CN115852128A - Method for eliminating mixed crystals at head of cold-drawn GH4738 alloy bolt - Google Patents
Method for eliminating mixed crystals at head of cold-drawn GH4738 alloy bolt Download PDFInfo
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- CN115852128A CN115852128A CN202211622396.4A CN202211622396A CN115852128A CN 115852128 A CN115852128 A CN 115852128A CN 202211622396 A CN202211622396 A CN 202211622396A CN 115852128 A CN115852128 A CN 115852128A
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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 part of a cold-drawn GH4738 alloy bolt. According to the invention, annealing treatment is carried out after the bolt is subjected to hot heading forming, so that the distortion energy difference of a critical deformation area of the bolt head subjected to hot heading forming is reduced, the grain size is controlled, the problem of mixed crystal structure of the bolt head made of cold-drawn GH4738 alloy is solved, the shape of a product is not required to be changed, the bolt head material is subjected to full static recrystallization in the subsequent heat treatment process, the structure is 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 part of a bolt made of GH4738 alloy in a cold-drawn state, 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 great threat is caused to the safety of the whole engine. The GH4738 alloy has high tensile strength and endurance strength below 760 ℃ and good oxidation resistance below 870 ℃, and is particularly suitable for manufacturing high-end fasteners of engines. However, the GH4738 alloy has large deformation resistance and narrow deformable temperature window, and belongs to the category of high-temperature alloys difficult to deform. In the hot forming process of the bolt made of GH4738 alloy, a hot deformation dead zone exists in a region about 2-5mm from the top in the center of the bolt head, the problems of different deformation amounts of various micro regions of the bolt head and the like occur in the hot heading forming process, so that after the bolt head is treated according to a standard heat treatment system (solid solution-stabilization-aging), a mixed crystal abnormal structure (namely, non-uniform crystal grains with the grain size grade difference of 4 or above) exists in the bolt head, coarse crystals with the grain size of 0-1.5 grade exist in the hot deformation dead zone, the grain size of other regions is generally about 5.5 grade, and the occurrence of mixed crystals can cause adverse effects on the plasticity, fatigue, creep and durability of the material. The existing molding process is adopted and then treated according to a standard heat treatment process system, so that the occurrence of mixed crystals is difficult to avoid. At present, no method for eliminating mixed crystals of bolt heads made of GH4738 alloy in a cold-drawn state by a heat treatment technology exists.
Disclosure of Invention
The invention provides a method for eliminating mixed crystals of a cold-drawn GH4738 alloy bolt head, aiming at the problem that after the existing cold-drawn GH4738 alloy upset bolt is treated according to a standard heat treatment system (solid solution-stabilization-aging), abnormal structures such as mixed crystals exist on the bolt head, namely the grain size of the bolt head is not uniform.
The technical scheme for solving the technical problems is as follows:
a method for eliminating mixed crystals at the head part of a bolt made of GH4738 alloy in a cold-drawn state comprises the steps of annealing the hot-upset formed bolt made of GH4738 alloy at 1000-1040 ℃, preserving heat for 10-60min, air cooling and then carrying out standard heat treatment.
Due to the fact that the deformation potential energy of microstructures in different areas is different due to different hot heading forming microcosmic deformation quantities of the bolt head, and when solution treatment is carried out according to a standard system subsequently, the grain growth kinetic energy of the different areas is different, the abnormal growth of the structure occurs in an area which is located in the critical deformation quantity area and is about 2-5mm from the top of the center of the bolt head, and a coarse grain structure is formed. According to the invention, annealing treatment is carried out before standard heat treatment, proper annealing reduces the distortion potential energy of the bolt head part, and eliminates the critical deformation area of the bolt head part, thereby improving the uniformity of the crystal grain structure after solution treatment and solving the problem of mixed crystal structure. In the aspect of selecting the annealing temperature, if the annealing temperature is too low, the effect of reducing the distortion potential energy cannot be achieved, if the temperature is too high, the annealing treatment is equivalent to solution treatment, a coarse grain structure directly appears during the annealing treatment, and the problem of mixed crystal structure cannot be solved, so that the annealing temperature range adopted by the invention is 1000-1040 ℃, the distortion potential energy of the microstructure of the bolt head can be more effectively reduced by annealing treatment in the temperature range, the critical deformation area is eliminated, and the mixed crystal of the bolt head made of the GH4738 alloy in a cold-drawn state is eliminated.
On the basis of 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 h, and air cooling is carried out.
Further, the temperature of the stabilizing treatment is 845 +/-10 ℃, the temperature is kept for 1-4 h, and air cooling is carried out.
Further, the temperature of the aging treatment is 760 +/-10 ℃, the temperature is kept for 16 +/-1 h, and air cooling is carried out.
The invention has the advantages that:
according to the invention, annealing treatment is carried out after the bolt is subjected to hot heading forming, so that the distortion energy difference of a critical deformation area of the bolt head subjected to hot heading forming is reduced, the bolt head material is subjected to full static recrystallization in the subsequent standard heat treatment process, the structure is homogenized, the grain size meets the standard requirement, and the problem of mixed crystal structure of the bolt head made of the GH4738 alloy in a cold-drawn state is solved.
Drawings
FIG. 1 is a photograph of the metallographic structure of the head of a bolt made of GH4738 alloy according to comparative example 1, which was subjected to standard heat treatment without annealing;
FIG. 2 is a photograph of the metallographic structure of the head of a bolt made of GH4738 alloy after being upset and formed;
FIG. 3 is a photograph of the metallographic structure of the head of a bolt made of GH4738 alloy according to example 1 of the present invention after annealing;
FIG. 4 is a photograph of the metallographic structure of the head of a bolt made of GH4738 alloy according to example 1 of the present invention after annealing and standard heat treatment;
FIG. 5 is a photograph of the metallographic structure of the head of a bolt made of GH4738 alloy according to example 2 of the present invention after annealing;
FIG. 6 is a photograph of the metallographic structure of the head 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 this invention are described below in conjunction with the following drawings, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
Selecting raw materials of the bolt: the bolt raw material is a cold-drawn GH4738 alloy raw material, after the cold-drawn raw material is subjected to solid solution and stabilization treatment, the average grain size is 2-6 levels, no obvious coarse and fine strips exist, more than 1 level of grains are not allowed to exist, and the grain size difference is less than 3 levels.
Selecting the hot heading temperature of the bolt: the bolt is formed by hot heading at 1050-1150 deg.c. The metallographic structure of the bolt head subjected to hot heading forming is photographed, the result of the metallographic structure photograph is shown in fig. 2, and it can be seen from fig. 2 that the headed crystal grains are elliptical structures, the grain size is about 8-9 grades, large distortion potential energy is generated in the deformed structures, and the internal structures are in an unstable state and cannot be directly used. The existing processing method is to recover the crystal grains into a stable equiaxial structure through solution treatment, and the crystal grains grow properly in the solution treatment until the grain size meets the product specification requirement. And then, subsequent stabilization and aging treatment are carried out to ensure that the performance indexes such as product hardness and the like meet the standard requirements (see figure 1 and comparative example 1).
Example 1
A method for eliminating mixed crystals at the head part of a cold-drawn GH4738 alloy bolt comprises the following steps:
annealing GH4738 alloy bolt at 1000 deg.C for 30min, air cooling, and standard heat treatment (solid solution treatment, stabilization treatment, and aging treatment).
The temperature of the solution treatment is 1060 ℃, the temperature is kept for 3 hours, and air cooling is carried out; the temperature of the stabilization treatment is 845 ℃, the heat preservation is carried out for 3 hours, and air cooling is carried out; the temperature of the aging treatment is 760 ℃, the temperature is kept for 16h, and air cooling is carried out.
The metallographic structure of the head of the bolt made of the GH4738 alloy of the present embodiment after annealing treatment was photographed, and the photograph is shown in fig. 3; the metallographic structure of the bolt head of the bolt made of the GH4738 alloy of the present example after annealing and standard heat treatment was photographed, and the photograph is shown in fig. 4.
The grain size of the bolt head made of the GH4738 alloy in the cold-drawn state is evaluated according to GB/T6394 Metal average grain size measurement, and the grain size of the bolt head made of the GH4738 alloy in the cold-drawn state treated by the method of the embodiment is about 5-5.5 grades, and the crystal grains are uniform. Therefore, the bolt head structure made of the GH4738 alloy in the cold-drawn state treated by the method of the embodiment has uniform grain size and meets the standard requirement.
Comparative example 1
And directly carrying out standard heat treatment, namely carrying out solid solution treatment, stabilizing treatment and aging treatment on the bolt formed by hot heading of the cold-drawn GH4738 alloy.
The metallographic structure of the bolt head directly subjected to standard heat treatment after hot heading forming is photographed, the result of the metallographic structure photograph is shown in fig. 1, it can be seen from fig. 1 that the bolt head directly subjected to standard heat treatment after hot heading forming has a mixed crystal structure, the grain size grade difference reaches 4 grades and above, wherein the average grain size of 98% -99% of grains is 5-6 grades, and 1% -2% of grains with the grain size of 1.5 grades or larger are present
Example 2
Unlike example 1, the annealing temperature in this example was 1020 ℃ and the temperature was maintained for 10min.
The rest is the same as embodiment 1 and is not described again.
The metallographic structure of the head of the bolt made of the GH4738 alloy of the present embodiment after annealing treatment was photographed, and the photograph is shown in fig. 5; the metallographic structure of the bolt head of the bolt made of the GH4738 alloy of the present example after annealing and standard heat treatment was photographed, and the photograph is shown in fig. 6.
The grain size of the bolt head made of the GH4738 alloy in the cold-drawn state is evaluated according to GB/T6394 Metal average grain size measurement, and the grain size of the bolt head made of the GH4738 alloy in the cold-drawn state treated by the method of the embodiment is about 5.5-6, and the crystal grains are uniform. Therefore, the bolt head structure made of the GH4738 alloy in the cold-drawn state treated by the method of the embodiment has uniform grain size and meets the standard requirement.
Claims (5)
1. A method for eliminating mixed crystals at the head part of a bolt made of GH4738 alloy in a cold-drawn state is characterized in that annealing treatment is carried out on the bolt made of the GH4738 alloy after hot heading forming, the annealing temperature is 1000-1040 ℃, the temperature is kept for 10-60min, air cooling is carried out, and then standard heat treatment is carried out.
2. The method of eliminating mixed crystals in the heads of cold-drawn GH4738 alloy bolts according to claim 1, wherein said standard heat treatments comprise solution treatment, stabilization treatment and aging treatment.
3. The method for eliminating the mixed crystals at the head part of the cold-drawn GH4738 alloy bolt according to claim 2, wherein the temperature of the solution treatment is 1040-1080 ℃, the temperature is kept for 1-4 h, and the bolt is cooled in air.
4. The method for eliminating mixed crystals on the head part of the cold-drawn GH4738 alloy bolt according to claim 2, wherein the temperature of the stabilizing treatment is 845 ℃ +/-10 ℃, the temperature is kept for 1-4 h, and the air cooling is carried out.
5. The method for eliminating mixed crystals on the head part of a cold-drawn GH4738 alloy bolt according to claim 2, wherein the temperature of the aging treatment is 760 ℃ ± 10 ℃, the temperature is kept for 16h ± 1h, and the bolt is cooled in air.
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| Application Number | Priority Date | Filing Date | Title |
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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 CN115852128B (en) | 2023-09-19 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117344253A (en) * | 2023-12-04 | 2024-01-05 | 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 |
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| KR20190109008A (en) * | 2018-03-16 | 2019-09-25 | 서울대학교산학협력단 | Self-healable trip superalloys and manufacturing method for the same |
| 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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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20190109008A (en) * | 2018-03-16 | 2019-09-25 | 서울대학교산학협력단 | Self-healable trip superalloys and manufacturing method for the same |
| 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 |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117344253A (en) * | 2023-12-04 | 2024-01-05 | 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 |
| 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 |
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