JP3354548B2 - Rolling method of stainless steel foil and stainless steel foil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spring for a tact switch (hereinafter referred to as a dome contact piece), a method for rolling stainless steel foil used for a suspension of a hard disk drive, and the like, and a stainless steel foil.

[0002]

2. Description of the Related Art In OA equipment, AV equipment, portable electronic equipment, and the like, there is a demand for a longer life of a dome contact piece used in such equipment in order to be smaller and thinner.
In addition, a suspension spring, a gimbal spring for supporting a magnetic head of a hard disk device, and a head for a printer ink jet are also required to be reduced in size and thickness. Metal foils obtained by cold rolling austenitic stainless steel (SUS301, 304, etc.) are used for these dome contact pieces, suspension springs, gimbal springs, and inkjet heads. The reason for this is that austenitic stainless steel SUS30
1, 304 is because the austenite phase is transformed into a martensite phase and hardened by working transformation by cold rolling, so that it can be used as a high-quality spring material having high strength and hardness.

Conventionally, various techniques for rolling austenitic stainless steel as a spring material have been proposed. For example, Japanese Patent Application Laid-Open No. 6-279952 discloses that, in order to provide a high-strength stainless spring steel having excellent workability as a seat belt spring for an automobile, cold rolling at a reduction of 20 to 70% after solution heat treatment is performed. A high-strength stainless steel for springs comprising two phases of an austenite phase and a martensite phase and having a Vickers hardness adjusted to 400 to 580 is disclosed. Further, the publication discloses a high-strength spring stainless steel in which Vickers hardness is adjusted to 600 or more by performing aging heat treatment. Japanese Patent Application Laid-Open No. Hei 7-216450 discloses a method of manufacturing an austenitic stainless steel material having a high hardness and a high strength and excellent spring properties by using austenitic stainless steel material with a reduction ratio of 20% or more. A method is disclosed in which a desired thickness is obtained while being hardened by rolling and then adjusted to a desired hardness while being softened by a heat treatment at 650 to 900 ° C. Japanese Patent Application Laid-Open No. Hei 9-192712 discloses a method for producing an austenitic stainless steel sheet having a target thickness and hardness by rolling, with the aim of providing the rolling temperature, rolling reduction and hardness of the austenitic stainless steel to be rolled. The number of rolling passes, target rolling temperatures, rolling reduction, and hardness after each rolling pass are determined based on the correlation so that the target thickness and hardness are obtained in the final pass. And a method of rolling.

Japanese Patent Application Laid-Open No. Hei 10-263621 discloses an austenitic stainless steel cold-rolled steel strip, which is annealed at 50 to 200 ° C., for the purpose of providing a method of manufacturing a stainless steel cold-rolled steel strip having good gloss. A method of manufacturing a cold-rolled steel strip which is heated and rolled in one pass at a rolling speed of 300 m / min or less and a rolling reduction of 22% or more by a rolling mill having a work roll diameter of 250 mm or less is disclosed. JP-A-8-1655
In order to provide a method for producing an austenitic stainless steel foil for a spring having a small warp after one-sided etching, Japanese Patent No. 19 discloses a cold-rolled austenitic stainless steel sheet having a thickness of 0.04 to 0.30 mm and a nitrogen concentration of 0.04 to 0.30 mm. 10 Vo
A manufacturing method is disclosed in which bright annealing is performed in a non-oxidizing gas atmosphere of 1% or less, followed by temper rolling at a reduction of 35% or more. Further, JP-A-62-199214 discloses that
For the purpose of rolling a steel strip made of austenitic stainless steel to a target hardness, the correlation between the amount of work-induced martensite and the rolling reduction corresponding to the previously determined target hardness is used as a control target pattern. A method of controlling a rolling speed and a rolling reduction in a rolling pass as operating factors is disclosed.

In recent years, as described above, the demand for miniaturization of OA equipment and the like has become stronger, and the thickness of a stainless steel spring material used for these equipment has been required to be 30 μm or less and the Vickers hardness has to be 400 or more. I have. Further, conventionally, the width of the rolled metal foil is about 300 mm, but if the width is rolled as wide as possible, the production efficiency is high and the effect of cost reduction is great. For this purpose, 12 steps or 20 steps
Using a multi-stage rolling mill as wide as possible, e.g.
It is required to perform rolling with a width of 550 mm. When performing wide rolling, the flatness of the rolled metal foil affects the quality of the final product. For example, when manufacturing a suspension spring, this metal foil is subjected to an etching process. If the flatness of the rolled metal foil is low, warpage occurs when the etching process or the like is performed.

[0006]

The above-mentioned prior art does not disclose rolling a stainless steel foil to an extremely thin thickness of 30 μm or less. In order to obtain a stainless steel foil having a thickness of 30 μm or less, a high flatness and a high hardness by cold rolling from an austenitic stainless steel material coil, the above-mentioned conventional technique cannot be applied unconditionally. An object of the present invention is to provide a stainless steel foil for a spring having a thickness of 30 μm or less, a high flatness, and a high hardness by cold rolling from a material of austenitic stainless steel foil. The present inventor, using a reversible multi-high rolling mill, from austenitic stainless steel foil material coil, to produce a stainless steel foil having a high flatness and a high hardness with a thickness of 30 μm or less, a total of It has been found that the rolling reduction, the rolling temperature, and the rolling reduction in each rolling pass are the most significant factors. Furthermore, the present inventor has set the flatness of the finally rolled stainless steel foil to a predetermined value, so that even if an etching process or the like is performed as a suspension spring material or the like, a high-quality stainless steel having a warpage within a target range. They found that foil could be obtained.

[0007]

According to the present invention, a stainless steel foil having a thickness of 30 μm or less is obtained by a reversible multi-high rolling mill .
In the rolling method because the material of the stainless steel foil was rolled by a plurality of rolling passes, each rolling reduction of the plurality of rolling passes 2
0% or less and before the total reduction exceeds 60%
The rolling pass heats the stainless steel foil to a temperature of 50 to 80 ° C.
This is a method for rolling stainless steel foil, characterized by rolling at a degree . Also, the present invention provides a reversible multi-high
Is 30μm or less, width is rolled to 310-550mm
Stainless steel foil, the rolling direction of the stainless steel foil
The width of the rolling direction is 300 ~
When a piece of steel foil cut to 500 mm is left on a platen,
The height from the platen surface to the steel foil piece is 1.5 mm or less
Bottom stainless steel with Vickers hardness of 400 or more
It is a steel foil. Further, in the present invention, the steel foil piece is placed on a platen.
When placed, more preferably, the center of the steel foil piece
Height A to the vicinity of the part is 0.2 mm or less, and
From the end of the steel foil piece in the rolling direction to the vicinity of the end is 1.5 m
m or less.

In the present invention, the material coil of the austenitic stainless steel foil before rolling has a thickness of 40 to 40 mm.
The thing of 80 μm is used. When rolling to a thickness of 30 μm or less through multiple passes of rolling by a reversible multi-high rolling mill, the rolling reduction of each rolling pass is rolled at a rolling reduction of 20% or less, and the total rolling reduction of the multiple passes is reduced. Is more than 60%, the stainless steel foil to be rolled
When the rolling is performed at a temperature of 80 ° C., the austenite phase can be transformed into a martensite phase more, and a stainless steel foil having a thickness of 30 μm or less and a Vickers hardness of 400 or more can be obtained. Furthermore, when the rolling is performed with the rolling reduction of each rolling pass being 20% or less as described above, not only the work hardening due to the rolling is further improved, but also the rolling heat generated during the rolling can be suppressed to a low level. If the temperature control is properly performed, the control of the rolling temperature of the material to be rolled can be easily performed.

The present invention further provides a stainless steel foil rolled in the final finishing rolling pass having a thickness of 30 μm or less and a width of 31 μm.
Rolled to 0 to 550 mm, the stainless steel foil was removed at both ends in the rolling direction by a predetermined width, and the length in the rolling direction was 3 mm.
Foil pieces cut to a size of 00 to 500 mm (length and width: 30
0 to 500 mm) on a surface plate, the vertical height from the surface of the surface plate to the foil piece is 1.5 mm or less, preferably the vertical height A from the surface of the surface plate to the vicinity of the center of the foil piece. Is 0.2 mm or less, and the stainless steel foil rolled so that the vertical height B from the surface of the platen to the vicinity of the end in the rolling direction is 1.5 mm or less. Stress). For this reason,
Only by performing heat treatment for removing ordinary residual stress on the stainless steel foil after the final finish rolling is completed, the amount of warpage at the time of performing the etching treatment or the like can be within the target range.

[0010]

(Embodiment) FIG. 1 shows an outline of a reversible 20-high rolling mill for carrying out the present invention. FIG.
In the rolling mill shown in FIG.
Is provided with a pair of tension reels 2 for winding and rewinding. A work roll 3, a first intermediate roll 4a, a second intermediate roll 4b, and a backup roll 5 are provided between the left and right tension reels 2. Although not shown, a nozzle for injecting rolling oil is installed near the intermediate rolls 4a and 4b.

A pair of upper and lower squeezing rollers 6 are provided between the work roll 3 and the tension reel 2 with the stainless steel foil 1 interposed therebetween. The squeezing roller 6 is a roller for reducing the rolling oil adhering to the surface of the rolled stainless steel foil 1 to a constant film thickness. The gap between the upper and lower squeezing rollers 6 can be adjusted by a cylinder device (not shown). ing. Squeezing roller 6
A pair of upper and lower wiper devices 8 composed of rollers made of synthetic rubber or the like is installed on the downstream side. A deflector roll 9 is provided on the downstream side of the wiper device 8 so that a predetermined tension is applied to the stainless steel foil 1 so that the stainless steel foil 1 can be normally unwound and wound during rolling. Further, the rolling direction is reversed for each of a plurality of rolling passes.

Next, the method for rolling stainless steel foil of the present invention will be described. Table 1 shows that using the 20-high rolling mill shown in FIG.
m coil (steel strip) with a thickness of 15
An example of a process for rolling (total draft 95.0%) on a stainless steel foil of μm is shown. In Table 1, the process targeted by the present invention is a rolling process, that is, a final finish rolling process. Note that the rolling and rolling processes include a softening annealing process after any one of the rolling passes or after all rolling passes of the process. This softening annealing is a heat treatment performed to soften the material of the stainless steel foil and increase the rolling workability. It is not necessary to provide the above-mentioned soft annealing step between a plurality of rolling passes constituting the rolling step.

[0013]

[Table 1]

In the example shown in Table 1, a total of seven rolling passes are set in the rolling process which is the subject of the present invention. Table 2 shows an example of specifications of each rolling pass in the rolling process (target rolling thickness of each rolling pass, rolling reduction of each rolling pass, total rolling reduction, rolling temperature). As shown in Table 2, in rolling passes 5, 6, and 7 in which the total draft is 60% or more, the temperature of the stainless steel foil to be rolled is set in the range of 50 to 80 ° C., and the rolling is performed. The temperature of the stainless steel foil to be rolled can be in the range of 50 to 80 ° C. by appropriate temperature control of the rolling oil. The reason for this is that the thickness is 40 to
Rolling ultra-thin stainless steel foil of 30 μm or less from 80 μm material coil, and reducing the rolling reduction of each rolling pass by 2
This is because the rolling temperature of the stainless steel foil can be appropriately controlled if the temperature of the rolling oil is accurately controlled because the rolling heat is reduced by as small as 0% or less. In Tables 1 and 2, a rolling path for rolling a 45 μm-thick stainless steel foil to a thickness of 15 μm in a rolling process is shown. For example, a material coil of a 45 μm-thick stainless steel foil is When rolling is performed to a range of 20 to 30 μm, the total number of rolling passes 7 shown in Table 2 is reduced to 4 to 6, and the rolling reduction of each rolling pass is set to 20% or less.

[0015]

[Table 2]

In the rolling process which is the subject of the present invention, in the rolling pass in which the total rolling reduction is less than 60% from the first rolling pass, the austenite phase is not completely transformed into the martensite phase and the two phases are mixed. It can be inferred that it is an organization. In the present invention, when rolling is performed at a rolling temperature of 50 to 80 ° C. in a rolling pass in which the total draft exceeds 60%, the phase in which these two phases are mixed is transformed into more martensite phase, and the Vickers hardness is increased. Can be further improved. Further, when rolling is performed with the rolling reduction of each rolling pass being 20% or less, the generation of rolling heat can be suppressed low, and the control of the rolling temperature becomes easy. For this reason, the thickness 30 where the flatness is high and the Vickers hardness is 400 or more without softening annealing between each rolling pass.
It is possible to obtain a stainless steel foil of μm or less.

[0017]

(Example 1) Using a 20-high rolling mill shown in FIG.
When rolled to 5 μm, the flatness of the rolled stainless steel foil was measured. Regarding the flatness, first, both ends in the rolling direction L of the stainless steel foil rolled to a width of 550 mm in the final finish rolling pass were removed by slitting each about 25 mm,
A stainless steel foil piece (length and width 500 × 500 mm) was cut so that the length in the rolling direction L was 500 mm. Subsequently, the surface plate 10 of the three-dimensional measuring device shown in FIG.
The stainless steel foil piece 1a was allowed to stand still (with no tension applied) thereon, and the distribution of the vertical height from the surface of the surface plate 10 to the stainless steel foil piece 1a was measured with a laser measuring instrument. FIG. 6 shows an example in which the measurement results are displayed as a contour map.
Then, from the height distribution values measured above, FIG.
As shown in (b), the maximum value A of the height distribution near the center of the stainless steel foil piece 1a and the maximum value B of the height distribution near both ends of the slit were obtained. Table 3 shows the measurement results.
The reason why both ends of the rolled stainless steel foil in the rolling direction L are slit and removed by a predetermined width is that, due to the structure of each roll of the multi-stage rolling mill, the vicinity of both ends in the rolling direction L of the rolled material is flat. This is because the degree becomes low. Therefore, the width to be removed by slitting both ends is an appropriate value in consideration of the width of the rolled material obtained in the final rolling pass (the width of one side (one end) to be removed is about 5% of the rolling width. Degree). The vicinity of the center of the stainless steel foil piece 1a is defined as the width H from the end in the rolling direction L in the contour diagram shown in FIG.
The central portion H2 excluding 1 is shown. When the rolling width of the stainless steel foil is 310 to 550 mm,
It may be about 25 to 75 mm.

As is apparent from Table 3, when a rolling pass whose rolling reduction exceeds 20% is set in each rolling pass, the height A near the central portion showing flatness is 0.2 mm,
Alternatively, the height B near the end was more than 1.5 mm.
The reason why the flatness is reduced in this manner is that when the rolling reduction per pass is set to a large value of 20% or more, residual stress is generated in the rolled stainless steel foil. It is presumed that when the stainless steel foil piece 1a is cut in this state and left on the surface plate 10, the residual stress becomes apparent and appears as a slight height difference. The rolling conditions at the time of this measurement are as follows. Rolled material: SUS304 Rolling machine: Work roll diameter 30 mm and 60 mm are used separately for each pass Work roll length 750 mm Rolling speed 120 m / sec Rolling load 110 tons

[0019]

[Table 3]

Example 2 Using a 20-high rolling mill shown in FIG. 1, a material of austenitic stainless steel foil (SUS304) having a thickness of 45 μm was cut to a thickness of 15 μm and a width of 550 m.
m, the relationship between the rolling temperature, the total draft and the Vickers hardness of the rolled stainless steel foil was measured. At this time, the total number of rolling passes was 7, and the rolling reduction of each rolling pass was 20% or less. FIG. 2 shows an example of the measurement results, and is a graph showing the relationship between the total draft and the Vickers hardness of the rolled stainless steel foil when the rolling temperature of the stainless steel foil is changed. Note that the rolling conditions at the time of this measurement are almost the same as those in the first embodiment. As shown in FIG. 2, when the rolling temperature is 50 to 80 ° C. in a rolling pass in which the total draft is 50% or more, the Vickers hardness becomes 350 or more, and the total draft exceeds 60%. When the rolling temperature was set to 50 to 80 ° C. in the rolling pass, a stainless steel foil having a Vickers hardness of 400 or more was obtained.

When the stainless steel foil obtained by the present invention is used as a dome contact piece, a suspension spring for a hard disk drive, or the like, it is formed into a minute predetermined shape by press punching or etching. However, if the flatness of the stainless steel foil is low or if the stainless steel foil has residual stress due to rolling, warping occurs after the press punching or etching treatment, resulting in a defective product. To prevent this problem, a tension annealing treatment for removing residual stress has been conventionally performed after the final finish rolling. In the present invention,
As described above, the numerical value indicating the flatness of the finished stainless steel foil, that is, when a piece of stainless steel foil cut to a predetermined size is allowed to stand on the surface plate, the stainless steel foil from the surface of the surface plate If the vertical height up to 1.5 mm or less, especially the vertical height A near the center is 0.2 mm or less, and the vertical height B near the end in the rolling direction is 1.5 mm or less, the flatness is high. Thus, a stainless steel foil having a small amount of warpage after press punching or etching can be obtained.

(Example 3) Test numbers 3 (flatness A: 0.31 mm, B: 2.10 mm) and test number 4 (flatness A: 0.18 mm, B: 1.50 mm) shown in Table 3 were used. For the 15 μm thick stainless steel foil after rolling shown,
After performing the heat treatment to remove the residual stress, length 15mm,
A test piece for etching treatment having a width of 10 mm was prepared and subjected to etching treatment. This test piece produced a test piece corresponding to each position in the rolling width direction. Then, the warpage S after the etching process was measured by the method shown in FIG. In the method of measuring the amount of warpage, one end of the test piece 1c was fixed, and the amount S of warpage was measured at a position 10 mm away from the fixed portion by a linear distance. In this measurement, the target value of the warpage S after the etching treatment was set to within ± 50 μm per 10 mm. FIG. 4 shows this measurement result (the warpage amount S is shown as an absolute value), and shows the relationship between the position in the rolling width direction of the test piece 1C and the warpage amount S. As is clear from FIG. 4, the height A near the center when the final finish rolling is completed is 0.2 mm.
Hereinafter, when the height B in the vicinity of the end portion is 1.5 mm or less, the warpage S due to the etching process could be kept within the target ± 50 μm. Even if the shape control of the multi-high rolling mill is optimally performed, when the final finish rolling is completed, the value indicating the flatness of the rolled stainless steel foil, that is, the height B near the end in the rolling direction is inevitably at the center. A near the part
Be larger. However, in the present invention, even when a rolling width of 310 mm or more, particularly 400 mm to 550 mm is wide, the height B near the end of the foil piece removed by a predetermined width in the rolling direction is 1.5 mm. If you do
By performing the heat treatment for removing the residual stress, it is possible to obtain a stainless steel foil having a small warpage and a thickness of 30 μm or less even when the etching treatment is performed.

In the above embodiment of the present invention, SUS304 has been described as the material of the stainless steel foil.
The present invention relates to SUS3, an austenitic stainless steel.
01, SUS316 and the like. Further, although the stainless steel foil of the present invention is described as being rolled by using a 20-high rolling mill, it has been described that the stainless steel foil of the present invention has a 12-roll rolling mill.
Rolling can be performed using a multi-high rolling mill such as a high rolling mill. The thickness of the stainless steel foil obtained by the present invention can be up to about 6 to 7 μm.

[0024]

The present invention described above has the following effects. 1) Since a stainless steel foil having a thickness of 30 μm or less, a wide flatness, a high flatness and a high hardness can be obtained by rolling,
This can contribute to prolonging the life of the dome contact piece and reducing the size and thickness of the hard disk device and the like. 2) A stainless steel foil having a width of 310 mm or more, particularly 400 mm or more, a thickness of 30 μm or less, a high flatness and a high hardness can be obtained without performing soft annealing between rolling passes in the final rolling step. . For this reason, the production efficiency of rolling can be significantly improved, and in addition to reducing the cost of rolling, it can contribute to improving the quality of the stainless steel foil.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a rolling mill for carrying out the present invention.

FIG. 2 is a diagram showing the relationship between the total draft and the hardness of a rolled stainless steel foil when the rolling temperature is changed.

FIG. 3 is an explanatory view showing an outline of a method for measuring the flatness of a rolled stainless steel foil piece, wherein (a) is an overall view and (b)
FIG. 4 is a cross-sectional view showing the height of the central portion of the stainless steel foil piece.

FIG. 4 is a diagram showing the results of measuring the relationship between the position in the rolling width direction and the amount of warpage of a test piece of stainless steel foil when the test piece was etched.

FIG. 5 is an explanatory diagram showing a method of measuring the amount of warpage,
(A) is a front view, (b) is a side view.

FIG. 6 is a view showing an example of a contour map when a flatness of a rolled stainless steel foil piece is measured by a laser measuring instrument.

[Explanation of symbols]

1: Stainless steel foil 1a: Stainless steel foil piece: Work roll 10: Surface plate A: Height near the center of the stainless steel foil B: Near the end of the stainless steel foil after slitting and removing it Height L: Rolling direction S: Warpage

Claims (3)

(57) [Claims] In a rolling method for obtaining a stainless steel foil having a thickness of 30 μm or less by a reversible multi-stage rolling mill , a stainless steel foil material is rolled in a plurality of rolling passes, and each rolling reduction in the plurality of rolling passes is performed. To 20% or less,
The rolling pass having a total draft of more than 60% is performed by
Rolling a stainless steel foil at a temperature of 50 to 80 ° C. 2. The thickness is 30 μm by a reversible multi-high rolling mill.
Hereinafter, stainless steel rolled to a width of 310 to 550 mm
A steel foil, wherein the stainless steel foil is rolled at both ends in the rolling direction.
Is removed by a predetermined width, and the length in the rolling direction is 300 to 500 m.
When the steel foil pieces cut to m are left on the platen, the platen
The height from the surface to the steel foil piece is 1.5 mm or less, and
A step having a Vickers hardness of 400 or more.
Stainless steel foil. 3. When the steel foil piece is allowed to stand on a platen,
The height A from the board surface to the vicinity of the center of the steel foil piece is 0.2
mm or less, also the rolling direction of the steel foil piece from the surface plate surface
Height B to the vicinity of the end of the
3. The base hardness is 400 or more.
The stainless steel foil according to the above.