JPH0122111B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to lap tools. Wrapping is a method for increasing the flatness of a pre-processed workpiece surface and creating a smooth finished surface with high dimensional accuracy. Specifically, the following methods have been used in combination. B. A method in which a lapping agent made of a mixture of fine abrasive grains (free abrasive grains) and oil is interposed between a lap made of a softer material than the workpiece and the workpiece, and the lap is caused to slide relative to the surface of the workpiece. A method in which the abrasive grains are fixed by pushing the abrasive grains into the surface of the lap, making use of the difference in hardness between the lap and the abrasive, and the surface of the workpiece and the lap are made to slide. However, with method (a), since the abrasive grains are loose from the lap, they tend to flow out together with the oil, which increases the consumption of expensive abrasive grains, and because the abrasive grains roll and embed randomly into the machined surface, Each of these disadvantages is that it is difficult to obtain a good finished surface, such as the surface becoming satin-like, and that the durability of the lap surface flatness is poor due to the large amount of wear on the lap, requiring frequent corrections. In addition, with method (b), the work is extremely complicated as it is necessary to push fine abrasive grains into the lap surface one by one, and it is difficult to ensure that the abrasive grains are fixed securely, so the abrasive grains may come off during use. The problem is that it tends to cause scratches on the processed surface. Because of the above, conventional methods require a very long time and a large amount of abrasive grains in order to obtain a finished surface with high precision. The present invention was developed through repeated research in light of the above-mentioned circumstances, and is capable of efficiently finishing the surfaces of various materials, including metal materials, with a beautiful luster in a short time, and does not require the consumption of abrasive grains. The object is to provide a new lapping tool that can minimize lapping and prolong the life of the tool. To achieve this objective, the present invention breaks away from the common sense of conventional lapping tools in which abrasive grains are considered to be completely separate or independent elements from the surface plate (lap), and the abrasive grains are integrated with the surface plate component. This is a lap tool with a special structure in which abrasive grains are fixed from the beginning and additional abrasive grains are built-in. That is, the characteristics of the present invention are that abrasive grains are mixed with cast iron powder at a ratio of 15 wt% or less, pressure molded at a molding pressure of 6 to 8 tons/ ^cm2 , and sintered at a sintering temperature of 1125 to 1150°C. The abrasive grains are bonded and fixed to the welded cast iron grains that make up the sintered cast iron base, and the abrasive grains are also dispersed and buried in the cast iron base below the surface layer. . Embodiments of the present invention will be described below with reference to the accompanying drawings. Fig. 1 shows an example of a lap tool according to the present invention, and 1 in the figure is a composite lap, which is a sintered composite made by mixing cast iron powder with a predetermined amount of abrasive (abrasive grains) and sintering it. It is composed of a body, and grooves 2 are formed vertically and horizontally at predetermined intervals. FIG. 2 shows a partial cross section of the composite lap 1, in which the abrasive grains 3 are integrally fixed to the sintered cast iron matrix 4 in a substantially uniform distribution, and each abrasive grain 3 in the surface layer
As shown in FIG. 2a, the upper part slightly protrudes from the surface 41 of the cast iron matrix, and the lower part is fixed integrally with welded cast iron powder grains 42, 42 constituting the cast iron matrix. Abrasive grains 3, which will become cutting edges in the future, are evenly distributed and buried in the part below the surface layer of the cast iron base. The composite wrap 1 may be constructed entirely of one piece, but in this embodiment, a plurality of wrap segments 5 having the structure described above are arranged and adhered on a disk 6 to obtain the required diameter. ing. Figures 3a and 3b are enlarged views of the surface of the lap tool according to the present invention. Figure 3a shows the case where abrasive grains with a large grain size are used, and Figure 3b shows the case where abrasive grains with a small grain size are used. This is the case. When abrasive grains with a large grain size are used, the abrasive grains are apparently uniformly distributed regardless of the cast iron powder grain boundaries, and the cast iron powders are in close contact with each other, resulting in high strength. On the other hand, when the abrasive grain size is small, the abrasive grains tend to be distributed along the boundaries of the cast iron powder. In this case, the mechanical strength is lower than in the former case, but the boundary becomes a hole where the lap fluid accumulates, and
It is effective in terms of the functionality of the lap tool because it provides a space for the separated abrasive grains to stay. from these things,
By appropriately selecting the grain size of the abrasive grains, it is possible to obtain a composite lap with good mechanical properties and good lap function. The abrasive grains are white alundum (alumina)
Any material such as (WA), cubic boron nitride (CBN), or diamond can be used.
The cast iron powder may be obtained by crushing and sifting scraps generated during cutting or grinding of cast iron materials or cast iron products, or decarburized cast iron powder obtained by further decarburizing the waste. If decarburized cast iron powder is used, the amount of carbon can be controlled arbitrarily, so it is possible to increase the strength of the lapping tool and to strengthen the bond with the abrasive grains. In particular, when fine-grained decarburized cast iron powder and abrasive grains are used, the fine abrasive grains tend to invade inside from the boundaries of the cast iron powder as carbon moves during the heat treatment process. This allows the abrasive grains to be encapsulated in the cast iron powder, resulting in more uniform distribution and improved strength. Thus, the lap tool according to the present invention can be obtained through the following steps. That is, first, an abrasive is added at a predetermined ratio to cast iron powder, which is the base material, and mixed uniformly using a ball mill or the like. Next, a mixed powder 8 of cast iron powder 7 and abrasive (abrasive grains) 3 is filled into a die 9 as shown in FIG.
Pressure molding is performed using a punch 10. At this time, the mixed powder 8 may be filled with cast iron powder to a required thickness and simultaneously press-formed using a punch. In this way, a composite wrap integrally lined with a cast iron base can be obtained, so that the strength can be improved. Next, the green compact 11 of the cast iron powder and abrasive obtained in the previous step is charged into a furnace and sintered in a reducing atmosphere without pressure or with pressure applied. After sintering, it may be forged by applying pressure in a preheated die, or an annealing step may be added. In the above manufacturing process, the content and particle size of the abrasive in the cast iron powder, molding pressure, and sintering conditions are adjusted appropriately to obtain the strength (tensile strength, radial crushing strength) and lapping effect required for the lapping tool. It should be made into something. First, if the content of the abrasive is too high, it impairs the sinterability of the molded body and reduces its strength, which is not preferable. Generally 5 for cast iron powder
There is no problem if it is about ~15wt%. Furthermore, if the viscosity is too small, the porosity tends to increase and the strength tends to decrease. However, this can be improved to some extent by changing the molding pressure and sintering conditions. According to the inventor's experiments, within the above range of abrasive grain addition, especially the molding pressure is 6 to 8 tons/cm ² and the sintering temperature is 1125 to
By adopting a temperature of 1150℃, we were able to produce a highly practical lap tool that does not cause abrasive grain consumption, has sufficient bonding with cast iron powder, and does not cause lamination cracks. In addition, when performing annealing, a cycle such as holding at 730°C for 2 hours and furnace cooling to 400°C for 3 hours may be used. The composite lap 1 or lap segment 5 shown in Fig. 1 is obtained through the above process, and in the latter case, the lap segment 5 is ground to a certain size and then arranged and bonded to a substrate to form a lap tool. becomes. To prepare the initial surface of this lapping tool, after finishing the surface by grinding, it may be sharpened by wet lapping or polishing using a correction ring or the like.
As a result, a solid abrasive lap tool has a surface in which minute and uniformly rough cutting edges (fixed abrasive grain halves) protrude from the flat cast iron base and are uniformly aligned and distributed. Next, the operation of the lap tool according to the present invention will be explained. When the composite lap 1 shown in Fig. 1 is attached to a lap machine, the required oil such as kerosene (not including abrasive grains) is applied to the surface of the composite lap, and the workpiece is pressed while rotating the lap machine at the required number of revolutions. The wrap of the present invention is composed of a sintered composite of cast iron powder and abrasive grains, in which half of the abrasive grains 3 are densely protruded from the cast iron matrix 4 and slightly protrude from each other, and the remaining part is bonded to the cast iron matrix 4 to form a strong structure. The graphite contained in the cast iron matrix prevents seizure, and the pores created by sintering become holes for oil to accumulate, providing a good lubrication effect. Minute chips can be removed extremely efficiently. That is, in the present invention, unlike the case of loose abrasive grains, a fractured surface is not caused by the movement (rolling) of the abrasive grains, and the abrasive grains are separated by a method in which the abrasive grains are embedded in the recesses on the surface of the lap plate. It also does not cause any scratches or scratches. Therefore, the surface roughness of the workpiece is rapidly improved within a very short period of time, making it possible to finish it with a beautiful glossy surface. Since the lapping tool of the present invention has abrasive grains firmly fixed to the cast iron matrix, it has extremely good wear resistance, and as a result, the durability of the flatness, which is important for a lapping, is high and the number of corrections can be reduced. Furthermore, since there is no need to replenish abrasive grains, the consumption of abrasive grains can be kept to a minimum, and the work of embedding minute abrasive grains into recesses by rubbing them together can be completely eliminated, resulting in extremely good workability. Furthermore, since the abrasive grains are embedded in the cross-sectional structure of the cast iron base, it can be easily regenerated by sharpening the cast iron base again and scraping the cast iron base, making it possible to provide a long-life lapping tool. In the case of hard and brittle materials, the cast iron matrix is polished due to its material characteristics, resulting in a self-sharpening effect and no sharpening is required. In addition, by selecting the type of abrasive grains and mixing and sintering them with cast iron powder, it can be applied not only to metal materials but also to bright finishing of hard and brittle materials such as silicon, crystal, alumina ceramic, and silicon nitride. When applied to wrapping materials, the wrapping time and polishing time can be significantly shortened. In addition to ordinary wrapping, the present invention can be widely used as a hole sealing tool, barrel polishing media, shot peening shot, and, of course, as a polishing and grinding tool. Next, specific examples of the present invention will be shown. Example 1 () A composite lap was made by mixing cast iron powder with an abrasive and sintering it. At this time, the particle size distribution and chemical composition of the cast iron powder serving as the base material are shown in Table 1 below.

[Table] The abrasive grains are commercially available white alundum #80,
Using 3 types: #120, #320, #800, #1200,
5wt%, 10wt%, 15wt% of this to cast iron powder
% and mixed using a ball mill. () Next, the mixture was filled into a die of φ38 and 55×10 and molded, and after molding, it was sintered in a hydrogen-nitrogen reducing atmosphere to obtain a lap segment with a thickness of 10 mm. The one with a content of 15 wt% was forged after sintering. testing the segment for radial crushing strength;
FIG. 5 shows the relationship between the abrasive grain size, its content, molding pressure, and sintering temperature. According to this, when the abrasive grain content is 10%, the sintering temperature is 1125°C, and the molding pressure is 8 ton/cm ² , the influence of the abrasive grain size is small, and this can be used as a standard. This radial crushing strength can be further improved by forging after sintering, and there is no problem in use. () Next, the lap segments were arranged and glued on a disk to form a mechanical lap of φ300, and the surface was finished by grinding, wrapping, and sharpening by short-time polishing. Using the above lapping (abrasive grain size #1200), attach it to the lapping machine, add a small amount of kerosene to the lapping surface, and polish the material under the condition that the lapping machine rotation speed is 100 rpm.
Wrapping was performed on samples of SS41 and SK4. For comparison, wet lapping was performed using white alundum abrasive grains of the same material and particle size, mixed with equal amounts of kerosene and machine oil, and 20 wt% added. The results are shown in the electron micrographs of FIGS. 6a and 6b. FIG. 6a shows the finished surface by the composite lapping of the present invention, and FIG. 6b shows the finished surface by wet wrapping, and it can be seen that a much better finished surface can be obtained according to the present invention. At the same time, we tested the surface roughness using a stylus method, and found that Rmax for composite lapping was 0.4 μm, while Rmax for wet lapping was 1.4 μm. Improvements had been made. Example 2 () Spherical boron nitride (CBN) abrasive grain size #1200 was used as the abrasive grain, and it was added to cast iron powder at 5wt% and 10wt.
% and 15wt%, molding pressure 8ton/cm ² , sintering temperature 1125℃, sintering time 30
Lap segment (30×30×10t) under minute conditions
I made it. During molding, CBN-containing cast iron powder was filled in the die, followed by cast iron powder, and pressure molding was performed at the same time. The cross section of this segment is as shown in Figure 7, and out of the segment thickness of 10mm, the portion containing abrasive grains is approximately 1.5mm, and the required amount of CBN abrasive grains is 10wt%.
Approximately 16g in weight. () After the obtained lap segments were forged, they were aligned and adhered to a mild steel disk of φ140, and finished in the same order as in Example 1 by surface grinding, wet lapping, and polishing to form a lap surface plate surface. The photograph in Figure 8 shows an enlarged view of this surface (without the forging process), and it can be seen that the abrasive grains are uniformly distributed in a mesh pattern at the boundaries of the cast iron powder, and the CBN abrasive grains are slightly protruding from the matrix. Recognize. () A wrapping test was conducted using the above wrapping tool. The test pieces and wrapping conditions at this time are as shown in Tables 2 and 3 below.

【table】

【table】

[Table] () Figures 9 and 10 are graphs summarizing the wrapping results under the above conditions. The surface roughness was measured using a stylus method. From these figures, according to the present invention, for both cemented carbide and hard brittle materials, the wrap time is 1 minute (distance 16
It can be seen that the surface roughness can be rapidly improved within an extremely short period of time (m). Particularly for ceramics, it is possible to obtain a better surface roughness improvement effect in a shorter time than lapping with diamond abrasive grains having a small abrasive grain size. () At the same time, we tested the durability of the lap, that is, the property of maintaining the protruding state of the abrasive grains to form a cutting edge, using alumina ceramic. As a test method, a method was used in which the processing amount was measured by wrapping for a relatively long time. The results are shown in FIG. 11, and the amount of lapping did not decrease over a long period of time. This is because the minute chips of the hard and brittle workpiece uniformly abrade the cast iron matrix, creating a self-sharpening effect on the cutting edge, and from this point of view as well, the effects of the present invention are significant. Example 3 The results of a performance test of a sintered composite lap of the present invention of various abrasive grains and cast iron and a wet lap of the same kind of abrasive grains are shown in Table 4 below.

【table】

[Table] From Table 4, it can be seen that according to the present invention, the lapping tool has a very good lapping effect, can minimize the consumption of abrasive grains, and is an economical lapping tool. According to the present invention explained above, cast iron powder
Mix abrasive grains at a ratio of 15wt% or less, and molding pressure 6
It consists of a composite sintered body that is pressure-formed at ~8ton/ ^cm2 and sintered at a sintering temperature of 1125~1150℃.The abrasive grains are bonded and fixed to the welded cast iron grains that make up the sintered cast iron matrix, and the surface layer Since the abrasive grains are also dispersed and buried in the cast iron base below, the carbon contained in the cast iron can reduce the reaction with the abrasive grains, especially diamond, and the addition rate and molding pressure By setting the temperature conditions, it is possible to create a sintered body with a high degree of bonding between cast iron and abrasive grains, ensuring mechanical strength, which is important for tools.In addition to good strength in use, it also has excellent wear resistance. It has high durability and surface flatness, and it does not require lubrication and does not seize.
Because the abrasive grains are highly fixed, it is possible to form a good finished surface on metal materials and hard brittle materials in an extremely short time.Furthermore, there is no need to replenish the abrasive grains, resulting in good durability and a long service life. Excellent effects can be obtained, such as being able to achieve better results.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of a wrap tool according to the present invention, Fig. 2 is a sectional view of the wrap tool according to the present invention, Fig. 2a is a partially enlarged view thereof, and Figs. 3 a and b are according to the present invention. The third surface micrograph of the lap tool.
Figure a has a magnification of 180x, and Figure 3 b has a magnification of 250x.
FIG. 4 is a cross-sectional view showing the forming process of the tool of the present invention, and FIG. 5 is a graph showing the relationship between the radial crushing strength and forming pressure, sintering temperature, abrasive grain size and content of the wrap tool constituent unit in the present invention. Figures 6a and b are micrographs (magnification: 1800x) showing finished surfaces by the tool of the present invention and the conventional tool, Figure 7 is a cross-sectional view of another embodiment of the wrap tool of the present invention, and Figure 8 is a sectional view of the finished surface of the wrap tool according to the present invention. A micrograph (250x magnification) showing the surface of the abrasive CBN composite lapping tool according to the invention, Figures 9 and 10 are graphs showing the lapping results using the tool in Figure 9, and Figure 11
The figure is a graph showing the durability test results of the tool of the present invention. 1... Composite lap, 3... Abrasive grain, 4... Cast iron base, 7... Cast iron powder, 8... Mixed powder, 11... Molded body.

Claims (1)

[Claims] 1 Mix abrasive grains with cast iron powder at a ratio of 15wt% or less,
Pressure molded at a molding pressure of 6 to 8 tons/ ^cm2 , 1125 to 1150
It consists of a composite sintered body sintered at a sintering temperature of °C, and the abrasive grains are bonded and fixed to the welded cast iron grains that make up the sintered cast iron matrix, and the abrasive grains are also dispersed and buried in the cast iron matrix below the surface layer. A wrap tool that is characterized by: