JPH11319981A - Punching method for high silicon steel sheet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To appropriately punch a high silicon steel sheet at room temperature without using a special press or the like, and secure a long tool life. SOLUTION: When punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, (1) the clearance is 2 to 10% of the thickness of the steel sheet to be processed and the radius of curvature R of the corner portion is Punching with a tool that is greater than or equal to the thickness of the steel plate to be processed. (2) When performing multiple-stage punching with a progressive die, at least one punching process in the second and subsequent punching processes is performed. This is performed using a tool having a cutting edge having a gradient of 0.3 to 1.5% in a feed direction of the steel sheet or a direction perpendicular thereto, (3) restraining the steel sheet to be processed by using a movable stripper, The load on the movable stripper is controlled to 25 to 80% of the maximum shearing load. (4) Punching is performed using a cemented carbide tool having an average particle size of the hard phase of 3 μm or less. (5) TiCN on the tool surface , TiN, Ti
Punching using a tool coated with at least one of C and TiAlN.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to the present invention, wherein the Si content is 4.0 to 4.0.
The present invention relates to a method for punching a 7.0 wt% high silicon steel sheet.

[0002]

2. Description of the Related Art A high silicon steel sheet having a Si content of 4 wt% or more has a high specific resistance and exhibits low iron loss characteristics in a high frequency band. In particular, when the Si content is around 6.5 wt%, the soft magnetic properties become the best, so that excellent iron loss properties are exhibited. However, silicon steel sheets become brittle at room temperature when the Si content is 4 wt% or more, so it is difficult to process them into thin plates, and mass production as a practical material for a long time has been impossible. However, in recent years, the rolling method (for example,
No. 5001) and siliconizing method (for example,
A thin plate manufacturing technology based on a manufacturing technology disclosed in Japanese Patent Publication No. 5-49745) has been developed and has a thickness of 0.05 mm to 0.5 m.
m high silicon steel sheets can be manufactured.

On the other hand, when assembling a high silicon steel sheet into an iron core such as a transformer or a motor, secondary working such as punching and shearing is required, but there is a problem that the high silicon steel sheet has poor secondary workability. . In order to compensate for such a lack of secondary workability, a method of warm working a high silicon steel sheet is disclosed in
Although this method is proposed in Japanese Patent Application Laid-Open No. 2-263827, this method requires a heating device in a process for heating the material and a processing facility, and has a disadvantage that the equipment cost and the manufacturing cost increase.

On the other hand, proposals have been made for the purpose of improving the workability of the raw material itself. For example, Japanese Patent Application Laid-Open No. Sho 62-270723 discloses that the workability can be improved by controlling the crystal grain size. In addition, Japanese Unexamined Patent Publication No.
In 172940 and the like, it has been proposed to suppress grain boundary oxidation to increase grain boundary strength and improve workability. Among these proposals, in particular, a high silicon steel sheet in which grain boundary oxidation by the latter is suppressed can be sheared or bent at room temperature.

[0005]

However, even high silicon steel sheets with improved workability as described above are brittle at room temperature and are difficult to punch. Further, since the high silicon steel sheet is harder than the normal silicon steel sheet, there is also a problem that the wear speed of the punching tool is high. Also, when punching difficult-to-work materials such as high silicon steel sheets, special punching methods such as precision punching may be adopted.However, such punching methods have extremely small clearances and thus have a long tool life. It is short and requires special presses and tools, which increases the production cost.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for punching a high silicon steel sheet which can perform appropriate punching at room temperature without using a special press or tool and can secure a long tool life. is there.

[0007]

The problem when punching a high silicon steel sheet is that, as the number of times of punching increases, the burr height increases, cracks and chippings increase, and the product defect rate increases. That is. The present inventors have studied the causes of such an increase in burr height and the occurrence rate of cracks and chips, and as a result, increased burr height and occurrence of cracks and chips in punching of high silicon steel sheets. The increase in the rate is that the amount of micro cracks introduced into the product at the time of punching increases as the number of punches increases,
Further, the inventors have found that the cause is that the crack itself becomes larger as the number of times of punching increases. Further, the minute cracks are concentrated at a specific place of the product. In such a place where the minute cracks easily occur, the tool wear is particularly easy to progress, and when such tool wear progresses, the minute cracks are generated. Have been found to be more likely to occur.

[0008] Further, when fine cracks occur, fine powder is generated, and the fine powder becomes an abrasive and causes tool wear to progress. At the same time, the fine powder adheres to the tool surface, and the occurrence of punching failure due to fluctuations in clearance and the like. If cemented carbide, which is harder than normal high-speed steel or die steel, is selected as the tool material to promote adhesive wear of the tool and to increase wear resistance, the tool wear progresses slowly but chipping occurs. Have been found to occur easily and the life of the tool cannot be extended.

Therefore, the present inventors have proposed to reduce the occurrence of minute cracks and reduce the tool wear rate as described above.
Furthermore, it is considered that the best method for punching high-silicon steel sheets is to prevent the occurrence of minute cracks as a product defect even if they occur, and the punching conditions that enable this are examined in more detail. Was.

As a result, by using a punching tool having a specific range of clearance and a corner radius of curvature R determined by the relationship with the thickness of the steel plate to be processed, minute cracks are generated and tool wear is caused. In addition, when performing multiple-stage punching with a progressive die widely used in the punching of high silicon steel sheets, a predetermined gradient is applied to the cutting edge of the second and subsequent steps. It has been found that by using a punching tool, it is possible to effectively prevent the generated microcracks from developing into product defects.

Further, by restraining the steel plate to be processed by using the movable stripper and setting the load of the movable stripper to a specific range determined in relation to the maximum shear load,
The occurrence of micro cracks and tool wear can be suppressed, and further, by selecting a cemented carbide having a hard phase grain size as the tool material, tool wear and chipping can be suppressed, and the life of the tool can be extended. I found something.
In addition, by coating the surface of the punching tool with a film having a specific composition, even if fine powder is generated due to the generation of minute cracks, adhesion to the tool surface does not occur, reducing the occurrence of punching defects and reducing the tooling. It has been found that the life can be extended.

The present invention has been made on the basis of such knowledge, and the characteristic configuration thereof is as follows. [1] In a punching method of a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, the clearance is 2 to 10% of the thickness of the steel sheet to be processed, and the curvature radius R of the corner portion is A method for punching a high silicon steel sheet, comprising punching with a punching tool having a thickness equal to or greater than the thickness of a steel sheet to be processed.

[2] In a punching method of a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, when performing a plurality of steps of punching by a progressive die, the punching of the second and subsequent steps is performed. At least one punching process
A punching method for a high silicon steel sheet, wherein the cutting step is performed using a punching tool having a cutting edge with a gradient of 0.3 to 1.5% in a feed direction or a direction perpendicular to the feed direction of the steel sheet to be processed.

[3] In a method of punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, a steel plate to be processed is restrained using a movable stripper, and the load of the movable stripper is reduced to a maximum shear load. A method for punching a high silicon steel sheet, wherein the method is controlled to 25 to 80%. [4] In a punching method for a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, the average particle size of the hard phase is 3 μm.
A punching method for a high silicon steel sheet, wherein the punching is performed using the following hard metal alloy punching tool.

[5] In a method for punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, T
A punching method for a high silicon steel sheet, comprising performing punching using a punching tool coated with at least one selected from iCN, TiN, TiC, and TiAlN.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below together with the reasons for limiting the same. The object of the stamping method of the present invention is a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%. If the Si content of the steel sheet is less than 4.0 wt%, there is no particular problem in punching, while a high silicon steel sheet having a Si content of more than 7.0 wt% is out of scope because its magnetic properties deteriorate. Such a high silicon steel sheet may be manufactured by any method such as a rolling method, a siliconizing method, and a super-quenching method.

First, the first stamping method according to the present invention will be described. In this punching method, the clearance of the punching tool is 2 to 10 times the thickness of the steel plate to be processed.
Need to be%. If the clearance of the punching tool is less than 2% of the thickness of the steel plate to be processed, the wear rate of the tool is high, and the frequency of polishing the tool is undesirably increased. On the other hand, when the clearance exceeds 10% of the thickness of the steel plate to be processed, minute cracks are easily introduced into the product, and cracks and chips are easily generated. Further, in order to further reduce the wear rate of the tool, it is preferable that the clearance of the punching tool is 4% or more of the thickness of the steel plate to be processed.

In addition, the occurrence of minute cracks is most likely at corners of the product. For this reason, the increase rate of the burr height is large at the corner portion, and the product is liable to crack or chip.
The wear rate is particularly high at the corners of the tool. Hibino et al. Have shown the relationship between tool roundness and tool life (Hibino, Shibata, Miyakawa, Kinoshita: “Plasticity and Machining” 5-46)
(1964), p779). According to this, the radius of curvature R of the tool corner portion (hereinafter simply referred to as “corner R”) is 2 mm of the plate thickness.
When the corner R is smaller than 5%, the wear rate increases as the corner R decreases. On the other hand, when the corner R exceeds 25% of the sheet thickness, there is no correlation between the corner R and the wear rate.

However, as described above, the wear of the tool when punching a high silicon steel sheet is closely related to the generation of micro cracks. Differently, the corner R of the tool is equal to the plate thickness or larger than the plate thickness t (preferably,
R / t ≧ 1.5), it was found that a remarkable wear reduction effect was obtained. For this reason, in the stamping method of the present invention, the corner R of the stamping tool must be equal to or greater than the thickness of the steel sheet to be processed, in addition to the above-mentioned clearance. In order to obtain a particularly excellent wear reduction effect, the corner R is preferably at least 1.5 times the thickness of the steel plate to be processed.

Next, a second punching method according to the present invention will be described. When a high-silicon steel sheet is punched into a product having a complicated shape, a plurality of steps of punching using a progressive die are usually performed. As described above, there is a minute crack that occurs when punching a high silicon steel sheet as a problem peculiar to the punching. However, in the punching process using a progressive die, it is introduced into the steel sheet during the first (first) punching. The microcracks tend to develop due to the impact and bending stress at the time of the second (second) and subsequent punching, causing cracks and chips.

As a result of investigations by the present inventors, in order to prevent such a problem, the second and subsequent punching processes are performed on the cutting blade (punch) in the feed direction of the steel plate to be processed or in a direction perpendicular thereto. It has been found that by using a punching tool having a predetermined gradient and reducing the maximum punching load during processing, the development of minute cracks can be prevented and the frequency of occurrence of cracks and chips can be reduced.

The gradient of the cutting edge is a gradient (inclination) of the cutting edge with respect to the surface of the steel plate at the processing position with respect to the reference surface. Direction (longitudinal direction of the steel plate to be processed)
You may attach along a direction (width direction of steel plate to be processed) orthogonal to this. However, as shown in the examples described later, it is more effective to provide a gradient in the feed direction of the steel plate to be processed.

FIGS. 1A and 1B show a form of punching of the second and subsequent stages using a punching tool having a cutting edge (punch) with a gradient. FIG. 1A shows a case where the cutting edge is punched by a tool in which a cutting edge is provided with a gradient in the feed direction (the longitudinal direction of the steel sheet) of the steel sheet S to be processed. Are cut in the order of x ₁ → x _{2 in} the direction. FIG. 1B shows a case where the cutting edge is punched by a tool having a gradient in a direction (steel plate width direction) perpendicular to the feed direction of the steel plate S to be processed. Are cut in the width direction in the order of y ₁ → y ₂ .

The gradient applied to the cutting blade is 0.3 to 1.5.
% Is appropriate. If the gradient is less than 0.3%, the maximum punching load at the time of punching cannot be reduced effectively. On the other hand, if the gradient exceeds 1.5%, the bending stress applied to the product increases, and on the contrary, the minute cracks Will evolve. In the case of multi-stage machining in which the punching is performed over three or more stages, at least one of the punching processes of the second and subsequent stages is performed with a tool having a sloped cutting edge to thereby prevent cracking and chipping. The frequency of occurrence can be reduced. In addition, by performing all the punching processes of the second and subsequent stages with a tool having a sloped cutting edge, it is possible to more effectively reduce the frequency of occurrence of cracks and chips.

Next, a third punching method according to the present invention will be described. In this punching method, a movable stripper is used to restrain a steel plate to be processed, and its load (hereinafter referred to as “plate holding force”) is reduced to a maximum shear load of 25 to 8.
0% is required. When a movable stripper is used for the punching process, it is possible to suppress the springing of the steel plate at the time of shearing, thereby reducing the wear of the tool. However, it is said that the plate holding force only needs to be about 10% of the maximum shearing load. However, when punching a high silicon steel sheet, the occurrence of micro cracks becomes a problem. Therefore, in order to suppress the generation of micro cracks and reduce the wear rate of the tool, the plate holding force is 25% or more of the maximum shear load. It is necessary to be. If the plate holding force is too large, cracks occur in the steel plate to be processed due to the plate holding force.

Next, a fourth punching method according to the present invention will be described. In this punching method, WC
It is necessary to use a hard-metal-punching tool (for example, a hard-metal alloy tool specified in JIS B 4053) in which the average particle size of the hard phase mainly composed of, for example, 3 μm or less.
Since the high silicon steel sheet has a Vickers hardness of about 400 and is extremely hard, when a die steel or high-speed steel is used as a tool material, the wear rate is high. On the other hand, when a normal cemented carbide tool is used, although the wear rate is low, chipping easily occurs and the tool life is shortened. In order to punch a high silicon steel sheet at a low wear rate and without chipping, it is necessary to use a hard metal stamping tool having a hard phase having an average particle size of 3 μm or less. More preferably, a stamping tool made of a cemented carbide having an average particle size of the hard phase of 1 μm or less may be used.

Next, a fifth punching method according to the present invention will be described. In this punching method, it is necessary to use a punching tool having a tool surface coated with at least one selected from TiCN, TiN, TiC, and TiAlN. Since high-silicon steel sheets are liable to generate minute cracks during punching, fine powder generated at the same time tends to adhere to the tool surface, and adhesion is more likely to occur than in general steel sheets. When such adhesion occurs, occurrence of punching failure due to clearance fluctuation, adhesion wear of the tool, and generation of cracks due to adhesion are promoted. However, one of TiCN, TiN, TiC and TiAlN is formed on the surface of the tool.
By coating the seeds or more, even if fine powder is generated, no adhesion occurs, and the tool life can be extended. The coating thickness is not particularly limited, but is preferably 0.5 μm or more from the viewpoint of abrasion resistance and film uniformity, and is 5 μm or less from the viewpoint of reducing the influence on peeling resistance and clearance. Is desirable.

In the present invention, sufficient effects can be obtained by the above first to fifth methods alone, but by combining any two or more methods, more excellent effects, especially prolongation of tool life, can be obtained. Can be achieved. Further, the effect of the present invention can be naturally obtained even when other measures for extending the tool life, such as the use of a lubricating oil containing an extreme pressure additive, are employed. Life can be extended. Further, in the case of performing the punching process by the progressive feed die, the same gradient as described above may be applied to the punching tool for performing the first-stage (first) punching process for the purpose of silencing or the like.

[0029]

[Example 1] A high silicon steel sheet having a Si content of 6.5 wt% (thickness: 0.3 mm) was prepared by using a punching tool made of die steel and not subjected to surface treatment.
A square hole punching test of mm square was performed. Eight tools were prepared, and the clearance was changed for each. The ratio R / t between the four corners R of the punch and the plate thickness t is 0.25, respectively.
0.5, 1.0, and 1.5 were set. Figure 2 shows an overview of the tool
Shown in The steel plate to be processed was restrained by using a fixed stripper. The press machine uses a 30 ton C type press,
Punching was performed at a speed of 200 spm without lubrication.

FIG. 3 shows the relationship between the burr height and the tool clearance at each corner and straight piece at the start of punching (early stage of punching). Generally, a burr height of 20 μm or less is accepted, but according to FIG. 3, when the clearance of the tool is 2 to 10% of the plate thickness, the burr height at the start of punching is small, and good punching can be performed. It turns out there is. It can also be seen that particularly good punching is possible when the clearance is 4 to 8% of the plate thickness. Such a result is obtained because, when the clearance is too small with respect to the thickness of the steel plate to be processed, a small crack is generated due to the influence of the secondary shear, so that the burr height is increased.
If the clearance is too large, a bending stress acts strongly on the steel sheet, so that minute cracks are generated, and as a result, the burr height is increased.

When the burr height is increased to 50 μm, the number of punches, the clearance of the tool and the corner R /
FIG. 4 shows the relationship with the plate thickness. As described above, the burr height at the start of striking is determined by the clearance of the tool, but the tool life is greatly affected by the clearance of the tool and the corner R as shown in FIG. It can be seen that the tool life is significantly prolonged when is equal to or greater than the plate thickness. This effect is particularly high when the clearance is 4% or more of the plate thickness. Similarly, this effect is more remarkable when the clearance is 2% or more (especially 4% or more) of the plate thickness and the corner R is 1.5 times or more the plate thickness, and the burr height in this region is increased. The speed is the same as the straight part. The preferable condition of the corner R is 1.5 times or more the plate thickness. However, if the corner R is excessively larger than this, there is no further effect of extending the tool life.

Example 2 A high silicon steel sheet (sheet thickness: 0.2 mm) having a Si content of 6.5 wt% was prepared as shown in FIG.
The EI core was punched using a progressive die of a step. In this embodiment, a punching tool made of die steel and not subjected to surface treatment is used. The clearance of the punching tool is set to 15% of the plate thickness to introduce minute cracks intentionally. As a punching tool (E type punch)
A tool whose cutting edge does not have a gradient as shown in FIG. 1, and a cutting edge which has two types of gradients as shown in FIGS. 1 (A) and (B),
In addition, when the punching process is performed using various tools having different gradient sizes and the second stage punching process is performed in a state where a minute crack is generated, the presence or absence of the gradient of the cutting edge, the degree of the gradient, and the product The relationship with the defective rate was examined. In the first-stage punching, a tool (I-type punch) whose cutting edge does not have a gradient as shown in FIG. 1 was used. The corners R of all tools were adjusted to 25 μm, and the steel plate to be processed was restrained using a fixed stripper. The defective rate of the product was evaluated based on the presence or absence of cracks or chips visually observed.

FIG. 6 shows the result. According to the figure, the inclination of the cutting edge of the tool used for the second-stage punching (FIG. 1)
(A) or (B) of 0.3 to 1.5%, a remarkable effect of reducing the product defect rate is observed. Similarly, when the inclination of the cutting edge is 0.7 to 1.5%, a particularly remarkable effect of reducing the product defect rate is recognized. Further, this effect is more remarkably obtained when the inclination of the cutting edge is set along the sheet feeding direction.

Example 3 A high silicon silicon steel sheet (sheet thickness: 0.3 mm) having a Si content of 6.5 wt% was punched into an EI core using a three-stage progressive die as shown in FIG. In this embodiment, a punching tool made of die steel and not subjected to surface treatment is used. The clearance of the punching tool is set to 23% of the plate thickness to introduce minute cracks intentionally. As a tool (punch for punching out) and a third-stage punching tool (E-type punch), a tool whose cutting edge does not have a gradient as shown in FIG.
A tool having a gradient (gradient: 1%) shown in FIG.
The punching process is performed by using various combinations as shown in the above, and when the second and third punching processes are performed in a state where a minute crack is generated, the presence or absence of a cutting edge gradient and the product defect rate are compared. Investigated the relationship. In the first-stage punching, a tool (I-type punch) having a cutting edge having a gradient of 1% as shown in FIG. 1A was used under all test conditions.
The corners R of all the punching tools were adjusted to 25 μm, and the steel plate to be processed was restrained using a fixed stripper. The defective rate of the product was evaluated based on the presence or absence of cracks or chips visually observed.

FIG. 8 shows the result. According to FIG.
When performing punching of a high silicon steel sheet using a progressive die of a stage, at least one of the punching processes of the second and subsequent stages is performed.
It can be seen that the frequency of cracking and chipping can be effectively reduced by performing the punching process a plurality of times using a tool having a sloped cutting blade. Further, it can be seen that the effect of reducing the frequency of occurrence of cracks and chips is more remarkably obtained by performing both the second-stage and the third-stage punching using a tool having a cutting edge with a slope. Therefore, it is considered that the same effect can be obtained in the case of punching using a progressive die having four or more steps.

Example 4 A high silicon steel sheet (sheet thickness: 0.3 mm) having a Si content of 6.5 wt% was punched into a ring shape having an outer diameter of 45 mm and an inner diameter of 33 mm by a punching machine equipped with a movable stripper. . In this embodiment, using a punching tool made of die steel and not subjected to surface treatment,
The clearance of this punching tool was set to 10% of the plate thickness. Also, to control the load on the movable stripper,
Punching was performed by using a spring with a changed spring constant and further changing the stroke of the movable stripper. Further, a load cell was attached to the tool and the movable stripper, and the maximum shear load and the plate pressing force were measured. After the punched ring was subjected to strain relief annealing, the core loss was measured and the punched end face was observed. The outer periphery of the ring was observed using an optical microscope with a magnification of 500 times, and the case where the number of minute cracks occurred was 1 or less was classified as “small”, and the case where 2 or more microcracks occurred was classified as “many”.

The results are shown in Table 1. According to the table, in the example of the present invention in which the movable stripper is used to restrain the steel plate to be processed and the load (plate holding force) by this is set to 25 to 80% of the maximum shearing load, a minute crack is generated on the end face. It can be seen that a high-silicon steel sheet can be punched without any problem, and as a result, a ring core having good magnetic properties can be obtained.

[0038]

[Table 1]

Example 5 A high-silicon steel sheet having a Si content of 6.5 wt% (thickness: 0.3 mm) was subjected to a punching test using a punching tool (no surface treatment) shown in FIG. For the punching tool, the clearance was adjusted to 6% of the plate thickness, five types of cemented carbide tools with different average grain sizes of the hard phase were prepared, and one die steel and one high-speed steel tool were prepared.
Available in different types. Other conditions were the same as in Example 1. After punching out 300,000 times, the chipping occurrence state and the wear state of the tool were observed. The occurrence of chipping is determined by the tool straight
The edge having a length of mm was observed by SEM, and the number of chippings having a size of 10 μm or more was counted and evaluated. The wear state of the tool was evaluated by measuring the edge shape of the straight piece portion of the tool with a two-dimensional shape measuring machine and calculating the area shown in FIG.

Table 2 shows the results. According to the table, in the example of the present invention using a cemented carbide tool having an average grain size of the hard phase of 3 μm or less as the tool, it is possible to punch a high silicon steel sheet at a low tool wear rate and without chipping. It turns out that it is possible.

[0041]

[Table 2]

Example 6 A high-silicon steel sheet having a Si content of 6.5 wt% (thickness: 0.3 mm) was subjected to a punching test using a punching tool shown in FIG. The tool material is high-speed steel and a cemented carbide in which the average grain size of the hard phase is adjusted to 3.9 μm.
A tool coated with iCN, TiN, TiC, and TiAlN and a tool subjected to a diffusion treatment of NbC and VC were prepared, and punching was performed using these tools. Other conditions were the same as in Example 5, and after punching out 300,000 times, the tool was subjected to the same observation as in Example 5.

Table 3 shows the results. According to the table, the wear can be reduced under all conditions using a tool that has been subjected to a surface treatment. However, to suppress the occurrence of chipping, the surface of any one of TiCN, TiN, TiC, and TiAlN can be reduced. It turns out that the coating is effective. It is known that chipping is accelerated by the adhesion phenomenon.
It is considered that the coating of iCN, TiN, TiC, and TiAlN suppresses adhesion. Also, NbC, VC
In the case of the diffusion treatment, it is considered that although the hardness increases, it is effective in reducing abrasion, but the adhesion cannot be prevented, so that the toughness is deteriorated due to the increase in the hardness and chipping frequently occurs.

[0044]

[Table 3]

[0045]

According to the method for punching a high silicon steel sheet according to the present invention described above, it is possible to perform a punching process with a long tool life and a low frequency of occurrence of product defects. Processing can be performed.

[Brief description of the drawings]

FIG. 1 shows a punching tool having a beveled cutting edge,
Explanatory drawing showing the outline of the punching process status by this

FIG. 2 is an explanatory view of a punching tool used in Example 1.

FIG. 3 is a graph showing the effect of the clearance and corner R / thickness t of a punching tool on the burr height at the start of punching.

FIG. 4 is a graph showing the effect of the clearance of the punching tool and the corner R / plate thickness t on the increasing speed of the burr height.

FIG. 5 is an explanatory diagram showing the state of execution of a two-stage punching process by a progressive die performed in Example 2.

FIG. 6 shows a two-stage punching process using a progressive die.
A graph showing the effect of the presence or absence of the cutting edge gradient and the degree of the gradient on the occurrence of defective products of the tool subjected to the second-stage punching process

FIG. 7 is an explanatory view showing the state of execution of three-stage punching by a progressive die performed in Example 3.

FIG. 8 shows a three-stage punching process using a progressive die.
The graph which shows the influence which the presence or absence of the cutting edge gradient of the tool which performed the 2nd stage and the 3rd stage punching process has on the occurrence of a product defect.

FIG. 9 is an explanatory diagram relating to a method for evaluating a tool wear state;

Claims (5)

[Claims] In a method for punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, a clearance is 2 to 10% of a thickness of a steel sheet to be processed, and a radius of curvature of a corner portion. A punching method for a high silicon steel sheet, wherein the punching is performed by a punching tool in which R is equal to or greater than the thickness of the steel sheet to be processed. 2. A method for punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, wherein when performing a plurality of stages of punching with a progressive die, at least one of the second and subsequent stages of punching is performed. A step of performing a single punching operation by using a punching tool having a cutting edge with a gradient of 0.3 to 1.5% in a feed direction of a steel plate to be processed or in a direction perpendicular to the feed direction. Stamping method for steel sheet. 3. A method of punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, wherein a movable steel stripper is used to restrain a steel sheet to be processed, and a load of the movable stripper is reduced to a maximum shear load of 25. A method for punching a high silicon steel sheet, wherein the method is controlled to be up to 80%. 4. A punching method for a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, wherein the punching is performed using a hard metal punching tool having an average grain size of a hard phase of 3 μm or less. A method for punching a high silicon steel sheet. 5. A method for punching a high silicon steel sheet having a Si content of 4.0 to 7.0 wt%, comprising:
1 selected from CN, TiN, TiC, TiAlN
A punching method for a high silicon steel sheet, wherein the punching is performed using a punching tool coated with at least one kind.