JPH06328353A - Grinding method for soft metal - Google Patents

Abstract

PURPOSE:To provide a low cost, highly efficient and quality machining method by grinding using a super abrasive grain wheel in a removing-machining method for soft metal being below HRC specified value such as stainless steel and non-ferrous material or the like. CONSTITUTION:Soft metal being below HRC 35 is ground by a super abrasive grain wheel made of CBN diamond or the like at high speed above 80m/s in wheel circumferential speed. In addition, it is desirable that the grain size of super abrasive grain is 16/18 to 325/400, and a concentration degree is 50 to 250.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the automobile industry, the electric industry,
The present invention relates to a method for removing and processing ferrous materials and non-ferrous materials, which are indispensable in many fields such as the shipbuilding heavy machinery industry, and particularly to provide a highly efficient and high quality new processing method for relatively soft materials of this kind.

[0002]

2. Description of the Related Art Conventionally, non-ferrous materials such as aluminum, aluminum alloys, copper, copper alloys, nickel, nickel alloys, titanium and titanium alloys, and steel materials such as mild steel, soft cast steel,
The removal of soft materials such as stainless steel having an HRC of about 35 or less has been performed by cutting using a cutting tool such as a cutting tool, end mill, or cutter. In rare cases, grinding was performed in order to satisfy the required high processing accuracy. Even in this case, the grindstone used in this case is normal grinding with a silicon carbide type or an alumina type, and diamond or CBN is used. The so-called superabrasive wheel was not used for grinding.

[0003]

The chip processing has always been a problem in the removal processing of these soft metals of HRC 35 or less. That is, chips of metal materials are generally of the flow type based on plastic flow, but in the case of soft metals, the chips themselves are soft and the chips are divided and become continuous flow type chips that are difficult to be miniaturized. easy. A conventional cutting tool is provided with a treatment for dividing and miniaturizing these continuous chips. The most typical one is a cutting edge treatment called a chip breaker. However, recently, the forging and casting technologies, which are the pre-stages of the removal process, have progressed for the parts to be processed, and the machining cost for the removal process has drastically decreased. That is, the machining allowance, which conventionally used to have a radius of 2 to 5 mm, has increased to 1 mm or less. It is difficult to divide and miniaturize such chips of a work material having a small machining allowance even with a chip breaker. Further, it is difficult to cut chips regardless of the machining allowance, such as cutting of narrow and deep grooves. The biggest problem in the cutting of these soft metals is that the above-mentioned chip treatment does not work well, and the machining line is stopped due to chip removal or breakage of the tool cutting edge. In other words, the processing is stopped due to the stop of processing due to the winding of chips around the tool or the work material, the deterioration of the quality of the processing surface, the chatter due to chipping of the tool cutting edge, the surface roughness defect, the dimensional accuracy defect, etc. Reach Due to these problems, it was difficult to automate, unmanned, and improve accuracy in a processing line including cutting.

On the other hand, in the grinding process, since the number of cutting edges is extremely large, the chips are small, and the risk of the machining line being stopped due to tool damage due to the chips is extremely low. Therefore, it is an optimum removal processing method for automation and unmanned processing. However, with conventional grinding stones that use alumina-based abrasive grains or silicon carbide-based abrasive grains, which are currently used in the grinding of soft metals, the grinding stone's processing capacity is low, so it cannot be processed with efficiency comparable to that of cutting. There was a problem in processing efficiency. For example, compare the maximum working capacity of a simple round bar of mild steel. The processing efficiency can be expressed by the material removal rate Z (mm ³ / min). That is, material removal rate Z = cut depth a
(Mm) x workpiece speed Vw (mm / min) x feed amount per revolution of the workpiece f (mm / rev). The processing conditions for cutting with a cemented carbide bit are a = 2, Vw =
With 100000 and f = 0.5, Z = 100000. When grinding with an alumina grindstone, a = 0.02, Vw = 15000, f = 10,
Z = 3000, that is, the grinding process was only about 1/30 the efficiency of the cutting process, and it was difficult to substitute the cutting process for the grinding process using the conventional grindstone. In order to improve the efficiency of the grinding process, a method of using a superabrasive grain wheel such as a diamond wheel or a CBN wheel having a significantly excellent grinding ability as a grindstone can be considered. However, in the conventional grinding technology, when soft metal is ground with a super-abrasive grain wheel, when trying to increase the machining efficiency, clogging occurs and the required machining accuracy and quality cannot be obtained, or even with a low machining efficiency It has been impossible to apply the superabrasive wheel to the grinding of soft metal, because it cannot be economically processed due to its large wear.

[0005]

[Means for Solving the Problems] In order to process soft metal with high efficiency and high precision on an automatic processing line, it is necessary to develop a grinding method having a processing efficiency comparable to that of cutting. In order to achieve these objects in the processing of soft metals having a hardness of HRC 35 or less, a technique for using a superabrasive wheel, particularly a CBN wheel, at a wheel peripheral speed of 80 m / s or more was developed. The CBN wheel uses CBN abrasive grains with high hardness, strength and thermal stability as abrasive grains, so it has good grinding performance at high speed machining and has a high strength wheel structure that far exceeds 80 m / s. It has the characteristic that it can be used safely even in the high circumferential speed range. By grinding with a CBN wheel having a wheel peripheral speed of 80 m / s or more, it is possible to perform highly accurate grinding with a machining efficiency comparable to that of cutting. Further, since high-performance CBN abrasive grains are used as cutting edges at high speed, wheel wear is extremely small and a sufficiently long wheel life can be obtained.

FIG. 1 shows the results of grinding tests of carbon mild steel (S25C, HRC22) at various wheel peripheral speeds with a metal bond CBN wheel having a grain size of # 60/80, a concentration of 100, a diameter of 250 mm and a width of 5 mm. It is shown. Machining capacity is expressed by specific material removal rate Z '(material removal rate per tool unit) = depth of cut a (mm) x workpiece speed Vw (mm / s),
From the figure, it is clear that the relationship between the wheel peripheral speed and the processing capacity that allows good processing without squeezing becomes surprisingly large when the wheel peripheral speed is 80 m / s or more. The grinding method used in the above grinding test was cylindrical plunge grinding, and the grinding fluid used was a 10% emulsion solution.

FIG. 2 shows the results of a comparative test of the relationship between the peripheral speed of the CBN wheel and the grinding ratio indicating the life of the wheel. As shown in the drawing, a high grinding ratio can be obtained at a wheel peripheral speed of 80 m / s or more. I understand. The conditions of this test are as follows. CBN wheel (diameter 150 mm, width 1.5 mm, grain size # 80/100, bond electrodeposition) Work material (SUJ2, HRC2
8) Grinding method (plane groove grinding) Grinding liquid (emulsion 15%
Solution) Specific material removal rate Z'is as follows. Wheel peripheral speed 20 to 60 m / s: 5 mm ³ / mm ・ s Wheel peripheral speed 80 m / s or more: 100 mm ³ / mm ・ s

[0008]

As described above, the reason why the CBN wheel, which cannot be used in the conventional grinding technique, can be used by increasing the speed is as follows. Grinding caused by this processing is because soft metal is processed by a conventional grinding technique using a CBN wheel, and the result is that the desired processing result is not obtained and the wheel wear becomes extremely large. This is because a relatively long flow type chip cannot be discharged as a process, and the bond material is scraped off by this chip. By the way, it is generally known that the amount of grinding heat generated increases as the wheel peripheral speed increases. Particularly, as in the present invention, the amount of heat generation is extremely large in the region of extremely high peripheral speed. The generated grinding heat is distributed to chips, workpieces, grinding fluid, and wheels.
It is said that the rate of inflow into the chips is the largest. CBN
It is considered that the rate of inflow into the chips becomes extremely large in the increase in grinding heat in high-speed grinding of 80 m / s or more using a wheel. It can be inferred from the fact that the surface quality of the processed material processed by high speed grinding was extremely good and no heat damage was received. That is, the long, soft chips generated at high speed become high temperature due to the inflowing heat. When it is rapidly cooled by the grinding fluid, it becomes extremely brittle, and the chips tend to be finely divided. Therefore, it is considered that the chips are easily discharged and neither clogging nor abrasion of the pond material occurs, that is, good workability and long wheel life can be obtained.

[0009]

【Example】

(Example 1) The machining allowance of the geometry shown in FIG. 3 is 0.
A 3 mm HRC28 bearing steel forging was ground with a vitrified CBN wheel A in one pass under the following conditions. The processing cycle time (loading to loading) at this time is 24 s, which is comparable to cutting processing,
The obtained processing precision was excellent with a surface roughness of 1.6 μmRz, roundness and cylindricity of 1 μm.

Grinding conditions and grinding results of Example 1 Wheel: Abrasive grain CBN Grain size # 80/100 Concentration degree 200 Bond Vitrified bond Work material: SUJ2, HRC28, machining allowance φ0.3 mm Processing condition: Wheel peripheral speed 140 m / s Workpiece material Rotation speed 3000rpm Depth of cut φ0.3mm Grinding fluid Emulsion, 10% solution Processing result: Cycle time 24s Surface roughness 1.6μm Rz Roundness 1μm Cylindricity 1μm

Table 1 shows the material removal rate Z indicating the processing efficiency and the specific material removal rate Z'indicating the processing capacity in this embodiment.
As shown in, the conventional processing method can be sufficiently countered.

[0012]

[Table 1]

(Embodiment 2) Carbon steel (S48C) of HRC23 having a diameter and a machining allowance of 0.5 mm shown in FIG.
Was ground with a metal bond CBN wheel B under the following conditions. The processing accuracy and the like are excellent as follows, and the processing efficiency and the like are shown in Table 2, which is superior to the conventional one.

Grinding conditions and results in Example 2 Wheel: Abrasive grain CBN Grain size # 60/80 Concentration 150 bond Metal bond Workpiece material: S48C, HRC23, machining allowance φ0.5 mm Processing condition: Wheel peripheral speed 160 m / s Material rotation speed 1400 rpm Depth of cut φ0.5 mm Grinding fluid emulsion, 10% solution Processing result: Cycle time 43 s Surface roughness 3 μm Rz Roundness 1 μm

[0015]

[Table 2]

Example 3 Table 3 shows the cutting ratio when Ti-6Al-4V, which is a typical titanium alloy, is processed with a diamond wheel. The cutting ratio was 9 to 31 at the conventional wheel peripheral speed (20 to 40 m / s), but by setting the wheel peripheral speed to 100 m / s, a cutting ratio of 290 and a cutting ratio of 9 to 32 times can be obtained, which is sufficient. It can be processed at an economical cost. That is, in the cutting of non-ferrous metal, the same processing result can be obtained by using the diamond wheel.

Cutting Conditions in Example 3 Wheel: Abrasive Grain Diamond Grain # 140/170 Concentration 100 Bond Resin Bond Work Material: Ti-6Al-4V, HRC33 Machining Method: Flat Traverse Grinding Machining Condition: Wheel peripheral speed 100 m / S table speed 12m / min depth of cut 0.01mm / pass grinding fluid emulsion, 5% solution

[0018]

[Table 3]

As the superabrasive wheel used in the present invention,
It is desirable to use those having a grain size of # 16/18 to 325/400, a concentration of 50 to 250, and a metal bond, vitrified bond, electrodeposition, or resin bond. In the conventional superabrasive wheel, the grain size is mesh size # 30/40 to 325 /
A wide range of 400 and micron size of 36.54 to 0.1 / 2 .mu.m and a concentration of 25 to 230 have been used. As described above, this processing method involves high-efficiency processing, and does not require the micron size used for obtaining good surface roughness. If the micron size is used, it will not be possible to store chips, and high efficiency machining will not be possible, and wheel wear will increase and the grinding ratio will be extremely low. Conventionally not used due to rough surface and increased grinding resistance # 16 / 18-20 / 30
The use of this technology for the coarse particles reduces the grinding resistance,
It becomes possible by improving the surface roughness by reducing the cutting depth of the abrasive grains. If the degree of concentration is less than 50, the stress applied to one abrasive grain becomes too large, causing large-scale abrasive grain wear. As a result, the bonding material comes into contact with the work material, and the work cannot be satisfactorily processed due to an increase in grinding resistance and the occurrence of grinding burn of the work material.

[0020]

[Effect] As described above, according to the present invention, the wheel using the superabrasive grains enables the HRC at a high peripheral speed of 80 m / s or more.
It is possible to grind soft metals such as 35 or less of mild steel, mild cast steel, stainless steel, and non-ferrous metal materials. This grinding is a new removal processing method for this kind of material, and has the features of higher efficiency, higher accuracy, less wheel wear, and lower cost than conventional methods. Therefore, in many fields such as the automobile industry, the electrical industry, the shipbuilding heavy machinery industry, etc., it promotes automation of unmanned processing of the material parts of this kind and contributes to the development of the industry.

[Brief description of drawings]

FIG. 1 is a view showing a result of testing a relationship between a peripheral speed of a CBN wheel and a specific material removal rate.

FIG. 2 is a view showing a result of testing a relationship between a peripheral speed of a CBN wheel and a grinding ratio.

3] Shape, size and CBN of work material in Example 1.
The schematic diagram which shows the position of a wheel.

4] Shape and size of work material and CBN in Example 2 [FIG.
The schematic diagram which shows the position of a wheel.

[Explanation of symbols]

 The black circles indicate points where good processing was possible without clogging. White circles indicate points that could not be processed due to clogging. A: Shows a vitrified bond CBN wheel. B: Metal bond CBN wheel is shown.

Claims (3)

[Claims] 1. A soft abrasive grain of 80 m
A grinding method of a soft metal, characterized by grinding at a wheel peripheral speed of not less than / s. 2. The method for grinding a soft metal according to claim 1, wherein the superabrasive grains are diamond or CBN, and the soft metal is a steel material or a non-ferrous material having a hardness of HRC 35 or less. 3. A metal bond, a vitrified bond,
Super-abrasive grains bonded by either electrodeposition or resin bond are
The method of grinding a soft metal according to claim 1 or 2, wherein the grain size is 16/18 to 325/400 and the degree of concentration is 50 to 250.