JPH05186854A - Piston ring material - Google Patents

Abstract

PURPOSE:To provide a piston ring material having such seizing, wear and corrosion resistance as to ensure high performance for a piston ring or to make even alcoholic fuel usable for the piston ring. CONSTITUTION:This piston ring material has a basic compsn. consisting of, by weight, >0.3-1.3% C, <=1.5% Si, <=1.5% Mn, 5.0-20.0% Cr, 0.5-5.0% Cu and the balance Fe with inevitable impurities or further, if necessary contains Mo and/or W satisfying Mo+1/2W<=2.5%, V and/or Nb satisfying V+1/2Nb=0.05 to 1.5% and >=0.5%, in total, of <=2.5% Ni and/or <=12% Co.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring material used in an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, cast iron has been used as a material for piston rings, but the application of steel piston rings has expanded with the recent demands for higher engine efficiency, higher load, and lighter weight. There is. Since this piston ring made of steel allows the piston to be made thinner, it meets the demand for weight reduction and is manufactured by ring processing of the flat wire, so the manufacturing process is significantly simplified compared to cast iron rings. There is an advantage that can be realized. From such a background, steel piston ring materials are disclosed in, for example, Japanese Patent Publication No. 61-22131, Japanese Patent Publication No. 57-8302, Japanese Patent Publication No. 58-46542, Japanese Patent Publication No. 61-21302, and Japanese Patent Application Laid-Open No. 1-208435. Many materials have been proposed.

At present, among the steel piston rings for automobile engines, particularly those requiring severe working conditions, Si-Cr steel (JIS SWOSC-V), SKD61, 13 are used.
Cr, 17Cr system martensitic stainless steel and the like are used. These materials are used with a hardness of about HRC38 to 45 due to the requirement of ring workability, and the outer peripheral part of the ring that slides with the cylinder is hard Cr plated or hardened to improve wear resistance and seizure resistance. , Composite plating containing hard particles,
Alternatively, a nitriding process is mainly performed on a high Cr-based material. At present, 17Cr stainless steel (SUS440B class) + nitriding material is positioned as the highest performance piston ring.

[0004]

By the way, in addition to the high performance of engines in recent years, in addition to the use of low-grade fuel, introduction of combustion gas into the engine for exhaust gas regulations, alcohol fuel,
The use of new fuels such as natural gas-based fuels has been studied and some test runs have been conducted. In these internal combustion engines, oil deterioration is accelerated due to factors such as oil depletion due to speed increase, increase in moisture generated after combustion, increase in corrosiveness due to sulfur oxides, increase in corrosiveness due to carboxylic acid, and piston ring and cylinder Since the lubricity deteriorates, there is a demand for a piston ring material that is more excellent in seizure resistance and corrosion resistance than the conventionally proposed materials. In addition, the above phenomenon is
This is called the scuff phenomenon of the piston ring and cylinder, and is the biggest problem of the piston ring material. The purpose of the present invention is to
It is an object of the present invention to provide a ring material which is improved in seizure resistance and corrosion resistance at the same time as stainless steel piston ring materials in comparison with conventional materials.

[0005]

Means for Solving the Problems As a result of studying the effects of various elements that simultaneously enhance seizure resistance and corrosion resistance on stainless steel for piston ring, the mating cast iron type 4 is used as the mating material of the piston ring. The present inventors have found that Cu in steel containing Cr, Cr carbide or carbides such as Mo, W, V and Nb is more effective in improving seizure resistance and corrosion resistance, and completed the present invention.

That is, the first aspect of the present invention is, in wt%, more than C 0.3% and 1.3% or less, Si 1.5% or less, and Mn 1.5%.
The following is a piston ring material characterized by comprising Cr 5.0 to 20.0%, Cu 0.5 to 5.0%, the balance Fe and unavoidable impurities. The second invention is C% 0.3% by weight and 1.3% by weight.
Below, Si 1.5% or less, Mn 1.5% or less, Cr 5.0-20.0%,
One or two of Mo and W is Mo + 1 / 2W and 2.5% or less, Cu
A third aspect of the present invention is a piston ring material characterized by comprising 0.5 to 5.0%, the balance Fe and unavoidable impurities.
% By weight, more than C 0.3% and 1.3% or less, Si 1.5% or less, Mn
1.5% or less, Cr 5.0 to 20.0%, one or two kinds of Mo and W are 2.5% or less at Mo + 1 / 2W, one or two kinds of V and Nb are 0.05 to 1.5% at V + 1 / 2Nb, and Cu 0.5 to The piston ring is characterized by comprising 5.0%, the balance Fe and unavoidable impurities. In the fourth invention, a part of Fe is 2.5% or less of Ni and 1% or 2% of Co of 12% or less (provided that Ni + Co is
0.5% or more) is the piston ring material according to any one of the first to third inventions.

[0007]

The reasons for limiting the components of the present invention will be described below. C combines with elements such as Cr, Mo, W, V and Nb to form a carbide, which contributes to the improvement of wear resistance and seizure resistance, and part of which forms a solid solution in the matrix to form a matrix. Strengthen. In the case of steel piston ring material, these effects must be added in excess of 0.3%, but if it exceeds 1.3%, excessive carbides are formed, so the workability of the ring material and the formability of the ring itself are increased. Aggravate. Therefore, it exceeds 0.3% 1.
Limited to 3% or less.

Si is an element that is added for the purpose of deoxidizing during refining of steel and is effective for improving corrosion resistance, hardenability and strength. However, if a large amount is contained, cold workability is impaired, so the content is limited to 1.5% or less. Mn is added for the purpose of desulfurization during refining of steel, but if it exceeds 1.5, it impairs hot workability, so it is limited to 1.5% or less.

As described above, Cr is combined with C to form a carbide.
(M ₂₃ C ₆ type and M ₇ C ₃ type) to improve wear resistance and seizure resistance. Further, a part of them dissolves in the matrix to improve corrosion resistance, oxidation resistance and heat resistance. In addition, in a particularly effective nitriding treatment as one of the surface treatments of the piston ring, a hard nitriding layer is formed, wear resistance,
Greatly improves seizure resistance. In order to exert these effects, 5.0% is necessary, but if it exceeds 20.0%, the toughness decreases, so the range of Cr is limited to 5.0 to 20.0%.

Mo and W combine with C to form carbides of their own, and they also form a solid solution in Cr carbides to strengthen them, further enhance the softening resistance in tempering, and perform nitriding treatment. When it is carried out, it contributes to the formation of a nitrided layer and improves wear resistance and seizure resistance. Further, Mo has the effect of improving sulfuric acid corrosion resistance. However, if added in excess of 2.5%, the amount of hard carbides increases, causing fatigue strength to decrease, and it is an expensive element. Therefore, when it is contained, Mo + 1 / 2W is limited to 2.5% or less. ..

Both V and Nb have the effect of refining the crystal grains, and not only contribute to the improvement of the toughness of the piston ring, but they also form carbides themselves as in Mo and W, and in Cr carbides. It also forms a solid solution and strengthens this to improve wear resistance and seizure resistance. Also,
Both elements improve sulfuric acid corrosion resistance and carboxylic acid corrosion resistance. In order to obtain these effects, at least 0.05% or more of V + 1 / 2Nb must be used for one or two of V and Nb. However, if added excessively, MC type carbides are excessively formed and the toughness is deteriorated, so the upper limit of the amount of V + 1 / 2Nb was set to 1.5%.

[0012] Ni and Co do not form carbides with both elements, and they form a solid solution in the matrix, and have the effect of enhancing the sulfuric acid corrosion resistance. Especially in the case of a piston ring for nitriding,
Since Ni and Co themselves do not form a nitride, the action remains in the nitride layer. To obtain this effect, at least 0.5% of Ni + Co is required for one or two of Ni and Co. However, if Ni exceeds 2.5%, it becomes difficult to obtain a predetermined hardness during heat treatment,
If Co exceeds 12%, hot workability and cold workability are deteriorated, so Ni is limited to 2.5% or less and Co is limited to 12% or less.

In the present invention, Cu is an important element which not only improves the seizure resistance but also enhances the corrosion resistance to carboxylic acid. Cu does not form carbides or nitrides, and the Fe solid solution of Cu is finely distributed in the matrix, whereby the seizure resistance between the piston ring and the cylinder can be greatly improved. Also, as described above, C
Since u-containing steel has significantly improved corrosion resistance against carboxylic acids, it can be made into a piston ring with more excellent corrosion resistance than conventional materials against corrosive atmospheres such as combustion gas of alcohol fuel. .. In order to obtain the above effect, Cu needs to be 0.5% or more, but if it exceeds 5.0%, the hot workability deteriorates, so the range of Cu is 0.5 to 5.
Limited to 0%.

[0014]

The present invention will be described in detail below with reference to examples. Table 1 shows the chemical composition of the test material. Of these, No.
No. 1 to No. 17 are materials of the present invention, No. 18 to No. 22 are
It is a conventional material. Conventional materials No. 18 and 19 are SKD61 and 13 currently used as top rings for gasoline vehicles.
No.20 is a Cr-based material, and 17Cr-based piston ring is used under the current severe conditions.
1 and 22 are steels disclosed in the above-mentioned Japanese Patent Laid-Open No. 2-208435. The test material was prepared by the steps of melting, forging, and annealing, and then quenched and tempered to adjust the hardness to HRC40 to 43. Then, gas nitriding treatment was performed at 540 ° C. for 20 hours. Since a brittle nitride is formed on the outermost surface of the nitride diffusion layer by the gas nitriding treatment, this was removed by polishing to obtain a test material.

[0015]

[Table 1]

[0016]

[Table 2]

Table 2 shows the results of seizure test and abrasion test of each test material and 10% sulfuric acid and carboxylic acid (5% acetic acid + 5%
Indicates the weight loss due to formic acid). For these tests, an ultra-high pressure abrasion tester was used. The outline of the test piece part is shown in FIGS. The seizure test was performed using the same tester under the following conditions. Friction speed ・ ・ ・ 8m / s Friction surface pressure ・ ・ ・ Initial pressure 20kg / cm ² , rising by 10kg / cm ² every 3 minutes Lubricating oil ・ ・ ・ Motor oil # 30, temperature 80 ℃, from the center of the stator holder 400 ml / min lubrication seizure detection: Detected by load cell and dynamic strain gauge (detects abnormal friction force during seizure) Counterpart material: JIS gray cast iron class 4 (FC25)

The wear test was carried out under the following conditions to measure the wear amount of the test piece. Friction speed ・ ・ ・ 3m / s Friction surface pressure ・ ・ ・ 80kg / cm ² Lubricating oil ・ ・ ・ Motor oil # 30, temperature 80 ℃, 400ml / min lubrication from the center of the stator holder Friction distance ・ ・ ・ 50km Counterpart material ・··· JIS JIS cast iron type 4 (FC25) For corrosion resistance, 10 mmφ × 20 mmL gas-nitrided sample (outermost surface removal), 10% sulfuric acid at 40 ° C, 40% corrosion loss and 5% acetic acid 5% formic acid + Water (60 ° C) and corrosion weight loss after 40 hours were obtained.

Among the test materials, C and Cr of the invention materials No. 1 and 6
% Is steel of the same level as the conventional material No. 18, the seizure-occurring surface pressure is 14 to 28% higher than No. 18, and the wear resistance and corrosion resistance are excellent. No. 2, which is the material of the present invention,
7,8,9,10 are 13Cr type steels, and the conventional materials are No. 1
9 is steel equivalent to 13Cr series. Even in this case, the seizure-occurring surface pressure is 25% higher than that of the conventional material. In addition, the wear resistance and the corrosion resistance are similarly increased. No. 3, which is the material of the present invention,
11 and 16 are 17Cr steels, which correspond to No. 20 as the conventional material. Even in this case, the seizure-occurring surface pressure of the material of the present invention is 20% or more, and the wear resistance and corrosion resistance are excellent. Nos. 4, 14, and 17 of the material of the present invention are 15Cr type steels, and some contain Co. The conventional material for this is No. 21. The invention materials No. 4, 14 and 17 show a seizure occurrence surface pressure increase of 10% or more as compared with the conventional material No. 21. Further, improvement in wear resistance and corrosion resistance is also seen. Inventive materials No. 5, 12, and 13 are C in 17Cr material.
It contains o and corresponds to No. 22 as a conventional material. In addition, the steel No. 15 of the present invention has the best surface pressure for seizure and wear resistance. FIG. 3 shows seizure-occurring surface pressures and wear amounts by distinguishing test materials for each steel type.

[0020]

As compared with the conventional material of the same level, the material of the present invention has a higher seizure-occurring surface pressure and can significantly reduce the scuff generated when it is used for a piston ring. Also, the wear resistance is much better than that of the conventional material. Further, it has a good corrosion resistance to sulfuric acid and carboxylic acid, is extremely excellent especially to carboxylic acid, and can sufficiently cope with alcohol fuel.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ultrahigh pressure wear test device.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a diagram in which the seizure surface pressure and the wear amount of the test material are classified by class.

[Explanation of symbols]

 1 Test piece (5.0mm square x 10L) 2 Disc (Mating material ... FC25) 3 Stator holder 4 Rotor 5 Test piece holder 6 Lubricating oil inlet 7 Load cell 8 Dynamic strain gauge P Friction pressure

Claims (4)

[Claims] 1. A weight percentage of C is more than 0.3% and 1.3% or less, Si
1.5% or less, Mn 1.5% or less, Cr 5.0 to 20.0%, Cu 0.5 to
Piston ring material characterized by being 5.0%, the balance being Fe and inevitable impurities. 2. The content of C exceeds 0.3% by weight and 1.3% or less by weight, Si
1.5% or less, Mn 1.5% or less, Cr 5.0 to 20.0%, one or two kinds of Mo and W are 2.5% or less at Mo + 1 / 2W, Cu 0.5 to 5.0
%, The balance Fe and unavoidable impurities, which is a piston ring material. 3. The weight percentage of C exceeds 0.3% and 1.3% or less, and Si
1.5% or less, Mn 1.5% or less, Cr 5.0 to 20.0%, one or two kinds of Mo and W are 2.5% or less at Mo + 1 / 2W, and 1 of V and Nb.
Type or 2 types with V + 1/2 Nb 0.05-1.5%, Cu 0.5-5.0
%, The balance Fe and unavoidable impurities, which is a piston ring material. 4. The piston according to claim 1, wherein a part of Fe is replaced by one or two kinds of Ni of 2.5% or less and Co of 12% or less (however, Ni + Co is 0.5% or more). Ring material.