach the middle and high hardness value of 27.0 HRC-28.0 HRC, can hardly reach the high hardness value of 28.5 HRC-32.0 HRC, and even can generate the paradoxical phenomenon that the Brinell hardness is qualified and the Rockwell hardness is unqualified.
Thirdly, the heating time of the heat treatment is long, and the efficiency is low: the heating time under the highest temperature conditions of solid solution and aging is long, and the requirement of quick production is difficult to realize; passively increasing the times of heat treatment reworking and repairing to solve the problem of unqualified solid solution and aging heat treatment.
Fourthly, the service life of high-temperature components of the heating equipment is low: the high-temperature components of the heating equipment have long retention time under the highest temperature conditions of solid solution and aging and bear large high-temperature load, so that the service life is short.
Fifthly, the reliability of heat treatment heating is poor: the traditional mainstream austenitic stainless steel box type resistance furnace equipment (only has the functions of conduction and radiation heat transfer) has poor heating reliability, and the heating reliability of the traditional mainstream austenitic stainless steel box type resistance furnace equipment is far lower than that of heating equipment (simultaneously has the functions of conduction, radiation and convection heat transfer) such as a fluidized bed furnace, a salt bath furnace, a vacuum furnace and the like.
Sixthly, the heat treatment cost is high: the combination of the above disadvantages ultimately results in high heat treatment costs.
In summary, the conventional mainstream solid solution and aging heat treatment methods for austenitic stainless steel cannot solve the problems of poor heat treatment quality stability, low qualified product rate, low hardness (or low mechanical properties) and consistency, long heating time, low efficiency, poor heating reliability of heat treatment equipment, low service life of high-temperature components and parts, and high cost of the conventional mainstream solid solution and aging heat treatment methods for austenitic stainless steel.
Disclosure of Invention
The invention aims to solve the technical problem of providing a compound heat treatment method which fully dissolves solid and fully starts from low temperature for multiple times of temperature change and aging alternation. The method can solve the problems of poor quality stability, low qualified product rate, low hardness (or low mechanical property) and consistency, long heating time, low efficiency, poor heating reliability of heat treatment equipment, low service life of high-temperature components, high cost and the like of the conventional mainstream austenitic stainless steel solid solution and aging heat treatment.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a compound heat treatment method for fully dissolving and fully starting from low temperature multiple temperature-changing alternating aging, which comprises the following steps:
performing a substantially solution heat treatment process, the substantially solution heat treatment process comprising: heating and heat preservation are carried out when the austenitic stainless steel is heated to the minimum temperature of full solid solution from room temperature within a specified time in a heating furnace, heating and heat preservation are carried out when the austenitic stainless steel is continuously heated to the intermediate solid solution temperature of full solid solution from the minimum temperature of full solid solution, heating and heat preservation are carried out when the austenitic stainless steel is continuously heated to the maximum temperature of full solid solution from the intermediate solid solution temperature of full solid solution, and finally cooling is carried out when the austenitic stainless steel is taken out of the furnace and is cooled from the maximum temperature of full solid solution to the minimum temperature of temperature-changing alternating ageing for multiple times by adopting a specific cooling mode;
after the full solid solution heat treatment is finished, performing full low-temperature multiple variable temperature alternating aging heat treatment, fully starting from low temperature to high temperature and fully starting from high temperature to low temperature multiple variable temperature alternating aging heat treatment, wherein the full solid solution heat treatment comprises the following steps of 1 st full low-temperature multiple variable temperature alternating aging process: the method specifically comprises the following steps that the first half part of the 1 st time is fully started from a low temperature to a high temperature non-variable temperature alternating aging process: firstly, cooling a first part of austenitic stainless steel which is fully dissolved in solution in a heating furnace within a specified time to a minimum temperature which is fully started from low-temperature multiple temperature-changing alternating ageing, then continuously heating and preserving the austenitic stainless steel to a middle temperature which is fully started from low-temperature multiple temperature-changing alternating ageing, then continuously heating and preserving the austenitic stainless steel to a maximum temperature which is fully started from low-temperature multiple temperature-changing alternating ageing, and then continuously heating the second half part of the 1 st time which is started from high temperature and ended from low-temperature multiple temperature-changing alternating ageing to obtain the austenitic stainless steel, wherein the temperature of the austenitic stainless steel is controlled by a temperature controller: firstly, continuously heating and preserving heat of austenitic stainless steel in a heating furnace from the highest temperature of low-temperature multiple-temperature-changing alternating ageing to the middle temperature of multiple-temperature-changing alternating ageing in a specified time, and then continuously heating and preserving heat of austenitic stainless steel in the heating furnace from the middle temperature of low-temperature multiple-temperature-changing alternating ageing to the lowest temperature of multiple-temperature-changing alternating ageing in the specified time; after the 1 st time fully begins to the end of the low-temperature multiple temperature-changing alternating aging process, then the 2 nd time, the 3 rd time or the 4 th time temperature-changing alternating aging process is carried out again: sequentially and reversely repeating the second half part of the 2 nd time in the 1 st time for 1 time in the high-temperature and low-temperature multiple temperature-changing and alternating ageing process, sequentially and reversely repeating the 3 rd time for 1 time in the 2 nd time temperature-changing and alternating ageing process, sequentially and reversely repeating the 4 th time for 1 time in the 3 rd time temperature-changing and alternating ageing process; and after the 2 nd, 3 rd or 4 th time of the low-temperature multiple temperature-changing alternating aging process is completely finished, cooling the austenitic stainless steel to room temperature by adopting a specific cooling mode.
Optionally, the total variable temperature alternating aging time fully starting from the low-temperature multiple variable temperature alternating aging heat treatment is 1 time, and each variable temperature alternating aging process at least simultaneously comprises 1 time of temperature rise and 1 time of temperature fall.
Optionally, the method is fully started in a multi-stage temperature rise temperature interval related to low-temperature multiple temperature change alternating aging: the method comprises a 1 st full multi-stage non-alternating temperature rise temperature interval: n is more than or equal to 3 and less than or equal to 7 from the lowest heating temperature interval Tafmin-1 of the full multi-stage heating and aging, n-2 middle heating temperature intervals Tafm-1 of the full multi-stage aging and finally n is more than or equal to n and less than or equal to 7 from the highest heating temperature interval Tafmin-1 of the full multi-stage aging; the 2 nd time, the 3 rd time or the 4 th time fully begins in a low-temperature multiple-time variable-temperature alternating heating aging temperature interval: the full heating and aging process is sequentially repeated, and the numerical values of the lowest temperature interval of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time of full starting at the low-temperature multiple temperature-changing alternating heating and aging are represented by the following relational expressions: tafmin-1 is more than Tafmin-2 is more than Tafmin-3 is more than Tafmin-4, and the numerical relation of the intermediate heating temperature interval in the full heating and aging process of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafm-1 is more than Tafm-2 is more than Tafm-3 is more than Tafm-4, the numerical value of the highest temperature interval of the temperature change and alternation and temperature rise aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time fully begins at the low temperature for a plurality of times is as follows: tafmax-1 > Tafmax-2 > Tafmax-3 > Tafmax-4; the temperature-raising aging temperature range is fully started from the low-temperature multiple-time temperature-changing alternating temperature-raising aging temperature range, and any one of a temperature-raising aging lowest heating temperature range, a temperature-raising aging middle heating temperature range and a temperature-raising aging highest temperature range is not repeated, and any one of a temperature-lowering aging lowest heating temperature range, a temperature-lowering aging middle heating temperature range and a temperature-lowering aging highest temperature range is not repeated.
Optionally, the method is fully started in a multi-stage cooling and aging temperature interval related to low-temperature multiple temperature-changing alternating aging: the method comprises a 1 st full multi-stage non-alternating cooling aging temperature interval: n staged full multi-stage cooling and aging heating temperature intervals are started from a full multi-stage cooling and aging highest heating temperature interval Tafmax-1, sequentially pass through n-2 full multi-stage aging intermediate heating temperature intervals Tafm-1 and finally end to a full multi-stage aging lowest heating temperature interval Tafmin-1, and n is more than or equal to 3 and less than or equal to 7; the 2 nd time, the 3 rd time or the 4 th time fully begins in a low-temperature multiple-time variable-temperature alternating cooling aging temperature interval: the cooling and aging process is sequentially repeated, and the relation of the numerical values of the lowest temperature interval of the low-temperature multiple-time variable-temperature alternating cooling and aging at the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafmin-1 is more than Tafmin-2 is more than Tafmin-3 is more than Tafmin-4, and the numerical relation of the intermediate heating temperature interval of the temperature-changing alternating aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafm-1 is more than Tafm-2 is more than Tafm-3 is more than Tafm-4, the numerical value of the highest temperature interval of the temperature-changing and alternating cooling aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time fully begins at the low temperature for a plurality of times is as follows: tafmax-1 > Tafmax-2 > Tafmax-3 > Tafmax-4; the temperature-reducing aging temperature interval, the temperature-reducing aging intermediate heating temperature interval and the temperature-reducing aging highest temperature interval do not repeatedly occur in the low-temperature multiple-temperature-changing alternating temperature-reducing aging temperature interval, and the temperature-increasing aging minimum heating temperature interval, the temperature-increasing aging intermediate heating temperature interval and the temperature-increasing aging highest temperature interval do not repeatedly occur.
Optionally, the mathematical relation between the lowest heating temperature Tafmin and the lowest theoretical heating temperature Tafmin of the aging process, which is fully started from the low-temperature multiple-temperature-changing alternating aging process, is as follows: tafmin ═ Taftmin;
in the formula, Tafmin is the lowest heating temperature (DEG C) of the aging process which is fully started from low temperature multiple temperature change and alternation; taftmin is the minimum theoretical heating temperature of aging, DEG C.
Optionally, the mathematical relation between the maximum heating temperature Tafmax of the low-temperature multiple-temperature-change alternating ageing and the maximum theoretical heating temperature Tafmax of the ageing is as follows: tafmax is Taftmax;
in the formula, Tafmin is the highest heating temperature (DEG C) of the aging process which is fully started from low temperature multiple temperature change and alternation; taftmin is the maximum theoretical heating temperature of aging at deg.C.
Optionally, the mathematical relation between the intermediate heating temperature Tafm, the aging minimum heating temperature Tafmin and the aging maximum heating temperature Tafmax, which is sufficiently started at each stage of the low-temperature multiple temperature-changing alternating aging, is as follows: tafm ═ Tafmin + ni(Tafmax–Tafmin)/(n–1)；
In the formula, Tafm is the intermediate heating temperature and the temperature in each stage of the low-temperature multiple temperature-changing alternating ageing, and is the specific stage temperature from the 2 nd stage to the 2 nd stage of the low-temperature multiple temperature-rising or temperature-reducing temperature-changing alternating ageing fully; tafmin is the lowest heating temperature of alternating aging at low temperature for multiple times of temperature rise or temperature fall and temperature change, and is measured at the temperature of DEG C; n isiThe specific nth heating temperature interval from the 2 nd to the 2 nd last stages from low to high or from high to lowiNumber of stages, n being not less than 1iLess than or equal to 5; tafmax is the maximum heating temperature of alternating aging at low temperature for multiple times or at variable temperature; (Tafmax-Tafmin)/n is a specific constant value which fully begins at low temperature for multiple times of temperature rise or temperature fall and changes temperature, and changes the aging time to increase or decrease the temperature difference gradually; n is the lowest temperature Tafmin of low-temperature multiple-temperature-change alternating aging and the last low-temperature multiple-time changeThe total number of stages of a temperature alternating ageing highest heating temperature Tafmax zone or a temperature alternating ageing highest heating temperature Tafmax zone starting from low temperature multiple temperature changing alternating ageing and ending at low temperature multiple temperature changing alternating ageing lowest heating temperature Tafmin is more than or equal to 3 and less than or equal to 7.
Optionally, when the low-temperature multiple temperature-changing alternating ageing time is performed according to the equal time method, the equal time method is performed by fully starting from the total heating time tau of the low-temperature multiple temperature-changing alternating ageing timeafNHeating time tau in each stage of aging corresponding to heating temperature intervals of 1 st, 2 nd, 3 rd, … …, and nth stages of heatingafnThe mathematical relationship of (a) is: tau isafN＝∑τafn＝∑τafN/N；
In the formula tauafNThe method is characterized in that the method is a uniform time method which is fully started from the total time of low-temperature multiple temperature-changing alternating aging heating for min or h; tau isafnHeating time in each stage of heating temperature interval corresponding to aging in 1 st stage, 2 nd stage, 3 rd stage, … …, and nth stage of heating temperature interval is tau/min or h/haf1、τaf2、τaf3、τaf4、τaf5、τaf6、τaf7，τaf1＝τaf2＝τaf3＝τaf4＝τaf5＝τaf6＝τaf7(ii) a N is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7; n is the number of nth stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and n is more than or equal to 1 and less than or equal to 7.
Optionally, when the low-temperature multiple temperature-changing alternating ageing time is performed according to an increasing time method, the increasing time method is performed by fully starting from the total heating time tau of the low-temperature multiple temperature-changing alternating ageing timeafNHeating time tau in each stage of aging corresponding to heating temperature intervals of 1 st, 2 nd, 3 rd, … …, and nth stages of heatingafnThe mathematical relationship of (a) is:
τafN＝∑τafn＝∑[τaf1+(n–1)τaf0]
in the formula tauafNThe method is characterized in that the method is a time increasing method which fully begins with the total time of low-temperature multiple temperature-changing alternating aging heating for min or h; n is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7; tau isafnHeating time of each stage of low-temperature multiple temperature-changing alternating ageing is min/time or h/time, and is tauaf1、τaf2、τaf3、τaf4、τaf5、τaf6、τaf7，τaf1＞τaf2＞τaf3＞τaf4＞τaf5＞τaf6＞τaf7(ii) a n is the number of nth stages which are fully started from low-temperature multiple variable-temperature alternating aging heating, and n is more than or equal to 1 and less than or equal to 7; tau isaf1Heating time in a first stage of low-temperature multiple temperature-changing alternating ageing is fully started for min/time or h/time; tau isaf0The heating time increases the grade difference for min/time or h/time and is the same and unchangeable specific numerical value.
Optionally, the low-temperature multiple-temperature-changing alternating aging heat treatment method comprises the following steps: comprises the following steps of 1 st fully starting from a low-temperature multiple-temperature-changing alternating aging process: the method specifically comprises the following steps that the first half part of the 1 st time is fully started from a low temperature to a high temperature non-variable temperature alternating aging process: firstly, heating and preserving the austenitic stainless steel at the lowest temperature of low-temperature multiple temperature-changing alternating ageing in a heating furnace within a set time, then continuously and rapidly heating the austenitic stainless steel to the middle temperature of the low-temperature multiple temperature-changing alternating ageing for heating and preserving, then continuously and rapidly heating the austenitic stainless steel to the highest temperature of final ageing for heating and preserving, and then continuing the second half of the 1 st time, namely the process of beginning at high temperature and ending at low-temperature multiple temperature-changing alternating ageing: firstly, continuously cooling the austenitic stainless steel from the highest temperature of low-temperature multiple temperature-changing alternating ageing to the middle temperature of multiple temperature-changing alternating ageing for heating and heat preservation in a heating furnace within a specified time, and then continuously cooling the austenitic stainless steel from the middle temperature of low-temperature multiple temperature-changing alternating ageing to the lowest temperature of low-temperature multiple temperature-changing alternating ageing for heating and heat preservation in the heating furnace within the specified time; after the 1 st time fully begins to the end of the low-temperature multiple temperature-changing alternating aging process, then the 2 nd time, the 3 rd time or the 4 th time temperature-changing alternating aging process is carried out again: sequentially and reversely repeating the second half part of the 2 nd time in the 1 st time for 1 time in the high-temperature and low-temperature multiple temperature-changing and alternating ageing process, sequentially and reversely repeating the 3 rd time for 1 time in the 2 nd time temperature-changing and alternating ageing process, sequentially and reversely repeating the 4 th time for 1 time in the 3 rd time temperature-changing and alternating ageing process; and after the 2 nd, 3 rd or 4 th time of the low-temperature multiple temperature-changing alternating aging process is completely finished, finally, continuously cooling the austenitic stainless steel to room temperature by adopting a specific cooling mode.
The scheme of the invention at least comprises the following beneficial effects:
(1) the invention relates to a composite heat treatment method for fully dissolving and fully starting from low temperature multiple temperature change and aging, which has the advantages of technical feasibility, process adaptability, quality reliability, economic rationality and use safety, and can fundamentally solve the problems of the theory and practice of the special heat treatment technology of poor quality stability, low qualified product rate, low hardness (or low mechanical property) and consistency, long heating time, low efficiency, poor heating reliability of heat treatment equipment, low service life of high-temperature components, high cost and the like of 'one long one high three difference five low'.
(2) The composite heat treatment method of alternating aging with full solid solution and full starting from low temperature for multiple times can effectively obtain the range of the optimized heat treatment hardness (or mechanical property) with the upper limit distribution and the tolerance less than or equal to 3.0 HRC.
(3) The invention relates to a composite heat treatment method for fully dissolving and fully starting from low temperature multiple temperature change and alternating aging, and the final heat treatment hardness qualified rate is up to 100%.
(4) The alternating aging composite heat treatment method with full solid solution and full starting from low temperature for multiple times can effectively improve the heat treatment efficiency (such as the maximization of furnace charging amount and the requirement of mass production can be realized, the total time of solid solution and aging heat preservation is reduced, and the like).
Drawings
FIG. 1 is a schematic diagram of the prior austenitic stainless steel showing the solution and aging heat treatment process (including the heating, heat preservation, cooling processes, time used and the like of the solution and aging heat treatment) consisting of 1 time 1-stage solution treatment at the highest solution temperature and 1 time 1-stage aging treatment at the highest aging temperature;
FIG. 2 is a schematic flow diagram of the composite heat treatment method of the present invention with full solution and full start at low temperature for multiple temperature-varying and alternate aging;
FIG. 3 is a schematic diagram of the austenitic stainless steel of the present invention, which is composed of 1 time of 4-stage full solid solution under the condition of full solid solution temperature and 1 time of 2 times (each 1 time comprises 3 sub-times, wherein the 1 st sub-time has no alternation, and the rest 2 sub-times have alternation) under the condition of full aging temperature, and 3 stages of full solid solution and full aging heat treatment process (including temperature rise, heat preservation, temperature reduction, cooling process and time used and the like of full solid solution and full aging heat treatment) fully started from the low-temperature multiple temperature-changing alternating aging heat treatment process.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In the invention, the method for fully solid-dissolving and fully starting from low-temperature multiple variable-temperature alternating-aging composite heat treatment comprises a 'full solid-dissolving heat treatment method' and a 'full starting from low-temperature multiple variable-temperature alternating-aging heat treatment method' continuously using composite compositions 'a full solid-dissolving and fully starting from low-temperature multiple variable-temperature alternating-aging composite heat treatment method'; the method comprises the following steps: firstly, carrying out the first part of full solution heat treatment, and finally, continuously carrying out the second part of full variable temperature alternate aging heat treatment at low temperature for multiple times. The first partial full solution heat treatment process: by virtue of the first partial full solution heat treatment process: the method comprises the following steps of heating and preserving heat of austenitic stainless steel from room temperature to the lowest solid solution temperature within a specified time in a heating furnace, heating and preserving heat of austenitic stainless steel when the austenitic stainless steel is continuously heated to the middle solid solution temperature, heating and preserving heat of austenitic stainless steel when the austenitic stainless steel is continuously heated from room temperature to the highest solid solution temperature, and finally cooling when the austenitic stainless steel is rapidly cooled from the highest full solid solution temperature to the lowest temperature of alternating temperature change and aging for multiple times by adopting a specific cooling mode; the second part is fully started in the low-temperature multiple-temperature-changing alternating aging heat treatment process: namely, after the first part is fully subjected to solid solution heat treatment, the second part is fully subjected to low-temperature multiple variable temperature alternate aging heat treatment, and the 1 st part is fully subjected to low-temperature multiple variable temperature alternate aging process by means of a low-temperature final high-temperature and high-temperature final low-temperature multiple variable temperature alternate aging heat treatment process: the method specifically comprises the following steps that the first half part of the 1 st time is fully started from a low temperature to a high temperature non-variable temperature alternating aging process: firstly, cooling a first part of austenitic stainless steel which is fully dissolved in solution in a heating furnace within a specified time to a lowest temperature which is fully started at low-temperature multiple temperature-changing alternating ageing, then continuously heating and preserving the austenitic stainless steel to a middle temperature which is fully started at the low-temperature multiple temperature-changing alternating ageing, and then continuously heating and preserving the austenitic stainless steel to a highest temperature which is fully started at the low-temperature multiple temperature-changing alternating ageing (the first half part of the 1 st time is fully started at low temperature and is ended at the high-temperature non-temperature-changing alternating ageing process), and then continuing the second half part of the 1 st time which is started at high temperature and is ended at the low-temperature multiple temperature-changing alternating ageing process: firstly, continuously heating and preserving heat of austenitic stainless steel from the highest temperature of low-temperature multiple-temperature alternating ageing to the middle temperature of multiple-temperature alternating ageing in a heating furnace within a specified time, and then continuously heating and preserving heat of austenitic stainless steel from the middle temperature of low-temperature multiple-temperature alternating ageing to the lowest temperature of multiple-temperature alternating ageing in the heating furnace within the specified time (the second half of the first time is fully started from the high temperature to the end of the low-temperature multiple-temperature alternating ageing process, and the first time is fully started from the low-temperature multiple-temperature alternating ageing process and is also completely ended); after the 1 st time fully begins to the end of the low-temperature multiple temperature-changing alternating aging process, then the 2 nd time, the 3 rd time or the 4 th time temperature-changing alternating aging process is carried out again: carrying out multiple temperature-changing alternating ageing for 2 times, sequentially and reversely repeating the second half part of the 1 st time for 1 time (the end of the multiple temperature-changing alternating ageing for 2 times) in the high-temperature and low-temperature multiple temperature-changing alternating ageing process, or sequentially and reversely repeating the multiple temperature-changing alternating ageing for 2 times for 1 time (the end of the multiple temperature-changing alternating ageing for 3 times) in the 3 rd time, or sequentially and reversely repeating the multiple temperature-changing alternating ageing for 4 times for 1 time (the end of the multiple temperature-changing alternating ageing for 4 times); after the whole process of the low-temperature multiple temperature-changing alternating ageing process is completed in the 2 nd time, the 3 rd time or the 4 th time, the process steps of cooling and the like performed when the austenitic stainless steel is cooled to the room temperature by adopting a specific cooling mode are continued, and the whole process of the low-temperature multiple temperature-changing alternating ageing heat treatment process is started (the second part is fully started in the whole process of the low-temperature multiple temperature-changing alternating ageing heat treatment process is completed).
In the present invention, the first partial sufficient solution heat treatment method is a sufficient solution heat treatment method performed under conditions such as a multistage temperature range, a multistage heating sequence, a multistage heating time, a multistage heating frequency, a specific cooling method, and the like.
In the present invention, the total number of solid solutions in the first part of the sufficient solid solution heat treatment is 1.
In the present invention, the first partial sufficient solution heat treatment method is a 3-stage sufficient solution heat treatment method or a 4-stage sufficient solution heat treatment method.
In the present invention, the multi-stage temperature interval of the 3-stage sufficient solution heat treatment means: and a 3-stage temperature rise temperature range which starts from the stage of raising the temperature from room temperature to the minimum solid solution temperature Tsfmin, then raises the temperature to the intermediate solid solution temperature Tsfm, and finally raises the temperature to the maximum solid solution temperature Tfmax.
In the present invention, the multi-stage temperature interval of the 4-stage sufficient solution heat treatment means: starting from the stage of raising the temperature from room temperature to the lowest solid solution temperature Tsfmin, and then sequentially raising the temperature to the first stage temperature Tsfm of intermediate solid solution1And a second stage temperature of intermediate solid solution Tsfm2And a 4-stage temperature rise temperature range in which the temperature is finally raised to the solid solution maximum temperature Tsfmax.
In the present invention, the first partial full solution heat treatment has a multi-stage temperature interval, and the number of stages of the full rapid solution temperature interval is moderate: the solid solution heating temperature range is narrow (the effective temperature range is between 100 ℃ and 200 ℃), for example, the solid solution capacity of the stage number of the solid solution temperature interval is 1 (the prior solid solution technology), the solid solution capacity of the stage 2 is better, and the solid solution capacity of the stage more than or equal to 6 is excessive, so that the embodiment sets the first part full solid solution temperature interval to be 3 stages or 4 stages, can greatly improve the solid solution capacity, the quality, the efficiency and the like, and particularly can greatly increase the solid solution strengthening phase, reduce or inhibit the solid solution weakening phase, reduce the high-temperature heating time, improve the efficiency, prolong the service life of high-temperature components of heating equipment and the like.
In the invention, the mathematical relation between the minimum heating temperature Tsfmin for full solid solution and the minimum theoretical heating temperature Tsftmin for solid solution is as follows: tsfmin is Tsftmin;
tsfmin is the lowest heating temperature for full solid solution, DEG C; tsftmin is the minimum theoretical heating temperature for full solutionizing at.
In the present invention, the mathematical relationship between the maximum heating temperature for sufficient solid solution Tsfmax and the maximum theoretical heating temperature for solid solution Tsftmax is: tsfmax is Tsftmax;
wherein Tsfmax is the maximum heating temperature for full solid solution, DEG C; tsfmax is the maximum theoretical heating temperature for full solution at C.
In the invention, the mathematical relation between the intermediate solid solution heating temperature Tsfm of full solid solution in 3 stages, the maximum solid solution heating temperature Tfmax and the minimum solid solution heating temperature Tfmin is as follows:
Tsfm＝(Tsfmax+Tsfmin)/2
wherein Tsfm is the heating temperature of the intermediate solid solution stage of full solid solution, and the temperature is also the heating temperature of the second stage of full solid solution; tsfmax is the maximum heating temperature for full solid solution, DEG C, and is also the heating temperature at the final stage of full solid solution; tsfmin is the minimum heating temperature for sufficient solid solution, DEG C, and is also the heating temperature at the beginning of sufficient solid solution.
In the invention, the heating temperature Tsfm of the first stage of 4-stage full solid solution intermediate solid solution1And intermediate solid solution second stage heating temperature Tsfm2The mathematical relations with the solid solution maximum heating temperature Tfmax and the solid solution minimum heating temperature Tfmin are respectively as follows:
Tsfm1＝1/3(Tsfmax–Tsfmin)+Tsfmin
Tsfm2＝2/3(Tsfmax–Tsfmin)+Tsfmin
in the formula Tsfm1The heating temperature of the first stage of full solid solution and the heating temperature of the second stage of full solid solution are the same at the temperature of the first stage of full solid solution; tsfm2The heating temperature of the second stage of full solid solution and intermediate solid solution is the temperature of the third stage of full solid solution; tsfmax is the maximum heating temperature for full solid solution, DEG C, and is also the heating temperature at the final stage of full solid solution; tsfmin is the minimum heating temperature for sufficient solid solution, DEG C, and is also the heating temperature at the beginning of sufficient solid solution.
In the present invention, the first portion full solid solution multi-stage time interval and the full solid solution multi-stage temperature interval are also set to be 3 stages or 4 stages in correspondence; the sufficient solid solution time is not suitable to be too long or too short: if the time is too long, the solid solution is sufficient but exceeds the solubility limit of the strengthening phase, and if the time is too short, the solid solution strengthening phase is not sufficiently dissolved, so that the solid solution capacity, quality, efficiency, and the like can be greatly improved by setting the sufficient solid solution time to a moderate value.
In the present invention, when the sufficient solution treatment time is performed by the uniform time method, the multi-stage sufficient solution treatment heating by the uniform time methodTotal time τsfNAnd heating time tau of each stage of full solid solutionsfnThe mathematical relationship of (a) is:
τsfN＝∑τsfn＝∑τsfN/N
in the formula tausfNThe total time of multi-stage full solid solution heating of an equal time method is min or h; tau issfnHeating time in each stage, min or h, when τ is dividedsf1、τsf2、τsf3At 3 stages in time, τsf1＝τsf2＝τsf3When dividing τsf1、τsf2、τsf3、τsf4At 4 stages in time, τsf1＝τsf2＝τsf3＝τsf4(ii) a N is the total number of stages of sufficient solid solution heating, and is 3 or 4; n is the number of n stages of sufficient solution heating, and n is 1, 2, 3 or 4.
In the present invention, when the sufficient solid solution time is performed by the incremental time method, the total time τ of the multi-stage sufficient solid solution heating of the incremental time methodsfNAnd heating time tau of each stage of full solid solutionsfnThe mathematical relationship of (a) is:
τsfN＝∑τsfn＝∑[τsf1+(n–1)τsf0]
in the formula tausfNThe total time of multi-stage full solid solution heating of an increasing time method is min or h; n is the total number of stages of sufficient solid solution heating, and is 3 or 4; tau issfnHeating time of each stage, min or h, for full solid solutionsf1、τsf2、τsf3Or τsf4，τsf1＞τsf2＞τsf3Or > tausf4(ii) a n is the number of the nth stage of sufficient solid solution heating, and n is 1, 2, 3 or 4; tau issf1Heating time of the first stage for full solid solution, min or h; tau issf0The time step difference, min or h, is decreased for sufficient solid solution heating, and is the same and unchanging specific numerical value.
In the present invention, when the sufficient solid solution time is performed in a decreasing time method, the total time τ of the multi-stage sufficient solid solution heating of the decreasing time methodsfNAnd heating at each stage of full solid solutionTime tausfnThe mathematical relationship of (a) is:
τsfN＝∑τsfn＝∑[τsf1–(n–1)τsf0]
in the formula tausfNThe total time of multi-stage full solid solution heating of a decreasing time method is min or h; n is the total number of stages of sufficient solid solution heating, and is 3 or 4; tau issfnHeating time of each stage, min or h, for full solid solutionsf1、τsf2、τsf3Or τsf4，τsf1＜τsf2＜τsf3Or < tausf4；τsf1Heating time of the first stage for full solid solution, min or h; n is the number of the nth stage of sufficient solid solution heating, and n is 1, 2, 3 or 4; tau issf0The time step difference, min or h, is decreased for sufficient solid solution heating, and is the same and unchanging specific numerical value.
In the present invention, the first partial full solution heat treatment final cooling method is: opening the furnace door or adopting other cooling modes to quickly cool the workpiece without discharging the workpiece out of the furnace.
In the invention, the first part 3 stage full solution heat treatment process comprises the following steps: the first stage is as follows: the austenitic stainless steel is heated from room temperature to a full solution minimum temperature Tsfmin (and heated and held within a time specified by the process) in a heating furnace → the second stage: continuously heating the austenitic stainless steel from the full solid solution minimum temperature Tsfmin to the intermediate solid solution temperature Tsfm (and heating and heat preservation within the time specified by the process) → a third stage: continuously heating the austenitic stainless steel from the full solid solution intermediate solid solution temperature Tsfm to the full solid solution maximum temperature Tfmax (heating and heat preservation within the time specified by the process) → finally continuously cooling the austenitic stainless steel from the full solid solution maximum temperature Tfmax to the low temperature multiple temperature-changing alternating ageing minimum temperature Tafmin (heating and heat preservation within the time specified by the process) by adopting a specific cooling mode.
In the invention, the first part 4-stage full solution heat treatment process comprises the following steps: the first stage is as follows: the austenitic stainless steel is heated in a heating furnace from room temperature to a full solid solution minimum temperature Tsfmin (and specified in the process)Heat and hold over time) → second stage: continuously heating the austenitic stainless steel from the minimum temperature Tsfmin of full solid solution to the first stage temperature Tsfm of full solid solution intermediate solid solution1(and heating and holding within the process specified time) → third stage: continuously dissolving the austenitic stainless steel from full solid solution to intermediate solid solution for the first stage temperature Tsfm1Raising the temperature to the second stage temperature Tsfm of full solid solution and intermediate solid solution2(and heat and soak for the specified time of the process) → fourth stage: continuously dissolving the austenitic stainless steel from full solid solution to intermediate solid solution at a second stage temperature Tsfm2Raising the temperature to the full solid solution maximum temperature Tfmax (and heating and preserving the temperature within the time specified by the process) → finally continuing to adopt a specific cooling mode to cool the austenitic stainless steel out of the furnace from the full solid solution maximum temperature Tfmax to the minimum temperature Tafmin of the variable temperature alternating ageing for a plurality of times starting from the low temperature (and heating and preserving the temperature within the time specified by the process).
In the present invention, the second part is sufficiently started by the low-temperature multiple temperature swing alternate aging heat treatment method, which is performed continuously under conditions such as a multistage temperature zone, a multistage heating sequence, a multistage heating time, a multistage heating frequency, a specific cooling method, and the like after the first part is sufficiently solid solution heat treated.
In the invention, the total variable temperature alternate aging times of the second part, which is fully started from the low-temperature multiple variable temperature alternate aging heat treatment, is 1 time (including 2, 3 or 4 times), and each variable temperature alternate aging process at least simultaneously comprises 1 time of temperature rise and 1 time of temperature drop.
In the present invention, the second part is sufficiently started from a multi-stage temperature-rise temperature zone relating to low-temperature multiple-temperature-rise alternating aging: the method comprises a 1 st full multi-stage non-alternating temperature rise temperature interval: starting from a full multi-stage heating and aging minimum heating temperature interval Tafmin (marked as Tafmin-1), sequentially passing through n-2 full multi-stage aging intermediate heating temperature intervals Tafm (marked as Tafm-1) and finally finishing to a full multi-stage aging maximum heating temperature interval Tafmax (marked as Tafmax-1), wherein n is more than or equal to 3 and less than or equal to 7, namely n is 3, 4, 5, 6 or 7; the 2 nd time, the 3 rd time or the 4 th time fully begins in a low-temperature multiple-time variable-temperature alternating heating aging temperature interval: the full heating and aging process is sequentially repeated, and the numerical values of the lowest temperature interval of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time of full starting at the low-temperature multiple temperature-changing alternating heating and aging are represented by the following relational expressions: tafmin-1 is more than Tafmin-2 is more than Tafmin-3 is more than Tafmin-4, and the numerical relation of the intermediate heating temperature interval in the full heating and aging process of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafm-1 is more than Tafm-2 is more than Tafm-3 is more than Tafm-4, the numerical value of the highest temperature interval of the temperature change and alternation and temperature rise aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time fully begins at the low temperature for a plurality of times is as follows: tafmax-1 > Tafmax-2 > Tafmax-3 > Tafmax-4; the temperature-raising aging temperature range is fully started from the low-temperature multiple-time temperature-changing alternating temperature-raising aging temperature range, and any one of a temperature-raising aging lowest heating temperature range, a temperature-raising aging middle heating temperature range and a temperature-raising aging highest temperature range is not repeated, and any one of a temperature-lowering aging lowest heating temperature range, a temperature-lowering aging middle heating temperature range and a temperature-lowering aging highest temperature range is not repeated.
In the present invention, the second part is sufficiently started in a multi-stage temperature-reduction aging temperature zone relating to low-temperature multiple temperature-reduction alternating aging: the method comprises a 1 st full multi-stage non-alternating cooling aging temperature interval: the method comprises the steps of starting from a full multi-stage cooling and aging highest heating temperature interval Tafmax (marked as Tafmax-1), sequentially passing through n-2 full multi-stage aging intermediate heating temperature intervals Tafm (marked as Tafm-1) and finally finishing to a full multi-stage aging lowest heating temperature interval Tafmin (marked as Tafmin-1), wherein n is more than or equal to 3 and less than or equal to 7, namely n is 3, 4, 5, 6 or 7; the 2 nd time, the 3 rd time or the 4 th time fully begins in a low-temperature multiple-time variable-temperature alternating cooling aging temperature interval: the cooling and aging process is sequentially repeated, and the relation of the numerical values of the lowest temperature interval of the low-temperature multiple-time variable-temperature alternating cooling and aging at the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafmin-1 is more than Tafmin-2 is more than Tafmin-3 is more than Tafmin-4, and the numerical relation of the intermediate heating temperature interval of the temperature-changing alternating aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafm-1 is more than Tafm-2 is more than Tafm-3 is more than Tafm-4, the numerical value of the highest temperature interval of the temperature-changing and alternating cooling aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time fully begins at the low temperature for a plurality of times is as follows: tafmax-1 > Tafmax-2 > Tafmax-3 > Tafmax-4; the temperature-reducing aging temperature interval, the temperature-reducing aging intermediate heating temperature interval and the temperature-reducing aging highest temperature interval do not repeatedly occur in the low-temperature multiple-temperature-changing alternating temperature-reducing aging temperature interval, and the temperature-increasing aging minimum heating temperature interval, the temperature-increasing aging intermediate heating temperature interval and the temperature-increasing aging highest temperature interval do not repeatedly occur.
In the invention, because the aging temperature range of the austenitic stainless steel is narrow (between 170 ℃ and 230 ℃), the temperature range of the aging temperature of the austenitic stainless steel is not too small or too large when the temperature is fully started in a low-temperature multiple-time temperature-changing alternating aging temperature range: the aging temperature range of the 1 stage belongs to the prior art (no temperature difference), and the aging capability is too poor; in the aging temperature range of 2 stages (the temperature difference is large), the aging capability is increased but is still insufficient; when the temperature is within the aging temperature range of not less than 8 stages (the temperature difference is too small), the aging capability is excessive (in fact, a certain aging capability is still provided in each temperature rise or decrease transition stage where the temperature difference is too small). Therefore, the temperature range of the low-temperature multiple-time variable-temperature alternating ageing is set to be 3-7, namely n is 3, 4, 5, 6 or 7 stages, so that the ageing capacity, range, quality, efficiency and the like can be improved.
In the invention, the mathematical relation between the lowest heating temperature Tafmin and the lowest theoretical heating temperature Taftmin of the aging process, which is fully started from low-temperature multiple temperature-changing alternating aging, is as follows: tafmin ═ Taftmin;
in the formula, Tafmin is the lowest heating temperature (DEG C) of the aging process which is fully started from low temperature multiple temperature change and alternation; taftmin is the minimum theoretical heating temperature of aging, DEG C.
In the invention, the mathematical relation between the maximum heating temperature Tafmax and the maximum theoretical heating temperature Taftmax of the aging process, which is fully started from the low-temperature multiple-time temperature change and alternating aging process, is as follows: tafmax is Taftmax;
in the formula, Tafmin is the highest heating temperature (DEG C) of the aging process which is fully started from low temperature multiple temperature change and alternation; taftmin is the maximum theoretical heating temperature of aging at deg.C.
In the invention, the mathematical relation between the intermediate heating temperature Tafm of the second part, the ageing minimum heating temperature Tafmin and the ageing maximum heating temperature Tafmax of each stage of the low-temperature multiple temperature-changing alternating ageing is as follows: tafm ═ Tafmin + ni(Tafmax–Tafmin)/(n–1)；
In the formula, Tafm is the intermediate heating temperature and the temperature in each stage of the low-temperature multiple temperature-changing alternating ageing, and is the specific stage temperature from the 2 nd stage to the 2 nd stage of the low-temperature multiple temperature-rising or temperature-reducing temperature-changing alternating ageing fully; tafmin is the lowest heating temperature of alternating aging at low temperature for multiple times of temperature rise or temperature fall and temperature change, and is measured at the temperature of DEG C; n isiThe specific nth heating temperature interval from the 2 nd to the 2 nd last stages from low to high or from high to lowiNumber of stages, n being not less than 1iN is less than or equal to 5i1, 2, 3, 4 or 5; tafmax is the maximum heating temperature of alternating aging at low temperature for multiple times or at variable temperature; (Tafmax-Tafmin)/n is a specific constant value which fully begins at low temperature for multiple times of temperature rise or temperature fall and changes temperature, and changes the aging time to increase or decrease the temperature difference gradually; n is the total number of stages starting from the lowest temperature Tafmin of low-temperature multiple temperature-changing alternating ageing and ending at the highest heating temperature Tafmax of low-temperature multiple temperature-changing alternating ageing or starting from the highest heating temperature Tafmax of low-temperature multiple temperature-changing alternating ageing and ending at the lowest heating temperature Tafmin of low-temperature multiple temperature-changing alternating ageing, n is more than or equal to 3 and less than or equal to 7, namely n is 3, 4, 5, 6 or 7.
In the invention, the total time of the multiple temperature-changing alternating ageing fully started at low temperature can be neither too short nor too long: if the time is too short, the alloy element strengthening phase can only reach limited aging precipitation capacity, quality, efficiency and the like; if the time length is too long, the aging capability, quality, efficiency and the like of the alloy element strengthening phase can reach a saturated or limit state.
In the invention, when the low-temperature multiple temperature-changing alternating ageing time is fully started according to the equal time method, the total heating time tau of the equal time method is fully started from the low-temperature multiple temperature-changing alternating ageing timeafNWith the 1 st and 2 nd stages of temperature increase agingHeating time tau in each stage of aging corresponding to heating temperature ranges of 3 rd stage, … … th stage and nth stageafnThe mathematical relationship of (a) is: tau isafN＝∑τafn＝∑τafN/N；
In the formula tauafNThe method is characterized in that the method is a uniform time method which is fully started from the total time of low-temperature multiple temperature-changing alternating aging heating for min or h; tau isafnHeating time in each stage of heating temperature interval corresponding to aging in 1 st stage, 2 nd stage, 3 rd stage, … …, and nth stage of heating temperature interval is tau/min or h/haf1、τaf2、τaf3、τaf4、τaf5、τaf6Or τaf7，τaf1＝τaf2＝τaf3＝τaf4＝τaf5＝τaf6Or τaf7(ii) a N is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7 (namely N is 3, 4, 5, 6 or 7); n is the number of the nth stage which is sufficiently started by low-temperature multiple temperature-changing alternating ageing heating, and n is more than or equal to 1 and less than or equal to 7 (namely n is 1, 2, 3, 4, 5, 6 or 7).
In the invention, when the time of low-temperature multiple temperature-changing alternating ageing is carried out according to the increasing time method, the total heating time tau of the increasing time method is fully started from the low-temperature multiple temperature-changing alternating ageingafNHeating time tau in each stage of aging corresponding to heating temperature intervals of 1 st, 2 nd, 3 rd, … …, and nth stages of heatingafnThe mathematical relationship of (a) is: tau isafN＝∑τafn＝∑[τaf1+(n–1)τaf0]；
In the formula tauafNThe method is characterized in that the method is a time increasing method which fully begins with the total time of low-temperature multiple temperature-changing alternating aging heating for min or h; n is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7 (namely N is 3, 4, 5, 6 or 7); tau isafnHeating time of each stage of low-temperature multiple temperature-changing alternating ageing is min/time or h/time, and is tauaf1、τaf2、τaf3、τaf4、τaf5、τaf6Or τaf7，τaf1＞τaf2＞τaf3＞τaf4＞τaf5＞τaf6Or > tauaf7(ii) a n is the number of nth stages which are sufficiently started by low-temperature multiple variable-temperature alternating aging heating, and n is more than or equal to 1 and less than or equal to 7 (namely n is 1, 2, 3, 4, 5, 6 or 7); tau isaf1Heating time in a first stage of low-temperature multiple temperature-changing alternating ageing is fully started for min/time or h/time; tau isaf0The heating time increases the grade difference for min/time or h/time and is the same and unchangeable specific numerical value.
In the invention, when the low-temperature multiple temperature-changing alternating ageing time is fully started according to the decreasing time method, the total heating time tau of the decreasing time method is fully started from the low-temperature multiple temperature-changing alternating ageing timeafNHeating time tau in each stage of aging corresponding to heating temperature intervals of 1 st, 2 nd, 3 rd, … …, and nth stages of heatingafnThe mathematical relationship of (a) is: tau isafN＝∑τafn＝∑[τaf1–(n–1)τaf0]；
In the formula tausfNThe time method is a decreasing time method which is fully started from the total time of low-temperature multiple temperature-changing alternating aging heating for min/time or h/time; n is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7 (namely N is 3, 4, 5, 6 or 7); tau isafnHeating time in each stage of heating temperature interval corresponding to aging in 1 st stage, 2 nd stage, 3 rd stage, … …, and nth stage of heating temperature interval is tau/min or h/haf1、τaf2、τaf3、τaf4、τaf5、τaf6Or τaf7，τaf1＜τaf2＜τaf3＜τaf4＜τaf5＜τaf6Or < tauaf7(ii) a n is the number of nth stages which are sufficiently started by low-temperature multiple variable-temperature alternating aging heating, and n is more than or equal to 1 and less than or equal to 7 (namely n is 1, 2, 3, 4, 5, 6 or 7); tau isaf1Heating for min/time or h/time in a first stage of low-temperature multiple-temperature-changing alternating ageing; tau isaf0Fully begins at low temperature for multiple times of temperature change and alternate agingThe thermal decrement time difference, min/time or h/time, is the same and unchanged specific numerical value.
In the invention, the final cooling mode of the second part which is fully started from low-temperature multiple temperature-changing alternating aging heat treatment is as follows: cooling in air at room temperature.
In the invention, the second part is fully started from a low-temperature multiple temperature-changing alternating aging heat treatment method, and the method comprises the following steps: comprises the following steps of 1 st fully starting from a low-temperature multiple-temperature-changing alternating aging process: the method specifically comprises the following steps that the first half part of the 1 st time is fully started from a low temperature to a high temperature non-variable temperature alternating aging process: firstly, heating and preserving the austenitic stainless steel at the lowest temperature of low-temperature multiple temperature-changing alternating ageing in a heating furnace within a specified time, then continuously and rapidly heating the austenitic stainless steel to the middle temperature of the low-temperature multiple temperature-changing alternating ageing for heating and preserving, and then continuously and rapidly heating the austenitic stainless steel to the highest temperature of final ageing for heating and preserving (the first half of the 1 st time is fully started at low temperature and ended at high temperature without temperature-changing alternating ageing), and then continuously the second half of the 1 st time is started at high temperature and ended at low-temperature multiple temperature-changing alternating ageing: firstly, continuously cooling the austenitic stainless steel from the highest temperature of low-temperature multiple temperature-changing alternating ageing to the middle temperature of multiple temperature-changing alternating ageing for heating and heat preservation in a heating furnace within a specified time, and then continuously cooling the austenitic stainless steel from the middle temperature of low-temperature multiple temperature-changing alternating ageing to the lowest temperature of low-temperature multiple temperature-changing alternating ageing for heating and heat preservation in the heating furnace within the specified time (the second half of the 1 st time is fully started from the high temperature and ends in the process of low-temperature multiple temperature-changing alternating ageing); after the 1 st time fully begins to the end of the low-temperature multiple temperature-changing alternating aging process, then the 2 nd time, the 3 rd time or the 4 th time temperature-changing alternating aging process is carried out again: carrying out multiple temperature-changing alternating ageing for 2 times, sequentially and reversely repeating the second half part of the 1 st time for 1 time (the end of the multiple temperature-changing alternating ageing for 2 times) in the high-temperature and low-temperature multiple temperature-changing alternating ageing process, or sequentially and reversely repeating the multiple temperature-changing alternating ageing for 2 times for 1 time (the end of the multiple temperature-changing alternating ageing for 3 times) in the 3 rd time, or sequentially and reversely repeating the multiple temperature-changing alternating ageing for 4 times for 1 time (the end of the multiple temperature-changing alternating ageing for 4 times); and after the 2 nd, 3 rd or 4 th time of the low-temperature multiple temperature-changing alternating ageing process is completely finished, finally, continuously cooling the austenitic stainless steel to room temperature by adopting a specific cooling mode (the second part of the process is completely finished in the low-temperature multiple temperature-changing alternating ageing heat treatment process).
According to the technical scheme, the invention can fundamentally solve the problems of poor quality stability, low qualified product rate, low hardness (or low mechanical property), poor consistency, long heating time, low efficiency, poor heating reliability of heat treatment equipment, low service life of high-temperature components, high cost and the like which cannot be solved by the traditional mainstream austenitic stainless steel technical method.
Although the invention is researched by taking the heat treatment method of austenitic stainless steel (the used heating equipment is the conventional box-type resistance heating furnace) as a research object, the invention is also applicable to heat treatment methods of other types of stainless steel, high-temperature alloy and the like (the heating equipment can also be selected from other types of resistance heating furnaces, high-medium and low-frequency heating furnaces, salt bath heating furnaces, gas-fuel oil heating furnaces, fluid particle heating furnaces, vacuum heating furnaces and the like); similarly, the method is also suitable for the heat treatment method related in the technical fields of hot working engineering such as austenitic stainless steel smelting, steel rolling, forging, heat treatment and the like related in steel mills and manufacturing plants; meanwhile, it should be noted that: it will be apparent to those skilled in the art that several arrangements, combinations, modifications, improvements (especially, the solution and aging heating temperature and time, and the cooling medium can be properly adjusted or changed according to the grade of austenitic stainless steel, the use performance, the heating equipment, etc.) without departing from the technical principle of the present invention, etc. should also be considered as the protection scope of the present invention.
Claims (10)
1. A full solid solution and multiple variable temperature alternate aging composite heat treatment method starting from low temperature is characterized by comprising the following steps:
performing a substantially solution heat treatment process, the substantially solution heat treatment process comprising: heating and heat preservation are carried out when the austenitic stainless steel is heated to the minimum temperature of full solid solution from room temperature within a specified time in a heating furnace, heating and heat preservation are carried out when the austenitic stainless steel is continuously heated to the intermediate solid solution temperature of full solid solution from the minimum temperature of full solid solution, heating and heat preservation are carried out when the austenitic stainless steel is continuously heated to the maximum temperature of full solid solution from the intermediate solid solution temperature of full solid solution, and finally cooling is carried out when the austenitic stainless steel is taken out of the furnace and is cooled from the maximum temperature of full solid solution to the minimum temperature of temperature-changing alternating ageing for multiple times by adopting a specific cooling mode;
after the full solid solution heat treatment is finished, performing full low-temperature multiple variable temperature alternating aging heat treatment, fully starting from low temperature to high temperature and fully starting from high temperature to low temperature multiple variable temperature alternating aging heat treatment, wherein the full solid solution heat treatment comprises the following steps of 1 st full low-temperature multiple variable temperature alternating aging process: the method specifically comprises the following steps that the first half part of the 1 st time is fully started from a low temperature to a high temperature non-variable temperature alternating aging process: firstly, cooling a first part of austenitic stainless steel which is fully dissolved in solution in a heating furnace within a specified time to a minimum temperature which is fully started from low-temperature multiple temperature-changing alternating ageing, then continuously heating and preserving the austenitic stainless steel to a middle temperature which is fully started from low-temperature multiple temperature-changing alternating ageing, then continuously heating and preserving the austenitic stainless steel to a maximum temperature which is fully started from low-temperature multiple temperature-changing alternating ageing, and then continuously heating the second half part of the 1 st time which is started from high temperature and ended from low-temperature multiple temperature-changing alternating ageing to obtain the austenitic stainless steel, wherein the temperature of the austenitic stainless steel is controlled by a temperature controller: firstly, continuously heating and preserving heat of austenitic stainless steel in a heating furnace from the highest temperature of low-temperature multiple-temperature-changing alternating ageing to the middle temperature of multiple-temperature-changing alternating ageing in a specified time, and then continuously heating and preserving heat of austenitic stainless steel in the heating furnace from the middle temperature of low-temperature multiple-temperature-changing alternating ageing to the lowest temperature of multiple-temperature-changing alternating ageing in the specified time; after the 1 st time fully begins to the end of the low-temperature multiple temperature-changing alternating aging process, then the 2 nd time, the 3 rd time or the 4 th time temperature-changing alternating aging process is carried out again: sequentially and reversely repeating the second half part of the 2 nd time in the 1 st time for 1 time in the high-temperature and low-temperature multiple temperature-changing and alternating ageing process, sequentially and reversely repeating the 3 rd time for 1 time in the 2 nd time temperature-changing and alternating ageing process, sequentially and reversely repeating the 4 th time for 1 time in the 3 rd time temperature-changing and alternating ageing process; and after the 2 nd, 3 rd or 4 th time of the low-temperature multiple temperature-changing alternating aging process is completely finished, cooling the austenitic stainless steel to room temperature by adopting a specific cooling mode.
2. The method for compound heat treatment of full solid solution and multiple temperature change and alternating aging from low temperature according to claim 1, wherein the total temperature change and alternating aging times fully started from the low temperature multiple temperature change and alternating aging heat treatment is 1 time, and each temperature change and alternating aging process at least comprises 1 temperature rise and 1 temperature fall at the same time.
3. The compound heat treatment method for full solid solution and multiple alternating aging at low temperature according to claim 1, characterized in that the multi-stage temperature rise temperature interval involved in the full solid solution and multiple alternating aging at low temperature is as follows: the method comprises a 1 st full multi-stage non-alternating temperature rise temperature interval: n is more than or equal to 3 and less than or equal to 7 from the lowest heating temperature interval Tafmin-1 of the full multi-stage heating and aging, n-2 middle heating temperature intervals Tafm-1 of the full multi-stage aging and finally n is more than or equal to n and less than or equal to 7 from the highest heating temperature interval Tafmin-1 of the full multi-stage aging; the 2 nd time, the 3 rd time or the 4 th time fully begins in a low-temperature multiple-time variable-temperature alternating heating aging temperature interval: the full heating and aging process is sequentially repeated, and the numerical values of the lowest temperature interval of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time of full starting at the low-temperature multiple temperature-changing alternating heating and aging are represented by the following relational expressions: tafmin-1 is more than Tafmin-2 is more than Tafmin-3 is more than Tafmin-4, and the numerical relation of the intermediate heating temperature interval in the full heating and aging process of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafm-1 is more than Tafm-2 is more than Tafm-3 is more than Tafm-4, the numerical value of the highest temperature interval of the temperature change and alternation and temperature rise aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time fully begins at the low temperature for a plurality of times is as follows: tafmax-1 > Tafmax-2 > Tafmax-3 > Tafmax-4; the temperature-raising aging temperature range is fully started from the low-temperature multiple-time temperature-changing alternating temperature-raising aging temperature range, and any one of a temperature-raising aging lowest heating temperature range, a temperature-raising aging middle heating temperature range and a temperature-raising aging highest temperature range is not repeated, and any one of a temperature-lowering aging lowest heating temperature range, a temperature-lowering aging middle heating temperature range and a temperature-lowering aging highest temperature range is not repeated.
4. The compound heat treatment method for full solid solution and multiple temperature-changing and alternating aging at low temperature according to claim 1, characterized in that the temperature range of the multi-stage temperature-reducing and aging, which is related to the multiple temperature-changing and alternating aging at low temperature, is fully started: the method comprises a 1 st full multi-stage non-alternating cooling aging temperature interval: n staged full multi-stage cooling and aging heating temperature intervals are started from a full multi-stage cooling and aging highest heating temperature interval Tafmax-1, sequentially pass through n-2 full multi-stage aging intermediate heating temperature intervals Tafm-1 and finally end to a full multi-stage aging lowest heating temperature interval Tafmin-1, and n is more than or equal to 3 and less than or equal to 7; the 2 nd time, the 3 rd time or the 4 th time fully begins in a low-temperature multiple-time variable-temperature alternating cooling aging temperature interval: the cooling and aging process is sequentially repeated, and the relation of the numerical values of the lowest temperature interval of the low-temperature multiple-time variable-temperature alternating cooling and aging at the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafmin-1 is more than Tafmin-2 is more than Tafmin-3 is more than Tafmin-4, and the numerical relation of the intermediate heating temperature interval of the temperature-changing alternating aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time is as follows: tafm-1 is more than Tafm-2 is more than Tafm-3 is more than Tafm-4, the numerical value of the highest temperature interval of the temperature-changing and alternating cooling aging of the 1 st time, the 2 nd time, the 3 rd time and the 4 th time fully begins at the low temperature for a plurality of times is as follows: tafmax-1 > Tafmax-2 > Tafmax-3 > Tafmax-4; the temperature-reducing aging temperature interval, the temperature-reducing aging intermediate heating temperature interval and the temperature-reducing aging highest temperature interval do not repeatedly occur in the low-temperature multiple-temperature-changing alternating temperature-reducing aging temperature interval, and the temperature-increasing aging minimum heating temperature interval, the temperature-increasing aging intermediate heating temperature interval and the temperature-increasing aging highest temperature interval do not repeatedly occur.
5. The compound heat treatment method for full solid solution and multiple alternating aging starting at low temperature according to claim 1, wherein the mathematical relationship between the minimum heating temperature Tafmin for full starting at low temperature multiple alternating aging and the minimum theoretical heating temperature Taftmin for aging is as follows: tafmin ═ Taftmin;
in the formula, Tafmin is the lowest heating temperature (DEG C) of the aging process which is fully started from low temperature multiple temperature change and alternation; taftmin is the minimum theoretical heating temperature of aging, DEG C.
6. The compound heat treatment method for full solid solution and multiple alternating aging at low temperature according to claim 1, wherein the mathematical relationship between the maximum heating temperature Tafmax of the multiple alternating aging at low temperature and the maximum theoretical heating temperature Taftmax of the aging is as follows: tafmax is Taftmax;
in the formula, Tafmin is the highest heating temperature (DEG C) of the aging process which is fully started from low temperature multiple temperature change and alternation; taftmin is the maximum theoretical heating temperature of aging at deg.C.
7. The compound heat treatment method for full solution and multiple alternating aging at low temperature according to claim 1, wherein the mathematical relationship between the intermediate heating temperature Tafm and the minimum heating temperature Tafmin and the maximum heating temperature Tafmax of aging at each stage of the full solution and multiple alternating aging at low temperature is as follows: tafm ═ Tafmin + ni(Tafmax–Tafmin)/(n–1)；
In the formula, Tafm is the intermediate heating temperature and DEG C of each stage of the low-temperature multiple temperature-changing alternating aging, and also is the stage from 2 nd to 2 nd of the low-temperature multiple temperature-changing alternating agingThe specific stage temperature of the 2 nd last stage; tafmin is the lowest heating temperature of alternating aging at low temperature for multiple times of temperature rise or temperature fall and temperature change, and is measured at the temperature of DEG C; n isiThe specific nth heating temperature interval from the 2 nd to the 2 nd last stages from low to high or from high to lowiNumber of stages, n being not less than 1iLess than or equal to 5; tafmax is the maximum heating temperature of alternating aging at low temperature for multiple times or at variable temperature; (Tafmax-Tafmin)/n is a specific constant value which fully begins at low temperature for multiple times of temperature rise or temperature fall and changes temperature, and changes the aging time to increase or decrease the temperature difference gradually; n is the total number of stages starting from the lowest temperature Tafmin of low-temperature multiple temperature-changing alternating ageing and ending at the highest heating temperature Tafmax of low-temperature multiple temperature-changing alternating ageing or starting from the highest heating temperature Tafmax of low-temperature multiple temperature-changing alternating ageing and ending at the lowest heating temperature Tafmin of low-temperature multiple temperature-changing alternating ageing, and n is more than or equal to 3 and less than or equal to 7.
8. The method for full solution and multiple variable temperature alternate aging combined heat treatment starting from low temperature according to claim 1, wherein when the full starting from low temperature multiple variable temperature alternate aging time is performed according to the equal time method, the equal time method is full starting from total heating time τ of low temperature multiple variable temperature alternate agingafNHeating time tau in each stage of aging corresponding to heating temperature intervals of 1 st, 2 nd, 3 rd, … …, and nth stages of heatingafnThe mathematical relationship of (a) is: tau isafN＝∑τafn＝∑τafN/N；
In the formula tauafNThe method is characterized in that the method is a uniform time method which is fully started from the total time of low-temperature multiple temperature-changing alternating aging heating for min or h; tau isafnHeating time in each stage of heating temperature interval corresponding to aging in 1 st stage, 2 nd stage, 3 rd stage, … …, and nth stage of heating temperature interval is tau/min or h/haf1、τaf2、τaf3、τaf4、τaf5、τaf6、τaf7，τaf1＝τaf2＝τaf3＝τaf4＝τaf5＝τaf6＝τaf7(ii) a N is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7; n is the number of nth stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and n is more than or equal to 1 and less than or equal to 7.
9. The method for full solution and multiple variable temperature alternate aging combined heat treatment starting from low temperature according to claim 1, wherein when the full starting from low temperature multiple variable temperature alternate aging time is performed according to the increasing time method, the increasing time method is full starting from total heating time tau of low temperature multiple variable temperature alternate agingafNHeating time tau in each stage of aging corresponding to heating temperature intervals of 1 st, 2 nd, 3 rd, … …, and nth stages of heatingafnThe mathematical relationship of (a) is:
τafN＝∑τafn＝∑[τaf1+(n–1)τaf0]
in the formula tauafNThe method is characterized in that the method is a time increasing method which fully begins with the total time of low-temperature multiple temperature-changing alternating aging heating for min or h; n is the total number of stages which are fully started from low-temperature multiple temperature-changing alternating aging heating, and is more than or equal to 3 and less than or equal to 7; tau isafnHeating time of each stage of low-temperature multiple temperature-changing alternating ageing is min/time or h/time, and is tauaf1、τaf2、τaf3、τaf4、τaf5、τaf6、τaf7，τaf1＞τaf2＞τaf3＞τaf4＞τaf5＞τaf6＞τaf7(ii) a n is the number of nth stages which are fully started from low-temperature multiple variable-temperature alternating aging heating, and n is more than or equal to 1 and less than or equal to 7; tau isaf1Heating time in a first stage of low-temperature multiple temperature-changing alternating ageing is fully started for min/time or h/time; tau isaf0The heating time increases the grade difference for min/time or h/time and is the same and unchangeable specific numerical value.
10. The method for fully solutionizing and starting from low-temperature multiple temperature swing alternate aging composite heat treatment according to claim 1, wherein the method for fully starting from low-temperature multiple temperature swing alternate aging heat treatment comprises the following processes: comprises the following steps of 1 st fully starting from a low-temperature multiple-temperature-changing alternating aging process: the method specifically comprises the following steps that the first half part of the 1 st time is fully started from a low temperature to a high temperature non-variable temperature alternating aging process: firstly, heating and preserving the austenitic stainless steel at the lowest temperature of low-temperature multiple temperature-changing alternating ageing in a heating furnace within a set time, then continuously and rapidly heating the austenitic stainless steel to the middle temperature of the low-temperature multiple temperature-changing alternating ageing for heating and preserving, then continuously and rapidly heating the austenitic stainless steel to the highest temperature of final ageing for heating and preserving, and then continuing the second half of the 1 st time, namely the process of beginning at high temperature and ending at low-temperature multiple temperature-changing alternating ageing: firstly, continuously cooling the austenitic stainless steel from the highest temperature of low-temperature multiple temperature-changing alternating ageing to the middle temperature of multiple temperature-changing alternating ageing for heating and heat preservation in a heating furnace within a specified time, and then continuously cooling the austenitic stainless steel from the middle temperature of low-temperature multiple temperature-changing alternating ageing to the lowest temperature of low-temperature multiple temperature-changing alternating ageing for heating and heat preservation in the heating furnace within the specified time; after the 1 st time fully begins to the end of the low-temperature multiple temperature-changing alternating aging process, then the 2 nd time, the 3 rd time or the 4 th time temperature-changing alternating aging process is carried out again: sequentially and reversely repeating the second half part of the 2 nd time in the 1 st time for 1 time in the high-temperature and low-temperature multiple temperature-changing and alternating ageing process, sequentially and reversely repeating the 3 rd time for 1 time in the 2 nd time temperature-changing and alternating ageing process, sequentially and reversely repeating the 4 th time for 1 time in the 3 rd time temperature-changing and alternating ageing process; and after the 2 nd, 3 rd or 4 th time of the low-temperature multiple temperature-changing alternating aging process is completely finished, finally, continuously cooling the austenitic stainless steel to room temperature by adopting a specific cooling mode.
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