JP6287438B2 - Method for manufacturing metal member - Google Patents

Description

The present invention relates to a method for producing a metal member having a dendrite groups on the surface.

  The surface of metal members can be used for various purposes such as improved heat transfer by increasing the contact area, improved adhesion by the anchor effect, improved supportability of active materials and catalysts, and improved adsorbability by increasing the adsorption area. Modification, roughening, etc. are performed. As an example, there is a description related to Patent Document 1 and Patent Document 2 below.

JP 2000-247800 A JP 2012-216513 A JP 2013-168375 A

  Patent Document 1 describes a metal oxide structure in which a protrusion made of a metal oxide is formed on a substrate by sputtering or the like. Patent Document 2 describes a current collector made of an aluminum alloy base material whose surface is electrochemically roughened by direct current application. The protrusions or irregularities formed on the surface of the substrate by these are only relatively simple shapes, and do not necessarily sufficiently increase the surface area, the anchor effect, and the like.

  In addition, although patent document 3 provides the copper powder which made the particle shape dendritic, naturally, the surface of the base | substrate which comprises a member is not roughened.

This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the metal member which formed the fine protrusion group of the shape different from the former on the surface.

  As a result of intensive studies to solve this problem and repeated trial and error, the present inventor made unidirectional solidification of the Al-Sn molten metal on the surface of the Al base material, and then performed etching under specific conditions. We succeeded in obtaining a metal member with a large number of dendrite protrusions made of pure Al standing on the surface of the substrate. By developing this result, the present invention described below has been completed.

《Metal member》
(1) The metal member of the present invention is a metal member having a base made of a pure metal or an alloy, and a surface part integrally formed with the base on the surface of the base, wherein the surface part is A projection made of a pure metal or an alloy of a main metal element which is a main constituent element of the substrate, and a plurality of dendritic projections composed of a trunk standing from the surface of the substrate and branches branched from the backbone. It has a group.

(2) The metal member of the present invention is different from simple granular protrusions and columnar protrusions, and has a group of protrusions having a large number of complicated dendritic protrusions having a backbone and branches branched from the backbone on the surface. Have. By this projection group, the metal member of the present invention can have a surface area much larger than that of the conventional roughened member. Moreover, since this protrusion group has the branch extended in the horizontal direction from the basic | foundation, it has favorable engagement property with the other member, film, etc. which contact, and can exhibit the outstanding adhesiveness or the anchor effect. Furthermore, the projection group forms various microspaces between adjacent backbones or between branches, between the backbone and branches in one projection, etc., so various substances (particles, ions, etc.) It also has excellent retention and support properties.

  The dendritic protrusion according to the present invention is integrated with the base of the metal member. Specifically, first, the backbone is integrally extended from the surface of the base, in other words, it is difficult to specify the boundary surface between the base and the base. For this reason, each backbone is not easily separated from the substrate, broken or the like. Such a state is the same between the base and the branch, and the backbone and each branch connected to the backbone are not easily separated or broken. Since the surface portion is formed by such dendritic protrusions, the metal member of the present invention can stably exhibit the effects described above.

In addition, the dendrite projection assumed in the present invention is basically a fine projection. For example, the thickness of the surface portion (projection group) (more precisely, the average stem height described later) is 1 mm or less, 0.5 mm or less, and further 0.2 mm or less. (Diameter) is 1 mm or less, 100 μm or less, 50 μm or less, and further 20 μm or less. The density of dendrites (the number of backbones per unit area) is, for example, 100 or more, 500 or more, or 1000 or more per 1 mm ² .

<< Method for producing metal member >>
(1) The present invention can be grasped not only as the above metal member but also as a manufacturing method thereof. That is, the present invention solidifies a molten liquid composed of a main metal element which is a main constituent element of the base and one or more alloy elements on the surface of the base made of a pure metal or an alloy in one direction with respect to the surface of the base. A solidification step for forming the solidified layer, and an elution step for selectively eluting the alloy element from the solidified layer to leave a dendritic crystal composed of the main metal element crystallized on the surface of the substrate. It can also be grasped as a method for producing a metal member characterized in that the above-described metal member is obtained.

(2) According to the production method of the present invention, a solidified layer containing dendritic crystals composed of main metal elements integrated on the surface of the substrate is formed in the solidification step. Then, by eluting and removing portions other than the dendritic crystals from the solidified layer in the elution step, dendritic protrusions integrated with the surface of the substrate can be obtained relatively easily.

<Others>
(1) A dendrite or dendritic crystal according to the present invention is an alloy composed of a pure metal composed of a main metal element or a main metal element and a trace amount of inevitable impurities and an alloy element present in a solid solution / precipitated / dispersed state. Preferably there is. Examples of such alloy elements include Si, Mg, Zn, Cu, and Fe.

(2) Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. A range such as “a to b” can be newly established with any numerical value included in various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value.

It is the SEM photograph which observed the dendrite group formed on the substrate surface. It is the SEM photograph which observed the dendrite group from the substrate side. It is the SEM photograph which expanded the dendrite. It is explanatory drawing which showed typically each size which prescribes | regulates the form of the dendrite which concerns on this invention. It is explanatory drawing which showed typically the outer diameter of the backbone which concerns on the dendrite. It is explanatory drawing which showed the root which concerns on this invention typically.

  The contents described in this specification can be applied not only to the metal member of the present invention but also to the manufacturing method thereof. A component related to a manufacturing method can be a component related to an object if understood as a product-by-process claim. One or two or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. Which embodiment is the best depends on the target, required performance, and the like.

《Dendrites / Dendrites》
The dendritic projection according to the present invention is composed of a trunk standing from the surface of the substrate and a branch continuous from the trunk. The dendrite is not limited in its detailed form, but is usually a fine projection having an outer diameter of about 100 μm or less and a height of about 1 mm or less. It is difficult to define in detail the size and form of individual dendrite, and its meaning is poor. Therefore, in the present specification, basically, an average form and the like of the entire projection group including a plurality of dendritic projections is defined.

  The “outer diameter” referred to in this specification is the diameter (D) of a circumscribed circle in contact with the outer shape (outer circumference) of the cross section at a specific position in the extending direction with respect to one trunk (the branch is the same) (see FIG. 2B). The “maximum outer diameter” is the maximum value of the outer diameter (D), that is, the maximum value of the outer diameter (D) in each transverse section in the extending direction with respect to one backbone. The thickness of one backbone is indicated by its maximum outer diameter (Di). In addition, as a group of protrusions, all the dendritic protrusions in a specific region (total number: N) are thickened by the average trunk diameter (Dm = ΣDi / N) obtained by averaging the maximum outer diameters (Di) of the respective trunks. Is indexed (see FIG. 2A).

  In addition, the height of one backbone is the length from the base (base) to the tip of the backbone measured in the normal direction of the surface on which the backbone stands, but the protrusion group is within a specific region. The height of the trunk is indicated by the average trunk height (Hm = ΣHi / N) obtained by averaging the height (Hi) of each trunk with respect to the dendrite (total number: N) (see FIG. 2A). Furthermore, the length of one branch is the straight length from the root (base) to the tip of the branch, but as a group of protrusions, there are dendrites (total number: N) in a specific region. The branch length is indexed by the average branch length (Lm = ΣLi / N) obtained by averaging the lengths (Li) of the branches (see FIG. 2A).

In addition, as shown in FIG. 2C, the “root” in this specification means a line connecting the most concave points (points a and b) between each dendrite (each backbone or each branch) and the vertex of the dendrite. The point of intersection with the perpendicular drawn from the base to the base. Further, the specific region for obtaining the average value for the projection group is selected to include 100 or more, preferably 1000 or more backbones in the region, and is set to an area of about 1 mm ² . The identification of each form (size, etc.) of each dendrite is based on the result of cross-sectional observation using an electron microscope.

  Based on these, the projection group according to the present invention has, for example, an average trunk height (Hm) obtained by averaging the height (Hi) from the root to the tip for each trunk, and the average outer diameter (Di) for each trunk. A columnar protrusion group larger than the diameter (Dm) is preferable. This is because when Hm is larger than Dm, a high anchoring effect and supporting effect due to roughening can be expected.

  Further, in the projection group according to the present invention, the average root diameter (drm) obtained by averaging the outer diameters (dri) at the roots for each trunk is smaller than the average trunk diameter (Dm) obtained by averaging the maximum outer diameters (Di) for each trunk. A group of undercut protrusions is preferable. This is because a remarkable anchor effect can be expected at the joint interface. The outer diameter (dri) at the base of each backbone is the minimum outer diameter that is the minimum value of the outer diameter in the vicinity of the root. The average root diameter (drm) is a value (drm = Σdri / N) obtained by averaging the root outer diameter (dri) with respect to dendritic protrusions (total number: N) in a specific region (see FIG. 2A).

  Further, in the projection group according to the present invention, the average branch length (Lm) obtained by averaging the length (Li) from the root to the tip for each branch is the average trunk diameter (Dm) obtained by averaging the maximum outer diameter (Di) for each backbone. Is preferably 0.1 or more, 0.5 or more, and more preferably 1 or more. This is because the longer the Lm, the larger the surface area and the greater the roughening effect. For example, the branch length ratio (Lm / Dm) is preferably 50 or less, more preferably 10 or less. This is because if Lm is too large compared to Dm, the burden on the backbone becomes a problem, and the density of the backbone decreases.

<Substrate and main metal element>
Regardless of the form of the substrate, an appropriate form is selected according to the use of the metal member. The projection group according to the present invention may be additionally formed on the original surface of the substrate, or the remaining portions other than the dendritic projections are removed from the original surface of the substrate toward the inside (deep part). It may be formed.

  The substrate may be a pure metal or an alloy. Although the main metal element which is the main constituent element can be variously considered, Al is preferable because the metal member of the present invention can be widely used. The main constituent element is an element that is present at 50 atomic% or more with respect to the entire substrate. In the case of the present invention, the dendrites are also preferably made of the main metal element (particularly the pure metal). As a result, the projection group of the present invention is easy to be integrated with the substrate and exhibit sufficient strength, and can be conveniently handled in the same manner as the substrate.

"Production method"
The projection group according to the present invention can be formed by various methods, but the projection group can be efficiently formed by the above-described coagulation step and elution step.

  In the solidification step, a molten liquid (alloy molten metal) in which the main metal element and one or more alloy elements are almost completely melted is introduced (poured) into the surface of the substrate and solidified on the surface. During this cooling process, the main metal element is crystallized as primary crystals, and the primary crystals develop as dendrites. At this time, when the vicinity of the substrate surface in contact with the melt is cooled, the heat flow direction of the melt is opposite to the surface of the substrate, and dendritic crystals developed along the heat flow direction are formed on the surface of the substrate.

  When the alloy elements that do not contribute to the formation of dendrites are selectively eluted from the solidified layer thus obtained, the solidification structure other than the dendrites is removed, and the dendrites composed of the main metal elements become the base. It remains in an integrally bonded state on the surface. The dendrite of the present invention is formed by the remaining dendritic crystals (dendritic crystals). Incidentally, the primary arm of the dendrite is the backbone of the dendrite, and the secondary arm of the dendrite is the branch of the dendrite. The dendritic protrusion according to the present invention may have a dendritic tertiary arm or the like.

  Such dendritic crystals are formed by self-organization of the solidified phase in the process of growing the solidified phase composed of the main metal from the molten alloy. Therefore, when an alloy element dissolved in the solid phase is used as a component of the molten alloy, the dendrites are composed of a main metal containing the alloy element, that is, an alloy. Conversely, if an alloy element that does not dissolve in the solidified phase is used, the dendritic crystal is composed of a pure metal composed of a main metal. As the material of the dendritic crystal, either a pure metal or an alloy can be selected according to the application. For example, for the purpose of modification such as improvement of strength or detoxification of inevitable impurities, an element in which the alloy element is dissolved in the solid phase may be added. When high thermal conductivity or electrical conductivity is required, an alloy element that does not dissolve in the solid phase is preferable, but an element that dissolves may be used if the amount of the solid solution is small. The solid solubility limit is generally difficult to specify, but for example, the maximum solid solution amount with respect to the main metal element in the solidification step is preferably 0.1% by mass or less, and more preferably 0.01% by mass or less.

  As a combination of such elements, for example, the main metal element is preferably Al and the alloy element is Sn. The alloy composition of the melt (alloy molten metal) at this time is preferably Sn: 80 to 95%, the balance: Al, and inevitable impurities, with the total being 100% by mass. If Sn is too small (Al is too much), it is not preferable because it is difficult to form dendrites. Excessive Sn (Al is insufficient) is not preferable because it becomes difficult to form dendrites or the formation amount is too small.

  Since the dendrite has a fine and complicated shape, the elution step is preferably an etching step. As the etching solution (etchant) used at this time, an appropriate one is selected according to the types of the main metal element and the alloy element. However, an etching solution having a dissolution rate of the alloy element larger than at least the dissolution rate of the main metal element is preferable.

When the solidified layer is made of the above-described Al—Sn alloy, it is conceivable to use tetrafluoroboric acid (HBF ₄ ), sulfuric acid (H ₂ SO ₄ ), sodium hydroxide (NaOH), or the like as an etching solution. Such an etching solution easily forms an oxide film (Al ₂ O ₃ ) serving as a protective film on the surface of the dendritic crystals made of Al, and easily elutes Sn while leaving the dendritic crystals remaining. . In order to adjust the dissolution rate of the alloy element or the like, an appropriate energization (for example, application of a DC voltage) may be appropriately applied to the material to be processed (the substrate on which the solidified layer is formed).

<Application>
The metal member of the present invention can be used for various products in various fields. For example, when attention is paid to the size of the surface area, it can be used for a heat exchanger (radiator or the like), its constituent members (fins or the like), an active material carrier or a carrier electrode. Also, paying attention to the peculiarity of the surface shape, super water-repellent member, sliding member, flow control member (laminarization member, turbulent flow member), dirt adhesion prevention member, heat pipe using phase change of water It can be used for gas-liquid separation filters. Furthermore, focusing on the anchor effect of dendrites, etc., it is possible to improve the adhesion to other members and coatings, and the metal member of the present invention can also be used as a joining member of different materials, a covering member having a surface coating, etc. Available. Of course, it is preferable that the form, density, and the like of the dendrites according to the present invention are appropriately adjusted according to each application.

  A sample in which a dendrite group was formed on a substrate was produced as follows. The present invention will be described more specifically based on this sample.

<Production of sample>
(1) A substrate made of a commercially available pure Al plate (A1050) was prepared as a substrate. This base material was heated to 550 ° C. using an electric heater (preheating step). Next, a molten alloy (melt) prepared to Al-90 mass% Sn was prepared. This molten alloy is completely melted by heating to 700 ° C. or higher.

(2) An annular (cylindrical) mold made of SUS304 (JIS) was placed on the upper surface of the substrate. This mold was also preheated in the same manner as the substrate. The molten alloy was poured into the mold. The temperature of the molten alloy during pouring was 660 ° C. After completing the pouring of the molten alloy, it was allowed to stand for 2 minutes. At this time, the temperature of the molten alloy was maintained at 560 ° C.

  Thereafter, the entire lower surface (back surface) of the substrate was brought into contact with the water jacket, and the molten alloy in the mold was cooled and solidified in one direction. When the temperature of the molten alloy reached 240 ° C., the remaining hot water was discharged from the mold, and then the substrate was cooled to room temperature. Thus, an intermediate material having an Al—Sn solidified layer formed on the surface of the base material was obtained.

This intermediate material was immersed in an etching solution, and a DC voltage was applied using the intermediate material as an anode (etching process, elution process). At this time, an HBF ₄ aqueous solution having a concentration of 3.5% by mass was used as the etching solution. Stainless steel (SUS304) was used for the cathode. The applied DC voltage was constant at 10V.

  After performing this etching process for 1 minute and a half (about 90 seconds), the pulled-up sample was immediately washed with pure water. Thus, a sample according to this example was obtained.

<< Observation >>
The photograph which observed the surface (upper surface side of the base material) of the obtained sample with the scanning electron microscope (SEM) was shown to FIG. 1A, and the photograph which observed the cross section (side surface) was shown to FIG. 1B. Moreover, the photograph which expanded a part of the surface was shown to FIG. 1C.

  As is clear from these figures, it can be seen that innumerable dendritic protrusions composed of dendritic crystals are integrally formed on the upper surface of the substrate. These dendrite groups were cut and observed with an SEM. The analyzed range is an area composed of arbitrary 100 lines. As a result, the dendrite group had an average stem height (Hm): 43 μm, an average stem diameter (Dm): 9.3 μm, and an average root diameter (drm): 5.4 μm. Therefore, it was confirmed that the protrusion group of this sample was a columnar protrusion group satisfying Hm> Dm and an undercut protrusion group satisfying drm <Dm.

  It was also confirmed that the protrusion group of this sample had an average branch length (Lm) of 30 μm and an average branch length ratio (Lm / Dm) of 1.5.

Claims (11)

A solidified layer obtained by solidifying a molten liquid composed of a main metal element which is a main constituent element of the base and one or more alloy elements in one direction with respect to the surface of the base on the surface of the base made of a pure metal or an alloy. A solidification process to form;
An elution step of selectively eluting the alloying elements from the solidified layer to leave dendrites crystallized on the surface of the substrate,
And the substrate, a method for producing a metal member having a metal member is obtained having, formed integrally with the surface portion and the base body to the surface of the substrate,
The surface portion is composed of a pure metal or an alloy of a main metal element which is a main constituent element of the base body, and a dendrite formed of a backbone standing from the surface of the base body and branches branched from the base body A method of manufacturing a metal member , wherein a plurality of protrusions are arranged side by side. In the projection group, the average trunk height (Hm) obtained by averaging the height (Hi) from the root to the tip of each trunk is larger than the average trunk diameter (Dm) obtained by averaging the maximum outer diameter (Di) of each trunk. The method for producing a metal member according to claim 1, which is a large columnar protrusion group. The protrusion group has an undercut in which an average root diameter (drm) obtained by averaging the outer diameters (dri) at the roots of the respective trunks is smaller than an average trunk diameter (Dm) obtained by averaging the maximum outer diameters (Di) of the respective trunks. method for producing a metal member according to claim 1 or 2 which is Jo projection group. The protrusion group has an average branch length (Lm) obtained by averaging lengths (Li) from the root to the tip of each branch, with respect to an average trunk diameter (Dm) obtained by averaging the maximum outer diameter (Di) of each backbone. The method for producing a metal member according to any one of claims 1 to 3, wherein the metal member is 0.1 or more. The method of manufacturing a metal member according to any one of claims 1 to 4, wherein the protrusion group has an average trunk height (Hm) obtained by averaging a height (Hi) from a root to a tip of each trunk. The method for producing a metal member according to any one of claims 1 to 5, wherein the protrusion group has an average trunk diameter (Dm) obtained by averaging the maximum outer diameters (Di) for each of the trunks, which is 100 µm or less. The said elution process is an etching process, The manufacturing method of the metal member in any one of Claims 1-6 . The main metal element is an element that produces primary crystals from the melt,
The alloying element, method for producing a metal member according to claim 1 is an element that does not substantially dissolved in the main metal element. Method for producing a metal member according to any of the main metal element Al der Ru claim 1-8. Before SL dendritic protrusions, producing a metallic component according to claim 9 consisting of Al or Al alloy. The method for manufacturing a metal member according to claim 9 or 10, wherein the alloy element is Sn.