Pressure ring wire

Abstract

A pressure ring wire 2 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 wire 2 is coiled or the like to form a pressure ring. The first side surface 8 corresponds to the outer peripheral surface of the pressure ring. The filtered center line 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 the contour is 3.0 μm or less. The sum of the filtered center line waviness WCA and the maximum deviation Dif is 5.5 μm or less.

Description

Pressure ring wire

[0001] The present specification discloses a line for a pressure ring attached to a piston of an internal combustion engine.

[0002] An 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 compression ring is disclosed in Japanese Patent Application Laid-Open No. 2008-50649.

[0003] JP 2008-50649 A

[0004] Circularity is important for compression rings. In an internal combustion engine with a highly circular compression ring, gas leakage between the compression ring and the cylinder is reduced. A highly circular compression ring can sufficiently scrape off lubricating oil. From the viewpoints of low fuel consumption and reduced consumption of lubricating oil, improvement of circularity is desired.

[0005] The compression ring can be obtained by forming a coating on a ring-shaped intermediate product and polishing this coating. Polishing the coating also serves to adjust the roundness of the compression ring. When polishing an intermediate product with a thin coating, the polishing stock removal is small. When polishing an intermediate product with a thin coating, the adjustment of roundness by polishing is not sufficient.

[0006] It is the applicant's intention to provide a wire that can provide a pressure ring with excellent roundness.

[0007] This specification discloses a line for a compression ring of an internal combustion engine, in which the maximum deviation Dif between the contour of a surface corresponding to the outer peripheral surface of the compression ring and a virtual curve approximating this contour in a plane perpendicular to the length direction of the line is 3.0 μm or less.

[0008] This line allows for a highly round pressure ring to be obtained.

[0009] 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 in FIG. 1. FIG. 3 is a chart showing the results of measuring the contour shape of a portion of the cross section of FIG. 2. FIG. 4 is a chart showing the results of measuring the contour shape of a portion of the cross section of FIG. 2 together with an imaginary curve. FIG. 5 is an enlarged view of a portion of the chart of FIG. 4. FIG. 6 is a front view showing a test piece used to measure the twist angle of the wire for a compression ring of FIG. 1. FIG. 7 is an enlarged right side view of the test piece of FIG. 6. FIG. 8 is a front view showing a method for measuring the winding warp of the wire for a compression ring of FIG. 1. FIG. 9 is a flowchart showing a method for manufacturing the wire for a compression ring of FIG. 1. 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 yet another embodiment.

[0010] Hereinafter, preferred embodiments will be described in detail with reference to the drawings as appropriate.

[0011] 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." A compression ring is formed by coiling the wire 2, for example. The first side surface 8 corresponds to the outer peripheral surface of the compression ring. In an internal combustion engine, this outer peripheral surface rubs against the inner peripheral surface of a cylinder.

[0012] The maximum deviation Dif between the contour of the first side surface 8 in FIG. 2 and the virtual curve approximating this contour is 3.0 μm or less. As will be described later, this line 2 makes it possible to obtain a compression ring with a high degree of circularity on the outer circumferential surface. This compression ring can contribute to improving fuel economy of an internal combustion engine and reducing the amount of lubricating oil consumed. 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.

[0013] In measuring the maximum deviation Dif, first, the contour of the line 2 on a plane perpendicular to the length direction is measured using a contour measuring instrument. The measurement conditions are as follows: Measuring instrument: Tokyo Seimitsu Co., Ltd. "SURFCOM 2000DX3" Stylus: DM47513 Moving speed: 0.030 mm / s Measuring speed: 0.030 mm / s Measuring pitch: 0.10 μm

[0014] Fig. 3 shows the contour 14 of the first side surface 8. Fig. 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. Fig. 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.

[0015] 5 shows an enlarged view of the contour 14 and the virtual curve 20. In FIG. 5, the symbol P1 indicates 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 described above. In the example of FIG. 5, the point P1 is located above the virtual curve 20. The point P1 can also be located below the virtual curve 20.

[0016] The filtered centerline waviness WCA of the first side surface 8 is 3.0 μm or less. As will be described later, this line 2 can produce a compression ring with a highly circular outer surface. In an internal combustion engine having a highly circular compression ring, gas leakage between the compression ring and the cylinder can be suppressed. This compression ring can contribute to low fuel consumption of the internal combustion engine. Furthermore, in this internal combustion engine, the compression ring can sufficiently scrape off lubricating oil. This compression ring can contribute to reduced lubricating oil consumption. From these perspectives, 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.

[0017] The filtered centerline waviness WCA is measured along the length direction of the compression ring wire 2. The measurement conditions are as follows: Measuring instrument: Tokyo Seimitsu Co., Ltd.'s "SURFCOM 1500DX3" Stylus: DM83502 Parameter calculation standard: JIS '82 standard Measurement type: filtered centerline 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: 5000x Horizontal: 1x Output parameter: WCC-m In the chart output by this measuring instrument, the vertical axis represents the amount of waviness, and the horizontal axis represents the length direction distance of the line 2. The distance between the straight line passing through the maximum point of the curve in this chart and the straight line passing through the minimum point of this curve is the filtered centerline waviness WCA.

[0018] The sum of the filtered centerline waviness WCA and the maximum deviation Dif is 5.5 μm or less. This line 2 allows for a compression ring with a high degree of circularity on the outer circumferential surface. This compression ring can contribute to improving fuel economy of an internal combustion engine and reducing the amount of lubricating oil consumed. From these perspectives, this sum is more preferably 4.9 μm or less, and particularly preferably 4.4 μm or less. The smaller this sum, the better.

[0019] Preferably, the twist angle of the wire 2 for a 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 an 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.

[0020] To measure the twist angle, a test piece obtained by bending the compression ring wire 2 at a right angle is used. 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.

[0021] As shown by arrow A1 in Figure 6, the angle θ is measured with the end of the base portion 24 pressed downward. This angle is referred to as the first angle θ1. In Figure 6, the angle θ is measured with the end of the base portion 24 pressed downward as shown by arrow A1, and with the base portion 24 pressed downward near the boundary between the base portion 24 and the upright portion 26 as shown by arrow A2. This angle is referred to as 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.

[0022] Preferably, the warp of the wire 2 for a compression ring is 15 mm / m or less. A compression ring having a high degree of roundness of the outer peripheral surface can be obtained from this wire 2. This compression ring can contribute to low fuel consumption of an internal combustion engine and a reduction in the amount of lubricating oil consumed. 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.

[0023] A test piece obtained by cutting the compression ring wire 2 is used to measure the warpage. 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 due to 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.

[0024] 9 shows an example of a manufacturing method for the compression ring wire 2. 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 circular.

[0025] This raw wire is subjected to cold wire drawing (STEP 2). This cold wire drawing gradually reduces the diameter of the raw wire and gradually increases its length. The cross-sectional shape of the wire after cold wire drawing (STEP 2) is circular.

[0026] This wire is then 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 wire drawing (STEP 2). Cold wire drawing (STEP 2) and heat treatment (STEP 3) may be repeated. An intermediate wire is obtained by these treatments.

[0027] This intermediate wire is cold-rolled (STEP 4). By this rolling, an intermediate shaped wire is obtained. The cross-sectional shape of this intermediate shaped wire is not circular.

[0028] This intermediate shaped wire is subjected to cold shaped wire drawing (STEP 5). In this shaped wire drawing, the intermediate shaped wire is passed through a die. Usually, a lubricant is supplied between the intermediate shaped wire and the die. This shaped wire drawing results in a shaped wire. This shaped wire has the cross-sectional shape shown in FIG. 2.

[0029] This deformed wire is subjected to thermal straightening (STEP 6). In this thermal straightening, the stress generated in the deformed wire by the deformed wire drawing (STEP 5) is relieved.

[0030] The shaped wire is then quenched (STEP 7). In the quenching, the shaped wire is first heated. During the heating, the temperature of the shaped wire reaches the austenite region. Then, the shaped wire is rapidly cooled. Preferably, the shaped wire is cooled in oil. After the quenching, the shaped wire has a martensite structure.

[0031] This 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 compression ring wire 2 shown in FIGS. 1 and 2.

[0032] The wire 2 is coiled to obtain a ring. The ring is then subjected to a heat treatment to remove strain. A coating is then formed on the outer circumferential surface of the ring. Part of this coating is then removed by grinding to obtain a compression ring.

[0033] Preferably, the working ratio in the deformed wire drawing (STEP 5) is 18.0% or more. This deformed wire drawing is a high degree of cold plastic working. This deformed wire drawing can provide a wire 2 for a compression ring with a small filtered center line waviness WCA. Furthermore, this deformed wire drawing can provide a wire 2 for a compression ring with a small maximum deviation Dif. From these viewpoints, the working ratio in the deformed wire drawing (STEP 5) is more preferably 20.0% or more, and particularly preferably 20.6% or more. The working ratio is preferably 22.0% or less.

[0034] The processing rate R is calculated by the following formula: R = (S1 - S2) / S1 * 100 In this formula, S1 is the cross-sectional area of ​​the intermediate deformed wire, and S2 is the cross-sectional area of ​​the deformed wire.

[0035] As described above, the large degree of deformation in the deformed wire drawing (STEP 5) allows for the production of a wire 2 for a compression ring having a small filtered centerline waviness (WCA) and a small maximum deviation (Dif). In a ring obtained from this wire 2, the upper surface 4 and the lower surface 6 are substantially perpendicular to the axial direction of the ring. This ring requires only a small amount of polishing of the coating to adjust the roundness. This ring requires only a thin coating before polishing. A method suitable for forming a thin coating can be employed to manufacture 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 lower environmental impact than plating and other methods. By employing physical vapor deposition or chemical vapor deposition, a coating that is hard and has excellent wear resistance can be formed. Manufacturing methods that require only a small amount of polishing of the coating also result in lower costs.

[0036] Preferably, the surface roughness Rz of the intermediate deformed wire subjected to 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 during deformed wire drawing. In this deformed wire drawing, defects are less likely to occur despite the high degree of processing. A manufacturing method including this deformed wire drawing (STEP 5) can obtain a wire 2 for a compression ring having 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.

[0037] In this specification, the term "surface roughness Rz" refers to the ten-point average roughness defined in "JIS B0601-1982." The conditions for measuring surface roughness Rz are as follows: Measuring instrument: Tokyo Seimitsu's "SURFCOM TOUCH 550-12" Stylus: E-DT-SS01B Parameter calculation standard: JIS '82 standard Measuring speed: 0.06 mm / s Shape removal: straight line Cutoff value: none Output parameter: Rz

[0038] The surface roughness Rz of the intermediate irregular shaped wire depends on the surface roughness Rz of the roller used in rolling (STEP 4). From the viewpoint of achieving a sufficiently large surface roughness Rz of the intermediate irregular shaped 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 compression ring wire 2, the surface roughness Rz of the roller is preferably 10.0 μm or less.

[0039] The deformed wire drawing (STEP 5), which has a high degree of processing, 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 compression ring with a small surface roughness Rz can be obtained. Rings obtained from this wire 2 for a compression ring are less likely to have uneven polishing of the coating. From this perspective, the surface roughness Rz of the deformed wire and the wire 2 for a compression 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.

[0040] 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 a compression ring with a small twist angle and small winding warpage.

[0041] In a preferred thermal straightening step (STEP 6), the profiled wire is exposed for 2.5 seconds to 3.5 seconds in an atmosphere having a temperature of 245° C. or higher and 255° C. or lower. The thermal straightening step (STEP 6) is performed prior to the quenching step (STEP 7).

[0042] As shown in FIG. 2 , the cross-sectional shape of the first side surface 8 of the wire 2 for a compression ring is a circular arc. Furthermore, as described above, the wire 2 has a first rounded chamfer 12a and a second rounded chamfer 12b. Each of these rounded chamfers has a circular arc shape. The number of arcs on the outer circumferential side of the cross-section of the wire 2 is three. The cross-sectional shape of the wire 2 is similar to the cross-sectional shape of a compression ring. A compression ring can be obtained from the wire 2 having this cross-sectional shape by low-level polishing. On the other hand, the cross-sectional shape of the wire 2 having three or more arcs is complex. In the profile drawing (STEP 5) for the wire 2 having this cross-sectional shape, stress concentration is likely to occur in the profiled wire. Thermal straightening (STEP 6) is particularly useful for manufacturing a wire 2 for a compression ring having three or more arcs.

[0043] The material of this compression ring wire 2 is steel. This steel contains: C: 0.51 mass% to 0.85 mass%; Si: 0.15 mass% to 1.60 mass%; Mn: 0.30 mass% to 0.90 mass%; Cr: 0.80 mass% or less; Ni: 0.02 mass% or less; P: 0.08 mass% or less; S: 0.05 mass% or less; and Cu: 0.20 mass% or less. Preferably, the balance is Fe and unavoidable impurities. This steel has a low content of alloying elements. This steel can be obtained at low cost. The role of each element will be explained in detail below.

[0044] [Carbon (C)] C contributes to the hardness and fatigue strength of the compression ring. From these viewpoints, the C content is preferably 0.51% by mass or more, more preferably 0.53% by mass or more, and particularly preferably 0.55% by mass or more. Excess C impairs workability in rolling (STEP 4) and deformed wire drawing (STEP 5). From the viewpoint of cold workability, the C content is preferably 0.85% by mass or less, more preferably 0.75% by mass or less, and particularly preferably 0.65% by mass or less.

[0045] [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% by mass or more, more preferably 0.18% by mass or more, and particularly preferably 0.20% by mass or more. Excessive Si impairs the workability in rolling (STEP 4) and profile drawing (STEP 5). Excessive Si also impairs the toughness of the compression ring. From the viewpoints of cold workability and toughness, the Si content is preferably 1.60% by mass or less, more preferably 1.50% by mass or less, and particularly preferably 1.45% by mass or less.

[0046] [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.

[0047] [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 a 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.

[0048] [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 a compression ring containing 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.

[0049] [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.

[0050] [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.

[0051] [Copper (Cu)] Cu can contribute to workability in rolling (STEP 4) and deformed wire drawing (STEP 5). From this viewpoint, the Cu content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and particularly preferably 0.15% by mass or more. Excess Cu inhibits hot workability. From the viewpoint of hot workability, the Cu content is preferably 0.20% by mass or less, more preferably 0.10% by mass or less, and particularly preferably 0.05% by mass or less. Cu is not an essential element. Therefore, the Cu content may be below the detection limit.

[0052] FIG. 10 shows a wire 38 for a compression 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. The number of arcs on the outer periphery of the cross section of the line 38 is four. The shape of the line 38 is called a "Napier shape." The wire 38 is then coiled or otherwise processed to form a compression ring. The first side surface 44 corresponds to the outer periphery of the compression ring. In an internal combustion engine, this outer periphery rubs against the inner periphery of the cylinder.

[0053] In this compression ring wire 38, the maximum deviation Dif is 3.0 μm or less. Furthermore, in this compression ring wire 38, the filtered center line waviness WCA is 3.0 μm or less, and the sum of the maximum deviation Dif and the filtered center line waviness WCA is 5.5 μm or less. From this wire 38, a compression ring with high circularity can be obtained.

[0054] FIG. 11 shows a wire 50 for a compression ring according to yet 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. The number of arcs on the outer periphery of the cross section of the wire 50 is four. The shape of the wire 50 is called an "undercut shape." The wire 50 is then coiled or otherwise processed to form a compression ring. The first side surface 56 corresponds to the outer periphery of the compression ring. In an internal combustion engine, this outer periphery rubs against the inner periphery of the cylinder.

[0055] In this compression ring wire 50, the maximum deviation Dif is 3.0 μm or less. Furthermore, in this compression ring wire 50, the filtered center line waviness WCA is 3.0 μm or less, and the sum of the maximum deviation Dif and the filtered center line waviness WCA is 5.5 μm or less. From this wire 50, a compression ring with high circularity can be obtained.

[0056] The effects of the wire for a compression ring according to the embodiment will be clarified below, but the scope of the disclosure of this specification should not be interpreted as being limited based on the description of this embodiment.

[0057] Example 1: A steel material having composition A shown in Table 1 below was subjected to the process shown in FIG. 9 to obtain a barrel-type compression ring wire having the shape shown in FIGS. 1 and 2. The equivalent diameter of the intermediate shaped wire after rolling (STEP 4) was 2.03 mm. The equivalent diameter of the intermediate shaped wire after profile drawing (STEP 5) was 1.80 mm. Therefore, the reduction rate was 21.4%. The surface roughness Rz of the intermediate shaped wire after rolling (STEP 4) was 9.5 μm. The surface roughness Rz of the compression ring wire after tempering (STEP 8) was 2.1 μm. This compression ring wire had a maximum deviation Dif of 2.2 μm and a filtered center line waviness WCA of 1.5 μm. This compression ring wire had a thickness of 1.03 mm and a width of 2.70 mm.

[0058] [Examples 2-9 and Comparative Examples 1 and 2] Compression ring wires 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.

[0059] [Warpage] The warpage of the profiled wire after profile drawing (STEP 5), the profiled wire after thermal straightening (STEP 6), and the wire for a compression ring after tempering (STEP 8) was measured using the method shown in Fig. 8. The results are shown in Table 3 below.

[0060] [Twist angle] 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 rings after tempering (STEP 8) were measured using the methods shown in Figures 6 and 7. 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 undergoing thermal straightening (STEP 6).

[0061] [Circularity] The wire for the compression ring was coiled to obtain a ring. The circularity of this ring was evaluated by a light leakage test and ranked according to the following criteria: A: Very good B: Good C: Fairly good D: Poor The results are shown in Table 3 below.

[0062] [Polishing Residue] A ring was obtained by coiling a wire for a compression ring. This ring was subjected to arc ion plating (AIP) to form a coating. This coating was polished to obtain a compression ring. The appearance of this compression ring was visually observed to determine whether there was any polishing residue. The results are shown in Table 3 below.

[0063]

[0064]

[0065]

[0066] As shown in Table 3, the wires for compression rings of each Example are excellent in various performances. From these evaluation results, the superiority of these wires for compression rings is clear.

[0067] Disclosed Items Each of the following items discloses a preferred embodiment.

[0068] [Item 1] A line for a compression ring of an internal combustion engine, wherein the maximum deviation Dif between the contour of a surface corresponding to the outer peripheral surface of the compression ring in a plane perpendicular to the longitudinal direction of the line and a virtual curve approximating this contour is 3.0 μm or less.

[0069] [Item 2] The wire according to item 1, wherein the filtered centerline waviness WCA of the surface corresponding to the outer peripheral surface measured along the length direction is 3.0 μm or less, and the sum of the maximum deviation Dif and the filtered centerline waviness WCA is 5.5 μm or less.

[0070] [Item 3] The line according to item 1 or 2, wherein the outline in a plane perpendicular to the length direction has three or more arcs on its outer periphery.

[0071] [Item 4] The wire according to any one of Items 1 to 3, having a surface roughness Rz of 3.0 μm or less.

[0072] [Item 5] The wire according to any one of items 1 to 4, wherein the twist angle is 3° / m or less.

[0073] [Item 6] The wire according to any one of Items 1 to 5, having a winding warp of 15 mm / m or less.

[0074] [Item 7] The wire according to any one of Items 1 to 6, wherein the material is steel, and 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.

[0075] [Item 8] A method for manufacturing a wire for a compression ring, comprising: (A) a step of rolling an intermediate wire with a roller having a surface roughness Rz of 5.0 μm or more to obtain an intermediate deformed wire; and (B) a step of performing deformed wiredrawing on the intermediate deformed wire using a lubricant with a processing degree of 18.0% or more and 22.0% or less to obtain a deformed wire.

[0076] [Item 9] The manufacturing method according to Item 8, wherein the step (B) provides an irregularly shaped wire having a surface roughness Rz of 3.0 μm or less.

[0077] [Item 10] The manufacturing method according to Item 8 or 9, further comprising, after the step (B), (C) a step of thermally straightening the deformed wire at a temperature of 245°C or higher and 255°C or lower for a time of 2.5 seconds or higher and 3.5 seconds or lower; and (D) a step of quenching and tempering the deformed wire.

[0078] The compression ring wire described above is suitable for piston rings in various internal combustion engines.

[0079] 2: Wire for compression ring 4: Upper surface 6: Lower surface 8: First side surface 10: Second side surface 12: Rounded chamfer 14: Outline of first side surface 16: Outline of upper surface 18: Outline of lower surface 20: Virtual curve 22: Test piece 24: Base 26: Standing portion 30: Test piece 34: Plate 38: Wire for compression ring 40: Upper surface 42: Lower surface 44: First side surface 46: Second side surface 48: Rounded chamfer 50: Wire for compression ring 52: Upper surface 54: Lower surface 56: First side surface 58: Second side surface 60: Rounded chamfer

Claims

1. A line for a compression ring of an internal combustion engine, in which the maximum deviation Dif between the contour of the surface corresponding to the outer peripheral surface of the compression ring in a plane perpendicular to the longitudinal direction of the line and a virtual curve approximating this contour is 3.0 μm or less.

2. The wire according to claim 1, wherein the filtered centerline waviness WCA of the surface corresponding to the outer peripheral surface measured along the length direction is 3.0 μm or less, and the sum of the maximum deviation Dif and the filtered centerline waviness WCA is 5.5 μm or less.

3. A wire as claimed in claim 1 or 2, wherein the profile in a plane perpendicular to the longitudinal direction has three or more arcs on its outer periphery.

4. The wire according to claim 1 or 2, whose surface roughness Rz is 3.0 μm or less.

5. A wire according to claim 1 or 2, the twist angle of which is 3° / m or less.

6. A wire according to claim 1 or 2, having a winding warp of 15 mm / m or less.

7. A wire according to claim 1 or 2, made of steel, which 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.

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

9. The manufacturing method according to claim 7, wherein step (B) produces an irregularly shaped wire having a surface roughness Rz of 3.0 μm or less.

10. A manufacturing method according to claim 7 or 8, further comprising, after step (B), (C) a step of thermally straightening the deformed wire at a temperature of 245°C or higher and 255°C or lower for a time of 2.5 seconds or higher and 3.5 seconds or lower; and (D) a step of quenching and tempering the deformed wire.

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