JP3377947B2 - Rotary cutting whetstone - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary cutting whetstone used for cutting stone, concrete, refractory and the like. 2. Description of the Related Art Conventionally, a rotary cutting grindstone in which a plurality of segment chips obtained by solidifying diamond-based abrasive grains with metal bonds is attached to the outer periphery of a substrate has been used for cutting stones, concrete, refractories and the like. I have. [0003] In such a rotary cutting grindstone, there are laser welding and electron beam welding as methods for bonding a segment chip and a substrate. The material of the substrate that can use this laser welding and electron beam welding is an iron-based material, and the bond of the abrasive layer of the segment chip to be adhered to the substrate is C
These are u-Sn-based, Co-based, Ni-based, and W-based metal bonds. When a segment chip is directly adhered to a substrate by laser welding or electron beam welding, Sn having a low melting point contained in the bond is melted out, and a blowhole is generated at that portion. If the bonding surface has a blowhole, the segment chip may be peeled off during the cutting operation, which is problematic in terms of safety. In addition, the laser is irregularly reflected at the diamond portion, resulting in incomplete welding and carbonization of the diamond. In order to avoid such a problem, a method has been adopted in which an underlayer having a composition similar to the material of the substrate is formed under the abrasive layer, and the segment chip is bonded to the substrate by bonding the underlayer to the substrate. ing. As such a technique, for example, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open No. 1-257777 discloses a method of bonding a segment chip sintered together using a diamond-based abrasive and a bonding metal powder with an iron-based powder as a base layer to an iron-based substrate by electron beam welding. Is disclosed. As described above, when a segment chip is adhered to a substrate by laser welding or electron beam welding with an underlayer of a material similar to that of the substrate interposed, the underlayer and the abrasive grains The composition of the layers can vary widely. Therefore, if the physical properties of the underlayer and the abrasive layer are different, especially if the thermal expansion coefficients are different, a difference in expansion coefficient and contraction rate between the underlayer and the abrasive layer during sintering and cooling occurs, respectively. . Further, when the segment chip after sintering is bonded to the substrate by laser welding or electron beam welding,
Since the underlayer is heated to about 2000 ° C., the abrasive layer and the substrate near the underlayer are also heated to a high temperature. For this reason, at the time of bonding by laser welding or electron beam welding, and at the time of cooling thereafter, a difference in expansion rate and contraction rate occurs between the substrate, the underlayer, and the abrasive layer. When the difference between the expansion rate and the contraction rate occurs,
Residual stress is generated at the boundary between the substrate and the underlayer and at the boundary between the underlayer and the abrasive layer. Due to the residual stress, a bending stress is generated in the underlying layer between the substrate and the abrasive layer. FIG. 8 is a view showing the state of generation of the bending stress, and schematically shows the bending stress for one segment chip S of the rotary cutting grindstone. Generally board B
And the underlayer H are made of a similar material, and the abrasive layer D has a larger expansion rate and shrinkage rate than the substrate B and the underlayer H. A bending stress represented by a triangular distribution having a maximum bending stress σ _max occurs at the center. The bending stress generated in the underlayer H is
And the bending stress increases as the length of the underlayer H increases. For this reason, conventionally, laser welding, so that the bending stress generated in the underlayer H is below the allowable value.
There was a limitation on the segment chip length that can be bonded by electron beam welding. For example, when the substrate B and the underlayer H are iron-based and the bond between the abrasive layers D is Ni or Co-based, one segment for the bending stress generated in the underlayer H to be within an allowable range. The maximum length of the tip was about 50 mm. [0012] Such a problem is not limited to the case where the segment chip and the substrate are bonded by laser welding or electron beam welding. This is also a problem that occurs when bonding by sintering or brazing. The problem to be solved in the present invention is to reduce the bending stress generated in the underlying layer in bonding a segment chip having a multilayer structure to a substrate, thereby alleviating the restriction on the length of the segment chip based on the bending stress. Is to do. [0014] Means for Solving the Problems] rotary cutting grindstone of the present invention for solving the above-segmented chips or Li
Ring-shaped segments for sintering with the underlying layer
Multi- layer molding with the underlayer part bonded to the substrate
A rotary cutting grindstone having a structure, wherein a discontinuous portion is formed at one or more locations in a chip longitudinal direction of an underlayer of the multilayer structure segment chip, or at a plurality of locations of an underlayer of a ring-shaped segment having the multilayer structure. The underlayer is divided into a plurality of layers. By forming a discontinuous portion of the underlayer in the chip longitudinal direction, bending stress generated in the underlayer during welding or sintering becomes discontinuous in the chip longitudinal direction. As a result, the concentration of bending stress in the longitudinal direction of the chip can be dispersed, and the maximum bending stress at the dispersed stress concentration portion is about 50% or less of the maximum bending stress when there is no discontinuous portion. FIG. 7 is a view showing a state of generation of bending stress when one discontinuous portion of the underlayer is provided, and schematically shows the bending stress for one segment chip S of the rotary cutting grindstone. Things. By providing the gap G in the underlayer H, the bending generated in the underlayer H when the abrasive layer D and the underlayer H are sintered and cooled, and when the segment chip S is bonded to the substrate B by laser welding. can be distributed to each of the central portion of the shed underlayer H ₁ and H ₂ concentration of stress, the maximum bending stress in the distributed stress concentration sites sigma _max1, sigma _max2 is in the absence of the gap G It is about 50% or less of the maximum bending stress σ _max (see FIG. 8). Since the maximum bending stress can be reduced to about 50% or less by providing only one discontinuous portion of the underlayer, the restriction on the chip length can be relaxed and the discontinuous portion can be reduced. If the number is increased to two or more, the restriction on the chip length can be further relaxed. Since the tip length can be increased, the manufacturing cost of the grindstone can be reduced. If the number of discontinuous portions is further increased, the restriction on the chip length is substantially eliminated, and it is possible to manufacture a rim-type rotary cutting grindstone which was conventionally difficult to manufacture by laser welding or electron beam welding. . That is, a ring-shaped segment having discontinuous portions formed at a plurality of locations in the circumferential direction of the base layer of the multilayered ring-shaped segment is bonded to the substrate by laser welding or electron beam welding, and a rim-type rotary cutting without welding defects. A grindstone can be manufactured. Further, a notch can be formed in the abrasive layer on the side of the underlying layer so as to be continuous with the discontinuous portion of the underlying layer. By forming the notch on the underlayer side of the abrasive layer in this way, it is possible to further reduce the occurrence of bending stress of the underlayer based on the difference between the expansion rate and the shrinkage rate of the underlayer and the abrasive layer. Further, it is possible to effectively cool a portion which is likely to be high in temperature, and to improve the sharpness by improving the discharge of cutting chips during cutting. The applicant of the present invention has disclosed that a concave portion for supplying cooling water is formed substantially at the center of the bonding portion between the segment chip and the substrate in the diamond cutting wheel, as disclosed in Japanese Patent Laid-Open No. 7-1560.
As proposed in Japanese Patent Application Publication No. 69, even in the case of the segment chip having a multilayer structure of the present invention, there is an effect of increasing the discharge of cutting chips by forming a notch on the underlayer side of the abrasive layer. However, simply forming a notch on the underlayer side of the abrasive layer without forming a discontinuous portion in the underlayer can hardly expect the effect of reducing the bending stress of the underlayer, thus forming a discontinuous portion in the underlayer. In addition, by forming a cutout on the underlayer side of the abrasive layer in such a manner as to be continuous with the discontinuous portion of the underlayer, it is possible to further reduce the occurrence of bending stress in the underlayer. The length of the continuous portion when the discontinuous portion is formed in the underlayer, that is, the interval between adjacent discontinuous portions is 10 to 2
5 mm is preferred. If this interval is less than 10 mm,
If the number of discontinuous portions is too large, the strength of the underlayer decreases, and if the interval exceeds 25 mm, the dispersion of the bending stress of the underlayer becomes insufficient, and the reduction of the maximum bending stress becomes insufficient. It is preferable that the size of the discontinuous portion, that is, the gap between adjacent continuous portions is 2 to 10 mm in the longitudinal direction of the chip. When the gap is less than 2 mm, the gap is connected when the base layer is temporarily melted during welding, so that a discontinuous portion is not formed.
If it exceeds 0 mm, the adhesive strength to the substrate will decrease. The shape of the discontinuous portion of the underlayer and the cutout portion of the abrasive layer is such that the corners are rounded in order to eliminate chips remaining in the corners and reduce stress concentration. It is desirable. Such a discontinuous portion of the underlayer and a cutout portion of the abrasive grain layer can be formed as follows. For example, in the case of a segment chip composed of a single-layer abrasive layer and an underlayer, first, the abrasive layer is filled into a mold in the form of powder or green compact, and the pre-divided underlayer is pressed thereon. A segment chip with a discontinuous part formed in the underlayer is manufactured by pressing a punch with a projection formed on the lower surface with a shape corresponding to the shape of the discontinuous part into a mold by filling it in the form of powder. be able to. In the case where the notch is formed on the underlayer side of the abrasive layer so as to be continuous with the discontinuous portion of the underlayer, after filling the divided underlayer, it is desired to form the discontinuous portion of the underlayer and the abrasive layer. Manufacturing a segment chip with a discontinuous part in the base layer and a notch part in the abrasive layer by pressing a punch with a projection with a shape corresponding to the shape of the notch on the lower surface into the mold and molding it. Can be. FIG. 1 is a front view of a cutting whetstone showing an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. The cutting whetstone 10 of the present embodiment is a cutting device in which an abrasive chip layer 11 made of a diamond-based abrasive grain and a metal bond and a Ni-based base layer 12 are bonded to an iron-based substrate 14 by laser welding. It is a whetstone. The dimensions of each part of the cutting whetstone 10 are 405 m outside diameter of the substrate 14.
m, thickness 23 mm, number of segment chips 13 12
The pieces have the same length of 100 mm, the same height of 10 mm, and the same thickness of 3 m. In the cutting whetstone 10 of this embodiment, a gap 12a is provided at the center of the underlayer 12 in the chip longitudinal direction, and the abrasive layer 11 is connected to the gap 12a.
Is provided with a notch 11a. The width of the gap 12a is about 2 m
m, and the height of the notch 11a is about 5 mm. By providing the gap 12a in the underlayer 12, the sintering and cooling of the abrasive layer 11 and the underlayer 12 and the bonding of the segment chip 13 to the substrate 14 by laser welding can be performed with the underlayer 12. The concentration of the generated bending stress can be dispersed in the respective central portions of the divided underlayers 12c and 12d. It is about 50% or less. When there is no gap 12a, the chip length must be 50 mm or less so that the maximum bending stress generated in the underlayer becomes equal to or less than the allowable value. In this embodiment, even if the chip length is set to 100 mm as in this embodiment, the underlayer 1
The maximum bending stress generated in No. 2 is below the allowable value. Further, in the cutting whetstone 10 of the present embodiment, the notch 11a connected to the gap 12a of the underlayer 12 is provided on the underlayer 12 side of the abrasive layer 11, so that the underlayer 12
Layer 12 based on the difference between the expansion and contraction rates of
Generation of bending stress can be further reduced.
Cooling water can be efficiently supplied, a portion that tends to be high in cutting temperature can be effectively cooled, and the cutting chips can be discharged well during cutting to improve sharpness. FIG. 3 is a diagram showing a manufacturing procedure of the segment chip 13 shown in FIG. First, formwork 30 and lower punch 3
1 is filled with 11 m of abrasive layer powder ((a) in the figure). The underlayer 12c, which is divided in advance,
12d is filled in the form of a green compact ((b) in the figure).
Next, an upper punch 3 having a projection 32a formed on the lower surface corresponding to the shape of the notch 11a to be formed on the abrasive grain layer 11 is formed.
2 is pressed into a mold and molded ((c) in the same figure), and sintered to form a gap 12a in the underlayer 12 and the abrasive layer 11
Then, a segment chip 13 having a notch 11a formed therein is manufactured ((d) in the figure). The segment chip 13 is welded to the substrate 14 ((e) in the figure) to complete the cutting wheel 10 shown in FIG. In the above embodiment, the underlayer 12
In this example, two gaps 12a and 12b are provided, and the underlayer 12 is divided into three underlayers 12e, 12f and 12g, as shown in FIG. it can. When two or more gaps are provided, the chip length can be made longer than when one gap is provided.
Here, as shown in the segment chip 13 of FIG.
In the case where the notch is not formed in 1, the shape of the projection on the lower surface of the upper punch 32 may correspond to the shape of the discontinuous portion of the base layer 12 in the manufacturing procedure of FIG. 3. FIG.
As shown in the figure, by applying to the rim type cutting whetstone 20,
The ring-shaped segment 23 can be bonded to the substrate 24 by welding. The gap 12a of the underlayer 12 and the abrasive layer 11
The shape of the notch 11a is desirably a rounded shape in order to eliminate residual chips in the corners and reduce stress concentration. In addition to the shape shown in FIG. ,
It is desirable that the shape is based on a semicircle, an ellipse, or the like as illustrated in FIGS. 6A and 6B. In the case of dry cutting, as shown in FIG.
By inclining the notch 11a rearward with respect to the rotation direction, the chip discharge performance can be further improved. On the other hand, when the output of the machine is high and the impact force applied to the chip is large due to large vibration such as an engine cutter, the chip strength can be increased by not tilting the gap 12a and the notch 11a. ,
The shape is preferably as shown in FIG. According to the present invention, the following effects can be obtained. (1) By forming discontinuous portions in the chip longitudinal direction of the base layer of the segment chip, the concentration of bending stress generated in the base layer during welding or sintering is dispersed to reduce the maximum bending stress. Therefore, the restriction on the chip length can be relaxed, and the manufacturing cost of the grinding wheel can be reduced. (2) By forming a notch on the underlayer side of the abrasive layer in a form continuous with the discontinuous portion of the underlayer,
It is possible to further reduce the occurrence of bending stress in the underlayer, and to effectively cool a portion that easily becomes high in cutting. (3) By further increasing the number of discontinuous portions, it is possible to manufacture a rim-type rotary cutting grindstone, which has conventionally been difficult to manufacture by bonding by laser welding or electron beam welding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a cutting whetstone showing an embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a view showing a manufacturing procedure of the segment chip shown in FIG. 2; FIG. 4 is a partially enlarged view of a cutting grindstone showing another embodiment of the present invention. FIG. 5 is a front view of a cutting whetstone showing still another embodiment of the present invention. FIG. 6 is a partially enlarged view showing another example of the shape of the discontinuous portion of the underlayer and the cutout portion of the abrasive grain layer. FIG. 7 is a schematic diagram showing a state of occurrence of bending stress in an underlayer in the cutting wheel of the present invention. FIG. 8 is a schematic diagram showing a state of occurrence of bending stress in an underlayer in a conventional cutting grindstone. DESCRIPTION OF SYMBOLS 10 Cutting whetstone 11 Abrasive layer 11a Notch 11m Abrasive layer powder 12, 12c-12g Underlayer 12a, 12b Gap 13 Segment chip 14 Substrate 20 Cutting whetstone 23 Segment 24 Substrate 30 Formwork 31 Lower punch 32 Upper punch 32a Projection

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-270077 (JP, A) JP-A-10-100309 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B24D 5/12 B24D 3/00 B24D 5/06 B23K 31/00

Claims (1)

(57) [Claims 1] Rotating cutting of a multilayer structure in which a segment chip or a ring-shaped segment is integrally formed with a base layer provided thereunder by sintering, and the base layer part is adhered to a substrate. A whetstone, the discontinuous portions are formed at one or more locations in the chip longitudinal direction of the underlying layer of the segmented chip having the multilayer structure, or at a plurality of locations of the underlying layer of the ring-shaped segment having the multilayered structure to form the plurality of underlying layers. Divided into individual pieces, and
In the form continuous with the discontinuous part,
A rotary cutting whetstone having a notch formed therein .