JP2952006B2 - Piston ring material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piston ring used for an internal combustion engine, and particularly to a material used as a second ring mounted on an automobile engine.

[Conventional technology]

BACKGROUND ART A piston ring used for an internal combustion engine, particularly an automobile engine, has been shifting from a conventional cast iron to a so-called steel piston ring which is used by processing a steel flat wire into a ring shape. This is due to the need to reduce the weight of the ring and increase the mechanical strength in order to respond to demands for higher engine speeds and higher power, and the effect of a drastic reduction in the ring manufacturing process is also a major factor. I have.

The application of steel piston rings has preceded top rings and oil rings in high load environments,
The material used is Si-Cr steel, 17Cr martensitic steel, or martensitic stainless steel as shown in JP-B-58-46542 and JP-B-61-19703, which has been subjected to surface treatment such as nitriding. Have been. Furthermore, JP-A-61-
60861 and JP-A-61-199053 also propose a piston ring material containing Cr.

However, for the second ring with a relatively small load, cast iron such as FC25 is still applied.

However, recently, excellent fatigue strength has also been required for the second ring, and the above-mentioned FC25 class cast iron has insufficient fatigue strength. At present, new steel is being sought.

[Problems to be solved by the invention]

As described above, steel is being used for the top ring and the oil ring, but the demand for steel for the second ring is also increasing in order to further improve the performance of the engine. The second ring is required to have wear resistance and seizure resistance as a sliding member.

The second ring is used under relatively mild conditions for gasoline engines, and is used under relatively severe conditions for diesel engines. There must be. For the second ring used under relatively mild conditions, a low-cost material that can be used without reducing the amount of alloying elements as much as possible and without performing surface treatment such as nitriding is desired.

Therefore, for this application, M ₃
Steel enriched in C-type carbides is considered promising.

However, for the second ring used under relatively severe conditions, in addition to the improvement of wear resistance and seizure resistance, excellent fatigue strength is required, so the above idea of only low-cost materials is sufficient. is not.

The present invention seeks to provide a material that is particularly suitable for the second ring among the piston rings that can be used under any of these conditions.

[Means for solving the problem]

The present inventors have made extensive studies in order to solve the above problems, whereas the conventional piston ring material were M ₃ C type carbide mainly added to M ₃ C type carbide, M ₇ C ₃
By enriching the type carbides, good wear resistance and seizure can be obtained, and non-metallic inclusions are reduced by regulating the S and O levels of impurities to low levels. It has been found that the fatigue strength is improved without performing such a surface treatment, and the present invention has been achieved.

That is, the first invention of the present invention is a method in which C
%, Si 1.5% or less, Mn 1.5% or less, Cr 3.0-9.0%, the balance being Fe and unavoidable impurities.
S is a piston ring material characterized by being restricted to 0.003% or less and O to 25ppm or less. And the second invention is the weight%
With C 0.7-1.3%, Si 1.5% or less, Mn 1.5% or less, Cr 3.0
~ 9.0%, one or two of Mo and W are not more than 2.5% by Mo + 1 / 2W, the balance being Fe and unavoidable impurities.
S is a piston ring material characterized by being restricted to 0.003% or less and O to 25ppm or less. In the third invention, C 0.
7-1.3%, Si 1.5% or less, Mn 1.5% or less, Cr 3.0-9.0
%, One or two of Mo and W at 2.5% or less at Mo + 1 / 2W, V
1.0% or less, Nb 0.5% or less containing one or two kinds, the balance consisting of Fe and unavoidable impurities.
A piston ring material characterized by being restricted to 3% or less and O to 25ppm or less. Further, the fourth invention is characterized in that the first invention comprises Ni
In the fifth invention, the second invention is Ni, and in the sixth invention, the third invention is Ni.
A piston ring material characterized by adding Ni in an amount of 2.0% or less.

[Action]

 The reasons for limiting the components in the present invention are described below.

C is an element that forms a solid solution in iron and imparts strength, and is an important element that forms carbides and contributes to wear resistance. At least 0.7% is required to achieve this effect. However, if it exceeds 1.3%, the workability of the flat wire and the ring becomes difficult, so the upper limit is made 1.3%.

Si is usually added as a deoxidizing agent, but if it exceeds 1.5%, it not only impairs cold workability but also lowers the thermal conductivity, thereby increasing the temperature of the contact surface due to sliding and preventing seizure. 1.5% was set as the upper limit to impair the properties.

Mn is added as a deoxidizer like Si, but if it is 1.5% or more, it impairs hot workability. In particular, the flat wire for the piston ring material of the present invention requires a high processing rate.
The upper limit was 1.5%.

Cr forms one of the features of the present invention, which forms M ₇ C ₃ type carbides, and contributes to the improvement of wear resistance, and also forms a solid solution in the matrix to increase softening resistance, thereby reducing thermal settling due to temperature rise during engine operation. Effective for It is also necessary to ensure hardenability and obtain sufficient heat treatment hardness.

In the present invention, for forming the M ₇ C ₃ -type carbide,
Cr content must be at least 3.0%.

However, if added excessively, the amount of carbides becomes too large, deteriorating cold workability, and lowering the thermal conductivity impairs seizure resistance. Therefore, the upper limit was made 9.0%.

Both Mo and W have the same function as carbide-forming elements, and the addition of one or two of these elements further improves the wear resistance. However, excessive addition increases the amount of carbide and deteriorates workability and toughness. Since the atomic weight of W is twice that of Mo, the upper limit of the amount of (Mo + 1 / 2W) is 2.
5%.

V and Nb are MC type hard carbide forming elements and are equivalent in that they are effective in improving wear resistance. However, excessive addition deteriorates workability and toughness, and hard carbides easily wear the partner (cylinder). Therefore, the upper limit of V is set to 1.0%, and the upper limit of Nb is set to 0.5%.

Ni dissolves in the matrix and has the effect of imparting toughness.
However, excessive addition prevents the lowering of the annealing hardness, so the upper limit was made 2.0%.

S and O are usually contained in trace amounts as impurity elements. S and O are mainly present as non-metallic inclusions in steel and have an adverse effect. In particular, in order to obtain the effect of improving the fatigue strength required for the piston ring material, it was found that S and O had to be suppressed to a considerably low level.
Regulated below.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

Table 1 shows the chemical components of the test materials. The material of the present invention and the comparative material are subjected to predetermined quenching and tempering after melting, forging and drawing (10
Hardness is HRC40-5 by quenching at 25 ℃ and tempering at 600-700 ℃
Adjusted to 0. The materials 1 and 3 of the present invention have a hardness level of 2
The test was carried out with the following changes. The conventional material FC25 is cast iron.

The abrasion test was performed using a reciprocating friction tester with FC25 cast iron as a mating material assuming a cylinder, and the amount of abrasion was measured.

Seizure resistance was evaluated using a Fabry abrasion tester.
In this test, a test material rotating at 300 rpm is sandwiched between V-blocks as mating members, seizure is detected by torque fluctuations of test pins while gradually applying a load, and the seizure load at this time is detected.

In the test, FC25 was used as a mating material, and the test was performed while lubricating oil was dropped. Seizure resistance is FC piston's conventional material FC
The value of 25 was shown as an index with 100 as the value.

Fatigue strength was determined 10 ⁷ times fatigue limit by rotating bending fatigue test.

Table 2 shows the hardness, the wear amount ratio, the seizure load ratio, and the fatigue limit stress.

The material of the present invention has significantly improved wear resistance as compared with the conventional material FC25. This is because the material of the present invention mainly contains an appropriate amount of M ₇ C ₃ type carbide and has an appropriate hardness. The wear resistance of the comparative materials 11 and 12 is better than the conventional material FC25, but is inferior to the material of the present invention. This is for comparative material 11,
M ₃ C carbides are the main component, and M ₇ C ₃ type carbides are not included.
Further, in the case of the comparative material 12, since the amount of C is small, the amount of carbide is insufficient.

Next, regarding the seizure resistance, the material of the present invention shows a value substantially equal to or higher than that of the conventional material FC25, and has practically sufficient seizure resistance.

Further, the fatigue strength of the material of the present invention is significantly higher than that of the conventional material FC25. This is due to the fact that the alloy amount of the material of the present invention is appropriate and the impurity amount (S, O) is regulated to be low. The comparative materials 13 and 14 have the same components as the material of the present invention except for S and O, but are inferior in fatigue strength to the material of the present invention because of the high amounts of S and O.

As a result, the material of the present invention has seizure resistance equal to or higher than that of the conventional material FC25, and has abrasion resistance and fatigue strength that far exceed FC25.

Although the above results were obtained without nitriding the surface, nitriding the surface further improves abrasion resistance and seizure resistance, so it can be applied to more severe conditions. is there.

As a result, it is clear that the material of the present invention has seizure resistance equal to or higher than that of the conventional material FC25 and wear resistance exceeding FC25.

〔The invention's effect〕

As described above, the material of the present invention contains an appropriate amount of M ₇ C ₃ type carbide and regulates the amount of impurities of O and S to an amount effective for improving the fatigue strength of the piston ring material, thereby improving the conventional material. FC
It has seizure resistance equal to or higher than 25 and wear resistance and fatigue strength that is significantly higher than FC25, and because of its extremely high strength, it is used for piston rings such as second rings to reduce weight and performance. It greatly contributes to the improvement of

Continuation of the front page (56) References JP-A-3-122257 (JP, A) JP-A-63-223147 (JP, A) JP-A-61-60861 (JP, A) JP-A-57-210954 (JP) , A) JP-B 64-11100 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 301 C22C 38/00 302 C22C 38/18 F02F 5/00

Claims (6)

(57) [Claims] C. 0.7 to 1.3% by weight, 1.5% or less of Si, Mn
1.5% or less, Cr 3.0-9.0%, the balance consists of Fe and unavoidable impurities. Of the impurities, S 0.003% or less, O 25p
A piston ring material characterized by being regulated to pm or less. 2. The composition according to claim 2, wherein C is 0.7 to 1.3% by weight, Si is 1.5% or less, and Mn is
1.5% or less, Cr 3.0 to 9.0%, one or two kinds of Mo and W are 2.5% or less by Mo + 1 / 2W, the balance consists of Fe and unavoidable impurities. A piston ring material characterized in that: (3) C-0.7-1.3% by weight, Si-1.5% or less, Mn
1.5% or less, Cr 3.0 to 9.0%, one or two of Mo and W in Mo + 1 / 2W 2.5% or less, V 1.0% or less, Nb 0.5% or less, including Fe or inevitable balance A piston ring material comprising impurities, the content of which is controlled to 0.003% or less of S and 25 ppm or less of O. C. 0.7 to 1.3% by weight of C, 1.5% or less of Si, Mn
It contains 1.5% or less, Cr 3.0 to 9.0%, and Ni 2.0% or less, with the balance being Fe and unavoidable impurities.
Piston ring material characterized in that S is regulated to 0.003% or less and O to 25ppm or less. 5. The method according to claim 1, wherein C is 0.7 to 1.3% by weight, Si is 1.5% or less,
Including 1.5% or less, Cr 3.0-9.0%, one or two kinds of Mo and W in Mo + 1 / 2W 2.5% or less, and Ni 2.0% or less,
The balance consists of Fe and unavoidable impurities.
A piston ring material characterized by being restricted to 003% or less and O 25ppm or less. 6. C-0.7-1.3% by weight, Si-1.5% or less, Mn
1.5% or less, Cr 3.0 to 9.0%, one or two types of Mo and W at 2.5% or less with Mo + 1 / 2W, V 1.0% or less, Nb 0.5% or less one or two types, and Ni 2.0% or less A piston ring material comprising: a balance of Fe and inevitable impurities, wherein the content of impurities is controlled to 0.003% or less and O to 25 ppm or less.