JPH08233103A - Heat resistant split elastic ring - Google Patents

Abstract

PURPOSE: To reduce the tension reduction even in a thermal ambiance, to give an excellent heat-resisting property, and to realize a light weight, by composing a heat-resisting split pattern elastic ring with a TiAl system metal compound, and specifying the volume integral ratio of the layer form, organizations in a metal organization. CONSTITUTION: This heat-resisting split pattern elastic ring 1 is composed of a TiAl system metal compound, and its metal organization has a circular main area A1 extending from the ring inner peripheral surface 3 to the ring outer peripheral surface 4 side, and a circular outer periphery area A2 existing at the outer periphery side. In the main area A1 and the outer periphery area A2 , numerous layer form organizations L exist, and they have a structure laminating the α2 phases and the γ phases alternatively. And the volume integral ratio of the layer form organizations L in the metal organization is set 10% or more. Consequently, an excellent heat-resisting property is obtained resulting from the quality of the TiAl system metal compound, and a light weight is realized. And by setting the volume integral ratio, the piston ring 1 exercises an excellent self tension maintaining function in the thermal ambiance of about 30 deg.C, and the tension reduction is made smaller.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-resistant split elastic ring. For example, a piston ring for an internal combustion engine corresponds to this split elastic ring.

[0002]

2. Description of the Related Art A conventional piston ring for an internal combustion engine is made of steel, cast iron, etc.
148612). This is because the material is inexpensive, has a high Young's modulus, and has excellent room-temperature bending strength.

[0003]

Currently, in automobile internal combustion engines, high output and high load are progressing, and under such circumstances, the piston ring is exposed to a thermal environment of about 300 ° C. become. However, the conventional piston ring has a remarkable decrease in tension under the above-mentioned thermal environment, and an urgent improvement has been desired in this respect.

In view of the above, the present invention has excellent heat resistance, so that the tension loss is small even under the above-mentioned thermal environment, the weight is light, and the split elastic ring is optimal as a piston ring. The purpose is to provide.

[0005]

A heat-resistant split elastic ring according to the present invention is composed of a TiAl-based intermetallic compound and has a volume fraction Vf of a layered structure in a metal structure of Vf ≧.
It is characterized by being 10%.

[0006]

The split elastic ring made of a TiAl-based intermetallic compound has excellent heat resistance due to its material and is lightweight. Then, the volume fraction Vf of the layered tissue
When the above is set as described above, the split elastic ring exerts an excellent self-tension maintaining ability in a thermal environment of about 300 ° C., so that the tension decrease is small.

However, the volume fraction Vf of the layered tissue is Vf <
At 10%, the tension loss of the split elastic ring in the thermal environment becomes large.

[0008]

1 and 2, an inside bevel piston ring 1 for an internal combustion engine as a heat-resistant split elastic ring is made of a TiAl-based intermetallic compound, and a solid line shows a true circular shape when used. The chain line shows each free-time shape that is a substantially elliptical shape. In the figure, reference numeral 2 indicates a gap.

3 (a) and 3 (b) show two types of metal structures in the piston ring 1.

The metallographic structure shown in FIG. 3 (a) has an annular main region A ₁ extending from the ring inner peripheral surface 3 to the ring outer peripheral surface 4 side.
And an annular outer peripheral area A ₂ existing on the outer peripheral side of the main area A ₁ . The main region A ₁ is composed of a large number of equiaxed crystals E, and the outer peripheral region A ₂ is composed of a large number of columnar crystals C grown from the ring outer peripheral surface 4 toward the main region A ₁ .

A large number of layered structures L are present in the main region A ₁ and the outer peripheral region A ₂ , and each layered structure L usually alternates between α ₂ phase (Ti ₃ Al phase) and γ phase (TiAl phase). It has a laminated structure. In the main region A ₁ , the layered structure L takes the form of equiaxed crystals, and the remaining equiaxed crystals are mainly γ equiaxed crystals Eγ. In the outer peripheral region A ₂ , the layered structure L is divided into one that constitutes the entire columnar crystal C and one that constitutes the portion of the columnar crystal C. In the columnar crystal C having the layered structure L, the portion other than the structure L is mainly the γ phase.

The volume fraction Vf of the layered structure L in such a metal structure is Vf ≧ 10% (including Vf = 100%).
Is set to

As described above, the piston ring 1 made of the TiAl-based intermetallic compound has excellent heat resistance due to its material and is lightweight. Then, when the volume fraction Vf of the layered tissue L is set as described above, it is 300
In a thermal environment of about ° C, the piston ring 1 exerts an excellent self-tension-maintaining ability, so that the decrease in tension is small.

The metallographic structure shown in FIG. 3B has the above-mentioned main region A.
Similar to _1, it is composed of many equiaxed crystals E. Therefore, in the metal structure, a large number of layered structures L exist in the form of equiaxed crystals, and the remaining equiaxed crystals are mainly γ equiaxed crystals Eγ.

The volume fraction Vf of the layered structure L in the metal structure is Vf in the same manner as described above in order to obtain the above effect.
≧ 10% (including Vf = 100%) is set.

In manufacturing the piston ring 1, FIG.
The cylindrical casting 5 shown in (1) is subjected to a ring-slicing process to collect the annular material 6, and then the annular material 6 is subjected to predetermined machining and heat treatment to obtain the piston ring 1 having a free-time shape.

In FIG. 5, the horizontal centrifugal casting apparatus 7 used for casting the tubular casting 5 comprises a tubular mold 8. The mold 8 is made of pure copper, has a cylindrical body 10 having a molten metal inlet 9 at one end and the other end closed,
It is composed of a mounting flange 11 provided on the outer peripheral surface of the closing side. The mold 8 is fixed to a rotary disk 12 through a mounting flange 11 with its axis a substantially horizontal, and a rotary shaft 13 protruding from the rotary disk 12 is connected to a motor (not shown).
The cylindrical main body 10 has a cylindrical cavity 14 continuous with the injection port 9, and the inner peripheral shape of its cross section is formed into a perfect circle.
The tip of the injection box 15 is inserted into and removed from the injection port 9, and the molten metal is injected into the cavity 14.

Hereinafter, a production example of the piston ring 1, its performance and a metal structure will be specifically described. [Example I] Table 1 shows 5 for obtaining a TiAl-based intermetallic compound.
The following is an example of blending different types of melting materials. In each melting material, the compounding amounts of V, Nb and B are constant, and the compounding amounts of Al and Ti are changed.

[0019]

[Table 1]

In the mold 8, the inner diameter of the cavity 14 was set to 90 mm and the length was set to 200 mm, and the mold 8 and the high frequency induction furnace equipped with the water-cooled copper crucible were both installed in the decompression chamber. (A) 2.5 kg of melting material Example 1 was put into a water-cooled copper crucible, and then the air pressure in the decompression chamber was adjusted to about 10 ⁻³ Torr.
Then, the pressure in the decompression chamber was replaced with 200 Torr in order to prevent evaporation of the Al component. (B) Induction melting was performed under the condition that the melting output was 125 kW and the material was melted down and then held for 5 minutes to prepare a molten metal having a TiAl-based intermetallic compound composition. (C) Mold temperature about 25 ℃ (normal temperature), rotation speed 600rpm
Rotate the mold 8 under the conditions of, and the hot water temperature is about 1600 ℃, 2.2
Pour kg molten metal into the cavity 14 from the pouring box 15,
Thereafter, the mold 8 was rotated for 4 minutes to cast the tubular casting 5. (D) The cylindrical casting 5 was left standing as it was for 30 minutes after the rotation of the die 8 was stopped, the inside of the decompression chamber was opened to the atmosphere, and then the cylindrical casting 5 was released from the die 8. The cylindrical casting 5 has an outer diameter of 90 mm, a wall thickness of 8.5 mm, and a length of 20.
It was 0 mm.

Then, the tubular casting 5 was cast at 1300.degree.
A hot isostatic pressing process (HIP) was performed for 5 hours at 2000 atmospheric pressure to densify the metal structure.

Then, Example 1 of the free-time piston ring 1 was obtained through the following machining process and heat treatment. That is, the tubular casting 5 was sequentially subjected to round-slicing, free-form cutting, upper and lower surface finishing, outer peripheral barreling, inside bevel cutting, gap adjustment processing, and strain relief annealing.

As shown in FIGS. 1 and 2, the piston ring 1
In Example 1, the nominal diameter D is D = 81 mm, and the width B is B = 1.
The thickness is 2 mm and the thickness T is T = 3.1 mm.

The same centrifugal casting method as described above was performed using Examples 2 to 5 of melting materials, and then the same hot isostatic pressing treatment, machining and heat treatment were sequentially performed as in Example 1 of the piston ring 1. Examples 2-5 of piston ring 1 having similar dimensions were obtained. Examples 2 to 5 are examples 2 of melting materials.
It corresponds to the case of using ~ 5.

Next, the following tension reduction tests were conducted on Examples 1 to 5 of the piston ring 1, and the volume fraction Vf of the layered structure L in the metal structure was determined. The results shown in Table 2 were obtained.

The tension reduction test is conducted by using the piston ring 1 of Example 1.
The initial tension was measured with respect to 5 and then Examples 1 to 5 were mounted on a piston and the piston was incorporated into the cylinder sleeve of the engine. After that, the piston and the like were held under heating at 300 ° C. for 100 hours, and after the holding. The tension was measured after the test of Examples 1 to 5.

The area fraction is used as the volume fraction Vf of the lamellar structure L, and the area fraction is observed by backscattered electron composition images of Examples 1 to 5 of the piston ring 1 and then image processed. Was asked to do so.

Table 2 also shows data on steel piston rings currently mass-produced as Example 6 of piston rings.

[0029]

[Table 2]

Examples 1 to 5 were provided with the metallographic structure shown in FIG. 3A, and the ratio of the outer peripheral area A ₂ was about 10%. FIG. 6 is a micrograph showing the metal structure of the outer peripheral region A ₂ in Example 1, and it can be seen from FIG. 6 that a plurality of columnar crystals having the layered structure L are present.

As is clear from Table 2, as in Examples 1 to 3, when a TiAl intermetallic compound is used as the constituent material and the volume fraction Vf of the layered structure L is set to Vf ≧ 10%, 3
Decrease the tension decrease rate in a thermal environment of 00 ° C by Vf <10%
4 or 5 and Example 6 of the mass-produced steel piston ring can be significantly lower or even zero.
In this case, the volume fraction Vf of the layered tissue L is preferably Vf ≧ 90%. [Example II] Using Examples 1 to 5 of the melting material shown in Table 1,
Example I except that the inner diameter of the cavity 14 in the die 8 was set to 100 mm, the preheating temperature of the die 8 was set to 130 ° C., and the molten metal injection amount into the cavity 14 was set to 4 kg.
Performed the same centrifugal casting method as above, but with an outer diameter of 100 mm and a wall thickness of 14
mm, and a length of 200 mm, 5 kinds of tubular castings 5 are cast, and then each of the tubular castings 5 is subjected to the hot isostatic pressing treatment similar to the above, and thereafter, the same machining and heat treatment are sequentially performed. , Examples 1a to 5a of the piston ring 1 having dimensions similar to those of the example 1 of the piston ring 1 were obtained. Example 1 of these
a to 5a respectively correspond to the cases of using Examples 1 to 5 of the melting material.

Next, the tension reduction tests similar to the above were performed on the piston rings 1 of Examples 1a to 5a, and the volume fraction Vf of the layered structure L in the metal structure was determined by the same method as described above. Got It should be noted that Table 3 also shows data on mass-produced steel piston rings as Example 6 of piston rings.

[0033]

[Table 3]

Examples 1a-5a had the metallurgical structure shown in FIG. 3 (b). FIG. 7 is a micrograph showing the metal structure of Example 1a, and it can be seen from FIG. 7 that a large number of layered structures L in the form of equiaxed crystals are uniformly dispersed.

As is clear from Table 3, when the TiAl intermetallic compound is used as the constituent material and the volume fraction Vf of the layered structure L is set to Vf ≧ 10% as in Examples 1a to 3a.
The tension decrease rate in a thermal environment of 300 ° C. is Vf <10.
% Examples 4a, 5a and mass-produced steel piston ring Example 6
It can be lower than. In this case, the layered structure L
The volume fraction Vf of is preferably Vf ≧ 85%.

FIG. 8 shows examples 1 to 6 and example 1 of the piston ring 1.
4 is a graph showing the relationship between the volume fraction Vf of the layered tissue L and the tension decline rate for a to 5a based on Tables 2 and 3. In the figure, points (1) to (6) and (1a) to (5a) correspond to Examples 1 to 6 and 1a to 5a, respectively.

From FIG. 8, it can be seen that the piston ring 1 according to Example I has a lower rate of tension decrease than the piston ring 1 according to Example II. From this, it can be said that the piston ring 1 should have the metal structure having the columnar crystals C shown in FIG. 3A.

Next, the example 1 of the piston ring 1 is incorporated as a top ring into a 4-cylinder DOHC engine having a displacement of 1600 cc, and the engine is rotated at an engine speed of 2000.
The run-in operation was carried out at ˜6000 rpm for a total of 3 hours, and then the blow-by gas amount was measured. The blow-by gas amount at this time is an initial value. Then, an endurance test was conducted in which the engine was continuously operated for 100 hours under a full load condition of an engine speed of 8000 rpm, and then the blow-by gas amount in the full load condition (8000 rpm) was measured. The blow-by gas amount at this time is the value after the endurance.

For the piston ring examples 1a and 6 as well, the initial value and the endurance value of the blow-by gas amount were measured by the same method as described above. Table 4 shows the measurement results.

[0040]

[Table 4]

As is clear from Table 4, the blow-by gas amount has an initial value of Example 6 for mass-produced steel piston rings.
However, the value after endurance is significantly lower in the case of using Examples 1 and 1a than in the case of using Example 6, and is 20 liter / min or less. This is because Examples 1 and 1a have a lower rate of decrease in tension than Example 6. For the same reason, the value after endurance is lower when Example 1 is used than when Example 1a is used.

In the TiAl-based intermetallic compounds of the present invention, V in Examples 1 to 3 of Table 1 is a transition metal such as Cr and Mn, Nb is a heavy metal such as Ta, W, Mo and Hf, and B. Are substituted with low specific gravity elements such as C, N and Si, the combinations of these elements are changed, and the TiAl binary system is included.

The split elastic ring according to the present invention can be used not only as a piston ring but also as a stop ring fitted in an annular groove on the inner peripheral surface of the shaft hole.

[0044]

According to the present invention, by virtue of the constitution as described above, it has excellent heat resistance and is lightweight,
It is possible to provide a split elastic ring having a small tension decrease even in a thermal environment.

[Brief description of drawings]

FIG. 1 is a plan view of a piston ring.

FIG. 2 is a cutaway side view of a main part of a piston ring.

FIG. 3 is an explanatory view showing two kinds of metal structures in a piston ring.

FIG. 4 is a perspective view of a tubular casting.

FIG. 5 is a vertical sectional front view of a main part of a horizontal centrifugal casting apparatus.

FIG. 6 is a micrograph showing an example of a metal structure of a piston ring.

FIG. 7 is a micrograph showing another example of the metal structure of the piston ring.

FIG. 8 is a graph showing the relationship between the volume fraction Vf of the layered tissue and the tension decline rate.

[Explanation of symbols]

1 Piston ring 3 Ring inner peripheral surface 4 Ring outer peripheral surface A ₁ Main area A ₂ Outer peripheral area C Columnar crystal E Equiaxed crystal L Layered structure

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Nakagawa 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Yuichi Ienaga 1-4-1 Chuo, Wako-shi, Saitama Stock Company Honda Technical Research Institute

Claims (4)

[Claims] 1. A TiAl-based intermetallic compound,
The volume fraction Vf of the layered structure (L) in the metal structure is Vf
A heat-resistant split elastic ring, characterized in that ≧ 10%. 2. The ring-shaped main region (A ₁ ) extending from the ring inner peripheral surface (3) to the ring outer peripheral surface (4) side.
If, has its annular peripheral region existing on the outer peripheral side of the main area _{(A 1) (A 2)} , said main region (A ₁₎ is composed of a number of equiaxed (E), also the outer peripheral region (a ₂₎ is composed of a number of columnar crystals grown toward the main area than the ring outer peripheral surface _{(4) (a 1) (} C), said layered tissue (L) of said main area (a ₁₎ and The heat resistant split elastic ring according to claim 1, which is present in the outer peripheral region (A ₂ ). 3. The heat-resistant split elastic ring according to claim 1, wherein the metal structure is composed of a large number of equiaxed crystals (E). 4. The heat-resistant split elastic ring according to claim 1, which is a piston ring (1) for an internal combustion engine.