JP2006289479A - Intensive working method of metal, and die used for intensive working method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal intensive working method capable of improving the mechanical properties of a metallic material for structural use which is used in an automobile, an aircraft or the like, and improving the workability such as the tensile elongation and ductility. <P>SOLUTION: In the metallic material intensive working method, the metallic material is extruded by using a twist die in which a twist die having spirally formed holes of the same section and a return die having holes of the same section formed in the straight direction are alternately combined with each other. The characteristics of a worked product are adjusted by combining the twist dies of the same twist direction and the opposite twist direction. A mandrel is provided on an end of the return die to form a long hollow product of an arbitrary shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The invention of this application is to extrude metal materials, especially structural metal materials used in automobiles, aircrafts, etc. and apply a predetermined shear strain to make the crystal grain structure finer and improve mechanical strength and tensile elongation. The present invention relates to a new strong working method of a structural metal material that also improves ductility such as, and a mold for imparting shear strain used therefor.

  A method for extruding a metal material using a twisting die is conventionally known. However, the conventionally known extrusion method for metal materials using a twisting die is used to form a molded product with a twisted shape. This is not intended to improve the characteristics (Patent Documents 1 to 5).

  Of course, when a metal material is extruded by using a twisting die, a certain amount of shear strain is applied to the molded product, so that the characteristics of the metal material are improved. However, when forming a molded product with a torsional shape loaded using a torsion die, the amount of shear strain that is applied by twisting in a single direction is determined only by the shape of the tip of the torsion die, so the total There is a limit to the shear strain loaded at.

  In this way, the method of improving the characteristics of the metal material by actively introducing shear strain using a die having a bent hole instead of using a twisting die to form a torsion molded product is also described. Known before application (Non-Patent Document 2).

  For example, a method called an ECAP (Equal Channel Angular Pressing) method is known as a method for improving the properties of a metal material by positively introducing shear strain into the metal material. The method is a processing method in which a large shear deformation is applied to the metal material by pushing the metal material from one of the molds having holes having the same shape at the inlet and outlet and having a bent portion at the center, and taking out from the other. It is characterized by a high-strength material based on the Hall Petch rule and no change in material shape before and after processing. This ECAP method could not be achieved in the past because not only the cross-sectional area of the metal material in the mold hardly changes, but it is possible not only to introduce repeated strain but also to load a large strain by one extrusion. It is possible to refine the crystal structure up to the region.

  However, this ECAP method is a batch type (batch type), which not only takes time and labor, but also has a low throughput and is used at the laboratory level because of low productivity. It has not been.

In addition, a means for imparting a shear strain by directly imparting a twist to a solid circular cross-section material has been proposed, but the cross-sectional shape is limited to a circle because no combination of twist and return (non-patent literature) 3 and 4) and there is a problem in terms of dimensional accuracy due to the absence of circumferential constraints by the mold (Non-Patent Documents 1 and 3).
JP 2002-248518 A Japanese Patent Laid-Open No. 09-109920 JP 09-104905 A Japanese Patent Laid-Open No. 06-099215 Japanese Patent Laid-Open No. 05-131213 Anada, Tanaka, Furui, Saji, “Recovery and deformation characteristics of aluminum alloy rods by untwisting”, Light Metal, Vol. 33 (2003) 20-26. Toshiji Mukai, Kenji Higashi “Refining crystal grains and improving mechanical properties of light metal materials by ECAE process”-Tradeoff balancing of high strength and high ductility-Metals, Vol. 170 (2000) No. 11, p71-77. Higashino, Miyahara, Neishi, Nakamura, Kaneko, Nakagaki, Horita, "Fine grain analysis and improvement of mechanical properties of Al-Mg alloy by high strain high speed continuous machining process" STSP "", Summary of the 55th Plastic Working Conference (2004) pp. 395-396. Mizunuma, “Deformation state and internal structure of aluminum subjected to torsion extrusion”, Summary of the 55th Joint Conference on Plastic Working, (2004) pp. 389-390.

  Therefore, in view of the circumstances as described above, the invention of this application is capable of efficiently introducing shear strain into a metal material, particularly a structural metal material, in one step without requiring a large burden, and is a strongly processed metal material. The present invention provides a method for forming a material in the shape of a long body or a hollow body and a mold for imparting shear strain used therefor.

  The invention of this application solves the above-mentioned problems. First, a metal material is extruded by using a mold in which twisting dies and return dies are alternately combined, and shear strain is continuously applied to the metal material. To provide a strong processing method for loading metal materials.

  Secondly, the present invention provides a strong processing method of the above metal material using a mold in which the twisting direction of the twisting die is the same before and after the return die.

  Thirdly, the present invention provides a strong processing method of the above metal material using a mold in which the twisting direction of the twisting die is reversed before and after the return die.

  Fourthly, a strong processing method of the above metal material using a mold in which a mandrel is provided at an end of a return die is provided.

  Fifth, a mold used in the above-described strong processing method of a metal material is provided with a hole having the same cross section as that of a twisting die in which a hole having the same cross section is provided in a spiral shape in a straight direction. Provided is a mold in which return dies are alternately provided.

  Sixth, the above-mentioned mold is provided in which the cross section of the hole provided in the twisting die is any one of a circle, an ellipse, a square, and a gear.

  Seventh, the above-described mold is provided in which the rotational axis of the torsion die is provided in a portion other than the central portion of the cross-sectional shape.

  Eighth, the above-described mold in which a plurality of material supply holes are provided in a twisting die is provided.

  According to the first invention of a strong processing method for a metal material, the metal material is extruded by using a mold in which a twisting die and a return die are alternately combined, whereby the crystal grain structure is miniaturized and strongly processed. Metal materials can be obtained continuously.

  According to the invention of the second strong working method, a metal material having a further strengthened texture can be obtained by using a mold in which the twisting direction of the twisting die is the same before and after the return die.

  According to the invention of the third strong working method, a metal material in which a relatively random texture is formed by using a mold in which the twisting direction of the twisting die is opposite to that before and after the return die. Can be obtained.

  According to the invention of the fourth strong processing method, it is possible to obtain an elongated body or hollow body of a strongly processed metal material.

  According to the fifth mold invention, it is possible to obtain a mold capable of continuously molding a long body or hollow body of a metal material with improved mechanical strength and ductility.

  According to the sixth mold invention, a mold that can be molded under optimum conditions can be selected according to the physical properties of the metal material.

  According to the seventh aspect of the present invention, a mold can be obtained in which a shearing strain can be applied relatively equally to a molded body of a metal material having an arbitrary cross section.

  According to the eighth invention of strong working method, a mold capable of simultaneously carrying out a plurality of strong working methods of metal material is obtained.

The strong processing method of the metal material of the invention of this application will be described in comparison with a conventionally known method. FIG. 6 schematically shows a conventionally known ECAP (Equal Channel Angular Pressing) method. It is. In this ECAP method, a metal material (b) is placed in a mold (c) provided with a hole having a bent portion having the same cross-sectional area, and a load (a) is applied from above to shear the metal material at the bent portion of the hole. Strain (e) is applied to refine the crystal grain structure. And it is the method of carrying out the strong processing of the metal material by taking out the metal material strongly processed by the crystal grain structure being miniaturized from the outlet (d). However, this ECAP method is a batch type (batch type), which is not only low in productivity, but also cannot form a long body, and this ECAP method is a bent portion of a hole provided in the mold (c). Since the amount of shear strain applied to the metal material differs between the inner angle and the outer angle, the crystal grain structure cannot be uniformly miniaturized.

  The present invention is different from the conventional method in which shear strain is introduced into a metal material by utilizing the bent portion of the hole, and the metal material is extruded using a twisting die, and the shear strain due to torsion is loaded, and after torsional deformation. This is a strong processing method for introducing shear strain into a metal material by returning it to its original shape using a return die. The invention of this application is characterized in that an infinite strain is applied by extruding a metal material using a mold in which a twisting die and a return die are combined, and repeating twisting and returning. In the invention of this application, it is possible to form a long material having a large cross-sectional area or a complicated shape, and it is possible to cope with an increase in the size of a metal material.

The invention of this application will be described in detail with reference to FIGS. 1 to 5. FIG. 1 is an exploded view of a die for imparting shear strain according to the invention of this application, and a twisting die (1) to which a predetermined twist is applied. It consists of a return die (2). In addition, although the cross-sectional shape of this twisting die (1) can be set arbitrarily, the cross-sectional shape of the twisting die (1) needs to be the same shape at any part where the metal material is extruded. 2A, 2B and 2C show the cross-sectional shape of the torsion die used in the present invention. As shown in FIG. 2, the torsion die only has a rectangular shape (A). Instead, a shape such as an elliptical cross section (B) or a circular cross section with a circumferential groove (C) can be used. FIG. 2 shows a typical torsion die, and it goes without saying that various other shapes are considered. The arrows in FIG. 2 indicate the direction of twisting in the twisting die, and the metal material is extruded along this direction. FIGS. 3A, 3B, and 3C show a torsion die that can equally apply a shear strain to an arbitrary cross section by providing a rotational axis of torsion at a position different from the center of the cross section. Is shown. Further, the direction of the arrow in FIG. 3 indicates the twisting direction of the twisting die, and the number of arrows indicates the number of material supply holes supplied to the twisting die. In FIGS. 3B and 3C, a plurality of arrows are shown, but by providing a plurality of material supply ports in this way, it becomes possible to simultaneously apply a shear strain to a plurality of metal materials. FIG. 4 schematically shows a typical shear strain die of the present invention in which a twisting die (1) and a return die (2) are combined, and FIG. 5 shows a twisting die (1) and a return die (2). ) Is another embodiment of the shear strain imparting mold of the present invention. Comparing the configuration of FIG. 4 with the configuration of FIG. 5, the twisting die (1) of the mold shown in FIG. 4 has the same twisting direction before and after the return die (2), whereas FIG. The torsion die (1) of the mold indicated by is different in that the twist direction of the torsion die (1) is reversed before and after the return die (2). In the invention of this application, the characteristics of the molded body can be controlled by selecting and combining the twisting die and the return die. For example, by combining the twisting die (1) and the return die (2) as shown in FIG. 4, the texture that changes due to torsional deformation can be strengthened, whereas the twisting die (1) and the return die By combining (2) as shown in FIG. 5, a relatively random texture can be formed. Also, in the shape of the metal material to be molded, a pipe having a cross-sectional shape such as a square can be formed by providing a mandrel or the like on the return die shown in FIG. As described above, according to the invention of this application, it is possible to form a long body of a strongly processed metal material in various forms by appropriately combining the twisting die (1) and the return die (2). In the invention of this application, the temperature range of the heat treatment in the extrusion process varies depending on the type of metal material to be used. For example, when pure magnesium is used, it is preferably about 90 to 150 ° C.

  The magnesium alloy AZ31 (Mg-3 wt.% Al-1 wt.% Zn-0.2 wt.% Mn) was extruded using a torsion die / return die having a square cross section shown in FIG. The length of one side of the square of the die hole was set to 12 mm, and after twisting 180 degrees with a twisting die, twisting was performed with a return die. The extrusion temperature was 220 ° C. When the structure of the extrusion was observed, it was possible to refine the structure from an initial structure having an average crystal grain size of 20 μm to an average crystal grain size of about 3 μm. As a result of the tensile test, the tensile elongation value was improved by about 1.5 times compared to the initial material.

  It can be expected to be used in various fields of automobiles and aircraft that require high mechanical strength such as structural metal materials and excellent workability such as ductility.

A twisting die and a return die are schematically shown. The cross-sectional shape of a typical torsion die is shown, (A) is a rectangular cross-sectional die, (B) is an elliptical cross-sectional die, and (C) is a circular cross-sectional die with a circumferential groove. The cross section of the torsion die provided with the rotational axis of the torsion die at a position different from the center of the cross-sectional shape and the twist direction are shown. (A) is one raw material supply port, (B) is two A raw material supply port, (C), shows four raw material supply ports. This is a twisting die in which twisting dies having the same twisting direction are combined. This is a twisting die in which twisting dies with opposite twisting directions are combined. It is the schematic which showed the cross section of the ECAP method of a prior art example.

Explanation of symbols

a: Load b: Metal material c: Mold d: Outlet e: Refined crystal structure

Claims (8)

A strong processing method for a metal material, characterized in that the metal material is extruded using a mold in which a twisting die and a return die are alternately combined. 2. The method for strongly processing a metal material according to claim 1, wherein a mold having a twisting direction of the twisting die in the same direction before and after the return die is used. 2. The method of strongly processing a metal material according to claim 1, wherein a die having a twisting direction of the twisting die opposite to that before and after the return die is used. 4. The method of strongly processing a metal material according to claim 1, wherein a die having a mandrel provided at an end of the return die is used. A shear strain imparting die, wherein a twisting die in which holes having the same cross section are provided spirally and a return die in which holes having the same cross section are provided in a straight direction are alternately combined. 6. The mold according to claim 5, wherein a cross section of the hole provided in the twisting die is one of a circle, an ellipse, a square, and a gear. The mold according to claim 5 or 6, wherein a rotation axis of a hole of the twisting die is provided at a portion other than a center portion of the twisting die hole. The die according to any one of claims 5 to 7, wherein a plurality of material supply holes are provided in the twisting die.

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