JPH0141408B2 - - Google Patents

Description

[Detailed description of the invention]

Two problems experienced in the extrusion of certain alloys are thermal embrittlement, manifested by circumferential cracking, and extrusion die pick-up, which creates longitudinal scratches on the surface of the extruded product. The main cause of cracks due to thermal embrittlement and flaws due to seizure is that the surface temperature of the extruded product increases excessively due to friction between the die and the billet container. In the case of unlubricated extrusion, shearing the billet along the dead metal zone also contributes to the temperature increase. High temperatures can collect small particles of product on the die surface and cause scratches during extrusion. The high surface temperature (exacerbated by friction of the collected particles damaging the surface) also exceeds the solidus temperature of the lower melting phase of the alloy (e.g., the eutectic component), causing local melting and extrusion die. When tensile stress is applied, circumferential cracks can occur. The solidus temperature of the low melting phase can be raised to a point where the pressure generated within the billet is sufficient to prevent melting at these high temperatures. However, when the pressure is released near the exit of a conventional die, the temperature will rise above the solidus temperature under reduced pressure (atmospheric pressure) and melting may occur again. This melting in combination with tensile stress will cause cracks to form. In the past, extrusion speeds had to be minimized to prevent increased friction and excessive billet temperature increases. Conversely, the preheating temperature of the billet can be reduced to allow for higher extrusion speeds and associated larger temperature increases within the billet and die. Unfortunately, this often increases the extrusion pressure so that the extrusion ratio must be lowered to keep the extrusion going. In addition to the problems mentioned for thermally sensitive alloys, there are die wear, product dimensional accuracy and product surface finish issues that are common in the extrusion of metals, especially high strength, refractory metals and alloys. These can be reduced by lowering the extrusion temperature, but the extrusion pressure increases. Of course, prior examples have shown the possibility of cooling the die to avoid high temperatures within the die. For example, US Pat. No. 2,135,193 discusses the die seizure problem and proposes a water cooled die. U.S. Pat. No. 3,553,996 teaches a method for extruding brittle billet materials without cracking the surface.
One embodiment of the method includes the use of a dual extrusion die similar to that proposed in the present invention. However, reliefs are provided between the surfaces of the extrusion die. Since the material problems dealt with in the cited patents are different from the problems of materials sensitive to thermal brittleness dealt with in the present invention, the cited patents do not address the problems in the present invention. West German Patent No. 429376 cools the land of the die,
It teaches ways to increase die friction by lengthening the die lands and to reduce cracking during extrusion by slightly converging the die lands toward the die exit. The inventors of the present invention found the opposite conclusion to this West German patent, which seeks to maximize friction in the land of the die. That is, friction should be minimized to produce a good product at high speed and with minimal extrusion pressure. It is an object of the present invention to provide a die and extrusion method for the extrusion of thermally sensitive alloys. Another object of the present invention is to provide an extrusion die and extrusion method that minimizes cracking and scratching in alloys that are susceptible to cracking and scratching. Another object of the present invention is to provide a die and method that allows extrusion of good product at very high extrusion speeds compared to those currently practiced. Another object of the present invention is to provide a die and method that reduces die wear and/or improves dimensional accuracy and surface finish in the extrusion of refractory metals and alloys. Yet another object of the invention is to enable the aforementioned extrusion at lower ram pressures to reduce friction and increase preheating of the billet. In particular, it is an object of the present invention to produce commercially available alloy wires, bars, etc. from aluminum, copper, magnesium, zinc or other thermally sensitive alloys at high extrusion rates.
An object of the present invention is to provide an extrusion die and method for making tubing or other shapes. According to the above objects, the present invention is an extrusion die and extrusion method for extruding sensitive alloys at high speed. The extrusion die includes first and second dies or extrusion dies arranged in tandem along longitudinally coincident axes. The first die has a long land surface connected to the second die. The second die has a normal land length, and the cross-section of the primary extruded product extruded by the first die is reduced by, for example, 1/4-60%, preferably about 2-50%, more preferably 2- 15% reduction (referred to as secondary extrusion). The novel extrusion die also cooperates with lands of the first die and, optionally, lands of the second die, such that the lands and thus the primary and secondary extrusion dies passing in contact with the lands cooperate with each other. It has a cooling device that cools the product indirectly. For normal non-lubricated extrusion methods that do not use lubricant between the billet and the billet container, the first
The face of the die is a shear plane, that is, a flat surface (included angle of 180 degrees).
may have. The surface of the second die in this case can also be flat, but it can also be convergently tapered (up to an included angle of 5 degrees) or have a curved surface. For lubricated extrusion, whether by conventional equipment or hydrostatic equipment, the first die is The surfaces can be convergent and tapered, curved, or a combination of conical and flat shapes. In this case, the surface of the second die is also preferably convergently tapered or curved for the same reason. Multiple extrusions and single extrusions are possible according to the invention via a die designed for this purpose. The lands of the first die are designed to be much longer than normal. The length-to-diameter ratio (or circumcircle) is selected to allow extrusion cooling to the desired extent. For solid round products between 1:1 and 12:1, preferably about 1:1
to 5:1. The diameter is 1.27cm (0.5
For inch) products, the length is approximately 2.0-5cm.
(3/4-2 inches) below the solidus temperature at the lowest melt phase at the original pressure (preferably below the solidus temperature at atmospheric pressure) before being extruded through the second extrusion die. It is long enough to reduce or maintain the temperature of the extruded product. The lands of the first die are preferably straight (neither converging nor diverging), but as long as sufficient contact with the extruded product is maintained to control the temperature described above. It may be slightly widened towards the die exit to reduce land friction. For thin cross-section products (tubes, plates, shapes) the length to cross-section thickness ratio can be adjusted to provide the necessary cooling. The land of the second die is e.g. 1.6-3.2mm
(0.063-0.125 inches) or may have a relief section immediately downstream. The second die may also be longer and cooled if necessary to further maintain or reduce the temperature of the extruded product. Approx.
0.25 μm (10 micron inches) rms (root mean square), preferably 0.05 μm (2 micron inches)
It is preferable to keep the friction in the die as low as possible by polishing to rms and adding lubricant to these parts. This extrusion process involves preheating a [thermally sensitive] alloy billet at atmospheric pressure to a preferred extrusion temperature, generally below the solidus temperature of the lowest molten phase, extruding the billet through a first extrusion die having a long land surface. While in the first die before performing the second extrusion, at least a surface portion of the extruded product is cooled to reduce or maintain the extrusion temperature below the solidus temperature; a second extrusion die downstream of the first extrusion die while applying back pressure to the extruded product in the die to reduce tensile stress and maintain extrusion against the lands of the first die; The process includes extruding the extruded product through a cooled extrudate. In some cases, cooling the extruded product in the first die to a temperature that is below the solidus temperature at the original pressure but above the solidus temperature at atmospheric pressure before performing the second extrusion. is also possible. in this case,
The second die must be cooled to cool the product below its solidus temperature at atmospheric pressure before exiting the second die to the atmosphere. The degree of cross-sectional reduction by the first extrusion may be conventional, for example about 75-99%, and that by the second extrusion is about 1/4-60%, preferably about 2-50%, and more. Preferably it may be about 2-15%. The die lands and die faces are preferably polished and lubricated to reduce friction. Preferably, the extruded product is cooled through the first and second die lands by cooling channels surrounding the die lands and in which a cooling fluid circulates. Optionally, the extruded product can be further cooled to eliminate thermal changes caused by the secondary extrusion by further cooling the lands of the second die. This helps prevent thermal brittleness cracking and seizure of the die lands. For tubular products, the central mandrel should also be cooled in conjunction with the cooling of the first and second dies. Cooling the first die face by means of cooling grooves near the lands of the die is acceptable provided that the cooling of the billet is not so excessive as not to increase the extrusion pressure to an unacceptable height. In fact, it is possible to allow some cooling of the die face and to preheat the billet container, ram (or dummy block), and first die face at an acceptable pressure level to extrude the desired material or product. It is preferable to keep it to the minimum necessary. A conical first die can be used to eliminate dead metal zones, and cooling can advantageously reduce the surface temperature of the billet as it approaches the lands of the die. Alloys that are sensitive to thermal brittleness may be treated by reducing the extrusion rate or by increasing the billet preheat temperature to the extent necessary to maintain the temperature of the extruded product, at least its surface temperature, below the solidus temperature of its lowest molten phase. This has led to extrusion problems associated with lowering. Metals based on copper, magnesium, zinc and aluminum are particularly sensitive to thermal embrittlement. In particular, the 2000 and 7000 series aluminum alloys are representative examples, and the extrusion of these alloys is significantly facilitated by the present invention. For example, extrusion speeds at least 4 to 5 times faster than conventional ones can be used to produce products with good surface finish. Referring to FIG. 1, a cooled double extrusion (CDR) die 3 according to the invention is positioned relative to an extrusion apparatus comprising an extruder vessel 1 (holding a billet 15) and a ram section 2. shown as something. The CDR die 3 is a first extrusion die 4,
Cooling groove 1 with second extrusion die 6, die block 13, inlet 11 and outlet 12 for cooling fluid
Including 0. The first die 4 and the second die 6 are
a first die face 9 and a second die face 1 which are flat, respectively;
4, a land 5 of the first die, and a land 7 of the second die. The second extrusion die 6 may have a relief section 8 . The first and second dies are integral and generally coaxial. As shown in FIG. 2, the die face may be tapered, although the taper angle is not critical. 45 in the drawing
Although an included angle of 30 degrees and 30 degrees is shown as an example, the die surface may be tapered to some extent as desired. Practically, it is preferable that the included angle of the first die surface is approximately 45 degrees to 180 degrees, and the included angle of the second die surface is approximately 5 degrees to 180 degrees.
Preferably up to 180 degrees. For primary extrusion of aluminum alloys without lubrication, both die surfaces are preferably flat surfaces (with an included angle of 180 degrees), ie, shear surfaces, as shown in FIG. Other alloys extrude better with a slightly tapered, lubricated die as shown in FIG. 2, as is well known in the art. Also, the surface of the die is preferably curved rather than straight tapered. In both lubricated and non-lubricated extrusion, the first die surface can be tapered, flat, or curved in combination. In particular, a conical and flat surface combination as shown in FIG. The taper reduces or eliminates the metal zone to minimize billet temperature increases due to friction and internal shear in the dead metal zone. The remainder of the first die face downstream may be a flat (shear) surface 24 or may be slightly tapered depending on the particular requirements of the particular product or billet material. Although Figures 1 through 4 only show a direct extrusion method in which the ram moves relative to the container and die, the present invention provides an indirect extrusion method in which the die and hollow ram move relative to the container. It can also be used in extrusion methods.
For indirect extrusion, the only modification is to cool the die via the hollow ram. Referring again to FIG. 1, a typical extrusion ratio of billet 15 to primary extruded product 16 is conventional and is about 4:1 to 500:1;
An extrusion ratio of 40:1 is typical for many alloys included in this invention. The function of the longitudinally extending lands of the first die is to cool the first extruded product, at least its outer surface, to below a critical temperature (the solidus temperature of its lowest molten phase) before extrusion through the second die. The goal is to lower or maintain the temperature. In most cases, and unless otherwise specified, solidus temperature is meant at atmospheric pressure.
However, in some cases, the initial pressure can be increased by raising the original pressure and cooling it below its solidus temperature.
It is sufficient to prevent melting in the second die and provide further cooling in the second die. Friction caused by high extrusion speeds and metal-to-metal contact can temporarily raise the temperature of the primary extruded product above a critical temperature, at least locally near the surface that contacts the first die. As described below, the back pressure generated by the secondary extrusion prevents the generation and growth of circumferential cracks in these high temperature areas until the temperature of the first land reaches a critical level due to cooling. Tend. The ability to maintain or reduce the temperature of the extruded product below a critical level depends, inter alia, on the land length of the first die and, for solid round products, on the length-to-diameter ratio. Depends on. The length of the first die relative to the product thickness is a more accurate determining factor for tubular or thin cross-section products. The land length of the first die should be selected to be as short as possible to reduce friction, yet long enough to control the temperature of the extruded product as required.
In an experiment conducted by the present inventor in which a groove around the land was water-cooled on a solid bar with a diameter of 1.27 cm (0.5 inch), the land length needed to be approximately 2.0-5.0 cm (0.75-2.0 inch). For hot, solid round products,
Length to diameter ratios of between about 1:1 and 12:1, preferably between 1:1 and 5:1, can be used successfully.
Larger ratios provide better cooling, but create excessive friction and extrusion pressure. If the above ratio becomes low, cooling is insufficient and it is necessary to reduce the extrusion speed to prevent cracking due to thermal embrittlement. Appropriate land lengths of the first die can be easily selected for other shapes of products in order to control the temperature below a critical level. The second extrusion die is e.g. about 1.6-3.2mm
For alloy extrusion in the (0.063-0.125 inch) range, a conventional one has a good land. Of course, the shorter the length of the land, the weaker the strength.
Dimensional instability can result, and longer lands can increase friction and cause more surface defects. The second die land has a relief section downstream thereof and is made as short as structurally possible. The second die land can be cooled (and lengthened) if necessary to further reduce the product temperature. The secondary extrusion applies back pressure to the first extrusion die, particularly near the face of the first extrusion die and on the cooled lands of the first die. The cooled land is used to reduce the tensile forces on the first die and to prevent thermal brittleness cracks from starting and growing. The back pressure is also applied to the land surface of the first die to ensure good contact to effectively cool the primary extruded product below the critical temperature before extrusion through the second die. press the alloy material. Furthermore, by maintaining the solidus temperature in the first die section above its value at atmospheric pressure, the back pressure can prevent or reduce melting. Therefore, the back pressure can increase the preheating temperature of the billet above the normal level,
Moreover, it prevents melting at the die portion. Although small amounts of cross-sectional reduction (by shortening the longitudinal dimension) are still useful for secondary extrusion purposes, the cross-sectional area of the primary extruded product can be reduced by 1/4 in the secondary extrusion. It was found that a -60% reduction is within a practical range. A reduction in cross-sectional area of 2-50% is preferred, with 2-15% more preferred. Even if the second die face is tapered, the longitudinal length of the die face and land is preferably minimized to minimize friction. Therefore, with a die with less taper (larger included angle),
Preferably, a larger secondary extrusion is carried out.
Further, if the reduction in cross section is larger or the land is longer, a higher pressure is required, which is not preferable. CDR dies can easily perform multiple extrusions and adapt to a wide range of general extrusion shapes. In particular, Figure 3 shows a design for extrusion of tubular products. Porthole mandrels can also be used, but for seamless pipes,
Using a fixed mandrel with an enlarged part 21, the first
A subsequent extrusion 22 is typically performed to produce the final tubular product 23. Preferably, the mandrel is cooled with fluid flowing through internal grooves (not shown). Of course, it is usual to extrude the extruded product from the billet at a temperature of the billet and an extrudate product temperature that is below the solidus temperature of the lowest molten phase at atmospheric pressure at the exit of the die. However, the inventors have found that using dual extrusion dies and cooling the first extruded product provides advantages in extrusion speed and extrusion pressure. As shown in FIG. 1, the land of the first die can be cooled by a cooling groove 10 located either on the die block 13 or on the outer surface of the dies 4 and 6 and having an inlet 11 and an outlet 12. The cooling groove is shown as a spiral surrounding the first die land. A cooling fluid such as water may be used, or a cryogenic liquid such as liquid nitrogen may be used to shorten the lands of the die. Other conventional cooling devices may be used to indirectly cool the extruded product passing through the first and second dies by removing heat from the lands of the dies. Preferably, cooling begins near the entrance to the first die land. Some cooling of the billet by contacting the face of the first die is useful as long as the cooling of the billet does not increase the extrusion pressure to an unacceptable level. In some cases, for example, for alloy materials that can be temporarily heated in the billet above a critical temperature without causing irreparable damage, the extrusion pressure may be minimized without cooling the billet at the first die face. It is preferable to In such a case, insulation may be provided between die block 13 and billet 15 to maintain a temperature difference therebetween.
The length of the cooling channels, the flow rate of the cooling liquid, the temperature of the cooling liquid and all other parameters are controlled in the usual manner to bring the first extruded product or its outer surface below the critical temperature before the second extrusion. Keep it at the desired temperature. In a preferred method of carrying out the invention, the temperature of the first extruded product, or at least a surface portion thereof, is lowered or maintained at a temperature below the solidus temperature at atmospheric pressure in the lowest melt phase before the second extrusion. cooled down. This cooling may be of such a level that even if heat is generated separately from the secondary extrusion, the temperature does not rise above the solidus temperature at atmospheric pressure. In this case, the die of the secondary extrusion need only be cooled just enough to minimize seizure. If the temperature rises above a critical level, the second die should also cool down sufficiently to prevent the temperature from rising. Since some metals can be irreversibly damaged by melting in the lowest melting phase, the temperature of the billet and die sections should always be kept below the solidus temperature at the original pressure. For other materials, there is little or no permanent damage when the solidus temperature is temporarily exceeded before being cooled below a critical level. Although not preferred, it is possible to cool the primary extruded product to below its solidus temperature at the original pressure (but above its solidus temperature at atmospheric pressure) in the first die before the secondary extrusion. It is possible. Furthermore, although it is possible according to the present invention to utilize a secondary extrusion to prevent or reduce cracking in this condition, if the secondary extruded product is not further cooled, the temperature of the product does not exceed the solidus temperature at the exit of the second die (to atmospheric pressure) and melting occurs.
Therefore, in this condition the second die must be designed to further cool the product. This makes the second die longer, which results in more friction and higher extrusion pressure. As a result, this method is not preferred and it is preferable to cool down to below the solidus temperature at atmospheric pressure in the first die. If CDR die friction can be completely eliminated, the first
Back pressure can be transmitted to the land portion of the die without adversely affecting the primary extruded product. This virtually prevents the formation of cracks. By eliminating or at least minimizing friction, the present invention prevents cracks or, if they do form, reduces the number of cracks that occur.
It is intended to be repaired and recovered in the first die before the next extrusion. Therefore,
Proper lubrication of the die face is desirable to reduce friction. It is normal to polish the lands and faces of the die to less than about 0.25 μm (10 micron inches) rms, preferably about 0.05 μm (2 micron inches).
Surface treated to below rms. It is then lubricated to prevent or minimize metal-to-metal contact at the die and the resulting extruded product from sticking to the face of the die. Lubricants such as graphite or molybdenum dioxide in resin carriers can be used as well as a wide variety of other well known lubricants used in special extrusion alloys. Also, in order to obtain a surface with less tendency for metal seizure from extruded products, e.g. nitriding, chromizing,
Surface treatment or impregnation can be achieved by boronizing. With the exception of the surface treated layers mentioned above, the materials used to make the CDR die are e.g. AISI H-11
Alternatively, it may be a conventional tool steel such as H-13 (hot worked) tool steel. Similarly, it may be made of other suitable materials such as tungsten carbide or other wear resistant materials known to be resistant to seizure from extruded products. Preferred Embodiment Example 1 From a 2024 aluminum alloy billet with a diameter of 7.62 cm (3 inches) to a diameter of 1.27 cm (0.5 inch)
conventional die (land length 2.5 mm, 0.1 inch) and
With an extrusion ratio of 36:1 through both CDR dies,
Several bars with a nominal diameter of 1.27 cm (0.5 inch) were extruded. The diameter of the CDR die is 1.27 cm (0.5 inch) and the land length of the first die is 3.81 cm (1.5 inch).
The secondary extrusion ratio was 10% (cross-sectional area) for a land length of 2.5 mm (0.1 inch). The results under the conditions described above are shown in Table 1. Cooling was performed as shown in FIG. 1 using cooling water at about 5 degrees Celsius. The long rand was polished and lubricated with a molybdenum dioxide based material.

Table: The exit speed commonly practiced for 2024 aluminum bar extrusion is between about 1-1.5 m/min (product speed). Experiments conducted at a billet temperature of 450°C show that good products can be obtained with a normal die at a speed of 1.5 m/min (5 fpm), but at a speed of 7.6 m/min (5 fpm).
min (25fpm), the product shows normal to severe cracking due to high temperature brittleness. 425 at extrusion speed of 18.3m/min (60fpm)
At billet temperatures of 0.degree. C., cracking due to hot brittleness in conventionally extruded products was severe. Conversely, at billet temperatures between 375°C and 450°C
Using CDR dies, products could be produced with little or no cracking due to hot brittleness even at 18.3 m/min. At 475℃, the product showed some thermal brittle cracking in the same series. During experimentation with CDR dies, it was discovered that the nose of the billet around the first die could be excessively cooled by the cooling medium. This appears to cause cracking at higher pressures, creating a poor surface on the extruded product and generally inhibiting the start of each extrusion operation. This excessive cooling of the billet nose can be prevented by starting extrusion before cooling the first die or by providing insulation between the die and the billet.
After cracking, cooling should be adjusted to a level that maintains the critical temperature of the product entering the second die during extrusion. Example 2 It was also discovered during the experiments described above that additional polishing and lubrication improves the results with CDR dies. Friction should be reduced as much as possible. To prove this and show the benefits of double extrusion, we used a CDR die with a secondary extrusion with a 10% cross-section reduction, and two other dies with longer die lands, i.e., one die with a straight Several experiments were conducted using a die with walls and no secondary extrusion, with the other die having converging walls towards the exit end.
The degree of convergence was such that a product with a 1.27 cm (0.5 inch) cross section was gradually reduced by an additional 10% to produce a product with dimensions similar to those produced by the CDR die. The data are shown in Table 2. again
Using A2024 aluminum alloy. The long land on the first die is 0.05μm (2 microinches)
Polished and lubricated to below rms. The lubricant is from Renite Company, Columbus,
Ohio) Renite R-Seal (Renite R-
Seal) AKW. This material was fed into a die with graphite lubricant in an alkaline silicate binder and baked. Although no attempt was made to specify the lubricant, other lubrications may be equally or better.

[Table] Convergent dies (Experiments No. 56 and 61) were used to demonstrate the need to reduce friction contrary to the teachings of German Patent No. 429,376. The convergent die generated pressures so high that no useful product could be obtained under these conditions. Even with a straight die (without secondary extrusion), the friction was too great to produce a product under the conditions of no lubrication (Experiment No. 54) and no special polishing and no lubrication (Experiment No. 51). Even with polishing and lubrication, a straight die will yield 18.3
Products with normal surface cracks were produced globally at a speed of m/min (experiments no. 53, 57, 59 and 62). However, the CDR die according to the present invention produced an overall good product with thin cracks or no cracks except those associated with stray scratch marks. (Experiment number 25, 55, 58
and 60). Routine experimentation with a polished and lubricated CDR can determine the appropriate billet temperature and cooling rate for a particular alloy, as well as an extrusion rate that produces a good product at rates significantly faster than conventional methods. This novel die and extrusion method is preferably used to extrude alloys that are sensitive to thermal embrittlement, and the present invention therefore emphasizes its use in this aspect. However, other materials extrudable by the present invention are also intended to be encompassed, providing a number of other advantages. For example, relatively high melting point metals such as titanium, zirconium, tantalum, tungsten, molybdenum, beryllium and their alloys, steel and copper, and superalloys such as nickel, chromium or cobalt, e.g. Extrusion is typically carried out at elevated temperatures of 100 to 100 mL, which can cause severe wear in dies commonly made from typical hot work tool steels such as AISI, H11, H12, and H13. The present invention improves die life because the die temperature is low in the first and second die parts, and even if the first die wears out like a normal single die, the second die according to the present invention are its initial dimensions, surface finish,
and retains hardness for a longer period of time than the first die.
As the extruded product approaches the second die, the temperature of the product, or at least its surface temperature, is reduced, and the second die itself remains in the die for a much longer period of time than would be possible with a typical single die. Contributes to sustaining the above-mentioned important quality. The improvement in surface finish and dimensional accuracy of extruded products is primarily due to the preservation of these qualities. In this way, a normal single die or
Product surface roughness and/or loss of dimensional accuracy resulting from the normal amount of wear experienced in the first die section of a CDR die is improved by passing through a cooled second die. . Also, by keeping the cross-sectional reduction of the product by the second die relatively small, the pressure generated in the second die is minimized. This further minimizes die wear,
Extends the life of the second die. Additionally, because the second die can size the product extruded from the first die, the second die can be used for more extrusion cycles than is possible with a single conventional die. Additionally, the CDR die allows the use of glass lubricants with lower melting points and lower viscosity than is typically done with conventional high-temperature extrusion of refractory metals and alloys. The use of lower viscosity glasses and grease-type lubricants may be preferable to relatively higher viscosity glasses, although this may promote increased first die wear. This is because highly viscous glasses tend to give the extruded product a rough surface finish. In addition, such high viscosity glass solidifies and accumulates on the cooled land of the first die, thereby causing
Furthermore, it tends to roughen the extruded product surface. However, low viscosity glass or grease type lubricants do not solidify in the cooled first die lands and therefore work very effectively and contribute to improving the surface finish of the extruded product. .

[Brief explanation of drawings]

1 is a sectional view of a cooled die of a double extrusion according to the invention for extruding a solid bar; FIG.
Figure 3 shows a drawing of a die as shown in Figure 1 with tapered first and second die faces; Figure 3 shows a die as shown in Figure 1 with a cooled central mandrel for extruding a tubular product; The cross-sectional view of the die as shown in FIG. 4 is a special embodiment of the die shown in FIG. 1 in which the first die face is a combination of conical and flat. In the figure, 3: double extrusion die, 4: first die, 6: second die, 10: cooling groove, 13:
Dive block, 15: Billet.

Claims (1)

[Claims] 1. A first extrusion die having an elongated land, and a device fixed adjacent to an outlet of the first extrusion die to receive the product extruded from the first extrusion die and measure its cross-sectional area. a second extrusion die that decreases, and a first cooling device that supplies a coolant around the first extrusion die to cool an extended land of the first extrusion die. Dual extrusion die for extruding metal at high extrusion speeds. 2. In the extrusion die according to claim 1, there is provided a second extrusion die for supplying a coolant around the second extrusion die so as to cool the second extrusion die.
An extrusion die comprising a cooling device. 3. The extrusion die of claim 1, wherein the first extrusion die is tapered such that at least a portion thereof has an included angle between about 45 degrees and 180 degrees. An extrusion die comprising a die face. 4. The extrusion die according to claim 1 or 3, wherein the second extrusion die is tapered to have an included angle between about 5 degrees and 180 degrees. An extrusion die characterized in that it includes a surface. 5. In the extrusion die according to claim 1, the land of the first extrusion die is about 0.25.
An extrusion die characterized by being polished to a finishing accuracy of microns RMS or less. 6. The extrusion die according to claim 1 or 5, wherein the land of the first extrusion die is lubricated to reduce friction with the extruded alloy product. 7. In the extrusion die according to claim 1 or 3, the land of the first extrusion die and the first die surface are polished to a finishing accuracy of 0.05 micron rms or less and lubricated. An extrusion die characterized by reducing friction with the extruded alloy product. 8. An extrusion die as claimed in claim 1, in which the elongated land of the first extrusion die has a length between about 1:1 and 12:1 for extruding a solid bar. An extrusion die characterized by having a diameter-to-diameter ratio. 9. In the extrusion die according to claim 1, the second extrusion die is dimensioned to reduce the cross-sectional area of the product extruded by the first extrusion die by 1/4 to 60%. Features an extrusion die. 10. The extrusion die according to claim 1, wherein the land of the first extrusion die is straight or widens toward the outlet. 11 a. extruding a first extruded product from a billet through a first extrusion die having an elongated land; b. cooling at least a portion of the outer surface of said first extruded product in said elongated land before the second extrusion; c. reducing or maintaining its temperature below the solidus temperature at atmospheric pressure of the lowest molten phase; c. extruding the first extruded product through a second extrusion die; the extruded product contacting the elongated land of said first extrusion die and applying back pressure to the alloy in said first extrusion die sufficient to reduce the tensile stress thereof. and/or a method of extruding products from a metal billet at low extrusion pressures. 12. In the method according to claim 11, the temperature of at least the outer surface portion of the product extruded from the second extrusion die is equal to or lower than the solidus temperature at atmospheric pressure in the lowest melt phase after the second extrusion die. The extrusion method further comprises cooling the second extrusion die so that the second extrusion die is maintained at . 13. The method of claim 11, including lubricating the land of the first extrusion die to reduce friction prior to extrusion. 14. The extrusion method according to claim 11, characterized in that the cooled first extruded product is reduced in cross-sectional area by 1/4-60% by a second extrusion. 15. A method according to claim 14, characterized in that the cooled first extruded product is reduced in cross-sectional area by 2-50% by a second extrusion. 16. The method of claim 11, wherein fluid circulates through a cooling groove surrounding an elongated land of the first extrusion die so that the first extruded product is indirectly An extrusion method characterized by cooling. 17. The method of claim 11, wherein the elongated land of the first extrusion die has a length to diameter between about 1:1 and 12:1 for extruding the solid bar. An extrusion method characterized by having a ratio of 18 a Extrude the primary extruded product from the billet through a first extrusion die having an elongated land, and inside the first extrusion die, the first extrusion product is
creating an elevated original pressure in the secondary extruded product; b cooling at least an external surface portion of the primary extruded product in the land; c. maintaining said primary extruded product in contact with said first elongated land by extruding the cooled primary extruded product through a second extrusion die; and apply sufficient backpressure to the original pressure of the alloy in said first extrusion die to reduce the tensile stresses therein, d such that the temperature of at least the outer surface portion is at least as high as in the lowest melt phase after the second extrusion. Faster than conventional speeds and/or lower extrusion pressures, including cooling the extruded product in a second extrusion die below its solidus temperature at atmospheric pressure, while maintaining a good surface finish A method of extruding products from a heated billet of alloys that are sensitive to thermal brittleness. 19. A method according to claim 18, characterized in that the cooled first extruded product is reduced in cross-sectional area by 1/4-60% by a second extrusion. 20. The method of claim 18, wherein the lands and die faces of the first and second extrusion dies are polished to a finish accuracy of about 0.05 microns rms or less and lubricated to reduce friction. An extrusion method further comprising: