JPH09164446A - Manufacture of stepped metallic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepped metallic material excellent in the surface property and having an appropriate large diameter part by forming an annular projection in a hot condition while at least one of three form rolling rolls is of flat roll type, and the inter-axis distance of the form rolling rolls is changed. SOLUTION: A material 3A to be worked is carried between rolls in which the mutual roll nip is set to be larger than the outer diameter of the material 3A to be worked, and a part of the material to be worked is located at an annularly projected part of form rolling rolls 1A, 1B. The infer-axis distance is successively brought close to each other while each roll is rolled, and the annular projection of the form rolling rolls 1A, 1B is pressed for form rolling into the material 3A to be worked. The material 3A to be worked is brought into contact with the form rolling rollers 1A, 1B, and a flat roll 2, and simultaneously rolled at three parts in the circumferential direction to transfer the rugged shape. Generation of seizure flaws is prevented, and the wear of the rolls is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a stepped metal material such as a stepped steel bar having a different outer diameter in the axial direction position by processing a rod-shaped metal material having the same outer diameter in the axial length direction. Regarding the method.

[0002]

2. Description of the Related Art A stepped metal material such as a stepped steel bar having a different outer diameter at each position in the axial direction (hereinafter simply referred to as a stepped bar) is used in various industrial fields such as heavy electric machines, tractors, It is used as a material for axles of automobiles and spinning machines, and such stepped rods are conventionally manufactured mainly by the following method.

<< First Method ... Cutting Method >> The first method is a cutting method. In this method, a material having the outer diameter of the largest diameter portion is used to obtain a required stepped rod-shaped product. It is a method of preparing and removing the constricted part of the step using a cutting machine such as a lathe to remove it to obtain a product shape, which is usually the most used method.

The advantage of this method is that the depth of cut can be set freely during external cutting, and even if the shape differs from product to product, it can be flexibly handled. Therefore, this method is suitable for manufacturing a large number of small lots.

However, in this method, if the step of the stepped portion is large, a large amount of material is removed by cutting, so that the material yield is extremely deteriorated. Further, there is a fatal drawback that the time required for cutting becomes long and the working time and cost increase.

<< Second Method ... Forming Method by Inclined Roll Rolling Mill >> The second method is, for example, Japanese Patent Laid-Open No. 63-12354.
As disclosed in Japanese Patent No. 5 publication, a method of squeezing the outer diameter of a raw material with an inclined roll rolling machine in which 3 to 4 cone type rolls are arranged around a pass line, and a distance between the cone type roll and the pass line is separated. Is a method of obtaining a required stepped rod by controlling and changing the value during rolling.

FIGS. 4 to 6 are schematic views showing a forming method by an inclined roll rolling machine, FIG. 4 is a front view, FIG. 5 is a side view taken along line IV-IV of FIG. 4, and FIG. III of III-III
It is a partially-omitted plan view taken along the arrow. As is clear from the figure, in this method, the cone-shaped rolls 4, 5 and 6 have a crossing angle γ (see FIG. 5) and an inclination angle β (see FIG. 6) around the workpiece 7 having a circular cross section. It is arranged radially and the like. Further, each of the cone-shaped rolls 4, 5 and 6 is connected to a rotary drive mechanism and a roll gap adjusting hydraulic pressure or a screw reduction mechanism, which are not shown, and is rotationally driven in a direction indicated by a thin line arrow and a thick line during rolling. The roll gap is controlled by displacing in the direction indicated by the arrow. As a result, the stretched line rolling of the material 7 to be processed shown in FIG. 5 is performed to form a portion 7a having a different outer diameter from the material 7 to be processed. At this time, the work material 7 is made of Al or C, which will be described later.
When it is a soft material such as u, it is processed at room temperature. However, in the case of a material that is more difficult to work than Al or Cu, for example, ordinary steel or special steel, 1000 to 1250
It is heated to about ℃ and then processed.

The advantage of this method is that it is possible to form a portion 7a having different outer diameters and lengths and having various outer diameters with only one kind of roll shape, and it is possible to obtain a desired product shape relatively flexibly. It is possible.

However, in this method, the diameter of the material can be reduced to various predetermined outer diameters by pushing the material into the material to be processed 7 while rotating the cone type roll by the hydraulic pressure reduction mechanism. If the taper angle of the stepped portion becomes large, there is a drawback that rolling cannot be continued. That is, FIG. 7 is a diagram showing the cone-shaped roll in a modified form for the sake of simplicity. However, as shown in FIG. 7, the cone-shaped roll is placed at an arbitrary position in the axial direction of the material 7 to be processed. When forming the small-diameter portion indicated by the broken line, if the taper angle of the stepped portion, in other words, the biting angle θ of the rolls 5 and 6 with respect to the material 7 to be processed is too large, slippage occurs at the portion and the leftward direction in the drawing It becomes impossible to move the rolls 5 and 6 in the direction indicated by the thick arrow, in other words, the material 7 to be processed cannot be sent out in the arrow direction (see FIGS. 5 and 6) and the step having the required taper angle is obtained. The disadvantage is that it is not possible to manufacture a bar with a bar. Incidentally, according to the experimental results of the present inventors, the upper limit of the biting angle θ that can be rolled is about 30 °, and it is not possible to manufacture a stepped rod having a stepped portion with a taper angle larger than this. could not.

<Third Method: Forming Method Using Rolling Roll with Protrusions> The third method is to form a thin annular fin on the outer peripheral surface of a rod or tubular body using three rolling rolls with protrusions. Is the way to do it.

8 and 9 are schematic views showing a method of forming an annular fin with a rolling roll having protrusions. FIG. 8 is a front view and FIG. 9 is a development view taken along the line V-V in FIG. . As is clear from FIGS. 8 and 9, in this method, a plurality of annular projections 10b are formed by connecting thin disk roll members 10a having the same outer diameter and a thin outer edge portion in the axial direction. Formed three rolls 10, 11, 1
The two are radially equally arranged so that their roll axes are parallel to each other. Then, the work material 13 is placed between these three rolling rolls, and the three rolling rolls 10, 11 and 12 are rotationally driven in the directions indicated by the thin line arrows, while the direction indicated by the thick line arrows, that is, the work to be processed. By gradually approaching toward the axis of the material 13, the material is bulged into the gap 10c between the disk roll members 10a, and thereby a plurality of thin annular fins 13a are simultaneously bulged on the outer peripheral surface of the material 13 to be processed. Is the way.

According to this method, for example, a thin fin having a relatively high height can be cold formed into a soft material such as Al or Cu, and a fin with a so-called fin used in a heat exchanger or the like can be formed. It is possible to manufacture tubes and the like. That is, the wall thickness is as thin as 1 to 3 mm at most like the thin annular fin 13a, and the interval between the thin annular fins 13a is almost the same as the wall thickness of the annular fin 13a, or at most 1.5 to 2 times. In the case of a certain degree, the material removed by pushing the disc roll member 10a flows toward the gap 10c between the disc roll members 10a and rises relatively uniformly, so that the height having a smooth tip shape is obtained. It is possible to form a thin annular fin 13a having a relatively high height.

However, according to this method, not only the stepped rod which is the object of the present invention to be manufactured, that is, the length of the large diameter portion in the axial length direction, but also the length of the small diameter portion between the large diameter portions in the axial length direction is as described above. In the case of molding a much larger one such as three times or more as compared with the thin annular fin 13a, there is a drawback that a predetermined shape cannot be obtained.

FIG. 10 is a schematic diagram for explaining the above, but as shown in FIG. 10, in order to mold a product in which the large-diameter portion and the small-diameter portion have large axial lengths, it is natural. However, by using the rolling rolls 110, 120 (and 130) in which the thick disk roll members 100a are connected to each other at a wide interval, the large diameter portion 130a corresponding to the annular fin 13a is provided between the thick disk roll members 100a. Will be bulged.

However, in this case, as shown in the drawing, the material removed by the thick disk roll member 100a is concentrated on the end of the step portion, and the partial raised portion A is formed.
However, there is a drawback that the large diameter portion 130a having a uniform outer diameter in the axial direction cannot be formed.

Incidentally, according to the experimental results of the present inventors,
The thickness of the tip portion of the large diameter portion 130a is the material to be processed 130.
When the outer diameter exceeds 15% of the outer diameter, the swelling portion A was observed. Further, once the bulge portion A is formed, even if it is attempted to finish by pressing to make it smooth in the next step, the pointed portion of the bulge portion A folds into either side and becomes a rash defect, resulting in a surface defect. I also confirmed that.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the object is to manufacture a stepped rod-shaped product having a wide axial length dimension by using the third method described above. It is an object of the present invention to provide a highly efficient method for producing a stepped metal material, which can surely prevent formation of the raised portion A and can produce a stepped rod in one step.

[0018]

Means for Solving the Problems The present inventors have found the following as a result of various experimental researches for achieving the above-mentioned objects. That is, when the material to be processed having a circular cross section is partially reduced in diameter by using three rolling rolls in which wide annular protrusions are connected at wide intervals, a large diameter portion is formed between the reduced diameter portions. It has been found that, when at least one of the three rolling rolls is a flat roll having no annular projection, the raised portion A (see FIG. 10 described above) can be reliably prevented from occurring.

The gist of the present invention based on the above findings lies in the following method for producing a stepped metal material.

3 in which a plurality of annular projections are formed in the axial direction
The three rolling rolls are radially arranged around the metal material to be processed so that the axis thereof is parallel to the axial center line of the metal material to be processed having a circular cross section, and formed by the three rolling rolls. A method of hot forming an annular projection on the outer peripheral surface of a metal material to be processed while changing the distance between the axes of the rolling rolls so that the diameter of the tangent circle is gradually reduced. A method for producing a stepped metal material, wherein at least one of the rolls is a flat roll.

In the above-mentioned method of the present invention, it is desirable that the number of flat rolls is two, and in this case, the raised portions generated on both sides of the annular projection of the rolling roll can be made smoother. Further, it is desirable to use a rolling roll having an annular projection as a driving rotation roll and a flat roll as a non-driving free rotation roll. In this case, seizure flaws and roll wear caused by the difference in roll peripheral speed are suppressed. Besides, it is possible to reduce the device cost. Further, it is desirable to displace only the axial center position of the rolling roll having the annular projection. In this case, in order to secure the processing reference position when performing the rolling continuously in the axial direction of the long material. It is not necessary to use a special guide, and the equipment cost can be reduced.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention described above, a plurality of rolling rolls with annular projections formed so as to obtain a required stepped shape and a flat outer peripheral surface having no annular projections. By using the rolls in combination, the annular protrusions of the rolling roll with annular protrusions are pressed into the material to be processed to transfer the shape of the annular protrusions to the outer peripheral surface thereof, while forming the convex portions between the annular protrusions. At this time, since the raised portions A (see FIG. 10) generated at both ends of the convex portion due to the pressing of the annular protrusion are pressed by the flat rolls and straightening is performed almost at the same time as the formation of the concave portion, local correction is performed. It is possible to form a smooth convex portion having no raised portion A. As a result, it is possible to manufacture a stepped rod-shaped product having a target uneven shape.

Hereinafter, the method of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a front view showing an example of an embodiment of the present invention, FIG. 2 is a front view showing another example, and FIG. 3 is a view taken along the line I--I in FIG. 1 and the line II--II in FIG. It is a side view.

FIG. 1 shows the case where the rolling rolls 1A and 1B having two annular projections and one flat roll 2 having no annular projections are used, and FIG. 2 shows one annular projection. The case of using the rolling roll 1 having it and the case of using the two flat rolls 2A and 2B having no annular projection are respectively shown. In either case, the rolling rolls 1A, 1B
And 1, and flat rolls 2 and 2A, 2B
Are radially arranged so that their roll axes are parallel to each other, and are connected to a drive source (not shown) so that they can be rotationally driven in a direction indicated by a thin arrow in the figure. Further, these rolls are connected to a roll gap adjusting hydraulic pressure or a screw pressing mechanism (not shown) so as to be movable in a direction indicated by a thick arrow in the drawing so that the mutual roll intervals can be adjusted.

The rolling rolls 1A, 1B and 1 are shown in FIG.
, The required product recess shape, that is, the outer diameter is d
i, the length in the axial direction is t, and a plurality of small-diameter portions 3a having a step portion taper angle α are formed at a predetermined pitch p, the tip width is T (= t) and the taper angle is α. , A plurality of annular projections 1a having an outer diameter D1O are connected at a predetermined pitch P, and the roll outer diameter D1i is such that a desired product convex shape, that is, a large diameter portion 3b having an outer diameter do can be obtained. It is set in consideration of the pushing amount.

Further, flat rolls 2, 2A and 2B
Has an outer diameter D2 and a length L exceeding np + t + (do-di) / tan α, where n is the number of annular projections 1a.

The production of the stepped rod by the rolling mill configured as described above is performed as follows. First, a solid work material 3A (3B) with a circular cross section, which is a rolling material
Is heated by a heating furnace (not shown) to a predetermined temperature, for example, about 1100 to 1200 ° C. for medium carbon steel and about 400 to 450 ° C. for aluminum alloy. Needless to say, when the rolled material is a soft metal such as pure aluminum or pure copper, it can be processed without heating.

Next, the roll intervals are set to the material 3 to be processed.
The material 3A (3B) to be processed should be conveyed and fed in the axial direction of the roll between the rolls set larger than the outer diameter of A (3B) by using an appropriate conveying means such as a roller conveyor to perform processing. The material portion is located on the annular projection 1a portion of the rolling rolls 1A, 1B (1).

Thereafter, while rotating the rolls, the distances between the axes of the rolls are gradually reduced, and the annular projections 1a of the rolls 1A, 1B (1) are pushed into the material 3A (3B) to be processed. Start. As a result, the material to be processed 3A
(3B) comes into contact with the rolling rolls 1A, 1B (1) and the flat roll 2 (2A, 2B), and at the same time, the rolling rolls 1A, 1B The uneven shape of 1) is transferred.

At this time, a recess of the product is formed in a portion of the rolling rolls 1A, 1B (1) which is pressed down by the annular projection 1a, and the material flows near both sides of the recess to locally raise the raised portion A (the above-mentioned portion). (See FIG. 10) occurs. However, in the present invention, as described above, the flat roll 2 having a smooth outer peripheral surface
(2A, 2B) are arranged, and the work material 3A (3B) is 1
The raised portion A formed during rotation (see FIG.
(Refer to FIG. 3) is sequentially smoothed and smoothed, so that the product portion formed between the annular protrusions 1a is surely formed into a flat surface.

In the above, the flat roll 2
The pushing amount of (2A, 2B) is the same as the pushing amount of the rolling rolls 1A, 1B (1) having the annular protrusion 1a.

In the above, the difference between the method shown in FIG. 1 and the method shown in FIG. 2 is that in FIG. 1 there is one flat roll, whereas in FIG. 2 there are two flat rolls. However, when the number of flat rolls is two, the bulge height of the raised portion A can be further reduced and the outer diameter variation in the axial direction can be further reduced. This is because the size of the raised portion A generated per revolution of the material to be processed when the product recess is processed by the rolling roll is larger than that in the case of one rolling roll.
The case of books is larger. Therefore, when the number of flat rolls is one, the raised portion A, which is formed larger by the two rolling rolls, is pressed once per revolution of the material to be processed for smoothing and straightening. On the other hand, when the number of flat rolls is two, the bulge portion A formed to be relatively small at the time of processing the concave portion of the product by one rolling roll.
This is because is pressed twice per revolution of the material to be processed to smooth and correct it.

Raised part A by the above flat roll
The effect of straightening is the rolling rolls 1A, 1B (1) shown in FIG.
The larger the tip end width T of the annular protrusion 1a, and the smaller the ratio P / T between the connecting pitch P and the tip end width T when the tip end width T is the same, the above-mentioned raised portion A. Although the bulge height becomes higher, when two flat rolls are used, this can be smoothed more reliably.

In the present invention described above, the rolling roll 1
Only A and 1B (1) are driven to rotate, and the flat roll 2
It is desirable that (2A, 2B) can be driven and rotated freely. This is because there is always a difference between the roll peripheral speed of the portion that abuts the material 3A (3B) to be processed and the peripheral speed of each portion of the material that is actually being processed due to the difference in the radius of gyration.
Unless the rolling speed of the rolling rolls 1A, 1B (1) having a and the flat rolls 2 (2A, 2B) is gradually changed during rolling, the amount of material slippage on the roll surface is large at any time. As a result, seizure flaws occur and roll wear becomes noticeable.

However, it is actually extremely difficult to control the rotational speed of the roll during the reduction to eliminate the slip amount, and if it is attempted to control it, a control device for that purpose requires a large amount of cost and is economically economical. It is difficult to adopt.

However, one roll, that is, the flat roll 2 (2A, 2B) is used as the work material 3A (3B).
If it is made non-driving so as to follow the rotation only by the frictional force from the contact surface with, all the rolls will rotate at a substantially balanced rotation speed.

As a result, in addition to preventing the occurrence of seizure flaws, it becomes possible to suppress roll wear. In addition, flat roll 2 (2A,
Since 2B) is not driven, the equipment cost can be reduced as much as the number of roll shafts required for driving this is unnecessary.

Further, in the above-mentioned method of the present invention, it is desirable that only the rolling rolls 1A, 1B (1) can be displaced in their axial center positions and the flat rolls 2 (2A, 2B) are fixedly installed. When focusing on the positional relationship between the flat rolls 2 (2A, 2B) and the work material 3A (3B) in the present invention, this is the outside of the work material 3A (3B) pressed by the flat rolls 2 (2A, 2B). The diameter do is larger than the outer diameter of the material before processing because the material removed by forming the concave portion (small diameter portion 3a) by the rolling rolls 1A, 1B (1) flows into the convex portion (large diameter portion 3b). Become. But,
Since the cross-sectional area is proportional to the square of the diameter, the convex outer diameter do is closer to the material outer diameter before processing than the concave outer diameter di. Moreover, the larger the processing amount and the smaller the outer diameter di of the concave portion, the smaller the contribution ratio of the outer diameter do of the convex portion to the diameter expansion. Therefore, the unprocessed material 3A (3B) in the unprocessed part
The change in the separation distance of the axis of the flat roll 2 (2A, 2B) with respect to the rotation center of the flat roll 2 (2A, 2B) is the change of the separation distance of the axis of the rolling rolls 1A, 1B (1) from the axis of the material 3A (3B) to be processed. It is much smaller than the degree.

Therefore, for example, in order to perform rolling on the entire length or the region of arbitrary length of the work material 3A (3B) having a length of 4 to 5 m, the rolling roll 1A having the length shown in FIG. 1B (1) and flat rolls 2 (2A, 2B) are used, the roll interval of each roll is opened each time, the material 3A (3B) to be processed is fed in the axial direction thereof, and continuously and intermittently rolled. When it is necessary to process, the work material 3A
It is preferable that the axial center position of (3B) does not change so much that the pressing position thereof is substantially constant.
If B) is fixedly installed, it is easy to maintain the axis center substantially constant. In this case, if the flat roll 2 (2A, 2B) has a freely displaceable shaft center, an auxiliary device for special position adjustment such as a material steady rest guide provided before and after the rolling device is necessary. Depending on the situation, it is not necessary, and the pressure reducing mechanism for adjusting the position is also unnecessary.

As a result, the equipment cost can be reduced.

In the manufacturing method of the present invention described above, as shown in FIG. 3, the small diameter portion 3a and the large diameter portion 3b having the same outer diameter and axial length direction dimension.
Is basically formed at the same pitch, but is not limited to this. That is, in the method of the present invention, the use of the flat roll restricts the outer diameter do of the large diameter portion 3b to be the same, but the outer diameter D10 and the tip end width T of the annular projection 1a are different. By using the rolling rolls arranged at the pitch P, it is possible to arbitrarily form the large diameter portion 3b having a different axial length dimension and the small diameter portion 3a having a different outer diameter di from the axial length dimension t thereof. . However, in this case, the permissible range is naturally restricted by the mass balance because the outer diameter do of the large diameter portion 3b is determined by the amount of the material discharged by the annular protrusion 1a when the small diameter portion 3a is formed by the rolling roll. Needless to say.

When forming the small diameter portion 3a by the annular projection 1a of the rolling roll, if the load pushing the material by the rolling roll is P1 and the load supporting the material by the flat roll is P2, both loads are shear loads. It acts on the step. If this shear load becomes excessive, if the material to be processed is a material having poor workability such as an alloy steel such as Cr-Mo steel, material breakage may occur at the portion. However, as a result of the present inventors' investigations on various materials, when the outer diameter di of the small diameter portion 3a and the width t in the axial direction thereof are set so as to satisfy the relationship of It turned out that there was no problem.

Therefore, it is preferable to set the outer diameter di of the small diameter portion 3a and the width t in the axial direction thereof so as to satisfy the following formula.

3.5t <di Moreover, the taper angle α provided at the tip of the annular projection 1a of the rolling roll is more than 0 ° and 90 ° or less, and the predetermined large-diameter portion 3b is secured in the axial length direction. Any angle may be used as long as it is within the range. However, if the taper angle α is made too small, the load required for forming the small diameter portion 3a becomes large, and the diameter of the roll main body and its supporting shaft must be made large, which leads to an increase in the size of equipment and is not economical. On the other hand, if it is too large, material breakage easily occurs due to shearing at the break. Therefore, the taper angle α is 60 to 80.
° is preferable.

[0046]

EXAMPLES Examples of the present invention will be described below with reference to specific production examples. It should be noted that each dimension specification is indicated by using the reference numerals shown in FIG.

<< Manufacturing Example 1 >> Using the apparatus shown in FIG.
Using a solid round bar made of C having an outer diameter of 32 mm as a material, a stepped bar having the following dimensions was manufactured. The rolling roll and the flat roll used at this time have the following dimensional specifications, and the solid round bar of the material was heated to 1200 ° C. before being processed.

[Target Product Dimension] Large Diameter Outer Diameter (do) = 35 mm, Small Diameter Outer Diameter (di) = 20 mm, Small Diameter Axial Length (t) = 3.5 mm, Pitch (p ) = 15 mm, taper angle (α) of stepped portion = 70 °, number of small diameter portions = 5 places.

[Dimensional Specifications of Rolling Roll (Common to 2 Rolls)] Roll Material = SCM440, Outer Diameter of Protrusion (D1O) = 100 mm, Outer Diameter of Roll (D1i) = 80 mm, Tip Width (T) = 3 0.5 mm, pitch (P) = 15 mm, number of protrusions = 5.

[Specifications of Flat Roll Dimension (1 Roll)] Roll material = SCM440, outer diameter (D2) = 90 mm, body length (L) = 100 mm.

[Reduction Condition] (Same for all three rolls) Roll rotation speed = 100 rpm, Reduction stroke = 0.24 mm / revolution, Processing time = about 12 seconds.

As a result of the production under the above conditions, it was possible to obtain a stepped rod having almost the same dimensional specifications as the target. That is, the outer diameter of the large diameter portion of the product is 35.15 at both ends.
mm, the central portion was 34.85 mm, and the variation in the outer diameter in the axial direction was 0.3 mm.

Manufacturing Example 2 Under the same conditions as in Manufacturing Example 1, except that the apparatus shown in FIG. 2 was used, that is, the number of flat rolls was changed to 2, and the rolling stroke of each roll was set to 0.12 mm / revolution. The same stepped rod as in Production Example 1 was produced.

As a result, similar to the case of Production Example 1, it was possible to obtain a stepped rod having almost the same dimensional specifications as the target. That is, the outer diameter of the large diameter part of the product is 35.0 at both ends.
The diameter was 5 mm, the central portion was 34.95 mm, and the variation of the outer diameter in the axial direction was 0.1 mm, and a flatter large-diameter portion was obtained as compared with the case of Production Example 1.

<Manufacturing Example 3> In order to further confirm the difference in effect due to the difference in the number of flat rolls, the tip end width T of the protruding portion of the rolling roll is 5.5 mm so that the raised portion A becomes more prominent. The connection pitch P is 15 mm, that is, the length t in the axial direction of the small diameter part of the product is 5.5 mm, and the pitch p is
Rolling roll with a diameter of 15 mm and a diameter of 3
A stepped rod was manufactured under the same conditions as in Production Examples 1 and 2 except that a 0.5 mm material was used.

As a result, it was possible to obtain a stepped rod having almost the same dimensional specifications as the target. That is, the outer diameter of the large diameter portion of the obtained product was 35.50 mm at both ends and 34.50 mm at the central portion according to the method of Production Example 1, and the variation of the outer diameter in the axial direction was 1. Although it was 0 mm, in the case of the method of Production Example 2, both ends were 35.25 mm, the central portion was 34.75 mm, and the outer diameter variation in the axial direction was 0.5 mm. According to the above, a flatter large diameter portion was obtained.

Manufacturing Example 4 Of the apparatus shown in FIG. 1, only the rolling rolls 1A and 1B are rotationally driven, and the flat roll 2
A stepped rod was manufactured under the same conditions as in Production Example 1 except that the non-drive following rotation was made possible.

As a result, it was possible to obtain a stepped rod having the intended size specifications. In addition, the peripheral speed difference between the rolling roll and the flat roll is almost eliminated, the material is rotated so that slippage does not occur on the surface, and seizure flaws do not occur at all. Property,
In particular, a product having a smoother surface texture on the tapered surface of the large diameter portion was obtained.

Manufacturing Example 5 In the apparatus shown in FIG. 1, only the rolling rolls 1A and 1B are displaced in axial position, the flat roll 2 is fixed in position, and the rolling stroke of the rolling roll is reduced to 0. A stepped rod was produced under the same conditions as in Production Example 1 except that the rod was set to 36 mm / rotation. In addition, the material was moved in the axial direction and subjected to rolling processing at multiple locations.

As a result, since the position of the flat roll is fixed, the axial center position of the material to be processed hardly changes, and the rolling process can be performed without changing the axial center position of the entire material.
In addition, stepped rods having the desired dimensional specifications were obtained at any axial length position.

Comparative Example Using the conventional apparatus shown in FIG. 8 which is the same rolling roll as the dimensional specifications used in Production Example 1, the stepped bar having the same dimensional specifications as in Production Example 1 is used as in Production Example 1. It was manufactured under the conditions.

As a result, the height of the large diameter portion is 2.5 mm at both ends.
A swelling portion reaching up to (5 mm in diameter) was formed, and it was necessary to remove this swelling portion after the rolling process step to obtain a product.

The above is the result of using medium carbon steel of ordinary steel as the material. Although detailed data is omitted, the material may be special steel or other metal material such as aluminum alloy. Similar results were obtained.

[0064]

According to the manufacturing method of the present invention, a local roll-up portion of the material generated by the pressing of the annular projection of the rolling roll can be processed by the flat roll while flattening it immediately during the processing. . As a result, it becomes possible to manufacture a stepped rod having a flat large-diameter portion having no surface defects in one step and at a high yield without removing the material. When using two flat rolls,
The flatness of the large diameter portion can be further improved. Further, when the flat roll is made to rotate freely without being driven and only the rolling roll is driven to rotate, the occurrence of seizure flaws can be prevented and roll wear can be suppressed, and the surface quality of the small diameter portion including the step portion can be improved. be able to.

Furthermore, by fixing the position of the flat roll,
When only the rolling roll is allowed to be displaced in its axial center position, it is possible to form a stepped portion having the same property even if rolling processing is performed at a plurality of positions in the axial direction of the material.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of an embodiment of the present invention.

FIG. 2 is a front view showing another example of the embodiment of the present invention.

3 is a side view of the I-I line in FIG. 1 and the II-II line in FIG.

FIG. 4 is a front view for explaining a conventional method.

5 is a development side view taken along the line IV-IV of FIG.

6 is a partially omitted plan view taken along the line III-III of FIG.

FIG. 7 is a side view for explaining a drawback of the conventional method.

FIG. 8 is a front view for explaining another conventional method.

9 is a development side view taken along the line VV of FIG.

FIG. 10 is a side view for explaining a drawback of another conventional method.

[Explanation of symbols]

 1, 1A, 1B: rolling roll, 2, 2A, 2B: flat roll, 3A, 3B: material to be processed, 1a: annular protrusion, 3a: small diameter part, 3b: large diameter part.

Claims (4)

[Claims] 1. A plurality of annular projections 3 formed in the axial direction.
The three rolling rolls are radially arranged around the metal material to be processed so that the axis thereof is parallel to the axial center line of the metal material to be processed having a circular cross section, and formed by the three rolling rolls. A method of hot forming an annular projection on the outer peripheral surface of a metal material to be processed while changing the distance between the axes of the rolling rolls so that the diameter of the tangent circle is gradually reduced. A method for producing a stepped metal material, wherein at least one of the rolls is a flat roll. 2. The method for producing a stepped metal material according to claim 1, wherein the number of flat rolls is two. 3. The method for producing a stepped metal material according to claim 1, wherein the rolling roll having the annular protrusion is a drive rotation roll and the flat roll is a non-drive free rotation roll. 4. The method according to claim 1, wherein only the axial center position of the rolling roll having the annular projection is displaced.
The method for producing a stepped metal material according to any one of 1.