JP3115982B2 - Method for producing titanium ring for electrodeposition drum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium ring used for a rotating drum cathode of a foil making apparatus for producing a metal foil such as a copper foil and a nickel foil by an electrolytic plating method.

[0002]

2. Description of the Related Art Titanium as a material for a rotating drum cathode used in the production of metal foil, mainly electrolytic copper foil for printed wiring boards, is disclosed in JP-B-46-90 and JP-B-58-24507. As described above, it is widely used because of its excellent corrosion resistance and good releasability of electrodeposited metal foil. As shown in FIG. 1, in an apparatus for producing an electrolytic copper foil using titanium as an electrodeposition surface, a rotating drum cathode 2 is set on a drum bearing 3 at the center of a bathtub 1 serving as a vessel for a copper plating solution, and the volume of the rotating drum cathode 2 is approximately 1 / 2 is immersed in an electrolytic solution 5 and a direct current is passed through a rectifier 7 between the anode 6 disposed facing the cathode through a rectifier 7 so that copper is plated on the titanium surface that has entered the bath from one side of the plating bath. Began to be, and after it became a copper foil of a predetermined thickness until it came out of the bath surface on the other side,
It is peeled off from the titanium surface and wound on a bobbin to be manufactured continuously.

FIG. 2 is a partially cutaway front view of a rotating drum cathode, whose typical dimensions are a titanium plate thickness of 5 to 8 mm and a diameter of 2 to 2 mm.
A titanium ring 10 is fitted to the outside of an inner drum 9 made of mild steel, which is 3 m in width and 1 to 3 m in width and centered on a rotating shaft 8. . When the thickness reduction due to corrosion and abrasion reaches 30 to 50% of the initial thickness, the pressure force applied to the inner drum surface becomes uneven, resulting in uneven electrical contact resistance. Due to problems such as discoloration due to local overheating, the life is renewed. Titanium rings used for this type of rotating drum cathode are today manufactured in two ways: One is a method in which a hot or cold-rolled titanium plate is rolled into a cylindrical shape by a roll forming machine, and the opposite ends of the plate are butted together and welded by plasma welding or the like. The ring rolling method uses a ring rolling mill to form a seamless ring without welds, but each method has advantages and disadvantages.

[0004] The disadvantage is that, with respect to the welding method, a base material having a crystal grain size of No. 6 to 8 of ASTME112 and a crystal structure having an equiaxed α-crystal structure is welded to a welded joint (hereinafter referred to as a weld zone). The welded part in the above becomes a saw-tooth coarse solidified structure as it is melt-solidified, and the heat-affected zone in contact with it changes to a transformed structure or a high temperature close to the transformed point caused by being heated to a temperature exceeding the β transformation point. It becomes a coarse-grained structure grown by heating and has different corrosion and wear properties from the base material.

For details of such macrostructures and hardness distributions of the welded metal portion, the heat-affected zone, and the base metal portion in the section of the titanium welded joint, see, for example,
As shown in P-110, Photo 4-2 (1992), edited by Titanium Association, when used as a drum cathode as it is, solidification of the weld and heat-affected zone on copper foil electrodeposited on titanium surface
The difference in the texture of the transformed structure and the roughness of the polished surface is transferred, and the quality specified for the copper foil for printed wiring boards is rejected.

Therefore, regarding the welding method, post-treatments for approximating the transformed structure of the weld zone to the base metal portion, for example, JP-A-2-243790, JP-A-4-36488, JP-A-4-62872 are conventionally used.
Requires the organizational adjustment process proposed in the issue. These are all known principles in metallurgy, for example, shown in the Handbook of Metals, edited by The Japan Institute of Metals, Maruzen (1960) P-518, FIG. As can be seen from the phenomenon that the initial crystal grains of a single-phase metal such as austenite or ferrite are recrystallized by rolling and heat treatment and are refined under appropriate conditions, certain coarse crystal grains By processing a metal material consisting of and accumulating plastic strain inside it and then heat-treating it at an appropriate temperature, the processed structure is recrystallized, applying the principle of obtaining homogeneous and fine crystals. The traces in the titanium ring welded area became inconspicuous by these structure adjusting means, and were generally improved to practically no problem.

However, some copper foils used in multilayer printed wiring boards, which are rapidly advancing and becoming more and more precise, have been reduced in thickness to 18 μm or less and low profile with small surface irregularities has been developed. There is a need for further homogenization of the properties, and correspondingly a further improvement for the improved traces of the titanium ring weld zone.

On the other hand, although the ring rolling method without a weld bead is currently used in some cases, it is necessary to sufficiently apply the plastic strain necessary for grain refinement of crystals due to the restriction of the rolling capacity of a ring rolling mill. Because of the difficulty, it is difficult to obtain a fine and uniform crystal structure required for the electrodeposited surface, and there are problems such as an increase in manufacturing cost. A hot rolling method is used to obtain a ring-shaped titanium intermediate product, and this intermediate product is cold-pressed again and continuously annealed to obtain a titanium electrodeposition drum. Although it has been used, it has not yet been widely used in Japan.

[0009]

As described above, the welding area of the titanium ring formed by welding has a macro- and micro-structure that is a coarse solidification transformed structure different from that of the base material as it is, resulting in corrosion wear. The properties are also different from those of the base material. Therefore, a post-treatment is required to make the transformed structure homogeneous with the base material. In principle, it is naturally possible to add processing such as squeezing, rolling and annealing corresponding to the processing history from the raw material of the base material to the product. However, since it is difficult to perform a process equivalent to the history of the base material in a limited region of the welding region, there is a need for what alternative means to perform it effectively.

JP-A-2-243790 and JP-A-4-62872 disclose:
The size of the crystal grains is adjusted by recrystallizing the weld and the transformed structure around it by the proposed rolling and annealing means. The trace of the weld transferred to the copper foil surface, which was once regarded as a problem Contribute to making it less noticeable. However, as described above, further improvements are required for titanium rings for producing highly precise thin, low-profile copper foil for printed wiring boards. That is, for example, welding is performed while cooling the outer surface to the inner concave portion formed by extruding the welded portion and the vicinity of the welded portion outward as in Japanese Patent Application Laid-Open No. 4-262872, and then warm or Even by adjusting means such as performing a crushing process in a cold state and subsequently performing an annealing process on the crushed portion, unevenness of a spotted pattern pointed out by strict inspection of the foil forming industry is scattered in the trace of the welded portion. Sometimes.

[0011] The unevenness of the structure is so small that it does not cause much problem in the production of copper foil for general use. The time-dependent change in surface roughness based on chemical and physical corrosion and wear due to the peeling of copper foil from the surface differs from that of the base material, and the spot pattern is projected on the copper foil to achieve the quality required for copper foil for precision printed wiring boards. Since it is rejected, it is necessary to cut and use a portion of the welding area of the copper foil, which causes a reduction in workability and an increase in cost. Accordingly, the present inventors worked to solve the problem of eliminating the spot pattern in the titanium ring welded area, which was improved by the proposed structure adjusting means, but was still present, and as a result, completed the present invention. Was.

[0012]

Means for Solving the Problems The present inventors have disclosed Japanese Patent Laid-Open No.
Note the uneven texture of the spot pattern that is slightly scattered on the polished surface of the weld area approximated to the base metal structure by the recrystallization means of overlaying, pressing, and heat treatment as described in 243790 and JP-A-4-62870. As a result of rigorously pursuing the cause, among the crystal grains that have been refined by the recrystallization means and the grain boundaries have been sharpened, grains that appear to be flakes of the pressed deformation structure when the coarse structure before the structure improvement is crushed are crushed. It was recognized that crystal groups with unclear boundaries were mixed, and it was judged that it was difficult to sufficiently spread the plastic strain required to reform the entire transformed structure by only one build-up, pressing, and heat treatment.

Based on this judgment, as a result of pursuing and experimenting on the means for improving the structure, the following three stages of heat treatment and re-
Through the crystallization process step, can be tissue unevenness of the weld zone is an object of the present invention is further reduced and becomes, grain size, abrasive, corrosion resistance was found that capable of further approximated by matrix .

First Step 1. A bending process is performed to protrude the welding area outside the ring around the welding line. 2. Press the bent part to restore the original arc. 3. The upper bent portion is recrystallized by heat treatment.

Second Step The bending and elongating and heat treatment recrystallization in the same manner as in the first step are repeated one or more times.

Third Step 1. As in the previous step, a bending process is performed to protrude the welding area to the outside of the ring. 2. At the boundary between the base material portion and the heat-affected zone on both sides of the concave portion of the bent portion, a build-up having a height of 15 to 20% of the base material thickness is performed, and then a build-up to fill the inner concave portion is formed. 3. The entire overlay is pressed so as to be equal to the thickness of the base material. 4. The processed portion is recrystallized by heat treatment. The structure of the weld zone after the above process is very similar to the structure of the base metal part, and is revived to a homogeneous and dense crystal structure with almost no unevenness of structure observed in the conventional method.

[0017]

The operation of each bending process in the first, second, and third steps performed after the above-described cylindrical winding and butt welding will be described.

Prior to the rolling and heat treatment, which is a basic means of modifying the solidification and transformation structure of the weld zone around the weld zone, the bending process in the first step involves localization of the structure that cannot be achieved by rolling alone. Acts to give the plastic strain of recrystallization. That is, the crystal group (lumps) in the metal structure is crushed by rolling and deforms into a flat shape, accumulating plastic strain at the grain boundaries,
Although recrystallization nuclei are generated during the heat treatment, it is impossible to make the recrystallization energy equally penetrate the entire structure only by increasing the rolling reduction. That is, it is considered that the above-mentioned uneven structure of the spot pattern is a residual reduction structure due to insufficient plastic strain. On the other hand, the form of plastic deformation in bending is different from rolling, but the tensile structure is applied to the structure outside the bending deformation and the compressive stress is applied to the structure inside the bending deformation. It provides plastic deformation involving slip and twinning, and acts to spread plastic strain to local areas that cannot be reached by rolling alone.

The function of the bending in the second step is exactly the same as in the first step. In the process of manufacturing a rolled titanium plate, the homogenization is enhanced by the repetition, just as the rolling annealing in several stages is repeated to obtain a product having a dense and homogeneous structure. However, the higher the number, the better. Needless to say, it is not economical, but it is not necessary to make the structure finer than the structure of the base material.

The effect of the bending in the third step is twofold. One of them is similar to the first and second steps, and acts as a repetitive effect. The other is to carry out the principle recrystallization action of rolling and heat treatment, and to finish and complete the target fine and fine grain structure. In the present invention, while the conventional method builds up a V-shaped groove in the base material of the welded portion or a groove-shaped recess formed by extruding the welded portion and the vicinity of the welded portion, the heat-affected zone and the base material are welded. The boundary with the material part is formed by pressing and receiving dies whose dimensions are located on both sides of the bending width, and the boundary is laid up with a height of 15 to 20% of the thickness of the base material, and then formed by this The filling that fills the recessed portion is performed.

In this manner, when the thickness of the entire built-up portion is made equal to the thickness of the base material by the subsequent crushing process, the rolling reduction becomes maximum when the welded portion is about 60%, and the reduction ratio with the base material portion is reduced. It is considered that the boundary is minimum at about 20%, during which the distance decreases in inverse proportion to the distance from the weld and is approximately proportional to the magnitude of the heat effect rate. As a result, a feature is created in which the grain size of the recrystallized grains at each position of the welded portion and the heat-affected zone is equalized. The above specific operation will be described in detail in the following examples.

[0022]

3 to 7 show an embodiment of the present invention. FIG. 3 shows the main steps in adjusting the structure of the welded portion of the titanium ring. V-bending, U-bending, R-bending, and the like can be applied to the bending, but the V-bending is exemplified here. FIG. 4-
FIG. 7 is a photomicrograph taken at 50 times magnification of the crystal structure of the polished surface near the weld in each step. The procedure will be described below.

A 6.5 mm thick titanium plate obtained by cold rolling a 12 mm thick hot rolled titanium plate is 500 mm in inner diameter and width by a roll forming machine.
The butt portion was continuously welded from one end to the other end by a plasma welding method while wrapping around a 300 mm cylinder to form a ring, and butt-shielding the opposite ends of the titanium plate with argon gas. FIG. 3A shows the vicinity of the welded portion of the titanium ring, and reference numeral 11 denotes a welded portion having a width of about 3 mm. Also,
The reference numeral 12 adjacent to the welded portion is a heat-affected zone where the crystal structure was transformed, and the width thereof was about 10 mm on each of the right and left sides. Reference numeral 13 on the outer side indicates a base material having the structure of the titanium material plate, and reference numeral 14 indicates a boundary between the base material and the heat affected zone.

FIG. 4 shows the thickness cut out from the above-mentioned titanium plate.
Using two plates of 6.5mm, 300mm width and 200mm length, the widths of both plates were butted together, and the surface of a test plate integrated by plasma welding under exactly the same conditions as above was polished, and then corroded by a corrosive liquid. Micrographs of the base metal, heat-affected zone, and weld at the 50-times magnification of the exposed surface, where (c) is the base metal, (a) is the heat-affected zone, and (b) is the weld. It is. The test plate was replaced with a real one because it could not be directly observed with a microscope from the above titanium ring, but since the processing conditions were completely matched with the real one, the results of the test plate were almost the same as those of the real one Make sure that As can be seen, the base material (c) is a uniform fine crystal with clear grain boundaries and irregularities which are the characteristic structure of the cold-rolled titanium sheet,
(b) is a solidification structure in which the base material is heated above the melting point (1688 ° C.), melts and then cools and solidifies, and remains unchanged from β crystal to α crystal, and β transformation point (882 ° C.) The heat-affected zone (a), which has a heated portion and a portion below 882 ° C but heated and grown, also has a coarse transformed structure that is completely different from the structure of the base material portion (c). It is recognized that.

Next, as shown in FIG. 3B, the range of the welding area centered on the welded portion was V-shaped so that the welded portion 11 protruded outward. This V-bending uses a die with a die width of 20 mm and an angle of 110 °, and a punch with a bead at the tip to prevent a spring bag. The boundary between the heat-affected zone and the base material after pressing is almost the die width The height of the projection 15 and the depth of the recess 16 were about 7 mm.

Next, the V-bent portion was pressed with a mold conforming to the curved surface of an arc having a thickness of 6.5 mm and an inner diameter of 500 mm, and was restored to the original cylinder arc.

Subsequently, the welding area was heated with a high-frequency induction heating device.
After the temperature was raised to 0 ° C. and maintained for 15 minutes, it was naturally cooled. The heating conditions were determined based on the heat treatment conditions taken after the cold-rolled titanium sheet of the base material was cold-worked.

The surface structure of the test plate after V bending and heat treatment under the same conditions as described above was observed under a microscope and photographed. FIG. 5A shows the heat-affected zone and FIG. 5B shows the weld zone. As is evident from the above, both of them are still far from the structure of the base material, but the coarse structure without any grain boundaries shown in FIGS. 4 (a) and 4 (b) splits into a crystal structure with irregularities. It is noted that it has changed.

Next, as a second step, the titanium ring welding area was V-bent and heat-treated under exactly the same conditions as in the first step.
The structures of the heat-affected zone and the welded portion after this repetitive processing can be known from the micrographs of the test plate subjected to the same processing, as shown in FIGS. 6 (a) (heat-affected zone) and (b) (welded zone). I can do it. The structures in both photographs clearly show that the recrystallized structure is closer to the base material than in FIGS. 5 (a) and 5 (b).

Next, the third step was performed as follows.
First, the V-bending of the welding area was performed in the same manner as in the first and second steps. As described above, one of the purposes is to apply plastic strain by bending, and the second purpose is to apply plastic strain by crushing and reducing. For the second purpose, at the position of the boundary 14 between the base material and the heat-affected zone at both ends of the width of the V-bend shown in FIG. (A) is TIG-welded to a size of 1.6 mm in height and 4 mm in width, and then, in the recess formed by this, reference numeral 18 in FIG.
(B) was subjected to TIG welding. Each welding was performed by cooling the outside of the titanium ring.

Next, the entire bent portion is pressed and molded to have a thickness substantially equal to the thickness of 6.5 mm of the base material portion 13, and the titanium ring is restored to a substantially perfect circle as shown in FIG. did. The rolling reduction ε important for the intended microstructural modification is generally expressed by the following equation from the thickness t ′ of the base metal and the thickness t ′ of the welded material subjected to fill welding.

[0032]

(Equation 1)

However, in the present invention, the boundary between the welded portion and the heat-affected zone and the base metal portion is approximately similar to the above equation. However, the middle portion is an inclined surface, and therefore differs depending on the position. The rolling reduction of each position within the range of the value and the minimum value at the end of the heat-affected zone decreases in inverse proportion to the distance from the base material portion. By the way, the base material is about 60%, the end of the heat affected zone is about 20%,
In the meantime, the heat affected zone was given a plastic strain with a rolling reduction of 20 to 60%.

After that, the above-mentioned processed portion was heated to 590 ° C., kept for 15 minutes and allowed to cool. V bending under the same conditions as above,
After the surfaces of the welded portion and the heat-affected zone of the test plate subjected to overlay welding, rolling, and heat treatment were polished, they were observed under a microscope. In each microstructure, fine grains with clear grain boundaries are uniformly arranged,
It was found that the microstructure was very similar to the microstructure of the base metal. FIG. 7 is a micrograph of the heat-affected zone, and FIG. 7 (b) is a welded zone. By comparing this with the micrograph of the base material in FIG. You can see that it is.

The Hv value obtained by measuring the hardness of the modified portion using a Vickers hardness tester was as follows.
It was confirmed that the hardness was very similar between the welded portions 120 to 130 and the heat affected zones 109 to 117.

The actual titanium ring after the heat treatment is
After this, it is shrink-fitted to the inner drum, which is the base of the electrodeposition drum, and after its surface layer is machined by about 0.5 mm, it is polished and finished to a surface roughness (Ra) of about 0.25 μm. The welded joint was carefully inspected. As a result, the pattern of the welding trace clearly distinguished by the conventional method was extremely difficult to see, and the unevenness of the structure scattered by the conventional method was hardly recognized.

[0037]

As described above, the titanium ring for an electrodeposition drum manufactured by using the hot or cold-rolled titanium plate of the present invention as a material provides a weld formed by rolling a titanium plate and welding a butt portion. The solidification and transformation structure of the heat affected zone and the heat-affected zone can be regenerated almost equally to the structure of the homogeneous and dense base material, and the structure can be made uniform and fine to the extent that there is almost no unevenness found in the conventional structure improvement treatment method. As a result, high-quality copper foil required for thin, low-profile copper foil can be manufactured with high yield, and an overall excellent economic effect can be brought about.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an apparatus for manufacturing an electrolytic copper foil.

FIG. 2 is a partially cutaway front view showing a structure of an electrodeposition drum and a mounting position of a titanium ring constituting the same.

FIG. 3 is a partial cross-sectional view showing a main process of improving the structure of a titanium plate weld and a heat-affected zone in the production of a titanium ring according to the present invention.

FIG. 4 is a micrograph of the structure of a cold-rolled titanium plate as a base material of a conventional titanium ring, where (a) is a heat-affected zone, (b) is a welded portion, and (c) is a base material portion. .

5A and 5B are photomicrographs of the structure of the welded portion and the structure of the heat-affected zone at the stage where the first step in the structure improving process of the present invention has been completed.

FIGS. 6A and 6B are micrographs of the structure of the welded portion and the structure of the heat-affected zone at the stage when the second step in the structure improving process of the present invention is completed.

7A and 7B are photomicrographs of the structure of the welded portion and the structure of the heat-affected zone at the stage where the third step in the structure improvement treatment of the present invention has been completed and completed.

[Explanation of symbols]

 10 Titanium ring 11 Welded part 12 Heat affected part 13 Base material part 14 Boundary part 15 Bend convex part 16 Bend concave part 17 Overlay part A 18 Overlay part B

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-262872 (JP, A) JP-A-4-36488 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22F 1/18 C25D 1/04 C25D 17/10

Claims (1)

(57) [Claims] 1. A method for manufacturing a titanium ring serving as a cathode of an electrodeposition drum for producing an electrolytic metal foil, comprising: a welded portion for butt-welding opposite ends of a pure titanium plate wound in a cylindrical shape; In the means for adjusting the resulting solidification and transformation structure to a structure of the same quality as the base material, after bending the welding area to the outside of the ring around the welding line, press the bent part to restore the original arc Heat - treated recrystallized bent and stretched part
A first step of reduction, the bending, restore, heat treatment recrystallization
A second step of repeating further one or more times of, suitable to thickness by rolling after NikuSakari the recess formed by the bending process
A third step of sequentially performing heat treatment and recrystallization .