JP2004314083A - High dimensional precision pipe and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high dimensional precision pipe which has satisfactory fatigue strength and can be manufactured at a low cost for a broad range of size requirement of the pipe and a manufacturing method for it. <P>SOLUTION: The high dimensional precision pipe is manufactured by pushing a metal pipe 5 in a cavity of die 2 preferably in an integrated type and/or a fixed type, keeping a plug 1 inserted inside the pipe 5. The pipe has a dimensional deviation of not more than 3.0% in one or two or more among an outer diameter deviation, an inner diameter deviation and a circumferential thickness deviation in a passed through state, or furthermore, the wall thickness of the metal pipe at the exit side of the die is not more than that at the entry side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３３】
表１より、実施例１〜３の製品管は、寸法精度が著しく良好で、疲労強度も最も良好であり、特にプラグをフローティングさせると寸法精度はさらに良好であった（実施例３）。これに対して、従来の引き抜きでは製品管の寸法精度が低下しその結果疲労強度も著しく低下していた（比較例１）。ロータリー鍛造機を用いた押し込みでも製品管の寸法精度は低下し（比較例２）、増肉させるとさらに低下し（比較例３）、十分な疲労強度を得ることはできなかった。
【００３４】
【発明の効果】
本発明の高寸法精度管は著しく良好な寸法精度を有しその結果良好な疲労強度を具えたものであり、しかも低コストで製造しうるから、自動車用駆動系部品等の軽量化促進に多大に寄与するという優れた効果を奏する。また、本発明の製造方法によれば、広範囲の管要求サイズに亘り寸法精度が著しく良好な金属管を低コストで製造することができるようになるという優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明で用いる押し抜きの実施形態を示す説明図である。
【図２】従来の引き抜きの実施形態を示す説明図である。
【図３】従来の分割ダイスを装着して復動させるロータリー鍛造機による押し込みの実施形態を示す説明図であり、（ａ）は管中心軸を含む断面図、（ｂ）は（ａ）のＡ−Ａ矢視図である。
【図４】疲労試験の応力と耐久回数の関係を示す特性図である。
【符号の説明】
１ プラグ
２ ダイス（例：一体型固定ダイス）
３ ロータリー鍛造機
４ 分割ダイス
５ 管（金属管、鋼管）
６ 管押し機
７ 管引き機
８ 押し込み力
９ 引き抜き力
１０ 復動[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-dimensional precision pipe and a method for manufacturing the same, and more particularly to a high-dimensional precision pipe which can be advantageously applied to a part requiring high dimensional precision, such as a drive system part for an automobile, and a method for manufacturing the pipe. The present invention relates to a method for manufacturing a high-dimensional precision pipe suitable for use in a pipe.
[0002]
[Prior art]
Metal pipes such as steel pipes are generally roughly classified into welded pipes and seamless pipes. Welded pipes are manufactured by rounding the width of the strip and welding the ends of the rounded width against each other, such as ERW pipes, while seamless pipes are made by drilling a mass of material at high temperatures. It is manufactured by rolling it with a mandrel mill or the like. In the case of a welded pipe, the bulge of the welded portion is ground after welding to improve the dimensional accuracy of the pipe, but the wall thickness deviation exceeds 3.0%. Further, in the case of a seamless pipe, eccentricity tends to occur in the drilling step, and the eccentricity tends to cause a large thickness deviation. Efforts have been made to reduce this thickness deviation in the post-process, but it is still not possible to reduce it sufficiently, and more than 8.0% remains in the product stage.
[0003]
Recently, due to environmental problems, the weight of automobiles has been spurred, and drive system components such as drive shafts are being replaced with solid metal rods and hollow metal tubes. High dimensional accuracy of 3.0% or less, more strictly 1.0% or less, in thickness, inner diameter, and outer diameter deviations is required for metal pipes of such drive system parts for automobiles. This is because drive train components must withstand fatigue caused by long-distance running of automobiles. This is because fatigue fracture tends to progress as a starting point and the fatigue strength is significantly reduced. Therefore, in order to maintain sufficient fatigue strength, it is necessary to improve the accuracy of the wall thickness, inner diameter, and outer diameter of the metal pipe.
[0004]
As a means of improving the accuracy of the wall thickness, inner diameter, and outer diameter of a metal pipe, a conventional method of drawing a steel pipe (both a welded pipe and a seamless pipe) cold by using a die and a plug after forming the pipe (so-called cold pipe). Towing method) is taken. In recent years, a manufacturing technique has been proposed in which a steel pipe is pressed into a die hole using a rotary forging machine incorporating a die divided in a circumferential direction (see Patent Documents 1, 2, and 3).
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 9-262637 [Patent Document 2]
Japanese Patent Application Laid-Open No. 9-262519 [Patent Document 3]
JP-A-10-15612
[Problems to be solved by the invention]
However, in the above-mentioned conventional cold drawing method, when the restriction on equipment or the wall thickness / diameter of the pipe is large and the pulling stress cannot be sufficiently obtained and the reduction ratio has to be reduced, the processing bite (: Since the stress of the pipe is a tensile force in the gap between the plug and the inner surface of the die hole, the contact between the die and the pipe and between the drawn plug and the pipe becomes insufficient, and the inner and outer surfaces of the pipe become insufficiently smooth. Irregularities are likely to remain. Therefore, the diameter of the tube is reduced by cold drawing to improve the contact between the inner and outer surfaces of the tube, the plug, and the die in the working bite. However, when the pipe is cold-drawn by using a die, irregularities occur on the inner surface of the pipe, and the roughness due to the irregularities increases as the diameter reduction rate of the pipe increases. As a result, it is difficult to obtain a pipe with high dimensional accuracy by the cold drawing method, and the fatigue strength of the pipe is not sufficient. Therefore, a pipe with better dimensional accuracy and fatigue strength has been strongly demanded.
[0007]
Further, in the above-mentioned conventional cold drawing method, even if the diameter reduction ratio can be increased due to the facility capability, the processing distortion due to the diameter reduction is increased, and the pipe is easily worked and hardened. The pipe is subjected to further processing such as bending and swaging after drawing.However, since the work hardening at the time of drawing tends to cause cracks, which is problematic, it is necessary to apply heat treatment at a high temperature for a sufficient time after drawing. Because of this, the production cost becomes extremely large, and there has been a demand for an inexpensive and easy-to-process pipe with high dimensional accuracy.
[0008]
Further, in the manufacturing technology described in Patent Documents 1 to 3, as a result of dividing the die of the rotary forging machine and moving the die back, a step is easily generated in the divided portion, and smoothing of the outer surface is insufficient, Or, uneven deformation may occur due to the different stiffness of the dies in the circumferential direction.Thus, the wall thickness accuracy is insufficient, so that the target finish dimensional accuracy cannot be sufficiently obtained, and the fatigue strength of the steel pipe is not sufficient. No further improvement was required.
[0009]
Further, in the manufacturing techniques described in Patent Documents 1 to 3, the wall thickness after pushing the steel pipe is thicker than the wall thickness before pushing. This is a limitation due to the use of a rotary forging machine, which has a complicated structure and is difficult to apply a load, and as a result, irregularities are easily generated on the inner surface of the tube, making it difficult to smooth the tube. I have. As a result, in order to obtain a desired thickness after the pressing, the only option is to reduce the thickness before the pressing. Therefore, in order to prepare pipes of various product sizes and improve the performance such as the fatigue strength of those pipes, it is necessary to prepare many pipe sizes. However, it was difficult to obtain good dimensions over the entire required size of the pipe, because there were restrictions on the raw pipe manufacturing equipment and many sizes could not be prepared. To increase the wall thickness, the gap is increased on the side closer to the outlet in the machining tool to make the tube easier to deform. When the wall thickness is further increased, the gap becomes larger, making it difficult for the tube to sufficiently contact the die surface or plug surface.As a result, the surface of the tube does not progress smoothly, and it is difficult to obtain a tube with high dimensional accuracy. Had disadvantages.
[0010]
In view of the above demands and difficulties, an object of the present invention is to provide a high-dimensional precision pipe having sufficient fatigue strength, which can be manufactured at low cost over a wide range of required sizes of pipes, and a method of manufacturing the same. .
[0011]
[Means for Solving the Problems]
The present invention that has achieved the above object is a high-dimensional precision pipe having the following gist configuration, and a method of manufacturing the high-dimensional precision pipe.
(1) Any one of an outer diameter deviation, an inner diameter deviation, and a circumferential thickness deviation manufactured by performing a punching operation in which a metal tube is pushed through a hole of a die while a plug is inserted in the tube. A high dimensional precision pipe as punched, characterized in that one or two or more are 3.0% or less.
[0012]
(2) A metal tube is pressed into a hole of a die while a plug is inserted into the tube, and the metal tube is pressed and passed to make the metal tube on the exit side of the die have a thickness smaller than that of the entrance side. A high-precision tube as-punched, wherein at least one of outer diameter deviation, inner diameter deviation, and circumferential thickness deviation is not more than 3.0.
[0013]
(3) The method according to (1) or (2), wherein the punching is performed while the metal tube is circumscribed entirely around the plug and entirely around the die within the same cross section of the tube. High dimensional precision tube.
(4) The high dimensional precision tube according to any one of (1) to (3), wherein the die is an integrated die and / or a fixed die.
[0014]
(5) A method of manufacturing a high dimensional precision tube, wherein a metal tube is subjected to a punching operation in which a plug is inserted into the tube and the metal tube is pushed into a hole of a die and passed therethrough.
(6) The method for manufacturing a high-dimensional precision pipe according to (5), wherein the thickness of the pipe on the outlet side of the die is equal to or less than the thickness of the pipe on the inlet side.
(7) The method according to (5) or (6), wherein the punching is performed while the metal pipe is circumscribed around the plug and the die all around the same cross section of the pipe. Manufacturing method of high dimensional accuracy pipe.
[0015]
(8) The method according to any one of (5) to (7), wherein the die is an integrated die and / or a fixed die.
(9) The method according to any one of (5) to (8), wherein the plug is a floating plug.
In the present invention, the upper limit of the outer diameter deviation, the inner diameter deviation and the circumferential thickness deviation is preferably 1.0%, more preferably 0.5%.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Conventionally, when a metal tube is drawn using a die and a plug, it is difficult to improve the dimensional accuracy of the tube because of the drawing, the die and the tube outer surface in the machining tool, and the plug and the tube inner surface. From insufficient contact. That is, as shown in FIG. 2, by inserting the plug 1 into the pipe (metal pipe) 5 and pulling out the pipe 5 from the hole of the die 2, the pulling force 9 applied on the exit side of the die 2 causes Tension is generated inside the machining tool, and irregularities are generated and increased on the inner and outer surfaces of the pipe from the entrance to the machining tool toward the exit side. On the inlet side in the machining tool, the inner surface of the tube deforms along the plug 1 so that the outer surface of the tube does not contact or only slightly contacts. The inner surface of the tube does not touch or only slightly touches because of deformation due to contact. For this reason, the inner and outer surfaces of the tube had free deformation portions, and the unevenness could not be sufficiently smoothed, and the dimensional accuracy of the tube obtained after drawing was low.
[0017]
On the other hand, in the case of the punching used in the present invention, as shown in FIG. 1, the plug 1 is inserted into the tube 5 and the tube 5 is pushed into the hole of the die 2 and passed therethrough. Due to the pushing force 8 applied on the entry side of the die 2, a compressive stress acts on the entire inside of the working tool. As a result, the pipe 5 can make sufficient contact with the plug 1 and the die 2 in the same cross section over the entire area in the circumferential direction, regardless of the entry side or the exit side of the machining tool. Moreover, even with a small diameter reduction ratio, the inside of the working bite is subjected to compressive stress, so that the pipe and the plug, the pipe and the die can easily come into full contact in the entire circumferential direction within the same cross section as compared with drawing. Therefore, the tube is easily smoothed, and a tube with high dimensional accuracy can be obtained.
[0018]
As a result, when comparing the fatigue strength of these pipes, a pipe manufactured by punching can obtain a target sufficient fatigue strength as compared with a pipe manufactured by conventional drawing. Also, in the case of extrusion, even if the diameter reduction ratio is small, the inner and outer surfaces of the pipe can be smoothed, so that the processing distortion does not increase as compared with the case of drawing, so the heat treatment load after diameter reduction is light, and the manufacturing cost is low. Lower.
[0019]
In addition, in the press-in using the conventional rotary forging machine 3 shown in FIG. 3, the integrated die is processed by returning the die 10 using the divided dies 4 which are divided in the circumferential direction. Although the wall thickness accuracy could not be sufficiently improved, in the present invention, such a step did not occur at all, and as a result, the inner and outer surfaces of the pipe could be smoothed to obtain sufficient fatigue strength. Can be. In the present invention, for example, a step may be eliminated as an integrated die, or a step due to backward rotation may be prevented as a fixed die. Of course, the die may be formed as an integral and fixed die to prevent the step.
[0020]
Furthermore, in the present invention, the apparatus structure can be simplified as compared with the method of moving the die back using a conventional rotary forging machine, and a sufficient load can be applied to the processing, and the die entrance side It is possible to process enough even if the load on the outlet side is made equal to or less than the thickness of A tube with sufficient strength can be obtained.
[0021]
Conventionally, as a method of reducing the outer diameter deviation, the inner diameter deviation, and the circumferential thickness deviation of a metal pipe to 3.0% or less, a method by machining (processing involving partial removal of material) is known. The cost was high, the work efficiency was poor, and it was difficult to process a long, small-diameter metal tube. Therefore, it is difficult to apply it to a drive shaft of an automobile part.
[0022]
As a method for distinguishing the machined metal tube from the present metal tube (as-extruded metal tube according to the present invention), black scale is formed on the surface of the present metal tube by heating, rolling, or the like in a pre-production process. In contrast to the adherence, the machined one has the black scale removed, so that a method of observing the condition of the tube surface can be mentioned, and this method can be used for identification.
[0023]
Further, the present metal pipe has a wall thickness deviation several times better than that manufactured by a method in which a steel pipe is pressed into a die using a conventional rotary forging machine (see, for example, Patent Documents 1, 2, and 3). ing. That is, in the past, no steel pipe was obtained in which any one or more of the outer diameter deviation, the inner diameter deviation, and the thickness deviation in the circumferential direction was 3.0% or less while being punched.
[0024]
In the present invention, the outer diameter deviation, the inner diameter deviation, and the circumferential thickness deviation, which are used as indices of the dimensional accuracy, are obtained as follows.
The outer diameter (or inner diameter) deviation is calculated from the circumferential distribution data of the outer diameter (or inner diameter) measured by rotating the tube with a micrometer in contact with the outer surface (or inner surface) of the tube, from the target outer diameter (or target). Calculated as the maximum deviation from the inner diameter, or from the circumferential distribution data of the distance between the tube and the laser oscillation source measured by applying laser light to the outer surface (or inner surface) of the tube, the target outer diameter (or target inner diameter) Is calculated as the maximum deviation from. Alternatively, the outer diameter (or inner diameter) deviation may be calculated by image analysis of a cross section in the circumferential direction of the pipe and calculating a deviation from a perfect circle in the circumferential direction.
[0025]
The circumferential thickness deviation is calculated as the difference between the circumferential distribution data of the outer diameter and the circumferential distribution data of the inner diameter, or the circumferential cross section of the pipe is image-analyzed and the thickness cross section is calculated. Is directly measured as the maximum deviation from the target image thickness from the image of FIG.
The measurement is performed at an arbitrary position excluding 150 mm from the front and rear ends of the pipe at a pitch of 10 mm or less, and is determined from the values of 10 or more measurement points.
[0026]
That is, the outer diameter deviation, the inner diameter deviation, and the thickness deviation (= circumferential thickness deviation) are defined as follows.
Outer diameter deviation: (MAX outer diameter-MIN outer diameter) / Target outer diameter (or average outer diameter) x 100 (%)
Inner diameter deviation: (MAX inner diameter-MIN inner diameter) / target inner diameter (or average inner diameter) x 100 (%)
Wall thickness deviation: (MAX wall thickness-MIN wall thickness) / Target wall thickness (or average wall thickness) x 100 (%)
Since the high dimensional accuracy pipe of the present invention is a metal pipe in which one or more of the three dimensional accuracy indicators is 3.0% or less, it is used for automobiles requiring high dimensional accuracy of 3.0% or less. It can be used as a metal tube for drive system parts and the like.
[0027]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
In Example 1, a steel pipe having an outer diameter of 40 mm and a wall thickness of 6 mm was subjected to a punching process in the form shown in FIG. Here, a plug having a mirror-finished surface to be brought into contact with the inner surface of the tube and a dice which is an integrated fixed die and having a mirror-finished surface to be brought into contact with the outer surface of the tube were used. The plug was inserted into the tube with one end fixed. The processing conditions were as follows: Outlet thickness = Inlet thickness, diameter reduction ratio = 10%.
[0028]
In Example 2, processing was performed in the same manner as in Example 1, except that the diameter reduction rate was 5%.
In Example 3, processing was performed in the same manner as in Example 2, except that the plug was floated.
Further, as Comparative Example 1, the same procedure as in Example 2 was carried out except that in Example 2, the drawing shown in FIG. 1 was used instead of the drawing shown in FIG. 1, and the outlet plate thickness was smaller than the inlet plate thickness. Processing.
[0029]
Further, as Comparative Example 2, instead of the integral fixed die in Example 2, a split die having the form shown in FIG. 3 was incorporated into a rotary forging machine and used in a backward movement, and the punching was performed instead of the punching. Processing was performed in the same manner as in the example except for the above.
Further, as Comparative Example 3, the processing was performed in the same manner as in Comparative Example 2, except that the processing conditions were set such that the outgoing side wall thickness = the incoming side wall thickness + 1 mm (= 7 mm).
[0030]
The three-dimensional accuracy index was determined for these steel pipes after diameter reduction processing, and the steel pipes were subjected to a fatigue test. Table 1 shows the results.
The outer diameter and inner diameter deviations shown in Table 1 were obtained by measurement using the laser light, and the circumferential thickness deviations in the same table were obtained from the difference in the circumferential distribution of these measurement data.
[0031]
As shown in FIG. 4, the endurance limit number of the fatigue test shown in Table 1 is obtained by changing the stress level variously in a test for obtaining the number of repetitions (namely, the endurance number) until a crack is generated while keeping the stress constant. In the graph of the relationship between stress and the number of times of endurance, the number of endurances at the inflection point at which the stress starts to decrease and becomes substantially constant as the number of times of endurance increases, the larger the value, the better the fatigue strength. That is, in the case of this example, the number of times of endurance at a stress of about 150 MPa.
[0032]
[Table 1]

[0033]
From Table 1, the product pipes of Examples 1 to 3 had remarkably good dimensional accuracy and the best fatigue strength. Particularly, when the plug was floated, the dimensional accuracy was even better (Example 3). On the other hand, in the conventional drawing, the dimensional accuracy of the product pipe was reduced, and as a result, the fatigue strength was also significantly reduced (Comparative Example 1). The dimensional accuracy of the product tube was reduced even by pushing using a rotary forging machine (Comparative Example 2), and further increasing the wall thickness (Comparative Example 3), and sufficient fatigue strength could not be obtained.
[0034]
【The invention's effect】
The high dimensional accuracy pipe of the present invention has remarkably good dimensional accuracy and, as a result, has good fatigue strength, and can be manufactured at low cost. It has an excellent effect of contributing to Further, according to the manufacturing method of the present invention, there is an excellent effect that a metal pipe having extremely good dimensional accuracy over a wide range of required pipe sizes can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of punching used in the present invention.
FIG. 2 is an explanatory view showing a conventional drawing embodiment.
FIGS. 3A and 3B are explanatory views showing an embodiment of pushing by a rotary forging machine in which a conventional split die is mounted and moved backward, in which FIG. 3A is a cross-sectional view including a pipe center axis, and FIG. It is an AA arrow line view.
FIG. 4 is a characteristic diagram showing a relationship between stress in a fatigue test and the number of times of endurance.
[Explanation of symbols]
1 Plug 2 Dice (Example: One-piece fixed die)
3 Rotary forging machine 4 Split die 5 Tube (metal tube, steel tube)
6 Pipe pusher 7 Pipe puller 8 Push-in force 9 Pull-out force 10 Return

Claims (9)

Any one or two of an outer diameter deviation, an inner diameter deviation, and a circumferential thickness deviation manufactured by performing a punching operation in which a metal tube is pressed into a hole of a die with a plug inserted into the tube and passed therethrough. The high-precision pipe as punched, characterized in that the above is 3.0% or less. The metal pipe was manufactured by pressing the metal pipe into the hole of the die while inserting a plug into the pipe, performing punching, and making the thickness of the metal pipe on the exit side of the die smaller than that on the entry side. A high-precision pipe as punched out, characterized in that at least one or more of the deviation of the outer diameter, the deviation of the inner diameter and the deviation of the wall thickness in the circumferential direction is not more than 3.0%. The high-precision pipe according to claim 1 or 2, wherein the punching is performed while the metal pipe is in full contact with the plug and the die in the same cross section of the pipe. The high dimensional precision tube according to any one of claims 1 to 3, wherein the die is an integrated die and / or a fixed die. A method of manufacturing a high-precision pipe, wherein a metal pipe is subjected to a punching operation in which a plug is inserted into the pipe and the metal pipe is pressed into and passed through a hole of a die. The method according to claim 5, wherein the thickness of the pipe on the exit side of the die is equal to or less than the thickness of the pipe on the entry side. 7. The high dimensional precision tube according to claim 5, wherein the punching is performed while the metal tube is circumscribed entirely around the plug and entirely around the die in the same cross section of the tube. Production method. The method according to any one of claims 5 to 7, wherein the die is an integrated die and / or a fixed die. 9. The method according to claim 5, wherein the plug is a floating plug.

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