Gradient heat treatment process for reducing residual stress of GH4169 alloy part in aging state

Abstract

The invention belongs to the field of heat treatment of high-temperature alloy parts, and particularly relates to a heat treatment method. An existing conventional destressing heat treatment process of charging at the furnace temperature below 400 DEG C, heating to the temperature of 540-560 DEG C at any speed / heat preservation for 2-4 h / air cooling is adjusted into a gradient heat treatment process of charging at the room temperature of a heating furnace, heating to the first gradient of 600-620 DEG C along with the furnace at the speed of (50 + / -10) DEG C / h and heat preservation for 2-4 h, furnace cooling to the second gradient of 500-550 DEG C at the speed of (50 + / -10) DEG C / h and heat preservation for 2-4 h. According to the method, after the aging-state GH4169 alloy part is subjected to heat treatment, the residual stress level of the aging-state GH4169 alloy part is reduced by more than 50% compared with that of a conventional stress relief annealing process, so that the deformation tendency and degree of the part in the subsequent machining and using process are further reduced, and the manufacturing qualification rate of the part is increased.

Description

Technical Field

[0001] The invention belongs to the field of heat treatment of high-temperature alloy parts, and in particular relates to a gradient heat treatment process for reducing residual stress of GH4169 alloy parts in an aging state. Background Art

[0002] GH4169 alloy is widely used in aerospace engine parts, including discs, shafts, casings and rings. The high performance and high stability requirements of aerospace engines put forward stringent indicators for the performance and size of GH4169 alloy parts. Therefore, in the processing of GH4169 alloy parts, stress relief annealing heat treatment process is usually arranged to reduce the residual stress of the parts under a certain processing state, reduce the deformation degree of the parts in the subsequent processing and use process, and improve the dimensional accuracy of the parts.

[0003] GH4169 is an aging-strengthening alloy, and its aging system is "720℃±10℃, heat preservation for 8h, furnace cooling to 620℃±10℃, heat preservation for 8h, air cooling". The alloy precipitates different types, sizes and quantities of second phases (γ′ and γ′′) during the heat preservation and cooling process at the aging temperature, which plays a role in precipitation strengthening. In the current conventional stress relief annealing heat treatment process, in order to avoid a significant impact on the precipitation phase and corresponding mechanical properties of the GH4169 alloy (especially in the solid solution state), the process adopted is "charging the furnace at a furnace temperature below 400℃, heating at any rate to 540℃~560℃, heat preservation for 2h~4h, air cooling", and the selected temperature is far from the aging temperature of 620℃. In the actual processing and stress detection process, it was found that the surface stress reduction of the parts before and after stress relief annealing was 200MPa~300MPa, and the maximum stress level still reached -300MPa, and the stress values ​​of different parts of the parts fluctuated greatly, and some parts still had a large degree of deformation. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides a gradient heat treatment process for reducing the residual stress of GH4169 alloy parts in an aged state.

[0005] The technical solution of the present invention is: A gradient heat treatment process for reducing residual stress of GH4169 alloy parts in an aged state, comprising the following steps; Step (1) Select a high-precision heat treatment furnace to ensure that the actual temperature fluctuation range of the parts is within the requirements; Step (2) arranges a stress relief gradient heat treatment in the process of machining a large amount of metal and the excess is basically uniform, specifically: Step (2.1) Load the parts into the heating furnace at room temperature and heat them to a first gradient temperature of 600°C to 620°C at a rate of (50±10)°C / h, and keep them at that temperature for 2-4 hours; After the first gradient temperature stage of step (2.2) is completed, the parts are cooled in the furnace at a rate of (50±10)℃ / h to a second gradient temperature of 500℃~550℃ and kept at this temperature for 1-2 hours; After the second temperature gradient stage in step (2.3) is completed, the parts are taken out of the heating furnace and placed in the air to cool to room temperature.

[0006] Furthermore, the above-mentioned gradient heat treatment process for reducing residual stress of GH4169 alloy parts in an aged state has a preferred embodiment in which the temperature range of the heating furnace in step (1) is below 800°C, and the temperature tolerance is not greater than ±10°C, so as to achieve precise control of the heating and furnace cooling rates.

[0007] Advantages and beneficial effects of the present invention: The gradient heat treatment process in the present invention can make the maximum reduction of residual stress of parts before and after heat treatment reach 600MPa, and the average reduction is close to 380MPa. The residual stress level of the parts after gradient heat treatment reaches below -150MPa, and the residual stress reduction effect is improved by about 1 times compared with conventional stress relief heat treatment. The substantial reduction in the residual stress level reduces the tendency and degree of deformation of the parts during subsequent processing and use, and significantly improves the dimensional accuracy and stability of the parts during processing. At the same time, since the strengthening phase of the GH4169 alloy has been fully precipitated after aging, practice has proved that the method of the present invention will not cause significant changes in the organization and mechanical properties of the aged GH4169 alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is the gradient heat treatment process of the present invention; Figure 2 is the surface residual stress value of GH4169 parts under different heat treatment processes. DETAILED DESCRIPTION

[0009] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention.

[0010] A gradient heat treatment process for reducing residual stress of GH4169 alloy parts in an aged state, wherein the gradient heat treatment process is shown in FIG. Figure 1 shown. Example

[0011] This embodiment takes the aged GH4169 alloy disc parts as an example, and the gradient heat treatment process for reducing the residual stress thereof includes the following steps: Step (1) Select a high-precision heat treatment heating furnace to ensure the actual temperature fluctuation range requirements of the parts, specifically, the temperature range of the heating furnace is below 800°C, the temperature tolerance is not greater than ±10°C, and the heating and furnace cooling rates are precisely controlled; Step (2) arranges a stress relief gradient heat treatment in the process of machining a large amount of metal and the excess is basically uniform, specifically: Step (2.1) Load the parts into the heating furnace at room temperature and heat them to a first gradient temperature of 620°C at a rate of 50°C / h, and keep them at that temperature for 4 hours; After the first gradient temperature stage of step (2.2) is completed, the parts are cooled in the furnace at a rate of 50°C / h to a second gradient temperature of 550°C and kept at this temperature for 2 hours; After the second temperature gradient stage in step (2.3) is completed, the parts are taken out of the heating furnace and placed in the air to cool to room temperature. Example

[0012] This embodiment takes the aged GH4169 alloy casing parts as an example, and the gradient heat treatment process for reducing the residual stress thereof includes the following steps: Step (1) Select a high-precision heat treatment heating furnace to ensure the actual temperature fluctuation range requirements of the parts, specifically, the temperature range of the heating furnace is below 800°C, the temperature tolerance is not greater than ±10°C, and the heating and furnace cooling rates are precisely controlled; Step (2) arranges a stress relief gradient heat treatment in the process of machining a large amount of metal and the excess is basically uniform, specifically: Step (2.1) Load the parts into the heating furnace at room temperature, heat them at a rate of 40°C / h to a first gradient temperature of 600°C, and keep them at this temperature for 2 hours; After the first gradient temperature stage of step (2.2) is completed, the parts are cooled in the furnace at a rate of 40°C / h to a second gradient temperature of 500°C and kept at this temperature for 1 hour; After the second temperature gradient stage in step (2.3) is completed, the parts are taken out of the heating furnace and placed in the air to cool to room temperature.

[0013] The surface residual stress of GH4169 alloy parts under different heat treatment processes was measured by X-ray diffraction. The results are as follows Figure 2As shown in the figure, after the gradient heat treatment of the present invention, the residual stress is greatly reduced, and the stress level reaches below -150MPa. Compared with the parts in the state of machine aging, the maximum reduction is more than 600MPa, and the average reduction is close to 380MPa; compared with the parts in the state of existing stress relief treatment, the stress is further reduced, with the maximum reduction reaching more than 200MPa and the average reduction reaching more than 100MPa.

[0014] The typical microstructure and mechanical properties test results before and after gradient heat treatment are shown in Table 1: Table 1 Typical microstructure and mechanical properties test results before and after gradient heat treatment

Claims

1. A gradient heat treatment process for reducing residual stress of GH4169 alloy parts in an aged state, characterized in that: The following steps are involved: Step (1) Select a high-precision heat treatment furnace to ensure that the actual temperature fluctuation range of the parts is within the requirements; Step (2) arranges a stress relief gradient heat treatment in the process of machining a large amount of metal and the excess is basically uniform, specifically: Step (2.1) Load the parts into the heating furnace at room temperature and heat them to a first gradient temperature of 600°C to 620°C at a rate of (50±10)°C / h, and keep them at that temperature for 2-4 hours; After the first gradient temperature stage of step (2.2) is completed, the parts are cooled in the furnace at a rate of (50±10)℃ / h to a second gradient temperature of 500℃~550℃ and kept at this temperature for 1-2 hours; After the second temperature gradient stage in step (2.3) is completed, the parts are taken out of the heating furnace and placed in the air to cool to room temperature.

2. A gradient heat treatment process for reducing residual stress of GH4169 alloy parts in an aged state according to claim 1, characterized in that: The temperature range of the heating furnace in step (1) is below 800°C, and the temperature tolerance is no more than ±10°C, so that precise control of the heating and furnace cooling rates can be achieved.

Images