JPH0421743A - Piston ring material - Google Patents

Abstract

PURPOSE:To manufacture a second excellent in wear resistance and seizing resistance at low cost by manufacturing a second ring fitted to automobile engine by a high carbon-low alloy steel having a specified compsn. CONSTITUTION:A high carbon-low alloy steel contg., by weight, >1.1 to 1.4% C, <1.0% Si, <1.5% Mn, 0.5 to 3.0% Cr and one or 2 kinds of Mo and W so as to satisfy Mo+W/2<1.5%, or furthermore contg. either one or 2 kinds of <0.5% V and <0.5% Nb or <2.0% Ni independently or compositely is used as stock to manufacture a second ring for an automobile engine. The second ring having remarkably high wear resistance compared to that of FC25 cast iron and not inferior to the above also in seizing resistance can be manufactured at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a material used for piston rings used in internal combustion engines, particularly as a second ring installed in automobile engines.

[Conventional technology]

Piston rings used in internal combustion engines, particularly automobile engines, are increasingly being replaced from conventional cast iron to so-called steel piston rings, which are made by processing flat steel wire into a ring shape. This is due to the need to reduce the weight of the rings and improve their mechanical strength in order to meet the demands for higher speeds and higher output engines.In addition, the effect of significantly shortening the ring manufacturing process 1 is a major factor behind this. ing.

Steel piston rings are used in top rings and oil rings with high-load circumferential gradients, and their materials are 5i-Cr#1.17C martensitic steel or Japanese Patent Publication No. 58-46542, Kosho 61-
Martensitic stainless steel as seen in No. 19703 is used after being subjected to surface treatment such as nitriding treatment. Furthermore, JP-A-63-216949, JP-A-63-
Piston ring materials have also been proposed in No. 223147 and JP-A-1-279733.

However, cast iron such as FC25 is still used for the second ring, which has a relatively low load.

[Problem to be solved by the invention]

As mentioned above, the top ring and oil ring are increasingly being made of steel, but in order to further improve engine performance, there is also an increasing demand for the second ring to be made of steel. As a sliding member, the second ring is required to have wear resistance and seizure resistance, but the operating environment of the top ring is not as severe, so the top ring does not require any high performance characteristics.

Therefore, it is desirable to use as low-alloy steel as possible to reduce costs. However, since it is desirable to be able to use the steel without surface treatment such as nitriding, the steel inner body is required to have a certain degree of wear resistance and seizure resistance.

The object of the present invention is to provide a second ring material that satisfies these requirements, is low cost, and has sufficient wear resistance and seizure resistance.

[Means to solve the problem]

As a result of various studies in order to develop materials that meet the above requirements, this @ Akisha et al. found that carbides (M
It has been found that good wear resistance and anti-seizure properties can be obtained by enriching C type and forming a highly hard matrix. In addition, the basic composition for that purpose is 0.8-
1.4C-0,5~3,OCr was found to be appropriate.5 When emphasis is placed on wear resistance, Mo, W, V.

By adding Nb or the like, wear resistance can be improved, but in order to reduce costs, it is desirable to limit the addition of these expensive elements to as small a quantity as possible.

JP-A-63-216949, JP-A-63-22314
No. 7 discloses a low-alloy material that can be substituted for 5i-Cr[, but all of these require nitriding treatment and require addition of A1 to form a nitrided layer. However, since the steel of the present invention is not subjected to nitriding treatment,
] is not necessary; rather, it is desirable to keep A1 low in order to avoid a decrease in fatigue strength due to alumina-based inclusions.

That is, the first invention of the present invention has a weight percentage of cl, exceeding 1.4% and 1.4% or less, Si 1.0% or less, and Mn 1.5%.
The following is a piston ring material characterized by consisting of 0.5 to 3.0% Cr, one or two of Mo and W in Mo+1/2W of 1.5% or less, and the balance Fe and unavoidable impurities. , the second invention is more than 1% by weight c], 1% by weight
．． 4% or less, Si 1.0% or less, Mn 1.5% or less,
Cr 0.5-3.0%, one or two of Mo and W in Mo+172W, 1.5% or less, VO, 5% or less, Nb
0.5% or less (7) A piston ring material characterized by comprising one or two types, the balance being Fe and unavoidable impurities. Further, the third invention has C more than 1.1% and 1.4% or less, Si 1.0% or less, and Mn 1.0% by weight. ．． 5% or less, Cr 005-3.0%, one or two of Mo and W
Seed with Mo + 172W at 1.5% or less, and Ni 2.
The fourth invention is a piston ring material characterized by containing 0% or less, with the remainder consisting of Fe and unavoidable impurities, and the fourth invention is a piston ring material characterized by containing more than 1.1% of C1.1% and less than 1.4% in weight percent, Si1
．． 0% or less, Mn 1.5% or less, Cr 0.5-3,
0%, one or two types of Mo and W as Mo+1/2W Te1
．． 1 below 5%y, ~'0.5% or less, Nb0.5% or less
Contains one or two species, and 2.0% or less of Ni, with the remainder @l! This piston ring material is characterized by being made of Fe and unavoidable impurities.

C action] The reasons for limiting the ingredients in the present invention will be described below.

C is an important and essential element that imparts strength and toughness, and is an element that forms carbides and is the main cause of exhibiting wear resistance. In the present invention, in order to ensure sufficient wear resistance and seizure resistance, the volume percentage of undissolved carbide after quenching and tempering is 2.0%.
It has been found that it is necessary to contain more than For this purpose, it is necessary for C to exceed at least 1.1%,
Further, if the content exceeds 1.4%, it becomes difficult to manufacture flat wires or form rings, so the upper limit was set at 1.4%.

Si is usually added as a deoxidizing agent, but if it exceeds 1.0%, it not only impairs cold workability but also reduces thermal conductivity, promoting the temperature increase of the contact surface due to sliding. The upper limit was set at 1.0% because it impairs seizure resistance.

Mn is added as a deoxidizing agent like Si, but 1.5
% or more impairs hot workability. In particular, flat wires such as those used in the present invention require a high processing rate, so the upper limit was set at 1.5%.

In the present invention, Cr becomes M and C type carbides to strengthen the material, and also solid-solves in some bases to increase resistance to softening, which is effective against heat loss due to temperature rise during engine operation. . It is also necessary to ensure hardenability and obtain sufficient heat treatment hardness. For this purpose, at least 0.5% or more is required. However, like Si, excessive addition lowers thermal conductivity and impairs seizure resistance, so the upper limit was set at 3.0%.

Both M o and W are carbide-forming elements, and the addition of these elements further improves the wear resistance. However, excessive addition increases the amount of carbides and deteriorates workability and toughness. Furthermore, since all of these elements are expensive, they should be added in as small a quantity as possible for this purpose, which requires low cost.

The effect of W is M.

Since this is equivalent to adding twice the amount of Mo, the upper limit was set at 1.5% with the amount of (Mo+1/2W).

Like V, Nbt+Mo, and W, it is a carbide-forming element and is effective in improving wear resistance. However, ■.

Nb is also an expensive element, and excessive addition deteriorates workability and toughness, and forms carbides that are harder than M o and W, which tends to wear out the mating element (cylinder). Therefore, the upper limits of both V and Nb were set at 0.5%.

Ni is dissolved in solid solution in the matrix and has the effect of imparting toughness and corrosion resistance. However, excessive addition prevents a decrease in annealing hardness, making molding difficult.

Therefore, the upper limit of Ni was set at 2%.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Table 1 shows the chemical components of the test materials. The inventive materials and comparative materials were melted, forged and stretched, then subjected to prescribed quenching and tempering treatments (80%
Quenched at 0°C, 400~b Hardness was adjusted to HRC40~50. Inventive materials 3 and 4 were tested with two different hardness levels.

The conventional material FC25 is cast iron.

The wear test was carried out using a reciprocating friction tester using Fe12, which is the cylinder material, as a mating material.The amount of wear was measured, and the value of the conventional material FC25 of the second ring was 100.
It is expressed as an index.

Seizure resistance was evaluated using a Fabilly abrasion tester. In this test, a test material rotating at 300 rpm is sandwiched between a mating block (1), and while a load is gradually applied, seizing is detected by the torque fluctuation of the test bottle, and the seizing load at this time is detected.

In the test, Fe12 was used as the mating material, and the test was conducted while dropping lubricating oil. The seizure resistance is also 1 higher than that of the conventional material FC25.
00 and expressed as an index.

Table 2 shows the hardness, wear ratio, and seizure load ratio.

The material of the present invention has significantly improved wear resistance compared to the conventional material FC25. This is Mo, W, V.

This is because it contains appropriate amounts of M and C type carbides reinforced with Nb etc. and has high hardness. The wear resistance of comparative material 11 is better than the conventional material FC25, but inferior to the material of the present invention.

This is mainly because the amount of M and C type carbides is insufficient due to the low amount of C.

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

Table [Effects of the Invention] As a result of the above, the material of the present invention has seizure resistance that is equal to or better than the conventional material FC25, and wear resistance that is significantly higher than that of FC25, and is also much stronger than cast iron material. When used as a steel second ring, it greatly contributes to weight reduction and improved performance.

Claims (1)

[Claims] 1% by weight of C more than 1.1% and less than 1.4%, Si 1.
0% or less, Mn 1.5% or less, Cr 0.5-3.0%,
One or two types of Mo and W at 1.5% with Mo+1/2W
Hereinafter, a piston ring material characterized in that the remainder is Fe and unavoidable impurities. 2% by weight of C over 1.1% and 1.4% or less, Si1.
0% or less, Mn 1.5% or less, Cr 0.5-3.0%,
One or two types of Mo and W at 1.5% with Mo+1/2W
Hereinafter, a piston ring material characterized in that it consists of one or both of V0.5% or less and Nb0.5% or less, the balance being Fe and unavoidable impurities. 3 C exceeds 1.1% and 1.4% or less in weight%, Si1.
0% or less, Mn 1.5% or less, Cr 0.5-3.0%,
One or two types of Mo and W at 1.5% with Mo+1/2W
Hereinafter, a piston ring material characterized in that it further contains 2.0% or less of Ni, and the remainder consists of Fe and unavoidable impurities. 4 C over 1.1% and 1.4% or less, Si 1.4% by weight.
0% or less, Mn 1.5% or less, Cr 0.5-3.0%,
One or two types of Mo and W at 1.5% with Mo+1/2W
A piston ring material characterized in that it contains one or both of V0.5% or less, Nb 0.5% or less, and Ni 2.0% or less, with the balance consisting of Fe and unavoidable impurities.