JP3101726B2 - Alloy steel for piston ring and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy steel used for an engine piston ring and a method for producing the same.

[0002]

2. Description of the Related Art Cast iron has been used for piston rings of conventional automobile engines.
In addition to the fact that it is difficult to manufacture a material that is thin in the axial direction and that it is insufficient in terms of breakage strength, and because it has a large inertia, it tends to cause fluttering phenomena. High-strength steel piston rings that can be made thinner and thinner have become widely used.

[0003] In order to manufacture such a steel piston ring, it is necessary to perform processing such as hot rolling, cold drawing, and flat wire rolling. Development of alloy steels that can be performed is underway.

[0004] It is also important from a practical point of view that a nitriding treatment is performed to secure the wear resistance of the piston ring to form a nitrided layer having sufficient wear resistance. Care must be taken to prevent occurrence.

And, manufactured from such a viewpoint,
Each Cr-based alloy steel containing 21%, 17%, and 13% of high-carbon Cr is disclosed in, for example, JP-A-1-201441.
It is proposed in Japanese Patent Publication No. On the other hand, low Si
A piston ring material having good workability and containing Mn and Mn is disclosed in, for example, JP-A-8-109445.

[0006]

However, the above C
In the case of r-based alloy steel, hot and cold workability is poor. On the other hand, in the case of a piston ring material containing low Si and Mn, a sufficient hardness can be obtained by nitriding treatment carried out in practical use. There was a problem that there was not.

[0007] On the other hand, the development of a nitrided steel material containing 8% of medium carbon Cr having good hot and cold workability has been attempted. There was a problem of causing cracks.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. By adding Al, it is possible to prevent the occurrence of quenching cracks in the cooling process after lumping and rolling, and to improve cold workability and nitriding property. An object of the present invention is to obtain an alloy steel for a piston ring having excellent resistance .

Further, the present invention provides a nitriding treatment,
Excellent wear and corrosion resistance can be easily obtained
An object of the present invention is to obtain a method of manufacturing alloy steel for a piston ring .

In order to achieve the above object, the alloy steel for a piston ring according to the first aspect of the present invention comprises, by weight%, C:
0.4-0.7%, Si: 0.1-1%, Mn: 0.1
１1%, Cr: 5 to 10%, Al: 0.3 to 1%, C
u: 0.2 to 1.2%, with the balance being Fe and impurities.

[0011] Pisutonri according to the invention of claim 2
The manufacturing method of alloy steel for aging is, in terms of% by weight, C: 0.4 to
0.7%, Si: 0.1-1%, Mn: 0.1-1%,
Cr: 5 to 10%, Al: 0.3 to 1%, Cu: 0.2
A chemical composition containing -1.2%, with the balance being Fe and impurities, is subjected to nitriding treatment.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Even when it is intended to impart wear resistance to a Cr alloy steel having good hot workability and cold workability, quenching cracking may occur in the cooling process after hot working. Such quenching cracks because the long incubation period of the A ₁ transformation of the steel, does not proceed sufficiently in the cooling process, generated to inflate causing the martensitic transformation in the vicinity of room temperature.

According to the present invention, the changes in the contents of C and Cr, which are the main chemical components, are kept within a practically acceptable range, the transformation incubation period is shortened, and the A ₁ transformation takes place sufficiently in the cooling step. For this purpose, Al is added in a range of 0.3 to 1%. By the addition of Al, it is possible to sufficiently and reliably prevent cracks and breakage that are concerned in the lumping and wire rod rolling steps.

Further, by adding Al as described above, the hardness of the nitrided layer of the steel material can be increased.
When this is used for a piston ring, it is possible to sufficiently improve the wear resistance of the cylinder, and the effect of two birds per stone can be obtained. Further, by keeping the addition amount of Al at a certain value, this has no practical adverse effect on the hot workability and the cold workability.

Therefore, according to the present invention, the hot workability and the cold workability are excellent, and a sufficient hardness can be obtained by the nitriding treatment performed in practical use, and the occurrence of quenching cracks in the cooling process after the hot working. The following alloy steel which can be prevented was obtained.

That is, this alloy steel is made of C, Si, M
It is composed of n, Cr, Al, Cu and the balance of Fe and impurities, and prevents the occurrence of burning cracks in the cooling process after lumping and rolling. Here, C is required to be 0.4% or more in order to obtain a required quenching height, and it is preferable that C is large in order to prevent sintering and quenching cracking in a cooling process after rolling.

The reason that the effect of preventing cracking by burning can be expected is that the completion temperature of martensite transformation is lowered by increasing C, thereby reducing the generation of martensite. By increasing this C,
In the present invention, the upper limit is 0.7% because the workability in the wire drawing process after rolling is reduced.

Next, Si is a necessary component in steelmaking.
Although 0.1% or more is required, 1% is made the upper limit to avoid a decrease in cold workability. Further, Mn is a necessary component in steelmaking and is required to be 0.1% or more, but the upper limit is 1% in order to avoid a decrease in drawability.

Cr is required to be 5% or more in order to improve the wear resistance and corrosion resistance. However, when it is used for a piston ring, 10% is sufficient for practical use.

[0020] Al is a characteristic element used in the present invention, which promotes the A ₁ transformation in the cooling process of the blooming and rolling process, the result of reducing the amount of austenite, to reach the M _S point, martensitic transformation By reducing the percentage of retained austenite before it occurs and by minimizing the volume expansion due to martensitic transformation that occurs during the subsequent cooling process, it functions to eliminate the occurrence of quenching cracks. Here, the addition amount of Al is required to be at least 0.3% or more, but if it exceeds 1%, the cold workability is impaired, so that the upper limit must be 1%.

Further, Cu can be assembled in a rational working step in order to improve the cold workability, so that at least 0.2% or more of Cu is added. However, if the content exceeds 1.2%, cracks are generated during hot working, and working becomes difficult, so it is necessary to limit the content to 1.2%.

[0022]

First, Table 1 shows that the alloy steels (A, C, D, E) according to the present invention obtained within the ranges of addition of the respective elements and the conventional Al-free steels (B, F, G, H) were obtained. ), Cu-free steel (F)
2 shows the chemical composition of the existing piston ring steel DINX-90.

[0023]

[Table 1]

A comparison between the alloy steels shown in Table 1 and the steels without Al is shown in FIG. 1. The cross-sectional hardness distributions of the billet of the material without Al added and the billet of the Al-added material according to the present invention are shown in FIG. It is on the street. Billet is obtained by gradually cooled is covered with a cover after being rolled by chunking roll according to, the Al additive hardness decreases due to the promotion of the A ₁ transformation, hence the occurrence of cracks was not observed .

Further, FIG. 5 is a microscope tissue billet without the addition of Al, the portion having black color is a part completing the A ₁ transformation. On the other hand, FIG. 2 shows the microstructure of the alloy steel of the present invention to which Al is added, and the black portion occupying most of the area is where the A ₁ transformation is completed.
The slightly remaining white part is the part of martensite. That is, it can be seen that in FIG. 5, the composition structure is susceptible to cracking, while in FIG. 2, the composition structure is susceptible to cracking.

FIG. 3 shows a comparison of the nitriding characteristics between the alloy steel of the present invention containing Al and the steel containing no Al. According to the comparison, the hardness of the nitrided layer was significantly increased by the addition of Al. Is shown. FIG. 4 also shows the reduction in drawing due to wire drawing in comparison with the alloy steel of the present invention and the existing DINX-90 steel. It is remarkably high, and it can be seen that it is excellent in cold workability.

[0027]

As described above, according to the present invention, C: 0.4-0.7%, Si: 0.1-1%, M
n: 0.1 to 1%, Cr: 5 to 10%, Al: 0.3 to
1%, Cu: 0.2-1.2%, the balance being a chemical composition consisting of Fe and impurities, so as to obtain good workability of wire drawing, while adding Al, lumping and rolling. The effect is obtained that it is possible to prevent the occurrence of quenching cracks in the subsequent cold process and to obtain an alloy steel for piston rings having excellent cold workability and nitriding properties.

Further, according to the present invention, C:
0.4-0.7%, Si: 0.1-1%, Mn: 0.1
１1%, Cr: 5 to 10%, Al: 0.3 to 1%, C
u: a chemical composition containing 0.2 to 1.2%, with the balance being Fe and impurities, being subjected to nitriding treatment, so that a piston rod having excellent wear resistance and corrosion resistance can be obtained .
Effect that can be easily obtained ring alloy steel.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a difference in hardness of a billet cross section between an alloy steel to which Al is added and an Al-free steel according to an embodiment of the present invention.

FIG. 2 is a micrograph showing a cross section of an alloy steel billet to which Al of the present invention is added.

FIG. 3 is a characteristic diagram showing a difference in nitriding characteristics between an alloy steel to which Al is added and an Al-free steel according to the present invention.

FIG. 4 is a characteristic diagram showing a difference in reduction characteristics of drawing by the drawing between the alloy steel to which Al is added and the steel without Al;

FIG. 5 is a micrograph showing a cross section of a billet of a conventional Al-free steel.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Odone 3-10-15 Yawata-cho, Shinminato-shi, Toyama Japan High Frequency Steel Industry Co., Ltd.Examiner, Toyama Works, Takeshi Ogawa (56) References JP 63-280960 (JP, A) JP-A-63-140066 (JP, A) JP-A-7-179985 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 -38/60

Claims (2)

(57) [Claims] 1. C .: 0.4 to 0.7% by weight, S
i: 0.1-1%, Mn: 0.1-1%, Cr: 5-1
An alloy steel for a piston ring containing 0%, Al: 0.3 to 1%, and Cu: 0.2 to 1.2%, with the balance being Fe and impurities. 2. C: 0.4-0.7% by weight, S
i: 0.1-1%, Mn: 0.1-1%, Cr: 5-1
An alloy for a piston ring , characterized in that a chemical composition containing 0%, Al: 0.3-1%, Cu: 0.2-1.2%, and the balance being Fe and impurities is subjected to nitriding treatment. Steel production method.