JP2006183078A - Method for producing metallic ring for variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a metallic ring for variable transmission in which a circumferential length correcting ratio is sufficiently increased without causing necking and breakage. <P>SOLUTION: Both edge parts of thin sheet-state martensitic stainless steel sheet 1 are butted and welded to form a cylindrical metallic drum 2, and the metallic drum 2 is cut at each prescribed width to form the metallic ring 3. After welding, the metallic drum 2 or the metallic ring 3 is held to the temperature range from Ms point to Mf point of the martensitic stainless steel sheet 1 to perform the slow-cooling treatment. Then, after this cooling treatment, the metallic ring 3 is plastically deformed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a stainless steel metal ring for a continuously variable transmission.

  Conventionally, for transmission of power of a continuously variable transmission (CVT) such as an automobile, a CVT belt in which a plurality of metal rings are laminated to form a laminated ring, and the laminated ring is assembled and bound to an element having a predetermined shape. Are known. As the material of the metal ring, maraging steel is often used, but since maraging steel is expensive, it has been proposed to use a cheaper martensitic stainless steel instead (for example, Patent Document 1).

  The metal ring can be manufactured as follows, for example. First, end portions of a thin plate martensitic stainless steel plate are brought into contact with each other and welded to form a cylindrical metal drum. Next, the metal drum is cut into a predetermined width to form a metal ring. Next, after polishing the end of the metal ring to eliminate the edge of the end of the metal ring caused by the cutting, the metal ring is rolled and further tension is applied to the metal ring to correct the circumference. By doing so, a metal ring having a predetermined circumference is obtained. The metal ring having the predetermined circumference can be formed by stacking and fitting a plurality of metal rings having slightly different circumferences to each other.

However, when the metal ring is manufactured by the above-described manufacturing method, if a tension is applied to the metal ring for the peripheral length correction, a constricted portion having a narrower width than the other part is formed in a part of the circumference of the metal ring. If this occurs or is severe, the metal ring breaks at the constricted portion, and there is a disadvantage that the circumference cannot be sufficiently corrected.
JP 2004-18989 A

  The present invention eliminates such inconvenience, and does not cause a necked portion or break even when tension is applied, and can provide a sufficiently high circumference correction factor for a continuously variable transmission metal. It aims at providing the manufacturing method of a ring.

  In order to achieve such an object, the method of manufacturing a metal ring for continuously variable transmission according to the present invention includes a step of butting the ends of thin martensitic stainless steel plates and welding them to form a cylindrical metal drum, Cutting the metal drum into a predetermined width to form a metal ring, and holding the metal drum or the metal ring at a temperature in the range from the Ms point to the Mf point of the martensitic stainless steel plate after the welding. And a step of performing a cooling treatment and a step of plastically deforming the metal ring after the cooling treatment.

  The martensitic stainless steel sheet is given a predetermined hardness in advance by processing it into a thin plate by, for example, light rolling. However, when the end portions of the martensitic stainless steel plate are butted and welded to form a cylindrical metal drum, the hardness imparted by processing into the thin plate shape due to heat during welding is lost, and the welded portion and The hardness of the heat affected zone (HAZ zone) on both sides is significantly lower than the hardness of the base material. When such a metal drum is cut into predetermined widths to form a metal ring, and when the circumference is corrected by applying tension to the metal ring, the welded portion and the HAZ portion are significantly harder than the base metal. Since it is low, it is easier to stretch than other parts, and it is considered that a constricted part occurs in this part.

Therefore, in the manufacturing method of the present invention, first, the metal ring formed by cutting the metal drum formed by the welding for each predetermined width is moved from the Ms point to the Mf point of the martensitic steel plate. Cooling is performed while maintaining the temperature within the range. If it does in this way, the austenite phase of the said weld will become a needle-like martensitic structure, and hardness will rise. As a result, the hardness of the welded portion becomes substantially equal to the hardness of the base material.

  Then, by plastically deforming the metal ring after the cooling treatment, in the HAZ part, work-induced martensite formation of the austenite phase occurs, and the hardness increases. As a result, the hardness of the welded part and the HAZ part are almost equal to the hardness of the base material.

  The cooling treatment may be performed on the metal drum. In this case, the metal drum subjected to the cooling treatment is cut into a predetermined width to form the metal ring, and the obtained metal ring is plastically deformed. Let As a result, the same effect as that obtained when the metal ring is subjected to the cooling treatment and the metal ring after the cooling treatment is plastically deformed can be obtained.

  Therefore, the metal ring obtained by plastic deformation after the cooling treatment does not generate a constriction or break even when tension is applied for the circumference correction, and the circumference correction rate Can be made high enough.

  In the manufacturing method of the present invention, the cooling treatment needs to be performed after the martensitic stainless steel plate is welded and the metal drum is welded, and before the metal ring is plastically deformed. When the metal ring is plastically deformed, work-induced martensite transformation of the austenite phase occurs. Therefore, even if the cooling treatment is performed after that, an increase in hardness is obtained due to transformation of the austenite phase into an acicular martensite structure. I can't.

  The cooling treatment must be performed while maintaining the temperature within the range of the Ms point or less of the martensitic steel sheet. Outside the range, the austenite phase cannot be transformed into a needle-like martensitic structure. Moreover, the lower limit of the temperature of the cooling treatment is the Mf point of the martensitic steel sheet, and no further effect can be obtained even if the temperature is lower than the Mf point. The temperature of the cooling treatment is preferably in a range of 30 ° C. lower than the Ms point (Ms point−30 ° C.) or less, more preferably 45 ° C. lower than the Ms point (Ms point−45 ° C.) or less. It is a range.

  There is no particular limitation on the apparatus and time used for the cooling treatment. For example, in the case of martensitic stainless steel having an Ms point of 30 ° C., examples of the apparatus used for the cooling treatment include a refrigerator and a freezer. According to the refrigerator, a temperature in the range of 30 ° C. lower than the Ms point can be easily obtained, and in the freezer, a temperature in the range of 45 ° C. lower than the Ms point can be easily obtained. In the cooling process, cooling water may be supplied to the welding jig so as to have a temperature within the above range, or the entire room for welding may be cooled to a temperature within the above range.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a process diagram showing the manufacturing method of the present embodiment, FIG. 2 is a graph showing the relationship between the cooling treatment temperature and the hardness of the welded portion, and FIG. 3 is a graph showing the hardness distribution of the metal drum after welding. FIG. 4 is a graph showing the hardness distribution of the metal drum after the cooling treatment. 5 is an explanatory perspective view showing an example of the configuration of an apparatus used for brushing a metal ring, FIG. 6 is a graph showing the relationship between the peripheral length correction factor and the size of the constricted portion, and FIG. 7 is a constricted portion. It is explanatory drawing which shows the calculation method of the magnitude | size.

  In the manufacturing method of the present embodiment, first, as shown in FIG. 1, a thin martensitic stainless steel plate 1 is curled or rolled to form a loop, and then the edges are butt welded to form a cylindrical metal drum. 2 is formed, and the metal drum 2 is cut into predetermined widths to form the metal ring 3.

  Next, the metal ring 3 is accommodated in the cooling device 4, and the martensitic stainless steel sheet 1 is maintained at a temperature in the range from the Ms point to the Mf point to perform a cooling process. By performing the cooling process at a temperature in the above range, the hardness of the welded portion increases as shown in FIG.

  By the way, the side edge of the metal ring 3 is sharpened by the cutting. Therefore, next, as shown in FIG. 1, the side edge of the metal ring 3 is polished by brushing to form a semicircular shape. And the metal ring 3 after the said brush process is rolled, and also the metal ring 3 of predetermined | prescribed circumferential length is obtained by giving tension | tensile_strength to the metal ring 3 after rolling, and performing circumference correction.

  The martensitic stainless steel sheet 1 is given a hardness exceeding 300 Hv by, for example, forming a 0.37 mm-thick original sheet to a thickness of 0.32 mm by a light rolling process such as a skin pass process. However, when the martensitic stainless steel plate 1 is welded to form the metal drum 2, as shown in FIG. 3, in the welded portion and the HAZ portions on both sides thereof, the hardness imparted by the skin pass processing is lost, The hardness of this part is significantly lower than the hardness of the base material. In addition, in FIG. 3, the said weld part points out the range of the welding center distance of about 0 ± 0.5 mm, and the said HAZ part points out the range of the welding center distance of about ± 0.5 mm to about ± 1.5 mm. .

  Therefore, in the manufacturing method of the present embodiment, next, the metal ring 3 obtained by cutting the metal drum 2 by a predetermined width is accommodated in the cooling device 4 and subjected to the cooling process, so that the welding is performed first. The austenite phase of the part is transformed into a needle-like martensite structure, and the hardness of the weld is increased. Here, as the martensitic stainless steel plate 1, when a stainless steel material having a composition in which the Ms point is 30 ° C. and the Mf point is −40 to −60 ° C. is used, the cooling treatment is specifically performed. Is performed by holding the metal ring 3 at a temperature in the range of −60 ° C. (Mf point) to 30 ° C. (Ms point).

  Next, FIG. 4 shows the hardness distribution of the metal drum 2 when the metal drum 2 is cooled in the cooling device 4 at a temperature of −14 ° C. for 1 hour. From FIG. 4, it is clear that the hardness of the welded portion is increased and has a hardness equivalent to that of the base material. In FIG. 4, the welded portion refers to a range with a weld center distance of about 0 ± 0.5 mm, and the HAZ portion refers to a weld center distance of about ± 0.5 mm to about ± 1.5 mm. .

  Next, the metal ring 3 is brushed. The brushing can be performed by, for example, a brush polishing apparatus 11 shown in FIG. The brush polishing apparatus 11 includes a columnar brush head 13 in which a plurality of polishing brushes 12 are provided on a circumference, and a table 14 that holds six metal rings 3. The polishing brush 12 is formed by bundling a plurality of nylon wires containing an abrasive in a cylindrical shape. Further, the table 14 is provided with a ring holding means 15 for holding the metal ring 3 from the inside. The ring holding means 15 holds the six contact members 16 in contact with the metal ring 3 from the inner peripheral surface. To do.

  The brush polishing apparatus 11 rotates the ring holding means 15 by a motor (not shown) to rotate each metal ring 3 in the circumferential direction, and rotates the brush head 13 by a motor (not shown) to rotate each polishing brush 12. Move along a circular orbit. As a result, the polishing brush 12 is brought into contact with the side edge of the metal ring 3, and the side edge is polished by the polishing brush 12 over the entire circumference. In the brush polishing apparatus 11, tension is applied to the metal ring 3 by bringing the contact member 16 of the ring holding means 15 into contact with the metal ring 3 from the inner peripheral surface.

  Then, after the brush processing, the metal ring 3 is rolled. As a result, the metal ring 3 is plastically deformed by the brushing and rolling.

  The plastic deformation occurs in the HAZ portion having a lower hardness than the base material, and the metal ring 3 is stretched in the circumferential direction at the HAZ portion. As a result, the austenite phase of the HAZ part is transformed into work-induced martensite, and the hardness of the HAZ part is increased to be equal to the hardness of the base material.

  As described above, the metal ring 3 has increased hardness between the welded portion and the HAZ portion, and is equal to the hardness of the base material. Therefore, when the circumference is corrected by applying tension to the metal ring 3 after the rolling, the constriction is unlikely to occur, and the circumference can be corrected with a larger circumference correction factor.

  Next, the metal ring 3 (Example) which performed the said cooling process according to the manufacturing method of this embodiment, and the metal ring 3 which performed exactly the same as the manufacturing method of this embodiment except not performing the said cooling process ( In Comparative Example), the relationship between the circumference correction factor and the size of the constricted portion was compared. The results are shown in FIG. As shown in FIG. 7, the size of the constricted portion is the difference B between the width A of the non-constricted portion 5 of the metal ring 3 after the circumferential length correction and the width B of the narrowest portion of the constricted portion 6. -A.

  As shown in FIG. 6, when the cooling process is not performed at all (comparative example), the metal ring 3 is broken at the circumference correction factor of 0.2%, and the constricted portion 6 having a size of -0.24 mm is obtained. There has occurred. On the other hand, when the cooling process is performed (Example), the size of the constricted portion 5 is between −0.04 to −0.12 mm and is a size that causes no practical problem. In addition, a circumference correction factor of 1.0% or more could be obtained.

  Therefore, according to the manufacturing method of the present embodiment, the metal ring 3 does not cause a constriction or breakage so as to cause a practical problem, and the peripheral length correction factor can be sufficiently increased. Is clear.

  In the present embodiment, the cooling process is performed on the metal ring 3 obtained by cutting the metal drum 2 by a predetermined width. However, the cooling process is performed on the metal drum 2. Also good.

Process drawing which shows the manufacturing method of this invention. The graph which shows the relationship between cooling process temperature and the hardness of a welding part. The graph which shows the hardness distribution of the metal drum after welding. The graph which shows the hardness distribution of the metal ring after a cooling process. Explanatory perspective view which shows one structural example of the apparatus used for brush processing of a metal ring. The graph which shows the relationship between a circumference correction factor and the size of a constriction part. Explanatory drawing which shows the calculation method of the magnitude | size of a constriction part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Martensitic stainless steel plate, 2 ... Metal drum, 3 ... Metal ring.

Claims (1)

A process of forming a cylindrical metal drum by abutting and welding the end portions of a thin martensitic stainless steel sheet; and
Cutting the metal drum into a predetermined width to form a metal ring;
A step of cooling the metal drum or the metal ring after the welding by holding the martensitic stainless steel sheet at a temperature ranging from the Ms point to the Mf point of the martensitic stainless steel plate;
And a step of plastically deforming the metal ring after the cooling treatment. A method of manufacturing a metal ring for a continuously variable transmission.

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