JP3484076B2 - Piston ring for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a piston ring for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, piston rings for internal combustion engines are made of steel materials such as cast iron, Si-Cr steel, and martensite-based high chrome stainless steel. In order to improve sliding characteristics such as seizure resistance, adhesion resistance, and friction coefficient, hard chrome plating by electroplating on the outer peripheral surface has been used. However,
Along with the increase in the output of internal combustion engines, there has been a demand for piston rings having more excellent slidability, and nowadays, piston rings made of nitriding stainless steel containing high chromium have come to be used.

Further, a piston ring having a chromium nitride film formed by ion plating on its outer peripheral surface has also been used. Some piston rings whose main body is coated with a chromium nitride film by ion plating are proposed in the following patent publications or publications. (1) Japanese Patent Publication No. 6-10454: Metal Cr and Cr ₂
A film having an ultrafine mixed structure in which N is 1000 angstroms or less. (2) Japanese Patent Laid-Open No. 7-286260: Cr ₂ N-type chromium nitride-based coating film. (3) JP-A-7-286261: CrN and Cr ₂
A film whose main component is N-type chromium nitride.

For conventional piston rings such as cast iron, Si-Cr steel, and martensitic high-chromium stainless steel, the surface of which is plated with hard chrome, and stainless steel containing high chromium, which is subjected to nitriding treatment, are used. There are the following problems. 1) The piston ring is used by being mounted in the piston ring groove of an aluminum alloy piston. However, in a piston ring obtained by nitriding high chromium content stainless steel, the nitrided layer may wear the piston ring groove facing it. Many. 2) Si with an ion plating film formed on the outer peripheral surface
In a piston ring whose main body is -Cr steel or tool steel, a predetermined set tension cannot be obtained due to thermal settling of the piston ring due to temperature rise during ion plating. The base material temperature rise during ion plating can be suppressed by lowering the vapor deposition rate or lowering the base material preheating temperature, but this is not a good idea because it reduces the adhesion and productivity of the ion plating film. 3) The piston ring mainly composed of high chromium content stainless steel on which an ion plating film is formed without nitriding does not have the same heat set as Si-Cr steel and tool steel, but has a low surface hardness from the beginning. Therefore, the upper and lower surfaces of the piston ring tend to wear more.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the outer peripheral sliding surface and the upper and lower surfaces of the piston ring are excellent in wear resistance and the piston ring of the aluminum alloy piston is provided. The object is to provide a piston ring that is less likely to wear with the groove.

[0007]

The piston ring of the present invention can be used as a piston ring even when the temperature rises at the time of ion plating for forming a film as described in [0003] on at least the outer peripheral sliding surface. In order to make the piston ring material with high heat resistance that does not impair the function of
The steel composition of the following (1) and (2) is provided for the base material or the main body. (1) C: 0.35 to 0.45% by weight, Si: 1.
80 to 2.50%, Mn: 0.60% or less, Cr: 1
0.0-12.0%, Ni: 0.60% or less, Mo:
Chrome steel containing 0.70 to 1.30% and the balance Fe and unavoidable impurities. (2) C: 0.45 to 0.55% by weight, Si:
1.00 to 2.00%, Mn: 0.60% or less, Cr:
Chrome steel containing 7.50 to 9.50%, Ni: 0.6% or less, and the balance Fe and unavoidable impurities. The piston ring body is made of steel or the base material is nitrided. The combination of such piston rings is as follows: (a) Ion plating film on the outer peripheral sliding surface of the steel material (hereinafter referred to as "film" in this section)
And (b) form a film on at least one of the outer peripheral sliding surface and the upper and lower surfaces of the steel material; (c) form a nitriding layer and a film on the outer peripheral sliding surface of the steel material. (D) A film is formed on the outer peripheral sliding surface of the steel material, and a nitriding layer is formed on at least one of the upper and lower surfaces; (e) A nitriding layer and a film are formed on the entire sliding surface.

Next, the features of the piston ring of the present invention will be described. At least the outer peripheral sliding surface of the piston ring of the present invention has a film containing chromium and nitrogen as main components by ion plating. The film structure is chromium nitride or a mixed structure of chromium metal and chromium nitride. The chromium nitride coating or the mixed texture coating of metal chromium and chromium nitride is not only excellent in wear resistance and seizure resistance, but also because the vapor pressure of metal chromium is higher than that of titanium etc., it is possible to form a coating at high speed by ion plating. , Is excellent in productivity. On the other hand, when nitrogen and chrome solidify on the body, the temperature of the base material rises significantly due to latent heat, which causes thermal fatigue which causes a large decrease in the tension of the piston ring.

Therefore, in the present invention, in order to prevent heat settling of the piston ring that occurs during ion plating of the coating, the body is made of a steel material having the above composition (1) or (2), and the heat resistance of the base material is increased. Raised. By using such a steel material for the piston ring, thermal settling after ion plating can be prevented, and normal tension can be obtained. Further, the high deposition rate and adhesion of the chromium nitride film are not impaired. Next, the piston ring base material (1)
The reasons for limiting each of the components will be described.

C is an element that forms a solid solution in Fe and contributes to the improvement of strength, and forms an carbide, which is an important element that contributes to wear resistance, so at least 0.35% is necessary. However, C, like N, is an interstitial solid solution element in Fe, so addition of a large amount not only leads to a reduction in elongation and drawing required when processing the piston ring material or the piston ring itself, but also improves heat resistance. Therefore, as a result of increasing the amount of carbides formed between Cr and Mo which are the elements to be added, the effect of adding these elements is weakened.
Further, since the coarse carbonitride is formed by the nitriding treatment and the aluminum alloy of the mating material is abraded, the upper limit is set to 0.45%.

Si is an element that forms a solid solution in Fe to improve heat resistance. To obtain this effect, at least 1.8
0% Si is required. However, addition of a large amount not only lowers the cold workability, but also lowers the thermal conductivity, which accelerates the temperature rise of the contact surface due to sliding and impairs the seizure resistance, so the upper limit is 2.50%. And

Mn is added as a deoxidizing agent during the production of ingots, and Mn is added to prevent the solid solution of Si and its oxidation.
Although it is an element that adjusts the preferable conditions for solid solution of i, addition of a large amount reduces hot workability, so the upper limit was made 0.60%.

Cr is a carbide forming element and is important for imparting wear resistance. It is also an element that forms a solid solution in Fe and improves heat resistance and oxidation resistance. In order to obtain these effects sufficiently, it is necessary to add at least 10.0% or more. However, addition of a large amount forms a large amount of carbide, reduces toughness, and further forms a large amount of solid solution with Fe to reduce workability, so 12.0% was made the upper limit.

Ni is an element that forms a solid solution with Fe to increase ductility and improve workability. However, in the case of this material, the effect is not remarkable because other alloying elements are added in large amounts, and it is an effective element. Therefore, it leads to cost increase, 0.60%
Was set as the upper limit.

Mo is added for the purpose of imparting heat resistance and seizure resistance, but if it is 0.70% or less, the effect is insufficient, and if it exceeds 1.30%, the hot workability is rather deteriorated. Since the toughness is also impaired, the range is 0.70 to 1.30%.

The functions of C, Si, Mn, Cr and Ni contained in the piston ring base material (2) of the present invention are basically the same as those described in the base material (1), but Corrections have been made in points. C in the base material (2)
Since the content is 0.45% or more and the content of Cr is 9.50% or less, (1) has a relatively large amount of special carbides such as Cr ₇ C ₃ , and (2) has Fe ₃ with solid solution of Cr _3. C and the like are relatively large. As a result, the base material (2) has the same heat sink resistance as the base material (1). Also,
If C exceeds 0.55% and Cr exceeds 9.5%, the above-mentioned adverse effects appear. Since Si tends to increase the amount of C solid solution in the matrix by expanding the α-Fe region, adding a large amount reduces the amount of carbide formation. Since the base material (2) has a small amount of Cr and thus tends to have a small amount of Cr-containing carbide, the Si content is smaller than that of the base material (1) in order to offset this, and the range is 1.00 to 2.00%. By doing so, excessive expansion of the α-Fe region is suppressed. The addition of Mo, which is the purpose of adding heat resistance and seizure resistance, is not remarkable in the composition of the base material (2), so the base material (2) is not particularly limited. That is, Mo is allowed to be contained in a small amount as an impurity.

The steel material having the above-mentioned composition is processed into a bar steel which is a rough shape material of a piston ring by hot and cold working,
After that, it is bent and then cut and polished. When performing various known nitriding treatments, nitriding is performed after bending. The action of the above components of the steel material of the present invention is exerted even in the processed state. Further, although various heat treatments such as annealing, quenching and tempering can be performed on the steel material, it is preferable to heat the steel material in the rough-shaped material state to a temperature above the temperature exposed during ion plating, for example, 400 to 500 ° C. The ion plating film can be formed under the conditions described in the above publication, and the thickness thereof is preferably 20-40.
μm.

[0018]

[Function] The rate of change in hardness of various steel materials caused by the formation of the ion plating film is defined by the following formula: {(hardness before heating-hardness after heating) / hardness after heating} x
The results of evaluation by 100 (%) are shown in Table 1 to explain the action of the present invention.

[0019]

[Table 1]

Since carbon steel does not contribute to the heat resistance of alloying elements such as Cr, the rate of change in hardness is high. next,
Since spring steel has a lower carbon content than carbon steel, the hardness before heating is low, but the rate of change in hardness is small due to the effects of Si, Cr, Mn and the like. However, the contribution of these alloying elements is still small. Subsequently, in SUS440B, the effect of Cr is recognized, but a considerable change in hardness occurs with the decomposition of martensite by heating. Furthermore SUS42
0J2 has little change in hardness due to such a microstructure change, but also has a considerable change in hardness due to relatively low Cr / low C. On the other hand, the steel of the present invention in which the composition of Cr-based stainless steel is relatively low Cr and the amount of Si is increased has the smallest hardness change. It is considered that this is because the Cr amount range in which the amounts of martensite and carbide are optimally balanced is on the relatively low Cr side, and the effect of strengthening the Fe solid solution by Si is high in such a low Cr range. .

[0021]

EXAMPLES Example 1 Next, Table 2 shows the composition of the piston ring body and the hardness of the core portion used as Examples and Comparative Examples of the present invention.

[0022]

[Table 2]

The balance of the ingredients listed in Table 2 is P,
A small amount of usual impurities such as S and Fe. Sample material N in the table
o. No. 1 of the present invention (base metal (1)), No. 1 No. 2 of the present invention steel (base material (2)), No. Nos. 3 to 6 are steels currently used as piston rings. 3 is carbon steel (SWRS
82A), No. 4 is Si-Cr steel (SWOSC-
V), No. 5 is 17Cr steel (SUS44OB), N
o. 6 is 13Cr steel (SUS420J2).

Example 2 Using the steel material (1) of the present invention and the current steel materials 3 to 6, a piston ring main body for ion plating having a size of φ86 × 1.2 × 3.1 mm was formed by ordinary forming and processing. did.
The steels of the present invention and the current steels 3 and 4 were further gas-nitrided to have a thickness of 100 μm on the entire circumference of the piston ring.
After the nitriding layer was formed by gas nitriding, the peripheral nitrogen compound layer was removed to expose the nitrogen diffusion layer. Then, each of these 10 piston rings is stacked with their outer peripheral surfaces aligned, and after performing normal pretreatment, ion plating is performed with an arc type ion plating device to form a chromium nitride film on the outer peripheral surface of the piston ring. Formed. The upper and lower exposed (sliding) surfaces of the piston ring subjected to the nitriding treatment were used as the nitriding treatment layer. Then, each piston ring was cut, and the ion plating film thickness, hardness and base metal hardness were measured from the cross section. Regarding the coating structure, the outer peripheral surface of the ring was identified by X-ray diffraction.

The ion plating conditions and results are as follows. Ion plating conditions 1. Arc power-200A 2. Bias voltage −10V 3. Preheating temperature −500 ° C. 4. Nitrogen gas pressure-10 mTorr 5. Time-3 hours

[0026]

[Table 3]

From Table 3 above, it can be seen that the piston ring of the present invention has less hardness decrease due to temperature increase during ion plating than the current steels 1 and 2, and has less thermal fatigue.

Next, the invention steel (No. 1) and the current steel 3
Abrasion test by a finishing engine was carried out on the piston rings of (No. 4) and the steel 4 (No. 5) currently in use until final processing. Working steel 1 (No. 2) and working steel 2 (No.
The one using 3) could not be used for the test because the subsequent processing could not be performed due to the heat set. Next, the conditions and results of the engine test are as follows.

Engine test conditions Engine used Water-cooled 6-cylinder 2,500 cc engine (piston ring 1st φ86 × 1.2 × 3.1) 6,000 rpm × 4/4 × 100 hours

[0030]

[Table 4]

1) Ring of the present invention 1: Ion plating film (CrN) directly provided on the base material (1) 2) Ring of the present invention 2: Ion plating film (CrN) after gas nitriding on the base material (1) 3) Comparative ring 1: 17Cr Ion plating film (Cr) directly on the base material of 17Cr martensitic stainless steel.
N) provided 4) Comparative ring 2: 13Cr Ion plating film (Cr) directly on the base material of martensitic stainless steel.
N) is provided 5) Comparison ring 3: 17Cr Cr is obtained by forming a nitriding layer on the base material of martensitic stainless steel and then providing an ion plating film (CrN) only on the outer peripheral surface 6) Comparison ring 4: 13Cr martensitic stainless steel base material provided with a nitriding layer, and then an ion plating film (CrN) provided only on the outer peripheral surface

The following can be said from the test results in the engine. In the piston ring of the present invention, not only is the wear of the outer peripheral surface of the piston ring reduced due to the effect of the ion plating film, but the hardness of the upper and lower surfaces slightly decreases due to the temperature rise during ion plating, but the wear of the upper and lower surfaces is also low. The piston rings made of 17Cr martensitic stainless steel as a base material (Comparative Examples 1 and 3) have heat resistance that does not cause thermal settling due to a temperature rise during ion plating, but since the hardness is low from the beginning, If the material is left as it is, the upper and lower surfaces of the piston ring itself will wear out much. The piston rings using 13Cr martensitic stainless steel as the base material (Comparative Examples 2 and 4) have the same tendency as the piston rings using 17Cr martensitic stainless steel as the base material.

Example 3 Steel Nos. Of the present invention shown in Table 2 were used. 2 and gas nitriding the same were subjected to ion plating under the same conditions as in Example 2, and the coating structure was CrN, the film thickness was 28 μm, and the altitude was Hmv.
An ion plating film of 1,752 was formed. When an engine test was conducted on these piston rings under the same conditions as in Example 2, as shown in Table 5, Example 2
The almost same result was obtained.

[0034]

[Table 5]

[0035]

EFFECTS OF THE INVENTION The piston ring of the present invention does not cause thermal settling even at a temperature rise during ion plating, does not lose tension, and has a small decrease in base metal hardness, so that the upper and lower surfaces of the piston ring are less worn. . Further, even if the nitriding treatment is carried out, a large crystal carbonitride is not formed, so that the aluminum alloy piston ring groove of the mating material is not worn.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-180608 (JP, A) JP-A-8-226541 (JP, A) JP-A-5-25591 (JP, A) JP-2552509 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16J 9/26 F02F 5/00

Claims (5)

(57) [Claims] 1. A piston ring for an internal combustion engine having an ion plating film composed of a chromium nitride structure containing Cr and N as main components, wherein the body of the piston ring is C: 0.35 to 0.45 in weight%.
%, Si: 1.80 to 2.50%, Mn: 0.60% or less, Cr: 10.0 to 12.0
%, Ni: 0.6% or less, Mo: 0.70 to 1.30%, and the balance Fe and unavoidable impurities, characterized by being a piston ring for an internal combustion engine. 2. A piston ring for an internal combustion engine, comprising Cr and N as main components, and an ion plating film made of a metal chromium and a chromium nitride structure, wherein the body of the piston ring is C: 0.35 to 0.45 in weight%.
%, Si: 1.80 to 2.50%, Mn: 0.60% or less, Cr: 10.0 to 12.0
%, Ni: 0.6% or less, Mo: 0.70 to 1.30%, and the balance Fe and unavoidable impurities, characterized by being a piston ring for an internal combustion engine. 3. A piston ring for an internal combustion engine having an ion plating film composed of a chromium nitride structure containing Cr and N as main components, wherein the body of the piston ring is C: 0.45 to 0.55 in weight%.
%, Si: 1.00 to 2.00%, Mn: 0.60% or less, Cr: 7.50 to 9.50
%, Ni: 0.6% or less, and the balance being Fe and inevitable impurities, which is a piston ring for an internal combustion engine. 4. A piston ring for an internal combustion engine, comprising Cr and N as main components, and an ion plating film composed of metallic chromium and a chromium nitride structure, wherein the body of the piston ring is C: 0.45 to 0.55 by weight%.
%, Si: 1.00 to 2.00%, Mn: 0.60% or less, Cr: 7.50 to 9.50
%, Ni: 0.6% or less, and the balance being Fe and inevitable impurities, which is a piston ring for an internal combustion engine. 5. The piston ring for an internal combustion engine according to claim 1, wherein the piston ring body is nitrided.