CN113943904A - Heat treatment process for improving high-temperature tensile plasticity of heat-resistant alloy - Google Patents

Heat treatment process for improving high-temperature tensile plasticity of heat-resistant alloy Download PDF

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CN113943904A
CN113943904A CN202111212095.XA CN202111212095A CN113943904A CN 113943904 A CN113943904 A CN 113943904A CN 202111212095 A CN202111212095 A CN 202111212095A CN 113943904 A CN113943904 A CN 113943904A
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temperature
resistant alloy
cooling
treatment process
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CN113943904B (en
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张鹏
杨征
严靖博
袁勇
谷月峰
杨珍
周永莉
鲁金涛
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Xian Thermal Power Research Institute Co Ltd
Huaneng Power International Inc
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Huaneng Power International Inc
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
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    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Abstract

The invention discloses a heat treatment process for improving high-temperature tensile plasticity of a heat-resistant alloy, which comprises the following steps of: 1) heating the deformed heat-resistant alloy to be 100-150 ℃ below the dissolution temperature of the second phase of the crystal boundary, carrying out solution treatment for 30-45 min, and then cooling; 2) heating the heat-resistant alloy treated in the step 1) to a temperature higher than the complete austenitizing temperature by 50 ℃, and cooling after aging treatment. The invention controls the morphology of the alloy structure through simple heat treatment, and improves the high-temperature elongation by more than 70 percent under the condition of ensuring that the yield strength is not lost in the high-temperature stretching at 650 ℃.

Description

Heat treatment process for improving high-temperature tensile plasticity of heat-resistant alloy
Technical Field
The invention relates to the field of heat treatment of heat-resistant alloys, in particular to a heat treatment process for improving high-temperature tensile plasticity of a heat-resistant alloy.
Background
Global warming has become one of the major problems in the world today. In order to cope with global warming and improve human living environment, it is necessary to reduce the emission of greenhouse gases such as carbon dioxide and carbon monoxide. The method for improving the parameters of the thermal power generating unit is one of effective ways for reducing the emission of carbon dioxide and carbon monoxide and improving the thermal efficiency. But the parameters of the thermal power generating unit are improved, and the method has higher requirements on the material selection of key high-temperature parts of the boiler.
The key high-temperature parts of the boiler not only require the heat-resistant alloy to have higher high-temperature strength, smoke corrosion resistance and steam oxidation corrosion resistance, but also have better high-temperature plasticity. Boiler key parts bear great stress and higher temperature, if the heat-resisting alloy has higher high temperature tensile plasticity, can in time discover the plasticity damage district among the daily maintenance process of unit, change, avoid taking place the inefficacy suddenly, cause the loss of personnel and property, the security and the economic nature of the operation of the thermal power unit of improvement.
If the heat-resistant alloy matrix is mainly a martensite matrix, the alloy has higher dislocation density, good strength at high temperature and slightly poor plasticity. In the past, it has been common to increase the tensile plasticity of the alloy by increasing the austenite content of the alloy structure. However, austenite has higher plasticity but not high strength relative to martensite. Therefore, increasing the high temperature tensile plasticity of the heat resistant alloy by increasing the austenite content tends to result in a decrease in high temperature yield strength.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a heat treatment process for improving the high-temperature tensile plasticity of a heat-resistant alloy, which can improve the high-temperature tensile plasticity by more than 70% on the premise of ensuring no loss of the high-temperature tensile yield strength at 650 ℃, and provides guarantee for the high-temperature safe operation of a thermal power generating unit.
The purpose of the invention is realized by the following technical scheme:
a heat treatment process for improving high-temperature tensile plasticity of a heat-resistant alloy comprises the following steps:
1) heating the deformed heat-resistant alloy to be 100-150 ℃ below the dissolution temperature of the second phase of the crystal boundary, carrying out solution treatment for 30-45 min, and then cooling;
2) heating the heat-resistant alloy treated in the step 1) to a temperature higher than the complete austenitizing temperature by 50 ℃, and cooling after aging treatment.
The invention is further improved in that the deformation-state heat-resistant alloy comprises the following components in percentage by mass: c: 0.05-0.08%, Cr: 11.5-15%, Ni: 0.9-1.6%, Mn: 5-10%, Si: 0.2-0.5%, B: 0.003-0.007%, Mo: 0.5-1.5%, W: 4-6%, Cu: less than or equal to 1.2 percent, Al: less than or equal to 1.5 percent and the balance of Fe.
The further improvement of the invention is that the deformation-state heat-resistant alloy is heated to 100-150 ℃ below the dissolution temperature of the second phase of the grain boundary at a heating rate of not more than 15 ℃/min.
The further improvement of the invention is that the heat-resistant alloy treated in the step 1) is slowly heated to be within 50 ℃ above the complete austenitizing temperature at a heating rate of less than 10 ℃/min.
The method is further improved in that the time of the aging treatment in the step 2) is 4-12 h.
The invention is further improved in that in the step 1) and the step 2), cooling is carried out in a water cooling mode.
The invention is further improved in that the temperature of the cooling liquid adopted by the water cooling is not higher than 30 ℃.
The further improvement of the invention is that the high-temperature elongation of the heat-resistant alloy treated by the step 1 and the step 2) is improved by more than 70 percent at 650 ℃.
Compared with the prior art, the invention has the following beneficial technical effects:
in the invention, the temperature is heated to be 100-150 ℃ below the second phase dissolving temperature of the crystal boundary, the heat preservation time of the solution treatment is controlled to be 30-45 min, and then the solution treatment is cooled to room temperature. The solution treatment temperature is controlled to ensure the solubility of the matrix to elements and activate the diffusion capacity of the elements. The control of the solution treatment time is to dissolve the precipitated phase precipitated in the crystal grains in the hot working process into the matrix, promote the formation of discontinuously distributed granular precipitated phase at the two-phase interface of austenite and martensite in the cooling process, improve the strength of the phase interface, prevent the alloy from cracking along the grain boundary and ensure that the heat-resistant alloy has good tensile plasticity.
Further, the slow heating is carried out at a temperature rise rate of not higher than 15 ℃/min in the invention, so as to reduce the thermal stress in the heating process.
Further, water cooling is carried out by a cooling medium with the temperature not higher than 30 ℃, so that part of austenite in the alloy is transformed into martensite, a large number of quenching twin crystals are formed in austenite grains, and nucleation points are provided for precipitation of a precipitated phase in the aging process.
Further, in the present invention, the steel sheet is slowly heated to complete austenitization A at a temperature rise rate of not more than 10 ℃/minc3And keeping the temperature within 50 ℃ above, preserving the heat for 4-12 h, carrying out aging treatment, and cooling to room temperature by water after the aging treatment is finished. The temperature of the aging treatment is controlled to ensure the nucleation rate of precipitated phases in an austenite matrix and the growth driving force of the precipitated phases, so as to ensure that the precipitated phases in the austenite matrix are grownA large number of dispersed precipitated phases are precipitated. The aging time is controlled to control the size of the precipitated phases and to ensure that the size of the precipitated phases in the austenitic matrix is not more than 1 μm. Martensite is a BCT (tetragonal body centered) structure with high density dislocations with higher strength relative to an austenitic FCC (face centered cubic) structure. Through aging treatment, fine precipitated phases are precipitated in an austenite matrix, the austenite strength is improved, the martensite and the austenite phases have good performance matching, and the strength is not lost under the condition that the alloy has good plasticity in the deformation process. The structure of the heat-resistant alloy obtained by the process has the properties of no loss of tensile yield strength at 650 ℃ and improvement of high-temperature tensile elongation by more than 70 percent, and is one of effective ways of ensuring no loss of alloy strength and improving high-temperature tensile plasticity.
Drawings
FIG. 1 is a block diagram of an tissue processed by step 1 of the method of example 1 of the present invention;
FIG. 2 is a view of the structure after heat treatment according to the method of example 1 of the present invention;
FIG. 3 is a view of the structure after heat treatment according to the method of example 2 of the present invention;
FIG. 4 is a view of the structure after heat treatment according to comparative example 1 of the present invention;
FIG. 5 is a structural view of a structure after heat treatment by the method of comparative example 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, which are provided by way of illustration and not by way of limitation.
The invention relates to a heat treatment process for improving high-temperature tensile plasticity of a heat-resistant alloy, which comprises the following steps of:
1) taking a deformation state heat-resistant alloy, wherein the deformation state heat-resistant alloy comprises the following components in percentage by mass: c: 0.05-0.08%, Cr: 11.5-15%, Ni: 0.9-1.6%, Mn: 5-10%, Si: 0.2-0.5%, B: 0.003-0.007%, Mo: 0.5-1.5%, W: 4-6%, Cu: less than or equal to 1.2 percent, Al: less than or equal to 1.5 percent, and the balance being Fe;
2) heating the deformed heat-resistant alloy to a temperature 100-150 ℃ below the second phase dissolution temperature of the crystal boundary at a heating rate of not more than 15 ℃/min, preserving the heat for 30-45 min, carrying out solid solution treatment, and then cooling the alloy to room temperature by water, so as to ensure that second phase particles are discontinuously precipitated in a blocky form at the two-phase crystal boundary interface of austenite and martensite, cover more than 40% of the two-phase crystal boundary, and have an average size of 0.5-4 mu m;
3) slowly heating the heat-resistant alloy treated in the step 2) to complete austenitization A at a heating rate of less than 10 ℃/minc3The temperature is higher than 50 ℃, the temperature is kept for 4-12 h, aging treatment is carried out, and cooling is carried out to room temperature after the aging treatment is finished, so that a large amount of strengthening phases are separated out from austenite grains, the average size is not more than 1 mu m, and the volume fraction is not lower than 5%;
4) and cooling by adopting a water cooling mode, wherein the temperature of cooling liquid adopted by water cooling is not higher than 30 ℃.
The following are specific examples.
TABLE 1 chemical composition of heat-resistant alloy used in examples 1-2 and comparative examples 1-2 below
Figure BDA0003309248490000041
Example 1
Step 1: taking a deformation state heat-resistant alloy with the composition of the heat-resistant alloy 1 in the table 1, and carrying out grain boundary second phase precipitation temperature and complete austenitization A on the heat-resistant alloyc3The temperature was measured by the laboratory instrument and was 1102 ℃ and 700.6 ℃ respectively. The heat-resistant alloy is heated to 1000 ℃ at the heating rate of 15 ℃ per min, the temperature is kept for 30min, the solution treatment is completed, then the water cooling is carried out to the room temperature, the temperature of a cooling medium adopted by the water cooling is not higher than 30 ℃, a sample after the solution treatment is obtained, and the structure and the appearance of the sample after the solution treatment are shown in figure 1. It can be seen from fig. 1 that the austenite and martensite grain boundaries of the heat-resistant alloy after the treatment of step 1 precipitate massive discontinuous precipitated phases, and the average size of the precipitated phases does not exceed 4 μm.
Step 2: heating the sample after the solution treatment to 750 ℃ at the temperature rising rate of 10 ℃ per min, preserving the temperature for 12h, finishing the aging treatment, then cooling with water, wherein the temperature of a cooling medium is not higher than 30 ℃, and the obtained structure is shown in figure 2. As can be seen from fig. 2, the microstructure of the heat-resistant alloy after the step 2 treatment mainly consists of two phases of martensite and austenite. Wherein the martensite is in a lath shape, and the volume percentage is not lower than 80%; the austenite grains are long-strip-shaped, the size is not more than 10 mu m, the volume number is 10-20%, and a large amount of fine precipitated phases are precipitated in the austenite grains, the size is not more than 1 mu m, and the volume fraction is not less than 5%.
Example 2
Step 1: a heat-resistant alloy having a transformation form of heat-resistant alloy 2 shown in Table 1 was prepared, and the temperature of precipitation of the second phase in the grain boundary and the temperature of complete austenitization A were measured for the heat-resistant alloyc3The temperature was measured by the laboratory instrument and was 1108 ℃ and 706.4 ℃ respectively. The heat-resistant alloy is heated to 990 ℃ at the heating rate of 15 ℃/min, the temperature is kept for 30min, the solid solution treatment is completed, then the water cooling is carried out to the room temperature, and the temperature of a cooling medium adopted by the water cooling is not higher than 30 ℃. After the treatment of the step 1, blocky phases are discontinuously precipitated at austenite and martensite crystal boundaries, and the average size of the blocky phases is not more than 4 mu m.
Step 2: heating the sample after the solution treatment to 750 ℃ at the heating rate of 10 ℃/mim, preserving the heat for 12h, finishing the aging treatment, and then cooling with water, wherein the temperature of a cooling medium is not higher than 30 ℃. The structure of the solution-treated sample is shown in fig. 3, and it can be seen from fig. 3 that the microstructure of the heat-resistant alloy treated in step 2 mainly consists of two phases, namely martensite and austenite. Wherein the martensite is in a lath shape, and the volume percentage is not lower than 80%; the austenite grains are long-strip-shaped, the size is not more than 10 mu m, the volume number is 10-20%, and a large amount of fine precipitated phases are precipitated in the austenite grains, the size is not more than 1 mu m, and the volume fraction is not less than 5%.
Comparative example 1
Taking a deformation state heat-resistant alloy with the components of the heat-resistant alloy 1 in the table 1, putting the heat-resistant alloy into a high-temperature heat treatment furnace for solution treatment, wherein the temperature of the solution treatment is 1100 ℃, the heat preservation time is 30min, and cooling the heat-resistant alloy to room temperature by water. And then placing the alloy sample after the solution treatment into a heat treatment furnace to heat to 750 ℃, preserving the heat for 12 hours, and cooling the alloy sample to room temperature by water to obtain a structure shown in figure 4.
Comparative example 2
Taking a deformation state heat-resistant alloy with the composition of the heat-resistant alloy 2 in the table 1, putting the heat-resistant alloy into a high-temperature heat treatment furnace for solution treatment, wherein the temperature of the solution treatment is 1100 ℃, keeping the temperature for 30min, and cooling to room temperature by water. And then placing the alloy sample after the solution treatment into a heat treatment furnace to heat to 710 ℃, preserving the heat for 8 hours, and cooling the alloy sample to room temperature by water, as shown in figure 5.
The alloys of examples 1-2 and comparative examples 1-2 were tested for their high temperature tensile plasticity at 650 ℃ and strength according to the present invention, and the results are shown in Table 2.
TABLE 2 high temperature tensile plasticity and Strength test results for alloys of examples 1-2 and comparative examples 1-2
Figure BDA0003309248490000061
As can be seen from Table 2, the high-temperature elongation of the heat-resistant alloy is improved by 70% or more without loss of yield strength at a high temperature of 650 ℃ after heat treatment.
Example 3
Step 1: the morphotropic heat-resistant alloy comprises the following components in percentage by weight: 0.05%, Cr: 11.5%, Ni: 1.6%, Mn: 10%, Si: 0.3%, B: 0.007%, Mo: 1.5%, W: 4%, Cu: 1.2%, Al: 1% and the balance Fe.
The measured precipitation temperature of the second phase of the alloy grain boundary is 1106 ℃, and the second phase is completely austenitized Ac3The temperature was 705 ℃. The heat-resistant alloy is heated to 998 ℃ at the heating rate of 15 ℃/min, the temperature is kept for 30min, the solid solution treatment is completed, then the water cooling is carried out to the room temperature, and the temperature of a cooling medium adopted by the water cooling is not higher than 30 ℃. After solution treatment, the block phase is discontinuously precipitated at the austenite and martensite crystal boundary, and the average size of the block phase is not more than 4 mu m.
Step 2: heating the sample after the solution treatment to 760 ℃ at the heating rate of 10 ℃/min, preserving the temperature for 12h to finish the aging treatment, and then cooling with water, wherein the temperature of a cooling medium is not higher than 30 ℃.
The microstructure of the heat-resistant alloy treated in the step 2 mainly comprises martensite and austenite, wherein the martensite is in a lath shape, and the volume percentage is not lower than 80%; the austenite grains are long-strip-shaped, the size is not more than 10 mu m, the volume number is 10-20%, and a large amount of fine precipitated phases are precipitated in the austenite grains, the size is not more than 1 mu m, and the volume fraction is not less than 5%. Under the condition of no loss of yield strength at high temperature of 650 ℃, the elongation at high temperature is improved by more than 70 percent.
Example 4
Step 1: the morphotropic heat-resistant alloy comprises the following components in percentage by weight: 0.08%, Cr: 12%, Ni: 1.3%, Mn: 5%, Si: 0.4%, B: 0.003%, Mo: 1%, W: 5%, Cu: 0.5%, Al: 1.5 percent and the balance of Fe.
The measured precipitation temperature of the alloy grain boundary second phase is 1110 ℃, and the alloy grain boundary second phase is completely austenitized Ac3The temperature was 716 ℃. Heating the heat-resistant alloy to 1010 ℃ at a heating rate of 15 ℃/min, preserving heat for 30min to finish solution treatment, and then cooling the heat-resistant alloy to room temperature by water, wherein the temperature of a cooling medium adopted by the water cooling is not higher than 30 ℃. After solution treatment, the block phase is discontinuously precipitated at the austenite and martensite crystal boundary, and the average size of the block phase is not more than 4 mu m.
Step 2: heating the sample subjected to the solution treatment to 720 ℃ at the heating rate of 10 ℃/min, preserving the temperature for 12h to finish the aging treatment, and then cooling with water, wherein the temperature of a cooling medium is not higher than 30 ℃.
The microstructure of the heat-resistant alloy treated in the step 2 mainly comprises two phases of martensite and austenite, wherein the martensite is in a lath shape, and the volume percentage is not lower than 80%; the austenite grains are long-strip-shaped, the size is not more than 10 mu m, the volume number is 10-20%, and a large amount of fine precipitated phases are precipitated in the austenite grains, the size is not more than 1 mu m, and the volume fraction is not less than 5%. Under the condition of no loss of yield strength at high temperature of 650 ℃, the elongation at high temperature is improved by more than 70 percent.
Example 5
Step 1: the morphotropic heat-resistant alloy comprises the following components in percentage by weight: 0.07%, Cr: 13%, Ni: 1.2%, Mn: 7%, Si: 0.5%, B: 0.004%, Mo: 0.5%, W: 6%, Cu: 0.1%, Al: 0.1 percent and the balance of Fe.
The measured precipitation temperature of the alloy grain boundary second phase is 1107 ℃, and the alloy grain boundary second phase is completely austenitized Ac3The temperature was 708 ℃. Heating the heat-resistant alloy to 1005 ℃ at a heating rate of 15 ℃/min, preserving heat for 30min to finish solution treatment, and then cooling the heat-resistant alloy to room temperature by water, wherein the temperature of a cooling medium adopted by the water cooling is not higher than 30 ℃. After solution treatment, the block phase is discontinuously precipitated at the austenite and martensite crystal boundary, and the average size of the block phase is not more than 4 mu m.
Step 2: heating the sample after the solution treatment to 740 ℃ at the heating rate of 10 ℃/min, preserving the heat for 12h to finish the aging treatment, and then cooling with water, wherein the temperature of a cooling medium is not higher than 30 ℃.
The microstructure of the heat-resistant alloy treated in the step 2 mainly comprises two phases of martensite and austenite. Wherein the martensite is in a lath shape, and the volume percentage is not lower than 80%; the austenite grains are long-strip-shaped, the size is not more than 10 mu m, the volume number is 10-20%, and a large amount of fine precipitated phases are precipitated in the austenite grains, the size is not more than 1 mu m, and the volume fraction is not less than 5%. Under the condition of no loss of yield strength at high temperature of 650 ℃, the elongation at high temperature is improved by more than 70 percent.
Example 6
Step 1: the deformation-state heat-resistant alloy comprises the following components in percentage by weight: 0.06%, Cr: 15%, Ni: 0.9%, Mn: 8%, Si: 0.2%, B: 0.005%, Mo: 1.2%, W: 6 percent and the balance of Fe.
The measured precipitation temperature of the alloy grain boundary second phase is 1120 ℃, and the alloy grain boundary second phase is completely austenitized Ac3The temperature was 721 ℃. Heating the heat-resistant alloy to 1020 ℃ at the heating rate of 15 ℃/min, preserving the heat for 30min to finish the solution treatment, and then cooling the heat-resistant alloy to room temperature by water, wherein the temperature of a cooling medium adopted by the water cooling is not higher than 30 ℃. After solution treatment, the block phase is discontinuously precipitated at the austenite and martensite crystal boundary, and the average size of the block phase is not more than 4 mu m.
Step 2: heating the sample subjected to solution treatment to 725 ℃ at the temperature rising rate of 10 ℃ per min, preserving heat for 12 hours, finishing aging treatment, and then cooling with water, wherein the temperature of a cooling medium is not higher than 30 ℃.
The microstructure of the heat-resistant alloy mainly consists of martensite and austenite after the step 2. The martensite is in a lath shape, and the volume percentage is not lower than 80%; the austenite grains are long-strip-shaped, the size is not more than 10 mu m, the volume number is 10-20%, and a large amount of fine precipitated phases are precipitated in the austenite grains, the size is not more than 1 mu m, and the volume fraction is not less than 5%. Under the condition of no loss of yield strength at high temperature of 650 ℃, the elongation at high temperature is improved by more than 70 percent.

Claims (8)

1. A heat treatment process for improving high-temperature tensile plasticity of a heat-resistant alloy is characterized by comprising the following steps of:
1) heating the deformed heat-resistant alloy to be 100-150 ℃ below the dissolution temperature of the second phase of the crystal boundary, carrying out solution treatment for 30-45 min, and then cooling;
2) heating the heat-resistant alloy treated in the step 1) to a temperature higher than the complete austenitizing temperature by 50 ℃, and cooling after aging treatment.
2. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 1, wherein the heat-resistant alloy in a deformed state comprises the following components in percentage by mass: c: 0.05-0.08%, Cr: 11.5-15%, Ni: 0.9-1.6%, Mn: 5-10%, Si: 0.2-0.5%, B: 0.003-0.007%, Mo: 0.5-1.5%, W: 4-6%, Cu: less than or equal to 1.2 percent, Al: less than or equal to 1.5 percent and the balance of Fe.
3. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 1, wherein the deformed heat-resistant alloy is heated to a temperature 100-150 ℃ below the dissolution temperature of the second phase of the grain boundary at a heating rate of not more than 15 ℃/min.
4. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 1, wherein the heat-resistant alloy treated in the step 1) is slowly heated to a temperature higher than the complete austenitizing temperature by 50 ℃ at a heating rate of less than 10 ℃/min.
5. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 1, wherein the time for the aging treatment in the step 2) is 4-12 hours.
6. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 1, wherein in the step 1) and the step 2), cooling is performed in a water cooling mode.
7. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 6, wherein the temperature of the cooling liquid for water cooling is not higher than 30 ℃.
8. The heat treatment process for improving the high-temperature tensile plasticity of the heat-resistant alloy according to claim 1, wherein the high-temperature elongation of the heat-resistant alloy treated in the steps 1 and 2) is improved by more than 70% at 650 ℃.
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CN104046891A (en) * 2013-03-13 2014-09-17 香港城市大学 Nanometer intermetallic compound-reinforced superhigh strength ferritic steel and manufacturing method thereof
JP2017166004A (en) * 2016-03-15 2017-09-21 山陽特殊製鋼株式会社 Austenitic heat resistant steel excellent in processability, high temperature strength and toughness after aging
CN108396223A (en) * 2018-03-29 2018-08-14 东北大学 A kind of super austenitic stainless steel and its alloying component optimum design method

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Publication number Priority date Publication date Assignee Title
US20020110476A1 (en) * 2000-12-14 2002-08-15 Maziasz Philip J. Heat and corrosion resistant cast stainless steels with improved high temperature strength and ductility
CN104046891A (en) * 2013-03-13 2014-09-17 香港城市大学 Nanometer intermetallic compound-reinforced superhigh strength ferritic steel and manufacturing method thereof
JP2017166004A (en) * 2016-03-15 2017-09-21 山陽特殊製鋼株式会社 Austenitic heat resistant steel excellent in processability, high temperature strength and toughness after aging
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