JP2005028451A - Method for manufacturing tube with high dimensional accuracy having good surface quality - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a tube with high dimensional accuracy having good surface quality, which can produce a tube having good surface quality and remarkably higher dimensional accuracy than ever. <P>SOLUTION: A lubricant film is formed on the inner face and/or the outer face of the tube 4. Then a plug 1 is inserted into the tube and the tube is punched by a die 2. The tube may be a steel tube on which oxidized scale remains. It is desirable to use, as a lubricant for forming the lubricant film, any of a liquid lubricant, a grease lubricant, and a drying resin lubricant (drying resin or a solution of the drying resin diluted with a solvent or an emulsion of the drying resin). In the case of using the drying resin lubricant, it is preferable to dry the drying resin lubricant with hot air after applied to the tube. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a high dimensional accuracy tube with good surface quality, and in particular, manufactures a tube that requires high dimensional accuracy, such as an automobile drive system component, so that the surface quality is good. On how to do.

  For example, metal pipes such as steel pipes (hereinafter also simply referred to as pipes) are roughly classified into welded pipes and seamless pipes. Welded pipes are manufactured by rounding the width of the strip and welding by welding both ends of the rounded width, such as ERW steel pipes, while seamless pipes are used to drill a mass of material at high temperatures. It is manufactured by a method of rolling with a mandrel mill afterwards. 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 thickness deviation exceeds 3.0%. In the case of a seamless pipe, it is easy to be eccentric in the drilling process, and a large thickness deviation is likely to occur due to the eccentricity. Efforts are made to reduce this thickness deviation in a subsequent process, but it cannot be sufficiently reduced, and remains at 8.0% or more at the product stage.

Pipes used for automobile drive system parts and the like are required to have a high dimensional accuracy of 3.0% or less, more strictly 1.0% or less, as deviations in thickness, inner diameter, and outer diameter. Therefore, as a means for improving the accuracy of the wall thickness, inner diameter, and outer diameter of the pipe, conventionally, as shown in FIG. A manufacturing method (so-called cold check method) that is used and pulled out cold is used (see, for example, Patent Document 1). In recent years, as shown in FIG. 3, the divided die 8 divided in the circumferential direction is swung (returned) 12 by a rotary forging machine 9, and the tube 4 is pushed into the die hole of the divided die 8 to be processed. A manufacturing technique (hereinafter referred to as a rotary forging indentation method) has been proposed (see Patent Documents 2, 3, and 4).
Japanese Patent No. 2812151 Japanese Patent Laid-Open No. 9-262637 Japanese Patent Laid-Open No. 9-262619 Japanese Patent Laid-Open No. 10-15612

  However, in the above-described cold check method, when the drawing stress is not sufficiently obtained due to restrictions on equipment and the pipe thickness / diameter is large, etc., it is necessary to reduce the diameter reduction rate. Since the stress of the tube within the gap between the die and the inner surface of the die hole is a tensile stress, the contact between the die and the outer surface of the tube and between the drawing plug and the inner surface of the tube is insufficient, and the inner surface of the tube and the outer surface of the tube are insufficiently smoothed. And unevenness tends to remain. For this reason, in the cold check method, it is attempted to increase the diameter reduction ratio of the pipe so that the contact between the inner and outer faces of the pipe and the plug and the die is sufficient in the machining tool. However, when the tube is pulled out using a die, unevenness is generated on the inner surface of the tube, and the roughness due to the unevenness increases as the diameter reduction ratio of the tube increases. As a result, it has been difficult to obtain a tube with high dimensional accuracy by the cold check method, and a tube with better dimensional accuracy has been strongly demanded.

  Further, in the rotary forging push-in method shown in Patent Documents 2 to 4 and the like, since the dividing die 8 is used while being swung, a step is easily generated in the divided portion, and the smoothing of the outer surface of the pipe is insufficient. Alternatively, the finished dimensional accuracy cannot be sufficiently obtained due to the rigidity of the divided dies different in the circumferential direction, and further improvement has been demanded. Moreover, in this rotary forging push-in method, the thickness after pushing the pipe is thicker than the thickness before pushing. This is due to the limitations of using a rotary forging machine that has a complicated structure and is difficult to apply a load, and as a result, irregularities are likely to occur on the inner surface of the pipe, and the pipe is smoothed. It is difficult to do. In order to increase the wall thickness, the gap is increased as it goes to the exit side in the machining tool, making it easier to deform the tube, but if there is a gap and deformation is easier, the tube will be on the surface of the die or plug. As a result, it was difficult to make sufficient contact, and as a result, smoothing of the inner and outer surfaces of the tube did not progress, and it was difficult to obtain a high dimensional accuracy tube.

  Also, when manufacturing a high dimensional accuracy tube, if the frictional force between the outer surface of the plug and the inner surface of the tube, the inner surface of the die and the outer surface of the tube is not reduced as much as possible, seizure such as seizure occurs on the tube surface during processing. The surface quality of the tube after processing deteriorates, the tube does not become a product, and the load during processing may increase significantly, making the processing itself impossible, resulting in a significant reduction in production efficiency. It was.

  As described above, in the conventional cold check method and rotary forging indentation method, it has been difficult to obtain a pipe with high dimensional accuracy, and the problem that the surface quality of the pipe may be deteriorated remains unsolved. In order to solve these problems, the present invention provides a high dimensional accuracy tube with good surface quality, which can obtain a tube with good surface quality and much higher dimensional accuracy than before, and can manufacture the tube efficiently. It aims at providing the manufacturing method of.

  The present invention provides a high dimensional accuracy tube with good surface quality, characterized in that after forming a lubricating coating on the inner surface and / or outer surface of the tube, a plug is inserted into the tube and the tube is pushed out with a die. It is a manufacturing method. In the present invention, it is preferable to continuously feed the pipe while the plug inserted in the pipe is floating, and to push out the pipe with a die. In the present invention, the tube on which the lubricating coating is formed may be a steel tube with an oxide scale attached. The lubricant used to form the lubricating coating includes a liquid lubricant, a grease-based lubricant, a drying resin-based lubricant (that is, a drying resin, or a solution obtained by diluting the drying resin with a solvent, Alternatively, any of the drying resin emulsions) can be preferably used. As a method for forming a lubricating coating in the case of using a drying resin-based lubricant, a method of applying this to a pipe and then drying it by applying it to hot air or drying it by air is preferable.

Moreover, it is preferable that the lubricant to be used is applied by any one or more of the following methods to form a lubricant film.
F1) It sprays and apply | coats to a pipe | tube from the front-end | tip and / or back end of a pipe | tube at the die entrance side.
F2) Apply through a tube while spraying on the die entry side.
F3) Dry the coating film by passing hot air through the tube after applying F1 or F2.
F4) Preheat tube before application of F1 or F2.
F5) The tube is heated upstream of the step of forming the lubricating coating or processed after the heating, and the tube is conveyed to the step of forming the lubricating coating while maintaining a high temperature.

  In the present invention, the step of inserting the plug into the pipe can be omitted.

  According to the present invention, it is possible to finish the tube with extremely good dimensional accuracy efficiently without deteriorating the surface quality.

  Hereinafter, embodiments and operations of the present invention will be described in comparison with the prior art.

  Conventionally, when a pipe is pulled out using a die and a plug, it is difficult to improve the dimensional accuracy of the pipe. This is due to the fact that is insufficient. That is, as shown in FIG. 2, by inserting the plug 5 into the tube 4 and pulling out the tube 4 from the die 6, the cutting tool 10 is pulled by the pulling force 10 applied by the tube drawing machine 7 on the exit side of the die 6. A tension (tensile stress) is generated inside. Since the inner surface of the tube is deformed along the plug 5 on the entry side in the processing tool, the outer surface of the tube does not contact the die 6 or only slightly, and on the exit side in the processing tool, the die 6 is contacted. Since the outer surface of the tube contacts and deforms, the inner surface of the tube does not contact the plug 5 or only slightly contacts. For this reason, both the outer surface of the tube and the inner surface of the tube have free deformation portions in the working bite, and the unevenness cannot be sufficiently smoothed, and only a tube with insufficient dimensional accuracy has been obtained after drawing.

  In contrast, in the case of punching according to the present invention, as shown in FIG. 1, the plug 1 is inserted into the tube 4, and the pushing force 11 is applied to the tube 4 by the tube pusher 3 from the entry side of the die 2. In addition, the tube 4 is fed into the die 2. Therefore, the compressive stress acts on the entire area of the pipe in the machining tool. As a result, the tube 4 can sufficiently contact the plug 1 and the die 2 regardless of the entry side or the exit side in the machining tool. In addition, even in the case of a small diameter reduction ratio, since the processing bite is in a compressive stress state, the tube and the plug, the tube and the die are more easily contacted than the drawing, and the tube is easily smoothed. A tube with high dimensional accuracy is obtained. Here, from the viewpoint of productivity, it is preferable to continuously feed the tube 4 into the die 2 while floating the plug 1 in the tube 4.

  Further, in the conventional rotary forging push-in method shown in FIG. 3, since the divided die 8 is used by swinging (returning) 12, the step is different depending on the step due to the divided portion or in the circumferential direction under high stress. The thickness accuracy could not be made sufficiently good due to the non-uniform deformation due to the rigidity of the steel sheet.

  Compared to this, in the punching of the present invention, the die may be a single piece and does not need to be swung, so non-uniform deformation does not occur, and as a result, both the inner surface of the tube and the outer surface of the tube can be smoothed. .

  When manufacturing high dimensional accuracy pipes, lubrication between the outer surface of the plug and the inner surface of the pipe and between the inner surface of the die and the outer surface of the pipe will not cause seizure such as seizure on the pipe surface during processing. Can be manufactured. Furthermore, since the frictional force is reduced by lubrication, the load required for machining can be reduced, machining energy can be saved, and the production efficiency can be improved.

  Therefore, the inventors examined various lubrication methods, and as a result, found that the following method is good and made it a requirement of the present invention. That is, it is preferable to perform the punching by previously forming a lubricating coating on one or both of the inner surface and the outer surface of the tube. Lubricants used for forming the lubricant film include liquid lubricants, grease-based lubricants, and dry resin-based lubricants (that is, a dry resin, a solution obtained by diluting the dry resin with a solvent, or the dry resin). Are preferred. Examples of liquid lubricants include mineral oils, synthetic esters, animal and vegetable oils and fats, and additives mixed with these. Examples of the grease-based lubricant include Li-based grease lubricant, Na-based grease lubricant, and those containing additives such as molybdenum disulfide. Examples of the drying resin include polyacrylic resins, epoxy resins, polyvinyl resins, and polyester resins. Examples of the solvent for diluting the drying resin include ethers, ketones, aromatic hydrocarbons, linear / side chain hydrocarbons, and the like. Examples of the dispersion medium for obtaining the emulsion of the drying resin include water, alcohols, and a mixture thereof. As a method for forming a lubricating coating using the drying resin lubricant, a method of applying the coating to a tube and applying it to hot air to dry, or air drying is preferable.

  The hot air means hot air or hot air, the hot air means an air flow above room temperature and below 100 ° C., and the hot air means an air flow above 100 ° C.

Examples of a method for efficiently forming a lubricant film using these lubricants include a method in which the lubricant to be used is applied by any one or more of the following methods to form a lubricant film.
F1) It sprays and apply | coats to a pipe | tube from the front-end | tip and / or back end of a pipe | tube at the die entrance side.
F2) Apply through a tube while spraying on the die entry side.
F3) Dry the coating film by passing hot air through the tube after applying F1 or F2.
F4) Preheat tube before application of F1 or F2.
F5) The tube is heated upstream of the step of forming the lubricating coating or processed after the heating, and the tube is conveyed to the step of forming the lubricating coating while maintaining a high temperature.

  In order to produce high-precision pipes more efficiently, it is better to process ERW welded pipes that are hot-rolled steel sheets as they are, or seamless steel pipes that are heated in a furnace without removing the oxide scale. And if it does so, processing cost can be reduced.

  When manufacturing pipes that only require outer diameter accuracy, if plugging is omitted and the punching is performed, the manufacturing time is shortened by the amount that the plug loading and unloading process is eliminated, and the production is more efficient. This is preferable.

[Comparative Example 1] A 40 mm × 6.0 mmt × 5.5 mmL ERW steel pipe with a hot-rolled scale attached to the surface was processed under the following condition A by punching shown in FIG.
(Condition A) Plug: A mirror surface plug is inserted into a steel pipe and floated.

Dice: Integrated fixed die
Reduction ratio: 5%
Steel pipe wall thickness on the die exit side: 6.0 mmt (= input wall thickness)
[Invention Example 1] The above steel pipe was coated with a liquid lubricant (mineral oil) on both the inner and outer surfaces by the method F1 (from the tip) to form a lubricating film, and then processed in the same manner as in Comparative Example 1. .
[Invention Example 2] Apply a grease lubricant (Li grease grease added with molybdenum disulfide) on both the inner and outer surfaces of the above steel pipe by the method F1 (from the rear end) and apply a lubricating coating. After forming, the same processing as in Comparative Example 1 was performed.
[Invention Example 3] The above steel pipe is coated with a drying resin (polyalkyl resin) on both the inner and outer surfaces by the method F1 (from the tip) and dried by applying hot air (about 200 ° C) to form a lubricating coating. After forming, the same processing as in Comparative Example 1 was performed.
[Invention Example 4] A solution obtained by diluting a drying resin (polyalkyl resin) with a solvent (acetone) on both the inner and outer surfaces of the steel pipe was applied by the method of F1 (from the tip) and warm air (about 50). C.) and dried to form a lubricating film, and then processed in the same manner as in Comparative Example 1.
[Invention Example 5] An emulsion in which a drying resin (polyalkyl resin) is dispersed in a dispersion medium (water) on both the inner and outer surfaces of the steel pipe is applied by the method of F1 (from the tip) and hot air ( (Approx. 70 ° C.) and dried to form a lubricating coating, which was then processed in the same manner as in Comparative Example 1.
[Comparative Example 2] After applying the same liquid lubricant as in Invention Example 1 on the inner and outer surfaces of the above steel pipe by the same method to form a lubricating film, the following condition B was applied by the cooling method shown in FIG. It was processed with.
(Condition B) Plug, die, diameter reduction ratio: same as Condition A
Steel pipe wall thickness on the die exit side: 5.5mmt (<Inside wall thickness)
[Comparative Example 3] After applying the same liquid lubricant as that of Invention Example 1 on both the inner and outer surfaces of the above steel pipe by the same method to form a lubricating film, the following conditions were obtained by the rotary forging indentation method shown in FIG. Processed with C.

(Condition C) Plug: Same as Condition A
Dice: Divided dice
Reduction ratio: Same as condition A
Steel pipe wall thickness on the die exit side: 7.0 mmt (> input wall thickness)
Table 1 shows the results of measuring the surface flaw state and dimensional accuracy (outer diameter deviation, inner diameter deviation, wall thickness deviation) of the steel pipes manufactured by the methods of these examples. The outer diameter deviation and the inner diameter deviation are obtained by image analysis of the circumferential section of the tube, and the maximum deviation from the perfect circle (ie, (maximum diameter−minimum diameter) / true circle diameter × 100%) Obtained by calculating. Further, the thickness deviation is obtained by image analysis of the circumferential cross section of the tube, and the maximum deviation with respect to the average thickness from the image of the thickness cross section (that is, (maximum thickness−minimum thickness) / average thickness × 100%). As measured directly.

  According to Table 1, in all of the examples of the present invention that were punched out under lubrication, no flaws were generated on the surface of the steel pipe after processing, good surface quality was obtained, and dimensional accuracy was remarkably good. . On the other hand, in Comparative Example 1 in which punching was performed without lubrication, wrinkles were generated on the surface of the steel pipe after processing. In Comparative Example 2 in which processing by the cold check method was performed under lubrication, the dimensional accuracy was lowered. In Comparative Example 3 in which processing by the rotary forging indentation method was performed under lubrication, the dimensional accuracy was further lowered.

  Film formation conditions shown in Table 2 using the same steel pipe as in Comparative Example 1 and liquid lubricant (synthetic ester), grease lubricant (Na grease lubricant added with molybdenum disulfide) or drying resin emulsion After forming a lubricating film by applying the above, the punching shown in FIG. 1 was carried out under the condition A (however, plug insertion was omitted for some parts) to obtain inventive examples 6-10.

  The obtained tube was investigated in the same manner as in Example 1, and the processing efficiency was investigated for each film forming condition. The results are shown in Table 2. The processing efficiency was indicated by the relative value of the number of processing per hour (ratio to Comparative Example 1). According to the present invention, it can be seen that a high dimensional accuracy tube having no surface flaws can be obtained with a machining efficiency 9 times or more higher than that of Comparative Example 1 without lubrication.

  In the above embodiments, the case of so-called double-sided lubrication in which a lubricating coating is formed on both the inner and outer sides of the pipe has been shown, but the present invention is not limited to this, and the lubricating coating is formed on either the inner surface or the outer surface. It also includes the case of so-called single-side lubrication, and it is clear that wrinkles can be effectively prevented from occurring on the surface on which the lubricating film is formed even in this single-side lubrication.

  The present invention can be used in a process of finishing a pipe with high dimensional accuracy.

It is a longitudinal cross-sectional view which shows the outline | summary of the punch used by this invention. It is a longitudinal cross-sectional view which shows the outline | summary of the conventional cold check method. It is the longitudinal cross-sectional view (a) which shows the outline | summary of the conventional rotary forge pushing method, and its AA arrow directional view (b).

Explanation of symbols

1 plug 2 dice (integrated fixed die)
3 Tube pusher 4 Tube (metal tube, steel tube)
5 Plug 6 Die 7 Pipe puller 8 Divided die 9 Rotary forging machine 10 Pulling force 11 Pushing force 12 Swing (return)

Claims (12)

  A method for producing a high dimensional accuracy tube with good surface quality, comprising forming a lubricating film on the inner surface and / or outer surface of a tube, inserting a plug into the tube, and punching the tube with a die.   After forming a lubrication film on the inner surface and / or outer surface of the tube, the tube is continuously fed into the tube and floated, and the tube is continuously fed to push the tube with a die. A manufacturing method of a good high dimensional accuracy tube.   The method for producing a high dimensional accuracy tube with good surface quality according to claim 1 or 2, wherein the tube for forming the lubricating coating is a steel tube with oxide scales still attached.   The method for producing a high dimensional accuracy tube with good surface quality according to any one of claims 1 to 3, wherein the lubricant film is formed using a liquid lubricant or a grease-based lubricant.   4. The lubricating coating is formed using a drying resin lubricant, that is, a drying resin, a solution obtained by diluting a drying resin with a solvent, or an emulsion of the drying resin. The manufacturing method of the high dimensional accuracy pipe | tube with favorable surface quality in any one of.   6. The production of a high dimensional accuracy tube with good surface quality according to claim 5, wherein the dry resin-based lubricant is applied to the tube and then applied to hot air or air dried to form the lubricating coating. Method.   6. The method for producing a high dimensional accuracy pipe with good surface quality according to claim 4, wherein the lubricant to be used is sprayed and applied to the pipe from the front end and / or rear end of the pipe on the die entrance side.   6. The method for producing a high dimensional accuracy tube with good surface quality according to claim 4, wherein the lubricant to be used is applied through the tube while being sprayed on the die entrance side.   9. The method for producing a high-dimensional accuracy tube with good surface quality according to claim 7, wherein the coating film is dried by passing hot air through the tube after the application.   The method for manufacturing a high-dimensional accuracy tube with good surface quality according to any one of claims 7 to 9, wherein the tube is preheated before the application.   The tube is heated or processed after heating upstream of the step of forming the lubricating coating, and the tube is conveyed to the step of forming the lubricating coating at a high temperature. The manufacturing method of the high dimensional accuracy pipe | tube with favorable surface quality of description.   The method for manufacturing a high-dimensional accuracy pipe with good surface quality according to any one of claims 1 to 11, wherein a step of inserting the plug into the pipe is omitted.

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