阅读说明：本技术 一种对大尺寸gh4738合金锻件进行快速时效的热处理工艺 (Heat treatment process for carrying out rapid aging on large-size GH4738 alloy forging ) 是由 郑磊 刘红亮 赵鑫 董建 孟晔 于 2021-07-14 设计创作，主要内容包括：本发明公开了一种对大尺寸GH4738合金锻件进行快速时效的热处理工艺,属于镍基高温合金热处理的技术领域。该工艺首先将大尺寸GH4738合金锻件进行固溶处理,并采用先炉冷后空冷的方式冷却；然后将其在加热炉中进行时效处理,时效处理温度740-760℃,保温时间4-8h,取出后空冷。本发明通过优化固溶处理之后合金的冷速,搭配短时间时效处理,促使GH4738合金基体中形成了弥散且均匀分布的γ′相。本发明处理工艺在提升合金锻件室温下强度均匀性方面具有意想不到的效果。其中室温下锻件边缘与心部区域对应的抗拉强度差异由40MPa左右降低到了15MPa以内,屈服强度差异由50MPa左右降低到15MPa以内。同时,与传统时效处理相比本发明热处理工艺大大缩短了时效处理时间,提高了生产效率、降低了生产成本,具有重要的生产应用价值。(The invention discloses a heat treatment process for carrying out rapid aging on a large-size GH4738 alloy forging, belonging to the technical field of heat treatment of nickel-based high-temperature alloys. The process comprises the steps of firstly, carrying out solution treatment on a large-size GH4738 alloy forging, and cooling by adopting a mode of furnace cooling first and then air cooling; then the material is subjected to aging treatment in a heating furnace, the aging treatment temperature is 740 and 760 ℃, the heat preservation time is 4-8h, and the material is taken out and then cooled in air. According to the invention, by optimizing the cooling rate of the alloy after the solution treatment and matching with short-time aging treatment, dispersed and uniformly distributed gamma' phase is formed in the GH4738 alloy matrix. The treatment process has an unexpected effect on improving the strength uniformity of the alloy forging at room temperature. Wherein the corresponding tensile strength difference between the edge of the forging and the core region at room temperature is reduced to within 15MPa from about 40MPa, and the yield strength difference is reduced to within 15MPa from about 50 MPa. Meanwhile, compared with the traditional aging treatment, the heat treatment process greatly shortens the aging treatment time, improves the production efficiency, reduces the production cost and has important production and application values.)

1. A heat treatment process for carrying out rapid aging on a large-size GH4738 alloy forging is characterized by comprising the following steps:

1) putting the large-size GH4738 alloy forging into a heating furnace for solution treatment: heating the heating furnace to 810-840 ℃ at the heating rate of 3-8 ℃/min, and preserving the heat for 30-60 min; then raising the temperature to 960-; then heating to 1010-1030 ℃ at the heating rate of 3-6 ℃/min, and preserving the heat for 30-90 min; then cooling is carried out;

2) placing the GH4738 alloy forging subjected to the solution treatment in the step 1) into a heating furnace for aging treatment: heating the heating furnace to 690 and 720 ℃ at the heating rate of 3-8 ℃/min, and preserving the heat for 30-60 min; then the temperature is raised to 740 and 760 ℃ at the heating rate of 3-8 ℃/min, and the temperature is kept for 4-8h and then cooled, thus finishing the aging treatment.

2. The heat treatment process for rapidly aging large-size GH4738 alloy forgings according to claim 1, wherein the heat treatment process comprises the following steps: step 1), after the solution treatment is finished, controlling the cooling rate of a heating furnace within the range of 100-150 ℃/min by adopting an air cooling method; and cooling the alloy forging below 500 ℃ out of the furnace and air cooling.

3. The heat treatment process for rapidly aging large-size GH4738 alloy forgings according to claim 1, wherein the heat treatment process comprises the following steps: and 2) the cooling mode after the aging treatment is discharging and air cooling.

Technical Field

The invention relates to the technical field of nickel-based high-temperature alloy heat treatment, in particular to a heat treatment process for rapidly aging a large-size GH4738 alloy forging.

Background

High temperature alloys, also known as heat resistant alloys or superalloys, have excellent mechanical properties and stability in high temperature environments. Wherein GH4738 is a Ni-Cr-Co based precipitation hardening type deformation high-temperature alloy, has good plastic deformation capacity at high temperature, has higher strength and anti-fatigue and anti-corrosion performances at the high temperature of 760-870 ℃, and is widely applied in the fields of aviation and energy at present.

In many applications, the GH4738 alloy is widely used for manufacturing forged parts such as large-size turbine disks and the like due to good processing plasticity and stable structure performance. The flue gas turbine is a prime mover which takes flue gas as a working medium and converts heat energy and pressure energy of the flue gas into mechanical energy. At present, the flue gas turbine is widely applied in the field of petrochemical industry, and is particularly applied to a regenerated flue gas energy recovery system of a vulcanization catalytic cracking unit of a petroleum refinery. Due to the special structural design requirements, a large amount of large-size GH4738 nickel-base superalloy forging turbine discs are required, because the components are complex and severe in use working conditions and are required to have strong stress corrosion resistance and toughness.

The GH4738 alloy is precipitated primarily by the gamma prime phase to strengthen the alloy matrix. In order to obtain the best performance, the alloy forging needs to be subjected to heat treatment before use to optimize the distribution form of a precipitation phase so as to achieve the aim of improving the alloy performance. The gamma ' phase is used as a main precipitated phase and a strengthening phase of a strengthening alloy matrix, the shape, the size and the distribution of the gamma ' phase obviously influence the mechanical property of the alloy, and the form and the distribution of the gamma ' phase can be changed by controlling the heat treatment process parameters, so that the potential of the alloy can be further exerted.

At present, a solid solution and aging heat treatment method is usually adopted for GH4738 alloy forgings in a forging state to improve and adjust the mechanical properties of the GH4738 alloy forgings. GH4738 alloy specified in the high-temperature alloy manual is cooled in an oil cooling mode after solution treatment, and the subsequent aging treatment process is 845 ℃/4h +760 ℃/16h, which is also called a standard double aging process. However, it should be noted that, for a large-size GH4738 alloy forging, especially a large-size forged turbine disk with a diameter greater than 1000mm and a thickness greater than 200mm, it is difficult to completely inhibit the precipitation growth of the γ 'phase even by oil cooling after the solution treatment, resulting in a large difference in the γ' phase content between the edge and the core of the forging after the solution treatment. Subsequent aging treatment cannot eliminate the structural difference, and finally the alloy forging body has large strength fluctuation and low mechanical property index qualification rate. In addition, the existing aging treatment time is long (the total time of two periods of aging treatment is up to 20 hours), the production period is long, the energy consumption is high, and the efficiency is low.

The current research on large-size GH4738 alloy forgings mainly focuses on the processing technology of the forgings, for example, a patent (CN 105177478A) proposes a cogging method of a GH4738 high-temperature alloy large ingot; the patent (patent number: CN103341586A) proposes a forming method for realizing GH4738 nickel-base superalloy turbine disks, but the research on the heat treatment process of formed forgings is less. Therefore, the rapid aging heat treatment process suitable for the large-size GH4738 alloy forge piece needs to be developed, the mechanical property uniformity of the alloy is improved, the aging treatment time is greatly shortened, the production efficiency is improved, and the cost is reduced.

Disclosure of Invention

The invention aims to provide a heat treatment process for rapidly aging a large-size GH4738 alloy forging aiming at the prior technical problems, and the process utilizes short-time aging treatment to promote the GH4738 alloy forging matrix to form dispersed and uniformly distributed gamma' phases while improving the production efficiency and reducing the cost, so that the strength uniformity of the alloy can be obviously improved.

The invention relates to a heat treatment process for carrying out rapid aging on a large-size GH4738 alloy forging, which is characterized by comprising the following steps of:

1) putting the large-size GH4738 alloy forging into a heating furnace for solution treatment: heating the heating furnace to 810-840 ℃ at the heating rate of 3-8 ℃/min, and preserving the heat for 30-60 min; then raising the temperature to 960-; then heating to 1010-1030 ℃ at the heating rate of 3-6 ℃/min, and preserving the heat for 30-90 min; then cooling is carried out;

2) placing the GH4738 alloy forging subjected to the solution treatment in the step 1) into a heating furnace for aging treatment: heating the heating furnace to 690 and 720 ℃ at the heating rate of 3-8 ℃/min, and preserving the heat for 30-60 min; then the temperature is raised to 740 and 760 ℃ at the heating rate of 3-8 ℃/min, and the temperature is kept for 4-8h and then cooled, thus finishing the aging treatment.

Further, after the solution treatment in the step 1) is finished, the heating furnace adopts an air cooling method to control the cooling rate within the range of 100-150 ℃/min; and cooling the alloy forging below 500 ℃ out of the furnace and air cooling.

Further, the cooling mode after the aging treatment in the step 2) is furnace discharging and air cooling.

The invention provides a heat treatment process for carrying out rapid aging on a large-size GH4738 alloy forging, which has unexpected effects on improving the uniformity of the structure and the mechanical property of the alloy forging.

Compared with the prior art, the invention has the beneficial effects that:

1. aiming at the characteristic that the alloy forging has larger size, the heat treatment process adopts graded heating before solid solution and aging treatment, so that the temperature rise rate of the alloy is reduced and the thermal stress of the alloy forging after heat treatment is reduced while the alloy is uniformly heated, and the heat treatment process is particularly suitable for large-size alloy forgings.

2. According to the invention, by optimizing the cooling rate of the alloy after the solution treatment and matching with the short-time aging treatment, dispersed and uniformly distributed gamma' phase is formed in the GH4738 alloy matrix, and the method has an unexpected effect on improving the strength uniformity of the alloy. Wherein the corresponding tensile strength difference between the edge of the forging and the core region at room temperature is reduced to within 15MPa from about 40MPa, and the yield strength difference is reduced to within 15MPa from about 50 MPa.

3. Compared with the traditional aging treatment, the heat treatment process greatly shortens the aging treatment time, improves the production efficiency, reduces the production cost and has important production and application values.

Drawings

FIG. 1 is a schematic view of the heat treatment process of the present invention.

FIG. 2 is the microstructure of the edge of the GH4738 alloy forging after solution + aging treatment of example 1.

FIG. 3 shows the microstructure of the core of the GH4738 alloy forging after solution treatment and aging treatment in example 1.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention. The specification of the GH4738 alloy forging in the embodiment of the invention isThe ingredients are shown in the following table.

GH4738 alloy forging compositions in Table 1 examples

Composition (I)	C	Cr	Co	Mo	Ti	Al	Zr	B	Ni
										Content wt. -%)	0.06	19.40	14.65	4.65	3.10	1.52	0.05	0.007	Balance of

Example 1

1) Putting the large-size GH4738 alloy forging into a heating furnace for solution treatment: heating the heating furnace to 830 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 40 min; then heating to 960 deg.C at a heating rate of 8 deg.C/min, and maintaining for 50 min; then heating to 1020 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 60 min; and then introducing air into the heating furnace, cooling to below 500 ℃ at the speed of 110-.

2) Placing the GH4738 alloy forging subjected to the solution treatment in the step 1) into a heating furnace for aging treatment: heating the heating furnace to 700 ℃ at the heating rate of 5 ℃/min, and preserving heat for 40 min; then heating to 750 ℃ at the heating rate of 6 ℃/min, preserving the heat for 6 hours, taking out and air-cooling to the room temperature.

Fig. 2 and 3 are gamma' phase distribution diagrams of the edge and the center of the alloy forging subjected to solid solution and aging treatment respectively, and it can be seen that the structural difference is small.

Comparative example 1

The difference from the embodiment 1 is that:

after the solution treatment, cooling the alloy forging to room temperature in an oil cooling mode; then the alloy forging in a solution treatment state is treated by adopting a traditional standard double-aging process: heating to 845 ℃ in a heating furnace, preserving heat for 4 hours, taking out, and then cooling to room temperature in air; then putting the mixture into a heating furnace to heat to 760 ℃, preserving heat for 16h, taking out the mixture and then cooling the mixture to room temperature in air.

Example 2

1) Putting the large-size GH4738 alloy forging into a heating furnace for solution treatment: heating the heating furnace to 820 ℃ at the heating rate of 6 ℃/min, and keeping the temperature for 50 min; heating to 970 ℃ at the heating rate of 5 ℃/min, and preserving heat for 40 min; then heating to 1030 ℃ at the heating rate of 3 ℃/min, and preserving heat for 40 min; and then introducing air into the heating furnace, cooling to below 500 ℃ at the speed of 130-.

2) Placing the GH4738 alloy forging subjected to the solution treatment in the step 1) into a heating furnace for aging treatment: heating the heating furnace to 710 ℃ at the heating rate of 6 ℃/min, and keeping the temperature for 30 min; then raising the temperature to 760 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 8h, taking out and air-cooling to room temperature.

The results of the room temperature tensile test of the alloy forgings treated by the heat treatment processes of examples 1-2 and comparative example 1 are shown in table 2.

TABLE 2 results of tensile and hardness test at room temperature for GH4738 alloys after heat treatment of examples 1-2 and comparative example 1

In summary, the embodiment of the invention provides a method for rapidly aging a large-size GH4738 alloy forging, wherein the alloy forging after solution treatment is cooled by a furnace cooling and then air cooling mode, and then is directly subjected to short-time aging treatment. The aging process in the heat treatment process not only is well matched with the solution treatment process, but also can greatly improve the production efficiency and reduce the production cost. The test results of multiple groups of mechanical properties show that the strength uniformity of the alloy is obviously improved by adopting the optimized process treatment. Wherein the corresponding tensile strength difference between the edge of the forging and the core region at room temperature is reduced to within 15MPa from about 40MPa, and the yield strength difference is reduced to within 15MPa from about 50 MPa.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and all equivalent flow changes made by the present invention, or direct or indirect application to other related technical fields, should be covered within the protection scope of the present invention.