JPH059231B2 - - Google Patents

Description

[Detailed description of the invention]

[Purpose of the Invention] (Field of Industrial Application) The present invention relates to an improvement in the method of forming a metal grinding wheel using centrifugal casting, in which intermetallic compounds such as Fe/Al etc. are added to the vicinity of grinding abrasive grains. to form,
This is a centrifugal forming method for metal whetstones that strengthens the base material and strengthens its abrasive retention. (Prior Art) As a method for manufacturing a grinding wheel using a centrifugal casting method, there is a publication in JP-A-58-94971 entitled "Method for Manufacturing a Super Abrasive Grinding Wheel." To explain this with reference to FIG. 6, the abrasive grains 22a, 22b, etc. are held on the inner peripheral surface of the cavity of the centrifugal casting mold by the abrasive grain holder 21 so that their tips are in contact with the inner peripheral surface of the cavity. 24, and while rotating a mold (not shown) as shown in 25, the molten metal 23 of the grinding wheel fixing metal is injected into the gap between the abrasive grain holder 21 and the outer periphery of the grinding wheel base metal by centrifugal force, and the grinding wheel base metal is removed. A metal for fixing abrasive grains is fixed to 24, and the abrasive grain holder 2
A method for manufacturing a grinding wheel is disclosed in which the height of the abrasive grains of the grinding wheel is made uniform by removing 1. (Problem to be solved by the invention) However, although this conventional manufacturing method for grinding wheels makes the height of the abrasive grains uniform, the abrasive grains are not firmly held by the fixed metal due to the uneven diameter of the abrasive grains. Abrasive grains are generated and the abrasive grains are likely to peel off. In the conventional method of forming grinding wheels by centrifugal casting, Al or Al alloys and Cu or Cu alloys 23 that hold carbide abrasive grains such as diamond, cubic boron nitride (CBN), and GC abrasive grains (SiC) are used. The bonding force between the substrate and the abrasive grains is not sufficient against the grinding force during the soft grinding process, and as a result, the abrasive grains are likely to peel off. That is, during the grinding process, stress is generated around the abrasive grains in the abrasive grains in the whetstone due to the stress caused by the grinding, and the abrasive grains fall off. This can be explained by modeling the state of one abrasive grain in a grinding wheel and using stress analysis in Figure 7.The model setting conditions are that the abrasive grain is a completely rigid body, and the surrounding base material is considered to be a completely elastic-plastic body. The bonding force shall be strong enough to withstand the grinding force. The shape of the abrasive grains is a conical apex angle of 90°, and the length of the slope is L.
Assume that the bottom surfaces of 100 μm cones are overlapped, and 1/2 (one cone) is embedded in the base material, and a, b, c, and d are the vertices of the cones, and e is
is the base material. Here, g: depth of cut, G: specific cutting force, 2r: cone apex angle = 90°, N: vertical component of grinding force, T:
Assuming the horizontal component of the grinding force, dN=1/2G ² sin ² r cos r cosφ d φ dT=1/2G ² sin r cos ² r cos ² φ d φ ∴N=∫〓 ^/2 _- 〓 _/2 dN/dφ・dφ=G ² sin r・tan
r= 0.71G ² T=∫〓 ^/2 _- 〓 _/2 dT／dφ・dφ=π/4G ² sin r
= 0.56G g ² Therefore, considering the vertical stress distribution applied to the substrate, the stress caused by N is uniformly distributed on ab and bc, and the abrasive grain abcd due to T has a rotational force with point b at the midpoint. If this occurs, the stress distribution on the ab and bc planes will be as shown in Figure 7 (b), and the maximum normal stress will occur on the plane perpendicular to point a, which will become the base point for abrasive grain dropout, and its magnitude will be |σ max | It is expressed as =0.81GgKg/ ^mm2 . Furthermore, if we actually measure the depth when a diamond indenter is pressed into each material with a constant load and calculate the G (specific cutting resistance value) of each cutting material from the following formula, G (empirical formula) = 42 × Table 1 shows the results obtained using 10 ^{3 -1.24} (in μm). still
A2024 is an Al-Cu alloy. (The above formula is based on the Transactions of the Japan Society of Mechanical Engineers Vol. 18, No. 74, 1952, p. 15.)

[Table] Using the values in Table 1 G, the values of T, N, and |σ max | are shown in Table 2 for each material.

[Structure of the invention]

(Means for Solving the Problems) The technical solutions taken in the present invention to solve the above problems are as follows:
In the centrifugal molding method for metal grindstones, which involves filling abrasive grains such as diamond, melting the base metal, and rotating the mold to form the metal whetstone using centrifugal force, (1) Applying a release agent to the mold; Then, a base metal material made of Al or Al alloy is inserted into the mold, and (2) abrasive grains such as diamond and metal powders of iron, nickel, and titanium are placed in the gap between the inner surface of the mold and the outer peripheral surface of the base metal material. (3) heating the base metal material, abrasive grains, and metal powder;
After the base metal material is melted, it is held at a high temperature for a certain period of time, (4) the mold is rotated, and the molten metal of the base metal material is impregnated by centrifugal force into the abrasive grain layer in which metal powder is mixed at a certain ratio; Centrifugation of metal grinding wheels that forms intermetallic compounds on the surface of metal powder, disperses them in the abrasive grain layer, and then solidifies the abrasive grains and base metal material to form the abrasive grain layer and base metal material into one piece. It is a molding method. (Operation) The technical means operates as follows. In other words, Al or Al alloy, which is the base metal material, becomes molten in the mold by heating to about 700℃, penetrates into the abrasive grain layer such as diamond filled in the gap, and further melts into the abrasive grain layer such as iron, nickel, titanium, etc. powder is also Al or Al
By being fused with the molten alloy and heated for several to 30 minutes, a hard intermetallic compound is formed on the surface of the iron, nickel, or titanium powder, resulting in a hard surface hardness of 700 to 900 Hv. The inside is iron,
The powder, which has toughness such as nickel or titanium, is dispersed in each part of the abrasive layer by centrifugal rotation, and the base material solidifies, so that the abrasive layer is mixed with the metal powder with increased hardness. As a result, the powder with increased hardness is dispersed around the abrasive grains, so that the abrasive grains are held strongly and reliably, and the abrasive grains are hardly peeled off. (Example) Hereinafter, specific examples of the above technical means will be described. 1 is a rotary molding type using a centrifugal casting forming device, and 2
is a rotating body, 3 is a heating device, 3a is a heater, 4
5 is a rotating plate, 5 is a motor, 6 is a temperature regulator, 7 is a ventilation hose, 8 is a lid of the rotating body, and 9 is a mold. Incidentally, some centrifugal casting forming apparatuses are of a swing forming type. To explain the manufacturing method in the above structure, a mold release agent (peel coat, dye louver, tycoso, etc.) is applied to the inside of the mold 9, and after drying, Al or
A base metal material 11 made of Al alloy is placed in the gap 10 between the mold 9 and the base metal material 11 (adjustable depending on the size of the base metal material). Abrasive grains 17a, 17b... (diamond abrasive grains, CBN abrasive grains, or GC Abrasive grain size is 20~
50 μm) and iron powders 15a and 15b are densely mixed and packed, and depending on the manufacturing conditions (such as when dispersing abrasive grains with a wide dispersion width, when dispersing abrasive grains with poor wettability, when controlling the concentration of abrasive grains, etc.), After mixing the Al powder together and heating the mold 9 in a melting furnace or a centrifuge with a heated melting furnace to melt the base metal material 11, it is kept at 650°C to 800°C for several minutes to about 30 minutes while being polished. Intermetallic compounds (Fe ₃ Al, FeAl, FeAl ₃ , etc.) 16 are present on the surface of the iron powders 15a and 15b mixed together with the grains.
a, 16b are generated, the rotary plate 4 and mold 9 are rotated by the operation of the motor 5, the abrasive grain layer 14 is impregnated with the molten metal, and the abrasive layer 14 is slowly solidified under high temperature to improve the flow of the hot water to form a whetstone. The outer circumferential surface 18 of the whetstone is appropriately sharpened to form a surface 19 on which abrasive grains protrude. Note that the Al powder also plays the role of promoting melting with the base metal material. The cross section of the grindstone manufactured by this method is
As shown in the figure. 12 is a grinding wheel, 13 is a base metal material such as Al, 14 is an abrasive grain layer, and a ₁ , a ₂ , a ₃ are Fe with intermetallic compounds formed on the surface generated within the abrasive grains.
With powder such as, if you enlarge it, it will be 15a, 15c.
16a and 16c are intermetallic compounds produced by being held at high temperatures. Next, the hardness of the metal whetstone formed by the above method was measured. In Fig. 3 A, the surface of the whetstone is A, and the position 5 mm from the surface toward the center is B, and A → B.
The hardness of the grinding wheel was measured at 0.2 mm intervals between
AlCu alloy, the abrasive grains are GC abrasive grains, and as metal powder
Using Fe, the base metal material of A2024 is GC: Fe powder = 1:
Fill the mold at a ratio of 1:1 in a 120° atmosphere,
After preheating, heat to 700℃, 2030rpm (671G)
It was rotated for 5 minutes. A in Figure 4 is 700℃
In the case of heating for 30 minutes, B indicates the case of heating for 60 minutes, H is the micro-Vickers hardness, and S is the surface measurement point. In both cases, the hardness is approximately 800Hv, which is several times harder than the measured value P (approximately 100Hv) of the A2024 base metal, and the hardness when the mold is heated for 30 minutes =
It was 790.5Hv, and for 60 minutes it was = 762.9Hv. FIG. 5 is a replica of a microscopic photograph of a part of the measurement surface enlarged 500 times, in which dimensions C to D are 20 μm, 15b and 15c are metal powders, 16b and 16
c is an intermetallic compound on the surface of the abrasive grain, 17c,
17d is a GC abrasive grain, and a ₄ , a ₅ , and a ₆ are metal powders on the surface of which intermetallic compounds are uniformly dispersed in the abrasive grain layer 14 . [Effects of the Invention] The present invention has the following effects. In other words, metal powder such as iron, nickel, or titanium combined with abrasive grains generates an intermetallic compound on the surface of the metal powder, which is further dispersed around the abrasive grains, thereby greatly increasing the holding power of the abrasive grains. Furthermore, the hardness of the abrasive grain layer itself can be freely changed by changing the amount of metal powder mixed, and by dispersing the abrasive grains appropriately depending on the use of the metal whetstone, it is possible to achieve sharpness. It is possible to manufacture whetstones, and it is possible to manufacture highly efficient metal whetstones that match the material to be ground. In addition, the abrasive grain layer and base metal are molded at the same time,
Since the base metal also serves as a binder, the manufacturing process is shortened.

[Brief explanation of the drawing]

FIG. 1 is a simplified diagram of a rotary molding type centrifugal molding machine, and FIG. 2 is a sectional view of a metal grindstone after molding. FIG. 3 is an enlarged sectional view of the abrasive grain layer, with A showing after molding and B showing after the outer peripheral surface has been sharpened. C is an enlarged cross-sectional view of powder such as Fe with intermetallic compounds formed on the surface. FIG. 4 is a graph of the measured hardness values between A and B in FIG. Figure 5 is a partial plan view of A in Figure 3.
This is a 500x magnification and is a reproduction of a micrograph. FIG. 6 is a cross-sectional view of a conventional example, in which A shows a state in which molding is in progress, and B shows a state in which some abrasive grains have peeled off. FIG. 7 is a block diagram of the conventional example, where A shows the load situation before peeling, and B shows the load situation when peeling occurs. 1... Centrifugal rotation molding device, 9... Mold, 13...
...base metal material, 14...abrasive grain layer, 15...metal powder,
17a, 17b... Abrasive grains.

Claims (1)

[Scope of Claims] 1. Centrifugal manufacturing of metal whetstones, in which a mold for manufacturing metal whetstones is filled with abrasive grains such as diamond, a metal serving as a base material is melted, and the mold is rotated to form the metal whetstones by centrifugal force. In the molding method, (1) a mold release agent is applied to the mold, a base metal material made of Al or Al alloy is inserted into the mold, and (2) a gap between the inner surface of the mold and the outer peripheral surface of the base metal material is filled. (3) heating the base material, the abrasive grains, and the metal powder;
After the base metal material is melted, it is held at a high temperature for a certain period of time, (4) the mold is rotated, and the molten metal of the base metal material is impregnated by centrifugal force into the abrasive grain layer in which metal powder is mixed at a certain ratio; Centrifugation of metal grinding wheels that forms intermetallic compounds on the surface of metal powder, disperses them in the abrasive grain layer, and then solidifies the abrasive grains and base metal material to form the abrasive grain layer and base metal material into one piece. Molding method.