JP6491735B1 - Sintered product manufacturing method and sintered product - Google Patents

Abstract

Provided is a method for producing a tungsten-based or similar sintered product having a refrigerant passage having a complicated shape therein.
A first powder compact 67 having a complex first refrigerant passage 68 and a second powder compact 74 having a second refrigerant passage 75 are prepared. The first powder compact 67 and the second powder compact 74 are mainly made of tungsten powder. A superposed body 78 formed by superposing the first powder compact body 67 on the second powder compact body 74 is put in a sintering furnace 80 and liquid phase sintered. The boundary 77 existing before sintering disappears after sintering.
[Selection] Figure 7

Description

The present invention relates to a sintered product that having a refrigerant passage therein.

  For example, a cylinder head that is one of the components of an internal combustion engine is manufactured by a casting method. In the casting method, a molten metal such as an aluminum alloy is poured into a cavity of a mold, and when the molten metal is solidified, the molten metal is taken out from the mold. The removed one becomes a cylinder head.

The shape of the combustion chamber in the internal combustion engine greatly affects the output. Therefore, the accuracy of the combustion chamber is required.
Since a part of the combustion chamber is formed by the cylinder head, the combustion chamber of the cylinder head is required to have higher accuracy and strength than other parts of the cylinder head.

In the cylinder head mold, it has been proposed to cool the combustion chamber forming portion (see, for example, Patent Document 1 (FIG. 5)).
By cooling, thermal deformation of the combustion chamber forming portion and coarsening of the solidified structure can be suppressed. Without thermal deformation, the accuracy of the combustion chamber can be increased. Moreover, the structure of a casting can be made dense by cooling.

FIG. 5 of Patent Document 1 shows a lower mold (3) (numbers in parentheses indicate reference numerals described in Patent Document 1. The same applies hereinafter) used for casting a cylinder head.
A combustion chamber core (9c) is attached to the lower mold (3). The combustion chamber core (9c) is provided with a cooling passage (12). By flowing a coolant (water or air) through the cooling passage (12), the temperature of the combustion chamber core (9c) is prevented from rising.

The technique of Patent Document 1 has the following problems.
First, regarding the shape of the cooling passage (12), there are the following problems.
Although there is no disclosure of the material in Patent Document 1, the material of the combustion chamber core (9c) is presumed to be mold steel or equivalent steel. A combustion chamber core (9c) can be obtained by machining the steel block. At this time, the cooling passage (12) is machined with a drill. A drill is a cutting tool for machining straight holes.
As a result, the cooling passage (12) shown in FIG. 5 of Patent Document 1 is linear and has a simple form.

In the simple form of the cooling passage (12), it is difficult to cool to the corner of the combustion chamber core (9c). As a result, the strength of the combustion chamber is reduced.
However, since the combustion chamber is a functionally important part, improvement in strength is desired.

Next, when the material of the combustion chamber core (9c) is steel, it is melted by molten aluminum.
While the combustion chamber core (9c) is required to have a long life, it is desirable to use a material that is resistant to melting.

Moreover, when the combustion chamber core (9c) is steel, the thermal conductivity of steel is lower than that of aluminum. If the thermal conductivity is low, the heat tends to be trapped.
As a countermeasure, it is necessary to increase the amount of refrigerant supplied to the cooling passage (12). The cross-sectional area of the cooling passage (12) also needs to be increased, which affects the mold design.
Therefore, it is desirable that the combustion chamber core (9c) be made of a material having a higher thermal conductivity than steel.

  While improvement in the quality of cast products such as cylinder heads is required, metal parts such as a combustion chamber core having a higher thermal conductivity than steel, being resistant to melting, and having a complicatedly shaped refrigerant passage inside are desired.

Japanese Patent No. 3636108

  The present invention is a metal part that has higher heat conductivity than steel, is resistant to erosion, has a complicated refrigerant passage inside, and can be used for a combustion chamber core (hereinafter referred to as nesting) or the like. It is an issue to provide.

The invention according to claim 1 is a preparation step of preparing a powder mainly comprising at least one of tungsten, molybdenum, and tungsten carbide, a first mold, a second mold, and a sintering furnace;
A first molding step in which the powder is charged into the first mold and pressed to obtain a first compact;
A step of forming a first refrigerant passage for allowing the refrigerant to flow through the obtained first green compact,
A second molding step in which the powder is charged into the second mold and pressed to obtain a second compact.
Forming a second refrigerant passage for allowing the refrigerant to flow through the obtained second green compact,
Obtaining a superimposed body by combining the first powder compact with the second powder compact so that the first refrigerant passage is connected to the second refrigerant passage;
And the resulting step of piled body to obtain a sintered product by liquid-phase sintering in the sintering furnace, to provide a method of manufacturing a Ru Tona sinter.

The invention according to claim 2, tungsten, molybdenum, a sintered product shall be the main component at least one tungsten carbide,
It has a refrigerant passage inside, and some of the refrigerant passages have a cross-sectional shape combining a straight bottom and an inverted U-shaped wall, and the straight bottom is the central axis of the sintered product. It extends along the orthogonal line which intersects perpendicularly .

The invention according to claim 3 is a sintered article of claim 2, wherein,
The refrigerant passage is a spiral refrigerant passage .

According to the first aspect of the present invention, a first powder compact is mainly made of a powder mainly composed of at least one of tungsten, molybdenum, and tungsten carbide, and the first refrigerant is added to the first powder compact. A passage,
Creating a second compacted body mainly composed of at least one of tungsten, molybdenum and tungsten carbide, and providing a second refrigerant passage in the second compacted body;
Second green compact as the first refrigerant passage leading to the second refrigerant passage combined first green compact, by applying the liquid phase sintering process to obtain a sintered product.

Tungsten, molybdenum and tungsten carbide powders have higher thermal conductivity than steel and are resistant to erosion.
If it is before match | combining a 1st powder compact with a 2nd powder compact, a 1st powder compact can be provided with the 1st refrigerant path of a complicated form. The same applies to the second green compact.
According to the present invention, high thermal conductivity than steel, sinters that have a refrigerant passage of the complex form inside and strongly corrosion is provided.

In the invention according to claim 2, some of the cooling passages have a straight bottom extending along an orthogonal line orthogonal to the central axis of the tungsten-based or similar sintered product.
Even if foreign matter is mixed in the refrigerant, the foreign matter is less likely to stay if it is a straight bottom.

In addition, in the invention according to claim 2, as in claim 1, tungsten, molybdenum, and tungsten carbide have higher thermal conductivity and higher resistance to melting than steel.
In addition, when two sintered compacts are combined and sintered to produce a sintered product, a groove is formed in one compacted body, and the opening of this groove is closed with the other compacted body. A refrigerant passage can be formed. Since the groove is opened before superposition, it can be easily formed in one of the green compacts.

In the invention according to claim 3, the refrigerant passage is a spiral refrigerant passage. Although the conventional refrigerant passage is a simple linear passage, the refrigerant passage of the present invention is a complicated passage.

It is principal part sectional drawing of an internal combustion engine. It is sectional drawing of a cylinder head. It is sectional drawing of a metal mold | die. It is a figure explaining the manufacturing process of a 1st compacting body. It is sectional drawing and bottom view of a 1st compacting body. It is a figure explaining the manufacturing process of the 2nd compacting body. It is a figure explaining a sintering process. It is sectional drawing of a nesting. It is a side view of a front milling machine. It is sectional drawing of a face mill. It is a figure explaining the manufacturing process of a body.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, a specific example of casting a cylinder head, a specific example of the sintered product was nested.

As shown in FIG. 1, the internal combustion engine 10 includes a cylinder block 11, a cylinder head 12 mounted on the cylinder block 11, and a head cover 13 that covers the upper surface of the cylinder head 12.
The cylinder head 12 has an intake passage 14 and an exhaust passage 15. The intake passage 14 and the exhaust passage 15 are opened and closed by a valve mechanism 20.

  The valve mechanism 20 includes an intake valve 21 that opens and closes the intake passage 14, an intake side spring 22 that urges the intake valve 21 toward the closing side, an intake side rocker arm 23 that pushes the intake valve 21 toward the open side, and the intake valve An intake side rocker shaft 24 that supports the side rocker arm 23, a cam shaft 25 that swings the intake side rocker shaft 24, an exhaust valve 26 that opens and closes the exhaust passage 15, and an exhaust that biases the exhaust valve 26 toward the closing side. It comprises a side spring 27, an exhaust side rocker arm 28 that pushes the exhaust valve 26 to the open side, and an exhaust side rocker shaft 29 that supports the exhaust side rocker arm 28. The exhaust side rocker arm 28 is also swung by the cam shaft 25.

Below the intake valve 21 and the exhaust valve 26 is a combustion chamber top (hereinafter simply referred to as a combustion chamber 31).
The intake side spring seat 32 and the exhaust side spring seat 33 are formed by machining a casting (FIG. 2, reference numeral 40).
The intake side valve seat 34, the intake side valve guide 35 disposed above the exhaust side valve seat 36, the exhaust side valve seat 36, and the exhaust side valve guide 37 disposed above the Fits into castings.

The cast product 40 before machining is described with reference to FIG.
As shown in FIG. 2, a cylinder head casting 40 includes a combustion chamber 31, an intake passage 14 extending to the combustion chamber 31, an exhaust passage 15 extending from the combustion chamber 31, and a camshaft (see reference numeral 25 in FIG. 1). ) And the like.

An example of the metal mold | die 50 which casts the casting 40 of such a structure is demonstrated based on FIG.
As shown in FIG. 3, the mold 50 includes a lower mold 51, a left side mold 52, a right side mold 53, and an upper mold 54. At the center of the upper surface of the lower mold 51, a nest 90 forming a combustion chamber (FIG. 2, reference numeral 31) is attached. Further, a collapsible core 55 that forms an intake passage (FIG. 2, reference numeral 14) is passed to the insert 90 and the left side mold 52, and an exhaust passage (FIG. 2, FIG. 2) is passed to the insert 90 and the right side mold 53. A collapsible core 56 is passed forming 15).

  A molten aluminum alloy is injected into the cavity 57 in the mold 50. When the melt has solidified, open the mold. The collapsible cores 55 and 56 are broken and scraped. Thus, the cast product 40 shown in FIG. 2 is obtained. The casting method is preferably a low pressure casting method.

The low-pressure casting method is also called a low-pressure mold casting method, in which a furnace is disposed below the mold, the molten metal is filled in the furnace, and a conduit extending from the mold is inserted into the molten metal. Then, a pressure of about (atmospheric pressure + 50 kPa) is applied to the upper surface of the molten metal. With this pressurization, the molten metal is supplied to the mold through the conduit.
Since the degree of pressurization is much lower than the die casting method, it is called the low pressure casting method.

Among the elements constituting the mold 50, the insert 90 is an important part. This is because the component is involved in the shape formation of the combustion chamber 31 requiring high accuracy.
A method of manufacturing such a nesting 90 will be described next.

  As shown in FIG. 4A, the first die 61, the first lower punch 62 fitted to the first die 61 from below, and the first upper punch 63 disposed above the first lower punch 62. A first mold 60 is prepared. Then, a metal mixed powder 64 as a powder containing tungsten as a main material is put into the first die 61.

The metal mixed powder 64 is preferably a mixture of a tungsten powder 65 as a main material and a nickel powder 66 as an auxiliary material. In addition to the tungsten powder, the main material may be molybdenum powder, tungsten carbide powder, or a mixture thereof.
As a mixing ratio, the main material may be 80 to 99% by mass and the balance may be an auxiliary material.

In FIG. 4B, the metal mixed powder 64 in the first die 61 is compressed by the first lower punch 62 and the first upper punch 63.
As a result, the first green compact 67 shown in FIG. 4C is obtained.
In addition, although mentioned later in detail, you may form the 1st cooling channel | path 68 shown with an imaginary line in FIG.4 (c) at the 1st compacting process simultaneously with compacting.

Next, as shown to Fig.5 (a), the groove-shaped 1st refrigerant path 68 currently opened below is formed in the 1st compacting body 67 by machining.
The first green compact 67 second green compact (Fig. 6, reference numeral 74) when manufacturing the sinter by sintering together, the groove (groove-like in the first green compact 67 1 refrigerant path 68) is formed, and the opening of this groove is closed with the second green compact, whereby the first refrigerant path 68 can be formed. Since the groove | channel of the 1st compacting body 67 is open | released, it can form in the 1st compacting body 67 easily.

The first refrigerant passage 68 may be configured such that the same shape of solid wax is embedded in the first powder compact 67 and melted and discharged after the powder compaction process.
As shown in FIG. 5B, which is a view taken in the direction of arrow b in FIG. 5A, the first refrigerant passage 68 is a spiral passage. For convenience, the center of the vortex is the inlet 68a, and the part farthest from the center is the outlet 68b.

  Such a first refrigerant passage 68 is provided with a spiral projection on the upper surface of the first lower punch 62 shown in FIG. In the step of obtaining, the first refrigerant passage 68 may also be formed. In this case, the first molding step for obtaining the first green compact 67 and the step for forming the first refrigerant passage are performed in parallel.

Further, as shown in FIG. 6A, the second die 71, the second lower punch 72 fitted into the second die 71 from below, and the second upper punch 73 disposed above the second lower punch 72. The 2nd shaping | molding die 70 which consists of these is prepared. Then, the metal mixed powder 64 is put into the second die 71.
The metal mixed powder 64 is made of the same material as the constituent elements of the first powder compact (FIG. 4, reference numeral 64).

In FIG. 6B, the metal mixed powder 64 in the second die 71 is compressed by the second lower punch 72 and the second upper punch 73.
As a result, the second green compact 74 shown in FIG. 6C is obtained.

As shown in FIG. 6D, a second refrigerant passage 75 is provided in the second green compact 74 by machining.
The second refrigerant passage 75 includes, for example, a long first horizontal hole 75a, a first vertical hole 75b that rises obliquely from the tip of the first horizontal hole 75a, a short second horizontal hole 75c provided on the opposite side of the first horizontal hole 75a, The second vertical hole 75d rises from the tip of the second horizontal hole 75c.
The second refrigerant passage 75 may be formed by embedding a solid wax of the same shape in the second compacting body 74 and melting and discharging it after the compacting process.

Next, as shown to Fig.7 (a), the 1st compacting body 67 is accumulated on the 2nd compacting body 74. FIG. The boundary between the first green compact 67 and the second green compact 74 is a boundary 77.
In the obtained superimposed body 78, the first vertical hole 75 b is connected to the inlet 68 a of the first refrigerant passage 68, and the second vertical hole 75 d is connected to the outlet 68 b of the first refrigerant passage 68.

Next, as shown in FIG. 7B, the superposed body 78 is put in a sintering furnace 80 and subjected to liquid phase sintering.
The sintering furnace 80 includes, for example, a cylindrical container 81, a heat insulating material 82 lining the container 81, a heater 83 disposed in the container 81, and a vacuum pump 84 that evacuates the container 81. .

  When evacuated by the vacuum pump 84, atmospheric pressure is applied to the outer peripheral surface of the container 81. Since the container 81 is a cylinder, there is no fear of being crushed. Carbon burns in the atmosphere but does not burn in a vacuum. Therefore, a carbon fiber can be used for the heat insulating material 82 and a carbon rod can be used for the heater 83. The carbon rod glows red when it is energized and acts as a heater.

  The liquid phase sintering process may be performed in an inert gas (argon gas, nitrogen gas) atmosphere in addition to the vacuum. Therefore, the sintering furnace 80 is not limited to a vacuum sintering facility.

The liquid phase sintering method is a processing method in which some components are dissolved during sintering and proceed in a mixed liquid phase state. The explanation will be tried again based on the embodiment.
The melting point of tungsten is 3380 ° C., and the melting point of nickel is 1453 ° C. The inside of the container 81 is evacuated and kept at about 1500 ° C. by the heater 83.
As a result, the nickel powder on the low melting point side becomes a liquid phase, and the tungsten powder on the high melting point side remains in a solid phase, and liquid phase sintering proceeds in a mixed liquid phase state.

Thus, it nested 90 as shown to sinter in FIG. 8 (a) is obtained.
In this nesting 90, when a coolant such as water is supplied to the first horizontal hole 75a, the refrigerant enters the first refrigerant passage 68 through the first vertical hole 75b, and the nesting 90 is inserted while passing through the first refrigerant passage 68. Cool to every corner. The warmed refrigerant is discharged through the outlet 68b, the second vertical hole 75d, and the second horizontal hole 75c.

FIG. 8B is an enlarged view of a portion b in FIG. 8A and shows a cross section of a general portion of the insert 90. The tungsten particles 91 are sintered such that the gap is filled with the nickel melt 92.
FIG. 8C is an enlarged view of part c of FIG. 8A and shows the vicinity of the boundary between the outlet 68b and the second vertical hole 75d. As in FIG. 8B, the tungsten particles 91 are sintered so that the gap is filled with the nickel melt 92.

If an A sintered product and a B sintered product (not shown) are overlapped and sintered again, a boundary layer is inevitably formed at the boundary between the A sintered product and the B sintered product. A boundary layer generated by sintering performed twice is not preferable because it causes a decrease in strength.
On the other hand, in the present invention, since the sintering is performed only once, a boundary layer cannot be formed. That is, the boundary 77 between the first green compact 67 and the second green compact 74 shown in FIG. 7 (a) has disappeared, and this bonded part is liquid-phase sintered in the same form as the general part, which is harmful. The boundary layer cannot be made.

As shown in FIG. 8 (d), nested 90 as sinter extends along the central axis 93. The central axis 93 coincides with the movement axes of the first upper punch (FIG. 4, reference numeral 63) and the second upper punch (FIG. 6, reference numeral 73).
The first refrigerant passage 68 has a cross-sectional shape in which a straight bottom 68c and an inverted U-shaped wall 68d are combined.
That is, of the refrigerant passages composed of the first refrigerant passage 68 and the second refrigerant passage 75, some of the cooling passages (first refrigerant passage 68) are straight bottoms extending along an orthogonal line 94 orthogonal to the central axis 93. 68c.

For example, when the bottom is V-shaped or U-shaped, a slight amount of foreign matter contained in the refrigerant tends to stay in the V-shaped (or U-shaped) valley bottom. That is, since the V-shaped (or U-shaped) valley bottom is narrow, the accumulated foreign matter is not easily discharged. The staying foreign matter reduces the cross-sectional area of the flow path and affects the cooling.
In this regard, if the straight bottom 68c is used, there is no fear that foreign matter accumulates, and the cooling performance is maintained.
The inverted U-shaped wall 68d may be an inverted V-shaped wall or a U-shaped wall, and its shape is arbitrary.

For comparison with the present invention, a conventional bonding method will be described with reference to FIGS.
As shown in FIG. 8E, a lower half 202 having a groove 201 and an upper half 204 having a groove 203 are prepared. The lower half 202 and the upper half 204 are made of cast steel or machined mold steel.

  As shown in FIG. 8 (f), the upper half body 204 is overlapped with the lower half body 202, and the discharge plasma pulse energization method is performed. That is, when a high voltage is applied to the lower punch 205 and the upper punch 206, current concentrates on the boundary 207 between the lower half 202 and the upper half 204, and the boundary 207 is melted due to resistance heat generation. By this melting, the upper half 204 is fused to the lower half 202.

However, the current is concentrated where it tends to flow. Therefore, a portion where the melting is good and a portion where the melting is insufficient are mixed in the boundary 207.
A boundary layer 208 in which a good melting portion and an incomplete melting portion are mixed is formed at the boundary 207.
Cracks occur due to thermal strain due to external forces or repeated thermal changes, and the incompletely melted portion of the boundary layer 208 becomes a base point for destruction and causes leakage of cooling water. Therefore, the upper half 204 may be broken from the lower half 202 with a force less than a predetermined value. That is, in the comparative example, a desired bonding strength may not be obtained.

  In this respect, as described with reference to FIGS. 8A to 8C, the boundary layer itself does not exist in the insert 90 according to the present invention. As a result, the mechanical strength is sufficiently high. Although the boundary layer prevents heat conduction, the nested 90 according to the present invention maintains high thermal conductivity because the boundary layer itself does not exist.

  Further, the thermal conductivity of the cast steel or mold steel exemplified in FIG. 8E is about 50 W / (m · K). On the other hand, the thermal conductivity of tungsten employed in the present invention is 177 W / (m · K). Tungsten has a thermal conductivity that is about three times higher, so that the cooling efficiency is improved, and the insert 90 can be cooled sufficiently and with a small amount of refrigerant.

The manufacturing method of the nesting 90 described above can be summarized as a manufacturing method as described below. Incidentally, nesting 90 generalizes read as sinter.

That is , a method for manufacturing a sintered product includes a powder mainly composed of at least one of tungsten, molybdenum, and tungsten carbide (FIG. 4, metal mixed powder 64), a first mold (FIG. 4, reference numeral 60), A preparation step of preparing a second mold (FIG. 6, reference numeral 70) and a sintering furnace (FIG. 7, reference numeral 80);
A first molding step in which the powder is charged into the first molding die and pressed to obtain a first compacted body (FIG. 4, reference numeral 67);
Forming a first refrigerant passage (FIG. 5, reference numeral 68) for flowing a refrigerant through the obtained first green compact,
A second molding step in which the powder is put into the second mold and pressed to obtain a second compact (FIG. 6, reference numeral 74);
Forming a second refrigerant passage (FIG. 6, reference numeral 75) for allowing the refrigerant to flow through the obtained second green compact,
A step of obtaining a superimposed body (FIG. 7, reference numeral 78) by combining the first powder compact with the second powder compact so that the first refrigerant passage is connected to the second refrigerant passage;
The obtained superposed body is subjected to liquid phase sintering in the sintering furnace to obtain a sintered product (FIG. 8, nest 90).

Next, a modification example will be described.
As shown in FIG. 9, the face mill 100 includes a shank 101, a body 110 fixed to the tip of the shank 101, and a blade 103 attached to the front surface (lower surface in the drawing). The blade 103 has a blade, and the workpiece 104 is cut with this blade.

In general, a coolant 106 is injected from a coolant supply pipe 105 between the workpiece 104 and the blade 103. The blade 103 is cooled by the coolant 106. The body 110 is indirectly cooled by the coolant 106. The coolant 106 is a cutting fluid that also serves as a coolant.
Under conditions of high-load cutting due to high-speed rotation in recent years, there is a concern that the temperature of the body 110 will rise. Cooling with the coolant 106 is insufficient.

When the temperature of the body 110 rises, the thermal deformation becomes remarkable, the blade 103 is displaced from a predetermined position, and the processing accuracy is lowered.
As a countermeasure, strong cooling of the body 110 is desired. A structure that can meet this demand will be described with reference to FIG.

As shown in FIG. 10A, in the face mill 100, the shank 101 is provided with a refrigerant supply path 111 and a refrigerant discharge path 112, and the body 110 is provided with first refrigerant paths 113a and 113b and a second refrigerant path 114. ing.
Such a body 110 is joined to the shank 101 with, for example, a brazing material 107 by a brazing method.

As shown in FIG. 10B, which is a cross-sectional view taken along the line bb of FIG. 10A, the second refrigerant passage 114 provided in the body 110 includes an inlet portion 114a, an annular portion 114b, an outlet portion 114c, And has a sufficiently complex shape. The inlet 114a is connected to the refrigerant supply path 111 via the first refrigerant passage 113a, and the outlet 114c is connected to the refrigerant discharge path 112 via the first refrigerant passage 113b.
A manufacturing procedure of the body 110 having such a structure will be described with reference to FIG.

The 1st compacting body 67 shown to Fig.11 (a) is shape | molded. The first compacted body 67 is compacted using at least one powder of tungsten, molybdenum, and tungsten carbide as a main material. The first green compact 67 is provided with first refrigerant passages 113a and 113b penetrating vertically.
In parallel, the 2nd compacting body 74 shown in Drawing 11 (b) is fabricated. The second green compact 74 is the same material as the first green compact 67. The second powder compact 74 is provided with a second refrigerant passage 114 having an open upper surface.

As shown in FIG.11 (c), the 1st compacting body 67 is accumulated on the 2nd compacting body 74, and the obtained superposition body 78 is liquid-phase-sintered.
The obtained body 110 is shown in FIG. The body 110 has first refrigerant passages 113a and 113b and a second refrigerant passage 114 inside, and does not have a boundary layer inside.

The body 110 of the sintered product extends along the central axis 93. The second refrigerant passage 114 has a cross-sectional shape that combines a straight bottom 68c and an inverted U-shaped wall 68d.
That is, of the refrigerant passages including the first refrigerant passages 113 a and 113 b and the second refrigerant passage 114, some of the cooling passages (second refrigerant passages 114) are straight lines extending along an orthogonal line 94 orthogonal to the central axis 93. It has a bottom 68c.

When manufacturing the first green compact 67 and sintered to sinter together the second green compact 74, the second green compact 74 the groove (second refrigerant passage 114 grooved) The second refrigerant passage 114 can be formed by forming and closing the opening of the groove with the first powder compact 67. Since the groove of the second green compact 74 is open before superposition, it can be easily formed in the second green compact 74.

  As the milling process is performed, the temperature of the body 110 increases. However, since tungsten constituting the body 110 has a much higher thermal conductivity than steel, heat is quickly absorbed by the refrigerant flowing through the second refrigerant passage 114. As a result, the temperature rise of the body 110 is suppressed.

As described above, the sintered product of the present invention, nesting and forming a combustion chamber of the cylinder head, is suitable to the face milling body, be other mold nest and other cutting tools Also good. Therefore , the use of the sintered product is arbitrary.

However, while high performance of the internal combustion engine is required, it is strongly required to improve the dimensional accuracy of the combustion chamber. In this respect, the sintered product of the present invention, compared to other applications, it can be said to be optimal nest mounting the mold for casting the cylinder head. Such nesting can include partial molds and cores.

  Further, the cutting tool may be a drill, a reamer, an end mill or the like in addition to a face mill. However, the present invention is more effective for a front milling machine in which the body has a larger diameter than the shank and the refrigerant passage provided in the body is necessarily complicated.

  In the examples, tungsten powder and nickel powder were prepared, respectively, but tungsten powder in which tungsten particles are coated (or adhered) with nickel may be used. In this case, only tungsten powder (nickel-attached tungsten particles) is charged into the first mold 60 in FIG. The same applies to FIG.

Carbon steel (Fe) has a melting point of 1540 ° C. and a thermal conductivity of about 50 W / (m · K).
On the other hand, tungsten has a melting point of 3400 ° C. and a thermal conductivity of 177 W / (m · K).
Molybdenum has a melting point of 2620 ° C. and a thermal conductivity of 139 W / (m · K).
Tungsten carbide has a melting point of 2870 ° C. and a thermal conductivity of 84 W / (m · K).

The present inventors have, as a result of the prototype, molybdenum sinter and tungsten carbide sinter even higher thermal conductivity than steel, it was confirmed that strong corrosion.
Accordingly, and to obtain a molybdenum sinter by changing the tungsten powder to molybdenum powder, tungsten powder may be obtained the tungsten carbide by de sinter by changing the tungsten carbide powder.

  The present invention is suitable for nesting attached to a mold for casting a cylinder head.

DESCRIPTION OF SYMBOLS 12 ... Cylinder head, 31 ... Combustion chamber, 60 ... 1st shaping | molding die, 64 ... Powder (metal mixed powder) which uses tungsten as a main material, 65 ... Tungsten powder, 67 ... 1st compacting body, 68, 113 ... Refrigerant passage (first refrigerant passage), 68c ... straight bottom, 70 ... second molding die, 74 ... second powder compact, 75, 114 ... refrigerant passage (second refrigerant passage), 78 ... superposed body, 80 ... Sintering furnace, 90 : sintered product (nested), 93: central axis, 94: orthogonal axis, 110 : sintered product (body), 208: boundary layer.

Claims (3)

A preparation step of preparing a powder mainly composed of at least one of tungsten, molybdenum, and tungsten carbide, a first mold, a second mold, and a sintering furnace;
A first molding step in which the powder is charged into the first mold and pressed to obtain a first compact;
A step of forming a first refrigerant passage for allowing the refrigerant to flow through the obtained first green compact,
A second molding step in which the powder is charged into the second mold and pressed to obtain a second compact.
Forming a second refrigerant passage for allowing the refrigerant to flow through the obtained second green compact,
Obtaining a superimposed body by combining the first powder compact with the second powder compact so that the first refrigerant passage is connected to the second refrigerant passage;
It obtained the steps of the piled body obtained sintered product to by liquid phase sintering in the sintering furnace, the production method of the sintered article Ru Tona. Tungsten, molybdenum, a sintered product shall be the main component at least one tungsten carbide,
It has a refrigerant passage inside, and some of the refrigerant passages have a cross-sectional shape combining a straight bottom and an inverted U-shaped wall, and the straight bottom is the central axis of the sintered product. sinter you characterized in that extending along the orthogonal line orthogonal. A second aspect sintered article according,
The refrigerant passage, sinter you being a spiral refrigerant passage.

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