JPH0212702B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a resin bonded CBN grindstone. [Background of the invention] CBN is an abbreviation for cubic boron nitride, which is produced using ultra-high pressure and high temperature technology similar to diamond synthesis.
It is used as an abrasive grain because it has a hardness second only to diamond. Its advantages are demonstrated in grinding steel, which is extremely difficult to do with diamond. Compared to whetstones with aluminum oxide or silicon carbide abrasive grains that are commonly used for grinding steel (hereinafter referred to as ordinary whetstones), CBN whetstones exhibit a grinding ratio of several tens to hundreds of times, and sometimes over 1,000 times. The grinding ratio is an index for measuring the life of the grinding wheel, and is the ratio of volume removed/volume consumed by the grinding wheel. The amount removed is the amount removed as chips from the workpiece, and means the amount of processing. However, CBN grinding wheels are also several tens to hundreds of times more expensive per unit consumption volume than normal grinding wheels, so even if the grinding ratio of CBN grinding wheels is high, the grinding wheel consumption costs may not necessarily be advantageous compared to normal grinding wheels. . CBN grinding wheels are often used because the overall grinding cost is superior to normal grinding wheels because even though the grinding wheel consumption costs are slightly higher, work efficiency and other factors are superior, but this advantage does not hold and CBN grinding wheels are not economical. In many cases, it is not as good as a regular whetstone. CBN grinding wheels have high expectations due to their performance in grinding steel, but the reason why they are not always satisfactory is due to economics, especially the cost of grinding the grinding wheels. To solve this problem and meet the expectations of the machining industry, grinding wheel consumption costs must be reduced. CBN
If it is not possible to significantly reduce the price of grinding wheels, the only option is to increase the grinding ratio. Of course, the grinding ratio is one of the most important performances of a grinding wheel, so many improvements have been made to CBN grinding wheels to date, and the grinding ratio has gradually improved, but even with the current highest level of grinding ratio, However, the economic efficiency remains as described above. In addition to the grinding ratio, cutting quality is also important for the performance of a whetstone. Cutting quality is a factor that affects work efficiency from the perspective of grinding work. In general, the lifespan of a whetstone competes with its sharpness; a whetstone with a long lifespan tends to have a poor cutting quality, and a whetstone with a good sharpness tends to have a short lifespan. It is possible to create a long-life whetstone by reducing the sharpness, but such CBN whetstones have no value. What is expected is a whetstone that cuts well and has a long lifespan. [Prior Art] CBN grinding wheels include those using resin bond, metal bond, and various other bonds, but resin bond grinding wheels are the most commonly used because they are suitable for a wide range of purposes. Until now, the resin bond for CBN grinding wheels has been made by blending a resin selected from phenolic resin or polyimide resin with one or more fillers from silicon carbide, aluminum oxide, copper, silver, graphite, etc. . It is known that the properties of resin molded articles can be adjusted by using fillers. In grindstones as well, fillers affect the characteristics of the bond and, ultimately, the performance of the grindstone. Silicon carbide and aluminum oxide help the grinding action of CBN abrasive grains as auxiliary abrasive grains, but they are said to be even more effective in strengthening the bond. This is because the flow-shaped chips produced when grinding steel with a CBN grinding wheel severely corrode soft resin bonds. Metals with high thermal conductivity, such as copper and silver, dissipate grinding heat and suppress the temperature rise at the grinding point. Graphite acts as a lubricant, smoothing out the grinding action and reducing frictional heat. It is also said that graphite quickly wears away, leaving behind pores that act as effectively as the pores in a normal grindstone. The above should be interpreted as a tentative explanation; in reality, even if the filler is the same material, it is determined empirically by selecting the powder characteristics and particle size and adjusting the blending amount. [Problems to be Solved by the Invention] An object of the present invention is to provide a resin-bonded CBN grindstone with a high grinding ratio and excellent cutting quality. [Means for Solving the Problems] The means of the present invention uses metallic tungsten powder as a filler for resin bond in an amount of 10% to 35% by volume of the bond.
This is due to the capacity percentage. The effect of this filler cannot be understood from the above description and is therefore not used heretofore. [Example] Practical test examples are shown below. (1) Test whetstone specifications and dimensions Abrasive grain Nickel-coated CBN Abrasive grain size 170/200 US mesh Outlet 100 Resin Listed in the table Filler〃 Filling amount〃 Diameter 175mm Thickness 6mm (2) Grinding test conditions Grinding style Wet surface grinding Specification machine Surface grinder, PSG-5EV type manufactured by Okamoto Machine Tools Grinding wheel Rotation speed 2800 rpm (Grinding wheel circumferential speed 1540 m/min) Table feed speed 15 m/min Back and forth feed 1 mm/pass Depth of cut 0.05 mm Grinding fluid Water-soluble 2 types (3) Grinding material Type JIS SKH−51 Dimensions Rectangular shape with a width of 100 mm and a length of 150 mm Hardness HRC 61 (4) Results

[Table] Under the above conditions, the grinding ratio is
Over 200 whetstones were considered to be CBN whetstones with excellent longevity. The test results are as described above, and the effect of the tungsten filler is clear, with the grinding ratio clearly increasing compared to conventional fillers, and with a large amount of filler, it is about twice as high. Although the grinding resistance increased slightly, the deterioration in cutting quality was not observed to the extent that it affected work efficiency. On the other hand, the grinding ratio of wheels with a small amount of tungsten filling cannot be said to be high compared to the conventional example, and in particular, the grinding ratios are reversed between grinding wheels 9 and 10, but grinding wheel number 10 has high grinding resistance. Grinding burn occurred on the workpiece partway through. On the other hand, grinding wheel number 9 had a low grinding resistance and was effective in allowing continuous grinding to be performed normally, and the grinding ratio exceeded the target value of 200. As the tungsten filler, metallic tungsten powder with a particle size of 1 to 10 microns is used. The tungsten powder used in the test wheels had a nominal particle size of 9 microns. As the grain size decreases, the grinding ratio decreases, and the grinding ratio decreases as the grain size decreases.
The grinding ratio after changing the grain size is

〔Effect of the invention〕

According to the present invention, it has been proven through many tests that the grinding ratio is improved to about twice that of the conventional method, and the cutting quality is hardly reduced.

Claims (1)

[Claims] 1. A resin-bonded CBN grindstone, characterized in that 10% to 35% by volume of the bond is filled with metallic tungsten powder as a resin-bond filler.