Patent Application
20170066054
The present disclosure relates to compacting of powdered metal, and more particularly relates to a system and a method for compacting powdered metal.
Powder metallurgy has been gaining widespread popularity in the realm of manufacturing processes. Powder metallurgy is a highly developed method of manufacturing precision metal components, and can be understood as a methodology that produces components from metallic powders. Usually, powder metallurgy includes mixing metal powders, compacting or pressing the mixed powders in a die, and sintering the compacted powder for bonding the particles of the compacted powder.
The process of compacting or pressing the mixed powders into a geometrical form is commonly referred to as powder pressing. Generally, the mixed powders are pressed in a press-type machine by using a punch-and-die arrangement at room temperature. In the punch and die arrangement, pressure applied by a press on powders is not focused. This causes non-uniform pressing of the mixed powders which leads to a difference in density that can occur in different parts of the resulting component. Due to such inconsistency in the density of components, manufacturing large components from mixed powders poses a difficulty. Moreover, dimensions of components that can be manufactured from mixed powders are also limited. Further, in order to have higher density of mixed powders in the components, compaction pressure has to be increased substantially which would demand larger presses and stronger tools to withstand such high pressures. Owing to the cost of large presses and stronger tools, the whole process would become uneconomical. Moreover, the traditional techniques involve separate steps for introducing the mixed powders for pressing, pressing the mixed powders, and then releasing the pressed product. Therefore, the entire process would become time-intensive and tedious.
CN Patent Number CN1059303A (the '303 patent) describes a production process for manufacturing powder metallurgy mechanical structure parts. The process includes placing the metal powder into a finished-product shaped mold cavity for pressure-sintering parts so as to make hot-press moulding sintering. Further, the formed moulded blank is put into a precision mold and is placed into a swing-forging machine capable of two-way pressurizing so as to make compaction by cold-forging. Finally, the work piece proceeds for secondary processing.
In one aspect of the present disclosure, a method of making an object from powdered metal is provided. The method includes feeding the powdered metal into a first end of a die, and rotating the die to pull a first portion of the powdered metal into a pressing zone. The method further includes pressing the first portion of the powdered metal using high pressure. Following the pressing of the powdered metal, the die is rotated to release the first portion of the powdered metal from a second end of the die, where the die rotates in one direction only. Further, a second portion of the powdered metal is pulled into the first end of the die.
In another aspect of the present disclosure, a system for compacting powdered metal is provided. The system includes a feeder, a die and a roller. The feeder is configured to feed the powdered metal at a continuous or stepwise rate. The die is configured to receive the powdered metal from the feeder and to rotate about a first axis, where the die rotates in one direction only. The roller is disposed adjacent to the die and is configured to rotate about a second axis in a direction opposite to that of the die.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts.
The powdered metal 108 may be, for example, of any conventional or known powdered metal formulation. The powdered metal 108 may include a single alloyed or unalloyed metallurgical powder or a blend of one or more such powders. In one example, the powdered metal 108 may include, but is not limited to low alloy ferrous materials, stainless steel, copper alloys, aluminum alloys, and titanium alloys.
Further, the powdered metal 108 may also include other metallurgical and non-metallurgical additives or binders. Addition of such additives or binders in the powdered metal 108 is herein referred to as binder treatment or bonding. Binder treatment is performed for reducing segregation as well as for improving flowability, green strength, green density, dimensional change, pressing and ejection of objects. Such binders or additives may include, but are not limited to graphite, metallic alloying elements, carbon, copper, nickel and lubricants. The powdered metal 108 and additives may be selected based on the properties of the objects to be manufactured.
The feeder 102 may feed the powdered metal 108 for pressing operation. In one embodiment, the feeder 102 may be configured to feed the powdered metal 108 at a continuous rate. In an alternate embodiment, the feeder 102 may be configured to feed the powdered metal 108 at a stepwise rate. In such an embodiment, the powdered metal 108 may be fed for a predefined duration of time and then the feeder 102 would stop feeding the powdered metal 108 for another predefined duration of time before feeding the powdered metal 108 again. For example, the feeder 102 may feed the powdered metal 108 for 15 seconds and then may stop feeding the powdered metal 108 for the following 10 seconds. After 10 seconds, the feeder 102 may resume feeding the powdered metal 108 for the pressing operation.
Further, the feeder 102 may feed the powdered metal 108 into the die 104 either automatically or manually. In the present embodiment, the feeder 102 is a hopper that may receive the powdered metal 108 from a supply source (not shown). The hopper may then feed the powdered metal 108 to the pressing zone 110 between the die 104 and the roller 106 for pressing. In one embodiment, the hopper may be vibrating for inducing flow of the powdered metal 108. Other feeding mechanisms that are already known in the art can also be employed for feeding the powdered metal 108 for the pressing operation.
The powdered metal 108 fed by the feeder 102 may be received by the die 104. The die 104 may include a first end 112 and a second end 114. In some embodiments, feeder 102 feeds the powdered metal 108 into the first end 112 of the die 104. In certain embodiments, the first portion of the powdered metal 108 is released from the second end 114 of the die 104 after the pressing operation.
In the present embodiment, the die 104 is an internal roller. Further, since the object to be manufactured is a ring gear, the geometry of the die 104 allows for the formation of a ring gear. Therefore, as can be seen, the die 104 includes teeth 116 along an outer edge 118. The dimensions of the die 104 can be adjusted according to the dimensions of the object, i.e., the ring gear. In one embodiment, the die 104 may include a joint 122. In some embodiments, joint 122 may be a preformed sinter lock joint. The preformed sinter lock joint can allow formation of a physical shape that in turn, can allow the start and stop location of, e.g., the ring gear, to be mechanically connected prior to sintering, such that a strong bond is created at the location during sintering. In certain embodiments, joint 122 may be a start-stop joint.
The roller 106 may be disposed adjacent to the die 104. The gap or the distance between the die 104 and the roller 106 may be adjusted to generate the corresponding dimensions of the object. In one example, the distance between the die 104 and the roller 106 is about 3-140 millimeters (mm). Moreover, the distance between the die 104 and the roller 106 may vary based on various operating conditions. Such operating conditions may include, but are not limited to dimensions of the die 104, dimensions of the roller 106, pressure to be applied, type of powdered metal 108, dimensions of the final product, geometry of the final product, and geometry of the die 104 and geometry of the roller 106.
In order to produce a pressed metal unit 124, i.e., the product that is obtained after pressing the powdered metal 108, the die 104 and the roller 106 may rotate about a first axis XX and a second axis XX′, respectively. The die 104 is allowed to rotate in one direction only. The roller 106 may rotate about the second axis XX′ in a direction opposite to the rotation of the die 104. The relative rotation of the die 104 and the roller 106 may allow for multiple functions to be accomplished simultaneously. For example, the relative rotation may pull the powdered metal 108 from the feeder 102, press the powdered metal 108 to obtain the pressed metal unit 124 and then release the pressed metal unit 124.
In one embodiment, the die 104 may continuously rotate about the first axis XX. For example, the die 104 may move continuously for more than one complete rotation. The continuous rotation would allow for continuous formation of the pressed product. In another embodiment, the die 104 may rotate about the first axis XX in a semi-continuous manner. For example, the die 104 may move semi-continuously for one complete rotation or less.
The process of manufacturing being offered by the system 100 can be either a continuous process or a semi-continuous process. For example, in the semi-continuous process of manufacturing the object, the feeder 102 may feed the powdered metal 108 to the die 104 at a stepwise rate and the die 104 may rotate about the first axis XX in a semi-continuous manner. The operation of the feeder 102 and the die 104 may be synchronized in a manner that both the feeder 102 and the die 104 may start and stop at the same time. In one example, the die 104 may rotate to complete one rotation at a time. Therefore, during each rotation, the powdered metal 108 may be pressed between the die 104 and the roller 106 to produce one pressed metal unit 124, as shown in
In such a case, a longer strip of pressed powdered metal 108 may be obtained than that obtained, for example, in the semi-continuous process. The longer strip may include a plurality of identical pressed metal units 224 similar to the object to be manufactured. For example, in the present embodiment, the continuous process may produce a spiral product that can be further processed, for example, by cutting at appropriate locations to generate a plurality of identical planar products as final objects. Therefore, the continuous process may be used for bulk production of the objects.
In one example, the feeder 102, the die 104, 204 and the roller 106 may be of stainless steel. Further, the die 104, 204 and the roller 106 are of high strength and wear resistant material.
The present disclosure relates to the system 100, 200 for compacting powdered metal 108. The system 100, 200 may include the feeder 102, the die 104, 204 and the roller 106 for compacting the powdered metal 108 for producing pressed metal units 124, 224 similar to the objects to be manufactured, that may further be sintered or subjected to secondary processing. The system 100, 200 allows for pressing of the powdered metal 108 by using a continuous process and a semi-continuous process. The continuous process may allow bulk production of the objects from the powdered metal 108 by producing a strip of identical pressed metal units 124, 224. Further, the semi-continuous process may produce one pressed metal unit 124 at a time. The pressed metal units 124, 224 so produced can then be sintered for obtaining the objects as the final product. The present disclosure also relates to a method 300 of making an object from powdered metal 108.
At step 304, the method 300 includes rotating the die 104 to pull a first portion of the powdered metal 108 into the pressing zone 110. The die 104 is allowed to rotate in one direction only. The pressing zone 110 can be understood as the region between the die 104 and the roller 106 where the powdered metal 108 is being pressed. For example, the powdered metal 108 is pressed between the die 104 and the roller 106 in the pressing zone 110. In one embodiment, the die 104 can be rotated continuously. In another embodiment, the die 104 can be rotated semi-continuously.
At step 306, the first portion of the powdered metal 108 may be pressed using high pressure. In one embodiment, the powdered metal 108 may be pressed under focused pressure at a high compression rate to form pressed metal units 124 having a near uniform density. In one example, the powdered metal 108 may be pressed from 10-100 tons per square inch (tsi) within a duration of 1-10 seconds. In another example, the powdered metal 108 is pressed at a temperature between 20-200° C.
The first portion of the powdered metal 108 may be pressed in the pressing zone 110 between the die 104 and the roller 106 that is placed adjacent to the die 104. The die 104 and the roller 106 may be rotating in a direction opposite to each other for producing the pressed metal units 124 by pressing the powdered metal 108. In one example, the ramp rate of pressure to be applied on the first portion of the powdered metal 108 can vary between 10-100 tsi in 1-10 seconds. For example, each unit area of the first portion may be pressed for a total of 10 seconds such that the pressure on the unit area increases at a ramp rate of about 10 to 20 tsi per second. In another example, the pressure on the unit area ramps up from 0-100 tsi within 5 seconds at a rate of about 10 to 20 tsi per second, and then ramps down from 100-0 tsi within the next 5 seconds, again at a rate of about 10 to 20 tsi per second.
At step 308, the method 300 includes rotating the die 104 further to release the first portion of the powdered metal 108 from a second end 114 of the die 104. Therefore, the pressed metal units 124 are being released out of the pressing zone 110, and further released out of the second end 114 of the die 104. At step 310, following the release of the first portion, a second portion of the powdered metal 108 may be pulled into the first end 112 of the die 104 for pressing operations.
In one embodiment, the pressed portion of the powdered metal 108, i.e., the pressed metal units 124 may be sintered by using high temperature to form a compact portion or a compacted piece, based on the continuous process or the semi-continuous process, respectively. The compact portion can be understood as a strip of pressed metal units 124 obtained after the continuous process of manufacturing.
As is generally known, in sintering, the temperature of the pressed metal unit 124 may be increased to a predefined temperature, also referred to as sintering temperature. The pressed metal unit 124 may then be kept at the sintering temperature for a predefined duration of time. In one example, the predefined temperature can be kept about 70% to 90% of the melting point of the powdered metal 108. This would result into bonding between the particles of the powdered metal 108 pressed together in the pressed metal unit 124.
In case of the continuous process of manufacturing, the compact portion obtained after the sintering operation may be cut to form individual compacted pieces. In an alternate embodiment, the compact portion or the strip of pressed metal units 124 may be cut to form individual compacted pieces before the sintering operation. The individual compacted pieces can then be sintered.
Following the sintering, the individual compacted pieces may be shaped to form the object. In one example, the object may be a spiral ring, a planar ring, an I-beam, or another shape of a complex cross-section. In one embodiment, the system 100, 200 may be modified to manufacture an I-beam. In such an embodiment, the shape of the die 104 may be changed for pressing the powdered metal 108 to manufacture the I-beam. Therefore, in such embodiments, the overall principle of the pressing and manufacturing of the object would remain as described in the previous embodiment with a ring gear. In some embodiments, the dimension and geometry of the die 104 may change based on the object to be manufactured.
In one embodiment, the object so obtained can then be sent for secondary processing. The secondary processing may include, but is not limited to forging, machining, bending, shearing, coining, milling, or any combination thereof.
The system 100, 200 and method 300 of the present disclosure provides focused pressure across the component or the powdered metal 108 during the pressing operation. During the pressing operation, each unit area of the powdered metal 108 in the pressing zone 110, 210 between the die 104, 204 and the roller 106 would experience an increase from zero load to maximum load and then back to zero load. Such uniform distribution of the pressure may assist in manufacturing objects with near uniform density.
Further, as the load is focused on a smaller area of the powdered metal 108 during the pressing operation, the localized pressure, for example in the pressing zone 110, 210, is substantially higher than that obtained using conventional techniques such as, a punch and die technique. The continuous or semi-continuous processes allow higher/focused pressure to be applied while pressing or compacting the powdered metal 108. The processes further provide better control of the pressure and density on the powdered metal 108 which in turn assist in manufacturing of complex parts.
Also, since density can be kept nearly uniform across the entire surface of the powdered metal 108 during the pressing operation, the system 100, 200 and the method 300 enable manufacturing of large size components with a near uniform density that cannot be produced using conventional techniques such as, a punch and die technique. For example, ring gears with large diameters can be made by using the system 100, 200 and the method 300. In one example, gears with a diameter of 36 inches to 60 inches can be easily made by using the method 300 and the system 100, 200 of the present disclosure.
In addition a higher level of efficiency can be accomplished. For example, by using the continuous process of manufacturing, large complex linear strips including a plurality of pressed metal units 124, 224 can be manufactured. The strip can then be cut into individual smaller units after the pressing operation for performing operations, such as shaping and sintering. In one example, the length of such linear strips can be up to 80 feet. As a result, a large volume of products can be obtained in a substantially short time by using the continuous process of manufacturing.
Moreover, the system 100, 200 and the method 300 allow for filling of the powdered metal 108, pressing of the powdered metal 108, and removal of the powdered metal 108 in a single step. As a result, inconvenience and time associated with executing these steps separately are substantially reduced. Therefore, the present disclosure offers an effective, easy, productive, flexible, time-saving, convenient, and cost-effective system 100, 200 and method 300 for compacting powdered metal 108.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
