JP3818094B2 - Circular material forging method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method by forging a circular material having a circular outer surface shape.
[0002]
[Prior art]
Forged products with a circular outer surface shape such as wheels, gears, rings, etc., after performing hot forging multiple times to reduce the material of the outer surface shape in the axial direction, perform molding and heat treatment as necessary, Manufactured by machining into product dimensions. For example, when manufacturing a wheel for a railway, a cylindrical material is heated, and the volume distribution in the radial direction is performed by the first wasteland forming step of reducing in the axial direction, and then by the second wasteland forming step. The outer shape formed into the approximate shape of the wheel is made into a rough wasteland, and after finishing rolling and finishing forging, heat treatment is performed as necessary, and then the wheel is formed by machining. In addition, annular products such as rings are rounded with rough forging as a rough ground forming process by rolling up the material in the axial direction, and then processed into circular products by finish rolling, finish forging, machining, etc. .
[0003]
In the rough ground forming by forging in the above-described process, a mold (hereinafter, referred to as an open mold) in which a side wall for restraining the outer peripheral surface of the workpiece being forged is not provided is often used. If an open mold is used, there is an advantage that it is easy to remove the scale that peels off during hot forging. However, when an open mold is used, forging is completed without the outer peripheral surface of the work piece being constrained, so the displacement of the material to be inserted relative to the mold, the shape of the material is poor, and the temperature uniformity of the material If there is a defect, the workpiece during forging will not be uniformly stretched in the circumferential direction with respect to the mold axis, and the dimension from the mold axis to the outer peripheral surface of the waste will be in the circumferential direction of the waste. A non-uniform dimension defect (hereinafter, this dimension defect is referred to as uneven thickness) occurs.
[0004]
If an excessive thickness deviation occurs at the stage of roughing, the thickness deviation is not corrected in finish rolling or finish forging, and as a result, the dimensional accuracy of the product is impaired. Further, assuming that uneven thickness occurs in rough ground forming, measures such as increasing the machining allowance in machining are taken, but increasing the machining allowance decreases the yield.
[0005]
Also in finish forging, if there is a displacement of the position of the inserted wasteland with respect to the mold, uneven shape such as uneven thickness of the wasteland, poor heat uniformity of the wasteland, etc. The problem that the occurrence is unavoidable arises.
[0006]
On the other hand, when a die having a side wall with an inner diameter equal to the outer diameter of the wasteland is used for forging in wasteland forming, the portion of the outer peripheral surface of the workpiece that extends earlier is restrained by the side wall of the die at the end of the forging. Therefore, uneven thickness is reduced as compared with the case where an open mold is used. However, when forging is performed using this mold, when a situation occurs in which the circumferential direction of the workpiece is extremely extended during forging, the portion is not only restrained by the side wall, but also the side wall Burr is generated by protruding from the upper or lower part of the surface. Therefore, man-hours for removing burrs are required, and the yield is reduced. In addition, wrinkles may occur in wasteland and molds.
[0007]
Japanese Laid-Open Patent Publication No. 7-308730 discloses a method for producing a rough terrain with good dimensional accuracy in railroad wheel rough terrain forming. In this method, a notch portion is formed at the corner of the rim, which is the outer periphery of the wasteland, and an amount of projection corresponding to the lacking portion is formed on the end surface of the rim. Is used to fill the corners of the rim. According to this method, even if a small press is used, the corner portion of the rim can be filled with the material. However, the uneven thickness in the circumferential direction of the wasteland cannot be eliminated.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to reduce the uneven thickness generated in a circular material when manufacturing a circular material having a circular outer surface shape by forging, improve the dimensional accuracy, and improve the manufacturing yield of the circular material. It is to provide a forging method.
[0009]
[Means for Solving the Problems]
The gist of the present invention is that, when a material having a circular outer surface shape is squeezed in the axial direction using an open and closed upper and lower molds and forged into a circular material having a circular outer surface shape, the inner diameter is expressed by the following formula (1) A ring tool having a diameter d satisfying the conditions specified in the above is provided with its axis aligned with the axis of the mold, and in this state, the material being forged is brought into contact with the inner surface of the ring tool, and then the ring A method for forging a circular material, characterized by removing a tool and forging.
[0010]
D + 2E ≦ d ≦ D ₁ (1)
Here, D: Maximum diameter of material (mm), E: Displacement amount (mm) between mold axis and material axis when material is inserted, D ₁ : Reduction amount is 70% of total reduction amount The average outer diameter of the material at the time of (mm) ”.
[0011]
The present inventors conducted various model experiments on the rough ground forming process in the manufacture of railway wheels, and repeated research on prevention of uneven thickness during the rough ground forming. As a result, the following knowledge was obtained. The present invention has been completed based on this finding.
[0012]
When a raw material is pressed down in the axial direction using open and closed upper and lower molds to form a rough ground, a ring tool with a predetermined inner diameter is placed around the work piece at the midpoint of the reduction, and the axis is the axis of the mold. In this state, the reduction is advanced to bring the material being forged into contact with the inner surface of the ring tool, and after that, the ring tool is removed and the reduction is effected by the open upper and lower molds. Can be suppressed.
[0013]
That is, when the diameter of the material increases by being axially squeezed by the open upper and lower molds, the material is pressed against the inner surface of the ring tool provided with the axis aligned with the axis of the mold. As a result, the outer peripheral surface of the material being forged is brought close to a circle having the same axis as that of the mold, and as a result, the deviation caused by the unevenness of the deformation due to the displacement of the material, the shape of the material, and the heat uniformity of the material. The meat is corrected. Thereafter, if the material with the uneven thickness corrected is squeezed down to the end in a state where the ring tool is removed, the uneven thickness generated thereafter is extremely small, which leads to the suppression of the final uneven thickness.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the method for forging a circular material according to the present invention will be described by taking as an example a rough ground forming of a railway wheel (hereinafter simply referred to as a wheel).
[0015]
FIG. 1 is a longitudinal sectional view showing an example of the periphery of a mold for explaining a state immediately before the start of rolling in the first wasteland forming step for wheels. FIG. 2 is a longitudinal sectional view showing an example of the periphery of a mold for explaining a state in the middle of rolling (when the inner surface of the ring tool is filled with material) in the first rough ground forming step of the wheel. FIG. 3 is a longitudinal sectional view showing an example of the periphery of a mold for explaining a state when the rolling in the first wasteland forming step of the wheel is finished.
[0016]
In these drawings, the raw material 1a is loaded on the lower mold 2, and the axial reduction is started by the lowering of the upper mold 3 (FIG. 1), and the outer periphery of the material 1b being forged in the middle of the reduction. The surface is pressed against the inner periphery of the ring tool 4 to fill the material 1b with the inner surface of the ring tool 4 (FIG. 2), and then the rolling is completed with the ring tool 4 removed to produce the rough ground 1c. (FIG. 3).
[0017]
The material is made of, for example, carbon steel defined in JIS E 5402-1, and is a cylindrical body having an outer diameter D and a length H obtained by cutting, for example, a round billet having a circular outer surface shape into a predetermined length.
[0018]
Lower mold 2, for example, the annular projection 2a of the axis O ₂ centered on the outer edge of the upper surface is formed also around the axis O ₂ in the central portion, the protrusion height of the annular A circular protrusion 2b lower than 2a is formed, and an annular groove 2c is formed between the annular protrusion 2a and the circular protrusion 2b. The lower mold 2 is a so-called open mold without a side wall. The upper mold 3 is, for example, an open mold in which a gentle protrusion 3a is formed at the center of the lower surface thereof, and no side wall is provided like the lower mold.
[0019]
At the time of rough ground forming, the upper die 3 is squeezed down so that the material 1a heated to the forging temperature is squeezed in the axial direction by the lower die 2 and the upper die 3, and the lower surface is the lower die. A shape corresponding to the upper surface of the mold 2, and the upper surface is formed into a rough ground 1 c having a shape corresponding to the lower surface of the upper mold 3. By this forging, the rim equivalent portion of the wheel is formed on the waste land 1c by the outer edge portion of the annular protrusion 2a formed on the lower mold 2 and the upper mold 3, and the circular shape formed on the lower mold 2 is formed. The protrusion 2b, the annular groove 2c, and the upper mold 3 form a wheel boss equivalent portion.
[0020]
In the present invention, a ring tool 4 having an inner diameter d, which will be described later, is provided before or during forging. The ring tool 4 only needs to have a circular inner surface shape, and is not concerned with the outer surface shape. The height may be a height including a region where the material 1b being forged is pressed against the inner surface of the ring tool 4. Moreover, the ring tool divided | segmented into the circumferential direction may be sufficient.
[0021]
The ring tool 4 is provided between the lower mold 2 and the upper mold 3 with a holding tool (not shown) so that its axis coincides with the axis O ₂ of the lower mold 2. Retained.
[0022]
In this state, the upper die 3 is lowered, and the material 1 b is continuously reduced by the lower die 2 and the upper die 3 until the entire outer peripheral surface of the material 1 b comes into contact with the inner peripheral surface of the ring tool 4. In this case, of the outer peripheral surface of the material 1b, in order from the largest part distance from the axis O ₂ of the lower die 2, pressed against the inner surface of the ring tool 4. The portion pressed first on the inner surface of the ring tool 4 is restrained from further extending in the outer surface direction, and the material 1b of the portion is extended along the inner surface of the ring tool 4.
[0023]
Of the outer peripheral surface of the material 1b, the distance is the smallest part of the axis O ₂ of the lower die 2, after the last pressed against the inner surface of the ring tool 4, the ring tool 4 is removed, the material 1b In the state where the restraint of the outer peripheral surface by the ring tool 4 is released, it is rolled down to the end.
[0024]
When the ring tool 4 is removed, the outer diameter of the material 1b matches the inner diameter d of the ring tool 4. Further, the ring tool 4 is provided with its axis aligned with the axis O ₂ of the lower mold 2. Therefore, the outer peripheral surface of the material 1b is formed in a circular shape having a diameter d with the axis O2 of the lower mold ₂ as the center. That is, the lower metal mold based on the position shift of the lower mold of the material 1a inserted on the lower mold _{2 with} respect to the axis O2, the shape defect due to the uneven thickness inherent in the material 1a, the heat uniformity defect of the material 1a, etc. The uneven thickness due to non-uniform extension from the axis O _{2 of the} mold is corrected. Therefore, even if the rolling is applied without using the ring tool 4 after that, the uneven thickness hardly occurs.
[0025]
The ring tool 4 is removed at a later time as much as possible in order to increase the contact area between the outer peripheral surface of the material 1b and the inner surface of the ring tool 4 to increase the uneven thickness suppressing effect. Is preferably filled. The timing for removing the ring tool 4 is determined within a range in which the rolling load and the material 1b do not bite out from the upper part or the lower part of the ring tool 4. It is not always necessary to fill the ring tool 4 with the material 1b, and the outer periphery of the material 1b may only be brought into contact with the inner surface of the ring tool 4, but it is preferable to fill the ring tool 4.
[0026]
As described above, in order to correct the uneven thickness generated in the material 1b by bringing the outer peripheral surface of the material 1b into contact with the inner surface of the ring tool 4, it is necessary to set the inner diameter of the ring tool 4 appropriately. Therefore, in the present invention, the inner diameter of the ring tool 4 is set to a diameter d that satisfies the condition defined by the following equation (1).
[0027]
D + 2E ≦ d ≦ D ₁ (1)
Here, D is the maximum diameter of material 1a (mm), E is the displacement of the axis O ₁ of the shaft center O ₂ and the material 1a of the lower die 2 when the charged material 1a on the lower die 2 The amount (mm), D ₁ is the average outer diameter (mm) of the material when the reduction amount is 70% of the total reduction amount.
[0028]
As described above, for example, the material 1a obtained by cutting a round billet into a predetermined length is not necessarily a perfect circle, and the outer diameter at each position in the circumferential direction may be different. In the case of charged material 1a on the lower die 2, not necessarily to the axis O ₁ of the material 1a coincides with the axis O ₂ of the lower die 2, the axis O ₁ and the lower material 1a The position of the mold 2 with respect to the axis O ₂ may be displaced.
[0029]
On the other hand, in order to correct the uneven thickness by constraining the outer peripheral surface of the material 1b by the ring tool 4, the axial center of the ring tool 4 is provided so as to coincide with the axial center of the lower mold 2, and after the material 1a starts rolling down. It is necessary to restrain the outer peripheral surface.
[0030]
In this way, even if the material 1a is not a perfect circle and the material 1a is misaligned when loaded on the lower mold 2, the ring tool 4 does not interfere with the material 1a and the ring tool 4. Is provided, the inner diameter (diameter) d of the ring tool 4 needs to be not less than (D + 2E).
[0031]
The inner diameter d of the ring tool 4, the material 1a when the total rolling amount when molded into wasteland 1c and Y, reduction amount of a material mean outside diameter D ₁ of the following at the time of 0.7Y. That is, when the ring tool 4 having an inner diameter equal to the outer diameter of the wasteland 1c is used, the uneven thickness is corrected as in the case of using a mold having an inner diameter equal to the outer diameter of the wasteland. However, when a situation occurs in which a part of the circumferential direction of the material is extremely extended during forging, the part is not only restrained by the inner surface of the ring tool 4 but also protrudes from the upper part or the lower part of the ring tool 4. Burr occurs. Therefore, in the present invention, reduction rate of the upper mold 3 is, the maximum value of the internal diameter d of the average outer diameter D ₁ of the ring tool 4 of the material at the time of a 70% of the total reduction rate Y by the upper mold 3 To do.
[0032]
Thus, the inner diameter d of the ring tool 4, if the average outer diameter D ₁ of the material at the time point when 70% of the total reduction rate Y, part of the peripheral direction of the material is extremely extended during forging Even if such a situation occurs, it is restrained by the inner surface of the ring tool 4 while the amount of extension is relatively small, so that the generation of burrs is prevented.
[0033]
The inner surface of the ring tool 4 does not have to have an inner diameter d equal in the height direction. For example, the inner diameter of the upper part may be a conical surface having a larger inner diameter than the lower inner diameter. However, also in this case, the inner diameter of the upper part and the inner diameter of the lower part need to satisfy the formula (1).
[0034]
Here, the maximum diameter D of the material 1a is assumed to be the maximum value of the allowable value when the outer diameter is set for the material, and is assumed from the actual value when the allowable value is not set. The maximum value.
[0035]
Displacement E between the axis O ₁ of the shaft center O ₂ and the material 1a of the lower die 2 when the inserted material 1a on the lower die 2, forging machine lower die 2 and the material instrumentation that are used There are a mechanical displacement with respect to the insertion device and a displacement of the material 1a with respect to the lower mold 2 based on the shape of the material 1a and the shape of the lower mold 2. Therefore, for example, the displacement amount E is set based on the actual value.
[0036]
Note that the total amount of reduction Y is obtained when a part of the lower surface of the upper mold 3, for example, the approximate center of the lower surface of the upper mold 3 in FIG. 1 contacts the upper surface of the material 1 a charged on the lower mold 2. To the amount of decrease in the distance between the lower mold 2 and the upper mold 3 until the end of the reduction, and is determined by the dimensions of the material 1a, the dimensions of the lower mold 2 and the upper mold 3 to be used, and the like.
[0037]
The average outer diameter D ₁ of the material at the time point when 70% of the total reduction amount Y, the dimensions of the material 1a, the shape of the lower die 2, based on such shape of the upper die, or obtained by calculation, or What is necessary is just to obtain | require from a track record value.
[0038]
The range of the inner diameter d of the ring tool 4 is defined as described above. A ring tool 4 having an inner diameter d within this range is prepared, and the ring tool 4 is provided with its axis aligned with the axis of the lower mold 2 before or during the reduction. The contact is made with the inner surface of the ring tool 4, and then the ring tool 4 is removed, and the reduction is continued to produce the rough ground 1c. The wasteland 1c is formed into a rough shape of a wheel by a second wasteland forming process, then finish-rolled or finish-forged, and then subjected to heat treatment as necessary, and then turned into a wheel by machining.
[0039]
In the above description, the ring tool 4 is provided between the lower mold 2 and the upper mold 3 with its axis center aligned with the axis O ₂ of the lower mold 2. May be provided so as to coincide with the axial center of the lower mold 2, and an intermediate position between the axial center of the lower mold 2 and the axial center of the upper mold 3 may be obtained and provided to coincide with the intermediate position.
[0040]
The ring tool 4 is provided separately from the lower mold 2 and the upper mold 3. However, one or both of the lower mold 2 and the upper mold 3 is a mold having a shape integrally including a ring having an inner diameter d. The material may be squeezed down to press the outer peripheral surface of the material against the inner surface of the ring, and thereafter, the die may be replaced with an open die without a ring and squeezed down to the end.
[0041]
Although the above description is a case of wasteland forming by the first wasteland forming process when manufacturing a wheel, it can also be applied to the second wasteland forming process or finish forging. Moreover, it can employ | adopt not only a wheel but disk-shaped or annular | circular shaped forging materials, such as a gear and a ring, and a circular outer surface shape. The material is not limited to carbon steel, and may be a steel product such as alloy steel or a non-ferrous metal such as aluminum.
[0042]
【Example】
10 columnar materials consisting of carbon steel containing C: 0.70%, Si: 0.15%, Mn 0.60% in mass%, with an outer diameter of 450 mm and a length of 330 mm are prepared. After heating to 1250 ° C., the first waste land was formed by the method shown in FIG. As the upper and lower molds, open molds having the shape shown in the figure were used.
[0043]
A ring tool with an inner diameter of 500 mm (corresponding to the average outer diameter of the material when the reduction amount is 23% of the total reduction amount) is arranged so that its axis coincides with the axis of the lower mold, and in this state the upper mold The mold is squeezed and a 60 mm reduction is applied by the upper and lower molds, the entire outer peripheral surface of the work piece is brought into contact with the inner surface of the ring tool, and then the ring tool is removed to reduce to the bottom dead center. finished. The total amount of reduction at this time was 270 mm.
[0044]
Next, the second rough ground forming was performed by using a known method to form the approximate shape of the wheel using the upper and lower molds, and the rough ground forming was completed. Thereafter, molding by a conventional wheel mill and finish molding by rotary forging were performed to produce a total of 10 finished molded products having an outer diameter of 900 mm. The finished molded product was machined to obtain a wheel having a normal size and shape.
[0045]
As a result of inspecting the shapes of these wheels, none of them was thin (defective shape), and a good-shaped wheel was obtained. Further, as a result of calculating the finishing yield ((W2 / W1) × 100) from the mass W1 of the finished molded product before machining and the mass W2 after machining, the average value of 10 wheels was 91%. It was.
[0046]
Next, prepare 10 pieces of each of a plurality of lengths that are 1 to 10 mm shorter than the length of the above materials, manufacture wheels from these materials by the same method as above, and check and finish the shape of the wheels. Yield was calculated. As a result, the finishing yield at the limit at which all 10 wheels had a good shape was 92.5%.
[0047]
As a comparative example, except that no ring tool is used in the first rough ground forming, and 10 wheels are manufactured under the same conditions as in the above method, all 10 wheels have a good shape. The length was 330 mm, and when a material having a shorter length was used, a lack of thickness occurred. That is, the finishing yield at the limit at which all 10 wheels are in good shape was 91%. That is, according to the method of the present invention, it is understood that the finishing yield is improved.
[0048]
【The invention's effect】
According to the method for forging a circular material of the present invention, when manufacturing a circular material having a circular outer surface shape by forging, the uneven thickness generated in the circular material is reduced to improve the dimensional accuracy, thereby improving the manufacturing yield of the circular material. Can be made.
[0049]
[Means for Solving the Problems]
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example around a mold for explaining a state immediately before the start of rolling in a first rough ground forming step of wheels.
FIG. 2 is a longitudinal sectional view showing an example around a mold for explaining a state in the middle of rolling (when an inner surface of a ring tool is filled with a material) in a first rough ground forming step of a wheel.
FIG. 3 is a longitudinal cross-sectional view showing an example of the periphery of a mold for explaining a state when the reduction in the first wasteland forming step of the wheel is completed.
[Explanation of symbols]
1a: material,
1b: material being forged,
1c: Wasteland
2: Lower mold,
3: Upper mold,
4: Ring tool.

Claims (1)

Satisfying the condition that the inner diameter is defined by the following formula (1) when a material with a circular outer surface is forged into a circular material with a circular outer surface shape by rolling it down in the axial direction using an open upper and lower mold A ring tool having a diameter d to be aligned is aligned with the axis of the mold, and in this state, the forging material is brought into contact with the inner surface of the ring tool, and then the ring tool is removed and forging is performed. A method for forging a circular material characterized by
D + 2E ≦ d ≦ D ₁ (1)
Where D: Maximum material diameter (mm)
E: Displacement (mm) between the axis of the mold and the axis of the material when the material is charged
D ₁ : Average outer diameter (mm) of the material when the reduction amount is 70% of the total reduction amount

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