JPS63219526A - Method for leveling saw - Google Patents

Abstract

PURPOSE:To easily obtain desired leveling strength, by pressing the specified part to be leveled prior to the other part, and further projecting shot particles to adjust the strength in the cooling of the saw material for hardening and/or tempering. CONSTITUTION:When the saw material heated to a hardening temp. is cooled and/or the material heated to a tempering temp. is cooled, the required part to be leveled around the toothed part is pressed prior to the other part. The other part is then pressed afterward. The cooling rates at both parts are differentiated to produce compression stress at the required part. Consequently, tensile internal force is produced at the region between the required part and the toothed part. Shot particles are then projected to adjust the leveling strength.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a method for stiffening a saw material during the manufacturing process of a saw.

b. Prior Art Generally, when a force is applied to a material, a certain amount of deformation occurs, but as the applied force is gradually increased, the amount of deformation increases accordingly.

However, depending on the shape of the material and how the force is applied, when the applied force reaches a certain level, a phenomenon occurs in which the deformation up to that point suddenly shifts to a deformation that is different from the total heat, that is, a buckling phenomenon.

In the case of circular saws and band saws, the above-mentioned buckling phenomenon may occur due to thermal stress. The mechanism by which this buckling phenomenon occurs is as follows.

For example, when a circular saw is used to rotatably cut an object such as wood or wood-based materials (including plastics), frictional heat is generated on the outer circumference of the circular saw, but at this time, frictional heat is generated on the inner circumference of the circular saw. Since no frictional heat is generated, a relatively large temperature gradient occurs between the outer and inner circumferences of the circular saw. However, due to the frictional heat generated at the outer periphery, the area near the blade of the circular saw tries to expand at the outer periphery, but cannot do so due to the resistance at the inner periphery, so a tensile force is applied to the inner periphery. As a reaction, compressive stress is generated in the outer circumferential portion. Therefore, the rate of expansion between the outer circumference and the inner circumference of the circular saw is greatly different, and as the outer circumference expands, compressive stress is generated on the outer circumference and tensile stress is generated on the inner circumference, and as a result, A stress gradient is created between the outer and inner circumferences of the circular saw.

When the thermal stress becomes large and the temperature of the outer periphery of the circular saw rises to a certain level, what had been expanding and contracting in a plane suddenly undergoes a different type of deformation (for example, as shown in Figures 11 and 12). This causes the circular saw a to become concave like a dish or become wavy. If such deformation or buckling occurs, the circular saw will no longer be able to cut, causing problems in cutting operations.

Therefore, in order to prevent the occurrence of buckling due to frictional heat as described above, the circular saw material is subjected to a stiffening process.

This tightening process is performed by applying plastic stretching to an appropriate annular portion of the circular saw material, which applies tensile internal force in the circumferential direction at the outer periphery near the saw blade, causing thermal stress during cutting. As a result, the compressive stress in the tangential direction generated on the outer periphery of the saw blade is canceled out, and buckling is effectively prevented. In the case of a band saw, the belt-shaped region between the blade portion and the saw back portion of the band saw material is also stretched plastically to perform the waist-fitting process.

By the way, this type of tightening method includes a hammering method in which a worker hits the plate surface of the saw material with a hammer to perform plastic expansion processing, and a metal roller is applied to each side of the saw material in pairs. The roller processing method, in which plastic stretching is performed by strongly clamping and pressing metal rollers, has been widely used in the past.

Problems to be Solved by the C0 Invention However, the above-mentioned conventional methods of tightening, such as the hammering method and the roller processing method, have the following major problems.

First, in the case of the hammering method, it requires a great deal of intuition and skill to strike the saw material with a hammer and apply plastic expansion processing to the predetermined waist-in portions, and in particular, it requires a great deal of intuition and skill. Since many years of experience and skill are required to achieve uniform buckling strength over the entire saw, it has been difficult to save labor and automate the saw manufacturing process. Furthermore, even if a person is sufficiently skilled, the work efficiency is very poor and it is difficult to obtain a homogeneous product, so it is not possible to mass-produce high-quality saws at low cost.

Next, in the case of the roller processing method, it does not require intuition or tricks as compared to the hammering method. It is easily affected by the quality of accuracy of rotary grinding (such as rotary grinding for grinding), and it is easy to cause local strength or weakness in tightening. Therefore, the strength of tightening is often uneven over the entire surface of the machined surface. In such cases, roller pressure has been applied repeatedly, or the previously described hammering method has been used in combination.

For this reason, there have been major problems in that production efficiency is extremely low and it is difficult to obtain uniform stiffening strength under certain processing conditions.

Moreover, in the hammering method and roll pressing method as mentioned above,
The reality is that it is not possible to obtain a sufficiently strong waist-in strength.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to make it possible to perform the cutting process of a saw efficiently without requiring any skill such as intuition or tricks. To provide a waist-inserting method which can obtain sufficiently strong waist-inserting strength and can be labor-saving and automated.

Means for solving the d0 problem In order to solve the above-mentioned problem, in the present invention, when press hardening and press tempering the saw material,
When cooling the saw material that has been heated to a required hardening temperature, or when cooling the saw material that has been heated to a required tempering temperature, the area around the saw blade portion of the saw material is By starting pressing the predetermined part to be tightened before other parts and pressing the other parts after this, the cooling rates of the predetermined part and the other parts are made different, thereby making it possible to A tightening process is performed by generating a compressive stress in the part and a tensile internal force in a region between the predetermined part and the saw blade, and then the predetermined part of the saw material to be tightened or the part thereof is tightened. Shot grains are projected onto other areas to adjust the strength of the waist.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 10.

First, FIG. 1 shows a circular saw material processing device 1 used for carrying out the waist tightening method according to the present invention.
This device 1 includes an upper mold 2. A predetermined high frequency current is supplied to a high frequency coil 8 via a press device 5 having a lower mold 3 and a circular saw material handling mechanism 4, a cooling oil tank 6 and a support member 7 arranged on the side of this press device 5. a high frequency transformer 9;
They are each equipped with a transfer means IO for horizontally moving the high frequency coil 8 and the high frequency transformer 9, and a high frequency power source (not shown).

Note that the circular saw material 11, which is the workpiece, is formed by punching out a thin steel plate to form a central hole 11a in the center and a saw blade portion 11b at the outermost periphery, as shown in FIG. It is.

The bracing surfaces 2a and 3a of the upper mold 2 and lower mold 3 are provided with annular protrusions 12 and 13 corresponding to the portions of the circular saw material 11 to be tightened, and a plurality of radially extending grooves. 27
(see FIG. 2), and the upper mold 2 is moved in the vertical direction by a pressure cylinder 14. Further, the circular saw material handling mechanism 4 includes a mounting table 16 inserted into the central hole 15 of the lower mold 3, and a mounting table 16 disposed through the central hole 15 of the lower mold 3.
It is composed of an elevating cylinder 17 for vertically moving the mounting table 16, and an induction motor 18 for rotationally driving the mounting table 16.

On the other hand, as shown in FIG.
Lead portions 20a and 20b are connected to a top plate 19a which is divided into two parts. Note that a semicircular notch 21 corresponding to the center hole 11a of the circular saw material 11 is provided at the center of the upper plates 19a and 19b.
a, 21b are formed.

Next, the operation of cutting the circular saw material 11 using the apparatus 1 having such a configuration will be described.

First, the circular saw material 11 is mounted and fixed on the mounting table 16 by engaging the central hole 11a of the circular saw material 11 with the mounting table 16. In this case, the mounting table 16 is placed in advance between the upper mold 2 and the lower molds 3 and 6 and at the same height as the high-frequency coil 8, so that it is placed and fixed on the mounting table 16. The circular saw material 11 will be placed at a predetermined heating position.

Thereafter, the high frequency coil 8 together with the high frequency transformer 9 is horizontally moved toward the press device 5 by the transfer means 10 and inserted between the upper mold 2 and the lower mold 3.

As a result, as clearly shown in FIGS. 3 and 4, approximately half of the circular saw material 11 is inserted and placed in the center between the upper surface plate 19a and the lower surface 1!19b of the high-frequency coil 8 in a freely rotatable state. .

Next, as the induction motor 18 is driven to rotate, the circular saw material 11 is driven to rotate together with the mounting table 16. At the same time, a high frequency large current is supplied from the high frequency power supply to the high frequency transformer 9, and a high frequency large current is caused to flow through the high frequency coil 8 as shown by the arrow in FIG. In this case, the high frequency power source is selected in the frequency range of 30 kHz to 400 +lz depending on the thickness of the circular saw material 11. As a result, each part of the circular saw material 11 is uniformly heated by high frequency induction.

Then, when the circular saw material 11 reaches the required hardening temperature,
The supply of high-frequency large current to the high-frequency coil 8 is cut off to complete the heating process, and the high-frequency coil 8 is transferred to the transfer means 10.
The high-frequency transformer 9 is moved back to its original position and placed out of the space between the upper mold 2 and the lower mold 3.

At the same time, the rotation of the circular saw material 11 is stopped and lowered by the lifting cylinder 17, whereby the circular saw material 11 is lowered by the lifting cylinder 17.
is placed on the protrusion 13 of the lower mold 3 with its center hole 11a corresponding to the center hole 15 of the lower mold 3.

On the other hand, in synchronization with the high-frequency coil 8 being removed from between the upper mold 2 and the lower mold 3, the mold 2 is lowered toward the lower mold 3 by the pressure cylinder 14, thereby making a round shape. Saw material 11
is pressurized between the upper mold 2 and the lower mold 3 as shown in FIG. 5(1).

To explain in detail the operation at this time, the circular saw material 11 heated to the required hardening temperature is placed on the protrusion 13 of the lower mold 3. Then, when the upper mold 2 is lowered, the circular saw material 11 is placed on the protrusion 13 of the lower mold 3. The protrusion 12 of the mold 2 first comes into contact with the surface of the circular saw material 11.

Therefore, in the initial stage, as shown in FIG. 5(1), only the portion M of the circular saw material 11 to be cut is held between the protrusions 12 and 13 of the upper mold 2 and the lower mold 3. On the other hand, the other portion N of the circular saw material 11 is not brought into contact with the pressing surfaces 2a and 3a of the upper mold 2 and the lower mold 3. Therefore,
Since the heat of the portion M of the circular saw material 11 to be cut is dissipated to the protruding portion 12.13 by conduction, the cooling rate of the predetermined portion M is faster than the cooling rate of the other portions N. Become. As a result, the residual stress generated in the circular saw material 11 has a different stress distribution between the predetermined portion M and the other portions N, and compressive stress is applied to the predetermined portion M, while compressive stress is applied to the predetermined portion M. A tensile internal force is applied in the circumferential direction to the region P between the outermost blade portion 23b and the outermost blade portion 23b. As a result, the circular saw material 11 is tightened.

Note that as the predetermined portion M cools and contracts,
Since the other portion N of the circular saw material 11 is held between the pressing surfaces 2a and 3a of the upper mold 2 and lower mold 3 as shown in FIG. 5(II), normal press hardening is performed.

In other words, as soon as this condition occurs, the cooling oil tank 6
Cooling oil is supplied to the circular saw blank 11 from the press, and the circular saw blank 11 is rapidly cooled and hardened by this cooling oil under the press condition. Once this hardening process is completed,
The upper mold 2 is moved upwardly by the pressure cylinder 14, and the hardened circular saw material 11 is removed from the apparatus 1.

Thereafter, the quenched circular saw material 11 is cleaned of cooling oil by a cleaning device (not shown), and then processed in the same manner as described above by another circular saw material processing device having the same configuration as the device 1. It is tempered at. A compressive stress is applied to the predetermined portion M, while a tensile internal force is applied in the circumferential direction to a region P between the predetermined portion M and the outermost blade portion 23b, and as a result, the circular saw material 11 will be processed to add waist. Note that although the induction hardening conditions and the tempering conditions are different, the magnitude of the high frequency current, the current application time, etc. are automatically switched according to a predetermined program according to the mutual relationship between the hardening conditions and the tempering conditions.

The circular saw material 11 that has been hardened and tempered as described above is rotary ground, and then subjected to shot peening in a subsequent shot peening device.

Figure 6 shows the shot peening device 22 used in this example.
This device 22 includes a holding jig 23 for holding a disk-shaped circular saw material 11 that is a workpiece, a drive mechanism 24 for rotationally driving this holding jig 23, and a shot grain cutting machine. The apparatus includes a main body 26 consisting of a projection mechanism 25.

The above-mentioned device main body 26 has a chamber 28a divided into two upper and lower stages.
.

28b, a holding jig 23 is disposed on the partition wall 30 of this housing 29, and the housing 29 is disposed in relation to this holding jig 23.
A drive mechanism 24 is disposed within the chamber 28b below.

This drive mechanism 24 includes an induction motor 34 that applies rotational force to a drive shaft 33 via a rotational force transmission mechanism 32 consisting of a belt and a pulley, and the drive shaft 33 is inserted into the bearing portion 35 of the holding mechanism 3. It is inserted in a rotatable state, and its tip is connected to a base 36 for holding a workpiece.

As shown in FIGS. 6 to 8, the above-mentioned holding jig 23 includes the base 36, a ring-shaped member 37a vertically fixed on the base 36, and a ring-shaped member 37a fixed to the base 36. A ring-shaped member 37b that is attached facing each other, a ring-shaped intervening member 28 that is arranged between these ring-shaped members 37a and 37b, and a ring-shaped intervening member 28 that is attached to both sides of the circular saw material 11 on the inner diameter side of the ring-shaped members 37a and 37b. It is composed of a pair of mask plates 39a and 39b.

Further, on the side wall 40 of the chamber 28a above the housing 29, the shot particle projection mechanism 25 described above is arranged. The shot grain projection mechanism 25 of this example is of a centrifugal force type, and includes a shot grain supply source 41 and a shot grain supply pipe 42.
and the side wall 4 of the housing 29 is connected to the tube 42 and
0, an impeller 44 rotatably disposed within the horn-shaped member 43, and a motor 45 that rotationally drives the impeller 44 in a vertical plane.
It is composed of. The impeller 44 used is, for example, one with a diameter of 400 mm and a number of blades of 8, which is driven to rotate at a rotation speed of 150 degrees r, p, m by a motor 45 and a belt 46. by 0.5
-1.2 shot grains (steel balls) are projected into the chamber 28a at a speed of 50 to 60 m/s.

Furthermore, a shot grain discharge hole 48 is formed at the outer edge of the partition wall 30 of the housing 29, and a shot grain guide wall 50 is provided near the inside of the side wall 49 of the housing 290 chamber 28b. guide wall 50
A passage 51 is formed at. One end of a shot grain suction tube 52 is connected to the lower end of the passage 51.
The other end of this tube 52 is connected to a separator 53 arranged above the housing 29. This separator 53
This is to separate and discharge shot particles that are damaged to the extent that they cannot be reused out of the projected shot particles, and those that are intact or similar to those that can be reused are separated and discharged through the connecting pipe 54. This is fed back to the shot grain suction tube 41. Further, a storage device 56 is connected to the horn-shaped member 43 of the shot particle projection mechanism 25 via a suction pipe 55.

Next, the operation of the shot peening device 22 having the above-described structure will be described.

First, the circular saw material 11 obtained by press hardening and press tempering using high frequency induction heating as described above is attached to the holding jig 23 of the device main body 26 as shown in FIG. The circular saw material 11 is held vertically.

To attach the circular saw material 11 to the holding jig 23, place the outer peripheral edge of the circular saw material 11 on the ring-shaped member 37a so that it is coaxial with the ring-shaped member 37a, and attach the other ring-shaped member 37b. A ring-shaped member is applied coaxially to the outer peripheral edge of the other surface of the circular saw material 11 and is arranged between the pair of ring-shaped members 37a and 37b on the outer peripheral edge of the circular saw material 11 and the outer peripheral side thereof. The intervening member 38 is inserted together, and in this state, the ring-shaped members 37a and 37b are tightened at several locations with bolts 58 and nuts 59 (see FIGS. 7 and 8). ). As a result, circular saw material 1
1 is firmly held between a pair of ring-shaped members 37a and 37b. Next, the ring-shaped members 37a, 37b
By arranging circular mask plates 39a and 39b of the same size and coaxially on both sides of the circular saw material 2 and using the center hole 11a of the circular saw material 11, the bolt 60 Tighten and secure with nuts 61. As a result, the circular saw material 11 is moved to the ring-shaped member 3.
7a, 37b and mask plates 39a, 39b are used to mask both the front and back surfaces except for predetermined portions A and B (surfaces corresponding to the portion M).

Thus, the circular saw material 11 is attached to the holding jig 23 with only the annular portions A and B exposed.

After the circular saw material 11 is attached to the holding jig 23 in this manner, the induction motor 34 is operated to rotate the holding jig 23 and the circular saw material 11 in the direction indicated by the arrow in FIG. . Next, a large number of shot grains are supplied from the shot grain supply source 41 through the supply pipe 42 into the horn member 43, and the shot grains are transferred to the circular saw material 11 by the impeller 44 which is rotated at high speed by the motor 45. Projecting toward the annular portion A.

B is subjected to tsusei processing. At this time, the portions of the circular saw material 11 other than the annular portions A and B are completely masked as described above, so no plastic working is performed at all.

As described above, after the cutting of the annular portions A and B of the circular saw material 11 is completed by projecting the shot particles for a predetermined period of time, the projection of the shot particles is stopped.

Incidentally, the shot shot grains pass through the hole 38 of the partition wall 30 and fall into the passage 51 of the lower chamber 28b, and are transferred to the separator 53 via the shot grain suction pipe 52, so that only reusable crushed grains are removed. Separated and discharged to the outside,
The reusable shot grains are again supplied to the shot grain supply source 41 and recycled.

Next, a specific example in which the tightening method according to the present invention is implemented using the circular saw material processing device 1 and the shot peening device 22 as described above will be shown below.

l Evidence (1) Material of circular saw material SKS 5 (2) Dimensions of circular saw material Outer diameter 305N Center hole diameter 25.4 +n Plate thickness? Number of teeth: 79 (3) Operating conditions of circular saw material processing equipment (4) Operating conditions of shot peening equipment A: Diameter of shot grains 0.8 B (B) Hardness of shot grains HRC5B (H) Material of shot grains
Cast steel <2> Shot grain projection speed 50 m/s E) Shot grain projection angle 90° Duration Shot grain projection time 5 minutes T> Circular saw material rotation speed 10 r, p, +w Under these conditions As a result of hardening and tempering the circular saw material 22 in the processing apparatus 1, the following results were obtained.

In addition, the residual stress on the surface of the circular saw material obtained by processing using the previously described circular saw material processing device 1 and rotary grinding and the circular saw material obtained by processing using the shot peening device 22 is As a result of the measurement, results as shown by a dashed line and a solid line in Fig. 1θ were obtained. In FIG. 10, the vertical axis represents the residual stress, and the horizontal axis represents the ratio of the distance Mr from the center of each part to the radius R of the circular saw material 11.

As is clear from the measurement results shown by the dashed line in FIG.
A small compressive stress (negative stress) is generated in the 16 m part (circular part L from 0,695R to 0.761H) and the part on the inner diameter side, and from the center to the outer diameter slightly more than 116 M A small tensile stress (positive stress) is generated in the area from the side part to the outermost saw blade part 11b,
Therefore, it was confirmed that the circular saw material 11 was subjected to a weak tightening process.

Furthermore, as is clear from the solid line in Fig. 10, a very large compressive stress is generated in the annular portions A and B onto which shot grains are projected, that is, the shot processed portion (band-shaped portion M from 0.695R to 0.761R). As a reaction, the outer peripheral portion of the circular saw material 11, that is, this annular portion A
, B and the outermost saw blade portion 11b, a larger tensile stress was generated in the portion C, and it was confirmed that this caused strong stiffening.

Therefore, even if the heat generated in the outer peripheral part C near the outermost periphery where the blade is attached when using a circular saw causes frictional heat to be generated in this outer peripheral part C and compressive stress is generated inside it, shot peening cannot be performed. Annular part A to which compressive stress is applied
, B, a tensile stress is applied in advance to the outer peripheral portion C, so that the inner diameter portion undergoes thermal expansion without applying any tensile force, and therefore no large stress gradient occurs. The thermal buckling phenomenon of the saw can be effectively prevented.

In order to confirm such an effect, a cutting test was conducted after attaching a tip blade made of cemented carbide or the like to the saw blade portion 11b of the circular saw material 11 obtained in this example after the saw blade portion 11b was set. The abnormal phenomenon of thermal buckling did not occur at all, and the durability was the same as that of products made by conventional hammering or roll pressing methods, and good results were obtained.

In addition, in the above-mentioned specific example, the predetermined annular portions A and B of the circular saw material 11, that is, 0.695R from the center of the circular saw material 11.
Although shot peening was performed on a band-shaped area of ~0.761R (where R is the radius of the circular saw material 11), as a result of numerous experiments, shot peening was performed on an annular area in the range of 0.6~0.8R. It was confirmed that a good waist inserting process could be achieved by doing so.

Furthermore, FIG. 9 shows the holding jig 23 tilted sideways, and in this case, the circular saw material 2 can be attached to the holding jig 3 without using the mask plates 39a and 39b described above. By using only the pair of ring-shaped members 37a and 37b, shot grains are projected from a predetermined location between the center and the outer periphery of the circular saw material 11 to the entire surface on the inner diameter side. results of the experiment,
In this case as well, it was confirmed that a good waist-insertion process with strong waist-insertion strength was achieved, similar to the case described above.

In addition, as a result of the experiment, it was confirmed that even when the projection area of the shot grains was set to the entire inner diameter side from the part 0.5R-0.8H from the center of the circular saw material 11, it was possible to perform good waist cutting. It was done.

After processing the thus obtained circular saw material and brazing a cemented carbide chip blade to the blade portion 28b,
A cutting test was conducted and good results were obtained. In other words, even though the circular saw was only heat treated and was not stiffened by mechanical external force such as hammering or roll pressure, no abnormal phenomenon of thermal buckling was observed. The durability was also similar to that of conventional products made by mechanical external force such as hammering or roll pressing.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made based on the technical idea of the present invention.

For example, in all of the above-mentioned embodiments, shot peening is used to obtain stronger stiffening strength when the stiffening process is insufficient in the press hardening/press tempering process, but in the opposite case, i.e. If the stiffening process in the press hardening/press tempering process is too strong, it is possible to weaken the stiffening strength by shot peening. In the case of Figure 8,
Either masking the annular parts A and B of the circular saw material 11 and projecting shot grains onto the other parts, or in the case of FIG. By masking 11b and projecting shot grains onto the outer circumferential portion C, the waist-fitting strength can be reduced. It should be noted that the degree of reduction in the waist insertion strength can be easily adjusted by appropriately changing the material (soft material, etc.) of the shot grains, the projection speed, etc., in particular.

In addition, in all of the above-mentioned embodiments, the protrusions of the upper and lower molds are brought into contact with the waist-fitting portions during both press hardening and press tempering to cool them quickly; however, during press hardening or press tempering, Such an operation may be performed only during one of the tempering operations. moreover,
The protrusion does not necessarily need to be provided on both the upper and lower molds, and may be provided only on either the upper or lower mold. Further, the heating source for the circular saw material is not limited to high frequency heating means, but it is also possible to use a continuous furnace, flame heating means, etc.

In addition, the shot peening processing conditions are not limited to the above example, but may include the shot direction and shot speed.

By appropriately changing the particle size, material, etc., the waist-fitting strength can be easily adjusted.

In addition, although circular saw materials are used as workpieces in all of the above-mentioned embodiments, the method and device for tightening according to the present invention can also be applied to hardening, tempering, and tightening processing of band saw materials. Needless to say, it can be applied.

e1 Effects of the Invention As described above, according to the present invention, by pressing the predetermined portion of the saw material to be tightened before other portions, the cooling rate in these cut portions is made different and the predetermined portion is pressed. Since a compressive stress is generated, and thereby a tensile internal force is generated in the area between the predetermined portion and the blade, a certain amount of stiffening can be applied only by press hardening or press tempering, and then Then, shot grains are projected onto a predetermined portion of the saw material to be tightened or other portions to adjust the tightening strength, so that it is possible to easily obtain the required tightening strength. .

However, since such operations can be performed using automated equipment without requiring any intuition or skill, it is possible to save labor and produce uniform, high-quality saws. It is possible to manufacture efficiently.

[Brief explanation of the drawing]

1 to 10 are for explaining one embodiment of the present invention, in which FIG. 1 is a partially cutaway front view of a high-frequency induction heating type circular saw material processing device, and FIG. Figure 2 is a plan view of the lower mold, Figure 3 is a perspective view of the high-frequency coil, Figure 4 is a sectional view taken along the line IV-IV in Figure 3, and Figure 5 (1) shows that the circular saw material is the upper mold and FIG. 5(n) is a cross-sectional view showing a state where the circular saw material is held between the protruding parts of the lower mold, and the protruding parts are embedded in the circular saw material and the circular saw material is spread over the entire surface of the upper mold and the pressing surface of the mold. Figure 6 is a cross-sectional view of the sawtooth peening device, and Figure 7 is a front view of the jig that holds the circular saw material. Figure 8 is a cross-sectional view taken along the line ■-■ in Figure 7. Figure 9 is a sectional view similar to Figure 8 showing separate holding jigs, Figure is a graph showing the measurement results of the residual force of the circular saw material after shot peening, Figures 11 and 12 are FIG. 3 is a cross-sectional view showing the buckled state of the saw. l... Circular saw material processing device, 2... Upper mold, 3...
...Lower mold, 2a, 3a...Press surface 8...High frequency coil, 11...Circular saw material,
11b...Saw blade part, 12.13...Protrusion part, 22.
... Shot peening device, 25... Shore) Grain projection mechanism, 37a, 37b... Ring-shaped member, 39a, 39b... Mask plate, A... Annular part of circular saw material, (Sea mark) Projection area of cut grains) C: Outer periphery of the circular saw material. Previous Figure 3 Omaru Figure 4 Figure 5
Figure 7! ■'' Figure 8 Figure 9 ＼2-N-一ノ)♂Bea

Claims (1)

[Claims] When press hardening and press tempering the saw material, at least one of cooling the saw material that has been heated to a required quenching temperature, or cooling the saw material that has been heated to a required tempering temperature. At this time, the predetermined portion of the saw material to be tightened around the saw blade is pressed before the other portions, and the other portions are pressed after this. The cooling rate of the other parts is made different, thereby generating compressive stress in the predetermined part and generating tensile internal force in the area between the predetermined part and the saw blade part, thereby performing a tightening process, A method for tightening a saw, characterized in that, after that, shot grains are projected onto a predetermined portion of the saw material to be tightened or other portions to adjust the tightening strength.