JP2019203197A - Method for heat-treating lamination-molded object and method for manufacturing copper alloy molded object - Google Patents

Abstract

To provide a method for heat-treating a lamination-molded object allowing for manufacturing a copper alloy molded object having a higher mechanical strength and/or electrical/thermal conductivity.SOLUTION: A method for heat-treating a lamination-molded object additionally manufactured uses a copper alloy powder consisting of Cr:1.1-20 mass%, Zr:0-0.2 mass%, and a remainder of Cu and inevitable impurities. The method for heat-treating a lamination-molded object has a first heat treatment step that holds the lamination-molded object at a first heat treatment temperature of 500-800°C and a second heat treatment step that holds it at a second heat treatment temperature that is a temperature of 400°C or higher and 50°C or more lower than the first heat treatment temperature after the first heat treatment step.SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a metal additive manufacturing technique using a powder bed fusion bonding method, and more specifically, a copper alloy powder as a raw material, a heat treatment method for a layered object manufactured by additive manufacturing, and a copper alloy shaped object including the heat treatment step. The present invention relates to a manufacturing method and a copper alloy shaped article.

  As a method for manufacturing a metal three-dimensional model, an additional manufacturing technique, a so-called 3D printing technique, has attracted attention. Of these, the additive manufacturing method using the powder bed fusion bonding method repeatedly lays the metal powder as a raw material on the modeling stage, and irradiates the predetermined position with a laser beam or an electron beam to melt and solidify the metal powder for lamination. This is a method of modeling a three-dimensional shape. Typical methods include laser sintering (SLS, Selective Laser Sintering) and laser melting (SLM, Selective Laser Melting). By this method, a product having a complicated shape that could not be made by conventional cutting or the like can be manufactured in a relatively short time.

  One problem in the additive manufacturing of metals is that it is difficult to manufacture products that take advantage of the excellent electrical and thermal conductivity of copper. The main causes are that the energy absorption rate of copper with respect to the wavelength of the laser beam (for example, 1090 nm for Yb fiber laser) is extremely low and the melting point cannot be reached. It is that the diffusion does not proceed sufficiently.

  On the other hand, Patent Document 1 contains at least one of chromium and silicon of 0.10% by mass or more and 1.00% by mass or less, and the total amount of chromium and silicon is 1.00% by mass or less. Yes, a copper alloy powder for additive manufacturing (additional manufacturing) is described in which the balance is made of copper. By using this copper alloy powder, it is possible to manufacture a layered object that can achieve both mechanical strength and electrical conductivity (electrical conductivity). Further, Patent Document 1 describes that the mechanical properties and conductivity are improved by performing heat treatment on the layered object.

Japanese Patent No. 6030186

  According to the example of Patent Document 1, an additive material with a tensile strength of 186.74 to 281.41 MPa and conductivity of 23.59 to 60.42% IACS can be obtained by blending chromium or silicon. ing. Further, the conductivity is improved to 26.25 to 64.27% IACS by heat treatment at 300 ° C. for 3 hours under a nitrogen atmosphere.

  However, the shaped article described in Patent Document 1 has room for further improvement in both mechanical strength and electrical conductivity. Further, although the electrical conductivity was slightly improved by the heat treatment at 300 ° C. for 3 hours, the effect of the heat treatment was not sufficient. In addition, samples with high electrical conductivity (Table 5) have low tensile strength, and samples with high tensile strength (Tables 6 and 7) have low electrical conductivity of 23.59 to 38.12%. It was desired to achieve a higher level of sex.

  The present invention has been made in view of the above, and an object of the present invention is to provide a copper alloy shaped article having higher mechanical strength and / or electrical conductivity / thermal conductivity than conventional ones by additive manufacturing. Moreover, an object of this invention is to provide the copper alloy powder which can manufacture this copper alloy molded object, the heat processing method of a laminated molded object, and the manufacturing method of a copper alloy molded object.

  As a result of intensive studies, the present inventors have obtained the following knowledge. It is said that the amount of saturated solid solution of chromium (Cr) with respect to copper (Cu) is small, less than 0.7% by mass at the eutectic temperature of about 1070 ° C, suddenly decreases due to temperature drop and less than 0.1% at 500 ° C and room temperature. ing. Then, when addition manufacture is performed using this Cu alloy containing 0.1 mass% or more of Cr, modeling becomes easy because the thermal conductivity is lower than that of pure copper (pure Cu). Due to the rapid cooling at the time of additive manufacturing, the material containing the superposed structure contains supersaturated Cr in the Cu phase. When this layered object is appropriately heat-treated, a Cr phase is precipitated in the parent phase of Cu and the electrical conductivity and thermal conductivity are improved by decreasing the Cr concentration of the parent phase. At the same time, the mechanical strength of the shaped article is also improved by the precipitation hardening action by Cr phase precipitation. When the Cr concentration in the initial Cu alloy is high to some extent, the Cr phase precipitates at the stage of the material as it is laminated, but even in this case, the electrical conductivity and heat conduction are reduced by the decrease in the Cr concentration of the parent phase due to heat treatment. Improves.

  Based on this knowledge, in the present invention, Cu-Cr alloy powder suitable for addition manufacturing and heat treatment of the obtained layered object, heat treatment method of layered object, method of manufacturing copper alloy shaped object that combines addition manufacturing and heat treatment It became possible to provide a copper alloy shaped article having high mechanical strength, electrical conductivity, and thermal conductivity.

  Specifically, the copper alloy powder of the present invention is a copper alloy powder for additive manufacturing, Cr: 1.1-20% by mass, Zr: 0-0.2% by mass, the balance being Cu and inevitable Consists of impurities.

  The layered object heat treatment method of the present invention is a heat treatment method for a layered object that is additionally manufactured using the copper alloy powder, and includes a heat treatment step of holding the layered object at 300 to 800 ° C. Preferably, the heat treatment step includes a first heat treatment step for holding the layered object at a first heat treatment temperature of 500 to 800 ° C. and a temperature of 400 ° C. or more and the first heat treatment temperature after the first heat treatment step. A second heat treatment step of holding at a second heat treatment temperature.

  Another layered object heat treatment method of the present invention is a heat treatment method of a layered object made of a copper alloy, and the copper alloy contains Cr: 0.1 to 20% by mass, Zr: 0 to 0.2% by mass. The content of Cr is larger than the content of Zr, the balance is made of Cu and inevitable impurities, and the heat treatment step of holding the layered object at 410 to 800 ° C. is included. Preferably, the heat treatment step includes a first heat treatment step of holding the layered object at a first heat treatment temperature of 500 to 800 ° C. and a temperature of 410 ° C. or more and the first heat treatment temperature or less after the first heat treatment step. A second heat treatment step of holding at a second heat treatment temperature.

  The method for producing a copper alloy shaped article of the present invention includes a first step of forming a thin layer of the copper alloy powder of the present invention, and melting and solidifying the copper alloy powder by irradiating an electromagnetic wave beam at a predetermined position of the thin layer. And a second heat treatment step that sequentially repeats the second step to produce a layered object, and a heat treatment step of holding the layered object at 300 to 800 ° C. Preferably, the heat treatment step includes a first heat treatment step for holding the layered object at a first heat treatment temperature of 500 to 800 ° C. and a temperature of 400 ° C. or more and the first heat treatment temperature after the first heat treatment step. A second heat treatment step of holding at a second heat treatment temperature.

  In another method for producing a copper alloy shaped article of the present invention, Cr: 0.1 to 20% by mass, Zr: 0 to 0.2% by mass, the Cr content is larger than the Zr content, and the balance is Cu and inevitable. Additive manufacturing by sequentially repeating a first step of forming a thin layer of copper alloy powder composed of mechanical impurities and a second step of irradiating an electromagnetic wave beam at a predetermined position of the thin layer to melt and solidify the copper alloy powder A modeling process for manufacturing an object, and a heat treatment process for holding the layered model at 410 to 800 ° C. Preferably, the heat treatment step includes a first heat treatment step of holding the layered object at a first heat treatment temperature of 500 to 800 ° C. and a temperature of 410 ° C. or more and the first heat treatment temperature or less after the first heat treatment step. A second heat treatment step of holding at a second heat treatment temperature.

  In any of the above-described copper alloy shaped article manufacturing methods, the electromagnetic wave beam is preferably laser light.

  The copper alloy shaped article of the present invention is a shaped article having a laminated structure of copper alloys, wherein the copper alloy is Cr: 0.1 to 20% by mass, Zr: 0 to 0.2% by mass, the balance is Cu and Consists of inevitable impurities. And the electrical conductivity in room temperature is 65% IACS or more, or 0.2% yield strength is 150 MPa or more, and tensile strength is 300 MPa or more.

  When the copper alloy powder of the present invention contains Cr, the thermal conductivity is lowered during addition production, and the modeling becomes easy. Furthermore, a Cr phase precipitates during solidification or heat treatment in addition production, and a copper alloy shaped article excellent in mechanical strength, electrical conductivity and thermal conductivity can be produced. According to the layered object heat treatment method or the copper alloy shaped object manufacturing method of the present invention, a copper alloy shaped article excellent in mechanical strength, electrical conductivity and thermal conductivity is produced by a combination of an appropriate copper alloy composition and heat treatment conditions. It becomes possible. According to the copper alloy shaped article of the present invention, higher mechanical strength and / or electrical conductivity / thermal conductivity than the conventional one can be obtained.

It is a figure which shows the shape of the tension test piece which is a laminate-molded article. It is a figure which shows the fall of the electrical conductivity by heat processing. It is a scanning electron microscope (SEM) image of the Cu1.4Cr sample cross section of an Example. It is a figure which shows the result of a two-step heat treatment experiment.

  The copper alloy (Cu alloy) powder of this embodiment is used for addition production by a powder bed fusion bonding method. The Cu alloy contains Cr as an alloy element. Moreover, Zr less than Cr content may be included on the mass% basis. The balance is Cu and inevitable impurities.

  Cr is precipitated at the time of solidification of the combined financial liquid in the addition manufacturing process or in a subsequent heat treatment step, and improves the strength of the Cu alloy by precipitation hardening. In order for Cr to precipitate, the Cr content needs to be larger than the saturated solid solution amount in Cu at room temperature or the subsequent heat treatment temperature, and specifically 0.1 mass% or more. The Cr content is preferably 0.50% by mass or more, more preferably 1.00% by mass or more, and particularly preferably 1.10% by mass or more. This is because the greater the Cr content, the lower the thermal conductivity and the easier the modeling during additive manufacturing. Moreover, Cr content becomes like this. Preferably it is 20 mass% or less. This is because if the Cr content is too large, the precipitated phase tends to be coarsened during the heat treatment and the mechanical properties are impaired. On the other hand, regarding electrical conductivity, the smaller the Cr content, the better. From this point, the Cr content is preferably 20% by mass or less, more preferably 7.5% by mass or less, and particularly preferably 5.0% by mass or less.

Zr is known to improve the intermediate temperature brittleness of Cu alloys by adding a small amount, and is used for the purpose of suppressing the influence of impurities by forming a compound with impurities such as oxygen (O) that lower the thermal conductivity. May be. The Zr content is preferably 0.010% by mass or more. However, the Zr content needs to be smaller than the Cr content on a mass% basis. This is because the Cr precipitation process is not affected. Moreover, Zr content is 0.20 mass% or less. This is because if the Zr content is 0.20% by mass or more, coarse precipitates of intermetallic compounds such as Cr ₂ Zr are likely to be formed, and mechanical properties are impaired.

  The Cu alloy powder of this embodiment may contain other elements as inevitable impurities. However, when the amount of impurity elements increases, the conductivity of the Cu alloy decreases, which may affect the Cr precipitation process, and may cause an unexpected precipitation phase to impair mechanical properties. Therefore, the content of inevitable impurities is preferably 0.1% by mass or less in total.

  The particle size of the Cu alloy powder can be determined according to the method of the additive manufacturing method, the required dimensional accuracy of the modeled object, and the like. When used in a general SLS method or SLM method, the volume-based median value (d50) of the particle diameter measured by a laser diffraction / scattering method is preferably 5 to 200 μm.

  Various known additive manufacturing techniques can be used for producing the layered object. For example, in the SLS method, a first step of forming a thin layer by spreading Cu alloy powder on a modeling stage, and a second step of melting and solidifying the irradiated Cu alloy powder by irradiating a predetermined position of the thin layer with laser light. Are repeated sequentially. Finally, a surplus powder is removed to obtain a layered product of Cu alloy.

  The heat treatment of the layered object is performed by holding the layered object at a predetermined temperature for a predetermined time. The heat treatment may be performed in the air, for example, or may be performed by a hot isostatic pressing method (HIP). By heat treatment, a Cr phase contained in supersaturation is precipitated in the Cu matrix, and mechanical strength, electrical conductivity and thermal conductivity are improved.

  The heat treatment temperature is 300 ° C. or higher, preferably 350 ° C. or higher, more preferably 400 ° C. or higher, and still more preferably 410 ° C. or higher. This is because the effect cannot be obtained if the heat treatment temperature is too low. The heat treatment temperature is particularly preferably 450 ° C. or higher from the viewpoint of improving electrical conductivity, and particularly preferably 500 ° C. or higher from the viewpoint of improving mechanical strength. On the other hand, the heat treatment temperature needs to be lower than the eutectic temperature of Cu and Cr (about 1070 ° C.). Furthermore, even if the heat treatment temperature is lower than the eutectic temperature, if the difference in the eutectic temperature is small, the layered object may be softened and deformed, so the heat treatment temperature is preferably 800 ° C. or lower. Regarding the mechanical strength, the heat treatment temperature is more preferably 600 ° C. or less, particularly preferably 550 ° C. or less. This is because if the heat treatment temperature is too high, the precipitated phase becomes coarse and the 0.2% proof stress and tensile strength decrease.

  The heat treatment time is preferably 5 minutes or longer. This is because a sufficient effect cannot be obtained when the heat treatment time is less than 5 minutes. The heat treatment time is more preferably 10 minutes or more from the viewpoint of mechanical strength, and more preferably 30 minutes or more from the viewpoint of electrical conductivity. On the other hand, if the heat treatment time is too long, it becomes a cost factor, so the heat treatment time is preferably 10 hours or less. Further, from the viewpoint of mechanical strength, if the heat treatment time is too long, the 0.2% proof stress and the tensile strength are lowered. Therefore, the heat treatment time is more preferably 5 hours or less. In terms of electrical conductivity, the longer the heat treatment time, the lower the Cr content of the Cu matrix, which is preferable.

  The effect of heat treatment is theoretically determined by the combination of heat treatment temperature and heat treatment time, but the diffusion rate of Cr in the alloy increases exponentially with increasing temperature, so the heat treatment temperature is set appropriately in practice. It is more important to do.

  The Cu alloy shaped article of the present embodiment is obtained through the above steps. The structure of the Cu alloy shaped article is a shaped article having a laminated structure of Cu alloy, and has a structure in which a Cr phase is precipitated in a parent phase of Cu.

  Next, the embodiment will be described in more detail based on some experimental results.

  Table 1 shows the composition of the Cu—Cr alloy powder used in the experiment together with pure Cu and Cu—Ni alloy powder for comparison. Analysis was performed by ICP emission spectroscopy. Among the components, Zr and Ti are added for the purpose of removing other impurities in a range that does not inhibit the heat treatment effect. The balance other than the elements shown in the table is Cu and unintended inevitable impurities.

  Using each Cu alloy, test pieces for measuring various properties described later were produced by the SLS method. Fabrication was performed using a powder additive manufacturing system (EOS GmbH, M290) using a Yb fiber laser under conditions of a laminate thickness of 0.02 to 0.06 mm and a laser output of 200 to 400W. However, a pure Cu test piece for comparison was produced by the same SLM method.

A test piece for measuring electrical conductivity was formed in a prismatic shape of 3 mm × 3 mm × 80 mm and laminated in the direction of 3 mm thickness. The electrical conductivity was calculated from the electrical resistivity measured by the DC four-terminal method using an electrical resistance measuring device (Agne Technical Center, Inc., ARC-TER-1 type). The measurement was performed in an argon (Ar) atmosphere at room temperature or while maintaining each set temperature described later. In addition, in this specification, electrical conductivity is shown by ratio (% IACS) with respect to annealing standard annealed copper. The electrical resistivity of the annealed standard annealed copper is 1.7241 × 10 ⁻² μΩ · m.

  A test piece for measuring thermal conductivity was produced by laminating coins having a diameter of 10 mm and a thickness of 3 mm in the direction of one diameter. The thermal conductivity was measured in a vacuum using a laser flash method. For some samples, the electrical conductivity was estimated from the thermal conductivity using the following Weedmann-Franz law.

There is a relationship of the following equation between the electrical conductivity and thermal conductivity of a metal, which is known as Wiedemann-Franz law.
K / σ = LT
Here, K: thermal conductivity, σ: electrical conductivity, L: Lorentz number, T: absolute temperature. The Lorentz number (L) is theoretically given by the following equation.
^{L = (π 2/3)} · (k B / e) 2
= 2.44 × 10 ⁻⁸ WΩK ⁻²
Here, k _B : Boltzmann constant, e: elementary electric charge.

  A test piece for measuring mechanical properties had the shape shown in FIG. 2 and was laminated in the longitudinal direction. The measurement of mechanical properties was performed by a tensile test at a room temperature and a strain rate of 0.001 / s using an autograph. Strain measurement was performed using a video non-contact extensometer (Shimadzu Corporation, TRView X120S). The tensile test was performed on three test pieces for each alloy condition (combination of alloy composition and heat treatment condition), and the average was taken as the measurement result.

  In order to investigate the influence of the heat treatment on the layered object, the electrical resistivity was measured in an Ar atmosphere while increasing the temperature stepwise by 50 ° C. using a sample for electrical conductivity measurement. The temperature rising rate between the set temperatures was 60 ° C./min. After reaching each set temperature, the measurement was performed after waiting for several minutes to 10 minutes until the temperature distribution in the sample became uniform. The results are shown in Table 2 in terms of conductivity (% IACS). The temperature was changed from the top to the bottom of Table 2 to 600 ° C., and finally cooled to room temperature (bottom stage). The same result is plotted in FIG. FIG. 2 shows the measured electrical resistivity as it is.

  In Table 2 and FIG. 2, the electrical resistivity of pure Cu increases linearly with increasing temperature. In all the Cu—Cr alloy samples, the electrical resistivity increased with increasing temperature from room temperature, but the slope decreased at 300 ° C. or higher, and the effect of heat treatment was recognized. Above 400 ° C., the effect of heat treatment was clear. In particular, in the samples of Cu0.6Cr and Cu1.4Cr, an electrical resistivity equivalent to that of pure Cu was obtained at 500 ° C. In Cu2.4Ni, the electrical resistivity continued to increase linearly with increasing temperature, and no heat treatment effect was observed in the range up to 600 ° C.

  The difference between Cr and Ni as alloy elements is that the saturated solid solution amount of Cr in Cu is small, whereas Cu and Ni form a solid solution in the entire region. Therefore, it is considered that Cu2.4Ni did not form a precipitated phase even after heat treatment.

  Further, in Patent Document 1, it is considered that the same effect can be obtained even if Si is used as an alloy element. Patent Document 1 does not explain what kind of mechanism improves the characteristics. However, considering that the amount of saturated solid solution of Si in Cu is 4 to 5% by mass, the mechanism is different from this example. I think that the.

  Next, in order to see the effect on the other properties of the heat treatment, three types of test pieces were prepared, and before the heat treatment (as a layered material) and after being held in an Ar stream for 2 hours at 500 ° C. Conductivity measurements, thermal conductivity measurements and tensile tests were performed. The results are shown in Table 3.

  From Table 3, it can be seen that the electrical conductivity and the thermal conductivity were improved by heat treatment at 500 ° C. for 2 hours in all the Cu—Cr alloy samples. In addition, the 0.2% proof stress and tensile strength increased and the elongation at break decreased, suggesting that the change in mechanical properties was due to precipitation hardening. In the Cu-Ni alloy, the electrical conductivity of Cu2.4Ni is not improved by the heat treatment, as explained in the results of Table 2 and FIG. 2, but the mechanical strength of Cu20Ni is not improved by the heat treatment at 500 ° C. for 2 hours. Was confirmed. In addition, although heat processing of pure Cu was not performed, the tensile strength of a commercially available annealing material is about 200 MPa.

  Next, in order to see the influence of the heat treatment temperature, the thermal conductivity and mechanical properties of Cu1.4Cr were measured while changing the heat treatment temperature to 400, 500, 600, and 800 ° C. Both processing times are 2 hours. The results are shown in Table 4. For reference, Table 4 also shows the electrical conductivity calculated from the thermal conductivity using the Wiedemann-Franz law. The leftmost column of Table 4 shows the results of the sample that is not heat-treated (as it is a layered material). The rightmost column of Table 4 shows the results of samples that were heat-treated at 800 ° C. for 2 hours, then water-cooled, and further heat-treated at 500 ° C. for 2 hours.

  From Table 4, the thermal conductivity was remarkably improved by the heat treatment at 400 to 800 ° C. × 2 hours, and in particular, the heat treatment at 600 ° C. × 2 hours was improved to about 4 times that of the laminate-molded material. The 0.2% proof stress was remarkably improved by the heat treatment at 400 to 600 ° C. × 2 hours, and in particular, the heat treatment at 500 ° C. × 2 hours was improved to about 3 times that of the material with the layered molding. The tensile strength was remarkably improved by the heat treatment at 400 to 800 ° C. × 2 hours, and in particular, the heat treatment at 500 ° C. × 2 hours was improved about 2.5 times as much as that of the laminate molding. The elongation at break was reduced by heat treatment, suggesting that changes in these mechanical properties were due to precipitation hardening. The sample subjected to the heat treatment of 800 ° C. × 2 hours + 500 ° C. × 2 hours showed the same mechanical properties as those of the heat treatment of 800 ° C. × 2 hours, and the highest thermal conductivity. In addition, the calculated value of the electrical conductivity calculated from the thermal conductivity was in good agreement with the actually measured value.

  Next, in order to see the influence of the heat treatment time, the thermal conductivity and mechanical properties of Cu1.4Cr were measured by changing the heat treatment temperature to 500 ° C. and changing the time from 5 minutes to 10 hours. The results are shown in Table 5. For reference, Table 5 also shows electrical conductivity calculated from thermal conductivity using Weedmann-Franz law. The leftmost column of Table 5 is the result of the sample (a laminate-molded material) that is not heat-treated.

  From Table 5, the effect has already appeared by the heat treatment for 5 minutes. The thermal conductivity is remarkably improved by heat treatment at 500 ° C. × 5 minutes to 10 hours, reaches about 3 times in 30 minutes, and is improved as the heat treatment time is increased. The 0.2% proof stress was remarkably improved by the heat treatment at 500 ° C. for 5 minutes to 10 hours, and in particular, the heat treatment at 500 ° C. for 30 minutes was improved to 3 times or more of the material with the layered molding. The tensile strength was remarkably improved by the heat treatment at 500 ° C. × 5 minutes to 10 hours, and particularly at the heat treatment of 500 ° C. × 30 minutes, the tensile strength was improved to 2.5 times or more of the material as a layered product. The elongation at break decreased with heat treatment, suggesting that the change in mechanical properties due to heat treatment is due to precipitation hardening.

  Next, the effect of heat treatment on the mechanical properties of Cu5Cr, Cu10Cr, and Cu20Cr was examined. The results are shown in Tables 6-8. Each leftmost column is a result of a sample (a laminate-molded material) that is not heat-treated. Further, each rightmost column shows the results of the samples that were heat-treated at 800 ° C. for 2 hours, then water-cooled, and further heat-treated at 500 ° C. for 2 hours.

  When the results of Tables 6 to 8 are compared with Cu0.6Cr and Cu1.4Cr, the sample having a large Cr content already has high mechanical strength at the stage of the material as a layered model. This is considered to be because when the Cr content is large, the Cr phase is already precipitated during the solidification of the combined financial liquid in the addition manufacturing process. In any of Tables 6 to 8, the mechanical strength is improved by 0.2% proof stress and tensile strength by the heat treatment at 500 ° C, but the mechanical strength is rather lowered by the heat treatment at 800 ° C. On the other hand, the elongation at break is slightly increased by heat treatment at 800 ° C. The mechanical properties after the heat treatment at 800 ° C. × 2 hours + 500 ° C. × 2 hours were not different from those after the heat treatment at 800 ° C. × 2 hours, which is the same as the results in Table 4 for Cu1.4Cr. All of Cu5Cr, Cu10Cr, and Cu20Cr show the same tendency, and it is considered that the mechanical characteristics are changed by the same mechanism by addition manufacturing and heat treatment. Therefore, it was found that this heat treatment method can be applied to a wide composition range.

  Next, cross-sectional scanning electron microscope (SEM) images of several samples were taken. FIG. 3 shows an SEM image of Cu1.4Cr. The length of the white bar under each image is 100 nm.

  From FIG. 3, no precipitates are observed in the material as it is laminated, and the Cr phase is precipitated at 500 ° C. for 5 minutes. This is consistent with the results in Table 5. Moreover, the structure of the as-built material was very similar to that of pure Cu (not shown). Further, in Cu5Cr, a precipitate having a diameter of about several tens to 100 nm was observed even with the material being layered (not shown).

  Next, in order to see the effect of the two-stage heat treatment, the thermal conductivity and mechanical properties of Cu1.5Cr were measured by changing the temperature and time of the first-stage heat treatment. The sample was held at a predetermined temperature for a predetermined time as the first heat treatment, then cooled with water, and held at 500 ° C. for 2 hours as the second heat treatment. The results are shown in Table 9. For reference, Table 9 also shows the electrical conductivity calculated from the thermal conductivity using the Wiedemann-Franz law. The leftmost column of Table 9 shows the results of the sample that is not heat-treated (as it is a layered material). In the following, the first heat treatment is referred to as “first heat treatment”, and the temperature and holding time of the first heat treatment are referred to as “first heat treatment temperature” and “second heat treatment time”, respectively. Similarly, they are referred to as “second heat treatment”, “second heat treatment temperature”, and “second heat treatment time”.

  Among the results in Table 9, the thermal conductivity and 0.2% proof stress of some samples are shown in FIG. Of the numbers on the side of each plot, the upper row is the thermal conductivity and the lower row is the 0.2% yield strength. For reference, FIG. 4 shows the results of a sample obtained by heat-treating Cu1.4Cr having a similar composition at 800 ° C. for 2 hours, water-cooling, and further heat-treated at 500 ° C. for 2 hours.

  From Table 9 and FIG. 4, high thermal conductivity was obtained for the sample having the first heat treatment temperature of 600 ° C. or higher. In simple heat treatment that is not two-stage heat treatment, it can be seen from Table 5 that the longer the holding time at 500 ° C., the higher the thermal conductivity, and the heat conductivity at 300 ° C. × 10 hours was 300 W / m · K. On the other hand, in the two-stage heat treatment in which the second heat treatment is 500 ° C. × 2 hours, if the first heat treatment temperature is 600 ° C. or higher, the simple heat treatment of 500 ° C. × 10 hours is possible even if the first heat treatment time is short. The same or higher thermal conductivity was obtained. When the first heat treatment temperature was 700 ° C. and 800 ° C., the first heat treatment time was 10 minutes, and 365 and 376 W / m · K, respectively, which were very high thermal conductivities were obtained.

  The reason why high thermal conductivity and therefore high electrical conductivity can be obtained by the two-stage heat treatment is not necessarily clear, but Cr phase is precipitated by the first heat treatment, and Cr in the Cu phase as the parent phase is precipitated by the second heat treatment. It is considered that the thermal conductivity and electrical conductivity (hereinafter referred to as “thermal conductivity etc.”) are improved by diffusing into the phase. Therefore, the first heat treatment is preferably performed at a higher temperature in order to promote nucleation of the Cr phase, and the second heat treatment is preferably performed at a lower temperature than the amount of saturated solid solution of Cr in the Cu phase is small.

  Specifically, the preferred range of the second heat treatment temperature is as follows from the results of Table 4. The second heat treatment temperature is preferably 400 ° C. or higher, more preferably 410 ° C. or higher, and particularly preferably 450 ° C. or higher. This is because good thermal conductivity and the like can be obtained in a practical time. On the other hand, the second heat treatment temperature is preferably 800 ° C. or lower, and preferably 600 ° C. or lower in applications where mechanical strength such as 0.2% proof stress and tensile strength is important. The second heat treatment temperature is preferably 600 ° C. or less, particularly preferably 550 ° C. or less from the viewpoint of treatment cost. This is because sufficient thermal conductivity and the like can be obtained even if the treatment is performed at these temperatures.

  From the results in Table 5, the preferred range of the second heat treatment time is as follows. The second heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more. On the other hand, the second heat treatment time is preferably 5 hours or less, more preferably 2 hours or less. This is because the treatment cost can be reduced as the second heat treatment time is shortened, and high thermal conductivity can be obtained by the two-stage heat treatment even if the second heat treatment time is short.

  The first heat treatment temperature is preferably higher than the second heat treatment temperature, more preferably 50 ° C. or more higher than the second heat treatment temperature. Or from the result of Table 9, 1st heat processing temperature becomes like this. Preferably it is 600 degreeC or more, More preferably, it is 650 degreeC or more. This is to promote the generation of Cr phase in a short time. On the other hand, the first heat treatment temperature is preferably 800 ° C. or lower.

  If the layered object reaches the first heat treatment temperature, the first heat treatment time does not need to be maintained at that temperature, and may be 0 minutes. The first heat treatment time is preferably 5 minutes or longer. This is because the Cr phase is reliably generated. On the other hand, the first heat treatment time is preferably 30 minutes or less, more preferably 15 minutes or less. This is because a sufficiently high thermal conductivity and the like can be obtained even in a short time. For example, in Table 9, when the first heat treatment temperature was 700 ° C. and 800 ° C., the maximum thermal conductivity was obtained when the first heat treatment time was 10 minutes.

  Next, for Cu1.5Cr, the thermal conductivity and mechanical properties were measured by changing the transition conditions from the first heat treatment to the second heat treatment. The results are shown in Table 10. The symbols at the top of Table 10 were given to the heat treatment conditions. For each symbol, test pieces for measuring thermal conductivity and measuring mechanical properties were prepared as described above, and heat-treated at the same time. The test piece of the symbol 10-1 reprinted from Table 9 the result of water cooling after the first heat treatment at 600 ° C. for 30 minutes. In the specimen 10-2, the first heat treatment temperature fluctuated between 585 ° C. and 605 ° C. due to experimental problems, and was cooled to 100 ° C. in the furnace after the first heat treatment. At that time, the temperature was lowered to about 300 ° C. in about 3 minutes, but it took about 120 minutes to lower the temperature to 100 ° C. The test piece of symbol 10-3 was cooled to 300 ° C. in about 3 minutes in the furnace after the first heat treatment, and then held at 300 ° C. for 10 minutes. The specimen 10-4 was cooled to 500 ° C. in about 2 minutes in the furnace after the first heat treatment, and subsequently subjected to the second heat treatment at 500 ° C. For reference, Table 10 also shows electrical conductivity calculated from thermal conductivity using Weedmann-Franz law.

  From Table 10, almost the same characteristics were obtained except for the specimen 10-2. From this, it was found that the temperature change during the transition from the first heat treatment to the second heat treatment is not particularly important. For example, when rapid cooling is possible as in this experiment, the temperature can be lowered from the first heat treatment temperature to the second heat treatment temperature, and the second heat treatment can be performed as it is. Alternatively, for example, when the layered product has a large heat capacity and takes time to cool down, the layered product can be once taken out of the furnace and water-cooled.

  The present invention is not limited to the above-described embodiments and examples, and can be modified within the scope of the technical idea.

  For example, in the above-described embodiments and examples, the heat source at the time of additional manufacture is laser light, but an electron beam may be used as the heat source.

Claims (5)

Cr: 1.1 to 20% by mass, Zr: 0 to 0.2% by mass, the balance is a heat treatment method of a layered object that is additionally manufactured using a copper alloy powder composed of Cu and inevitable impurities,
A first heat treatment step of holding the layered object at a first heat treatment temperature of 500 to 800 ° C .;
After the first heat treatment step, there is a second heat treatment step of holding at a second heat treatment temperature that is 400 ° C. or more and lower than the first heat treatment temperature by 50 ° C. or more.
Heat treatment method for layered objects. Heat treatment of a layered object made of a copper alloy consisting of Cr: 0.1 to 20% by mass, Zr: 0 to 0.2% by mass, Cr content greater than Zr content, the balance being Cu and inevitable impurities A method,
A first heat treatment step of holding the layered object at a first heat treatment temperature of 500 to 800 ° C .;
After the first heat treatment step, there is a second heat treatment step of holding at a second heat treatment temperature of 410 ° C. or more and 50 ° C. or more lower than the first heat treatment temperature.
Heat treatment method for layered objects. Cr: 1.1 to 20% by mass, Zr: 0 to 0.2% by mass, the first step of forming a thin layer of copper alloy powder consisting of Cu and inevitable impurities, and at a predetermined position of the thin layer A modeling process for producing a layered object by sequentially repeating a second process of irradiating an electromagnetic wave to melt and solidify the copper alloy powder;
A first heat treatment step of holding the layered object at a first heat treatment temperature of 500 to 800 ° C .;
After the first heat treatment step, there is a second heat treatment step of holding at a second heat treatment temperature that is 400 ° C. or more and lower than the first heat treatment temperature by 50 ° C. or more.
A method for producing a copper alloy shaped article. Cr: 0.1 to 20% by mass, Zr: 0 to 0.2% by mass, Cr content is greater than Zr content, and the remainder forms a thin layer of copper alloy powder consisting of Cu and inevitable impurities A modeling process for producing a layered object by sequentially repeating a first process and a second process of irradiating an electromagnetic wave beam at a predetermined position of the thin layer to melt and solidify the copper alloy powder;
A first heat treatment step of holding the layered object at a first heat treatment temperature of 500 to 800 ° C .;
After the first heat treatment step, there is a second heat treatment step of holding at a second heat treatment temperature of 410 ° C. or more and 50 ° C. or more lower than the first heat treatment temperature.
A method for producing a copper alloy shaped article. The electromagnetic beam is a laser beam,
The manufacturing method of the copper alloy molded article as described in any one of Claim 3 or 4.