Patent Grant
9975160
The present invention relates to a metal extrusion and in particular, to an extrusion press container and a liner for same related to metal extrusion.
Metal extrusion presses are well known in the art, and are used for forming extruded metal products having cross-sectional shapes that generally conform to the shape of the extrusion dies used. A typical metal extrusion press comprises a generally cylindrical container having an outer mantle and an inner tubular liner. The container serves as a temperature controlled enclosure for a billet during extrusion. An extrusion ram is positioned adjacent one end of the container. The end of the extrusion ram abuts a dummy block, which in turn abuts the billet allowing the billet to be advanced through the container. An extrusion die is positioned adjacent the opposite end of the container.
During operation, once the billet is heated to a desired extrusion temperature (typically 800-900° F. for aluminum), it is delivered to the extrusion press. The extrusion ram is then activated to abut the dummy block thereby to advance advancing the billet into the container and towards the extrusion die. Under the pressure exerted by the advancing extrusion ram and dummy block, the billet is extruded through the profile provided in the extrusion die until all or most of the billet material is pushed out of the container, resulting in the extruded product.
In order to attain cost-saving efficiency and productivity in metal extrusion technologies, it is important to achieve thermal alignment of the extrusion press. Thermal alignment is generally defined as the control and maintenance of optimal running temperature of the various extrusion press components. Achieving thermal alignment during production of extruded product ensures that the flow of the extrudable material is uniform, and enables the extrusion press operator to press at a higher speed with less waste.
As will be appreciated, optimal billet temperature can only be maintained if the container can immediately correct any change in the liner temperature during the extrusion process, when and where it occurs. Often all that is required is the addition of relatively small amounts of heat to areas that are deficient.
A number of factors must be considered when assessing the thermal alignment of an extrusion press. For example, the whole of the billet of extrudable material must be at the optimum operating temperature in order to assure uniform flow rates over the cross-sectional area of the billet. The temperature of the liner in the container must also serve to maintain, and not interfere with, the temperature profile of the billet passing therethrough.
Achieving thermal alignment is generally a challenge to an extrusion press operator. During extrusion, the top of the container usually becomes hotter than the bottom. Although conduction is the principal method of heat transfer within the container, radiant heat lost from the bottom surface of the container rises inside the container housing, leading to an increase in temperature at the top. As the front and rear ends of the container are generally exposed, they will lose more heat than the center section of the container. This may result in the center section of the container being hotter than the ends. As well, the temperature at the extrusion die end of the container tends to be slightly higher compared to the ram end, as the billet heats it for a longer period of time. These temperature variations in the container affect the temperature profile of the liner contained therein, which in turn affects the temperature of the billet of extrudable material. The temperature profile of the extrusion die generally conforms to the temperature profile of the liner, and the temperature of the extrusion die affects the flow rate of extrudable material therethrough. Although the average flow rate of extrudable material through the extrusion die is governed by the speed of the ram, flow rates from hotter sections of the billet will be faster compared to cooler sections of the billet. The run-out variance across the cross-sectional profile of a billet can be as great as 1% for every 5° C. difference in temperature. This can adversely affect the shape of the profile of the extruded product. Control of the temperature profiles of the liner and of the container is therefore of great importance to the efficient operation of the extrusion process.
Other challenges arise when the liner passage is non-circular. For example, liners having a rectangular passage, referred to as “rectangular liners”, are used for extruding shapes having generally flat profiles. A conventional approach to forming a rectangular liner involves inserting a pair of liner inserts into an otherwise circular liner. For example,
Such “multiple-piece” rectangular liners are known to have drawbacks. For example, stress cracks readily form in the liner 14 along the corners of the rectangular passage during use, which in turn can propagate into the mantle 12, particularly around the vicinity of bolts 19. Additionally, dead metal zones can form at the corners of the rectangular passage, causing metal impurities to be deposited at the corners of the passage. These impurities can be transferred to the extruded product, resulting in an increase in the amount of scrap of extruded product.
Single-piece rectangular liners have been previously considered. For example, U.S. Pat. No. 3,892,114 to Taniguchi et al. discloses a container for use in an extrusion press of the type comprising an inner cylinder having a noncircular opening and an outer cylinder applied about the inner cylinder by shrinkage fit. A plurality of circumferential recesses are provided for the inner or outer cylinder at the interface between them at portions corresponding to the portions of the noncircular opening having small pressure receiving areas. The recess has a predetermined radial depth and extends along the entire axial length of the inner and outer cylinders.
Prior art single-piece rectangular liners typically have high failure rates owing to increased stresses in the liner at the corners of the rectangular passage. This failure typically takes the form of cracking in the liner in the vicinity of these corners. These cracks can eventually propagate from the liner into the mantle, necessitating replacement of both the liner and the mantle and resulting in costly downtime.
Some approaches to resolving the issue of cracking in single-piece rectangular liners have also been previously considered. For example, U.S. Pat. No. 4,007,619 to Ames et al. discloses a container for an extrusion press comprising a liner space having its shape defined by at least one, if desirable several, component parts in which in the liner wall where the highest stresses arise there is provided at least one groove or similar recess. The at least one groove runs approximately in the extrusion direction, and is filled and sealed with a weld which behaves elastically during extrusion. The intrusion of extruded metal into the gaps is thus prevented and a longer lifetime of the container is achieved.
As will be appreciated, improvements to address the problems discussed above are generally desired. It is therefore an object of the present invention at least to provide a novel extrusion press container and a liner for same.
Accordingly, in one aspect there is provided a liner for use in a metal extrusion press, the liner comprising: an elongate body having a longitudinally extending passage therein through which a billet is advanced, the passage having a generally rectangular cross-sectional profile; and at least one first longitudinally extending heating element accommodated by the body adjacent a first side of the passage and at least one second longitudinally extending heating element accommodated by the body adjacent a second side of the passage, the first and second heating elements being individually controllable for controlling a thermal profile within the liner.
The generally rectangular cross-sectional profile of the passage may have a width defining a transverse axis, the first and second heating elements being positioned on opposite sides of the transverse axis. The first and second heating elements may be arranged in at least one row adjacent the passage. The at least one row may be parallel to the transverse axis.
The liner may further comprise at least one first longitudinally extending temperature sensor adjacent the first side of the passage and at least one second longitudinally extending temperature sensor adjacent the second side of the passage. The at least one first temperature sensor may be positioned between the at least one first heating element and the passage. The at least one second temperature sensor may be positioned between the at least one second heating element and the passage. The first and second temperature sensors may be thermocouples.
The generally rectangular cross-sectional profile may comprise rounded corners. The generally rectangular cross-sectional profile may comprise rounded sides. The generally rectangular cross-sectional profile may comprise flared ends.
At least one of the first and second heating elements may comprise at least one heating section.
Each of the first and second heating elements may comprise two heating sections positioned towards each relative end of the heating element.
In another aspect, there is provided a container for use in a metal extrusion press, the container comprising: an outer mantle configured for connecting to an extrusion press and having a central axial bore therein; and a liner comprising an elongate body having a longitudinally extending passage therein through which a billet is advanced, the passage having a generally rectangular cross-sectional profile, and at least one first longitudinally extending heating element accommodated by the body adjacent a first side of the passage and at least one second longitudinally extending heating element accommodated by the body adjacent a second side of the passage, the first and second heating elements being individually controllable for controlling a thermal profile within the liner.
The generally rectangular cross-sectional profile of the passage may have a width defining a transverse axis, the first and second heating elements being positioned on opposite sides of the transverse axis. The first and second heating elements may be arranged in at least one row adjacent the passage. The at least one row may be parallel to the transverse axis.
The container may further comprise at least one first longitudinally extending temperature sensor adjacent the first side of the passage and at least one second longitudinally extending temperature sensor adjacent the second side of the passage. The at least one first temperature sensor may be positioned between the at least one first heating element and the passage. The at least one second temperature sensor may be positioned between the at least one second heating element and the passage. The first and second temperature sensors may be thermocouples.
The generally rectangular cross-sectional profile may comprise rounded corners. The generally rectangular cross-sectional profile may comprise rounded sides. The generally rectangular cross-sectional profile may comprise flared ends. At least one of the first and second heating elements may comprise at least one heating section.
Each of the first and second heating elements may comprise two heating sections positioned towards each relative end of the heating element.
The mantle may comprise a plurality of additional longitudinally extending heating elements adjacent the liner. The plurality of additional longitudinally extending heating elements may be arranged circumferentially about an axial bore of the mantle.
Embodiments will now be described more fully with reference to the accompanying drawings in which:
During operation, once the billet 131 is heated to a desired extrusion temperature (typically 800-900° F. for aluminum), it is delivered to the extrusion press. The extrusion ram 133 is then actuated to abut the dummy block 134, thereby to advance the billet 131 into the container and towards the extrusion die 137. Under the pressure exerted by the advancing extrusion ram 133 and dummy block 134, the billet 131 is extruded through the profile provided in the extrusion die 137 until all or most of the billet material is pushed out of the container 130, resulting in the extruded product 139.
At the ram end 140 of the mantle 132, an annular recess 142 for passage of bus lines (not shown) is provided in the interior surface of the mantle. The ram end 140 is further configured to accommodate cover plates to protect the bus lines accommodated by the channel. Within the annular recess 142, there is provided a plurality of longitudinal bores 144 extending the length of the mantle 132. The longitudinal bores 144 are positioned circumferentially about the axial bore of the mantle that accommodates the liner 136. Each longitudinal bore 144 is shaped to accommodate an elongate heating element 146 that can be energized to provide thermal energy to the mantle 132 and to the liner 136 during use.
The liner 136 is better illustrated in
In this embodiment, container 130 also comprises a pair of longitudinal bores 162a and 162b extending partially into the length of the liner 136. Each longitudinal bore 162a and 162b is provided within a centrally located deviation of the channels 159, and is shaped to accommodate a temperature sensor (not shown). The longitudinal bores 162a and 162b are positioned in a manner so as to avoid intersecting any of the longitudinal bores 158, and in the embodiment shown, the longitudinal bores 162a and 162b are positioned on opposite sides of the transverse axis T of the passage 150, and each longitudinal bore 162a and 162b is centrally located and is positioned between the longitudinal bores 158 and the passage 150. The longitudinal bores 162a and 162b extend from the ram end 140 to approximately four (4) inches from the die end 138 of the liner 136. As will be appreciated, terminating the longitudinal bores 158, 162a and 162b at a distance from the die end 138 of the liner 136 advantageously strengthens the liner 136.
The elongate heating elements 146 are cartridge-type elements, as shown in
To monitor the temperature of the extrusion process, temperature sensors (not shown) are used. In this embodiment, the temperature sensors are thermocouples. Each sensor comprises two sensing elements (not shown), one sensing element for placement in the front zone 145a of the liner 136, and the second sensing element for placement in the rear zone 145b. The sensors feed into the controller, providing the operator with temperature data from which subsequent temperature adjustments can be made.
In use, the liner 136 is oriented such that the transverse axis T of passage 150 is generally horizontal. In this orientation, rows 160a and 160b of longitudinal bores 158 accommodating the elongate heating elements are situated above and below the passage 150, respectively, and the longitudinal bores 162a and 162b accommodating the temperature sensors are situated above and below the passage 150, respectively. As will be appreciated, the positioning of temperature sensors both above and below the passage 150 advantageously allows the vertical temperature profile within the liner 136 to be measured, and moreover allows any vertical temperature difference across the passage 150 that arises during extrusion to be directly monitored by the operator. The positioning of elongate heating elements both above and below the passage 150 advantageously allows any measured vertical temperature difference to be reduced or eliminated by increasing the thermal energy supplied by elongate heating elements 146 positioned within row 160b below the passage 150, or by reducing the thermal supplied by elongate heating elements 146 positioned within row 160a above the passage 150, or by both. As each of the heating elements within the rows 160a and 160b are individually controllable, the thermal profile within the liner can be accurately controlled.
Those skilled in the art will appreciate that accurately controlling the thermal profile of the liner also allows the thermal profile of the extrusion die to be indirectly controlled, as the container and the extrusion die are in general thermal communication with each other by thermal conductance.
Additionally, the arrangement of the longitudinal bores 158 in rows 160a and 160b advantageously allows the thermal energy to be evenly distributed along the transverse axis T of the passage 150, which thereby improves the temperature uniformity across the width of the passage 150.
Those skilled in the art will appreciate that the inclusion of flared ends 152, rounded corners 154 and rounded sides 156 in the cross-sectional profile of the passage 150 advantageously reduces localized stresses in the liner 136 near the corners of the passage 150. This reduction in localized stresses reduces cracking in the liner in the vicinity of these corners. Such cracks can eventually propagate from the liner into the mantle, necessitating replacement of both the liner and the mantle and resulting in costly downtime. Accordingly, the cross-sectional profile of the passage 150 comprising flared ends 152, rounded corners 154 and rounded sides 156 enables the usage life of both the liner 136 and the mantle 132 to be extended.
It will be understood that the liner is not limited to the configuration described above, and in other embodiments, the liner may alternatively have other configurations. For example, the liner may alternatively comprise a billet receiving passage having a generally rectangular cross-sectional profile that comprises any of flared ends, rounded corners, and rounded sides.
Although in the embodiments described above, the liner comprises twelve (12) longitudinal bores each for accommodating an elongate heating element, in other embodiments, the liner may alternatively comprise more or fewer longitudinal bores each for accommodating an elongate heating element.
Although in embodiments described above, the longitudinal bores for accommodating elongate heating elements in the liner are arranged in two rows and parallel to, and on opposite sides of, the transverse axis T of the passage, in other embodiments, the longitudinal bores for accommodating elongate heating elements in the liner may alternatively be arranged in other arrangements within the liner.
Although in embodiments described above, the longitudinal bores for the elongate heating elements and the longitudinal bores for the temperature sensors extend partially into the length of the liner, in other embodiments, any of the longitudinal bores for the elongate heating elements and the longitudinal bores for the temperature sensors may alternatively extend the entire length of the liner.
Although in embodiments described above, the elongate heating elements are configured with front heating sections and rear heating sections, in other embodiments, the elongate heating elements may alternatively be configured with additional or fewer heating sections, and/or may alternatively be configured to heat along the entire length of the heating cartridge.
Although in embodiments described above, the elongate heating elements in the vicinity of the lower front zone and the lower rear zone are described as being configured to be controlled by the operator to provide added temperature, it will be understood that these elongate heating elements are also configured to be controlled by the operator to provide reduced temperature. Similarly, although in embodiments described above, the elongate heating elements in the vicinity of the upper front zone and the upper rear zone are described as being configured to be controlled by the operator to provide reduced temperature, it will be understood that these elongate heating elements are also configured to be controlled by the operator to provide added temperature.
Although in embodiments described above, the liner comprises two (2) longitudinal bores for accommodating temperature sensors, in other embodiments, the liner may alternatively comprise more or fewer longitudinal bores for accommodating temperature sensors. In still other embodiments, the liner may alternatively comprise no longitudinal bores and for accommodating temperature sensors, and in such embodiments, the liner may comprise one or more radial bores for accommodating temperature sensors.
Although in embodiments described above, each longitudinal bore for the temperature sensors is positioned between the longitudinal bores for the elongate heating elements and the passage, in other embodiments, one or more of the longitudinal bores for the temperature sensors may alternatively be positioned elsewhere within the liner.
Although in embodiments described above, the temperature sensor contains two sensing elements, in other embodiments, the temperature sensor may alternatively comprise any number of sensing elements.
Although in embodiments described above, in use, the liner is configured to be oriented such that the transverse axis T of the passage is generally horizontal, it will be understood that the liner may alternatively be used with the transverse axis T of the passage oriented in any direction.
Although embodiments have been described above with reference to the accompanying drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the scope thereof as defined by the appended claims.
This application claims the benefit of U.S. Provisional Application No. 61/535,602 to Robbins filed on Sep. 16, 2011 and entitled “Extrusion Press Container and Liner for Same”, the entire content of which is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2960221 | Albers et al. | Nov 1960 | A |
| 3042195 | Muller | Jul 1962 | A |
| 3089591 | Groos | May 1963 | A |
| 3161756 | Haverkamp et al. | Dec 1964 | A |
| 3360975 | Edgecombe | Jan 1968 | A |
| 3364707 | Foerster | Jan 1968 | A |
| 3478562 | Groos | Nov 1969 | A |
| 4007619 | Ames et al. | Feb 1977 | A |
| 4064723 | Larsson et al. | Dec 1977 | A |
| 4882104 | Dobrowsky | Nov 1989 | A |
| 5311761 | Robbins | May 1994 | A |
| 5600990 | Kelly et al. | Feb 1997 | A |
| 7272967 | Robbins | Sep 2007 | B2 |
| 7594419 | Robbins | Sep 2009 | B2 |
| 20050262913 | Robbins | Dec 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 414506 | Jun 1966 | CH |
| 202087620 | Dec 2011 | CN |
| 102007033205 | Feb 2008 | DE |
| 481951 | Apr 1992 | EP |
| 481951 | Apr 1992 | EP |
| 0481951 | Apr 1992 | EP |
| 62-161421 | Jul 1987 | JP |
| 4-274820 | Jun 2009 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20130074568 A1 | Mar 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61535602 | Sep 2011 | US |
