GB2089704A - Indirect extrusion press with billet piercing - Google Patents

Abstract

A billet container 4 behind the platen 1 of an indirect extrusion press has a billet-receiving passage 5 through it and is movable toward and away from the platen. A billet-piercing mandrel 8 is slidably mounted in a tubular extrusion stem 6 behind the container. During upsetting and piercing of a billet 20 a stationary plug 17 fills the front end of the container passage. As the mandrel pierces the billet the container is free to be moved rearwardly by billet metal tightly engaging it and moving rearwardly around the mandrel, after which the plug is replaced by an extrusion die 12, through which the pierced billet is extruded around the mandrel by the extrusion stem to form a forwardly moving extruded tube. <IMAGE>

Description

SPECIFICATION Indirect extrusion press with billet piercing This invention relates to indirect extrusion presses and more particularly to such presses that include billet piercing.

The present invention consists in an indirect extrusion press for extruding tubes, a platen, a billet container behind the platen with a billet-receiving passage through it and movable toward and away from the platen, a tubular extrusion stem behind the container movable forward into the container passage, a billet piercing mandrel slidably mounted in said stem and projectable forward therein through said passage, a stationary plug filling the front end of said passage during upsetting and piercing of a billet, said container being free to be moved rearwardly by billet metal engaging it and moving rearwardly around the mandrel as the mandrel moves forward through the billet, and means for replacing said plug with an extrusion die when the mandrel has pierced a billet far enough to leave only a thin metal slug in front of the mandrel, the mandrel then being movable further forward to insert its front end in the die and eject said slug from the billet, and the extrusion stem being movable forward around the mandrel to extrude the pierced billet through the die to form a forwardly moving tube.

In the piercing and indirect extrusion of brass billets to form tubes, for example, a thin shell is formed that contains the impurities that were in the surface of the billet so that the impurities will not enter the extrusion. The die is smaller than the passage through the container to permit the shell to pass the die. When a hot billet is placed in the container it rests on the bottom of the container passage, leaving a crescent-shape clearance above it. Heretofore, in upsetting the billet against the die to fill out the container passage, the die was lifted by the friction of the metal flowing up into the clearance just mentioned. This caused the die to move off center, with the result that a considerable length of the tube being extruded had a non-uniform wall thickness and had to be cropped and discarded as waste.

During piercing in conventional extrusion presses the metal does not flow back around the mandrel very well, if at all, and this is particularly true of hard aluminum alloy billets. Consequently, high piercing force is required and there is considerable scrap loss, especially with large diameter mandrels, due to the length of the slug in front of the mandrel.

It is thus possible to provide an indirect extrusion press for extruding tubes, in which scrap is reduced, in which the piercing force also is reduced, in which the piercing speed is increased and in which there is increased concentricity of the front end portion of the tube being extruded.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which it is shown somewhat schematically.

Figure 1 is a horizontal section showing the press just after a solid billet has been placed in the container; Figure 2 is a veiw taken on the line ll-ll of Figure 1; Figure 3 is a vertical section through the center of the billet container with a solid plug in front of the billet; Figures 4, 5, 6 and 7 are views similar to Figure 3 at successive stages in the piercing of the billet; Figure 8 likewise is a vertical section through the center of the billet container but showing a die in front of the billet; Figures 9 and 10 are views similar to Figure 8 at successive stages in the piercing of the billet; Figure 7 1 is a vertical section similar to Figure 8 but showing the position of the apparatus at the conclusion of the extruding operation; and Figures 12to 16 are horizontal sections through the center of a billet container showing a modified system of piercing a billet.

Referring to Figures 1 and 2 of the drawings, an extrusion press platen 1 is provided with a slide 2 that can be moved back and forth across its rear face in any suitable manner, such as by a hydraulic cylinder (not shown). Atubular die stem 3 projecting behind the platen is secured at its front end to the slide. The slide is provided with a passage through it in line with the stem and alignable with a passage through the platen to allow an extrusion to pass through them and emerge from the front of the platen. Behind the die stem there is a billet container 4 provided with a billet-receiving passage 5 therethrough in line with the die stem.The container can be moved in a well-known manner toward and away from the platen. Atubular extrusion stem 6 behind the container is movable forward into the container passage in a known manner by a hydraulical!y operated ram 7. Disposed in the extrusion stem is a piercing mandrel 8 that can be moved forward relative to the stem in conventional manner.

Slidablymounted in any suitable mannerfor movement back and forth across the front of the container is a die slide 9 that travels between upper and lower tracks 10 and 11 supported bythe container. When the slide is in operating position, as shown in Figure 8, a die 12 disposed in a capsule 13 mounted in the opening that extends through the slide from front to back is disposed in front of the container passage. The diameter of the die is somewhat less than the diameter of the container passage and of the inside of a second capsule 14 that receives the dummy block and extrusion butt after completion of extrusion.

Mounted between the tracks and disposed at one side of the die slide, as shown in Figures 1 and 2, is a plug slide 16 that contains a solid metal plug 17. The plug projects a short distance from the front of the slide so that it can engage the die stem when the plug and die stem are aligned with the container passage. The rear or inner end of the plug is the same size as container passage 5 and will fit it snugly when it enters the passage, as shown in Figures 4 and 5. The plug is slidable forward and backward in the slide, forward movement being limited by engaging annular shoulders 18.

As shown in Figure 1, the die stem, die slide and plug slide are moved to one side of the container to permit a hot billet 20 to be inserted in the container passage by any suitable means, such, for example, as disclosed in my copending patent appiication Serial No. 183,230, filed September 2, 1980. Then the die stem and plug slide are moved into operating position to align the stem and plug with the container passage as shown in Figure 3. Following this, as shown in Figure 4, the ram 7 is moved forward to insert the front end of the mandrel in a dummy block 21 that will fit the container passage closely, and to cause the extrusion stem to push the dummy block into the container passage and up against the billet, which will push the plug against the end of the die stem.The container is moved forward at the same time relative to the stationary plug by conventional container-moving means (not shown) to move the plug slide 16 forward on the plug. Enough pressure is exerted by the ram to upset the billet against the plug to fill out the container passage. The ram 7 and extrusion stem 6 then are retracted, but the dummy block and mandrel remain against the billet.

The next step is to move the mandrel forward to start piercing the billet as shown in Figure 5. The container is free at this time to move rearwardly at the same time, which it does due to the billet metal moving rearwardly around the forwardly moving mandrel and tightly engaging the wall of the container passage as shown in Figure 6. In other words, as the mandrel moves forward in the billet, the container is moved backward in the opposite direction, with the result that piercing is carried out more rapidly than when the container is held stationary, and with the use of less force exerted by the ram because the metal of the billet moving rearwardly around the mandrel does not have to slide against the encircling container, so there is no sliding friction between them.

As also shown in Figure 6, forward movement of the mandrel through the billet is stopped just before the mandrel reaches plug 17. This leaves a thin layer or slug of metal between the mandrel and the plug.

The ram and the container, with the slides carried by the container, then are moved backward to separate the front end of the plug from the die stem 3 as shown in Figure 7. Following this, the plug slide 16 is moved laterally away from the container passage 5 and the die slide 9 is moved into operating position as shown in Figure 8. Then the ram is advanced to cause the die slide to move forward over the die stem (Figure 9) until the billet engages the die and presses it against the die stem. The mandrel 8 then is advanced again to complete the piercing of the billet by breaking away the slug 23 and pushing it into the die as indicated in Figure 10. The mandrel is stopped with its front end inside the die.

The press now is in position for extruding the billet, which, as shown in Figure 11, is done by advancing the extrusion stem around the mandrel to force the billet metal forward between the front end of the mandrel and the die to form a forwardly moving tube 24. During this operation, the frictional engagement of the billet with the container moves the container forward also, as is customary with indirect extrusion. The extrusion step centers the die in the container passage so that there is clearance all the way around the die. Some of the billet metal is forced through this clearance to form a shell 25 that will contain any surface imperfections that were in the billet.

In the modification shown in Figures 12 to 16, two laterally spaced stems 30 and 31 extend rearwardly from a slide 32 movable back and forth across the back of an extrusion press platen 33. Stem 30 is a die stem, to the rear end of which a die 34 can be attached. A plug 35 is held against the rear end of the other stem by means of a rod 36 extending through the stem and attached to the platen slide. The diameter of the plug is the same as the inside diameter of the billet-receiving passage through the container 37. While the container is retracted, the platen slide is moved laterally to line up the plug with the container passage, in which a billet 38 has already been inserted.Then, as shown in Figure 12, as the container is moved forward around the plug, an extrusion stem 39, mandrel 40 and dummy block 41 are moved forward into the container passage by the usual ram 42 to upset the billet against the plug.

Following this, the ram and extrusion stem are retracted but the mandrel and dummy block remain against the billet as shown in Figure 13. A space is thus formed between the dummy block and extrusion stem.

Then the mandrel is moved forward relative to the stem and block to pierce billet as shown in Figure 14.

As the billet metal flows rearwardly around the mandrel, the metal carries the container with it.

Piercing is stopped temporarily just before the mandrel reaches the plug, and then the ram and container are retracted to move the container away from the plug so that the platen slide can be shifted to align the die stem and die with the container passage as shown in Figure 15. The ram then advances again to cause the billet to engage the die, followed by advancement of the mandrel through the thin end of the billet and into the die as shown in Figure 16. Further advance of the ram, with the mandrel stationary, causes the extrusion stem to extrude the billet through the die to form a tube in the same manner as illustrated in Figure 11 of the first embodiment of the invention.

Claims (6)

1. In an indirect extrusion press for extruding tubes, a platen, a billet container behind the platen with a billet-receiving passage through it and movable toward and away from the platen, a tubular extrusion stem behind the container movable forward into the container passage, a billet piercing mandrel slidably mounted in said stem and projectable forward therein through said passage, a stationary plug filling the front end of said passage during upsetting and piercing of a billet, said container being free to be moved rearwardly by billet metal engaging it and moving rearwardly around the mandrel as the mandrel moves forward through the billet, and means for replacing said plug with an extrusion die when the mandrel has pierced a billet far enough to leave only a thin metal slug in front of the mandrel, the mandrel then being movable further forward to insert its front end in the die and eject said slug from the billet, and the extrusion stem being movable forward around the mandrel to extrude the pierced billet through the die to form a forwardly moving tube.

2. In the extrusion press recited in claim 1, a tubular die stem holding said plug stationary during billet upsetting and piercing.

3. In the extrusion press recited in claim 2, a die slide and a plug slide movable back and forth across the front of said container, said plug and die being mounted in laterally spaced relation in said slides for selective positioning between said die stem and container passage.

4. In the extrusion press recited in claim 1, said plug-replacing means including a platen slide mounted on the back of said platen, plug-holding means secured to said slide and extending rearwardly therefrom, and a die stem spaced laterally from said plug-holding means, said slide being movable back and forth across the platen to selectively align said plug and die with said container passage.

5. In the extrusion press recited in claim 1, said container being movable forward and backward relative to said plug and die.

6. An extrusion press substantially as hereinbefore described with reference to and illustrated in the accompanying drawings.