JP4092306B2 - Hollow light metal member extrusion method, hollow extrusion die, and hollow light metal extrusion member - Google Patents

Description

  The present invention relates to a technique for manufacturing a hollow member (product) made of a light metal such as aluminum by extrusion, and particularly to an extrusion technique for obtaining hollow members having various cross-sectional shapes from a solid light metal material. Is.

  Conventionally, a method shown in FIG. 5 is known as a method for producing a hollow member made of a light metal typified by an aluminum alloy using hot extrusion. In this method, a light metal material 1 formed as a solid billet is introduced into a container 2 of an extrusion device in a heated state, and pressure is applied from behind the light metal material 1 (from the direction of arrow A in the figure) by a stem 3. A hollow member 5 (product) is formed by extruding forward (in the direction of arrow B in the figure) from a die hole having a predetermined cross-sectional shape through a hollow couple die 4 provided in a die holder 9 connected to the container 2. In this example, a rectangular tube) is obtained.

  In this method, as the hollow couple die 4, a loader die such as a bridge die, a porthole die, or a spider die is used. FIG. 6 shows a porthole die as an example of the horodice.

  The hollow couple die 4 includes a male die 4a located on the billet side and a female die 4b located on the hollow member 5 side, and is used in a state in which both dies 4a and 4b are fitted together.

  The male die 4a has a plurality of entry ports 6 (four in the figure, one is omitted in the figure) drilled in the circumferential portion thereof, and is pushed out from the central portion. A male bearing 7a (mandrel portion) projects toward the downstream side (the female die 4b side). In the female die 4b, a substantially cross-shaped welding chamber 8 corresponding to each entry port 6 of the male die 4a is recessed, and the female die 4b is penetrated in the axial direction at the center position of the welding chamber 8. A female bearing 7b, which is a hole, is provided. The female bearing 7b has a shape that allows the male bearing 7a of the male die 4a to be inserted with a gap having a specific shape (in the example of the figure, a thin rectangular tube shape). The hollow member 5 having a cross section corresponding to the shape can be extruded.

  The extrusion mechanism using the hollow couple die 4 will be briefly described with reference to FIG. First, the light metal material 1 pushed from the direction of the arrow A is pushed into the four entry ports 6 of the female die 4b and diverts to each entry port 6. That is, the light metal material 1 is divided into four parts 1a, 1b, 1c, and 1d. The diversion portions 1a to 1d merge in the welding chamber 8 of the next female die 4b after passing through the entry port 6, and are welded to each other to be united again. Further, the integrated light metal material 1 includes an outer peripheral surface of a male bearing 7a having a rectangular cross section and an inner peripheral surface of a female bearing 7b having a rectangular cross section into which the male bearing 7a is inserted with a gap. The hollow member (rectangular tube) 5 having a rectangular hollow cross section corresponding to the shape of the gap is formed by being extruded from the gap in the direction of arrow B. Accordingly, the molded hollow member 5 has the welded portions 5a at the four ridge lines.

  That is, since the hollow member 5 which is a product obtained by this method is extruded through a process of “dividing” and “merging / welding” which is not possible with a method using a normal solid die, There are necessarily welded portions 5a corresponding to the number and position of the entry ports 6 of the couple die 4. The metallurgical adhesion between the welded portion and the bare portion (non-welded portion) largely governs mechanical properties such as tensile strength, proof stress, and elongation of the hollow member, particularly strength. If the adhesion of the welded portion is insufficient, cracks and deformations may occur during the subsequent secondary processing or use of the product, and the quality may not be sufficiently guaranteed.

  In addition, among the hollow dies, in particular, extrusion using a bridge die has an advantage that the die life is longer than that of other hollow dies, but there is a drawback that it is difficult to operate to ensure the strength of the welded portion. For example, in the case of an aluminum alloy, there are no problems with some products that do not require relatively high strength, such as JIS 3000 and JIS 6000, but in the case of a product that requires high strength such as JIS 7000, its metallurgical Due to the characteristics, it is very difficult to ensure a sufficient strength at the weld. Furthermore, in the JIS 5000 series, extrusion using a hollow die is said to be impossible in this industry, and even its development has been abandoned.

  In addition, in conjunction with the conventional situation, there is no appropriate method for evaluating the strength of the welded part in advance, and in fact, it is actually confirmed for the first time by post-manufacturing inspection such as a pipe expansion test. Insufficient products often occur, and the product yield is low. If such a lack of strength is discovered, it is dealt with through empirical knowledge and trial and error by changing the die shape and extrusion conditions, but such measures lack new reproducibility and versatility, and have no experience. The product shape and required characteristics could not be dealt with sufficiently and quickly, and the production of the dice was wasted, which had to be said to be extremely inefficient.

  In view of such a conventional situation, the present invention eliminates all the basic problems in the strength of the welded portion in the extrusion process using a hollow die such as a bridge die, and is a hollow light metal member having excellent mechanical properties ( Product) was able to be manufactured stably, and at the same time, it was made for the purpose of realizing and establishing a new extrusion technology that can efficiently produce products that match the required strength level at a low cost. Is.

  In order to achieve the above object, the present invention employs the following configuration.

That is, the present invention is a method of extruding a light metal material using a hollow extrusion die, the light metal material is once shunted, merged and welded to each other, and the light metal material after the merge is formed into the hollow And extruding into a desired cross-sectional shape through a die hole of an extrusion die, and in this extruding step, it is applied to the light metal material from the welding chamber inlet cross section to the outlet section product cross section of the extrusion die. so that the average value of the distortion distribution amount is less than 2.4, the cross-sectional area of the material flow part in the welding chamber (Am), the cross-sectional area of the product (Atp), the height of the welding chamber (H _M) and the die thickness The die design factor (H _D ) is analyzed and determined by a numerical analysis method, and the extrusion process is performed using a die designed based on the determined design factor. The

Here, the “strain amount” means an average value of the equivalent strain distribution amount generated in the light metal material from the welding chamber inlet cross section to the die outlet portion product cross section.

  By maintaining such an amount of strain at 1.8 or more, it becomes possible to increase the tensile strength of the welded portion in the product to a strength that is substantially close to the tensile strength of the bare portion.

  This method can be applied to various light metal materials, but is particularly effective when the metal constituting the hollow light metal member is an aluminum alloy.

  As this hollow extrusion die, a bridge die, a port hole die, or a spider die is suitable.

  Hereinafter, the principle and action of the present invention and preferred embodiments thereof will be described in detail.

  With the aim of solving the above problems, the present inventors have continued experimentation and examination focusing on factors that influence the strength of the welded portion, and it is generally assumed that this is quantitatively controlled. We have determined that this is not the product temperature, but the amount of strain experienced by light metal materials at specific locations within the hollow die. Furthermore, as a result of further research, it is also experimentally determined that when the amount of strain exceeds a certain threshold, the strength of the welded portion is improved to a strength close to the strength of the bare portion (the portion not involved in welding). I was able to. Based on these facts, the relationship between the amount of strain and the shape and structure of the hollow die is quantified, and the result is reflected in the die design to obtain a hollow member with high welding strength and excellent quality. As a matter of course, it has been found that hollow members suitable for various required strength levels can be produced freely.

  In clarifying the effect of this amount of strain on the welding strength, the inventors first changed what deformation during the process in which the material billet supplied under pressure in the container is extruded as a product through a hollow die. I decided to consider the change in the cross-sectional area.

  1 (a) and 1 (b) show an example of a bridge-type die 4, and FIGS. 2 (a) to 2 (d) show a metal (a molding material for forming a billet) in each part of the die. ), That is, a model of the cross-sectional shape. In these drawings, the peripheral outer wall portion and other members constituting the die 4 are omitted for convenience.

  The die 4 includes a male die 4a and a female die 4b that are fitted to each other. The male die 4a integrally includes a cross-shaped bridge body 41 and leg portions 42b projecting downward from four ends of the bridge body 41, and the male bearing 7a extends downward from the center of the bridge body 41. Is protruding. The female die 4b has a concave portion 43 into which each leg portion 42 of the male die 4a is fitted on the upper surface thereof, and is a female that is a hole that penetrates the female die 4a in the axial direction at the center of the bottom surface of the concave portion 43. A bearing 7b is provided. The relative relationship between the bearings 7a and 7b is the same as that shown in FIGS.

  In this die 4, the light metal material 1 formed as a billet in the same manner as in the apparatus shown in FIG. 5 enters the container from the direction of arrow A until it is finally extruded as a product in the direction B. In addition, although the cross-sectional shape of the light metal material 1 changes remarkably, FIG. 2 shows the transition of the cross-sectional shape by focusing on the sector region S having a central angle of 45 ° shown in FIG. 1 (a). It is a thing.

  Specifically, FIGS. 2 (a), (b), (c), and (d) are the lines (1)-(1), (2)-(2), (3) shown in FIG. 1 (b), respectively. The cross-sectional shape of the light metal raw material 1 in the height position of-(3) line and (4)-(4) line is shown. The light metal material 1 has a portion that flows on the center side in the die 4 and a portion that remains on the outside and stays without flowing. FIG. 2 (a) (b) ) (C) and (d), the flow portion 1a of the light metal material 1 is shown as a fine mesh portion, and the non-flow portion 1b is shown as a coarse mesh portion.

  First, at the position of the line (1)-(1), that is, the position in the container on the upstream side of the die 4, the flow portion 1a of the light metal material 1 occupies the entire cross-sectional area, but (2)-(2 ) At the position of the line, that is, the position where the bridge main body 41 exists and is located above the leg portion 42, the light metal material 1 has four positions as shown in FIG. The cross sectional area is reduced corresponding to the opening area between the bridge bodies 41.

  After that, when the branch part passes the bridge body 41 and reaches the position of the line (3)-(3) where the leg part 42 exists, the welding formed below the bridge body 41 and inside each leg part 42. They merge again in the chamber 8 and weld together. Therefore, the cross-sectional shape of the metal (molding material) here is as shown in FIG.

  At the position of line (4)-(4) where both bearings 7a and 7b exist, the metal cross-sectional area becomes the area of the gap formed between both bearings 7a and 7b as shown in FIG. 2 (d). It is constrained and will be significantly reduced from the cross-sectional area shown in FIG. 2 (c).

As a result of studying the transition of the cross-sectional shape as described above, the inventors of the present invention started from the portion of the welding chamber 8 after joining as shown in FIG. As a result, the inventors have come to the knowledge that the amount of strain imparted to the metal before reaching the part after molding as shown in FIG. In addition, the distortion amount said here means the average value of equivalent distortion distribution amount from a welding chamber entrance cross section to a die exit part product cross section as mentioned above.

From the above, this distortion amount is largely governed by the cross-sectional area (Am) of the material flow portion 1a in the welding chamber 8 and the cross-sectional area (Atp) of the product, as shown in FIGS. 3 (a) and 3 (b). also it changes by welding chamber height H _M and the die thickness H _D. 3 (a) shows the dimensions in the case of a bridge die or spider die having a bridge body 41, and FIG. 3 (b) shows the dimensions in the case of a port hole die having an entry port 6. In these figures, FIG. X represents the position of the entry port surface, Y represents the position of the upper surface of the welding chamber (upper surface of the joining portion), and Z represents the position of the die opening surface.

  If the present inventors quantify the relationship between the die design factor and the amount of distortion, the die can be designed based on this, and the problem of welding strength can be fundamentally solved. Got clear guidelines. The specific quantification (formulation, functionalization) method of the design factor and the distortion amount will not be described in detail here, but if the die shape is determined, a well-known numerical analysis method such as the finite element method or the difference method is used. Thus, since the distortion amount can be calculated, the correlation between the die design factor and the distortion amount can be obtained relatively easily.

Based on the examination and consideration of the relationship between the welding strength, the strain amount, and its controlling factor, the present inventors have investigated whether or not this can be effectively applied in the actual technology, such as an aluminum alloy such as 7000 series. Extrusion processing experiments were conducted using hollow dies having various different shapes as test materials, and the amount of strain at that time and the tensile strength of the resulting hollow member were measured. Table 1 below shows the experimental conditions, and Table 2 shows the experimental results. In Table 2, in the column of tensile strength of welded portion / tensile strength of bare portion, ◯ indicates that the strength ratio is 90% or more, and X indicates that the strength ratio is less than 90%. ing.

  The extrusion process in this experiment was performed under process conditions such that the extrusion temperature was 450 to 550 ° C., the extrusion force was 1500 to 3500 t, and the extrusion ratio was 10 to 140. “EP” in Table 1 is an abbreviation for entry port.

  From the experimental results shown in Table 2, when the strain amount is 1.8 or more, the tensile strength ratio is 90% or more, and the strength of the welded portion is bare, compared to the specimens less than that. It turns out that there is not much difference from that. Therefore, an excellent hollow member having a high weld strength can be stably manufactured by performing extrusion processing with the strain amount threshold being 1.8 and maintaining the strain amount to be equal to or higher than this value.

  Further, FIG. 4 is a graph in which the relationship between the amount of strain and the welding strength is similarly arranged by increasing the number of N in addition to the results of additional experiments in addition to these results. In the figure, the solid line parallel to the X-axis, where the tensile strength ratio between the welded part and the bare part is 100%, indicates the tensile strength of the bare part (non-welded part), and the dotted curve indicates the tensile strength of the welded part. Represents each.

  As can be seen from this figure, there is a clear positive correlation between the strain amount and the welding strength, and the strain ratio is 1.8 or more and the strength ratio is 90% or more. It turns out that is obtained. In addition, when the strain amount is in the range of 2.4 or more, a very high strength welded portion with a strength ratio of 95% or more can be obtained, and a hollow member of better quality that is almost the same as the strength of the bare material can be obtained. You can see that it is provided. That is, according to these experimental results, in order to obtain a hollow light metal member having a tensile strength ratio of 90% or more, it is essential to perform extrusion while maintaining the strain amount at 1.8 or more. If extrusion is carried out while maintaining the strain amount at 2.4 or more, a hollow light metal member having more excellent strength characteristics can be obtained.

  Thus, the correlation between the strain amount and the welding strength is obtained as a correlation, the strain amount corresponding to the target welding strength is determined based on the correlation, and the strain amount is set as the target strain amount. A hollow extrusion die is designed so that the amount of strain imparted to the light metal material is maintained above the target strain amount from the stage after joining and welding to the stage after extrusion molding. Thus, by performing the extrusion molding, it becomes possible to stably obtain a hollow light metal extruded member having sufficient welding strength.

  In addition, in the Example mentioned above, although the outstanding effect of this invention was demonstrated about the aluminum alloy, this invention is applied to the extrusion process of other light metals (including an alloy), for example, tin, antimony, titanium, magnesium, beryllium, etc. However, the same effect can be obtained.

FIG. 1 (a) is a perspective view showing an example of a hollow die used for hollow extrusion molding, and FIG. 1 (b) is a sectional front view of the die. It is the cross-sectional top view which showed the mode of the cross-sectional area change of the molding material in each site | part in the said hollow die. 3 (a) and 3 (b) are partial cross-sectional front views for explaining the dimensions of various hollow dies. It is the graph which showed the relationship between the distortion amount and welding strength based on the extrusion experiment result using a hollow die. It is sectional explanatory drawing which showed the outline | summary of the hollow extrusion apparatus. It is a partial cross section perspective view which shows an example of the hollow die used for the said hollow extrusion apparatus.

Explanation of symbols

1: Billet 2: Container
3: Stem
4: Hollow (couple) die 4a: Male die 4b: Female die
5: Hollow material 6: Entry board 7a: Male bearing 7b: Female bearing 8: Welding chamber 41: Bridge body HM: Height of welding chamber HD: Die thickness

Claims (3)

A method of extruding a light metal material using a hollow extrusion die, wherein the light metal material is once shunted and then merged and welded together, and the light metal material after the merged die hole of the hollow extrusion die And extruding into a desired cross-sectional shape through, in this extruding step, the average of the equivalent strain distribution applied to the light metal material from the welding chamber inlet cross section to the outlet product cross section of the extrusion die It consists of the cross-sectional area (Am) of the material flow portion in the welding chamber, the cross-sectional area of the product (Atp), the height of the welding chamber (H _M ), and the die thickness (H _D ) so that the value is 2.4 or more. A hollow light metal member characterized in that a die design factor is analyzed and determined by a numerical analysis method, and the extrusion is performed using a die designed based on the determined design factor. Extrusion method.   2. The method for extruding a hollow light metal member according to claim 1, wherein the metal constituting the hollow light metal member is an aluminum alloy. 3. A method for extruding a hollow light metal member, wherein the hollow extrusion die used for extrusion processing according to claim 1 or 2 is a bridge die, a port hole die, or a spider die.

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