CN115852128B - Method for eliminating mixed crystals at head of bolt made of cold-drawn GH4738 alloy - Google Patents
Method for eliminating mixed crystals at head of bolt made of cold-drawn GH4738 alloy Download PDFInfo
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- CN115852128B CN115852128B CN202211622396.4A CN202211622396A CN115852128B CN 115852128 B CN115852128 B CN 115852128B CN 202211622396 A CN202211622396 A CN 202211622396A CN 115852128 B CN115852128 B CN 115852128B
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Abstract
The invention belongs to the technical field of GH4738 alloy processing, and particularly relates to a method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy, which comprises the steps of annealing a bolt made of the GH4738 alloy after hot heading forming, preserving heat for 10-60min at 1000-1040 ℃, air-cooling, and then carrying out standard heat treatment. According to the invention, through carrying out annealing treatment after hot upsetting forming of the bolt, the distortion energy difference of a critical deformation area of the head of the bolt formed by hot upsetting is reduced, the grain size is controlled, the problem of mixed crystal structure of the head of the bolt made of cold-drawn GH4738 alloy is solved, the shape of a product is not required to be changed, the head material of the bolt is fully and statically recrystallized in the subsequent heat treatment process, the structure is further homogenized, and the grain size meets the standard requirement.
Description
Technical Field
The invention relates to a method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy, and belongs to the technical field of GH4738 alloy processing.
Background
The high-temperature alloy fastener has the characteristics of high temperature resistance, high strength, high fatigue resistance, high corrosion resistance, high reliability and the like, and is an important bearing connecting piece of an engine. The engine connecting structure is easy to generate fatigue cracks under a complex alternating load environment, and the safety of the whole engine is greatly threatened. The GH4738 alloy has high tensile strength and durability below 760 ℃, has good oxidation resistance below 870 ℃, and is particularly suitable for manufacturing high-end fasteners of engines. However, GH4738 alloy has large deformation resistance and narrow deformable temperature window, and belongs to the category of high-temperature alloy difficult to deform. In the hot forming process of the GH4738 alloy bolt, a thermal deformation dead zone exists in a region of about 2-5mm from the top in the center of the bolt head, the deformation of each micro region of the bolt head is different in the hot upsetting forming process, and the like, so that after the bolt head is treated according to a standard heat treatment system (solid solution-stabilization-aging), abnormal mixed crystal tissues (namely, uneven crystal grains, the grain size level difference is up to 4 levels or more) exist in the bolt head, coarse crystals with the grain size of 0-1.5 levels exist in the thermal deformation dead zone, the grain size of other regions is generally about 5.5 levels, and the occurrence of mixed crystals can cause adverse effects on the plasticity, fatigue, creep and durability of materials. After the existing molding process is adopted, the mixed crystal is treated according to a standard heat treatment process system, and mixed crystals are difficult to avoid. At present, a method for eliminating mixed crystals at the head of a bolt made of cold-drawn GH4738 alloy by a heat treatment technology does not exist.
Disclosure of Invention
The invention provides a method for eliminating mixed crystals at the head of a bolt made of cold-drawn GH4738 alloy, which aims at solving the problem that the head of the bolt has abnormal structures such as mixed crystals and the like, namely the granularity of the head of the bolt is uneven after the existing cold-drawn GH4738 alloy upsetting bolt is treated according to a standard heat treatment system (solid solution-stabilization-aging).
The technical scheme for solving the technical problems is as follows:
a method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy comprises the steps of carrying out annealing treatment on the bolt made of the GH4738 alloy after hot heading forming, keeping the annealing temperature at 1000-1040 ℃, preserving the heat for 10-60min, carrying out air cooling, and then carrying out standard heat treatment.
The deformation of the head of the bolt is different in the hot upsetting forming microscopic deformation, so that the distortion potential energy of the microscopic structures of different areas is different, and the crystal grain growth kinetic energy of different areas is different when the solution treatment is carried out according to a standard system, so that the area, from the top to about 2-5mm, of the center of the head of the bolt in the critical deformation area is abnormal and grown, and a coarse crystal grain structure is formed. The invention carries out annealing treatment before standard heat treatment, proper annealing reduces distortion potential energy of the bolt head part and eliminates the critical deformation area of the bolt head part, thereby improving uniformity of grain structure after solution treatment and solving the problem of mixed crystal structure. In the selection of the annealing temperature, if the annealing temperature is too low, the effect of reducing distortion potential energy cannot be achieved, if the annealing temperature is too high, the annealing treatment is equivalent to solution treatment, coarse grain structures are directly generated during the annealing treatment, and the problem of mixed crystal structures cannot be solved, so that the annealing temperature interval adopted by the invention is 1000-1040 ℃, the distortion potential energy of the microstructure of the bolt head can be effectively reduced, the critical deformation area is eliminated, and the mixed crystal of the bolt head made of the cold-drawn GH4738 alloy is eliminated.
Based on the technical scheme, the invention can also make the following improvements:
further, the standard heat treatment includes solution treatment, stabilization treatment, and aging treatment.
Further, the temperature of the solution treatment is 1040-1080 ℃, the temperature is kept for 1-4 hours, and the air cooling is performed.
Further, the temperature of the stabilization treatment is 845+/-10 ℃, the temperature is kept for 1-4 hours, and the air cooling is performed.
Further, the temperature of the aging treatment is 760+/-10 ℃, the temperature is kept for 16+/-1 h, and the air cooling is performed.
The invention has the advantages that:
according to the invention, the deformation energy difference of a critical deformation area of the head of the bolt formed by hot upsetting is reduced by carrying out annealing treatment after the hot upsetting of the bolt is formed, and the head material of the bolt is fully and statically recrystallized in the subsequent standard heat treatment process, so that the structure is homogenized, the grain size meets the standard requirement, and the problem of mixed crystal structure of the head of the bolt made of cold-drawn GH4738 alloy is solved.
Drawings
FIG. 1 is a photograph of a head metallographic structure of a bolt made of GH4738 alloy of comparative example 1, which has been subjected to standard heat treatment without annealing;
fig. 2 is a photograph of a head metallographic structure after forming a GH4738 alloy bolt by heading;
FIG. 3 is a photograph showing a metallographic structure of a head portion of a bolt made of GH4738 alloy according to example 1 of the present invention after annealing;
FIG. 4 is a photograph showing a metallographic structure of a head portion of a bolt made of GH4738 alloy, which has been annealed and subjected to a standard heat treatment in accordance with example 1 of the present invention;
FIG. 5 is a photograph showing a metallographic structure of a head portion of a bolt made of GH4738 alloy according to example 2 of the present invention after annealing;
fig. 6 is a photograph showing a metallographic structure of a head portion of a bolt made of GH4738 alloy according to example 2 of the present invention after annealing and standard heat treatment.
Detailed Description
The principles and features of the present invention are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
Bolt raw material selection: the bolt raw material is selected from cold-drawn GH4738 alloy raw materials, the cold-drawn raw materials are subjected to solid solution and stabilization treatment, the average grain size is 2-6 grades, no obvious coarse and fine strips exist, grains larger than 1 grade are not allowed to exist, and the grain size difference is smaller than 3 grades.
Selecting the hot heading temperature of a bolt: the bolt adopts a hot heading forming mode, and the hot heading temperature is in the range of 1050-1150 ℃. The metallographic structure of the head of the bolt after hot upsetting forming is photographed, the result of the metallographic structure photograph is shown in fig. 2, the upset crystal grains are elliptic structures, the grain size is about 8-9 levels, the deformed structures have larger distortion potential energy, and the internal structures are in an unstable state and cannot be directly used. The existing processing method is that crystal grains are restored into stable equiaxial structures through solution treatment, and meanwhile, the crystal grains are properly grown in the solution treatment until the grain size meets the product specification requirement. And then, after subsequent stabilization and aging treatment, ensuring that the performance indexes such as the product hardness and the like meet the standard requirements (see figure 1 and comparative example 1).
Example 1
The method for eliminating mixed crystals at the head of the bolt made of the cold-drawn GH4738 alloy comprises the following steps:
the GH4738 alloy bolt is annealed at 1000 ℃, kept for 30min, then air-cooled, and subjected to standard heat treatment (solution treatment, stabilization treatment, aging treatment).
The temperature of the solution treatment is 1060 ℃, the heat preservation is carried out for 3 hours, and the air cooling is carried out; the temperature of the stabilization treatment is 845 ℃, the temperature is kept for 3 hours, and the air cooling is carried out; the aging treatment temperature is 760 ℃, the heat preservation is carried out for 16 hours, and the air cooling is carried out.
Photographing a metallographic structure of the bolt head of the bolt made of the GH4738 alloy of the embodiment after annealing treatment, and taking a photograph to see FIG. 3; the metallographic structure of the bolt head portion of the bolt made of GH4738 alloy of this example after annealing and standard heat treatment is photographed, and the photograph is shown in FIG. 4.
The grain size of the head of the bolt made of the cold-drawn GH4738 alloy is evaluated according to GB/T6394 metal average grain size measurement method, and the grain size of the head of the bolt made of the cold-drawn GH4738 alloy treated by the method of the embodiment is about 5-5.5 level, and the grains are uniform. Therefore, the head structure of the bolt made of the cold-drawn GH4738 alloy treated by the method disclosed by the embodiment has uniform grain size, and meets the standard requirement.
Comparative example 1
And directly carrying out standard heat treatment on the bolt after cold-drawn GH4738 alloy hot heading forming, namely carrying out solution treatment, stabilization treatment and aging treatment.
The metallographic structure of the bolt head directly subjected to standard heat treatment after hot upsetting forming is photographed, the result of the metallographic structure photograph is shown in figure 1, and it can be seen from figure 1 that the bolt head directly subjected to standard heat treatment after hot upsetting forming has mixed crystal structure, the grain size grade is up to 4 grade and above, wherein 98% -99% of grains have average grain size of 5-6 grade, and 1% -2% have grains of 1.5 grade or above
Example 2
Unlike example 1, the annealing temperature in this example was 1020℃and the temperature was kept for 10 minutes.
The other components are the same as those in embodiment 1, and will not be described again.
Photographing a metallographic structure of the bolt head of the bolt made of the GH4738 alloy of the embodiment after annealing treatment, and taking a photograph as shown in FIG. 5; the metallographic structure of the bolt head portion of the bolt made of GH4738 alloy of this example after annealing and standard heat treatment is photographed, and the photograph is shown in FIG. 6.
The grain size of the head of the bolt made of the cold-drawn GH4738 alloy is evaluated according to GB/T6394 metal average grain size measurement method, and the grain size of the head of the bolt made of the cold-drawn GH4738 alloy treated by the method of the embodiment is about 5.5-6, and the grains are uniform. Therefore, the head structure of the bolt made of the cold-drawn GH4738 alloy treated by the method disclosed by the embodiment has uniform grain size, and meets the standard requirement.
Claims (4)
1. A method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy is characterized by carrying out annealing treatment on the bolt made of the GH4738 alloy after hot heading forming, wherein the annealing temperature is 1000-1040 ℃, the heat preservation is carried out for 10-60min, the air cooling is carried out, and then standard heat treatment is carried out, and the standard heat treatment comprises solution treatment, stabilization treatment and aging treatment.
2. The method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy according to claim 1, wherein the solution treatment temperature is 1040-1080 ℃, the heat preservation is carried out for 1-4 h, and the bolt is air-cooled.
3. The method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy according to claim 1, wherein the temperature of the stabilizing treatment is 845 ℃ + -10 ℃, the temperature is kept for 1-4 h, and the bolt is air-cooled.
4. The method for eliminating mixed crystals at the head of a bolt made of a cold-drawn GH4738 alloy according to claim 1, wherein the aging treatment is performed at 760 ℃ +/-10 ℃, the temperature is kept for 16 h+/-1 h, and the bolt is air-cooled.
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| CN202211622396.4A CN115852128B (en) | 2022-12-16 | 2022-12-16 | Method for eliminating mixed crystals at head of bolt made of cold-drawn GH4738 alloy |
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| CN202211622396.4A CN115852128B (en) | 2022-12-16 | 2022-12-16 | Method for eliminating mixed crystals at head of bolt made of cold-drawn GH4738 alloy |
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| CN115852128B true CN115852128B (en) | 2023-09-19 |
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| CN117344253B (en) * | 2023-12-04 | 2024-02-23 | 东方蓝天钛金科技有限公司 | Method for eliminating coarse crystals of solid solution state Waspaloy alloy bolt rod part |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111041393A (en) * | 2019-12-24 | 2020-04-21 | 陕西宏远航空锻造有限责任公司 | Method for refining grains of high-temperature solid solution nickel-based superalloy |
| WO2021174727A1 (en) * | 2020-03-02 | 2021-09-10 | 北京钢研高纳科技股份有限公司 | Method for preparing nickel-based deformed high-temperature alloy turbine disk forging for high temperature use |
| CN113560481A (en) * | 2021-07-30 | 2021-10-29 | 内蒙古工业大学 | Hot working process of GH4738 nickel-based high-temperature alloy |
| CN114561527A (en) * | 2022-02-24 | 2022-05-31 | 上海交通大学 | Active control method for grain size of solution treatment of 316H steel forging |
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| KR102136455B1 (en) * | 2018-03-16 | 2020-07-21 | 서울대학교산학협력단 | Self-healable trip superalloys and manufacturing method for the same |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111041393A (en) * | 2019-12-24 | 2020-04-21 | 陕西宏远航空锻造有限责任公司 | Method for refining grains of high-temperature solid solution nickel-based superalloy |
| WO2021174727A1 (en) * | 2020-03-02 | 2021-09-10 | 北京钢研高纳科技股份有限公司 | Method for preparing nickel-based deformed high-temperature alloy turbine disk forging for high temperature use |
| CN113560481A (en) * | 2021-07-30 | 2021-10-29 | 内蒙古工业大学 | Hot working process of GH4738 nickel-based high-temperature alloy |
| CN114561527A (en) * | 2022-02-24 | 2022-05-31 | 上海交通大学 | Active control method for grain size of solution treatment of 316H steel forging |
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