A method for producing a fgh96 alloy standard sample for a residual stress deflection method calibration device

Abstract

The application provides a preparation method of a FGH96 alloy standard sample for a residual stress deflection method calibration device, and relates to the technical field of material analysis and testing. Traditional stress relief annealing of the FGH96 alloy adopts air cooling or furnace cooling, and the workpiece is cooled at a speed that is too fast in the range of 760 DEG C to 400 DEG C, so that more residual stress is introduced. The application can effectively and uniformly reduce the residual stress by controlling the cooling rate in the range of 760 DEG C to 400 DEG C to be 0.8-1.2 DEG C / min, and the mechanical properties such as the strength of the standard sample will not be deteriorated. The FGH96 alloy standard sample obtained by the method has small residual stress and uniform distribution, and can meet the use requirements of the residual stress calibration device.

Description

Technical Field

[0001] This invention relates to the field of materials analysis and testing technology, and in particular to a method for preparing FGH96 alloy standard samples for a residual stress deflection method calibration device. Background Technology

[0002] During processing and use, metallic materials often generate certain residual stresses within them. Except in a few cases, the presence of residual stresses often leads to significant hazards, such as causing deformation of parts and affecting the safety and stability of the overall structure. Therefore, the accurate measurement and control of residual stresses are of great importance.

[0003] Deflection-based stress calibration devices can effectively calibrate residual stress testing processes (e.g., CN201710418129.8 discloses a stress measurement device based on the deflection method). The FGH96 alloy low-stress, equal-strength beam standard used in the deflection-based stress calibration device needs to meet the requirement of initial residual stress ≤ 0.05σ. s The conditions are as follows. Although as little residual stress as possible is introduced during the preparation of raw materials, the initial residual stress of the processed equal-strength beam standard sample still does not meet the standard, which requires stress-relief annealing. The purpose of stress-relief annealing is to reduce the residual stress of the standard sample without reducing its strength. However, the traditional FGH96 alloy stress-relief annealing method (760℃ / 8h / air cooling or 760℃ / 8h / furnace cooling) can only make the residual stress in some parts of the standard sample meet the standard, while the residual stress in other parts does not meet the standard, resulting in an unsatisfactory and uneven stress relief effect. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing FGH96 alloy standard samples for a residual stress deflection method calibration device. The FGH96 alloy standard samples obtained by the method of this invention have low residual stress and uniform distribution, which can meet the requirements of the residual stress calibration device.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing FGH96 alloy standard samples for a residual stress deflection method calibration device, comprising the following steps:

[0007] Provide raw material bars; the composition of the raw material bars corresponds to the composition of the FGH96 alloy standard sample;

[0008] The raw material bars are machined to obtain beam blanks of equal strength.

[0009] The equal-strength beam blank is ground to obtain an equal-strength beam sample.

[0010] The equal strength beam specimen was subjected to stress-relief annealing and cooling to obtain FGH96 alloy standard specimens for the residual stress deflection method calibration device.

[0011] The stress-relief annealing temperature is 760℃, and the holding time is 8h; the cooling is a first cooling from 760℃ to 400℃, and then a second cooling from 400℃ to 20-25℃, wherein the first cooling rate is 0.8-1.2℃ / min.

[0012] Preferably, the first cooling rate is 1°C / min.

[0013] Preferably, the second cooling method is furnace cooling or temperature-controlled cooling, and the rate of temperature-controlled cooling is 0.8 to 1.2 °C / min.

[0014] Preferably, the grinding conditions include: a grinding depth of 0.2 mm, a feed rate of 0.02 mm, and a grinding wheel speed of 1500 r / min.

[0015] Preferably, the cooling method for the grinding process is a casting-type lubrication cooling.

[0016] Preferably, the machining process includes wire cutting.

[0017] Preferably, the preparation of the raw material bar includes: hot isostatic pressing of the raw material powder according to the composition of the FGH96 alloy standard sample to obtain the raw material bar.

[0018] This invention provides a method for preparing an FGH96 alloy standard sample for a residual stress deflection method calibration device, comprising the following steps: providing raw material bars; the composition of the raw material bars corresponding to the composition of the FGH96 alloy standard sample; machining the raw material bars to obtain an equal-strength beam blank; grinding the equal-strength beam blank to obtain an equal-strength beam sample; stress-relief annealing and cooling the equal-strength beam sample to obtain an FGH96 alloy standard sample for a residual stress deflection method calibration device; the stress-relief annealing temperature is 760℃, and the holding time is 8h; the cooling is a first cooling from 760℃ to 400℃, and then a second cooling from 400℃ to 20-25℃, wherein the first cooling rate is 0.8-1.2℃ / min. Traditional stress-relief annealing of FGH96 alloy uses air cooling or furnace cooling, which results in excessively rapid cooling of the workpiece in the 760℃~400℃ range, introducing a significant amount of residual stress. This invention, by controlling the cooling rate between 760℃ and 400℃ to 0.8~1.2℃ / min, can effectively and uniformly reduce residual stress without deteriorating the strength and other mechanical properties of the standard sample.

[0019] Furthermore, in existing technologies, the production of finished metal parts involves rough machining (or semi-finishing), followed by heat treatment, and finally finish machining (grinding is a type of finish machining) to ensure machining accuracy. Although grinding does not introduce much residual stress, the standard samples have very high requirements for residual stress. Therefore, the traditional machining sequence of stress-relief annealing followed by grinding still leads to excessive residual stress. This invention, by adjusting the machining sequence and adopting a process of grinding followed by heat treatment, and by controlling the grinding and stress-relief annealing parameters, can simultaneously ensure that the residual stress meets the standard and that the flatness of the standard samples remains essentially unchanged before and after stress-relief annealing, while still meeting the standard (≤0.02mm). Attached Figure Description

[0020] Figure 1 The actual temperature changes of the standard samples during the stress-relief annealing process in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0021] This invention provides a method for preparing FGH96 alloy standard samples for a residual stress deflection method calibration device, comprising the following steps:

[0022] Provide raw material bars; the composition of the raw material bars corresponds to the composition of the FGH96 alloy standard sample;

[0023] The raw material bars are machined to obtain beam blanks of equal strength.

[0024] The equal-strength beam blank is ground to obtain an equal-strength beam sample.

[0025] The equal strength beam specimen was subjected to stress-relief annealing and cooling to obtain FGH96 alloy standard specimens for the residual stress deflection method calibration device.

[0026] The stress-relief annealing temperature is 760℃, and the holding time is 8h; the cooling is a first cooling from 760℃ to 400℃, and then a second cooling from 400℃ to 20~25℃ (room temperature), wherein the first cooling rate is 0.8~1.2℃ / min.

[0027] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0028] The present invention first provides raw material rods.

[0029] This invention does not have special requirements regarding the source of the raw material bars; they can be purchased commercially or prepared in-house. When preparing in-house, the preparation of the raw material bars preferably includes: hot isostatic pressing the raw material powder according to the composition of the FGH96 alloy standard sample to obtain the raw material bars.

[0030] The present invention does not have special requirements for the implementation process of hot isostatic pressing; a hot isostatic pressing process well known in the art can be used. Specifically, the raw material powder is loaded into a sleeve, and then nitrogen or argon is used as the pressurizing medium to directly heat and pressurize the powder to form the desired shape. In the present invention, the density of the raw material rods obtained by hot isostatic pressing reaches 100%.

[0031] After obtaining the raw material bars, the present invention performs machining on the raw material bars to obtain beam blanks of equal strength. In the present invention, the machining preferably includes wire cutting. The present invention processes the raw material bars into a specified shape through machining.

[0032] After obtaining the equal strength beam blank, the present invention grinds the equal strength beam blank to obtain the equal strength beam sample.

[0033] In this invention, the preferred grinding conditions include: a grinding depth of 0.2 mm, a feed rate of 0.02 mm, and a grinding wheel speed of 1500 r / min. Grinding is used in this invention to ensure a smooth surface on the standard sample while minimizing the introduction of residual stress. The preferred cooling method for the grinding process in this invention is casting-type lubrication cooling.

[0034] After obtaining the equal-strength beam specimen, the present invention performs stress-relief annealing and cooling on the equal-strength beam specimen to obtain the FGH96 alloy standard specimen for the residual stress deflection method calibration device.

[0035] In this invention, the stress-relief annealing temperature is 760°C, and the holding time is 8 hours. The stress-relief annealing is preferably performed in a conventional electric furnace.

[0036] In this invention, the cooling is a first cooling from 760°C to 400°C, and then a second cooling from 400°C to 20-25°C. The first cooling rate is 0.8-1.2°C / min, preferably 0.9-1.1°C / min, and more preferably 1°C / min. The second cooling method is preferably furnace cooling or temperature-controlled cooling. The temperature-controlled cooling rate is preferably 0.8-1.2°C / min, and more preferably the same as the first cooling rate.

[0037] Traditional stress-relief annealing of FGH96 alloy uses air cooling or furnace cooling, which results in excessively rapid cooling of the workpiece in the 760℃~400℃ range, introducing a significant amount of residual stress. This invention, by controlling the cooling rate between 760℃ and 400℃ to 0.8~1.2℃ / min, can effectively and uniformly reduce residual stress without deteriorating the strength and other mechanical properties of the standard sample.

[0038] Furthermore, in existing technologies, the production of finished metal parts involves rough machining (or semi-finishing), followed by heat treatment, and finally finish machining (grinding is a type of finish machining) to ensure machining accuracy. Although grinding does not introduce much residual stress, the standard samples have very high requirements for residual stress. Therefore, the traditional machining sequence of stress-relief annealing followed by grinding still leads to excessive residual stress. This invention, by adjusting the machining sequence and adopting a process of grinding followed by heat treatment, and by controlling the grinding and stress-relief annealing parameters, can simultaneously ensure that the residual stress meets the standard and that the flatness of the standard samples remains essentially unchanged before and after stress-relief annealing, while still meeting the standard (≤0.02mm).

[0039] The following detailed description, in conjunction with embodiments, illustrates the preparation method of the FGH96 alloy standard sample for the residual stress deflection method calibration device provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] Corresponding to the composition of the FGH96 alloy standard sample, the raw material powder was hot isostatically pressed to obtain raw material bars; the bars had a diameter of 280 mm and a height of 170 mm.

[0042] The raw material bars are wire-cut to obtain equal-strength beam blanks;

[0043] The equal-strength beam blank was ground to a depth of 0.2 mm, a feed rate of 0.02 mm, and a grinding wheel speed of 1500 r / min. After lubrication and cooling, an equal-strength beam sample was obtained; the flatness was 0.0167 mm.

[0044] The equal-strength beam specimen was subjected to stress-relief annealing at a temperature of 760℃ for 8 hours, followed by cooling at a rate of 1℃ / min from 760℃ to 400℃, with furnace cooling after 400℃. The specimen was cooled to room temperature to obtain an FGH96 alloy standard specimen for the residual stress deflection method calibration device, with a flatness of 0.0106 mm.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that the stress-relief annealing is cooled in the furnace, that is, cooled from 760°C to room temperature.

[0047] The actual temperature changes of the standard samples during stress-relief annealing in Example 1 (controlled cooling) and Comparative Example 1 (furnace cooling) are as follows: Figure 1 As shown, by Figure 1 It can be seen that Comparative Example 1 uses traditional furnace cooling, and the cooling rate of 760℃~400℃ is too fast, which introduces more residual stress.

[0048] Performance testing:

[0049] The residual stress of the standard samples prepared in Example 1 and Comparative Example 1 was tested using the blind hole method, and the results are shown in Tables 1 and 2. The residual stress of the standard samples prepared in Example 1 and Comparative Example 1 was tested using the X-ray method, and the results are shown in Tables 3 and 4.

[0050] Table 1. Results of residual stress test of specimen in Comparative Example 1 using the blind hole method.

[0051]

[0052] Table 2. Results of residual stress test on specimen using the blind hole method in Example 1.

[0053]

[0054] Table 3 Results of X-ray residual stress test on specimen 1 (Comparative Example 1)

[0055]

[0056] Table 4 Results of X-ray Residual Stress Test of Specimen in Example 1

[0057]

[0058] Table 5. Room temperature tensile mechanical properties of FGH96 alloy under different process parameters

[0059]

[0060] Note: In Table 5, H3-1 and H3-2 are two samples prepared using the scheme of Comparative Example 1, and H5-1 and H5-2 are two samples prepared using the scheme of Example 1.

[0061] Compared to the traditional stress-relief annealing process (Comparative Example 1), the optimized stress-relief annealing process for the FGH96 standard sample resulted in an approximately 10 MPa increase in yield strength (Table 5). The residual stress level, tested using the blind hole method, decreased by an average of 30 MPa with a lower standard deviation (Tables 1 and 2). Furthermore, the residual stress level, tested using the X-ray method, decreased by an average of 5 MPa with a lower standard deviation (Tables 3 and 4). This demonstrates that the optimized FGH96 stress-relief annealing process significantly reduces residual stress in the workpiece and promotes more uniform stress distribution.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing FGH96 alloy standard samples for a residual stress deflection method calibration device, characterized in that, Includes the following steps: Provide raw material bars; the composition of the raw material bars corresponds to the composition of the FGH96 alloy standard sample; The raw material bars are machined to obtain beam blanks of equal strength. The equal-strength beam blank is ground to obtain an equal-strength beam sample; the grinding conditions include: grinding depth of 0.2 mm, feed rate of 0.02 mm, and grinding wheel speed of 1500 r / min. The equal strength beam specimen was subjected to stress-relief annealing and cooling to obtain FGH96 alloy standard specimens for the residual stress deflection method calibration device. The stress-relief annealing temperature is 760℃, and the holding time is 8h; the cooling is a first cooling from 760℃ to 400℃, and then a second cooling from 400℃ to 20~25℃, wherein the first cooling rate is 0.8~1.2℃ / min; the second cooling method is furnace cooling.

2. The preparation method according to claim 1, characterized in that, The first cooling rate is 1°C / min.

3. The preparation method according to claim 1, characterized in that, The cooling method for the grinding process is casting-type lubrication cooling.

4. The preparation method according to claim 1, characterized in that, The machining process includes wire cutting.

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