JPH05169434A - Cutting method with wire saw - Google Patents

Abstract

(57) [Summary] [Object] To provide a cutting method capable of manufacturing an ultra-hard material typified by high-purity alumina with a wire saw at high efficiency, high accuracy, and low cost. [Construction] While moving a wire row 5 stretched at a predetermined pitch in one direction, a work 10 is lifted from immediately below the wire row. An abrasive liquid containing boron carbide abrasive grains is supplied to the contact portion between the wire row 5 and the work 10 to cut the workpiece.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting brittle material having high hardness with a wire saw using loose abrasive grains.

[0002]

2. Description of the Related Art As an apparatus for cutting a block-shaped hard material into a thin plate-shaped product, there are an inner peripheral blade saw, an outer peripheral blade saw, a blade saw, a wire saw, and the like.
The latter two are cut with loose abrasive grains. The inner blade saw is a plate-shaped product in which a blade with diamond abrasive grains fixed to the inner periphery of a thin donut-shaped metal disk is rotated at high speed and the work set at the center is moved in the radial direction of the blade. It is a method of cutting each one. Since the blade applies tension from the outside, the thickness of the blade can be reduced, so that the loss of material due to cutting is small. On the other hand, the outer peripheral blade saw is a thin donut-shaped metal disk with a blade fixed to the outer periphery of which diamond abrasive grains are fixed to the shaft at predetermined intervals, and is rotated at a high speed to cut into the workpiece, and many products are cut at once. Is a method of cutting. In the case of this peripheral blade saw, the diameter of the blade cannot be increased from the viewpoint of the rigidity of the blade, and therefore it is suitable for cutting small-sized products. The blade saw is a straight blade made of tool steel, which is tensioned and set at a predetermined pitch, and is reciprocated while applying a working fluid of abrasive grain mixture to this, and at the same time, the workpiece is moved upwards to produce many products at once. It is a method of cutting. This blade saw is inexpensive in terms of equipment and can cut even a large-area product if there is no time limit. A wire saw is a working fluid that mixes abrasive grains in the contact area between a workpiece and a wire row while reciprocating or running in one direction a wire row formed by winding a wire fed from a reel around a plurality of groove rollers at a predetermined pitch. It is a method of cutting while feeding, and winding the wire on another reel. In the case of the wire saw, since a wire having a small diameter can be used, the loss of the material due to the cutting can be minimized as compared with the above cutting methods.

The above-mentioned four types of cutting devices are properly used depending on the material and size of the material (work) to be cut and the required cutting accuracy. For example, an inner blade saw or blade saw for silicon, an inner blade saw or blade saw for quartz, a blade saw or wire saw for quartz, and an outer blade saw or blade saw for glass are generally used.

[0004]

Needless to say, the higher the hardness of the material to be cut, the more difficult the cutting becomes. That is, in the case of high hardness material to be cut,
In the inner peripheral blade saw and the outer peripheral blade saw, the diamond abrasive grains adhered to the blade are worn out so much that the number of dressings increases, and the blade must be replaced frequently. Moreover, since the cutting speed must be slowed, the cutting efficiency is remarkably reduced. In the case of a blade saw, the blade itself is severely worn, the thickness accuracy of the product is significantly deteriorated, the durability of the blade is reduced, and it becomes necessary to replace the blade during cutting, and the cutting efficiency is also significantly reduced. In the wire saw, the grinding force acting on the wire becomes large and the wire is easily broken, and the time required for cutting becomes abnormally long.

Under the circumstances described above, it is necessary to rely on surface grinding and polishing for a material having extremely high hardness, which is difficult to cut a material block into a thin plate-like product by an industrially applicable method. I don't get it. That is, for example, a method in which a high hardness ceramic material is sintered to a thickness as close as possible to a product, and the product is finished by grinding and polishing is adopted. Further, a method of cutting artificial sapphire or the like into a product having a thickness considerably larger than that of the product without considering the thickness accuracy and the cutting cost, and grinding and polishing the product to finish the product is adopted.

However, in the case of a ceramic material having a high hardness, it is difficult to manufacture a thin material with high flatness by sintering. Therefore, when the product thickness is considerably thinner than the sinterable thickness, grinding is performed. Also, there is a problem of material loss due to polishing, that is, reduction in yield and cost. Further, since the products are sintered one by one, the production efficiency of the raw materials also decreases. Further, in the case of artificial sapphire or the like, in addition to the cutting cost, it is difficult to grind and polish a cut product that is inferior in accuracy, so that the man-hours for grinding and polishing are further increased.

On the other hand, recently, high-hardness ceramic materials having excellent wear resistance have been increasing in demand as electronic parts or mechanical parts, and high-hardness crystal materials such as sapphire as optical parts or parts in watches and the like. However, there is an increasing demand for industrial means for accurately cutting these thinly.

In view of the above situation, the present invention provides a method for cutting a high hardness ceramic material having excellent wear resistance and a high hardness crystal material such as sapphire with an existing wire saw in a thin thickness with high accuracy and at low cost. It is a proposal.

The gist of the present invention is to run a wire row stretched at a predetermined pitch in one direction, raise the material to be cut from immediately below the wire row, and grind the contact portion between the wire row and the material to be cut. In a one-way traveling type wire saw that supplies and cuts a working fluid containing grains, as the working fluid, an abrasive liquid containing boron carbide abrasive grains is used, and the running speed of the wire is 400 to 800
m / min, the particle size of boron carbide abrasive grains is 10 to 70 μm
m, and the specific gravity of the working fluid is 1.2 to 1.8 gf / cm ³ .

[0010]

In the present invention, the target cutting method is limited to the one-way traveling type wire saw for the following two reasons. In order to grind and cut a high hardness material with free abrasive grains, it is necessary to give a large kinetic energy to the abrasive grains to scrape off the surface of the work cut, and a one-way traveling type that can easily increase the wire speed is preferable. In the reciprocating traveling type, since the speed becomes zero when the traveling direction of the wire is reversed, the average speed of the wire cannot be made higher than that in the one-way traveling type. It is necessary to suppress wear of the wire due to sliding with the work piece through the abrasive liquid as much as possible.When focusing on one point on the wire, the sliding distance of the one-way traveling type is better than that of the reciprocating traveling type. Much smaller.

Next, the reason why the abrasive liquid containing boron carbide abrasive grains is used as the working liquid in the one-way traveling wire saw will be described. Usually, the abrasive liquid for cutting the brittle material is prepared by mixing abrasive grains with an oil such as lapping oil or a liquid such as water containing an appropriate additive. As free abrasive grains for blade saws and wire saws, silicon carbide, which has versatility as abrasive grains for lapping, is most widely used. Also in the one-way traveling wire saw, the silicon carbide abrasive grains can be sufficiently applied to materials having a Knoop hardness of about Hv = 400 to 1000 such as silicon, quartz, glass, and quartz. In addition, Knoop hardness of ceramics is H
Alumina or silicon nitride having a purity of 92% with v = 1300 to 1500 has a particle size of silicon carbide abrasive grains of 20 to 40 μm and a wire speed of 400 m / min or more enables efficient cutting. Also has a good flatness.

However, the Knoop hardness is Hv = 150.
For 09.7 to 9700% pure alumina,
It is necessary to reduce the cutting speed to about 0.1 mm per minute, and unless the size is small, it is difficult to cut with practical efficiency. Furthermore, the Knoop hardness is Hv = 1900 to 20
00 sapphire and Knoop hardness Hv = 2100-2
For the 300 titanium carbide / alumina composite sintered material, even if the cutting speed was reduced to about 0.1 mm per minute, the cutting resistance was large and the wire trajectory was not stable.
Rippling occurs on the cut surface. That is, in the brittle material category, as the hardness of the material to be cut increases, the wire saw cutting with the silicon carbide abrasive grains tends to become difficult. Since the Knoop hardness Hv of the silicon carbide abrasive grains is about 2500, practical cutting is possible if the hardness of the material to be cut is about 60% or less of the hardness of the abrasive grains, but if the hardness is higher than that, it can be gradually cut. The cutting efficiency is lowered, and it becomes difficult to cut a material having a hardness of 80% or more of the hardness of the abrasive grains.

By the way, in cutting with loose abrasive grains, it is necessary to consider the crushing strength of the abrasive grains in addition to the hardness of the abrasive grains. In other words, the abrasive grains being cut by the wire saw scrape the work while being pinched between the wire and the work and receiving pressure and being crushed. .. When cutting a material having a high hardness, it is natural that the crushing of the abrasive grains is likely to occur, and it is necessary to use the abrasive grains having high crushing strength.

Therefore, a material having a high hardness and difficult to cut with silicon carbide abrasive grains, specifically, a Knoop hardness of Hv = 170.
Various experiments have been conducted on abrasive grains for efficiently and accurately cutting hard materials of 0 or more with a one-way traveling wire saw.
As a result of repeated studies, it was found that boron carbide (B ₄ C), which is a boron-based compound, is an abrasive grain that satisfies hardness and crush strength. By the way, Knoop hardness Hv of boron carbide is about 2800 and crush strength is about 200 kg.
/ Cm ² . In particular, the crush strength is about four times that of silicon carbide abrasive grains. The particle size of this boron carbide abrasive grain is 10 to 70.
The reason for limiting to μm is that if the particle size is 10 μm or less, the cutting efficiency is low and the flatness of the cut surface is difficult to obtain.
This is because if the particle size is more than μm, it tends to precipitate when mixed with a liquid, and it becomes difficult to supply it as a slurry. Also, to that the specific gravity of boron carbide abrasive liquid and 1.2~1.8kg / cm ³ is decreased cutting efficiency is less than 1.2 kg / cm ^3, viscosity exceeds the other 1.8 kg / cm ³ This is because the wire is too large to be stably supplied onto the wire array. The running speed of the wire is preferably as high as possible in order to improve the cutting efficiency, but if it becomes extremely fast, the abrasive liquid will be shaken off from the wire row, so 800 m / min was set as a practical upper limit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing an example of a cutting process part of a one-way traveling type wire saw.
4 is a wire, 5 is a wire row, 6 is a working fluid supply nozzle, 7
Is a work lifting base, 8 is a base, 9 is a dummy plate, and 10 is a work.

That is, one wire 4 is wound around a large number of grooves engraved on the outer periphery of three multi-groove rollers 1, 2 and 3 rotatably held to form a wire row 5 of a predetermined pitch. At least one multi-groove roller that is formed is driven to rotate the wire row 5 in one direction, and the boron carbide abrasive liquid supplied onto the wire row 5 from the machining liquid supply nozzle 6 on the entry side of the workpiece 10. At 11, the work 10 is ground and cut as the wire row travels. The work 10 is adhered to a dummy plate 9 made of carbon, ceramics, glass or the like, and the dummy plate 9 is fixed to a base 8 which is detachably fixed to the work lifting table 7 by means such as adhesion. Less than,
An example in which the method of the present invention is applied to the one-way traveling type wire saw having the above-mentioned structure to cut a high hardness material will be described.

Example 1 Diameter 40 mm, length 100 mm, Knoop hardness Hv196
0 sapphire was set on the one-way traveling wire saw in Fig. 1, and a wire row in which a 0.18 mm diameter piano wire was stretched at a 1.4 mm pitch was run in one direction at a speed of 600 mm / min. Particle size 20-60 on the wire
A diameter of 40 m was obtained by mixing boron carbide abrasive grains of μm with lapping oil and raising the work at a speed of 0.3 mm / min while flowing down a polishing liquid adjusted to a specific gravity of 1.30.
70 sapphire discs each having a thickness of 1.1 mm and a thickness of 1.1 mm were simultaneously cut. As a result, the required cutting time was 2.5 hours including the cut to the dummy plate under the work. The thickness accuracy was ± 15 μm, and the flatness of the cut surface was 10 μm, which were extremely good. On the other hand, when using the same material with the same wire saw and silicon carbide abrasive grains with an average grain size of 30 μm, it takes 8 hours to cut, and the thickness accuracy is extremely poor at ± 100 μm, and the cut surface has A waviness with a height difference of up to 200 μm was confirmed.

Example 2 50 mm × 50 mm × 15.4 mm, Knoop hardness Hv2
A 50 mm x 50 mm x 90 mm material consisting of 6 composite sintered materials of 200 titanium carbide and alumina was set in the one-way traveling wire saw of Fig. 1 and the diameter was 0.2 m.
A m wire of a piano wire stretched at a pitch of 2.2 mm is run at a speed of 800 mm / min, and boron carbide abrasive grains having a particle size of 30 to 70 μm are mixed with lapping oil on the wire line on the work entry side. , 50 mm × 50 mm × 1.9 mm thick plate 42 by raising the work at a speed of 0.4 mm / min while flowing down an abrasive liquid adjusted to a specific gravity of 1.50.
The sheets were cut at the same time. As a result, the required cutting time was 2.5 hours including the cut to the dummy plate under the work. The thickness accuracy is ± 20 μm, and the flatness of the cut surface is 1.
It was 0 μm, which was extremely good. On the other hand, when using the same material with the same wire saw and silicon carbide abrasive grains having an average particle size of 30 μm, it takes 10 hours to cut, and the thickness accuracy is extremely poor at ± 150 μm, and the cut surface has ~ 20
A waviness with a height difference of 0 μm was confirmed.

Example 3 70 mm × 20 mm × 150 mm, Knoop hardness Hv70
70mm x 1 by stacking 09.7% pure alumina of 0
A block-shaped material of 00 mm × 150 mm is set on the one-way traveling type wire saw of FIG.
Run at a speed of m / min, and on the wire row on the work entry side,
Boron carbide abrasive grains having a particle diameter of 10 to 40 μm are mixed with an aqueous grinding liquid, and the work liquid is raised at a speed of 0.3 mm / min while flowing down the grinding liquid adjusted to have a specific gravity of 1.70.
1000 sheets of 0 mm x 70 mm x 0.45 mm thickness were cut at the same time. As a result, the time required for cutting was 6 hours including the cutting to the dummy plate under the laminated work. Also,
Thickness accuracy is ± 10μm, and cut surface flatness is 15μm.
It was extremely good. On the other hand, when the same material was used with the same wire saw and the silicon carbide abrasive grains having an average particle diameter of 30 μm were used, the cutting accuracy was the same, but the cutting took 16 hours.

In all of the above three examples, the wear of the wire due to the use of the boron carbide abrasive grains was extremely slight, and the wire could be continuously used 10 to 12 times.

As described above, according to the present invention, the silicon carbide abrasive grains which are widely used in the conventional wire saws require a very long time for cutting, and a material of high hardness which cannot ensure the cutting accuracy. Even in this case, a great effect that cutting can be performed with high efficiency and high accuracy and at low cost is achieved. Therefore, the industrial value of this invention, which enables these thin products to be manufactured by cutting with a wire saw, is extremely high, as the applications of high hardness materials are further expanded due to improved wear resistance.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a cutting step part of a one-way traveling wire saw to which the present invention is applied.

[Explanation of symbols]

 1, 2 and 3 multi-groove roller 4 wire 5 wire row 6 machining liquid supply nozzle 7 work push-up base 8 base 9 dummy plate 10 work 11 abrasive liquid

Claims (2)

[Claims] 1. A process in which a wire row stretched at a predetermined pitch is run in one direction, a material to be cut is raised from directly below the wire row, and a contact portion between the wire row and the material to be cut contains abrasive grains. In a one-way traveling type wire saw that supplies and cuts a liquid, a cutting method using a wire saw, wherein a grinding liquid containing boron carbide abrasive grains is used as the working liquid. 2. The running speed of the wire is 400 to 800 m /
The method for cutting with a wire saw according to claim 1, wherein the boron carbide abrasive grains have a particle size of 10 to 70 μm, and the working fluid has a specific gravity of 1.2 to 1.8 gf / cm ³ .