JP2003001366A - Manufacturing method for hollow member made of titanium-based composite material and for hollow valve made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method where the hollow part of a hollow member is easily formed of a titanium-based composite material by cutting work. SOLUTION: The manufacturing method for the hollow member made of a titanium-based composite material comprises the following processes: a forging process for forging the forging material (8) that has an outer peripheral layer (81) made of a titanium-based composite material whose matrix, in which reinforced particles are dispersed, is mainly constituted of titanium and that has an inner peripheral layer (82) which is arranged inside the outer peripheral layer and which is made of a free-cutting titanium material having more excellent machinability than the titanium-based composite material; and a hollow-part forming process for forming a hollow part (101) by cutting the inner peripheral layer of the forging material that is obtained from the forging process. Since the inner peripheral layer is made of the free-cutting titanium material, the hollow part is easily formed by cutting.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a hollow member or a hollow valve made of a titanium-based composite material.

[0002]

2. Description of the Related Art In order to improve the performance of various devices and save energy, it is required to reduce the weight of various members. In order to reduce the weight, it is effective to change the material and shape of the members. The weight of the member can be reduced by changing the material of the member from steel to a light alloy such as an aluminum alloy or a titanium alloy. To further secure the strength and rigidity of the member, a composite material in which reinforcing particles are dispersed in a light alloy matrix is also used. Further, the weight of the member can be reduced by changing the shape of the member, for example, downsizing the member or making it hollow. However, the external dimensions of the mechanical structural member and the like are almost determined from the viewpoint of strength and rigidity. Therefore, it is not easy to reduce the size of the member itself.
Therefore, hollowing by thinning the inner side, which exerts less stress, is generally performed and effective as a weight reduction of the member.

Under these circumstances, it is highly preferable to use a hollow member made of a titanium-based composite material because it is possible not only to reduce the weight but also to increase the strength and rigidity of the member in a high degree. However, in the case of a titanium-based composite material, it is difficult to form a hollow member by a normal cutting process because of its poor workability. Therefore, for example, JP-A-2000-15386 and JP-A-6-63831 propose methods for easily manufacturing a hollow member.

[0004]

According to the former publication,
Crude material for melting (sintered titanium alloy: Ti-6Al-
A core made of a metal material (copper alloy) lower than 4 V) and higher than the forging temperature is inserted into the hollow portion of the rough forging material that has been formed in advance. A method for manufacturing a hollow member is disclosed in which the hollow core is formed by forging it and then heating the whole to elute the core. But with this method,
When the core is eluted, Ti easily reacts with Cu,
Form a brittle compound layer. In the case of hollow members made of titanium-based composite material, strict mechanical properties require
For example, it is not preferable to form such a fragile compound layer even on the inner peripheral side.

According to the latter publication, a small-diameter guide hole is formed by a YAG laser prior to deep hole machining of a difficult-to-cut material. After that, a deep hole drilling method for a difficult-to-cut material is disclosed in which a drill hole is drilled along the guide hole. However, in this method, since the laser processing is performed, the cost of processing the guide hole becomes high. Further, when the difficult-to-cut material is melted by the YAG laser, the difficult-to-cut material undergoes a structural change, which causes a decrease in strength. Further, in the publication, since the material which is difficult to cut is only heat resistant steel (SUH), such drilling is possible. However, when it is a titanium-based composite material, it is difficult to drill holes even if the guide holes are formed.

By the way, it is possible to obtain a hollow material by providing a core with a molding die and performing powder molding or the like. However, if the hollow material is forged as it is, the hollow portion is crushed, and eventually the desired hollow member cannot be obtained. Of course, the hollow material is inferior in strength and cannot be used as it is.

The present invention has been made in view of such circumstances. That is, the present invention provides a manufacturing method capable of easily manufacturing a hollow member made of a titanium-based composite material that is difficult to cut. Moreover, it aims at providing the manufacturing method of the hollow valve which consists of titanium group composite materials as an example of the hollow member.

[0008]

Therefore, the present inventor has diligently studied to solve this problem, and as a result of repeated trial and error,
A free-cutting titanium-based material, which has better machinability than titanium-based composite materials, is used as the inner peripheral layer, and a titanium-based composite material is used as the outer peripheral layer. Completed the invention. (Method of Manufacturing Hollow Member) That is, the hollow member made of the titanium-based composite material of the present invention includes an outer peripheral layer made of a titanium-based composite material in which reinforcing particles are dispersed in a matrix containing titanium as a main component, and an inner side of the outer peripheral layer. A forging step of forging a forging material having an inner peripheral layer made of a free-cutting titanium-based material, which is disposed in the above and has better machinability than the titanium-based composite material; and a forging material obtained after the forging step. A hollow portion forming step of forming a hollow portion by cutting the inner peripheral layer side.

In the manufacturing method of the present invention, a forging step is performed using a forging material in which the outer peripheral layer is made of a titanium-based composite material having high strength and the inner peripheral layer is made of a free-cutting titanium-based material excellent in machinability. I do. In this case, the free-cutting titanium-based material having relatively excellent machinability remains on the inner peripheral layer side of the obtained forged material. Since the inner peripheral layer side is easier to cut as compared with the case of processing a titanium-based composite material, it is easy to form a hollow portion. Further, the finished surface roughness can be improved by honing or the like.

Since a free-cutting titanium-based material having the same main component (Ti) as the matrix of the titanium-based composite material constituting the outer peripheral layer is used for the inner peripheral layer, hot forging, heat treatment, etc. are performed and the hollow member is made. Even when used at a high temperature, a fragile compound layer is rarely formed between the inner peripheral layer (or the inner peripheral layer remaining after cutting) and the outer peripheral layer. The outer peripheral layer of the forging material does not need to completely surround (enclose) the inner peripheral layer. Rather, in the hollow portion forming step, it is preferable that a part of the inner peripheral layer is exposed at a portion where the cutting process is started. "Forging" referred to in the present specification is from 300 to
Hot forging at 1700 ° C is preferable, and the types of forging include
Mold forging, extrusion, upsetting, wire drawing, free forging, swaging, rolling, etc.

(Method for Manufacturing Hollow Valve) The present inventor has further developed a manufacturing method suitable for manufacturing a hollow valve, which is an example of the hollow member, and completed the present invention. That is, the method for producing a hollow valve made of a titanium-based composite material of the present invention is provided with an outer peripheral layer made of a titanium-based composite material in which reinforcing particles are dispersed in a matrix containing titanium as a main component, and an inner layer of the outer peripheral layer. A shaft portion forming step of forming a shaft portion by hot extruding a forging material having an inner peripheral layer made of a free-cutting titanium-based material, which has better machinability than the titanium-based composite material, and the forging material. Umbrella part forming step of forming an umbrella part by upsetting forging, and the hollow part by axially cutting the inner peripheral layer side of the valve material obtained after the shaft part forming step and / or the umbrella part forming step. And a hollow portion forming step of forming a portion.

In the case of the present invention, the forging process described above is made into a more specific shaft forming process and umbrella forming process. The shaft part forming process and the umbrella part forming process may be preceded.
Then, a desired hollow portion is formed by axially cutting the inner peripheral layer side of the thus obtained valve material in the hollow portion forming step. The processing direction of the hollow portion forming step may be from the shaft end portion (stem end) side or the umbrella portion (valve) side.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to embodiments. (1) Forging material The forging material is composed of an outer peripheral layer of a titanium-based composite material and an inner peripheral layer of a free-cutting titanium-based material having excellent machinability. The titanium-based composite material is composed of a matrix containing titanium as a main component and reinforcing particles dispersed in the matrix. The matrix may be pure titanium, but it is preferable to select a titanium alloy having an appropriate composition depending on the strength, rigidity, etc. required of the hollow member. The reinforcing particles include TiB,
One or more of TiB ₂ , TiC, TiN, etc. may be used.
The combination of the matrix and the reinforcing particles, the compounding ratio, etc.
It is appropriately selected in consideration of desired mechanical properties, high temperature stability, hot workability and the like. The titanium-based composite material may be a matrix in which separately prepared reinforcing particles are mixed and dispersed, or Ti and B may be reacted with a reinforcing element in a sintering step or a heating step to precipitate the reinforcing particles. It can be a stuff.

The free-cutting titanium-based material is superior to the titanium-based composite material in machinability and contains titanium as a main component. It does not have to have the same composition as the matrix of the titanium-based composite material. Rather, pure titanium, Ti-3Al-2V + sulfide, etc., which are more excellent in machinability, are preferable as the free-cutting titanium-based material.

The forging material is obtained, for example, by a material forming step in which at least a part of the core made of the free-cutting titanium-based material is surrounded by the titanium-based composite material. This core forms the inner peripheral layer, and the titanium-based composite material surrounding it forms the outer peripheral layer.

More specifically, for example, a core made of a free-cutting titanium-based material is molded (core molding step), the core is placed in a mold, and a titanium-based composite material is formed in the formed cavity. A powder compact obtained by filling the composition powder of (1) (filling process) and press-molding (forming process) may be used as a forging material. Further, a sintered material obtained by sintering the powder compact may be used as a forging material (sintering step). Further, a mold is prepared in place of the molding die, the raw material of the titanium-based composite material is melted (melting process), and the molten metal is poured into the mold and cast (casting process) for forging. Good as a material.
In any case, it is advisable to select a material forming process suitable for the desired form of the forging material.

It is preferable that the material forming step includes a coating step of forming a coating layer having at least lubricity on a boundary between the outer peripheral layer and the inner peripheral layer.
When the forging material including the outer peripheral layer and the inner peripheral layer has a coating layer having at least lubricity between both layers, the material flow (plastic flow) of each layer is improved in the forging step,
A uniform forged material can be obtained. For example, when the material for forging is hot extruded, a uniform forged material having the extrusion ratio in which the diameters of the outer peripheral layer and the inner peripheral layer are substantially set can be obtained.

It is preferable that the coating layer further suppresses reaction and seizure between the two layers at high temperature to ensure lubricity. This is because hot forging is often used as the forging step. As such a coating layer, for example, an h-BN layer (hexagonal boron nitride), Zr
There is O ₂ etc. Specifically, the coating step can be performed by applying a treatment agent (spray method, brush coating method) or dipping (dip method) to the outer surface of the inner peripheral layer or the inner surface of the outer peripheral layer.

(2) Hollow portion forming step The hollow portion forming step is a step of forming a hollow portion by cutting the inner peripheral layer side of the forged material. This cutting process includes a hole process using a drill, a groove process using an end mill, a lightening process, and the like. (3) Manufacturing Method of Hollow Valve According to the manufacturing method of the present invention, the hollow portion of the valve is formed by cutting with a drill or the like. Therefore, at least one end side of the valve material has an opening. In a normal valve, it is common to close the opening. Therefore, it is preferable to further include a joining step of joining a lid to the opening of the hollow portion after the hollow portion forming step.

Particularly, it is preferable that the lid is made of a titanium-based material having substantially the same composition as that of the matrix. It is possible to suppress or prevent the formation of a fragile compound layer near the boundary. Also, when joining the lids by welding, the weldability is improved. For welding, for example,
Laser welding or the like can be used.

Further, it is preferable that the manufacturing method of the present invention includes a heat treatment step of subjecting the valve material to a heat treatment comprising a solution treatment and an aging treatment. By performing the heat treatment, the strength, fatigue resistance and heat resistance of the valve can be improved. Solution treatment is, for example, 1050 to 130.
After heating at 0 ° C. for 5 to 30 minutes, rapid cooling such as water cooling can be performed. The aging treatment can be carried out by holding it at 480 ° C. or higher for 1 to 5 hours and then allowing it to cool. Of course, the heat treatment conditions vary depending on the composition of the titanium-based composite material, desired mechanical properties, and the like.

Further, it is preferable to include a straightening step for straightening the bending of the shaft portion. This is because the squareness of the shaft portion with respect to the umbrella portion is strictly regulated in order to open and close the intake and exhaust holes of the engine with high accuracy. In particular, it is efficient to perform the straightening step at the same temperature as the aging treatment in combination with the aging treatment or after the aging treatment. The hollow valve obtained through the above-described steps according to the present invention is not only made lighter by the material itself, but also made lighter by providing a hollow portion in terms of shape. As a result, the reciprocating inertial mass around the valve is reduced, so that the friction loss due to the reduction of the spring load can be reduced and the engine speed can be further increased.

[0023]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. Below, a hollow valve is taken as the hollow member, and a method for manufacturing a hollow valve made of a titanium-based composite material will be described. (Example) (1) Example 1 Manufacturing of Forging Material (Material Forming Step) (a) First, a core 3 which is an inner peripheral layer of the forging material according to the present invention was manufactured. This state is shown in FIG. The core 3 is a cylindrical powder compact made of pure titanium powder (free-cutting titanium-based material), and was manufactured as follows. Average particle size 80μm
Of the comparatively coarse pure titanium powder 2 is filled in a rubber mold 1 (FIG. 1A) having a cylindrical cavity with a bottom, which is a molding die (first filling step: FIG. 2B), and 294 MPa. CIP molding with pressure (first molding step: same figure (c)), φ9 ×
A 30 mm columnar powder compact was obtained. The rubber mold 1
A cylindrical protrusion 11 slightly protrudes from the bottom of the core 3, and a recess for positioning is formed at one end of the core 3.

(B) h-BN (2%) having an average particle size of 5 μm
Is immersed in a bath 4 of a solution in which is dispersed in a solvent (ethanol (or alternative Freon)) and then pulled up,
A coating layer 31 of h-BN was formed on the surface of the core 3 (coating step). This state is shown in FIG.

(C) Next, a material compact 7 having a powder compact as an outer peripheral layer of the forging material formed around the core 3 was produced. This state is shown in FIG. As a mold,
A rubber mold 5 having a bottomed cylindrical cavity shown in (a) was used. The cavity is formed by inserting the concave portion of the core 3 into a positioning protrusion 51 slightly protruding from the central bottom portion of the rubber mold 5. Pure titanium powder (average particle size 25 μm) and Al were placed in the bottomed cylindrical cavity.
-40% V powder (average particle size 10 μm) and Fe-50% M
A mixed powder of o powder (average particle size 10 μm) and TiB ₂ powder (average particle size 4 μm) was filled (second filling step: FIG. 2B). The composition of the entire mixed powder is Ti-3Al-
2V-1Fe-1Mo-1.8B. After that, CIP molding at 294 MPa, φ19 × 50 m
A columnar raw material molded body 7 of m was obtained (second molding step: FIG. 7C).

Further, the material compact 7 is sintered in a vacuum atmosphere at 1300 ° C. for 4 hours (sintering step) to form a forging billet 8 having a two-layer structure including an outer peripheral layer 81 and an inner peripheral layer 82. It was obtained ((d) of the same figure). The forging billet 8 corresponds to the forging material in the present invention.

Forging Step (Shaft Forming Step, Umbrella Forming Step) The obtained forging billet 8 (φ17 × 45 mm) is heated to 1150 ° C. by a high frequency induction heating device and hot forged to form the valve material 9. Obtained. This state is shown in FIG.
Specifically, first, hot extrusion processing (extrusion ratio: 7.
5), the shaft portion 91 (φ6.5 mm × 100 mm) was formed (shaft portion forming step: FIG. 7A). Next, the extruded material obtained by this hot extrusion processing is upset to 80%.
Upset forging (umbrella forging) is performed to form the umbrella portion 92, and the valve material 9 is a forged material (umbrella diameter φ40 × 5 mm).
And

Heat Treatment Step and Straightening Step This valve material 9 was held at 1100 ° C. for 15 minutes for solution treatment, and then rapidly cooled (water cooled) for solution treatment. Then, it hold | maintained at 500 degreeC for 4 hours, and performed the aging treatment.
Immediately after that, the shaft portion was straightened at a temperature of 500 ° C., which is the same as the aging temperature (straightening step).

Hollow Portion Forming Step Further, a hollow valve material 10 having a hollow portion 101 is manufactured by subjecting the valve material 9 to a straight hole drilling with a diameter of 2.5 mm and a depth of 85 mm using a carbide drill 40. It did (hollow part formation process). This state is shown in FIG.

Joining process Opening 1 formed in hollow valve material 10 after drilling
02, the lid 20 was welded with an electron beam (joining step) to form a hollow valve 30. This state is shown in FIG.
The lid 20 is a round bar made of the same material as the matrix. After that, the hollow valve 30 is assembled into the engine by appropriately finishing the outer peripheral surface of the shaft portion (stem), the end surface of the stem end, and the face surface.

(2) Example 2 In this example, a core 230 made of a sintered body was used instead of the core 3 made of the powder compact of Example 1. The core 230 is obtained by sintering a powder compact having the same shape as the core 3 in a vacuum atmosphere at 1300 ° C. for 4 hours (first).
Sintering process). The same h-BN solution as in Example 1 was sprayed onto the surface of the core 230 to form a coating layer of h-BN. This state is shown in FIG. The subsequent steps are the same as in Example 1. Thus, the hollow valve according to Example 2 was manufactured. However, the molding pressure when the molded body of the forging material (corresponding to the material molded body 7) was CIP-molded was 392 MPa.

(3) Example 3 In this example, first, a sintered forged material 340, which is an outer peripheral layer of the forging material according to the present invention, was manufactured. This state is shown in FIG. The sintered forged material 340 was manufactured as follows. The mixed powder 320 having the same composition as in Example 1 was
A rubber mold 310 having a cavity of 80 × 150 mm ((a) in the same figure) was filled (FIG. (B) in the same figure) and 392
CIP molding was carried out at a pressure of MPa to obtain a powder compact 330 ((c) in the figure). The powder compact 330 is sintered at 1300 ° C. for 16 hours in a vacuum atmosphere to obtain φ60 × 150 m
A sintered body of m was obtained. The sintered body was heated to 1150 ° C. in an atmospheric furnace, hot forged to φ20 mm, naturally cooled, and then cut to a predetermined length to obtain a sintered forged material 340 (see FIG. d)).

Next, using this sintered forging material 340,
The billet 380 for forging was manufactured as follows. This state is shown in FIG. The sintered forging material 340 is machined to have an outer diameter of 17 mm, a length of 45 mm, and an inner diameter of 7 mm.
B. A cup-like shape having a depth of 40 mm was formed to form a hollow portion 341 ((b) of the same figure). Note that the machining here had a larger drilling diameter than the final product, and the hardness was low because the cooling rate was slow with forging as it was, so the machining was relatively easy. Pure titanium type 2 (JIS) round bar 330 (φ
6.9 × 40 mm: a free-cutting titanium-based material) was prepared, and a coating layer of h-BN was formed on the surface thereof by the spray method as in Example 2 (FIG. 10A). Hollow part 34
1 was inserted into the forging billet 380 ((c) in the figure). Therefore, the round bar 330 serves as the inner peripheral layer in the present invention. The subsequent steps are the same as in Example 1, and thus the hollow valve according to Example 3 was manufactured.

(Evaluation) The valve materials according to the above-mentioned three examples and the titanium-based composite material not having the two-layer structure (Example 1)
The machinability with a drill was evaluated for a valve material (comparative example) consisting only of (the same composition). As a result, in the case of the comparative example, the drill was broken when the hole was drilled to a depth of about 10 mm. On the other hand, in the case of the examples, any of the valve materials could be drilled to a desired depth without breaking the drill, and a desired hollow portion could be formed. As can be seen from this result, a hollow valve (hollow member) made of a titanium-based composite material can be obtained by using a valve material (forging material) having a free-cutting titanium-based material in the inner peripheral layer, which has excellent machinability. It has become possible to easily and efficiently manufacture.

[0035]

According to the manufacturing method of the present invention, the hollow member or the hollow portion of the hollow valve can be easily and efficiently formed from the titanium-based composite material by cutting.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing process of a core according to a first embodiment.

FIG. 2 is a schematic view showing a manufacturing process of the forging billet according to the first embodiment.

FIG. 3 is a schematic diagram showing a manufacturing process of the valve material according to the first embodiment.

FIG. 4 is a schematic view showing a hollow portion forming step according to Example 1.

FIG. 5 is a schematic diagram showing a joining step according to Example 1.

FIG. 6 is a schematic diagram showing a coating process according to Example 2.

FIG. 7 is a schematic diagram showing a manufacturing process of a sintered forged material according to a third embodiment.

FIG. 8 is a schematic view showing a manufacturing process of the forging billet according to the third embodiment.

[Explanation of symbols]

1 rubber mold 2 mixed powder 3 cores 31 coating layer 8 Billet for forging (material for forging) 81 outer layer 82 Inner layer 9 valve material 91 Shaft 92 Umbrella part 10 Hollow valve material 101 hollow 102 openings 20 lid 30 hollow valve

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) B22F 3/24 B22F 3/24 C F 5/00 5/00 S B23P 13/00 B23P 13/00 F01L 3/24 F01L 3/24 D (72) Inventor Kazuaki Nishino 1 A-41, Nagakute-cho, Aichi-gun, Aichi-gun 1-sided Yokomichi Toyota Central Research Institute Co., Ltd. F-term (reference) 4E087 AA10 BA05 BA26 CA22 CA31 CB01 CC01 DB04 DB14 DB24 HA69 HB03 4K018 AA06 AB02 FA01 FA02 FA08 JA02 KA10

Claims (7)

[Claims] 1. An outer peripheral layer made of a titanium-based composite material in which reinforcing particles are dispersed in a matrix containing titanium as a main component, and an outer layer disposed inside the outer peripheral layer and having better machinability than the titanium-based composite material. A forging step of forging a forging material having an inner peripheral layer made of a titanium-based material, and a hollow portion forming a hollow portion by cutting the inner peripheral layer side of the forged material obtained after the forging step A method for producing a hollow member made of a titanium-based composite material, comprising the steps of: 2. The titanium-based material according to claim 1, wherein the forging material is obtained by a material forming step of surrounding at least a part of a core made of the free-cutting titanium-based material with the titanium-based composite material. A method for manufacturing a hollow member made of a composite material. 3. The hollow member made of a titanium-based composite material according to claim 2, wherein the material forming step includes a coating step of forming a coating layer having at least lubricity on a boundary between the outer peripheral layer and the inner peripheral layer. Manufacturing method. 4. An outer peripheral layer made of a titanium-based composite material in which reinforcing particles are dispersed in a matrix containing titanium as a main component, and free-cutting disposed inside the outer peripheral layer and having excellent machinability than the titanium-based composite material. A shaft portion forming step of forming a shaft portion by hot extruding a forging material having an inner peripheral layer made of a titanium-based material, and an umbrella portion forming an umbrella portion by upsetting the forging material. A forming step, and a hollow portion forming step of axially cutting the inner peripheral layer side of the valve material obtained after the shaft portion forming step and / or the umbrella portion forming step to form a hollow portion. A method of manufacturing a hollow valve made of a titanium-based composite material, comprising: 5. The method for manufacturing a hollow valve made of a titanium-based composite material according to claim 4, further comprising a joining step of joining a lid to the opening of the hollow portion after the hollow portion forming step. 6. The method for producing a hollow valve made of a titanium-based composite material according to claim 4, further comprising a heat treatment step of subjecting the valve material to a heat treatment comprising a solution treatment and an aging treatment. 7. The method of manufacturing a hollow valve made of a titanium-based composite material according to claim 4, further comprising a straightening step of straightening the bending of the shaft portion.