JP2005125377A - Method for manufacturing drawn tube having excellent surface quality - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a drawn tube having excellent surface quality with high efficiency and at a low cost. <P>SOLUTION: When a tube is drawn by a die 2 by forming a lubrication film on an outer surface and/or an outer surface of the tube, the lubrication film is formed by using raw lubrication material consisting of dry resin or this dry resin as a base with other lubricant added thereto. The lubrication film may be formed by applying solution in which the raw lubrication material is dissolved in solvent, and emulsion with the raw material dispersed in dispersant to the tube, and drying the solution or the emulsion. Sufficient lubrication effect can be obtained even by forming the lubrication film on a steel tube with oxide scale deposited thereon. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a drawn pipe having a good surface quality, and more specifically, a pipe having a high dimensional accuracy and a good surface quality, such as an automotive drive system component filling pipe, is produced by drawing. In this case, the present invention relates to a method of manufacturing a drawn tube having a good surface quality, which can obtain a sufficient lubricating effect with a simple process and can be pulled out with high efficiency.

  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 the thickness deviation is reduced in the subsequent process, but the thickness deviation in the product stage is usually 8.0% or more. .

  Pipes used for automobile parts and the like are required to have a high dimensional accuracy of 3.0% or less, more strictly 1.0% or less in terms of deviations in thickness, inner diameter, and outer diameter. In order to meet this requirement, generally, as shown in FIG. 1, for example, as shown in FIG. 1, after forming a metal pipe (both a welded pipe and a seamless pipe), the pipe is pulled out cold using the die 2 or the die 2 and the plug 1. A manufacturing method (a so-called cold check method) is employed.

  However, with the conventional cold check method described above, the machining tool (plug) is used when the restriction on the equipment and the thickness and diameter of the pipe are large and the pulling force is not sufficient to reduce the diameter reduction rate. Because the tensile stress acts on the pipe within the gap between the die and the inner surface of the die hole, the contact between the die and the pipe, and the plug for extraction and the pipe is insufficient, and the inner and outer surfaces of the pipe are not smoothed, leaving irregularities. Cheap. Therefore, the diameter reduction rate of the pipe is increased to improve the contact between the inner and outer surfaces of the pipe, the plug, and the die within the machining tool. However, when the diameter reduction ratio is increased, the die or plug and the tube are seized, resulting in frequent wrinkles on the pulled tube, and the surface quality of the tube after processing deteriorates. In some cases, the load increases significantly, making the machining itself impossible, and as a result, the production efficiency of the pipe is significantly reduced.

Therefore, a measure is taken to preliminarily lubricate the pipe before drawing to form a sufficient lubricating film. As such a lubricating treatment, a liquid lubricant is injected at a high pressure as shown in Patent Document 1. In other cases, the inner and outer surfaces of the tube are bonded and further coated with metal soap.
JP-A-4-313418

  However, the conventional lubrication treatment requires acid cleaning of the surface of the tube to remove the oxide scale, and it is necessary to immerse the tube in a lubricant tank for a long time to form a lubricating coating. The efficiency was bad and the cost was great.

  In view of this point, an object of the present invention is to provide a method of manufacturing a drawn tube with good surface quality that can produce a drawn tube with good surface quality at high efficiency and at low cost.

  Conventionally, when a tube is pulled out using a die or a die and a plug, the reason why it is difficult to improve the dimensional accuracy of the tube is because of the drawing, the die inside the processing tool and the outer surface of the tube, the plug and the inner surface of the tube There is inadequate contact. For this reason, there are cases where the inner and outer surfaces of the tube have free-deformable portions in the machining bite and the unevenness cannot be smoothed. As a countermeasure, the diameter reduction ratio is increased to improve the dimensional accuracy. However, when the diameter reduction ratio is increased, the tube is seized on the die or plug and flaws are generated on the drawn tube, the surface quality of the tube after processing deteriorates, and the tube does not become a product. In some cases, the load increases significantly, making the machining itself impossible, and as a result, the production efficiency of the drawn tube is significantly reduced. In order to improve this point, conventionally, it has been necessary to form a sufficient lubricating film in advance by applying a bond treatment and further applying a metal soap. These lubrication treatments are performed by acid cleaning the surface of the tube. It was necessary to remove the scale and immerse the tube in a lubricant tank for a long time to form a lubricating coating, which was extremely inefficient and costly.

  Therefore, as a result of intensive studies on a lubricant that can be easily applied and that can sufficiently reduce the friction force between the drawing die and the outer surface of the tube, and the plug and the inner surface of the tube, the present invention having the following summary configuration has been completed. .

  (1) When a tube is pulled out with a die by forming a lubricant film on the outer surface or further on the inner surface of the tube, the above-mentioned lubrication is performed using a lubricating raw material made of a dry resin or a material added with other lubricants based on this. A method for producing a drawn tube with good surface quality, characterized in that a film is formed.

  (2) The surface according to (1), wherein a solution obtained by dissolving the lubricating raw material in a solvent or an emulsion in which the raw material is dispersed in a dispersion medium is applied to a tube and dried to form the lubricating coating. A method of manufacturing a drawn tube with good quality.

  (3) The method for producing a drawn tube with good surface quality according to (1) or (2), wherein the lubricating coating is formed on a steel tube with oxide scales still attached.

  (4) A method for producing a drawn tube with good surface quality according to any one of (1) to (3), wherein a plug is inserted into the tube formed with the lubricating coating and the drawing is performed. .

  According to the present invention, a sufficient lubrication effect can be obtained with a simple treatment, and therefore a drawn tube having a good surface quality can be manufactured with high efficiency and at low cost.

  In order to easily apply the lubricant, it is desirable that a lubricant film having a sufficient thickness can be formed by being applied as it is to a tube (element tube) as a material to be drawn. In the study of the present inventors, when a liquid lubricant is applied, not only does the dripping occur even if the viscosity of the lubricant is increased, the film thickness is reduced, but an extreme pressure additive such as molybdenum disulfide is included. It was understood that the friction force could not be reduced sufficiently even with liquid lubricants. In addition, in the case of the grease-like lubricant, the thickness of the lubricating coating can be increased, but the frictional force cannot be sufficiently reduced.

  In contrast, in the present invention, a drying resin, that is, a resin that is dried in the air, is used as the lubricating raw material. This kind of resin can be applied to the base tube to obtain a sufficient film thickness without causing dripping, and a sufficient frictional force reducing effect can be obtained. As the drying resin, those having a functional group in the molecule of a polymer lubricant such as polyacrylate and polymethacrylate are preferable. In addition, the lubricating raw material used in the present invention may be one obtained by adding another lubricant (such as the conventional liquid lubricant or grease-like lubricant) based on the drying resin. Further, it is further preferable to add an extreme pressure agent, an oiliness improver or the like into the resin.

  If it is difficult to apply the lubricant as it is, apply it as a solution dissolved in a solvent or an emulsion dispersed in a dispersion medium (eg water), and evaporate the solvent or dispersion medium in the atmosphere. Thus, a lubricating coating can be easily formed. When applying as an emulsion, an alcohol such as ethyl alcohol may be mixed in the emulsion in advance.

  In addition, in order to easily form a lubricating coating, it is desirable that a solution or emulsion of a lubricating raw material can be directly applied to a steel pipe as a raw pipe. However, the steel pipe generally has an oxide scale formed on the surface. If this oxide scale is present, adhesion between the lubricating coating and the surface of the raw tube is insufficient, and the lubricating effect is impaired. On the other hand, since the lubricating coating formed by the present invention has good adhesion to the oxide scale, the lubrication treatment before drawing is performed at each stage by forming it on the steel pipe with the oxide scale attached. In addition, the frictional force can be sufficiently reduced and wrinkles due to seizure can be prevented.

  In order to further improve the dimensional accuracy of the drawing tube, it is preferable to insert the plug into the base tube having a lubricating film formed on the inner surface for drawing.

固定 40mm × 6.0mmt × 5.5mL steel pipe is used as a base tube, and the plug with the mirror surface plug and an integral type fixed die is used. And pulled out to obtain a drawn tube of φ30 mm × 5.3 mmt. Prior to drawing, the following various lubrication treatments were applied to the inner and outer surfaces of the raw tube.
(Invention Example 1) The oxide scale on the surface of the raw tube was left as it was, and a solution obtained by diluting a drying resin with a solvent was applied and dried. A polyacrylate drying resin was used as the drying resin, and dimethyl ether was used as the solvent.
(Invention Example 2) The oxide scale on the surface of the raw tube was left as it was, and an emulsion in which a drying resin was dispersed in a dispersion medium was applied and dried. A polyacrylate drying resin was used as the drying resin, and water was used as the dispersion medium.
(Comparative example 1) The oxide scale on the surface of the base tube was left as it was, and a liquid lubricant was injected.
(Comparative Example 2) A grease-like lubricant was sprayed with the oxide scale on the surface of the raw tube unchanged.
(Comparative Example 3) The base tube was acid-washed, and after metal bonding, metal soap was applied.

  Table 1 shows the surface flaw occurrence state, dimensional accuracy, and lubrication treatment time (relative ratio with the shortest one taken as 1) of the drawn tube in the inventive example and the comparative example. The dimensional accuracy is indicated by the circumferential thickness deviation (= (maximum thickness−minimum thickness) / average thickness × 100%) obtained from the image analysis data of the pipe cross section.

  From Table 1, it can be seen that in the examples of the present invention, even when the drying resin is diluted with a solvent or coated with an emulsion and dried, no wrinkle is generated and the surface is good and the dimensional accuracy is remarkably good. It was.

  On the other hand, in Comparative Example 1 using the liquid lubricant and Comparative Example 2 using the grease-like lubricant, wrinkles occurred and the dimensional accuracy also decreased. Further, in Comparative Example 3 in which acid cleaning → bonding process → metal soap application was performed, wrinkles did not occur, but the lubrication process took a long time and efficiency was lowered.

It is a schematic diagram which shows the outline | summary of the cold check method.

Explanation of symbols

1 Plug 2 Die 3 Pipe drawing machine 4 Drawing direction 5 Pipe (metal pipe, steel pipe)

Claims (4)

  When forming a lubricating coating on the outer surface or further on the inner surface of the tube and drawing the tube with a die, the lubricating coating is formed by using a lubricating raw material made of a drying resin or a material added with other lubricants based on this. A method for producing a drawn tube having good surface quality.   2. The surface quality is good according to claim 1, wherein the lubricating coating is formed by applying a solution obtained by dissolving the lubricating raw material in a solvent or an emulsion in which the raw material is dispersed in a dispersion medium to a tube and drying it. Method for manufacturing a simple extraction tube.   3. The method of manufacturing a drawn tube with good surface quality according to claim 1 or 2, wherein the lubricating coating is formed on a steel pipe to which oxide scale is still attached.   The method of manufacturing a drawn tube with good surface quality according to any one of claims 1 to 3, wherein the drawing is performed by inserting a plug into the tube formed with the lubricating coating.

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