JP7467783B1 - Pressure Ring Wire - Google Patents

Abstract

[Problem] To provide a wire 2 that can provide a compression ring with excellent roundness. [Solution] The wire 2 for a compression ring has an upper surface 4, a lower surface 6, a first side surface 8, a second side surface 10, and a rounded chamfer 12. The contour of the wire 2 in a plane perpendicular to the length direction has three arcs on its outer periphery. The wire 2 is subjected to coiling or the like to form a compression ring. The first side surface 8 corresponds to the outer periphery of the compression ring. The filtered centerline waviness WCA of the first side surface 8 measured along the length direction is 3.0 μm or less. The maximum deviation Dif between the contour of the first side surface 8 and a virtual curve approximating this contour is 2.8 μm or less. The sum of the filtered centerline waviness WCA and the maximum deviation Dif is 5.2 μm or less. [Selected Figure] Figure 2

Description

This specification discloses a wire for a pressure ring that is attached to a piston of an internal combustion engine.

The internal combustion engine has a cylinder, a piston, a pressure ring, and an oil ring. The pressure ring is attached to the piston. The pressure ring is obtained by coiling a wire. An example of a wire for a pressure ring is disclosed in JP 2008-50649 A.

JP 2008-50649 A

Circularity is important for compression rings. In an internal combustion engine with a highly circular compression ring, there is less gas leakage between the compression ring and the cylinder. A highly circular compression ring can adequately scrape off lubricating oil. From the standpoint of low fuel consumption and reduced consumption of lubricating oil, improved circularity is desirable.

The compression ring can be obtained by forming a coating on a ring-shaped intermediate product and polishing this coating. Polishing the coating also adjusts the roundness of the compression ring. When polishing an intermediate product with a thin coating, the amount of polishing required is small. When polishing an intermediate product with a thin coating, the adjustment of roundness by polishing is not sufficient.

The applicant's intention is to provide a wire that can produce a pressure ring with excellent roundness.

This specification discloses a line for a pressure ring of an internal combustion engine. The contour of the line in a plane perpendicular to the length direction has three or more arcs on its outer periphery. The filtered centerline waviness (WCA) of the surface corresponding to the outer periphery of the pressure ring measured along the length direction of the line is 3.0 μm or less.

This line can produce a highly circular pressure ring.

FIG. 1 is a perspective view showing a portion of a wire for a compression ring according to one embodiment. FIG. 2 is an enlarged cross-sectional view taken along line II-II of FIG. FIG. 3 is a chart showing the results of measuring the contour shape of a portion of the cross section of FIG. FIG. 4 is a chart showing the measurement results of the contour shape of a portion of the cross section of FIG. 2 together with a virtual curve. FIG. 5 is an enlarged view of a portion of the chart of FIG. FIG. 6 is a front view showing a test piece used to measure the twist angle of the wire for the compression ring of FIG. 1. FIG. 7 is an enlarged right side view of the test piece of FIG. FIG. 8 is a front view showing a method for measuring the warpage of the wire for the compression ring of FIG. FIG. 9 is a flow chart showing a method for manufacturing the wire for the compression ring of FIG. FIG. 10 is a cross-sectional view showing a portion of a wire for a compression ring according to another embodiment. FIG. 11 is a cross-sectional view showing a portion of a wire for a compression ring according to still another embodiment.

A preferred embodiment will be described in detail below, with reference to the drawings as appropriate.

1 and 2 show a wire 2 for a compression ring. The wire 2 has an upper surface 4, a lower surface 6, a first side surface 8, and a second side surface 10. The wire 2 further has a first rounded chamfer 12a and a second rounded chamfer 12b. The first rounded chamfer 12a is located between the upper surface 4 and the first side surface 8. The second rounded chamfer 12b is located between the first side surface 8 and the lower surface 6. The shape of the wire 2 is called a "barrel shape." The wire 2 is coiled or the like to form a compression ring. The first side surface 8 corresponds to the outer circumferential surface of the compression ring. In an internal combustion engine, this outer circumferential surface rubs against the inner circumferential surface of the cylinder.

The filtered centerline waviness WCA of the first side surface 8 is 3.0 μm or less. As described later, this line 2 can produce a pressure ring with a high degree of circularity on the outer circumferential surface. In an internal combustion engine having a pressure ring with high circularity, gas leakage between the pressure ring and the cylinder can be suppressed. This pressure ring can contribute to low fuel consumption of the internal combustion engine. Furthermore, in this internal combustion engine, the pressure ring can sufficiently scrape off lubricating oil. This pressure ring can contribute to reducing the consumption of lubricating oil. From these viewpoints, the filtered centerline waviness WCA is more preferably 2.7 μm or less, and particularly preferably 2.5 μm or less. The smaller the filtered centerline waviness WCA, the better.

The filtered centerline waviness WCA is measured along the length of the compression ring wire 2. The measurement conditions are as follows:
Measuring instrument: Tokyo Seimitsu's "SURFCOM 1500DX3"
Stylus: DM83502
Parameter calculation standard: JIS '82 standard Measurement type: filtered center line waviness Cutoff type: 2RC Phase compensation correction: least squares straight line Measurement span: 90 mm
Cutoff wavelength High pass filter: 0.8 mm
Low pass filter: 25 mm
Measurement speed: 3.0 mm/s
Magnification: Vertical: 5000 times Horizontal: 1 time Output parameters: WCC-m
In the chart output by this measuring device, the vertical axis represents the amount of waviness, and the horizontal axis represents the longitudinal distance of the line 2. The distance between a straight line passing through the maximum point of the curve of this chart and a straight line passing through the minimum point of this curve is the filtered centerline waviness WCA.

The maximum deviation Dif between the contour of the first side surface 8 in FIG. 2 and the virtual curve approximating this contour is preferably 2.8 μm or less. As described below, this line 2 can produce a compression ring with a high degree of circularity on the outer circumferential surface. This compression ring can contribute to low fuel consumption of the internal combustion engine and reduced consumption of lubricating oil. From these viewpoints, the maximum deviation Dif is more preferably 2.7 μm or less, and particularly preferably 2.5 μm or less. The smaller the maximum deviation Dif, the better.

In measuring the maximum deviation Dif, first, the contour of the line 2 in a plane perpendicular to the length direction is measured by a contour shape measuring device. The measurement conditions are as follows.
Measuring instrument: Tokyo Seimitsu's "SURFCOM 2000DX3"
Stylus: DM47513
Travel speed: 0.030 mm/s
Measurement speed: 0.030 mm/s
Measurement pitch: 0.10 μm

Figure 3 shows the contour 14 of the first side surface 8. Figure 3 also shows a contour 16 of a portion of the upper surface 4 and a contour 18 of a portion of the lower surface 6. Figure 4 also shows a virtual curve 20 that approximates the contour 14 of the first side surface 8. This virtual curve 20 is a quadratic curve calculated by the least squares method.

In FIG. 5, the contour 14 and the virtual curve 20 are shown enlarged. In FIG. 5, the symbol P1 represents the point on the contour 14 of the first side surface 8 that is the greatest distance from the virtual curve 20. The distance between this point P1 and the virtual curve 20 is the maximum deviation Dif mentioned above. In the example of FIG. 5, point P1 is located above the virtual curve 20. Point P1 can be located below the virtual curve 20.

The sum of the filtered center line waviness WCA and the maximum deviation Dif is 5.2 μm or less. From this line 2, a compression ring with high circularity of the outer circumferential surface can be obtained. This compression ring can contribute to low fuel consumption of internal combustion engines and reduced consumption of lubricating oil. From these viewpoints, this sum is more preferably 4.9 μm or less, and particularly preferably 4.4 μm or less. The smaller this sum, the better.

Preferably, the twist angle of the wire 2 for the compression ring is 3°/m or less. From this wire 2, a compression ring with a high degree of circularity of the outer circumferential surface can be obtained. This compression ring can contribute to low fuel consumption of the internal combustion engine and reduced consumption of lubricating oil. From these viewpoints, the twist angle is more preferably 2°/m or less, and particularly preferably 1°/m or less. The smaller the twist angle, the better.

To measure the twist angle, a test piece is used, which is obtained by bending the wire 2 for the compression ring at a right angle. This test piece 22 is shown in Figures 6 and 7. This test piece 22 has a base portion 24 and an upright portion 26. The angle between the base portion 24 and the upright portion 26 is substantially 90°. The length of the base portion 24 is 1000 mm. The height of the upright portion is 90 mm. The base portion 24 is placed on a base 28. In Figure 7, the symbol θ is the angle of the upright portion 26 with respect to the base 28.

As shown by arrow A1 in FIG. 6, the angle θ is measured with the end of the base portion 24 pressed downward. This angle is called the first angle θ1. In FIG. 6, the angle θ is measured with the end of the base portion 24 pressed downward as shown by arrow A1, while the base portion 24 is pressed downward near the boundary between the base portion 24 and the upright portion 26 as shown by arrow A2. This angle is called the second angle θ2. The difference (θ1-θ2) between the first angle θ1 and the second angle θ2 is calculated. The absolute value of this difference (θ1-θ2) is the twist angle of this compression ring wire 2.

Preferably, the warp of the wire 2 for the compression ring is 15 mm/m or less. From this wire 2, a compression ring with a high degree of roundness of the outer circumferential surface can be obtained. This compression ring can contribute to low fuel consumption of the internal combustion engine and reduced consumption of lubricating oil. From these viewpoints, the warp is more preferably 10 mm/m or less, and particularly preferably 7 mm/m or less. The smaller the warp, the better.

To measure the warpage, a test piece obtained by cutting the wire 2 for the compression ring is used. The length of this test piece is 1000 mm. As shown in FIG. 8, one end 32 of this test piece 30 is fixed to a plate 34 extending in the vertical direction. This fixation causes the test piece 30 to hang down under its own weight. The distance L1 between the other end 36 of this test piece 30 and the plate 34 is measured. This distance L1 is called the warpage.

Figure 9 shows an example of a manufacturing method for the wire 2 for the compression ring. In this manufacturing method, first, a basic wire is prepared (STEP 1). This basic wire is obtained through processes such as steelmaking, refining, casting, hot rolling, and annealing. The cross-sectional shape of this basic wire is a circle.

This raw wire is then cold drawn (STEP 2). This cold drawing gradually reduces the diameter of the raw wire and gradually lengthens it. The cross-sectional shape of the wire after cold drawing (STEP 2) is circular.

This wire is subjected to heat treatment (STEP 3). When the wire is made of carbon steel, a typical heat treatment is patenting. Patenting is a heat treatment in which a wire heated to the austenite region is cooled to obtain a fine pearlite structure. Patenting restores the ductility of the wire that was lost by cold drawing (STEP 2). Cold drawing (STEP 2) and heat treatment (STEP 3) may be repeated. An intermediate wire is obtained by these processes.

This intermediate wire is cold rolled (STEP 4). This rolling produces an intermediate deformed wire. The cross-sectional shape of this intermediate deformed wire is not circular.

This intermediate wire is subjected to cold deformed wire drawing (STEP 5). In this deformed wire drawing, the intermediate wire is passed through a die. Typically, a lubricant is supplied between the intermediate wire and the die. This deformed wire is obtained by this deformed wire drawing. This deformed wire has the cross-sectional shape shown in Figure 2.

This deformed wire is then subjected to thermal straightening (STEP 6). This thermal straightening relieves the stress that was generated in the deformed wire by the deformed wire drawing (STEP 5).

The shaped wire is then subjected to quenching (STEP 7). In quenching, the shaped wire is first heated. During this heating, the temperature of the shaped wire reaches the austenite region. Then, the shaped wire is quenched. Preferably, the shaped wire is cooled in oil. After quenching, the shaped wire has a martensite structure.

The shaped wire is then tempered (STEP 8). In tempering, the shaped wire is first heated. Then, the shaped wire is cooled. Tempering can produce a structure in which fine carbides are precipitated. Tempering produces the wire for compression ring 2 shown in Figures 1 and 2.

This wire 2 is coiled to obtain a ring. This ring is then subjected to a distortion-relieving heat treatment. A coating is then formed on the outer circumferential surface of this ring. Part of this coating is then removed by polishing to obtain a compression ring.

Preferably, the processing rate in the deformed wire drawing (STEP 5) is 18.0% or more. This deformed wire drawing is a high degree of cold plastic processing. This deformed wire drawing can produce a wire 2 for a compression ring with a small filtered center line waviness WCA. Furthermore, this deformed wire drawing can produce a wire 2 for a compression ring with a small maximum deviation Dif. From these viewpoints, the processing rate in the deformed wire drawing (STEP 5) is more preferably 20.0% or more, and particularly preferably 20.6% or more. The processing rate is preferably 22.0% or less.

The degree of processing R is calculated by the following formula.
R = (S1 - S2) / S1 * 100
In this formula, S1 is the cross-sectional area of the intermediate profile wire, and S2 is the cross-sectional area of the profile wire.

As described above, the wire 2 for a compression ring can be obtained with a small filtered centerline waviness WCA and a small maximum deviation Dif by the deformed wire drawing (STEP 5) with a large degree of processing. In the ring obtained from this wire 2, the upper surface 4 and the lower surface 6 are almost perpendicular to the axial direction of the ring. In this ring, only a small amount of polishing of the coating is required to adjust the roundness. In this ring, a thin coating before polishing is sufficient. A method suitable for forming a thin coating can be adopted for manufacturing this compression ring. Typical methods suitable for forming a thin coating are physical vapor deposition (PVD) and chemical vapor deposition (CVD). Physical vapor deposition and chemical vapor deposition have a smaller load on the environment than plating methods, etc. By adopting physical vapor deposition or chemical vapor deposition, a coating that is hard and has excellent wear resistance can be formed. A manufacturing method that requires only a small amount of polishing of the coating is also low cost.

Preferably, the surface roughness Rz of the intermediate deformed wire subjected to the deformed wire drawing (STEP 5) is 5.0 μm or more. This intermediate deformed wire enters the die accompanied by a sufficient amount of lubricant. This lubricant can suppress the occurrence of defects in the deformed wire drawing. In this deformed wire drawing, defects are unlikely to occur despite the large degree of processing. By using a manufacturing method including this deformed wire drawing (STEP 5), a wire 2 for a compression ring can be obtained that has a small filtered center line waviness WCA, a small maximum deviation Dif, and few defects. From this viewpoint, the surface roughness Rz of the intermediate deformed wire is more preferably 5.5 mm or more, and particularly preferably 6.0 mm or more. From the viewpoint of a good surface state of the wire 2 for a compression ring, the surface roughness Rz of the intermediate deformed wire is preferably 10.0 μm or less.

In this specification, the term "surface roughness Rz" refers to the ten-point average roughness defined in "JIS B0601-1982." The conditions for measuring the surface roughness Rz are as follows.
Measuring device: Tokyo Seimitsu's "SURFCOM TOUCH 550-12"
Stylus: E-DT-SS01B
Parameter calculation standard: JIS '82 standard Measurement speed: 0.06 mm/s
Shape removal: Straight line Cutoff value: None Output parameter: Rz

The surface roughness Rz of the intermediate irregular wire depends on the surface roughness Rz of the roller used in rolling (STEP 4). From the viewpoint of being able to achieve a sufficiently large surface roughness Rz of the intermediate irregular wire, the surface roughness Rz of the roller is preferably 5.0 μm or more, more preferably 5.5 μm or more, and particularly preferably 6.0 μm or more. From the viewpoint of a good surface condition of the wire 2 for the pressure ring, the surface roughness Rz of the roller is preferably 10.0 μm or less.

The large degree of processing in the deformed wire drawing (STEP 5) can contribute to excellent surface smoothness of the deformed wire. Therefore, even if an intermediate deformed wire with a surface roughness Rz of 5.0 μm or more is subjected to deformed wire drawing, a deformed wire with a small surface roughness Rz can be obtained. From this deformed wire, a wire 2 for a pressure ring with a small surface roughness Rz can be obtained. In the ring obtained from this wire 2 for a pressure ring, uneven polishing of the coating is unlikely to occur. From this viewpoint, the surface roughness Rz of the deformed wire and the wire 2 for a pressure ring is preferably 3.0 μm or less, more preferably 2.5 μm or less, and particularly preferably 2.3 μm or less. The smaller the surface roughness Rz, the better.

The large degree of processing in the deformed wire drawing (STEP 5) promotes stress concentration in the deformed wire. This stress concentration can lead to a large twist angle and large winding warpage. As mentioned above, the thermal straightening (STEP 6) relieves the stress generated in the deformed wire by the deformed wire drawing (STEP 5). A manufacturing method including the thermal straightening (STEP 6) can produce a wire 2 for compression rings with a small twist angle and small winding warpage.

In the preferred thermal straightening (STEP 6), the profiled wire is exposed to an atmosphere having a temperature of 245°C or more and 255°C or less for a period of 2.5 seconds or more and 3.5 seconds or less. Thermal straightening (STEP 6) is performed prior to quenching (STEP 7).

As shown in FIG. 2, the cross-sectional shape of the first side surface 8 of the wire 2 for the compression ring is a circular arc. Furthermore, as described above, this wire 2 has a first rounded chamfer 12a and a second rounded chamfer 12b. The shape of each of these rounded chamfers is a circular arc. The number of arcs on the outer periphery of the cross section of this wire 2 is three. The "arcs on the outer periphery" are the arc of the first side surface 8, the arc sandwiched between the upper surface 4 and the first side surface 8, and the arc sandwiched between the lower surface 6 and the first side surface 8.

The cross-sectional shape of this wire 2 is close to that of a compression ring. A compression ring can be obtained from wire 2 having this cross-sectional shape by low-level polishing. On the other hand, the cross-sectional shape of wire 2 having three or more arcs on the outer periphery is complex. In the deformed wire drawing (STEP 5) for wire 2 having this cross-sectional shape, stress concentration is likely to occur in the deformed wire. In particular, when deformed wire drawing (STEP 5) with a large processing degree R is performed with the intention of achieving a small filtered center line waviness WCA, stress concentration is likely to occur. Thermal straightening (STEP 6) is particularly useful for manufacturing wire 2 for a compression ring having three or more arcs on the outer periphery.

The material of the wire 2 for the compression ring is steel.
The steel contains C: 0.51% by mass to 0.85% by mass, Si: 0.15% by mass to 1.60% by mass, Mn: 0.30% by mass to 0.90% by mass, Cr: 0.80% by mass or less, Ni: 0.02% by mass or less, P: 0.08% by mass or less, S: 0.05% by mass or less, and Cu: 0.20% by mass or less. Preferably, the balance is Fe and unavoidable impurities. The content of alloy elements in this steel is low. This steel can be obtained at low cost. The role of each element will be described in detail below.

[Carbon (C)]
C contributes to the hardness and fatigue strength of the compression ring. From these viewpoints, the C content is preferably 0.51 mass% or more, more preferably 0.53 mass% or more, and particularly preferably 0.55 mass% or more. Excess C inhibits the workability in rolling (STEP 4) and deformed wire drawing (STEP 5). From the viewpoint of cold workability, the C content is preferably 0.85 mass% or less, more preferably 0.75 mass% or less, and particularly preferably 0.65 mass% or less.

[Silicon (Si)]
Si contributes to the heat resistance and high-temperature strength of the compression ring. From these viewpoints, the Si content is preferably 0.15 mass% or more, more preferably 0.18 mass% or more, and particularly preferably 0.20 mass% or more. Excessive Si inhibits the workability in rolling (STEP 4) and deformed wire drawing (STEP 5). Excessive Si further inhibits the toughness of the compression ring. From the viewpoints of cold workability and toughness, the Si content is preferably 1.60 mass% or less, more preferably 1.50 mass% or less, and particularly preferably 1.45 mass% or less.

[Manganese (Mn)]
Mn is added as a deoxidizer during steelmaking for raw wire. Mn can fix S. From these viewpoints, the Mn content is preferably 0.30 mass% or more, more preferably 0.40 mass% or more, and particularly preferably 0.50 mass% or more. Excess Mn inhibits workability in rolling (STEP 4) and deformed wire drawing (STEP 5). From the viewpoint of cold workability, the Mn content is preferably 0.90 mass% or less, more preferably 0.80 mass% or less, and particularly preferably 0.75 mass% or less.

[Chromium (Cr)]
Cr can precipitate as carbides. These carbides can contribute to the wear resistance of the compression ring. From this viewpoint, the Cr content is preferably 0.30 mass% or more, more preferably 0.40 mass% or more, and particularly preferably 0.50 mass% or more. Excess Cr inhibits the toughness of the wire 2 for the compression ring. When the wire 2 containing excess Cr is coiled, the wire 2 may break. From the viewpoint of toughness, the Cr content is preferably 0.80 mass% or less, more preferably 0.75 mass% or less, and particularly preferably 0.70 mass% or less. Cr is not an essential element. Therefore, the Cr content may be below the detection limit.

[Nickel (Ni)]
Ni can contribute to the toughness of the compression ring. From this viewpoint, the Ni content is preferably 0.05 mass% or more, more preferably 0.10 mass% or more, and particularly preferably 0.15 mass% or more. Excess Ni causes austenite to remain in the structure of the compression ring. The hardness of the compression ring containing the retained austenite is insufficient. From the viewpoint of hardness, the Ni content is preferably 0.02 mass% or less, and particularly preferably 0.01 mass% or less. Ni is not an essential element. Therefore, the Ni content may be below the detection limit.

[Phosphorus (P)]
P is an impurity. P segregates in the compression ring and impairs the toughness of the compression ring. From the viewpoint of toughness, the P content is preferably 0.08 mass% or less, more preferably 0.05 mass% or less, and particularly preferably 0.03 mass% or less.

[Sulfur (S)]
S is an impurity. S segregates in the compression ring and impairs the toughness of the compression ring. From the viewpoint of toughness, the S content is preferably 0.05 mass% or less, more preferably 0.03 mass% or less, and particularly preferably 0.02 mass% or less.

[Copper (Cu)]
Cu can contribute to the workability in rolling (STEP 4) and deformed wire drawing (STEP 5). From this viewpoint, the Cu content is preferably 0.05 mass% or more, more preferably 0.10 mass% or more, and particularly preferably 0.15 mass% or more. Excessive Cu inhibits hot workability. From the viewpoint of hot workability, the Cu content is preferably 0.20 mass% or less, more preferably 0.10 mass% or less, and particularly preferably 0.05 mass% or less. Cu is not an essential element. Therefore, the Cu content may be below the detection limit.

10 shows a wire 38 for a pressure ring according to another embodiment. The wire 38 has an upper surface 40, a lower surface 42, a first side surface 44, and a second side surface 46. The wire further has a first rounded chamfer 48a, a second rounded chamfer 48b, a third rounded chamfer 48c, and a fourth rounded chamfer 48d. In the wire 38, the number of arcs between the upper surface 40 and the first side surface 44 is 1, and the number of arcs between the lower surface 42 and the first side surface 44 is 3. The shape of the first side surface 44 is straight and not an arc. The number of arcs on the outer circumferential side of the cross section of the line 38 is 4. The shape of the line 38 is called a "Napier shape". The wire 38 is coiled or the like to form a pressure ring. The first side surface 44 corresponds to the outer circumferential surface of the pressure ring. In an internal combustion engine, this outer circumferential surface rubs against the inner circumferential surface of the cylinder.

In this pressure ring wire 38, the filtered center line waviness WCA is 3.0 μm or less. Furthermore, in this pressure ring wire 38, the maximum deviation Dif is 2.8 μm or less, and the sum of the maximum deviation Dif and the filtered center line waviness WCA is 5.2 μm or less. From this wire 38, a pressure ring with high circularity can be obtained.

11 shows a wire 50 for a compression ring according to another embodiment. The wire 50 has an upper surface 52, a lower surface 54, a first side surface 56, and a second side surface 58. The wire further has a first rounded chamfer 60a, a second rounded chamfer 60b, a third rounded chamfer 60c, and a fourth rounded chamfer 60d. In the wire 50, the number of arcs between the upper surface 52 and the first side surface 56 is 1, and the number of arcs between the lower surface 54 and the first side surface 56 is 3. The shape of the first side surface 56 is straight and not an arc. The number of arcs on the outer circumferential side of the cross section of the wire 50 is 4. The shape of the wire 50 is called an "undercut shape". The wire 50 is coiled or the like to form a compression ring. The first side surface 56 corresponds to the outer circumferential surface of the compression ring. In an internal combustion engine, this outer circumferential surface rubs against the inner circumferential surface of the cylinder.

In this wire 50 for a pressure ring, the filtered centerline waviness WCA is 3.0 μm or less. Furthermore, in this wire 50 for a pressure ring, the maximum deviation Dif is 2.8 μm or less, and the sum of the maximum deviation Dif and the filtered centerline waviness WCA is 5.2 μm or less. From this wire 50, a pressure ring with high circularity can be obtained.

The effects of the wire for the compression ring according to the embodiment will be explained below, but the scope of the disclosure in this specification should not be interpreted as being limited based on the description of this embodiment.

[Example 1]
A steel material having the composition A shown in Table 1 below was subjected to the treatment shown in FIG. 9 to obtain a wire for a barrel-type compression ring having the shape shown in FIGS. 1 and 2. The equivalent diameter of the intermediate deformed wire after rolling (STEP 4) was 2.03 mm. The equivalent diameter of the deformed wire after deformed wire drawing (STEP 5) was 1.80 mm. The processing rate was therefore 21.4%. The surface roughness Rz of the intermediate deformed wire after rolling (STEP 4) was 9.5 μm. The surface roughness Rz of the wire for a compression ring after tempering (STEP 8) was 2.1 μm. In this wire for a compression ring, the filtered center line waviness WCA was 1.5 μm and the maximum deviation Dif was 2.2 μm. In this wire for a compression ring, the thickness was 1.03 mm and the width was 2.70 mm.

[Examples 2 to 9 and Comparative Examples 1 and 2]
Wires for compression rings of Examples 2-9 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that the production conditions were as shown in Table 2 below.

[Rolling]
Using the method shown in Fig. 8, the warpage of the profiled wire after profile drawing (STEP 5), the profiled wire after thermal straightening (STEP 6), and the wire for compression ring after tempering (STEP 8) was measured. The results are shown in Table 3 below.

[Twist angle]
6 and 7, the twist angles of the deformed wire after deformed wire drawing (STEP 5), the deformed wire after thermal straightening (STEP 6), and the wire for compression ring after tempering (STEP 8) were measured. The results are shown in Table 3 below. The wires for compression rings of Examples 7 and 8 and Comparative Examples 1 and 2 were obtained without thermal straightening (STEP 6).

[Circularity]
The wire for the compression ring was coiled to obtain a ring. The circularity of the ring was evaluated by a light leakage test and rated according to the following criteria.
A: Very good B: Good C: Fairly good D: Poor The results are shown in Table 3 below.

[Polishing residue]
The wire for the compression ring was coiled to obtain a ring. The ring was then subjected to arc ion plating (AIP) to form a coating. The coating was then polished to obtain a compression ring. The appearance of the compression ring was visually observed to determine whether there was any polishing residue. The results are shown in Table 3 below.

As shown in Table 3, the wires for compression rings in each embodiment have excellent performance. From these evaluation results, the superiority of this wire for compression rings is clear.

[Disclosure items]
Each of the following sections discloses a preferred embodiment.

[Item 1]
A wire for a pressure ring of an internal combustion engine, comprising:
The outline of the line in a plane perpendicular to the longitudinal direction of the line has three or more arcs on its outer periphery,
A line having a filtered centerline waviness WCA of a surface corresponding to the outer circumferential surface of the compression ring, measured along the length direction, of 3.0 μm or less.

[Item 2]
2. The line according to item 1, wherein a maximum deviation Dif between a contour of a surface corresponding to the outer circumferential surface and a virtual curve approximating this contour in a plane perpendicular to the length direction is 2.8 μm or less.

[Item 3]
3. The line according to item 2, wherein the sum of the filtered centerline waviness WCA and the maximum deviation Dif is 5.2 μm or less.

[Item 4]
4. The wire according to any one of items 1 to 3, wherein the surface roughness Rz is 3.0 μm or less.

[Item 5]
5. The wire according to any one of items 1 to 4, wherein the twist angle is 3°/m or less.

[Item 6]
6. The wire according to any one of items 1 to 5, wherein the winding warp is 15 mm/m or less.

[Item 7]
7. The wire according to any one of items 1 to 6, wherein the material is steel, and the steel contains C: 0.51% to 0.85% by mass, Si: 0.15% to 1.60% by mass, Mn: 0.30% to 0.90% by mass, Cr: 0.80% by mass or less, Ni: 0.02% by mass or less, P: 0.08% by mass or less, S: 0.05% by mass or less, and Cu: 0.20% by mass or less.

[Item 8]
(A) rolling the intermediate wire with a roller having a surface roughness Rz of 5.0 μm or more to obtain an intermediate irregularly shaped wire;
And (B) a method for manufacturing a wire for a compression ring, comprising a step of performing deformed wiredrawing on the intermediate deformed wire using a lubricant to a degree of processing of 18.0% or more and 22.0% or less to obtain a deformed wire.

[Item 9]
9. The manufacturing method according to item 8, wherein the process (B) provides a specially shaped wire having a surface roughness Rz of 3.0 μm or less.

[Item 10]
After the above step (B),
(C) subjecting the deformed wire to thermal straightening under conditions of a temperature of 245° C. or more and 255° C. or less and a time of 2.5 seconds or more and 3.5 seconds or less; and (D) subjecting the deformed wire to quenching and tempering. The manufacturing method according to item 8 or 9.

The compression ring wire described above is suitable for piston rings in various internal combustion engines.

Description of the Reference Numerals 2: Line for pressure ring 4: Upper surface 6: Lower surface 8: First side surface 10: Second side surface 12: Rounded chamfer 14: Contour of first side surface 16: Contour of upper surface 18: Contour of lower surface 20: Virtual curve 22: Test piece 24: Base 26: Standing portion 30: Test piece 34: Plate 38: Line for pressure ring 40: Upper surface 42: Lower surface 44: First side surface 46: Second side surface 48: Rounded chamfer 50: Line for pressure ring 52: Upper surface 54: Lower surface 56: First side surface 58: Second side surface 60: Rounded chamfer

Claims (7)

A wire for a pressure ring of an internal combustion engine, comprising:
The outline of the line in a plane perpendicular to the longitudinal direction of the line has three or more arcs on its outer periphery,
A line having a filtered centerline waviness WCA of a surface corresponding to the outer circumferential surface of the compression ring, measured along the length direction, of 3.0 μm or less. The wire according to claim 1, in which the maximum deviation Dif between the contour of the surface corresponding to the outer circumferential surface in a plane perpendicular to the length direction and a virtual curve approximating this contour is 2.8 μm or less. The wire according to claim 2, wherein the sum of the filtered centerline waviness WCA and the maximum deviation Dif is 5.2 μm or less. The wire according to claim 1 or 2, the surface roughness Rz of which is 3.0 μm or less. The wire according to claim 1 or 2, the twist angle of which is 3°/m or less. The wire according to claim 1 or 2, the winding warp of which is 15 mm/m or less. 3. The wire according to claim 1 or 2, wherein the material is steel, the steel containing: C: 0.51% by mass to 0.85% by mass; Si: 0.15% by mass to 1.60% by mass; Mn: 0.30% by mass to 0.90% by mass; Cr: 0.80% by mass or less; Ni: 0.02% by mass or less; P: 0.08% by mass or less; S: 0.05% by mass or less; and Cu: 0.20% by mass or less.

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