JP5391866B2 - Jig, and heat treatment method for cylindrical member - Google Patents

Description

  The present invention relates to a jig for restraining a cylindrical member when the cylindrical member is heat-treated, and a heat treatment method for the cylindrical member using the jig.

  In general, when heat treatment is performed on a cylindrical member made of a steel material, the cylindrical member expands / contracts as the temperature changes, but the entire cylindrical member does not expand / contract uniformly. The roundness of the shaped member, in particular, the roundness of the end (opening) is likely to decrease.

  Conventionally, a technique for suppressing a decrease in roundness of a cylindrical member when heat treatment is performed on the cylindrical member is known, and is described in, for example, Patent Document 1 and Patent Document 2.

  The restraint quenching apparatus described in Patent Document 1 performs heat treatment (quenching) on the constrained cylindrical member in a state where the cylindrical member is constrained by a jig. Specifically, a plurality of convex portions having tip positions that match the shape of the cylindrical member are formed inside the jig, and the cylindrical member is constrained by each convex portion (each convex portion is cylindrical) The material is lightly contacted or opposed with a slight gap) and subjected to quenching. And although a cylindrical member cannot apply a big restraining force at the time of hardening start, when it tries to deform | transform after that, a restraining force (drag) is applied from each convex part, and a deformation | transformation is suppressed. Thus, by suppressing the deformation of the cylindrical member during quenching, it is possible to suppress a decrease in the roundness of the cylindrical member.

  In addition, the quenching deformation correction method described in Patent Document 2 restrains and deforms the cylindrical member with a jig while the structure of the cylindrical member at the time of quenching is in the austenite state. Specifically, the cylindrical member is press-fitted into a jig having a size slightly different from that of the cylindrical member, and is deformed into a shape (perfect circle shape) along the shape of the jig. In this way, it is possible to suppress a decrease in the roundness of the cylindrical member by correcting the shape of the cylindrical member into a perfect circle while the structure of the cylindrical member is in the austenite state.

Here, heat treatment is performed on a relatively thin cylindrical member that easily undergoes plastic deformation when subjected to an external force, and the end of the cylindrical member is subjected to the jig described in Patent Document 1 or Patent Document during heat treatment. Suppose that the jig described in 2 is restrained.
When the heat treatment is started, the cylindrical member expands and contracts as the temperature changes.
However, if the jig for restraining the cylindrical member does not have a size corresponding to the size of the cylindrical member that expands and contracts, there may arise a problem that the roundness of the cylindrical member is reduced.
Specifically, when the outer diameter of the end of the cylindrical member 100 is constrained by the jig described in Patent Document 1 or the jig described in Patent Document 2, when the cylindrical member 100 expands, the cylinder Even when the cylindrical member 100 is uniformly expanded, if the jig does not expand relative to the cylindrical member 100, the cylindrical member 100 can receive a drag force radially inward from the jig. As a result, one place or several places on the outer peripheral portion of the cylindrical member 100 may be plastically deformed inward, leading to a decrease in roundness (see FIG. 10).
Further, in the case where the inner diameter of the end portion of the cylindrical member 110 is constrained by the jig described in Patent Document 2, even when the cylindrical member 110 contracts uniformly when the cylindrical member 110 contracts, If the jig does not contract with respect to the cylindrical member 110, the cylindrical member 110 receives a drag force radially outward from the jig. As a result, the end portion of the cylindrical member 110 is plastically deformed in a trumpet shape toward the outside (in a shape that expands toward the end side), and the diameter deviates from a desired dimension at the end portion (FIG. 11 ( a) and FIG. 11B).

JP-A-6-200320 Japanese Patent Laid-Open No. 8-225851

  This invention provides the jig | tool which can suppress the fall of the roundness of a cylindrical member when heat-processing to a cylindrical member, and the heat processing method of a cylindrical member using the said jig | tool.

The jig according to claim 1 is a jig that restrains an end of the cylindrical member when the cylindrical member is subjected to heat treatment by heating and then cooling the cylindrical member, An outer constraining portion that is formed in an annular shape, has an inner diameter at room temperature that matches the outer diameter of the cylindrical member at room temperature, and has a thermal expansion coefficient that is greater than the thermal expansion coefficient of the cylindrical member made of a martensite phase. Is provided.

The jig according to claim 2 is formed in an annular shape, and the outer diameter when the cooling temperature reaches the martensitic transformation start point of the cylindrical member is the martensitic transformation start point. The cylinder, which coincides with the inner diameter of the cylindrical member, is located in the outer restraint portion, and whose outer peripheral surface is concentric with the inner peripheral surface of the outer restraint portion, and whose thermal expansion coefficient is an austenite phase. An inner restraint portion smaller than the thermal expansion coefficient of the member is provided.

  According to a third aspect of the present invention, there is formed a space that penetrates in the axial direction of the outer restraint portion.

The cylindrical member heat treatment method according to claim 4 is a cylindrical member heat treatment method in which the cylindrical member is heat-treated by heating the cylindrical member and then cooling the cylindrical member, Before heating, it is formed in an annular shape, the inside diameter at room temperature matches the outside diameter of the cylindrical member at room temperature, and the coefficient of thermal expansion is from the coefficient of thermal expansion of the cylindrical member made of a martensite phase. The cylindrical member in a state where the end portion of the cylindrical member is inserted in advance into the outer restraint portion of the jig having a larger outer restraint portion, and the end portion is inserted into the outer restraint portion of the jig, Heat in a single heat treatment furnace and then cool.

The heat treatment method for a cylindrical member according to claim 5 is formed in an annular shape inside an end portion of the cylindrical member before heating the cylindrical member, and the temperature during cooling is the cylindrical shape. The outer diameter of the member when it reaches the martensitic transformation start point coincides with the inner diameter of the cylindrical member at the martensitic transformation start point, and is within the outer restraint portion, and the outer peripheral surface is the outer restraint portion. The inner restraint portion of the jig provided in advance with an inner restraint portion disposed at a position concentric with the inner peripheral surface of the cylindrical member and having a thermal expansion coefficient smaller than that of the cylindrical member made of an austenite phase. Insert, insert the end into the outer restraint portion of the jig, and further heat the cylindrical member in a state where the inner restraint portion is inserted into the end portion in a single heat treatment furnace, Then cool down.

The jig according to claim 6 is a jig for restraining an end portion of the cylindrical member when the cylindrical member is subjected to heat treatment by heating and then cooling the cylindrical member, Formed in an annular shape, the outer diameter when the temperature at the time of cooling reaches the martensitic transformation start point of the cylindrical member matches the inner diameter of the cylindrical member at the martensitic transformation start point, And it has an inner side restraint part whose thermal expansion coefficient is smaller than the thermal expansion coefficient of the said cylindrical member which consists of an austenite phase .

  ADVANTAGE OF THE INVENTION According to this invention, when performing heat processing to a cylindrical member, it is possible to suppress the fall of the roundness of a cylindrical member.

It is a schematic block diagram of the jig | tool which restrains the outer diameter of the edge part of a pipe. It is a flowchart which shows the manufacturing process of a CVT belt. It is a figure which shows the process in which a pipe is manufactured and processed in the case of manufacture of a CVT belt, (a) shows the state by which steel was cut | disconnected, (b) is steel rolled into the cylindrical shape. Shows the state, (c) shows the state where the steel is welded into a pipe, (d) shows the state where the pipe subjected to the first heat treatment is cut into a ring shape, (e) shows the ring shape It is a figure which shows the state which the pipe cut | disconnected by this was deform | transformed by the rolling process. It is a figure which shows the line D1 and the line D3. It is a figure which shows the line D2 and the line D4. It is a partially expanded sectional view of FIG. It is sectional drawing of the jig | tool which restrains the internal diameter of the edge part of a pipe. It is sectional drawing of the jig | tool which restrains the outer diameter and inner diameter of the edge part of a pipe. It is sectional drawing of the jig | tool which restrains the outer diameter and inner diameter of the edge part of a pipe, (a), (b) is a figure which shows the state which the jig | tool has restrained the upper end part of a pipe. It is a figure which shows the edge part of a cylindrical member when restraining a cylindrical member with the conventional jig | tool and performing heat processing. It is a figure which shows the shape of a cylindrical member when restraining a cylindrical member with the conventional jig | tool, and performing heat processing, (a) shows the shape of the outer peripheral surface of a cylindrical member, (b) is FIG. The figure which looked at (a) from the direction of arrow A is shown.

  Below, the jig | tool 10 which is one Embodiment of the jig | tool which concerns on this invention is demonstrated with reference to drawings.

  As shown in FIG. 1, the jig 10 is a pipe 1 that is a portion that tends to expand and contract nonuniformly due to strain or the like generated during phase transformation when heat-treating a thin-walled pipe 1 (cylindrical member) made of a steel material. This restricts the end of the pipe 1 and suppresses the decrease in the roundness of the pipe 1.

The pipe 1 is a cylindrical member that opens at both ends, is a relatively thin member, and easily undergoes plastic deformation when subjected to an external force.
Pipe 1 is maraging steel (Ni: 17-19%, Co: 7-13%, Mo: 3.5-4.5%, Ti: 0.3-1%, Al: 0.05-0. 15%, C: 0.03% or less) and the like, and processed into a CVT belt (an endless metal belt constituting one of the power transmission elements of the belt type CVT).

As shown in FIG. 2, in the pipe 1, the steel strip 1a is cut to a predetermined length (see the steel strip cutting step S10, FIG. 3A), the cut steel 1b is rounded into a cylindrical shape, It is welded in a rolled state (welding step S20, see FIG. 3 (b)) and manufactured by this (see FIG. 3 (c)).
The pipe 1 manufactured in this way is processed to manufacture a CVT belt. More specifically, after the welding step S20 is finished, the manufactured pipe 1 is subjected to a first heat treatment so that the welded portion and the other portion of the pipe 1 have substantially the same hardness (first solution treatment step S30). Thereafter, the pipe 1 subjected to the first heat treatment is cut into a ring shape (see pipe cutting step S40, FIG. 3D), and the pipe 1 cut into the ring shape is subjected to a rolling process (rolling). Step S50, see FIG. 3 (e)), and further a second heat treatment is performed to make the structure uniform (second solution treatment step S60). Thereafter, the perimeter is adjusted (rolled) to a predetermined length (perimeter adjustment step S70), and finally aging / nitriding is performed to improve the strength (aging / nitriding step S80). A CVT belt is manufactured from the pipe 1 through such processes.

The first solution treatment step S30 (the first heat treatment) will be described with reference to FIGS. The first heat treatment is performed in the following order (1) to (7). 4 shows the relationship between the temperature and the outer diameter of the pipe 1 when the pipe 1 is subjected to the first heat treatment, and the line D2 of FIG. 5 shows when the pipe 1 is subjected to the first heat treatment. The relationship between the temperature and inner diameter of the pipe 1 is shown. Further, the outer diameter value corresponding to each temperature of the pipe 1 in the line D1 and the inner diameter value corresponding to each temperature of the pipe 1 in the line D2 are average values, that is, the pipe 1 is uniformly expanded and contracted as the temperature changes. Indicates the value of time.
(1) The pipe 1 is set in a heat treatment furnace (not shown). At this time, the pipe 1 is placed upright so that the axis is vertical. At this time, the pipe 1 is at room temperature and is composed of a martensite phase.
(2) As shown in the line D1 in FIG. 4 and the line D2 in FIG. 5, the heating of the pipe 1 is started from this state, and the temperature of the pipe 1 is increased. The pipe 1 expands as the temperature rises, and the outer diameter and inner diameter increase.
(3) When the pipe 1 is heated to a predetermined temperature (austenite transformation start point / As), the pipe 1 starts to transform from the martensite phase to the austenite phase and hardly expands despite the temperature rise.
(4) When the temperature of the pipe 1 further increases and the temperature rises to the austenite transformation end point (Af), the austenite phase is obtained and the transformation is completed. The austenitic pipe 1 has a higher coefficient of thermal expansion than the martensitic pipe 1.
(5) After the pipe 1 is completely transformed into the austenite phase, the heating of the pipe 1 is finished. Note that T is the temperature of the pipe 1 at the end of heating.
(6) After the heating is finished, the cooling of the pipe 1 is started and the temperature of the pipe 1 is lowered. At this time, the pipe 1 contracts as the temperature decreases, and the outer diameter and inner diameter become smaller.
(7) When the temperature of the pipe 1 is lowered to the martensite transformation start point (Ms), the pipe 1 starts transformation from the austenite phase to the martensite phase, and then expands along with the temperature fall to increase the outer diameter and the inner diameter. The temperature at the martensitic transformation start point is lower than that at the austenite transformation start point. Further, when the temperature of the pipe 1 is at the martensitic transformation start point, the pipe 1 is most contracted and the diameter of the pipe 1 is minimized.
(8) When the temperature of the pipe 1 further decreases and the temperature decreases to the martensitic transformation end point (Mf), the martensitic phase is reached and the transformation is terminated.
(9) After the pipe 1 is transformed into the martensite phase, the pipe 1 cools and contracts, and is cooled to room temperature.

  By applying the first heat treatment shown in the above (1) to (9) to the pipe 1, the welded portion and the other portion of the pipe 1 have the same structure, and the hardness of the pipe 1 is not varied. As a result, when the pipe 1 is stretched in the subsequent rolling step S50, it is possible to prevent the pipe 1 from being broken due to the variation in hardness, and it is possible to uniformly stretch the pipe 1. .

The jig 10 is used when the first heat treatment shown in the above (1) to (9) is performed on the pipe 1 in the first solution treatment step S30.
As shown in FIG. 6, the jig 10 restrains the outer diameter (outer peripheral surface) of the end portion of the pipe 1 during the first heat treatment, and the portion of the jig 10 that restrains the end portion of the pipe 1. The inner diameter is formed according to the size of the outer diameter of the end of the pipe 1.
At the time of the first heat treatment, not only the pipe 1 but also the jig 10 itself that restrains the pipe 1 expands and contracts, but the jig 10 has a larger thermal expansion coefficient than the pipe 1 made of a martensite phase. (For example, austenitic stainless steel).
The jig 10 has a property that does not cause a phase transformation even when the temperature is changed between room temperature and temperature T, so that even when heated and cooled between room temperature and temperature T, distortion is not easily generated, and the jig 10 is uniform. Easy to expand and contract.
The jig 10 includes a ring-shaped flange portion 11, and an annular outer restraint portion 12 that rises from the outer peripheral edge of the flange portion 11 to the flange portion 11 at a substantially right angle (substantially in the axial direction of the flange portion 11). Have.

The inner diameter of the outer restraint portion 12 is set on the basis of the outer diameter of the pipe 1 before heating (at normal temperature) described in (1) above. Specifically, the inner diameter of the outer restraint portion 12 is set to a dimension that matches the outer diameter of the pipe 1 at the normal temperature of (1) above. The inner diameter of the outer restraint portion 12 is the same as the outer diameter of the pipe 1. Moreover, the inner peripheral surface of the front-end | tip part of the outer side restraint part 12 inclines to the outer peripheral side, and is formed in the taper surface which expands slightly as it goes to an edge part. Thereby, the end portion (opening portion) of the pipe 1 can be smoothly inserted into the outer restraint portion 12 (the space surrounded by the inner peripheral surface of the outer restraint portion 12) at the normal temperature of (1). The one end portion is configured not to be plastically deformed by a drag force received from the outer restraint portion 12. As described above, by inserting the end portion of the pipe 1 into the outer restraint portion 12, that is, the space surrounded by the inner circumference surface of the outer restraint portion 12, the outer peripheral surface of the end portion of the pipe 1 and the outer restraint portion 12 are inserted. And the outer diameter of the end portion of the pipe 1 is restrained by the outer restraint portion 12.
When the pipe 1 is inserted into the outer restraint portion 12, the tip of the pipe 1 abuts against the flange portion 11, and the tip of the pipe 1 is prevented from passing through the outer restraint portion 12. It is comprised so that the state by which the outer diameter of this can be restrained with the outer side restraint part 12 can be hold | maintained.

In the first heat treatment, two jigs 10 and 10 are used. Specifically, the two jigs 10 and 10 are inserted into both ends of the pipe 1 at the normal temperature of the above (1), and the outer diameters of the both ends are restrained by the outer restraining parts 12 and 12 of the jigs 10 and 10, respectively. Is done. Further, the pipe 1 constrained by the outer restraining portions 12 and 12 is placed in an upright state (see FIG. 1), and the pipe 1 in this state is heated and cooled as shown in the above (2) to (9). Is given.
At the time of the first heat treatment shown in the above (1) to (9), the jigs 10 and 10 are heated together with the pipe 1 from room temperature to temperature T, and then cooled from temperature T to room temperature. At this time, the relationship between the temperature of the jig 10 and the inner diameter of the outer restraint portion 12 is a line D3 shown in FIG. At the time of the first heat treatment, the jigs 10 and 10 do not undergo phase transformation and expand and contract at a constant coefficient of thermal expansion. Therefore, as shown by the line D3, the inner diameter of the outer restraint portion 12 is as described in (1) above. It corresponds in the time of normal temperature, and the time of normal temperature of said (9).

As shown in FIG. 4, during the first heat treatment, when the pipe 1 expands and contracts uniformly (similarly) as a whole, the outer diameter of the pipe 1 and the outer restraint portion at the room temperature of (1) above. Since the inner diameters of 12 and 12 substantially coincide with each other, there is no gap X1 between the outer peripheral surface of the pipe 1 and the inner peripheral surface of the outer restraining portions 12 and 12, but otherwise (when the temperature is higher than normal temperature) ) Has a gap X1. That is, at the time of the first heat treatment, the jigs 10 and 10 expand to the pipe 1 or more, and the inner diameter of the outer restraining portions 12 and 12 becomes a dimension larger than the outer diameter of the pipe 1. This prevents the pipe 1 that is thin and easily plastically deformed from receiving a drag force from the outer restraining portions 12 and 12. Accordingly, it is possible to suppress a decrease in the roundness of the pipe 1.
The gap X1 is minimized during the cooling shown in the above (6) to (9) at the normal temperature of the above (9).

  Further, during the first heat treatment, when the pipe 1 expands and contracts non-uniformly due to, for example, strain generated during phase transformation, and part of the pipe 1 tends to expand excessively compared to other parts, this excessive expansion occurs. The part to be received receives a drag force from the outer restraining parts 12 and 12 and is restrained from expanding. Thereby, the shape of the pipe 1 is adjusted, and the roundness reduction of the pipe 1 is suppressed. The excessively expanded portion receives drag from the outer restraining portions 12 and 12 particularly at the normal temperature of (9), and is suppressed from expanding.

  Hereinafter, the jig 20 will be described.

The jig 20 is used when the first heat treatment shown in the above (1) to (9) is performed on the pipe 1 in the first solution treatment step S30.
As shown in FIG. 7, the jig 20 is inserted into both ends of the pipe 1 during the first heat treatment, and restrains the inner diameter (inner peripheral surface) of the end of the pipe 1. The outer diameter of the portion that restrains the end of 1 is formed in a size corresponding to the inner diameter of the end of the pipe 1.
During the first heat treatment, not only the pipe 1 but also the jig 20 itself that restrains the pipe 1 expands and contracts, but the jig 20 has a smaller thermal expansion coefficient than the pipe 1 made of an austenitic phase ( For example, it is made of a titanium alloy.
The jig 20 has a property that does not cause a phase transformation even when the temperature changes between room temperature and temperature T, and thus, even when heated and cooled between room temperature and temperature T, distortion hardly occurs, and the jig 20 is uniform. Easy to expand and contract.
The jig 20 includes a ring-shaped flange portion 21 and an annular inner restraint portion 22 that rises from the inner peripheral edge of the flange portion 21 to the flange portion 21 at a substantially right angle (substantially in the axial direction of the flange portion 21). Have.
The outer diameter of the inner restraint portion 22 is set based on the size of the inner diameter of the pipe 1 at the martensitic transformation start point (7). Specifically, the outer diameter of the inner restraint portion 22 is set to a dimension that coincides with the inner diameter of the pipe 1 that has been uniformly expanded and contracted at the martensitic transformation start point (7).
Further, the outer diameter of the inner restraint portion 22 is set to be smaller than the inner diameter of the pipe 1 at the normal temperature of the above (1), and thereby, through the opening at the end of the pipe 1 at the normal temperature of the above (1). The inner restraint portion 22 can be inserted into the pipe 1 (a space surrounded by the inner peripheral surface of the pipe 1). Thus, by inserting the inner restraint portion 22 into the pipe 1, the inner peripheral surface of the end portion of the pipe 1 and the outer peripheral surface of the inner restraint portion 22 face each other. The inner diameter is restrained by the inner restraint portion 22. In addition, the outer peripheral surface of the front-end | tip part of the inner side restraint part 22 inclines to the inner peripheral side, and is formed in the taper surface which diameter-reduces slightly as it goes to an edge part. Thereby, insertion of the inner side restraint part 22 in the pipe 1 can be performed smoothly.
Further, when the inner restraint portion 22 is inserted into the pipe 1, the tip of the pipe 1 comes into contact with the flange portion 21 and the jig 20 is prevented from entering the pipe 1. As a result, the state in which the inner restraint portion 22 is inserted inside the end portion of the pipe 1 (the space surrounded by the inner peripheral surface of the pipe 1 at the end portion of the pipe 1) can be maintained, and the inner diameter of the end portion of the pipe 1 can be reduced. It is comprised so that the state restrained by the inner side restraint part 22 can be hold | maintained.

The pipe 1 is subjected to the first heat treatment in a state in which the jigs 20 and 20 are fitted at both ends thereof, and the pipe 1 has inner diameters of the inner restraining portions 22 and 22 at the normal temperatures of the above (1). Are restrained respectively.
During the first heat treatment shown in the above (1) to (9), the jigs 20 and 20 are heated from room temperature to temperature T together with the pipe 1 and then cooled from temperature T to room temperature. At this time, the relationship between the temperature of the jig 10 and the outer diameter of the outer restraint portion 12 is a line D4 shown in FIG. At the time of the first heat treatment, the jigs 20 and 20 do not undergo phase transformation and expand and contract at a constant coefficient of thermal expansion, so that the outer diameter of the outer restraint portion 12 is (1) When the temperature is normal, and when the temperature is normal (9).

  As shown in FIG. 5, at the time of the first heat treatment, when the pipe 1 expands and contracts uniformly as a whole, at the martensitic transformation start point (7) above, the inner diameter of the pipe 1 and the outer restraint portions 12. 12 does not have a gap X2 between the inner peripheral surface of the pipe 1 and the outer peripheral surfaces of the outer restraining portions 12 and 12, but in other cases (temperature lower than the martensitic transformation start point). , And at a temperature higher than the martensitic transformation start point), there is a gap X2. That is, at the time of the first heat treatment, the outer diameter of the inner restraining portions 22, 22 becomes a dimension equal to or smaller than the inner diameter of the pipe 1. Thereby, it is prevented that the pipe 1 receives a drag from the inner side restraint parts 22 and 22. Accordingly, it is possible to suppress a decrease in the roundness of the pipe 1.

  In addition, when the pipe 1 expands and contracts unevenly during the first heat treatment, and a part of the pipe 1 tends to contract excessively as compared with other parts, the excessively contracted part is restrained inside. The drag is received from the portions 22 and 22 and the contraction is suppressed. Thereby, the shape of the pipe 1 is adjusted, and the roundness reduction of the pipe 1 is suppressed. In addition, especially the part which tends to shrink | contract receives drag from inner side restraint part 22 * 22 at the martensitic transformation start point of said (7), and shrinkage | contraction is suppressed.

  Further, the flange portions 11 and 21 are formed in a ring shape, and the restraining portions 12 and 22 are formed in a cylindrical shape, and the jigs 10 and 20 have shafts of the restraining portions 12 and 22 (the cylinders of the restraining portions 12 and 22). Since the hollows penetrating in the axial direction of the restraining portions 12 and 22 are formed around the cylindrical shaft that forms the shape), the jigs 10 and 20 can be reduced in weight and the jigs 10 and 20 can be reduced in weight. The volume of can be reduced. Thereby, the heat capacity of the jig | tool 10 * 20 can be made small, and the pipe 1 can be heated and cooled rapidly.

  The thermal expansion coefficient of the jig 10 may be the same as the thermal expansion coefficient of the pipe 1 made of the martensite phase. Further, the thermal expansion coefficient of the jig 20 may be the same as the thermal expansion coefficient of the pipe 1 made of the austenite phase.

  Hereinafter, the jig 30 will be described.

The jig 30 includes a function of restraining the outer diameter of the pipe 1 of the jig 10 and a function of restraining the inner diameter of the pipe 1 of the jig 20.
As shown in FIG. 8, the jig 30 includes a jig 10 and a jig 20a.
The jig 20 a is obtained by deforming the shape of the jig 20 into a shape that can be engaged with the jig 10, and the remaining configuration is the same as that of the jig 20. The jig 20 a is formed in a cylindrical shape and has an inner restraint portion 22 a that is functionally identical to the inner restraint portion 22. The relationship between the temperature of the jig 20a during the first heat treatment and the inner diameter of the inner restraint portion 22a is a line D4 shown in FIG.
The inner restraint portion 22a is arranged in the outer restraint portion 12, and the axis of the outer restraint portion 12 and the axis of the inner restraint portion 22a (the axis of the cylinder forming the cylindrical shape of the inner restraint portion 22a) are coaxial. It arrange | positions and the inner peripheral surface of the outer side restraint part 12 and the outer peripheral surface of the inner side restraint part 22a have opposed.
That is, the inner restraint portion 22 a is disposed in the outer restraint portion 12, and is disposed at a position where the outer peripheral surface of the inner restraint portion 22 a is concentric with the inner peripheral surface of the outer restraint portion 12.
By arrange | positioning in this way, the edge part of the pipe 1 is comprised so that insertion is possible between the outer side restraint part 12 and the inner side restraint part 22a. When the end of the pipe 1 is inserted between the outer restraint 12 and the inner restraint 22a, the end of the pipe 1 is sandwiched between the outer restraint 12 and the inner restraint 22a. As a result, the outer peripheral surface of the end portion of the pipe 1 faces the inner peripheral surface of the outer restraint portion 12, and the outer diameter of the end portion of the pipe 1 is restrained by the outer restraint portion 12. At the same time, the inner peripheral surface of the end portion of the pipe 1 is opposed to the outer peripheral surface of the inner restraint portion 22 a, and the inner diameter of the end portion of the pipe 1 is restrained by the outer restraint portion 12. In this way, the outer diameter and inner diameter of the end of the pipe 1 can be constrained simultaneously using the jig 30.

The jig 30 may be configured as shown in FIG. 9A or 9B.
The jig 30 shown in FIGS. 9A and 9B restrains the outer diameter and inner diameter of the upper end portion of the pipe 1.
A jig 10 a including the outer restraint portion 12 shown in FIG. 9A is obtained by appropriately changing the shape of the jig 10. The jig 20b including the inner restraint portion 22a and the jig 20c are obtained by dividing the jig 20 into two parts and further appropriately deforming the shape. The jig 20b and the jig 20c are coupled with a screw or the like. The jig 10a is engaged with the jigs 20b and 20c.
The jig 10b including the outer restraint portion 12 and the jig 10c shown in FIG. 9B are obtained by dividing the jig 10 into two parts and further appropriately deforming the shape. The jig 10b and the jig 10c are coupled with a screw or the like. The jig 20d including the inner restraint portion 22a is obtained by appropriately changing the shape of the jig 20. The jigs 10b and 10c and the jig 20d are engaged.

During the first heat treatment, the outer diameter and the inner diameter of both ends of the pipe 1 are restrained by the jigs 30 and 30 at the normal temperature of (1), and the restrained pipe 1 is transformed into the above (2) to (9). Heated and cooled as shown.
As shown in FIGS. 4 and 5, during the first heat treatment, when the pipe 1 expands and contracts uniformly as a whole, the inner diameter of the outer restraining portions 12, 12 becomes larger than the outer diameter of the pipe 1. Furthermore, the outer diameters of the inner restraining portions 22a and 22a are smaller than the inner diameter of the pipe 1. Thereby, it is prevented that the pipe 1 receives a drag from the restraining portions 12, 12, 22a, and 22a. Accordingly, it is possible to suppress a decrease in the roundness of the pipe 1.
Further, when the pipe 1 expands and contracts unevenly during the first heat treatment, and a part of the pipe 1 tends to expand excessively compared to other parts, this excessively expanded part is particularly (9) At the normal temperature, it receives a drag force from the outer restraint portions 12 and 12 and is restrained from expanding. Further, when a part of the pipe 1 tends to shrink excessively compared to the other parts, the inner restraint portions 22a and 22a are particularly located when the excessively shrinking part is the martensitic transformation start point (7). It is dragged from and the contraction is suppressed. Thereby, the shape of the pipe 1 is adjusted, and the roundness reduction of the pipe 1 is suppressed.

  As described above, the pipe 1 constrained by the jigs 10 and 10, the jigs 20 and 20, or the jigs 30 and 30 is heated and cooled during the first heat treatment. In the present embodiment, the operation of restraining the end of the pipe 1 with the jigs 10 and 10, the jigs 20 and 20, or the jigs 30 and 30 is performed at the normal temperature of the above (1), that is, the above (2). Before starting the heating of the pipe 1 shown, the operation | work which restrains the edge part of the pipe 1 is performed previously. Thereafter, the pipe 1 is heated and cooled as shown in the above (2) to (9) while being restrained by the jigs 10 and 10, the jigs 20 and 20, or the jigs 30 and 30. Further, heating and cooling of the pipe 1 are performed in a single heat treatment furnace, and during the heating and cooling of the pipe 1, the pipe 1 is not taken out of the heat treatment furnace so that the pipe 1 does not come into contact with air. ing. Thereby, the surface oxidation of the pipe 1 is prevented.

  When the pipe 1 was subjected to the first heat treatment without using the jigs 10, 20, 30, the roundness of the pipe 1 after the first heat treatment was 5 to 10% of the diameter of the pipe 1 On the other hand, when the jig 10 or the jig 20 was used as described above, it could be reduced to about 3%. Further, when the jig 30 was used, a roundness of about 1% could be achieved.

1 Pipe 10, 20, 20a, 30 Jig 12 Outer restraint part 22, 22a Inner restraint part

Claims (6)

A jig that restrains an end of the cylindrical member when the cylindrical member is heated and then cooled to heat-treat the cylindrical member.
An outer constraining portion that is formed in an annular shape, has an inner diameter at room temperature that matches the outer diameter of the cylindrical member at room temperature, and has a thermal expansion coefficient that is greater than the thermal expansion coefficient of the cylindrical member made of a martensite phase. A jig comprising Formed in an annular shape,
The outer diameter when the temperature at the time of cooling reaches the martensitic transformation start point of the cylindrical member matches the inner diameter of the cylindrical member at the martensitic transformation start point,
Inside the outer restraint portion, the outer peripheral surface is disposed at a position that is concentric with the inner peripheral surface of the outer restraint portion, and the thermal expansion coefficient is smaller than the thermal expansion coefficient of the cylindrical member made of the austenite phase. The jig according to claim 1, further comprising a restraining portion.   The jig according to claim 1 or 2, wherein a space penetrating in the axial direction of the outer restraint portion is formed. A cylindrical member heat treatment method in which a cylindrical member is heated and then cooled to heat treat the cylindrical member,
Before heating the cylindrical member,
An outer constraining portion that is formed in an annular shape, has an inner diameter at room temperature that matches the outer diameter of the cylindrical member at room temperature, and has a thermal expansion coefficient that is greater than the thermal expansion coefficient of the cylindrical member made of a martensite phase. In the outer restraint portion of the jig comprising
Insert the end of the cylindrical member in advance,
A method for heat-treating a cylindrical member, wherein the cylindrical member with an end inserted into the outer restraint portion of the jig is heated in a single heat-treatment furnace and then cooled. Before heating the cylindrical member,
Inside the end of the cylindrical member,
Formed in an annular shape, the outer diameter when the temperature at the time of cooling reaches the martensitic transformation start point of the cylindrical member matches the inner diameter of the cylindrical member at the martensitic transformation start point, Inside the outer restraint portion, the outer peripheral surface is disposed at a position that is concentric with the inner peripheral surface of the outer restraint portion, and the thermal expansion coefficient is smaller than the thermal expansion coefficient of the cylindrical member made of the austenite phase. The inner restraint portion of the jig including the restraint portion,
Insert it in advance
The cylindrical member in a state where an end portion is inserted into the outer restraint portion of the jig and the inner restraint portion is further inserted into the end portion is heated in a single heat treatment furnace and then cooled. Item 5. A method for heat-treating a cylindrical member according to Item 4. A jig that restrains an end of the cylindrical member when the cylindrical member is heated and then cooled to heat-treat the cylindrical member.
Formed in an annular shape, the outer diameter when the temperature at the time of cooling reaches the martensitic transformation start point of the cylindrical member matches the inner diameter of the cylindrical member at the martensitic transformation start point, And a jig | tool provided with an inner side restraint part whose thermal expansion coefficient is smaller than the thermal expansion coefficient of the said cylindrical member which consists of an austenite phase .

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