DE112005000491T5 - A method of extruding tubes from metal alloy billets - Google Patents

Abstract

One Article made of a magnesium alloy tube, the article has a grain size of between 10 μm and 50 microns has and produced by hydroforming.

Description

AREA OF INVENTION

These This invention relates to methods of extruding metal alloy tubes and structures formed by such methods, in particular Extrusion using magnesium alloys.

BACKGROUND OF THE INVENTION

metal profiles and pipes become common produced by extrusion. In the process, a round metal block, called "club", in a heated container given, on the one hand a rammer and on the other Side has a hollow shape. The ram is used to pressure on the stick in the direction of the mold. The stick is through an opening pressed into the mold, and the metal is deformed into an extruded body having a cross section in the form of the opening Has. This is called direct extrusion. In another known extrusion process, the mold is the billet emotional. The stick is thus stationary in relation to to the container, which eliminates friction there and the pressure required for extrusion is reduced. Surface damage the stick however, are transferred to the extruded material. This is called indirect extrusion designated.

The Deformation of an article having a cross-sectional area to a An article with a smaller cross-sectional area results in a greater length. The relationship the cross sectional area of the stick to the cross-sectional area of the extruded body is in the art as well as in the present description and the claims as the extrusion reduction ratio.

Around by means of extrusion hollow shapes, such as. To produce pipes, gets a thorn in the opening placed in the mold. The metal is between the mold and pressed the thorn, resulting in the formation of a cavity in the metal, which is the shape of the mandrel Has.

since Briefly, hydroforming (internal high pressure forming, IHPF) used to make parts with complex shapes, especially in the Vehicle industry, mold. IHPF uses fluid pressure to the part in the desired Shape to press. With this procedure, components that otherwise produced as different parts and then joined together would manufactured as a unit. This will change the mass of the component reduced and maintained their rigidity, through the elimination of spot welding connections.

Further Benefits of using IHPF include weight reduction more efficient section shaping of the component and tailoring their wall thickness, improved structural strength, lower Processing costs due to fewer parts, fewer secondary operations, such as the welding of parts, smaller dimensional tolerances and fewer sections for the final assembly needed become.

For now IHPF is used for the production of steel and aluminum parts.

SUMMARY OF THE INVENTION

The The present invention relates to the adaptation of hydroforming for magnesium, to In particular, in the reduction of the weight of a vehicle, thereby increasing fuel economy and reducing emissions.

According to one Aspect of the present invention, an article is provided is made of a magnesium alloy tube Isz, wherein the Article a grain size of between 10 microns and 50 microns and is produced by hydroforming. The temperature at Hydroforming is between 200 ° C and 605 ° C. The tube is made by extrusion prepared, wherein the extrusion temperature is between 300 ° C and 605 ° C, the extrusion speed substantially between 5 mm / s and 45 mm / s and the extrusion reduction ratio in Essentially between 10: 1 and 50: 1. The tube can last for 6 hours at 300 ° C annealed become.

According to one Another aspect of the present invention is a method for Forming a hollow tube provided by extrusion from a billet, which is made of a magnesium alloy, comprising the Steps of heating the cudgel to a predefined temperature within a temperature range, the extrusion of the billet by means of an indirect extrusion process, wherein the temperature in a range of 300 ° C up to 605 ° C is located, the extrusion speed substantially in the range between 5 mm / s and 45 mm / s and the extrusion reduction ratio in Essentially in the range between 10: 1 and 50: 1.

According to another aspect of the invention, there is provided a hydroforming process using tubes made in accordance with the method described above. The method comprises the steps of: cooling the tube at a predefined temperature for a predefined period of time, sealing the tube from both ends, inserting a pressure tube into the tube, positioning the tube in a mold having a guide zone and an expansion zone, wherein the temperature of the expansion zone is between 200 ° C and 605 ° C, and applying an axial compressive force to the tube, with the result that the section of the Pipe, which lies within the expansion zone, expands to fill the zone and thereby assume its shape. The tube is then cooled for a predefined period of time at a predefined temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Around to understand the invention and to see how it works in practice carried out will be, now, solely as non-limiting Example, an embodiment with reference to the attached Drawings in which:

1 Figure 10 is a partial cross-sectional view of a typical extrusion press that may be used with an extrusion process of the present invention;

2 FIG. 4 is an illustration of a typical equipment setup that can be used in hydroforming; and FIG

3 a representation of the construction in 2 wherein a tube is subjected to hydroforming.

DETAILED DESCRIPTION OF THE INVENTION

A Extrusion press, known in the art, is prepared using specific Parameter used to extruded magnesium parts with properties to form, which make it possible in industrial applications, such. In the automotive industry, to perform a plastic deformation on it.

1 represents an extrusion press 10 which is a container 12 includes, trained to a magnesium billet 14 a ram 16 , a mold 18 and a flying thorn (not in 1 shown). The mold 18 includes an opening 19 with a predefined shape. The magnesium billet 14 is heated so that its temperature is within a range of 300 ° C to 605 ° C. The heated billet 14 gets into the container 12 positioned, and the mold 18 becomes a cudgel 14 moved, wherein it exerts a pressure which the stick 14 to an extrusion 20 deformed, which has a similar scope as the opening 19 Has. The extrusion press 10 is trained to get the truncheon 14 during extrusion at the predefined temperature. The mold 18 is moved at an extrusion speed that is substantially between 5 mm / s and 45 mm / s. The mandrel is positioned so that it has a cavity 21 in the extrusion 20 forms and determines the size and shape of the cavity. The space between the mold 18 and the mandrel determines the cross-sectional area of the extrusion 20 , The extrusion reduction ratio is substantially between 10: 1 and 50: 1.

When heating the magnesium billet 14 should be taken into account that additional heating takes place due to the pressure inherent in the extrusion process. Therefore, the stick should 14 Do not heat from the beginning to the desired temperature, so that it is not exceeded during the extrusion.

The billet used for extrusion 14 may be an undrilled billet or a pre-drilled billet with a hollow center.

The Magnesium used in this process can be any commercial magnesium alloy, such as AM60, AS41, AZ31, AZ61, AZ80, AZ91, ZE41 or ZM21. alternative It can be an alloy made to customer specifications. Preferably, the magnesium obtained by the process of the present invention Invention, either the AZ31 or the ZM21 alloy. The combination of parameters for every single magnesium alloy can by the professional by trial and error Error be detected.

According to one certain embodiment the chemical composition of the magnesium alloy used in the Method according to the present invention To 2.856 Al, 1.022 Zn, 0.329 Mn, 0.004 Fe, 0.038 Si, 0.001 Cu and 0.001 Ni. In a conducted experiment was a system with continuous casting with a sliding jaw of 42 mm, a mandrel of 38 mm and a container of 110 mm used. The magnesium billet was 155 mm long, had a diameter of 107 mm and was with a hole diameter of 38 mm predrilled (need pre-drilling to confirm). The extrusion speed was 1.6 mm / s, with a billet and the container to 320 ° C were heated. The extrusion reduction ratio was about 30: 1, with a total power of 4.45 MN.

The magnesium pipe obtained by the above-described method had mechanical properties imparting strength and durability to easily withstand plastic deformation inherent in further production of the pipe. Specifically, it had a yield strength of 195 N / mm ² , a ultimate tensile strength (UTS) of 255 N / mm ² and an elongation at break of 14%.

A method for which the magnesium tube obtained as described above can be used is hydroforming. Regarding 2 This is done with the help of specialized equipment 22 reached. Equipment 22 includes a clamping unit 25 on each side of the pipe 23 is arranged, and a molding unit 27 that surrounds her. The clamping unit 25 includes pressing beams 24 , Hydraulic cylinder 26 , Sealing stamp 28 and suitable heating and cooling agents. The closure stamp 28 are formed to seal the ends of the tube during molding, and at least one includes an opening 42 , which is adapted to introduce a pressure medium from a pressure source (not shown) in the tube. The mold unit 27 includes body material 30 , Molds 32 which is an expansion zone 36 form, inserts 34 , the leadership zones 38 form, and suitable heat and coolant.

Regarding 3 becomes the pipe 23 within the equipment 22 deformed. If the pipe 23 is held in the equipment, its ends are closed, and a pressure medium with a molding pressure therein through the opening 42 introduced. A high pressure is applied to the medium and an axial compressive force (indicated by arrows 44 ) gets on the pipe 23 exercised. The expansion zone 36 is maintained at a temperature substantially in the range of 200 ° C to 605 ° C, to ensure the necessary for reshaping hoop stress. In the leadership zone 38 is maintained at a lower temperature, for. In the range of 100 ° C to 200 ° C. This will ensure that the yield stress of the section of the pipe 23 in the leadership zone 38 sufficient to apply the axial force to the section of the pipe in the expansion zone 36 transferred to. (For example, depending on the alloy used, in the temperature range of about 350 ° C to 400 ° C, the yield stress may decrease to 40 N / mm ^2. The higher the axial force transmitted to the section of the pipe in the expansion zone, the higher the Hoop stress that can be achieved resulting in higher ductility.) Consequently, the pipe deforms 23 in the expansion zone 36 and forms a bump 40 that the shape of the mold 32 occupies.

For the expert will be clear that the molding pressure on the basis of Magnesium alloy is determined for the production of the pipe the thickness of it, the special geometry of the forming part and the temperature used for molding. A smaller radius and a lower temperature require one higher Molding pressure. Even a thicker wall requires a higher forming pressure.

The Pressure medium is a fluid that is either a gas or a heat resistant Fluidum is. According to one embodiment it is a gas that does not react with another material, with that during it IHPF comes into contact. It is preferably recyclable for later use. In particular, nitrogen or one of the noble gases is used. The Use of a gas has several advantages over that Use of a liquid, as gases, as described with reference to the processes described herein high temperatures can be heated without decomposing.

The ductility of the magnesium tube during IHPF is partly influenced by the strain rate of the material. This influence increases with higher temperatures. Depending on the processing time and the necessary deformability, the forming speed can vary between 2 × 10 ^-1 s ^-1 and 1 × 10 ^-4 s ^-1 .

Previous heat treatment may also affect the initial structure of the magnesium tube. The tubes can be annealed at temperatures substantially between 200 ° C and 600 ° C. In a preferred case, the annealing temperature is between 250 ° C and 300 ° C. After a maximum of six hours of annealing in this temperature range, a uniform, fine-grained structure can be seen in the tube. A grain size between 10 microns and 50 microns can be achieved. This fine-grained structure leads to improved ductility, especially at low strain rates (lower than 2 × 10 ^-1 s ^-1 ).

The methods described herein, and in particular the steps that IHPF may additionally include subsequent Followed by IHPF steps, which serve to further the pipe deform or additional structural changes to do it on him.

In one example, the following conditions are used for IHPF. After extrusion, the magnesium tube becomes 6 Annealed at 300 ° C for hours. This annealing time leads to a uniform, fine-grained structure. One skilled in the art will recognize that a fine-grained structure is particularly suitable for IHPF and similar processes. Thereafter, the magnesium tubes are preheated to a deformation temperature of 350 ° C. The expansion zone is maintained at a temperature of 350 ° C, and the guided zone is maintained at a temperature of 250 ° C. At 350 ° C, the total allowable elongation is at a peak of approximately 35%. An axial force is exerted by the hydraulic cylinders, resulting in a compressive stress condition in the wall of the pipe. Nitrogen gas is used as the pressure medium. The pressure against the time path ensures a constant forming speed in the course of the processing time.

SUMMARY

It An article is provided which consists of a magnesium alloy tube is made, wherein the article has a particle size of between 10 microns and 50 microns and is produced by hydroforming. The temperature of the Hydroforming is between 200 ° C and 605 ° C. The tube is made by extrusion, wherein the extrusion temperature between 300 ° C and 605 ° C is, the extrusion speed substantially between 5 mm / s and 45 mm / s and the extrusion reduction ratio is Essentially between 10: 1 and 50: 1. The tube can last 6 hours long at 300 ° C annealed become.

Claims (23)

An article made of a magnesium alloy tube is made, wherein the article has a particle size of between 10 microns and 50 microns and through Hydroforming is produced. An article according to claim 1, wherein the temperature of the hydroforming is between 200 ° C and 605 ° C. An article according to claim 1, wherein the tube was prepared by extrusion. An article according to claim 3, wherein the extrusion temperature is between 300 ° C and 605 ° C. An article according to claim 3, wherein the extrusion rate is substantially between 5 mm / s and 45 mm / s. An article according to claim 3, wherein the extrusion reduction ratio in Essentially between 10: 1 and 50: 1. An article according to claim 3, wherein the extrusion temperature is between 300 ° C and 605 ° C, the extrusion rate is substantially between 5 mm / s and 45 mm / s and the extrusion reduction ratio in Essentially between 10: 1 and 50: 1. An article according to one any of the above claims, wherein the magnesium alloy is selected from the group consisting of AZ31 and ZM21. An article according to claim 8, wherein the extrusion reduction ratio is substantially 30: 1 is, the extrusion rate is substantially 15 mm / s, the defined temperature is substantially 300 ° C and the AZ31 alloy used becomes. An article according to claim 1, wherein the magnesium alloy is 2.856 aluminum, 1.022 zinc, 0.329 Manganese, 0.004 iron, 0.038 silicon, 0.001 copper and 0.001 nickel includes. An article according to claim 1, wherein the tube annealed becomes. An article according to claim 11 wherein the tube is annealed for six hours at a temperature of 300 ° C. A method of manufacturing a tube from a Stick, which is made of a magnesium alloy, wherein the method Includes: (a) heating the billet to a predefined one Temperature ranging from 300 ° C to 605 ° C; (b) Extrude of the truncheon with the help of an extrusion press, a ram, an interior punch and has a mold while the temperature of the billet is maintained to stay in the area, and (C) Applying a force to the billet, allowing it with a predefined extrusion speed of the ram is pressed between the mold and the mandrel, around a pipe with a predefined extrusion reduction ratio form; wherein the extrusion rate is substantially between 5 mm / s and 45 mm / s and the extrusion reduction ratio substantially between 10: 1 and 50: 1. A method according to claim 13, wherein the magnesium alloy chosen is from the group consisting of AZ31 and ZM21. A method according to claim 14, wherein the extrusion reduction ratio in the Essentially 30: 1, the extrusion rate is substantially 15 mm / s, the predefined temperature is substantially 300 ° C and uses the AZ31 alloy becomes. A method according to claim 1, wherein the magnesium alloy 2.856 aluminum, 1.022 zinc, 0.309 manganese, 0.004 iron, 0.038% silicon, 0.001% copper and 0.001% nickel. A method according to claim 1, wherein the method continue the step of annealing of the pipe. A method according to claim 17, wherein the tube It is annealed for six hours at a temperature of 300 ° C. A method according to claim 13, further comprising the steps of: (d) cooling the tube at a predefined time th cooling temperature over a predefined period of time; (e) sealing the tube from both ends; (f) introducing a pressure medium into the tube; (g) positioning the tube in a mold having a guide zone with a predefined guide temperature and an expansion zone having a predefined shape at a predefined expansion temperature; (h) applying an axial compressive force to the tube such that a portion of the tube located in the expansion zone expands to conform to the predetermined shape; and (i) cooling the tube at a predefined second cooling temperature for a predefined period of time; wherein the expansion temperature is in a range of 200 ° C to 605 °. A method according to claim 19, wherein the expansion temperature essentially between 200 ° C and 500 ° C lies. A method according to claim 19 wherein the print medium is a Gas is. A method according to claim 21, wherein the gas under the conditions used in the process not with the Metal reacts. A method according to claim 19, wherein the printing medium a heat-resistant liquid is.