Method for manufacturing stress reference chip

Abstract

To provide a method capable of manufacturing a stress reference piece made from an aluminum alloy.SOLUTION: A method of manufacturing a stress reference piece includes the following steps: (S1) preparing an aluminum alloy member containing an element that generates a β phase; (S2) performing a shot peening treatment on the aluminum alloy member; and (S3) performing a tempering treatment on the aluminum alloy member after the shot peening treatment, the tempering treatment to accelerate the generation of the β phase.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a stress reference piece.

Background Art

[0002] In X-ray residual stress measurement, for the operation confirmation of the measuring instrument, it is recommended to measure a reference piece using non-distorted iron powder (Non-Patent Document 1). Non-distorted iron powder is an object obtained by solidifying iron powder close to fully annealed pure iron with an adhesive or the like. By using such a reference piece and confirming whether a value near 0 MPa (no stress) is measured, it is possible to confirm that the measuring instrument is operating normally.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an X-ray residual stress measuring instrument is used in the industrial field, there is a potential requirement to configure a reference piece with a material used for manufacturing.

[0005] The present disclosure provides a method for manufacturing a stress reference piece capable of manufacturing a stress reference piece made of an aluminum alloy.

Means for Solving the Problems

[0006] A method for manufacturing a stress reference piece according to one aspect of the present disclosure includes a step of preparing an aluminum alloy member containing an element that generates a β phase, a step of performing shot peening on the aluminum alloy member, and a step of performing a tempering treatment that promotes the generation of the β phase on the aluminum alloy member after the shot peening.

[0007] In this method for manufacturing the stress reference piece, the crystal grains on the surface layer of the aluminum alloy member can be refined by shot peening treatment. Therefore, a certain number or more of crystal grains can be present within the measurement range of X-ray residual stress measurement, and the detected Debye rings can be made into continuous rings. The reliability of X-ray residual stress measurement is preferably such that the peak intensity is constant, that is, the Debye rings are continuous. Thus, in X-ray residual stress measurement, reliable measurement results can be obtained. As a result of introducing strain by shot peening treatment on the surface layer of the aluminum alloy member, residual stress (residual compressive stress) is imparted. The residual stress generated by shot peening treatment is relaxed when the β-phase is formed on the strain. Since the aluminum alloy member contains an element that generates the β-phase, the residual stress value changes over time (time-dependent change). In this manufacturing method, since the generation of the β-phase is promoted while maintaining the refinement of the crystal grains by tempering treatment, the change over time of the residual stress after tempering treatment can be suppressed. As described above, reliable measurement results can be obtained, and a stress reference piece made of an aluminum alloy in which the change over time of the residual stress value is suppressed can be manufactured.

[0008] In one embodiment of the present disclosure, the tempering treatment may be a treatment in which the aluminum alloy member is held at a temperature of 125 degrees or more and 170 degrees or less for 6 hours or more. In this case, while suppressing the recrystallization of the aluminum alloy, the aluminum alloy member can be reliably stress-relieved, and the change over time of the residual stress after tempering treatment can be suppressed. In this specification, stress-relieving means bringing the residual stress as close as possible to 0 MPa.

[0009] In one embodiment of the present disclosure, the time for which the aluminum alloy member is held at a temperature of 125 degrees or more and 170 degrees or less by tempering treatment may be 72 hours or less. In this case, the recrystallization of the aluminum alloy can be more reliably suppressed.

[0010] In one embodiment of the present disclosure, the element may be Mg, Cu, or Mn. Since all of these elements form a β-phase, it is effective to perform a tempering treatment.

[0011] In one embodiment of the present disclosure, the shot peening treatment may be performed using a shot medium made of zirconia, glass, or steel at an injection pressure of 0.1 MPa or more and 0.5 MPa or less. In this case, the crystal grains on the surface layer of the aluminum alloy member can be surely refined, and reliable measurement results can be obtained.

[0012] In one embodiment of the present disclosure, the tempering treatment may be performed such that the half-value width of the diffraction X-ray peak of the aluminum alloy member changes by 0.1 deg or more. In this case, the change over time of the residual stress can be surely suppressed.

[0013] In one embodiment of the present disclosure, the tempering treatment may be performed such that the change amount of the residual stress of the aluminum alloy member is 50 MPa or less within 24 hours after the tempering treatment and thereafter. In this case, the change over time of the residual stress can be surely suppressed.

[0014] In one embodiment of the present disclosure, the aluminum alloy member may be a bulk body. In this case, a stress reference piece of the bulk body can be obtained.

[0015] A method for manufacturing a stress reference piece according to another aspect of the present disclosure includes a step of preparing an aluminum alloy member containing an element that generates a β-phase, a step of performing a shot peening treatment on the aluminum alloy member, and a step of holding the aluminum alloy member after the shot peening treatment at 125 degrees or more and 170 degrees or less for 6 hours or more.

[0016] In this method for manufacturing a stress reference piece, the crystal grains on the surface layer of the aluminum alloy member can be refined by shot peening treatment. Therefore, a certain number or more of crystal grains can be present within the measurement range of X-ray residual stress measurement, and the detected Debye rings can be made into continuous rings. The reliability of X-ray residual stress measurement is desirably such that the peak intensity is constant, that is, the Debye rings are continuous. Thus, in X-ray residual stress measurement, reliable measurement results can be obtained. As a result of introducing strain by shot peening treatment on the surface layer of the aluminum alloy member, residual stress (compressive residual stress) is imparted. The residual stress generated by shot peening treatment is relaxed when the β-phase is formed on the strain. Since the aluminum alloy member contains an element that generates the β-phase, the residual stress value changes over time (time-dependent change). In this manufacturing method, since the aluminum alloy member is held at 125 degrees or more and 170 degrees or less for 6 hours or more, the generation of the β-phase can be promoted while suppressing the recrystallization of the aluminum alloy. By promoting the generation of the β-phase, the change over time of the residual stress after the heat treatment can be suppressed. As described above, reliable measurement results can be obtained, and a stress reference piece made of an aluminum alloy in which the change over time of the residual stress value is suppressed can be manufactured.

Effects of the Invention

[0017] According to the method for manufacturing a stress reference piece according to the present disclosure, a stress reference piece made of an aluminum alloy can be manufactured.

Brief Description of the Drawings

[0018]

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[0019] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant descriptions are omitted.

[0020] The stress reference piece manufactured by the manufacturing method according to the present embodiment is a bulk body made of an aluminum alloy containing an element that generates a β phase. The element that generates the β phase is, for example, Mg, Cu, or Mn. The stress reference piece contains at least one or more elements that generate the β phase. In the aging process in the isothermal state, a supersaturated solid solution, a needle-like zone, and rod-like precipitates are passed through in this order, and plate-like stable phase precipitates (β phase) are precipitated. The total volume of the precipitated β phase decreases from the total volume of the supersaturated solid solution. Let the energy generated by the decrease in the total volume be E, and let the energy G for the precipitation of the β phase, that is, the generation of a new phase, then G>E. Originally, by adding thermal energy H, G = E + H. By using the strain energy ΔG existing inside the material as an alternative to H, the β phase is precipitated even at room temperature.

[0021] If the content (total content) of Mg, Cu, and Mn elements is at least 0.2% or more, the β phase is generated. The stress reference piece is an aluminum alloy member with an extremely low stress (stress-free) in which the residual stress is infinitely close to 0. The residual stress value of the stress reference piece is, for example, -25 MPa or more and 25 MPa or less, and preferably -10 MPa or more and 10 MPa or less. Minus indicates residual compressive stress, and plus indicates residual tensile stress.

[0022] The stress reference piece is used to confirm the state of the stress measuring device. The stress reference piece is given a predetermined compressive residual stress in advance by combining shot peening treatment and heat treatment included in the conventional manufacturing processes in the automotive and aircraft industries. The following three points are required for the stress reference piece. (1) The detected device loop is continuous. That is, the crystal grains are sufficiently fine. (2) A predetermined residual stress value set in advance is measured. (3) No change over time in the residual stress value occurs.

[0023] The above (1) is solved by refining the crystal by shot peening treatment. However, by performing shot peening treatment with energy sufficient to enable refinement, residual compressive stress is applied to the surface layer. Also, as the residual stress is relaxed, a change over time in the residual stress value occurs. This change over time is related to the above elements added to the aluminum alloy. The above elements generate a β-phase compound on the strain introduced by shot peening treatment. At that time, the residual stress applied by shot peening treatment is relaxed.

[0024] Specifically, the residual stress value in the above (2) is near 0 MPa (no stress). In reality, 0 MPa is not calculated in the calculation when obtaining the measured value, so a certain degree of numerical variation is allowed. The above (3) is solved by performing heat treatment. However, the refined crystal grains recrystallize and coarsen due to heat treatment. For this reason, in the analysis of residual stress, the number of crystals from which data can be obtained decreases, and the device loop becomes discontinuous.

[0025] FIG. 1 is a flowchart showing a method for manufacturing a stress reference piece according to the present embodiment. As shown in FIG. 1, the method for manufacturing a stress reference piece includes steps S1 to S3. Hereinafter, each step will be described.

[0026] Step S1 is a step of preparing an aluminum alloy member containing an element that generates a β phase. The aluminum alloy member is a starting material for manufacturing a stress reference piece. The aluminum alloy member is a bulk body that has been subjected to a predetermined heat treatment. The aluminum alloy member is made of, for example, an aluminum alloy for rolling or an aluminum alloy for casting.

[0027] Step S2 is a step of performing shot peening treatment on the surface layer of the aluminum alloy member prepared in Step S1 using a shot peening device. According to Step S2, the crystal grains on the surface layer of the aluminum alloy member can be refined. Therefore, a certain number or more of crystal grains can be present in the measurement range of X-ray residual stress measurement, and the detected Debye rings can be made into continuous rings. As a result, reliable measurement results can be obtained in X-ray residual stress measurement.

[0028] The shot peening treatment is performed, for example, by an air method using a shot medium made of zirconia, glass, or steel. For this reason, the crystal grains on the surface layer of the aluminum alloy member can be surely refined. The air pressure (injection pressure) is, for example, 0.1 MPa or more and 0.5 MPa or less. The particle size of the shot medium is, for example, 0.05 mm or more and 0.6 mm or less. The hardness of the shot medium is, for example, 250 HV or more and 700 HV or less. These shot peening conditions are set according to the type of the aluminum alloy member.

[0029] The shot peening treatment refines (nanocrystallizes) the crystal grains on the surface layer of the aluminum alloy member. As a result, the number of crystals from which data can be acquired increases in the analysis of residual stress. Therefore, the Debye rings can be made into continuous rings, and the reliability of the measurement results can be improved. The particle size of the refined crystal grains is, for example, 5 nm or more and 50 nm or less, and 5 nm or more and 20 nm or less is more preferable. The refined crystal grains are present, for example, in a depth range within 50 μm from the surface of the aluminum alloy member.

[0030] Step S3 is a step of performing tempering treatment on the aluminum alloy member after shot peening treatment. The tempering treatment is a treatment in which the aluminum alloy member is held at a temperature of 125 degrees or more and 170 degrees or less for 1 hour or more, and then cooled until it reaches room temperature. The generation of the β-phase compound is promoted by heating in a temperature range of 125 degrees or more. Therefore, according to Step S3, the change over time of the residual stress after tempering treatment can be suppressed. The recrystallization temperature of an aluminum alloy with low purity is 180 degrees or more. Therefore, recrystallization can be suppressed by heating in a temperature range of 170 degrees or less.

[0031] The time (heat treatment time) for holding the aluminum alloy member at a temperature of 125 degrees or more and 170 degrees or less by tempering treatment is at least 1 hour or more, preferably 6 hours or more. Thereby, while suppressing the recrystallization of the aluminum alloy, the aluminum alloy member can be surely stress-free, and the change over time of the residual stress after tempering treatment can be suppressed. The heat treatment time is 72 hours or less, preferably 48 hours or less, more preferably 24 hours or less. By setting the heat treatment time to 72 hours or less, the recrystallization of the aluminum alloy can be more surely suppressed and the productivity can be improved.

[0032] Step S3 is performed using a device capable of maintaining a constant temperature at a temperature higher than room temperature, such as a drying furnace or a muffle furnace. Thereby, in X-ray residual stress measurement, a more reliable measurement result can be obtained. The tempering treatment is performed so that the half-value width of the diffraction X-ray peak of the aluminum alloy member changes by 0.1 deg or more, preferably 0.2 or more before and after the tempering treatment. The tempering treatment is performed so that the change amount (absolute value) of the residual stress of the aluminum alloy member becomes 50 MPa or less within 24 hours after the tempering treatment and thereafter. Thereby, the change over time of the residual stress can be suppressed. Step S3 is performed, for example, immediately after Step S2. In this case, the productivity is improved. Step S3 may be performed after a lapse of time after Step S2.

[0033] Through the above steps S1 to S3, a reliable measurement result can be obtained, and a stress reference piece made of an aluminum alloy with the change in residual stress value over time suppressed can be manufactured.

[0034] The present invention is not necessarily limited to the above-described embodiments, and various modifications are possible without departing from the gist thereof.

Example

[0035] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0036] The stress reference piece according to the example was manufactured as follows. First, as starting materials, test materials made of aluminum alloy JIS A7075 for rolling and JIS A2014 were prepared respectively. Next, shot peening treatment was performed on these test materials. As the shot medium, zircon beads B-205 (particle size 0.05 mm) manufactured by Sango Ban Co., Ltd. was used. The injection pressure was 0.3 MPa, the stage moving speed was 10 mm / s, and the arc height was 0.090 mmN. Subsequently, as the tempering treatment, the test material after the shot peening treatment was held at 150 degrees for 6 hours and then cooled to room temperature. Thereby, the stress reference piece according to the example was obtained.

[0037] FIG. 2 is a graph showing the change over time of the residual stress of the stress reference piece according to the example. FIG. 3 is a graph showing the change over time of the half-value width of the stress reference piece according to the example. The horizontal axis in FIGS. 2 and 3 indicates the aging time. The vertical axis in FIG. 2 indicates the residual stress. The vertical axis in FIG. 3 indicates the half-value width. The measurement of the residual stress and the half-value width was performed by the cosα method using an X-ray residual stress measuring device μ-X360s manufactured by Pulstec Industrial Co., Ltd. Using a Cr tube target, the irradiation diameter was φ3.0 mm, the collimator diameter was φ1.0 mm, and the measurement angle was 25 degrees.

[0038] The measurement of the residual stress and the half-value width was carried out at the time points of aging time of 0.25 days, 1 day, 5 days, 10 days, 20 days, and 30 days, with the start point of the aging time being the start point of the tempering treatment. The data at the aging time of 0.25 days (i.e., 6 hours) are the measured values immediately after the tempering treatment. The residual stress and the half-value width at the aging time of 0 are the measured values after the shot peening treatment and immediately before the tempering treatment.

[0039] As shown in Figure 2, the residual stress of JIS A7075 was -147 MPa immediately after the shot peening treatment, but was stress-relieved by the tempering treatment and showed -16 MPa immediately after the tempering treatment. After that, the change amount was small and showed -5 MPa at the aging time of 30 days. The change amount (absolute value) was 20 MPa or less within 24 hours after the tempering treatment and thereafter. The residual stress of JIS A2014 was -89 MPa immediately after the shot peening treatment, but was stress-relieved by the tempering treatment and showed -11 MPa immediately after the tempering treatment. After that, the change amount was small and showed -1 MPa at the aging time of 30 days. The change amount (absolute value) was 20 MPa or less within 24 hours after the tempering treatment and thereafter.

[0040] As shown in Figure 3, the half-value width of JIS A7075 was 2.12 deg immediately after the shot peening treatment, but decreased by 0.37 deg due to the tempering treatment and showed 1.75 deg immediately after the tempering treatment. After that, there was almost no change and it showed 1.76 deg at the aging time of 30 days. The half-value width of JIS A2014 was 1.96 deg immediately after the shot peening treatment, but decreased by 0.26 deg due to the tempering treatment and showed 1.70 deg immediately after the tempering treatment. After that, there was almost no change and it showed 1.68 deg at the aging time of 30 days.

[0041] The residual stress and half-value width of JIS A7075 did not change from 30 days to 100 days after the aging time. Also, as described in FIG. 5, even when the holding time of the quenching and tempering treatment was 24 hours, 48 hours, and 72 hours, the results were comparable to those in the case of 6 hours. Similarly, the residual stress and half-value width of JIS A2014 did not change from 30 days to 100 days after the aging time. Also, as described in FIG. 6, even when the holding time of the quenching and tempering treatment was 24 hours, 48 hours, and 72 hours, the results were comparable to those in the case of 6 hours.

[0042] FIG. 4 is a graph showing the change over time of the residual stress of the stress reference piece according to the comparative example. For the stress reference piece according to the comparative example, it was manufactured in the same manner as in the examples except that the quenching and tempering treatment was not performed, and the residual stress was measured in the same manner as in the examples. As shown in FIG. 4, the residual stress of JIS A7075 was -146 MPa immediately after the shot peening treatment, but then continued to change and showed -80 MPa at an aging time of 30 days. The residual stress of JIS A2014 was -88 MPa immediately after the shot peening treatment, but then continued to change and showed -44 MPa at an aging time of 30 days.

[0043] FIGS. 5 and 6 are graphs showing the relationship between the holding time and the residual stress. The horizontal axis of FIGS. 5 and 6 indicates the holding time. The vertical axis of FIGS. 5 and 6 indicates the residual stress. Here, the holding time of the quenching and tempering treatment after the shot peening treatment was set to 0, 30 minutes, 1 hour, 6 hours, 24 hours, 48 hours, and 72 hours, and the residual stress was measured immediately after the quenching and tempering treatment. The case where the holding time is 6 hours corresponds to the case of the above-described examples. The case where the holding time is 0 corresponds to the case of the above-described comparative example where the quenching and tempering treatment was not performed, and the value of the residual stress measured immediately after the shot peening treatment was used.

[0044] Figure 5 shows the case where the test piece is made of JIS A7075. As shown in Figure 5, the residual stress is -80 MPa at a holding time of 30 minutes and -70 MPa at a holding time of 1 hour, and is a larger value on the compression side compared to the case where the holding time is 6 hours or more. When the holding time was 6 hours or more, there was no significant difference in the residual stress. Figure 6 shows the case where the test piece is made of JIS A2014. As shown in Figure 6, the residual stress is -38 MPa at a holding time of 30 minutes and -21 MPa at a holding time of 1 hour, and is a larger value on the compression side compared to the case where the holding time is 6 hours or more. When the holding time was 6 hours or more, there was no significant difference in the residual stress.

[0045] Figures 7 and 8 are graphs showing the relationship between the peak intensity and the α angle. The α angle is the rotation angle of the Debye ring and is shown from 0 degrees to 360 degrees. Here, shot peening treatment was performed under the same conditions as in the above examples, and X-ray diffraction images were obtained before and after the shot peening treatment. Furthermore, X-ray diffraction images were similarly obtained for the case of tempering treatment with holding times of 6 hours, 24 hours, 48 hours, and 72 hours. For the Debye ring near the diffraction angle (2θ) of about 139 deg in each of the obtained X-ray diffraction images, the peak intensity was plotted against the α angle.

[0046] Figure 7 shows the case where the test piece is made of JIS A7075. Figure 8 shows the case where the test piece is made of JIS A2014. As shown in Figures 7 and 8, in both cases of using any test piece, before the shot peening treatment, prominent peaks are observed at two points (two α angles) on the Debye ring. When the shot peening treatment is applied, the phenomenon is suppressed and the peak intensity becomes constant, that is, the Debye ring approaches continuously. Thus, it was confirmed that the reliability of X-ray stress measurement is improved by the shot peening treatment.

[0047] Even when the quenching and tempering treatment was performed, the device rings were continuous. No significant difference was observed in the peak intensity of the device rings after the quenching and tempering treatment depending on the holding time. In particular, when the test piece made of JIS A7075 was used, the peak intensity of the device rings after the quenching and tempering treatment was substantially the same regardless of the holding time. Therefore, considering the productivity aspect, a holding time of 6 hours is considered to be optimal.

Claims

1. A step of preparing an aluminum alloy member containing an element that generates a β phase; A step of performing shot peening on the aluminum alloy member; A step of performing a tempering treatment that promotes the generation of the β phase on the aluminum alloy member after the shot peening treatment, and includes: A method for manufacturing a stress reference piece.

2. The tempering treatment is a treatment in which the aluminum alloy member is held at a temperature of 125 degrees or more and 170 degrees or less for 6 hours or more, The method for manufacturing a stress reference piece according to Claim 1.

3. The time for holding the aluminum alloy member at a temperature of 125 degrees or more and 170 degrees or less by the tempering treatment is 72 hours or less, The method for manufacturing a stress reference piece according to Claim 2.

4. The element is Mg, Cu, or Mn, The method for manufacturing a stress reference piece according to any one of Claims 1 to 3.

5. The shot peening treatment is performed using a shot medium made of zirconia, glass, or steel at an injection pressure of 0.1 MPa or more and 0.5 MPa or less, The method for manufacturing a stress reference piece according to any one of Claims 1 to 4.

6. The tempering treatment is performed such that the half-value width of the diffraction X-ray peak of the aluminum alloy member changes by 0.1 deg or more, The method for manufacturing a stress reference piece according to any one of Claims 1 to 5.

7. The tempering treatment is performed such that the change amount of the residual stress of the aluminum alloy member becomes 50 MPa or less within 24 hours after the tempering treatment and thereafter, The method for manufacturing a stress reference piece according to any one of Claims 1 to 6.

8. The aluminum alloy member is a bulk body, The method for manufacturing a stress reference piece according to any one of Claims 1 to 7.

9. A step of preparing an aluminum alloy member containing an element that generates a β phase; A step of performing shot peening on the aluminum alloy member; A step of holding the aluminum alloy member after the shot peening treatment at 125 degrees or more and 170 degrees or less for 6 hours or more, and includes: A method for manufacturing a stress reference piece.

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