Patent Application
20170197274
Friction stir joining is a technology that has been developed for welding metals and metal alloys. Friction stir welding is generally a solid state process that has been researched, developed, and commercialized over the past 20 years. Solid state processing is defined herein as a temporary transformation into a plasticized state that may not include a liquid phase. However, it is noted that some embodiments allow one or more elements to pass through a liquid phase.
Friction stir joining began with the joining of aluminum materials because friction stir joining tools could be made from tool steel and adequately handle the loads and temperatures that may be needed to join aluminum. Friction stir joining has continued to progress into higher melting temperature materials (HMTMs) such as steels, nickel base alloys and other specialty materials because of the development of superabrasive tool materials and tool designs capable of withstanding the forces and temperatures that may be needed to flow these higher melting temperature materials.
It is understood that the friction stir joining process often involves engaging the material of two adjoining planar workpieces on either side of a joint by a rotating stir pin. Force is exerted to urge the pin and the workpieces together and frictional heating caused by the interaction between the pin, shoulder and the workpieces results in plasticization of the material on either side of the joint. The pin and shoulder combination or “FSW tip” is traversed along the joint, plasticizing material as it advances, and the plasticized material left in the wake of the advancing FSW tip cools to form a weld. The FSW tip may also be a tool without a pin so that the shoulder is processing another material through FSP.
Referring to
It is observed that when the shoulder 12 contacts the surface of the planar workpieces, rotation of the shoulder creates additional frictional heat that plasticizes a larger cylindrical column of material around the inserted pin 14. The shoulder 12 provides a forging force that contains the upward metal flow caused by the tool pin 14.
During friction stir joining, the area to be joined and the tool are moved relative to each other such that the tool traverses a desired length of the weld joint at a tool/workpiece interface. The rotating friction stir welding tool 10 provides a continual hot working action, plasticizing metal within a narrow zone as it moves transversely along the base metal, while transporting metal from the leading edge of the pin 14 to its trailing edge. As the weld zone cools, there is no solidification as no liquid is created as the tool 10 passes. It may be the case that the resulting weld is a defect-free, re-crystallized, fine grain microstructure formed in the area of the weld.
Friction stir welding of high melting temperature materials may require the use of specialized equipment. For example, it may require the use of a polycrystalline cubic boron nitride tool, a liquid cooled tool holder, a temperature acquisition system, and the proper equipment to have a controlled friction stir welding process. The present disclosure is also applicable to lower melting temperature materials such as aluminum and other metals and metal alloys that are not considered part of the high melting temperature materials.
This document also addresses methods of mechanically joining components. A mechanical joint may be useful when components are removed or replaced after use. Mechanical joints include using fasteners such as screws, bolts, rivets, rods and cotter pins, zip ties, paper clips, etc. Mechanical joints may be used in applications where the operating environment is particularly harsh such as in aerospace, oil and gas exploration, mining and others. These applications may benefit from a more permanent fusion joining method such as a weld or a brazed joint. However, fusion joining methods may not be practical because of potential thermal damage to the parts, distortion that prevents fit up with mating parts, solidification defects, safety, cost or simply that the materials being joined cannot be fusion joined due to the physical properties of the materials.
An example is given where the state of the art fails to provide an adequate solution. Mining of coal and minerals may require equipment that is continually exposed to hard rocks, abrasive minerals and random materials encountered during the mining operation. In order to minimize machine component wear of the equipment that is caused by exposure to this environment, abrasion resistant materials are employed in the manufacture of the equipment. These materials are designed as consumable components that may be continually replaced.
One of the most common abrasion or wear resistant materials used in equipment that is subjected to severe wear environments is cemented tungsten carbide or tungsten carbide. Mining equipment may use thick section tungsten carbide to line machine surfaces that are in contact with minerals, rocks, abrasive materials or other materials being extracted from the earth. Tungsten carbide is a common material of choice because of its very high hardness and resistance to wear under extreme conditions.
The process of manufacturing tungsten carbide may use a powder including tungsten carbide crystals and cobalt. This mixture may be cold pressed together with a binder to form a “green” state which is then formed to a desired shape. The green state may be characterized as being relatively soft, like chalk, which may then be formed and/or machined into a variety of shapes. After the green state mixture has been formed, it may be put through a high temperature/vacuum or a high temperature/high pressure sintering process that may cause it to shrink by up to 48% by volume. Shrinkage may be more or less.
The sintering process may give tungsten carbide its high hardness but may also leave it brittle compared to steel and other ferrous alloys. The sintered carbide component may then be ground to a finished size according to application requirements.
Because tungsten carbide is brittle, sharp corners should not be designed or integrated into the design of the carbide component. Sharp corners may be stress raisers and may create cracking during the sintering process or during subsequent usage in an application. As a result, it may be difficult to include certain features into the design of the carbide component such as threads to hold bolts and other conventional features that function as locking mechanisms because they may have sharp corners. Accordingly, it may be difficult to find a method to secure tungsten carbide components to equipment or to a surface that is exposed to the high loads that may be generated during mining and excavation operations.
It is noted that there are many materials such as ceramics, cermets (ceramic-metallic), intermetallics, as well as other high strength materials that may not be readily joined and yet could be used wherever a wear resistant solution may be used for a number of applications.
An example is shown in
One of the aspects with the design shown in
As for attaching the tungsten carbide plate 30 to the steel weldable work piece 32 using adhesive, applications of using the assembly may generate substantial heat from frictional wear which may cause the adhesive to decompose and delaminate the tungsten carbide from the steel weldable work piece substrate. Other aspects of using an adhesive may include, but should not be considered as limited to, poor performance in very cold conditions, premature failure due to low strength or brittle failure, poor chemical resistance to acidic compounds, and the mechanical strength of adhesives is inherently very low and high shear forces generated by rock and debris may pull the tungsten carbide from the substrate during equipment operation.
Another known joining method is brazing, which also has limitations. The braze material along with the components to be joined may need to be heated to 600° C. to 1100° C. In this case, the thermal expansion of the steel weldable work piece 32 is much greater than the thermal expansion of the tungsten carbide plate 30. During the cooling process, residual stresses may be introduced at the joint between them as the steel weldable work piece 32 contracts more than the tungsten carbide plate 30. This may effectively reduce the strength of the joint to that of an adhesive.
The present disclosure is a system and method for securely join together a high melting temperature material and a backing substrate or plate using a mechanical connection.
In a first aspect, a friction-stir joined assembly includes a high melting temperature material forming a plate having an outer surface and an opposite attaching surface. At least one dovetailed recess may be disposed in the attaching surface, and then an insert may be disposed in the dovetailed recess. A weldable work piece may be disposed against the attaching surface and then friction stir welded to the insert. The insert may form an interference fit inside the dovetailed recess after friction stir welding. An attachment device may be then coupled to the weldable work piece so that the assembly can be attached to a piece of equipment or other device that can use a wear resistance surface.
In another aspect, the same friction-stir joined assembly is created but without the insert. During friction stirring of the weldable work piece, material from the weldable work piece is extruded into the dovetailed recess until an interference fit is created.
In another aspect, the friction-stir joined assembly is created without using a high melting temperature material but may be the same in other respects.
In another aspect, a method for creating the friction-stir joined assembly includes forming a non-weldable work piece into a desired shape before it is hardened and then selecting an outer surface and an opposite attaching surface. A plurality of dovetailed recesses is also formed in the attaching surface before hardening of the non-weldable work piece. An insert is then disposed into each of the dovetailed recesses. An attachment device is then coupled to the weldable work piece so that the assembly can be attached to a piece of equipment or other device that can use a wear resistance surface.
In another aspect, the dovetailed recesses are formed after the non-weldable work piece is hardened.
In another aspect, the same friction-stir joined assembly is created but without the inserts. During friction stirring of the weldable work piece, material from the weldable work piece is extruded into the dovetailed recess until an interference fit is created.
In another aspect, at least two recesses are created in the high melting temperature material, the recesses not being perpendicular to the attaching surface but at an angle relative to each other. A weldable work piece is friction stir welded to inserts that are disposed inside of each of the recesses, the angle of the recesses keeping the high melting temperature material coupled to the weldable work piece.
In another aspect, at least two recesses are created in the high melting temperature material, the recesses are not being perpendicular to the attaching surface but at an angle relative to each other. By extruding material into the recesses from a weldable work piece, the angle of the recesses keeps the high melting temperature material coupled to the weldable work piece.
These and other embodiments of the present will become apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings.
One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, some features of an actual embodiment may be described in the specification. It should be appreciated that in the development of any such actual embodiment, as in any engineering or design project, numerous embodiment-specific decisions will be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one embodiment to another. It should further be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
One or more embodiments of the present disclosure may generally relate to the joining of a first material having a first strength and/or first ductility and a second material having a second strength and/or second ductility where the second strength is greater than the first strength and/or the second ductility is less than the first ductility. For example, a tool steel workpiece may be joined to a tungsten carbide workpiece. The tool steel, while having a high yield strength and low ductility, may still have a lower yield strength and greater ductility than the tungsten carbide. Tungsten carbide may be functionally non-weldable due to its high hardness and brittleness and low ductility. In another example, an aluminum alloy workpiece may be joined to a tool steel workpiece. The aluminum alloy, while having a high yield strength and low ductility compared to some materials, may still have a lower yield strength and greater ductility than the tool steel. The tool steel, while weldable by some processes including friction stir welding (“FSW”), may require specialized equipment or conditions that may render the tool steel non-weldable for a particular application.
As used herein, “non-weldable” should be understood to describe a material and/or workpiece that, given the equipment or conditions used to weld another material, is non-weldable. For example, a first material may be weldable by a given FSW tool capable of a certain speed of rotation, force applied normal to a workpiece, force applied lateral to a workpiece (e.g., to move the FSW tip along a path), movement speed, or other operational parameters. A second material may not be weldable by the given FSW tool, although the second material may be weldable by other equipment and/or conditions. Therefore, one should understand that the present disclosure may allow a given FSW tool to join a weldable material to a non-weldable material or, in other words, to a material which the given FSW tool may be unable to weld.
In some embodiments, a non-weldable material may include tungsten carbide, silicon carbide, alumina, cubic boron nitride, polycrystalline diamond, boron carbide, boron carbon nitride, materials having a hardness greater than 40 gigapascals (GPa) when measured by the Vicker's hardness test, or combinations thereof. In other embodiments, a non-weldable material may include steel, such as carbon steel (e.g., AISI 10XX, AISI 11XX, AISI 12XX, or AISI 15XX), manganese steel (e.g., AISI 13XX), nickel steel (e.g., AISI 23XX, or AISI 25XX), nickel-chromium steel (e.g., AISI 31XX, AISI 32XX, AISI 33XX, or AISI 34XX), molybdenum steel (e.g., AISI 40XX, or AISI 44XX), chromium-molybdenum steel (e.g., AISI 41XX), nickel-chromium-molybdenum steel (e.g., AISI 43XX, or AISI 47XX), nickel-molybdenum steel (e.g., AISI 46XX, or AISI 48XX), chromium steel (e.g., AISI 50XX, or AISI 51XX), combinations thereof, and the like, where “XX” may range from 1 to 99 and represents the carbon content; titanium alloys; nickel superalloys; other metal high melting temperature alloys.
A weldable material and/or a non-weldable material may be magnetic or non-magnetic. For example, the weldable workpiece may be a magnetic material or a non-magnetic material and the non-weldable workpiece may be a magnetic material or a non-magnetic material. In some embodiments described herein, a first workpiece made of or including a weldable material may be in contact with a second workpiece made of or including a non-weldable material. One, both, or neither of the workpieces may be magnetic. A workpiece that is magnetic may, in some embodiments, magnetize the adjacent workpiece.
Reference will now be made to the drawings in which the various embodiments will be given numerical designations and in which the embodiments will be discussed so as to enable one skilled in the art to make and use the embodiments of the disclosure. It is to be understood that the following description illustrates embodiments of the present disclosure, and should not be viewed as narrowing the claims which follow.
A first embodiment is shown in
The shape of the non-weldable work piece 40 may be rectangular or any desired shape and should not be considered limited to the example being shown. As described herein, in some embodiments, the non-weldable workpiece may be a ceramic, a carbide, an ultrahard material, other material formed in a green state, or combinations thereof. In such embodiments, the desired shape may be created while the non-weldable work piece 40 is in the green state and then hardened.
The dovetailing grooves 44 may be described more generically as a dovetailing depression, recess, or cavity in the non-weldable work piece 40. The grooves 44 may be considered to be a specific case of a dovetailing recess.
In some embodiments, the grooves 44 may not extend from one end of the non-weldable work piece 40 to the other. One or both of the grooves 44 may not reach the ends of the non-weldable work piece 40. Furthermore, the grooves 44 may not be parallel and also not cross each other. In some embodiments, one or more of the grooves 44 may also cross one or more other grooves. In another embodiment, the grooves 44 may not be straight but may be arcuate. In some embodiments, the grooves 44 may be a combination of straight and arcuate segments.
A feature that may be common to all of the grooves 44 is shown in
The material selected for the inserts 46 may be selected from but should not be considered as limited to the following materials including steel, stainless steel, aluminum, high nickel alloys such as Inconel or any other material that is capable of being friction stir welded.
In some embodiments, the inserts 46 may be made of a plurality of different materials. These different materials may be selected for a particular property that may be obtained from the combination. As an example, such materials may include but should not be considered as limited to a braze material, a corrosion resistant material, a material that may extrude further than other materials, and a material that may be more readily weldable by friction stir welding, by arc or fusion welding or both.
In some embodiments, different materials may be used in different areas of the inserts 46. For example, one material may be used in certain areas where an attachment device will be connected to the weldable work piece 42 in order to improve the strength of the point of attachment.
It should be understood that the inserts 46 and the weldable work piece 42 may not be made of steel or may not be the same type of steel. Furthermore, the inserts 46 and the weldable work piece 42 may be made of different materials. However, the inserts 46 and the weldable work piece 42 should be made of materials that may be friction stir welded together. As long as the inserts 46 and the weldable work piece 42 may be joined using friction stir welding, then the friction-stir joined assembly 50 shown in
One aspect of this first embodiment is that when performing friction stir welding, this process will plasticize portions of the weldable work piece 42 and the inserts 46 that are near the friction stir welding tool, and causing them to flow to the degree as made possible by friction stir welding. It is desirable to fully extrude the material of the weldable work piece 42 and the inserts 46 into the grooves 44. The flow of the material in the weldable work piece 42 and the inserts 46 from friction stir welding may be sufficient to at least partially fill the grooves 44. The material of the weldable work piece 42 and the inserts 46 may not need to fill the entire cavity formed by the grooves 44, but enough to create an interference fit or a friction fit between the bars and the non-weldable work piece 40 that is forming the grooves. The interference fit may be strong enough to prevent the weldable work piece 42 and the inserts 46 from detaching from the non-weldable work piece 40 in a direction that is orthogonal to a plane of the non-weldable work piece 40, but also from sliding out of the grooves 44.
In some embodiments, the inserts 46 may not be disposed within the grooves 44. In such embodiments, the material from the weldable work piece 42 is extruded into the grooves 44 during penetration of the friction stir welding tool 48 into weldable work piece 42. Accordingly, even if no inserts 46 are present in the grooves 44, it has been determined that penetration of the friction stir welding tool 48 into the weldable work piece 42 may be sufficient to extrude sufficient material into the grooves 44 to create an interference fit between material from the weldable work piece 42 and the grooves 44.
In some embodiments, the inserts 46 may not be fitted to the grooves 44. In other words, the inserts 46 form a tight fit within the grooves 44 before friction stir welding. The inserts 46 may be loose fitting filler material. Extrusion from the weldable work piece 42 may fill in gaps between the loose fitting filler material and the grooves 44.
The weldable work piece 42 may be welded, machined, or altered in order to provide an accurate fit to equipment as a replaceable friction-stir joined assembly 50.
The attachment devices 54 should not be considered as limited to the threaded studs shown in
It should be understood that a chute is only one example of an environment in which the friction-stir joined assembly 50 of the first embodiment may be used. The chute is a wear environment in which an ultrahard material may be employed. Other embodiments of wear environments include but should not be considered as limited to mining and bulk material handling such as hoppers, mold boards, bang plates, classifiers, screw conveyor flights, centrifuge flights, distribution nozzles, and coal and ore cargo ship holds. Mineral processing includes such applications as cheek plates, edge rings, feed systems, crushers, and grinders. Valves and flow control applications include end plates, chokes, and rotary valves. Pump applications include impellers, liners, and seats. Power generation applications include combustion fans, pug mill trough liners and paddles, ash trough liners and paddles, combustion nozzles and crushers. Oil and gas applications include mud pumps, hydro heaters, artificial lift pumps and drill string stabilizers. A friction stir-joined assembly as described herein may be used in any industry or application to join one or more materials that are not weldable by friction stir-welding. For example, in addition to the wear resistance applications described, a friction stir-joined assembly as described herein may be used for thermal shielding, for providing low-friction or high-friction surfaces, for aesthetic purposes, other applications, and combinations thereof. These are only a few of the applications for the technology of all of the embodiments disclosed herein.
It should be understood that other features may be added to the grooves 44 in order to prevent sliding of the weldable work piece 42, and these features should all be considered to be within the scope of the first or any other embodiments.
There may or may not be bars disposed within the grooves 86 in the tubular object 80. Accordingly, it may be possible to cause extrusion of material from the weldable work piece tubular object 82 to flow into the grooves 86 of the high melting temperature material tubular object 80 in order to fill the grooves. This means that the grooves 86 may or may not be sufficiently large enough to allow at least a partial penetration of a friction stir welding tool into the grooves 86.
The size of the dovetailed recesses 85 may enable friction stir spot welding through a weldable work piece. In some embodiments, some movement of a friction stir welding tool may be used to cause extrusion of material from a weldable work piece into the recesses 85. The dovetailed recesses 85 may be formed as a cavity with an opening that is smaller than the cavity and thus forming an overhang. The dovetail or overhang may be formed while the non-weldable work piece 80 is in the green state or after it is hardened using a routing tool that can form the dovetail or overhanging shape.
A dovetail groove may be considered to include any type of groove where there is a cavity inside the groove that is larger than an opening into the groove when seen in a cross-sectional view. The dovetail groove may be formed while a non-weldable workpiece such as a high melting temperature material plate is in the green state or after hardening by using any appropriate routing tool.
For example,
It should be understood that the first angled recess 94 and the second angled recess 98 are not restricted to being straight holes. The first angled recess 94 and the second angled recess 98 may include any desired geometrical feature or shape that enables the recesses to lock the weldable work piece 96 to the non-weldable work piece 92.
In another embodiment of the disclosure, the weldable work piece may include a plurality of protrusions or projections. The plurality of projections may be pre-heated. The pre-heated projections may be heated sufficiently such that when the projections are forced into dovetailed grooves or dovetailed recesses of the non-weldable work piece, the plurality of projections on the weldable work piece may be deformed and expand into the dovetailed grooves or the dovetailed recesses, thereby creating the desired interference fit.
It should be understood that while the embodiments are directed to attaching a high melting temperature material to a weldable work piece, the principles of the embodiments are applicable to the mechanical joining of any two materials.
The articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements in the preceding descriptions. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are “about” or “approximately” the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value.
A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional “means-plus-function” clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words ‘means for’ appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims.
The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to “up” and “down” or “above” or “below” are merely descriptive of the relative position or movement of the related elements.
Although the preceding description has been described herein with reference to particular means, materials, and embodiments, it is not intended to be limited to the particulars disclosed herein; rather, it extends to all functionally equivalent structures, methods, and uses, such as are within the scope of the disclosure. Accordingly, all such modifications are intended to be included within the scope of this disclosure. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/026,166, filed Jul. 10, 2014, the disclosure of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/039785 | 7/9/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62023166 | Jul 2014 | US |
