JP6541901B1 - Heat treatment method for laminate shaped article and method for producing shaped copper alloy article - Google Patents

Abstract

[Summary] [Problem] To provide a copper alloy shaped article having higher mechanical strength and / or electrical conductivity / thermal conductivity, and a copper alloy powder capable of producing such a copper alloy shaped article. [Solution] This is a copper alloy powder for additive production, which is a copper alloy powder comprising 1.1 to 20% by mass of Cr, 0 to 0.2% by mass of Zr and the balance Cu and unavoidable impurities. In addition, it is a three-dimensional object having a laminated structure of a copper alloy, wherein the copper alloy is made of Cr: 0.1 to 20% by mass, Zr: 0 to 0.2% by mass, and the balance is Cu and unavoidable impurities The copper alloy shaped article has an electrical conductivity of at least 65% IACS, or a 0.2% proof stress of at least 150 MPa and a tensile strength of at least 300 MPa.

Description

  The present invention relates to an additive manufacturing technology of metal by powder bed fusion bonding method, and more specifically, copper alloy powder as a raw material, a heat treatment method of laminate shaped article manufactured by additive production, copper alloy shaped article including the heat treatment step The present invention relates to a manufacturing method and a copper alloy shaped article.

  As a method of producing a three-dimensional shaped object of metal, additional production technology, so-called 3D printing technology has attracted attention. Among them, the additive manufacturing method by powder bed fusion bonding method repeatedly lays down the metal powder as the raw material on the modeling stage, irradiates the laser beam and the electron beam to the predetermined position, melts and solidifies the metal powder, and laminates it. Is a method of forming a three-dimensional shape. Typical methods include laser sintering (SLS, Selective Laser Sintering) and laser melting (SLM, Selective Laser Melting). By this method, it has become possible to manufacture in a relatively short time products having complicated shapes that could not be produced by conventional cutting and the like.

  One of the problems in the additive manufacture of metal is that it is difficult to manufacture a product utilizing copper's excellent electrical conductivity and thermal conductivity. The main reason is that the energy absorption rate of copper for the wavelength of laser light (for example, 1090 nm for Yb fiber laser) is extremely low, and heat can not be reached rapidly because heat conduction is high even if it can reach the melting point. It is that it spreads and sufficient melting does not proceed.

  On the other hand, Patent Document 1 contains 0.10% by mass or more and 1.00% by mass or less of at least one of chromium and silicon, and the total amount of the chromium and the silicon is 1.00% by mass or less. There is described a copper alloy powder for additive manufacturing, the remainder being made of copper. By using this copper alloy powder, it is possible to manufacture a laminate-molded article compatible in mechanical strength and conductivity (electrical conductivity). Further, Patent Document 1 describes that the mechanical properties and the conductivity are improved by subjecting the laminate-molded article to heat treatment.

Patent No. 6030186

  According to the example of Patent Document 1, the compounding of chromium or silicon can provide a laminate molding material having a tensile strength of 186.74 to 281.41 MPa and a conductivity of 23.59 to 60.42% IACS. ing. Moreover, the conductivity is improved to 26.25 to 64.27% IACS by heat treatment at 300 ° C. for 3 hours in a nitrogen atmosphere.

  However, in the shaped article described in Patent Document 1, there is room for further improvement in any of mechanical strength and conductivity. Also, although the conductivity was slightly improved by the heat treatment at 300 ° C. for 3 hours, the effect of the heat treatment was not sufficient. In the sample with high conductivity (Table 5), the tensile strength is small, and in the sample with high tensile strength (Tables 6 and 7), the conductivity is as low as 23.59% to 38.12%. It is desirable to make the sex compatible at a higher level.

  The present invention has been made in consideration of the above, and it is an object of the present invention to provide a copper alloy shaped article having mechanical strength and / or electrical conductivity / thermal conductivity higher than that of the conventional one by additive manufacturing. Another object of the present invention is to provide a copper alloy powder capable of producing such a copper alloy shaped article, a heat treatment method for a laminate shaped article, and a method for producing a copper alloy shaped article.

  The present inventors obtained the following findings as a result of earnest research. The amount of saturated solution of chromium (Cr) to copper (Cu) is small, less than 0.7% by mass at eutectic temperature of about 1070 ° C, and it is said to be less than 0.1 mass at 500 ° C or room temperature. ing. Therefore, if the additive manufacturing is performed using the Cu alloy containing 0.1 mass% or more of Cr, since the thermal conductivity is lower than that of pure copper (pure Cu), modeling becomes easy. By rapid cooling at the time of additive production, the layered shaped as-formed material contains supersaturated Cr in the Cu phase. When the layered product is appropriately heat-treated, the Cr phase is precipitated in the parent phase of Cu, and the Cr concentration of the parent phase is reduced to improve the electrical conductivity and the thermal conductivity. At the same time, the mechanical strength of the shaped article is also improved by the precipitation hardening action due to the Cr phase precipitation. In addition, when the Cr concentration in the original Cu alloy is high to a certain extent, the Cr phase precipitates at the stage of the material as laminated modeling, but also in this case, the Cr concentration of the matrix decreases due to the heat treatment. Improves the quality.

  Based on this finding, in the present invention, a Cu-Cr alloy powder suitable for heat treatment of additive manufacturing and the obtained laminate-molded article, a heat treatment method of laminate-molded article, a method of producing a copper alloy molded object combining additive manufacturing and heat treatment It has become 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 laminate molding, wherein Cr: 1.1 to 20% by mass, Zr: 0 to 0.2% by mass, the balance is Cu and unavoidably It consists of impurities.

  The laminate shaped article heat treatment method of the present invention is a heat treatment method of a laminate shaped article additionally manufactured using the above-mentioned copper alloy powder, and has a heat treatment step of holding the laminate shaped article at 300 to 800 ° C. Preferably, in the heat treatment step, a first heat treatment step of holding the layered product 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 or less after the first heat treatment step. And a second heat treatment step of holding at a certain second heat treatment temperature.

  Another layered shaped product heat treatment method of the present invention is a heat treating method of a layered shaped object made of a copper alloy, wherein the copper alloy comprises 0.1 to 20% by mass of Cr and 0 to 0.2% by mass of Zr. The content of Cr is greater than the content of Zr, and the balance is Cu and unavoidable impurities, and has a heat treatment step of holding the layered object at 410 to 800 ° C. Preferably, the heat treatment step is a first heat treatment step of holding the layered product 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. And a second heat treatment step of holding at a certain second heat treatment temperature.

  The method for producing a copper alloy shaped article according to the present invention comprises the first step of forming a thin layer of the copper alloy powder according to the present invention, and irradiating an electromagnetic wave beam to a predetermined position of the thin layer to melt and solidify the copper alloy powder. And a heat treatment step of holding the layered object at 300 to 800 ° C. Preferably, in the heat treatment step, a first heat treatment step of holding the layered product 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 or less after the first heat treatment step. And a second heat treatment step of holding at a certain second heat treatment temperature.

  Another method for producing a copper alloy shaped article according to the present invention is as follows: 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, and the balance is Cu and unavoidable The first step of forming a thin layer of copper alloy powder consisting of organic impurities and the second step of dissolving and solidifying the copper alloy powder by irradiating an electromagnetic wave beam at a predetermined position of the thin layer are sequentially repeated It has a modeling process which produces a thing, and a heat treatment process which holds the layered model at 410-800 ° C. Preferably, the heat treatment step is a first heat treatment step of holding the layered product 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. And a second heat treatment step of holding at a certain second heat treatment temperature.

  In any of the above methods for producing a copper alloy shaped article, preferably, the electromagnetic wave beam is a laser beam.

  The copper alloy shaped article of the present invention is a shaped article having a laminated structure of a copper alloy, wherein the copper alloy comprises 0.1 to 20% by mass of Cr, 0 to 0.2% by mass of Zr, and the balance is Cu. It consists of unavoidable impurities. And, the electric conductivity at room temperature is 65% IACS or more, or the 0.2% proof stress is 150 MPa or more, and the tensile strength is 300 MPa or more.

  Since the copper alloy powder of the present invention contains Cr, the thermal conductivity is lowered at the time of additive production, and shaping becomes easy. Furthermore, Cr phase precipitates during solidification or heat treatment of additive manufacturing, and it becomes possible to produce a copper alloy shaped article excellent in mechanical strength, electrical conductivity and thermal conductivity. According to the laminate shaped article heat treatment method or copper alloy shaped article production 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, mechanical strength and / or electrical conductivity / thermal conductivity higher than those of the prior art 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 two-step heat treatment experiment.

  The copper alloy (Cu alloy) powder of the present embodiment is used for additive manufacture by a powder bed fusion bonding method. The Cu alloy contains Cr as an alloying element. In addition, Zr may be contained in an amount of less than the Cr content on a mass percent basis. And the remainder is Cu and an unavoidable impurity.

  Cr precipitates during solidification of the coking liquid in the additive manufacturing process or in a subsequent heat treatment step, and improves the strength of the Cu alloy by precipitation hardening. In order to precipitate Cr, the Cr content needs to be larger than the saturated solid solution amount to Cu at room temperature or a heat treatment temperature later, and specifically, it is 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. The higher the Cr content, the lower the thermal conductivity, and the easier the shaping at the time of additive production. Also, the Cr content is preferably 20% by mass or less. If the content of Cr is too large, the precipitated phase tends to be coarsened during heat treatment, and the mechanical properties are impaired. On the other hand, with regard to the electrical conductivity, the smaller the Cr content, the better. From this point of view, 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.

It is known that Zr improves the intermediate temperature brittleness of Cu alloy by the addition of a small amount, and is used for the purpose of forming a compound with impurities such as oxygen (O) which lowers the thermal conductivity to suppress the influence of the impurities There is something to be done. 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. It is for not affecting the precipitation process of Cr. Moreover, Zr content is 0.20 mass% or less. If the Zr content is 0.20 mass% or more, coarse precipitates of intermetallic compounds such as Cr ₂ Zr are easily formed, and the mechanical properties are impaired.

  The Cu alloy powder of the present embodiment may contain other elements as unavoidable impurities. However, if the content of impurity elements is large, the conductivity of the Cu alloy may be lowered to affect the precipitation process of Cr, and an unexpected precipitation phase may be formed to impair the mechanical properties. Therefore, the content of unavoidable impurities is preferably 0.1 mass% or less in total.

  The particle size of the Cu alloy powder can be determined in accordance with the type of additive manufacturing method, the dimensional accuracy of the desired object, and the like. When using for a general SLS method and SLM method, Preferably, the volume-based median value (d50) of the particle size measured by the laser diffraction and scattering method is 5-200 micrometers.

  Various well-known addition manufacturing techniques can be used for preparation of a laminate-molded article. For example, in the SLS method, a first step of forming a thin layer by laying a Cu alloy powder on a forming stage, and a second step of dissolving and solidifying the irradiated Cu alloy powder by irradiating a predetermined position of the thin layer with laser light And repeat sequentially. Finally, the excess powder is removed to obtain a layered product of Cu alloy.

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

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

  The heat treatment time is preferably 5 minutes or more. If the heat treatment time is less than 5 minutes, a sufficient effect can not be obtained. 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, cost will be a factor, so the heat treatment time is preferably 10 hours or less. Further, from the viewpoint of mechanical strength, the 0.2% proof stress and tensile strength decrease if the heat treatment time is too long, so the heat treatment time is more preferably 5 hours or less. In addition, regarding electric conductivity, since the Cr content of the Cu matrix decreases as the heat treatment time becomes longer, it is preferable.

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

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

  The above embodiments will now be described in more detail by means of several experimental results.

  The composition of the Cu-Cr alloy powder used for experiment is shown in Table 1 with the pure Cu and Cu-Ni alloy powder for comparison. The analysis was performed by ICP emission spectrometry. Among the components, Zr and Ti are added in a small amount within the range not to inhibit the heat treatment effect for the purpose of removing other impurities. The balance other than the elements shown in the table is Cu and unintended unavoidable impurities.

  The test piece for the various characteristic measurement mentioned later was produced by SLS method using each Cu alloy. The production was performed under the conditions of a laminated thickness of 0.02 to 0.06 mm and a laser output of 200 to 400 W, using a powder layered manufacturing system (EOS GmbH, M290) using a Yb fiber laser. However, pure Cu test pieces for comparison were produced by the same SLM method.

A test piece for measurement of electrical conductivity was prepared by laminating in a direction of 3 mm in thickness in a square column of 3 mm × 3 mm × 80 mm. Electrical conductivity was computed from the electrical resistivity measured by the direct current | flow four-terminal method using electrical resistance measuring apparatus (AGNE technology center, ARC-TER-1 type | mold). The measurement was performed in an argon (Ar) atmosphere at room temperature or while maintaining each set temperature described later. In the present specification, the electrical conductivity is shown as a ratio (% IACS) to annealed standard soft copper. The electrical resistivity of the annealed standard soft copper is 1.7241 × 10 ⁻² μΩ · m.

  A test piece for thermal conductivity measurement was produced by laminating in the direction of one diameter in a coin shape having a diameter of 10 mm and a thickness of 3 mm. The measurement of thermal conductivity was performed in 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 the following relationship between the electrical conductivity and the thermal conductivity of metal, and is known as the Weedmann-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 W Ω K ^-2
Here, k _B : Boltzmann's constant, e: elementary electric charge.

  The test pieces for measuring the mechanical properties had the shape shown in FIG. 2 and were produced by laminating in the longitudinal direction. The measurement of mechanical properties was carried out by using an autograph, at room temperature, by a tensile test at a strain rate of 0.001 / s. Strain measurement was performed using a video non-contact extensometer (TRView X120S, Shimadzu Corporation). The tensile test was conducted 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 laminate-molded article, the electrical resistivity was measured in an Ar atmosphere while raising the temperature stepwise by 50 ° C. using a sample for electrical conductivity measurement. The heating rate between each set temperature was 60 ° C./minute, and after reaching each set temperature, 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 top to bottom in Table 2 to 600 ° C. and finally cooled to room temperature (bottom stage). Also, the same results are shown 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 temperature rise. In all the samples of the Cu-Cr alloy, the electrical resistivity increases as the temperature rises from room temperature, but the inclination becomes smaller at 300 ° C. or higher, and the effect of the heat treatment is recognized. Above 400 ° C., the effect of the heat treatment was clear. In particular, in the samples of Cu0.6Cr and Cu1.4Cr, an electrical resistivity equal to that of pure Cu was obtained at 500 ° C. In Cu 2.4 Ni, the electrical resistivity continued to increase linearly with temperature rise, and the effect of heat treatment was not observed in the range up to 600 ° C.

  The difference between Cr and Ni as alloying elements is that Cu and Ni form a solid solution over the entire area, while the saturated solution amount of Cr to Cu is small. Therefore, it is considered that in Cu 2.4 Ni, no precipitate phase was formed even when heat treatment was performed.

  Further, in Patent Document 1, using Si as an alloying element is considered to have the same effect. Although patent document 1 does not explain by what mechanism a characteristic is improved, the mechanism is different from the present example, considering that the saturated solid solution amount of Si to Cu is 4 to 5% by mass. I think that the.

  Next, in order to see the effect of heat treatment on other properties, three kinds of test pieces are prepared, and they are held in an Ar air flow at 500 ° C. for 2 hours before heat treatment (laminated as-formed material) and electric Conductivity measurements, thermal conductivity measurements and tensile tests were performed. The results are shown in Table 3.

  It can be seen from Table 3 that in all the samples of the Cu-Cr alloy, the electric conductivity and the thermal conductivity were improved by the heat treatment at 500 ° C. for 2 hours. In addition, as the 0.2% proof stress and tensile strength increase, the breaking elongation decreases and it is suggested that the change in mechanical properties is due to precipitation hardening. In the Cu-Ni alloy, although the results of Table 2 and FIG. 2 explain that the electric conductivity of Cu 2.4 Ni is not improved by the heat treatment, the mechanical strength is not improved by heat treatment at 500 ° C. for 2 hours also for Cu 20 Ni. Was confirmed. In addition, although heat processing of pure Cu was not performed, the tensile strength of a commercial annealing material is about 200 Mpa.

  Next, in order to see the influence of the heat treatment temperature, the thermal conductivity and the mechanical properties were measured with Cu1.4Cr while changing the heat treatment temperature to 400, 500, 600 and 800 ° C. The processing time is 2 hours in each case. The results are shown in Table 4. For reference, Table 4 also shows the electrical conductivity calculated from the thermal conductivity using Weedmann-Franz's law. The leftmost column of Table 4 is the result of the sample not subjected to the heat treatment (laminated and formed material). The rightmost column of Table 4 shows the results of the samples which were treated with heat 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 significantly improved by the heat treatment at 400 to 800 ° C. for 2 hours, and in particular, the heat conductivity at 600 ° C. for 2 hours was improved to about 4 times that of the material as laminated and formed. The 0.2% proof stress was remarkably improved by the heat treatment at 400 to 600 ° C. for 2 hours, and in particular, the heat treatment at 500 ° C. for 2 hours was improved to about 3 times that of the as-molded laminate. The tensile strength was significantly improved by the heat treatment at 400 to 800 ° C. for 2 hours, and in particular, the heat treatment at 500 ° C. for 2 hours was improved to about 2.5 times that of the as-molded laminate. The elongation at break was reduced by the heat treatment, suggesting that changes in these mechanical properties are due to precipitation hardening. The sample subjected to the heat treatment at 800 ° C. × 2 hours + 500 ° C. × 2 hours exhibited mechanical properties similar to those of the heat treatment at 800 ° C. × 2 hours, and the thermal conductivity showed the highest value. In addition, the calculated value of the electrical conductivity calculated from the thermal conductivity was in good agreement with the measured value.

  Next, in order to see the influence of heat treatment time, the heat conductivity and mechanical properties were measured for Cu1.4Cr 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 the electrical conductivity calculated from the thermal conductivity using Weedmann-Franz's law. The leftmost column of Table 5 is the result of the sample not subjected to the heat treatment (laminated and formed material).

  From Table 5, the heat treatment for 5 minutes already shows the effect. The thermal conductivity is significantly improved by heat treatment at 500 ° C. × 5 minutes to 10 hours, reaches about 3 times in 30 minutes, and improves as the heat treatment time becomes longer. The 0.2% proof stress is remarkably improved by the heat treatment at 500 ° C. × 5 minutes to 10 hours, and in particular, in the heat treatment at 500 ° C. × 30 minutes, it has improved to three times or more of the layered shaped as it is. The tensile strength is significantly improved by heat treatment at 500 ° C. × 5 minutes to 10 hours, and in particular, by heat treatment at 500 ° C. × 30 minutes, it has improved to 2.5 times or more of the laminated and shaped material. The elongation at break was reduced by the heat treatment, suggesting that the change in mechanical properties due to the heat treatment is due to precipitation hardening.

  Next, with respect to Cu5Cr, Cu10Cr, and Cu20Cr, the influence of the heat treatment on the mechanical properties was examined. The results are shown in Tables 6-8. The leftmost column of each shows the result of the sample not subjected to the heat treatment (the laminated as-formed material). Further, the rightmost column of each shows the results of the samples subjected to heat treatment at 800 ° C. for 2 hours, then water cooling, 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 high Cr content already has high mechanical strength at the stage of the as-fabricated material. This is considered to be due to the fact that the Cr phase is already precipitated when the coking liquid is solidified in the addition manufacturing process if the Cr content is high. Moreover, although mechanical strength improves both 0.2% proof stress and tensile strength by heat processing at 500 degreeC also in any of Tables 6-8, mechanical strength is falling rather by heat processing at 800 degreeC. On the other hand, the breaking elongation is slightly increased by the heat treatment at 800 ° C. The mechanical properties after heat treatment at 800 ° C. × 2 hours + 500 ° C. × 2 hours are the same as those after heat treatment at 800 ° C. × 2 hours, as in the results of Table 4 for Cu1.4Cr. Cu5Cr, Cu10Cr, and Cu20Cr all show the same tendency, and it is considered that the mechanical characteristics are changed by the same mechanism by the additive manufacturing and the heat treatment. Therefore, it was found that this heat treatment method can be applied to a wide composition range.

  Next, scanning electron microscope (SEM) images of cross sections were taken for several samples. The SEM image of Cu1.4Cr is shown in FIG. The length of the white bar below each image is 100 nm.

  As shown in FIG. 3, in the as-molded laminate material, no precipitate is observed, and a Cr phase precipitates at 500 ° C. × 5 minutes. This is consistent with the results in Table 5. In addition, the structure of the as-molded material was similar to that of pure Cu (not shown). In addition, with Cu5Cr, precipitates with a diameter of several tens to about 100 nm were observed even in the case of layered modeling (not shown).

  Next, in order to see the effect of the two-step heat treatment, the thermal conductivity and mechanical properties were measured for Cu1.5Cr by changing the temperature and time of the first-step heat treatment. The sample was held at a predetermined temperature for a predetermined time as the first heat treatment, then was water cooled, and was held at 500 ° C. for two 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 Weedmann-Franz's law. The leftmost column of Table 9 is the result of the sample not subjected to the heat treatment (laminated and formed material). In the following, the first heat treatment is referred to as “first heat treatment”, the temperature and holding time of the first heat treatment are referred to as “first heat treatment temperature”, and the “second heat treatment time”, respectively. Similarly, it is referred to as "second heat treatment", "second heat treatment temperature", and "second heat treatment time".

  Among the results of Table 9, the thermal conductivity and 0.2% proof stress of some samples are shown in FIG. Of the numbers beside each plot, the top is the thermal conductivity and the bottom is the 0.2% proof stress. For reference, FIG. 4 shows again the results of the samples which were subjected to heat treatment at 800 ° C. for 2 hours, followed by water cooling, and further heat treated at 500 ° C. for 2 hours.

  From Table 9 and FIG. 4, high thermal conductivity was obtained by the sample whose first heat treatment temperature is 600 ° C. or higher. According to Table 5, in the simple heat treatment which is not a two-step heat treatment, the longer the holding time at 500 ° C., the higher the thermal conductivity, and the heat conductivity of 300 W / m · K for the heat treatment at 500 ° C. × 10 hours. On the other hand, in the two-step heat treatment in which the second heat treatment is performed at 500 ° C. × 2 hours, if the first heat treatment temperature is 600 ° C. or more, the simple heat treatment at 500 ° C. × 10 hours even if the first heat treatment time is short. An equivalent or higher thermal conductivity was obtained. In addition, when the first heat treatment temperature was 700 ° C. and 800 ° C., the first heat treatment time was 10 minutes, and a very high thermal conductivity of 365 and 376 W / m · K was obtained, respectively.

  Although the reason why high thermal conductivity and thus high electrical conductivity can be obtained by the two-step heat treatment is not always clear, the Cr phase is precipitated by the first heat treatment, and the Cr in the parent phase Cu is precipitated by the second heat treatment. It is thought that the thermal conductivity and the electrical conductivity (hereinafter referred to as "the thermal conductivity etc.") are improved by the diffusion into the phase. From this, it is preferable that the first heat treatment be performed at a higher temperature to promote nucleation of the Cr phase, and the second heat treatment be performed at a lower temperature because the amount of the saturated 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 more, more preferably 410 ° C. or more, and particularly preferably 450 ° C. or more. 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 less, and is preferably 600 ° C. or less 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 the treatment cost. Even if it processes at these temperatures, sufficient thermal conductivity etc. are obtained.

  The preferable range of the second heat treatment time is as follows from the results of Table 5. 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 processing cost can be reduced as the second heat treatment time is shorter, and high thermal conductivity and the like can be obtained by the two-step 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, and more preferably 50 ° C. or more higher than the second treatment temperature. Alternatively, from the results in Table 9, the first heat treatment temperature is preferably 600 ° C. or more, more preferably 650 ° C. or more. It is for promoting the formation of Cr phase in a short time. On the other hand, the first heat treatment temperature is preferably 800 ° C. or less.

  The first heat treatment time is not particularly required to be held at the first heat treatment temperature when the layered product reaches the first heat treatment temperature, that is, it may be 0 minutes. The first heat treatment time is preferably 5 minutes or more. This is to ensure that the Cr phase is 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 can be obtained even in a short time. For example, in Table 9, when the first heat treatment temperature is 700 ° C. and 800 ° C., the maximum heat conductivity is obtained when the first heat treatment time is 10 minutes.

  Next, with respect to Cu1.5Cr, the transition conditions from the first heat treatment to the second heat treatment were changed, and the thermal conductivity and the mechanical characteristics were measured. The results are shown in Table 10. The symbols in the top row of Table 10 are given for the heat treatment conditions, and for each symbol, test pieces for thermal conductivity measurement and mechanical property measurement were produced as described above, and simultaneously heat treated. The test piece of symbol 10-1 has been water-cooled after the first heat treatment at 600 ° C. for 30 minutes. The test piece of the symbol 10-2 had the first heat treatment temperature varied 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 drop to 100 ° C. The test piece of symbol 10-3 was held at 300 ° C. for 10 minutes after cooling to 300 ° C. in about 3 minutes in a furnace after the first heat treatment. The test piece of symbol 10-4 was subjected to the second heat treatment at 500 ° C. after cooling to 500 ° C. in about 2 minutes in the furnace after the first heat treatment. For reference, Table 10 also shows the electrical conductivity calculated from the thermal conductivity using Weedmann-Franz's law.

  From Table 10, substantially the same characteristics were obtained except for the test piece of symbol 10-2. From this, it was found that the temperature change at the time of transition from the first heat treatment to the second heat treatment was 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 heat capacity of the laminate-molded article is large and it takes a long time to cool, the laminate-molded article can be once taken out of the furnace and water-cooled.

  The present invention is not limited to the embodiments and examples described above, and modifications are possible within the scope of the technical idea thereof.

  For example, although the heat source at the time of additional manufacturing is the laser light in the above embodiment and examples, an electron beam may be used as the heat source.

Claims (5)

A heat treatment method of a laminate-molded article additionally manufactured using a copper alloy powder comprising 1.1 to 20% by mass of Cr, 0 to 0.2% by mass of Zr and the balance of Cu and unavoidable 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 which is 400 ° C. or more and 50 ° C. or more lower than the first heat treatment temperature .
Heat treatment method of layered product. Heat treatment of a laminate shaped article comprising a copper alloy containing 0.1 to 20% by mass of Cr, 0.1 to 0.2% by mass of Zr, a content of Cr greater than that of Zr, and the balance being Cu and unavoidable impurities 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 which is 410 ° C. or more and 50 ° C. or more lower than the first heat treatment temperature .
Heat treatment method of layered product. 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 unavoidable impurities as the balance, and at a predetermined position of the thin layer Forming a laminate-molded product by sequentially repeating the second step of melting and solidifying the copper alloy powder by irradiating an electromagnetic wave beam;
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 which is 400 ° C. or more and 50 ° C. or more lower than the first heat treatment temperature .
Method of producing a copper alloy shaped article 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, and the remainder forms a thin layer of copper alloy powder consisting of Cu and unavoidable impurities A forming step of producing a laminate-molded article by sequentially repeating a first step and a second step of dissolving and solidifying the copper alloy powder by irradiating an electromagnetic wave beam to a predetermined position of the thin layer;
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 which is 410 ° C. or more and 50 ° C. or more lower than the first heat treatment temperature .
Method of producing a copper alloy shaped article The electromagnetic wave beam is a laser beam,
The manufacturing method of the copper alloy molded article as described in any one of Claim 3 or 4.