JP2001271144A - Martensitic stainless steel for piston ring and deformed wire for piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide martensitic stainless steel by which the scuffing resistance and fatigue resistance of a piston ring can be improved compared to the conventional one without increasing its cost. SOLUTION: This martensitic stainless steel for a piston ring has a composition containing, by mass, 0.30 to 0.75% C, 14 to 19% Cr, 0.05 to 0.19% N, <=0.5% Si, <=0.5% Mn, <=0.05% P and <=0.05% S, in which 20<=Cr(%)/(C(%)+N(%))<=35 is also satisfied, and the range of N(%) satisfies α-0.05<=N(%)<=α+0.07 prescribed by (α); wherein, α=0.883×10 (0.046×Cr(%)-0.13×C(%)-1.57), and the rest composed of Fe with impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a martensitic stainless steel for a piston ring having both excellent scuffing resistance and fatigue resistance and a deformed wire for a piston ring using the martensitic stainless steel.

[0002]

2. Description of the Related Art In a material for a piston ring used in an internal combustion engine, in addition to hot and cold drawing, drawing, rolling workability and bending workability after heat treatment of a wire rod after hot rolling, a piston rod material is used. Scuffing resistance and wear resistance of the ring are important.
JP-A-07-107 and JP-A-11-106874 disclose that, in order to improve the characteristics required for these piston rings, the Cr / C is adjusted to reduce the particle size of the carbide and to control the distribution thereof. Discloses an invention capable of achieving more excellent scuffing resistance and workability.

Further, Japanese Patent Application Laid-Open Nos. 9-287053 and 9-287058 disclose that by adding nitrogen to martensitic stainless steel, coarse carbides can be reduced and corrosion resistance, abrasion resistance, toughness, An invention that improves fatigue life is disclosed.

[0004]

As environmental measures are being promoted on a worldwide scale, emission regulations for internal combustion engines have become more stringent, and there has been a demand for more efficient combustion of engines. Along with this, the conditions required for the scuffing resistance and the fatigue resistance of the piston ring have become increasingly severe.
However, the conventional method of using martensitic stainless steel, controlling the size and amount of carbides, and performing nitriding treatment does not provide sufficient scuffing resistance and fatigue resistance characteristics, making it difficult to meet severe operating conditions. It has become to.

[0005] The present invention provides a martensitic stainless steel for a piston ring and a martensitic stainless steel for a piston ring which can improve the scuffing resistance and fatigue resistance of the piston ring without increasing the cost compared to the prior art. It is an object of the present invention to provide a deformed wire for a piston ring used.

[0006]

In order to achieve the above-mentioned object, the first invention of the present application is based on the present invention, wherein C: 0.30-0.
75%, Cr: 14 to 19%, N: 0.05 to 0.19
%, Si: 0.5% or less, Mn: 0.5% or less, P:
0.05% or less, S: 0.05% or less, and 20 ≦ C
r (%) / (C (%) + N (%)) ≦ 35,
(%) Satisfies the following formulas (1) and (2) defined by α, and α-0.05 ≦ N (%) ≦ α + 0.07 (1) α = 0.883 × 10 ＾ (0.046 × Cr (%) − 0.13 × C (%) − 1.57) (2) Martens for piston rings characterized in that the balance contains Fe and impurities. It is a site-based stainless steel.

Further, a second invention of the present application for achieving the above-mentioned object is the above-mentioned first invention, wherein the mass%
o: 1.5% or less, W: 0.8% or less, V: 1.0% or less, containing one or more of the following, with the balance being Fe
And martensitic stainless steel for piston rings, characterized by containing impurities.

Further, a third invention of the present application is a deformed wire for a piston ring using the martensitic stainless steel for a piston ring of the first invention or the second invention. Here, the deformed line means that the cross-sectional shape is a track shape, square,
It refers to a striatum having a shape other than a circle such as a rectangle, a C shape, and an I shape.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail. In the present invention, the scuffing resistance and fatigue resistance of a piston ring using martensitic stainless steel are not increased compared with the conventional one. As a result of intensive studies to improve the quality of the steel, nitrogen was added to the martensitic stainless steel in the range of 20 ≦ Cr (%) / (C (%) + N (%)) ≦ 35 and α−0.05. ≦ N (%) ≦ α + 0.07 (1) α = 0.883 × 10 ＾ (0.046 × Cr (%) − 0.13 × C (%) − 1.57) (2) It has been found that by adding nitrogen in combination with carbon within the condition range defined by α, both fatigue characteristics and scuffing resistance after nitriding treatment are simultaneously improved.

[0010] By using a martensitic stainless steel to which nitrogen is compounded and added in the above range, both scuffing resistance and fatigue resistance can be improved with respect to a conventional martensitic stainless steel. It is possible to provide a piston ring material that can withstand severe use conditions without increasing the cost. Hereinafter, the above components of the present invention will be described in detail.

The content of C (% by mass, hereinafter the same) is 0.3
0 to 0.75%. If the C content is less than 0.30%, excellent hardening hardness and excellent scuffing resistance by quenching and tempering cannot be obtained in a composite addition with nitrogen. On the other hand, the reason why the content is set to 0.75% or less is that if the content exceeds this range, coarsening of the carbide particle size and increase in the amount of carbide will not be achieved, and excellent fatigue life will not be obtained.

The content of Cr is 14 to 19%. Cr
Is set to 19% or less, if added in excess of this, an increase in the amount of carbides and an increase in the particle size of the carbides are caused, and a good fatigue life cannot be obtained. Preferably, an addition of 18% or less is recommended. Further, the reason why the content of Cr is set to 14% or more is that if the content is less than 14%, required scuffing resistance cannot be obtained. Preferably, an addition of 15% or more is recommended.

[0013] The N content is 0.05 to 0.19%. N is set to 0.05% or more because if it is less than this, the carbide particle size becomes coarse and excellent fatigue characteristics cannot be obtained. Further, the reason for setting the content to 0.19% or less is that when a large amount of nitrogen exceeding this is added, a large amount of pores are introduced into the steel ingot.

Further, the following formulas (1) and (2) wherein the range of N (%) is defined by α: α-0.05 ≦ N (%) ≦ α + 0.07 (1) α = 0.883 × 10 ＾ (0.046 × Cr (%) − 0.13 × C (%) − 1.57) (2) N (%) is calculated by the above (1),
Formula (2) is specified because if N (%) is less than α-0.05, the carbide grain size becomes coarse and excellent fatigue characteristics cannot be obtained. If it exceeds 07, a large amount of pores will be introduced into the steel ingot, and excellent fatigue characteristics cannot be obtained.

20 ≦ Cr (%) / (C (%) + N
(%)) ≦ 35. Cr (%) / (C (%) + N
(%)) Is set to 20 or more. If the value is less than 20%, coarsening of the carbide particle size and increase in the amount of carbides may be caused, and excellent fatigue life cannot be obtained. Also, Cr (%) / (C (%) + N
(%)) Is set to 35 or less, because if it exceeds this, excellent hardening hardness and excellent scuffing resistance by quenching and tempering cannot be obtained.

The content of each of Si and Mn is 0.5%
The following is assumed. Si is an element useful as a deoxidizing agent for steel, and is added in a small amount for deoxidation. However, if added in a large amount, cold workability is reduced, so the upper limit is made 0.5%. Mn is a useful element as a deoxidizing agent for steel, and is added in a small amount for deoxidation. However, when added in a large amount, the cold workability is reduced, so the upper limit is made 0.5%.

The contents of P and S are each set to 0.05% or less. P is an element that segregates at the grain boundary to reduce ductility. Therefore, it is desirable that the content is low, but extremely lowering increases the manufacturing cost, so the upper limit is made 0.05% as an allowable range. Further, if the content of S is large, the hot workability is reduced, so that the content is desirably low. However, if the content is extremely reduced, the production cost is increased. Therefore, the upper limit is set to 0.05% as an allowable range.

Mo, W, and V are useful elements for improving wear resistance, but excessive addition of Mo causes deterioration of workability. Therefore, the upper limits of Mo: 1.5% or less, and W:
0.8% or less, V: 1.0% or less.

The martensitic stainless steel for the piston ring is formed into a filament by hot rolling.
Cold drawing, cold drawing / rolling, and heat treatment are performed to obtain a deformed wire for piston rings having desired physical properties.

[0020]

EXAMPLE 10 kg melted in an air atmosphere or nitrogen atmosphere using a high-frequency vacuum melting furnace and adjusted to a predetermined composition
An ingot was made. Next, the steel ingot was formed into a rod-shaped material having a diameter of 20 mm by hot working, and annealed at 860 ° C.
Table 1 shows the chemical composition of the obtained annealed material. In addition, Cr
(%) / (C (%) + N (%)), α value and N
(%)-Α value.

[0021]

[Table 1]

Table 2 shows the results of the quenching and tempering hardness and fatigue life of each steel as characteristics of the quenched and tempered material and the values of the scuffing surface pressure indicating the nitriding hardness and scuffing resistance as the characteristics of the nitrided material. Show.

[0023]

[Table 2]

In 15Cr steel and 17Cr steel, Cr
It can be seen that, in the case where the value of / (C + N) was made substantially constant and the nitrogen and carbon were changed, the larger the amount of added nitrogen, the better the scuffing resistance and fatigue characteristics. Further, when the N (%)-α value exceeds 0.05 in the melting in the air atmosphere, cavities are formed in the steel ingot and cannot be used as a product. , There is no porosity even at 0.05 or more, indicating that a steel excellent in scuffing resistance and fatigue resistance is obtained.

FIG. 1 is a diagram showing the relationship between the fatigue life and the scuffing surface pressure in Table 2. FIG. 1 shows that the steel of the present invention has both improved scuffing resistance and fatigue resistance as compared with the comparative example.

The scuffing test was performed with a diameter of 20 m.
After quenching a test piece material produced by machining from a rod-shaped material of m in the range of 950 to 1100 ° C, the hardness is 35 to
After tempering in the range of 500 to 700 ° C. so as to attain 45 HRC and nitriding at 570 ° C. × 360 min, the test piece measurement surface shape φ5.7 mm was measured by a friction and wear tester (pin-on-disk method). , Test load 196N
From each 98.1N steps (holding each load 3min), test speed 8m / s, lubricating motor oil # 30, oil temperature 80 ° C, oil spraying 400cc / min, mating material FC2
50.

The fatigue characteristics were as follows. A test piece material prepared by machining a rod-shaped material having a diameter of 20 mm was tested for hardness of 40 mm.
Using a No. 5 smooth test piece (φ6 mm) heat-treated to HRC ± 1, using an Ono-type rotary bending fatigue tester at a rotation speed of 3400 rpm, a load lever length of 200 mm, and a repetitive stress of 882.6 N / mm ² Carried out.

Next, the invention steels N0.5 and N
Actually, (thickness dimension) × (width dimension) is calculated using 0.7.
A deformed wire for a piston ring having a square shape of 5 × 3.5 mm and a square shape was manufactured. Then, as a result of investigating the workability and finished physical properties, it was confirmed that there was no problem.

[0029]

Since the present invention has the above configuration,
If this is applied to a piston ring, the cost will increase. Without using PVD, excellent scuffing resistance and fatigue characteristics (fatigue life) are obtained by conventional inexpensive nitriding treatment.
Are exhibited at a level not obtained by conventional nitriding applications. Therefore, there is an effect that its industrial advantage is high.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between fatigue life and scuffing surface pressure.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toju Onaka 3-10-15, Yawata-cho, Shinminato-shi, Toyama Japan High-frequency Steel Industry Co., Ltd. Toyama Works F-term (reference) 3J044 AA01 AA02 AA18 BA03 BC06 DA09

Claims (3)

[Claims] C: 0.30 to 0.75% by mass%,
Cr: 14 to 19%, N: 0.05 to 0.19%, S
i: 0.5% or less, Mn: 0.5% or less, P: 0.05
% Or less, S: 0.05% or less, and 20 ≦ Cr (%) / (C (%) + N (%)) ≦ 35, and the range of N (%) is defined by α as follows: 1),
(2), α-0.05 ≦ N (%) ≦ α + 0.07 (1) α = 0.883 × 10８３ (0.046 × Cr (%) − 0.13 × C (%)-1.57) (2) Martensitic stainless steel for piston rings, the balance of which contains Fe and impurities. 2. Mo: 1.5% or less, W:
2. The martensitic stainless steel for a piston ring according to claim 1, wherein one or more of 0.8% or less and V: 1.0% or less are contained, and the balance contains Fe and impurities. steel. 3. A deformed wire for a piston ring using the martensitic stainless steel for a piston ring according to claim 1 or 2.