JP4267151B2 - Method for producing endless metal belt - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an endless metal belt used in a continuously variable transmission or the like.
[0002]
[Prior art]
Conventionally, endless metal belts used for continuously variable transmissions and the like are manufactured by the following method. First, end portions of maraging steel thin plates, which are super-extreme steels, are welded together to form a cylindrical drum, and the hardness partially increased by the heat during the welding is homogenized with respect to the drum. Therefore, the first solution treatment is performed. Next, the solution-treated drum is cut into a predetermined width to form a ring, and the ring is rolled. Next, in order to recrystallize the rolled structure on the rolled ring and restore the shape of the metal structure deformed by rolling, a second solution treatment is performed. And after correcting the ring after the solution to a predetermined circumferential length, and performing aging and nitriding treatment to improve the hardness, a plurality of rings having different circumferential lengths are laminated one by one to endless metal belt Form.
[0003]
In the conventional manufacturing method, the circumference correction of the ring after the second solution is made, as shown in FIG. 5, the ring 4 is stretched between the driving roller 11 and the driven roller 12 to give tension, and the driving roller 11 While the ring 4 is driven to rotate, the correction roller 13 provided between the driving roller 11 and the driven roller 12 is moved in the direction of the arrow. As a result, the ring 4 is loaded in a direction orthogonal to the traveling direction of the ring 4 by the correction roller 13 and is extended to a predetermined length. In order to appropriately perform the circumference correction, it is desirable that the ring 4 has an annular shape as close to a perfect circle as possible.
[0004]
However, in the conventional manufacturing method, heat treatment distortion occurs depending on the conditions of the second solution treatment, and the shape of the ring 4 after the solution treatment is, for example, a cross shape in plan view as shown in FIG. It may be a complex curve with irregularities or an extremely long and narrow elliptical shape as shown in FIG.
[0005]
When the ring 4 after the second solution forming has a shape as shown in FIG. 7A or 7B, the ring 4 is spanned between the driving roller 21 and the driven roller 22 to correct the circumference. When this occurs, a portion where the ring 4 does not sufficiently contact the rollers 21 and 22 will come out. In such a state, when the circumferential length correction is performed as described above, the thickness of the ring 4 becomes uneven between the portion that contacts the rollers 21 and 22 and the portion that does not contact, or the both ends of the ring 4 There is an inconvenience that the circumference does not match.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide an endless metal belt manufacturing method capable of properly correcting the circumferential length by eliminating such inconvenience and suppressing heat treatment distortion in solution treatment after rolling a ring. To do.
[0007]
[Means for Solving the Problems]
In order to eliminate the inconvenience, the present inventors have studied various methods for producing the endless metal belt and have obtained the following knowledge.
[0008]
First, in the conventional manufacturing method, the second solution after the rolling is performed by heating the ring in a heating furnace in a nitrogen atmosphere containing some hydrogen. At this time, when the ring is heated at a temperature lower than the recrystallization temperature of the maraging steel, distortion due to the heat treatment occurs, and the shape of the ring after solution forming becomes a complex curve with irregularities, for example, FIG. ) It turned out to be a cross-sectional shape in plan view as shown.
[0009]
Next, when the ring is heated at a temperature equal to or higher than the recrystallization temperature of the maraging steel in a state where it is suspended from the hook, the shape of the ring after solution forming is a cross-sectional shape in plan view as shown in FIG. Although it is possible to avoid this, it has been found that an extremely elongated elliptical shape as shown in FIG. The reason for the extremely elongated elliptical shape as described above is considered to be that when the ring is heated while being suspended from a hook, creep deformation due to its own weight occurs in the ring depending on the solution conditions.
[0010]
The present invention has been made on the basis of the above knowledge, and in order to achieve the above object, a step of welding end portions of thin sheets of maraging steel to form a cylindrical drum, and a predetermined width of the drum. Forming a ring by cutting into a ring, a step of rolling the ring, a step of forming a solution on the rolled ring, and a circumference correction by spanning the solution formed ring between a driving roller and a driven roller in the manufacturing method of an endless metal belt and a step of performing, the solution is the circumferential direction of the ring on the floor of the heating furnace is disposed the ring so as to be parallel, maraging in the oven By heating at a temperature in the range of not less than the recrystallization temperature of steel and not more than 850 ° C., the ring segment after solution forming always has a line segment connecting any two points on the circumference inside the ring and The curvature of the drive roller and Characterized by an annular shape which is less curvature of the dynamic rollers.
[0011]
The solution treatment for the ring after the rolling is performed by heating at a temperature in the range of not less than the recrystallization temperature of the maraging steel and not more than 850 ° C. to recrystallize the rolled structure deformed by the rolling, thereby changing the shape of the metal structure. It can be restored and heat treatment distortion can be suppressed. When the solution temperature is lower than the recrystallization temperature of maraging steel, solution itself is difficult and the ring is deformed by heat treatment strain. Further, when the temperature of the solution treatment exceeds 850 ° C., the crystal of the recrystallized metal structure is coarsened, so that the tensile strength of the ring is lowered.
[0012]
According to the manufacturing method of the present invention, the ring is solution-treated in the temperature range so that the ring after solution forming has an annular shape, so that the ring is made like the conventional manufacturing method. When the circumference correction is performed across the drive roller or the driven roller, the ring can be continuously brought into contact with each roller. When the ring is in continuous contact with each roller, there is no intermittent contact portion, and the circumference correction is performed with uneven thickness of the ring or circumference mismatch at both ends of the ring. It can be performed appropriately without becoming.
[0013]
Also, before Symbol ring, by arranging as described above, it is possible to avoid creep deformation due to its own weight, can be easily annular shape the shape of a ring after the solution.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a process diagram schematically showing each process of the manufacturing method of the present embodiment, FIG. 2 is a graph showing the relationship between the solution temperature and the tensile strength of the ring, and FIG. 3 is a solution process of the present embodiment. FIG. 4 is an explanatory view showing the relationship between the continuous solution furnace used and the temperature of each chamber, FIG. 4 is an explanatory sectional view showing the arrangement of the rings in the heating furnace, and FIG. 5 shows a method for correcting the circumference of the ring. FIG. 6 is an explanatory diagram showing the shape of the ring after solution treatment by the manufacturing method of the present embodiment.
[0015]
In the manufacturing method of this embodiment, first, as shown in FIG. 1, the maraging steel thin plate 1 is bent to form a loop, and then the ends are welded to form a cylindrical drum 2. At this time, since the maraging steel exhibits age hardening by the heat of welding, high hardness portions appear on both sides of the welded portion of the drum 2.
[0016]
Therefore, next, the drum 2 is accommodated in the vacuum furnace 3 and held at a temperature of 820 to 830 ° C. for 20 to 60 minutes to perform a first solution treatment to remove welding distortion. When the first solution treatment is completed, the drum 2 is unloaded from the vacuum furnace 3 and cut into a predetermined width to form the ring 4.
[0017]
The ring 4 formed as described above is then rolled at a rolling reduction of 40 to 50%. And the rolled ring 4 is accommodated in the heating furnace 5, and 2nd solution treatment is performed. In the second solution treatment, the ring 4 is heated to a temperature not lower than the recrystallization temperature of maraging steel and not higher than 850 ° C. in a reducing atmosphere composed of nitrogen containing 1 to 10%, for example, 4% hydrogen. The process is performed so that the ring 4 after solution forming has an annular shape.
[0018]
The recrystallization temperature varies depending on the composition of the maraging steel, but is about 760 ° C., for example, in the case of 18Ni-maraging steel. As shown in FIG. 2, the tensile strength after solutionization of the ring 4 made of 18Ni-maraging steel becomes constant when heated at a temperature in the range of 760 to 850 ° C., and proper recrystallization occurs in this temperature range. It is clear that this is done. On the other hand, when heated at a temperature of less than 760 ° C., the tensile strength is higher than when heated at a temperature in the range of 760 to 850 ° C., and it is clear that recrystallization is difficult to perform. Further, when heated at a temperature exceeding 850 ° C., the tensile strength is lower than when heated at a temperature in the range of 760 to 850 ° C., and recrystallization proceeds excessively to generate coarse crystals. it is obvious.
[0019]
As shown in FIG. 3, the heating furnace 5 used in this embodiment includes a vacuum carry-in chamber 21, a first heating chamber 22, a second heating chamber 23, a third heating chamber 24, a gas cooling chamber 25, and a vacuum carry-out chamber 26. It consists of 6 consecutive rooms. After being carried into the vacuum carry-in chamber 21, the ring 4 moves toward the vacuum carry-out chamber 26 over 40 minutes each passing through each chamber.
[0020]
The vacuum carrying-in chamber 21 is a section into which the ring 4 is carried in, and while the carried-in ring 4 moves to the first heating chamber 22, the atmosphere is sucked into a vacuum and then nitrogen is supplied, The inside of the vacuum carry-in chamber 21 is replaced with a nitrogen atmosphere.
[0021]
Each heating chamber 22, 23, 24 is a section for heating the ring 4 in the reducing atmosphere. First, the first heating chamber 22 is heated, for example, from room temperature to about 700 ° C. while the ring 4 loaded from the vacuum loading chamber 21 moves to the second heating chamber 23. Next, the second heating chamber 23 is heated to a temperature at which the ring 4 is solutionized, for example, 820 ° C., while the ring 4 carried from the first heating chamber 22 moves to the third heating chamber 24, The compartment is maintained at the temperature. The third heating chamber 24 is a section that holds the ring 4 at a temperature at which the solution is formed until the ring 4 carried in from the second heating chamber 23 moves to the gas cooling chamber 25.
[0022]
The gas cooling chamber 25 is a section for cooling the solution-formed ring 4 under a nitrogen atmosphere, and the ring 4 is moved until the ring 4 carried in from the third heating chamber 24 moves to the vacuum carry-out chamber 26. For example, it is cooled to a temperature of 150 ° C. or lower. The vacuum carry-out chamber 26 is a section for carrying out the solutionized ring 4 to the outside of the heating furnace 5, and sucks the nitrogen atmosphere until the ring 4 carried in from the gas cooling chamber 25 is carried out to the outside. Then, after evacuating, the atmosphere is supplied to replace the inside of the vacuum carry-out chamber 26 with the atmosphere.
[0023]
As a result, while the ring 4 passes through the respective heating chambers 22, 23, 24, the ring 4 is kept in solution at a temperature at which the solution is formed, for example, 820 ° C. for 30 minutes.
[0024]
In addition, the ring 4 is laid flat on a mesh wire mesh 28 laid on the base tray 27 as shown in FIG. 4 inside the heating furnace 5, and the circumference C of the ring 4 is placed on the floor 29 of the heating furnace 5. It arrange | positions so that a direction may become parallel. Therefore, the ring 4 does not cause creep deformation due to its own weight, and can be easily formed into a solution so as to have the annular shape.
[0025]
After the ring 4 formed into a solution as described above is taken out from the heating furnace 5, the ring 4 is passed over the drive roller 11 and the driven roller 12 as shown in FIG. While rotating, the circumference correction is performed by moving the correction roller 13 provided between the drive roller 11 and the driven roller 12 in the direction of the arrow. At this time, the ring 4 is formed into an annular shape by the solution treatment, and can continuously contact the rollers 11 and 12 without forming a portion that intermittently contacts. In this state, the ring 4 moves the correction roller 13 in the direction indicated by the arrow and applies a load in a direction perpendicular to the traveling direction of the ring 4 so that the plate thickness is uniform and the circumferences of both ends are equal. Thus, the circumference correction is appropriately performed.
[0026]
As shown in FIG. 6 (a), the ring shape is such that a line segment AB connecting any two points A and B on the circumference is always inside the ring 4, and as shown in FIG. 6 (b). It is desirable that the curvature of 4 is not more than the curvature of the rollers 11 and 12.
[0027]
In the present embodiment, the first solution heat treatment for the drum after welding is performed using the vacuum furnace 3, but the first solution heat treatment is the same condition as the second solution heat treatment for the ring after rolling. Thus, the heating furnace 5 may be used.
[Brief description of the drawings]
FIG. 1 is a schematic view showing each step of a production method of the present invention.
FIG. 2 is a graph showing the relationship between the solution temperature and the tensile strength of the ring.
FIG. 3 is an explanatory diagram showing a relationship between a configuration example of a continuous solution furnace used in the manufacturing method of the present invention and the temperature of each chamber.
FIG. 4 is an explanatory cross-sectional view showing the arrangement of rings in a heating furnace.
FIG. 5 is an explanatory diagram showing a ring circumference correction method.
FIG. 6 is an explanatory view showing the shape of the ring after solution treatment by the production method of the present invention.
FIG. 7 is an explanatory view showing the shape of a ring after solution treatment by a conventional manufacturing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Thin plate, 2 ... Drum, 4 ... Ring, 5 ... Heating furnace, 29 ... Floor surface.

Claims (1)

A step of welding ends of thin sheets of maraging steel to form a cylindrical drum, a step of cutting the drum into a predetermined width to form a ring, and rolling the ring; In a method for producing an endless metal belt, comprising: a step of performing solution treatment; and a step of performing circumference correction by spanning the ring subjected to solution solution to a drive roller and a driven roller .
The solution is circumferential direction of the ring on the floor of the heating furnace is disposed the ring so as to be parallel, heated at a temperature of recrystallization temperature or higher 850 ° C. or less in the range of maraging steel in the oven Thus, the ring after the solution is formed is a ring in which a line segment connecting any two points on the circumference is always inside the ring and the curvature of the ring is equal to or less than the curvature of the driving roller and the driven roller. A method for producing an endless metal belt, characterized by having a shape .

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