JP2002155349A - Method for producing titanium plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a titanium plate which has a smooth surface hardly causing uneven grinding and is suitable to, particularly, a blank for electrodeposited drum. SOLUTION: In a forging process for steel ingot, after applying a compressing work having >=10% in α-phase temperature zone, the material is heated in β-phase temperature zone and successively, cooled in the condition satisfying inequality of R/t>=0.01, wherein, R is the average cooling speed ( deg.C/sec) in the period of time from the β transforming point to 800 deg.C and t is the thickness (mm) of the titanium blank when the cooling is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a titanium plate requiring excellent surface properties (smoothness), in particular, to the surface of a drum used for producing metal foil such as copper foil and nickel foil by an electrolytic deposition method. The present invention relates to a method for producing a titanium plate having excellent surface properties (smoothness).

[0002]

2. Description of the Related Art A metal foil such as a copper foil and a nickel foil used for electronic equipment is formed on a drum (hereinafter referred to as an electrodeposition drum) for rotating a metal such as copper or nickel from a solution such as copper sulfate or nickel sulfate. To produce a foil, which is continuously wound and collected.

[0003] Since this electrodeposition drum needs to have good corrosion resistance, a plate-shaped titanium material wound around a steel drum base material (inner drum) is used. That is, the electrodeposition drum is formed by bending a plate-shaped titanium material (titanium plate) into a cylindrical shape, joining the ends by welding to form a ring, and fitting this into the inner drum by shrink fitting or the like. It is manufactured by

[0004] On the other hand, with the miniaturization and high density of electronic devices and the like, there is an increasing demand for metal foils having a smooth surface. Since the surface condition of the metal foil is determined by the surface condition of the titanium plate used for the surface of the electrodeposition drum, after assembling the electrodeposition drum, its surface, that is, the surface of the titanium plate is finished by grinding and polishing, In the polishing step, as described below, polishing unevenness presumed to be caused by the non-uniformity of the structure of the titanium material occurs, and therefore, there is a problem that the surface quality of the metal foil becomes poor.

[0005] In the titanium plate manufacturing process, the ingot manufactured in a consumable arc melting furnace or an electron beam melting furnace is subjected to hot rough forging and heat treatment for heating in a β phase temperature range. Thereafter, rolling is performed while repeating reheating until the final sheet thickness is reached. In this step, when heated in the β-phase temperature range after the rough forging, the crystal grains are coarsened. In particular, titanium has a faster growth rate of crystal grains in the β phase temperature range than in the α phase temperature range, and it is possible to randomize the orientation of the crystal grains by heat treatment in the β phase temperature range. It becomes coarse.

In the rolling process after the heat treatment in the β phase temperature range,
The crystal grains generated by this heat treatment are recrystallized. At this time, the effect of the crystal grains after the heat treatment in the β phase temperature region remains in the titanium material after rolling, and the region of the recrystallized grains having substantially the same crystal orientation is proportional to the size of the crystal grains after the heat treatment. Will exist. In the region of the recrystallized grains, the crystal orientation is slightly different in each region. That is, the surface roughness of the polished surface differs for each region, and polishing unevenness occurs.

[0007] In particular, on the inner side of the ingot (particularly at the center), the influence of processing is reduced, so that coarse crystal grains existing at the time of the ingot remain. Therefore, when the surface (that is, the surface of the titanium plate) is repeatedly polished with the use of the electrodeposition drum and a portion corresponding to the center of the ingot appears on the surface, polishing unevenness is likely to occur.

[0008] Further, the crystal structure of titanium is a dense hexagonal structure (hcp), but since it does not have a slip component in the c-axis direction of the hcp structure, it is difficult to deform in this direction. As a result, if the orientation of the c-axis is disturbed for each crystal, the surface hardness becomes non-uniform, the resistance applied to the grindstone during polishing slightly changes, a good polished surface cannot be obtained, and polishing unevenness occurs. Invite.

In order to solve the problem of uneven polishing, the present applicant disclosed in Japanese Unexamined Patent Application Publication No. 9-20971 a method for destroying coarse crystal grains inherent in a titanium ingot to reduce the structure unevenness. 1000 ° C during hot working to eliminate
/ H is passed through the β transformation point at a cooling rate of
A method of processing and heat-treating in the temperature range below the transformation point was proposed. Further, in Japanese Patent Application Laid-Open No. 9-20990, the Vickers hardness on the surface (load 9.8) is obtained by repeating the processing in the temperature range below the β transformation point after giving the above-mentioned heat history.
(07N or less) is disclosed.

However, in the methods described in these publications, coarse crystal grains can be destroyed. However, in order to obtain a titanium plate having excellent surface properties required for the production of metal foil, which has been required in recent years, the above-mentioned heat treatment is required. Processing conditions must be sufficiently controlled, and it is not possible to obtain a homogeneous structure up to the inside.Therefore, especially when used as an electrodeposition drum, the surface of the titanium material is repeatedly polished to reduce the center of the titanium material. When it appears on the surface, uneven polishing occurs due to unevenness on the structure.

In Japanese Patent Application Laid-Open No. 6-93400,
The titanium material is hot-roll-rolled, cold-worked at a working rate of 20 to 70% to this ring-shaped titanium material, and further processed under specific conditions, that is, a total working rate of 35% under cold rolling. In the case of ~ 70%, 570≤T≤6
70, 5 ≦ t ≦ 120, −T + 610 ≦ t ≦ −T + 72
0, when the processing rate is also 20% or more and less than 35%,
Annealing under conditions satisfying 600 ≦ T ≦ 670 and 30 ≦ t ≦ −T + 720 (T is annealing temperature, t is annealing time) generates fine crystal grains, and is caused by a large step between crystal grains adjacent to each other. There has been proposed a method for eliminating a step on a drum surface and improving the quality of a metal foil.

However, this method can eliminate the surface defects caused by the steps in the adjacent crystal grains, but it involves the heating and processing steps to obtain a ring-shaped titanium material. No mention is made of the coarsening of the crystal grains and the improvement of the difference in crystal orientation for each recrystallization region, and the problem of uneven polishing caused by this difference in crystal orientation cannot be solved.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a titanium plate having a smooth surface which is unlikely to cause such polishing unevenness, particularly a titanium plate used as a material for an electrodeposition drum. It is in.

[0014]

The gist of the present invention resides in the following method for producing a titanium plate.

In the forging process of the ingot, a compression process of 10% or more is applied in the direction perpendicular to the surface of the titanium plate in the α-phase temperature range, and then the titanium plate is heated in the β-phase temperature range. 1) A method for producing a titanium plate that is cooled under conditions satisfying the expression. R / t ≧ 0.01 (1) where, R: average cooling rate from the β transformation point to 800 ° C. (° C.)
/ Sec) t: Thickness (mm) of the titanium material at the time of cooling.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for manufacturing a titanium plate according to the present invention will be described in detail.

In order to produce a titanium plate without polishing unevenness, it is necessary that crystal grains are fine at the stage after completion of the heat treatment in the β-phase temperature range and uniform inside (in the thickness direction center). is necessary.

For that purpose, as described above, in the forging process of the ingot, it is necessary to apply a compression process of 10% or more in the α-phase temperature range to give a pre-strain to the ingot, and thereafter, to perform the β-phase temperature range. Heat with. That is, in the final forging stage before heating in the β phase temperature range, the inside of the ingot (center part) in the α phase temperature range
Strain is accumulated in the titanium material by applying compression processing until the recrystallization proceeds to the inside of the material when heated in the β phase temperature region in the next step using this strain as a driving force, making the crystal grains fine and internal Can be made uniform.

The temperature during forging before heating in the β phase temperature range (the surface temperature of the forged material) must be in the α phase temperature range, and is preferably 850 ° C. or less. If the temperature is in the β phase temperature range, the crystal grains become coarse again after forging.

If the compression processing is less than 10%, the driving force for recrystallization inside the raw material is insufficient, and it is impossible to uniformly recrystallize up to the center of the ingot.
The compression processing of 10% or more is processing in which compression of 10% or more is applied in a direction perpendicular to a surface to be a surface of a titanium plate to be manufactured, that is, processing in which a draft is 10% or more. . The compression processing is more preferably at least 20%.

After completion of forging, heating is performed in the β phase temperature range. Because the compression process is applied in the forging process as described above, in the heating process in the β phase temperature range, the material is uniformly recrystallized to the inside of the material,
The crystal grains can be made fine and uniform up to the center.

Next, cooling is performed under the condition satisfying the following equation (1). In the equation (1), R is 800 from the β transformation point.
The average cooling rate up to ° C. (° C./sec), and t is the thickness (mm) of the titanium material at the time of cooling. R / t ≧ 0.01 (1) If the average cooling rate deviates from the condition of equation (1), the cooling effect at the center of the titanium material becomes insufficient, and the crystal grains at the center of the material become coarse. . As a result, the polishing property of the central portion of the titanium plate is deteriorated, and when the polishing of the surface of the electrodeposition drum is repeated to expose the central portion of the titanium plate on the surface, polishing unevenness occurs. There is no particular upper limit for the average cooling rate.

As described above, a feature of the method for producing a titanium plate of the present invention is that a predetermined amount of compression processing is performed on an ingot in an α-phase temperature range before heating in a β-phase temperature range, and then in a β-phase temperature range. Heating,
After that, there is an optimal combination of the three steps of cooling at the above-mentioned predetermined cooling rate, and by this method, the crystal grains are fine, and even to the center in the thickness direction, having a smooth surface that is unlikely to cause polishing unevenness. A titanium plate can be manufactured.

After cooling, rolling and heat treatment may be performed by a usual method to form a titanium plate having a predetermined thickness.

[0025]

EXAMPLE A pure titanium ingot (diameter 300 mm) was forged to a thickness of 150 mm at a heating temperature of 1100 ° C.
It was reheated at 50 ° C. and further processed to the intermediate thickness shown in Table 1.

Next, at the time when the material was cooled to the temperature (forging temperature) shown in Table 1, the intermediate thickness was reduced to 100 mm.
Finish forging was performed. This step is the “step of applying a compression process of 10% or more in the α-phase temperature range” in the method of the present invention, and the rolling reduction at this time is as shown in Table 1.
Each of the compression processes was performed in a direction perpendicular to the surface to be the surface of the titanium plate. No. 1 and No. 2 in Table 1 are comparative examples in which the rolling reduction was out of the conditions specified by the method of the present invention.

[0027]

[Table 1] By the above forging process, the board width 200mm x thickness 100m
m of titanium material was obtained.

Subsequently, the titanium material after the forging was heated at 950 ° C. which is a β phase temperature range for 2 hours. This step is the “step of heating in the β-phase temperature range” in the method of the present invention. The β transformation point of this pure titanium is 910 ° C.

Subsequently, cooling was performed under cooling conditions shown in Table 1. This step corresponds to “R / t ≧ 0.
No. 7 is a comparative example in which this condition is not satisfied.

Thereafter, the cooled material was heated to 850 ° C., rolled to a thickness of 10 mm, and heat-treated at 700 ° C. for 1 hour to obtain a titanium plate specified by JIS-H4600.

5 cm from this titanium plate (10 mm thick)
Cut out a square test piece, 1mm or 5m deep from the surface
m, and the cut surface was polished with a # 1200 abrasive paper, and then finished by buffing.

The surface of the polished test piece was observed with a microscope of 20 times, and the occurrence of uneven polishing was investigated.

The results of the investigation are shown in Table 1. "Surface" in the column of "Abrasiveness" in Table 1 is a test piece cut from the surface to a depth of 1 mm, and "center" is a depth of 5 mm from the surface.
This is a test piece cut to the nearest mm. In the column of “Polishability”, a mark “な か っ” indicates that polishing unevenness did not occur, a mark “△” indicates that polishing unevenness was slightly observed, and a mark “X” indicates that polishing unevenness occurred. In the column of “Comprehensive evaluation”, “Surface part”
And the lower one of the evaluations for the “center” was described. If the “overall evaluation” was “O” or “△”, the evaluation was “good”.

As is clear from these results, good results were obtained with the titanium plates Nos. 3 to 6 satisfying the conditions specified in the present invention. In particular, compression processing of 20% or more in the α-phase temperature region was performed. No. (that is, the rolling reduction was 20% or more)
In the titanium plates of Nos. 4 to 6, no polishing unevenness was observed at the "center".

[0035]

According to the method of the present invention, it is possible to produce a titanium plate excellent in surface properties which is less likely to cause polishing unevenness and is suitable as a material for an electrodeposition drum. This makes it possible to produce a metal foil having a smooth surface. Since this titanium plate has a uniform structure up to the center in the plate thickness direction, polishing unevenness does not occur even if polishing is repeated, and expensive titanium can be used without waste (in a good yield). In addition, this makes it possible to extend the life of the electrodeposition drum, which can contribute to a reduction in the manufacturing cost of the metal foil.

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Claims (1)

[Claims] In a forging process of an ingot, after performing compression processing of 10% or more in a direction perpendicular to a surface to be a surface of a titanium plate in an α phase temperature range, heating is performed in a β phase temperature range, A method for producing a titanium plate, comprising cooling under conditions satisfying the following expression (1). R / t ≧ 0.01 (1) where, R: average cooling rate from the β transformation point to 800 ° C. (° C.)
/ Sec) t: Thickness (mm) of the titanium material at the time of cooling.