Patent Application
20150167144
This application is based upon, and claims the benefit under the Paris Convention of the priority of, Chinese Patent Application 2013 1068 1469.1 filed Dec. 13, 2013, the specification and drawings thereof being incorporated herein by reference.
This Application relates to a surface coating modification method. with the use of ultrasonic pressurized rotating friction process. This method is particularly suitable to improve the density of the coating layer material and the bonding of the coating material to the base metal of the substrat, All these improvement help to improve the life of welding electrodes.
With the recent development of the automotive industry, ordinary steel material cannot meet the requirements in areas such as anti-corrosion and weight. To meet the future development needs of the automotive industry, a variety of coated steels and galvanized steels are widely used. At the same time, to save energy, the desirability of lightweight in vehicles has gradually become one of the main issues to consider in the automobile manufacturing industry. Aluminum alloy plates have gradually been adopted in the automotive lightweight development. Although there is a variety of material to be selected in the production of automoblies, there are not many choices available for production processes. Resistance spot welding is still the main technology used in the automotive assembly, especially in body frame construction. The life of welding electrodes has become an important issue in the resistance welding of galvanized steel and aluminum sheets. This in turn increases the consumption in automotive production and thus raises the production cost. To solve this problem, researchers conducted many studies. The most representative research result is the application of a protective coating layer (metallic or cermet) to the surface of welding electrodes through the electro-spark deposition process. This helps the welding electrodes to resist or delay alloy migration and plastic deformation during welding, thus improving the usage life of resistance welding electrodes.
Electro-spark deposition (ESD) is a micro-arc pulse welding technology which transfers electrode material to a metallic substrate with the use of high frequency and short duration current pulses. The main advantage of electro-spark deposition is the ability to produce metallurgical bonding between the coating material and the substrate base metal with low heat transfer. Due to thermal shock when the spark discharges, ESD coatings may tend to have flaws.
Chen Zheng et al, noticed such problems on the coating layers of resistance spot welding electrodes coated with electro-spark deposition technology. To repair these defects, Chen Zheng used a laser to treat the coating by re-melting the TiC coating on the surface of the spot welding electrodes. Although coating defects can be eliminated or improved, there is no apparent increase in the life of the welding electrode. It may be that the laser may cause the temperature of the copper base metal to rise above its annealing temperature and thus producing softening to the electrode substrate. From one aspect of this research, it is understood that the treatment temperature on the coating of the welding electrode surface ought not to exceed the annealing temperature of the electrode substrate (copper alloy in this case) metal. Otherwise it will result in softening of the electrode substrate metal.
Friction Stir Welding (referred to as FSW) is a patented technology invented by British Welding Institute in 1991. In friction stir welding a cylindrical shape welding pin (welding probe) is inserted into the seam or joint of two facing metals. The welding probe rotates at a high speed and it generates enough heat from the friction between the probe and the metals to soften the metal at the joint. This yields a mechanical joint between the two facing metals. Different types of processing technology have been tried by various domestic and foreign researchers to achieve grain refinement using the friction stir welding processing. Ultrasonic grain refinement processing, as a secondary process technology, has been widely studied and reported in areas such casting, welding, and surface material treatment. Kwanghyun Park was the first to study the ultrasonic assisted friction stir spot welding equipment and processes. Ultrasonic assisted friction stir welding process can produce welded joints with better performance than friction stir welding alone.
Friction stir processing technology is newly developed based on the friction stir welding process for the surface coating modification of composite material. Due to the unique thermal or mechanical characteristics, or both, friction stir processing has been used in the preparation and modification of surface coatings. Zhou Xiaoping et al (Chinese invention patent CN201010570898.8, the preparation and modification of Al2O3+TiB2+Al composite coating on aluminum surface by friction stir welding) has demonstrated that the density and micro-hardness of Al2O3+TiB2+Al composite coating produced by thermal spraying process can be improved by friction stir processing.
Similarly, Chinese invention patents (CN 201310050662.5) “A semi-solid ultra fine grain/nano-crystalline plate processing method based on ultrasound-assisted friction stir processing”, (CN 201310049003.X) “An ultrasound-assisted semi-solid friction stir processing method in a controlled low temperature environment”, and (CN 201310049927.X) “a realization of surface UFG/nano material based on ultrasonic assisted semi-solid friction stir processing method” have adopted ultrasound-assisted semi-solid friction stir processing technology, implemented with the use of a stirring pin for surface treatment.
Use of a friction stir processing pin may expose the coating material of the substrate. Part of the base material may mix with the coating material, resulting in a possible deterioration of mechanical and physical properties. As a result, a friction stir process may not be suitable for the modification of surface coatings, such as those on resistance spot welding electrodes. In addition, the process is difficult, and power consumption may be high.
The following summary is provided to introduce the reader to the more detailed discussion to follow. The summary is not intended to limit or define the claims.
In an aspect of the invention there is a surface modification apparatus and method for treating electro-spark deposition coating layers. It may include a processing method for a surface coating in which there is use of a flat or curved shaped head applying pressurized, or force biased rotating friction to the surface coating on a workpiece. Ultrasonic vibration is simultneously applied to the workpiece or the rotating head. In a feature of that aspect of the invention the shape of the friction spinning head or probe is flat or curved surface, without a projection spinning pin or needle.
In this aspect, it may be that the coating material would not be removed from the base material of the workpiece. It may be that no base material of the substrate is disturbed in the process. This may help to maintain the coating material composition during the process. With the addition of ultrasonic vibration to the surface coating during the process, coating defects (delaminations, porosity, cracks and uneven coating) may be reduced or eliminated and high binding strength to the base material may be achieved. In addition, the physical and mechanical properties of the coating may also be improved.
In a feature of that aspect of the invention, the force-biased rotating friction head and the workpiece spin in opposite directions. The surface coating may undergo a continuous treatment process. The composition of the surface coating may remain unchanged while coating defects are eliminated giving better coating performance as a result.
In another aspect of the invention there is an apparatus for the surface modification of surface coating on workpieces. It includes a work table for the clamping of the workpieces. It has an ultrasonic, force-biased rotating friction device and an ultrasonic power source. The ultrasonic rotating friction device has a force-biased rotating friction module and an ultrasonic transducer. The ultrasonic transducer is electrically connected to the ultrasonic power source. The shape of the rotating friction probe may be either flat or curved. The friction probe may be free of any projection pin on the flat or curved surface thereof. The surface may be planar.
In various features of that aspect of the invention, the apparatus may include one or more of the following: a rotating electrode holder workstation having an equipment frame, an electric motor, a transmission belt, pulley, supporting bearings, a transmission shaft, a clamping chuck and a dual guiding rails; an integrated ultrasonic transducer with rotating friction head apparatus comprising: a pair of sliders, upper and lower panels, screw shaft, poisitive and negative inputs of the ultrasonic power, a sliding conductor, bearings, a belt pulley, a driving belt, an electric motor, an eltrasonic transducer, a transducer horn, a rotating friction head and the housing; an ultrasonic power source having ultrasonic positive output terminal, an ultrasonic power control knob, the ultrasonic negative output terminal, and a power switch.
Integration of the workstation, pressurized rotating friction module and the ultrasonic power source: The equipment frame is fixed to the workstation, the electric motor drives the transmission shaft through the coupling of the driving belt and pulley; the clamping chuck for work pieces is mounted to the transmission shaft; The integrated rotating friction assembly is fitted to the workstation through the fitting of the sliders to achieve free repeating movements, this allows rotating friction application to the surface coating of workpiece on the workstation assembly; the lower panel of the rotating friction assembly is attached to the upper panel through the coupling of the screw shaft, this allows the rotating friction assembly to move in a vertical direction and thus to achieve the application of pressure during the process by adjusting the screw shaft; the ultrasonic input +ve and −ve terminals are connected to the corresponding terminals of the ultrasonic power source; the sliding conductor is connected to the ultrasonic transducer with the use of electrical wires; the transducer horn is mounted to the ultrasonic transducer; the rotating friction head is driven to rotate through the driving of the electric motor, driving belt, belt pulley and the support bearing; this setup achieves the application of the pressurized rotating friction to workpiece on the workstation; the rotating friction assembly is then enclosed in the housing.
On the workstation, the clamping chuck for mounting the workpiece is driven to rotate by the electric motor through the transmission of the driving belt and pulley. With the fitting of the 2 sliders on the lower panel and the 2 guiding rails on the workstation, the integrated ultrasonic rotating friction assembly can be used to process the workpiece repeatedly.
With the integrated ultrasonic rotating friction assembly attached to the upper panel, the upper panel is attached to the lower panel through the screw shaft. Not only does the screw shaft move the upper panel in a vertical direction, it also allows certain pressure to be applied to the workpiece. The ultrasonic rotating friction assembly is driven by the motor through the transmission of the pulley, belt and bearings. Through the adjustment to the screw shaft, the pin-less friction head can be moved to make friction contract with the workpiece. Furthermore, with the application of pressure and the ultrasonic vibration simultaneously, it is made possible to modify surface coatings on workpiece using ultrasonic pressurized rotating friction processing.
In an aspect of the invetnion there is a process of surface treatment of an ESD coating. The process includes biasing a friction head assembly against a workpiece to which an ESD coating is applied; moving the workpiece relative to the friction head while in contact therewith; and subjecting the coating to ultrasonic vibration while the friction head is in contact therewith.
In a feature of that aspect of the invention, the process includes rotating the workpiece while the friction head is in contact therewith. In another feature, the process includes rotating said friction head assembly while it is in contact with the workpiece. In a further, additional feature, the process includes rotating the workpiece while the friction head is in contact therewith. In another feature, the coating is a TiC coating. In another feature, the process includes depositing the ESD coating. In still other features, the process may include at least one of (a) an ultrasonic frquency of about 50 kHz; (b) a biasing force of about 200N; and (c) a rotational speed of the rotating friction head of about 1400 rpm.
In another aspect of the invention, there is an apparatus for the processing of surface coating modifications of an ESD coating on a workpiece surface. The apparatus has a work station for the mounting and rotation of the workpiece; a friction assembly, operable, in use, to be biased against the workpiece; and an ultrasonic transducer mounted to transmit ultrasonic vibration to the workpiece while the workpiece is in contact with the rotating friction assembly.
In a feature of that aspect of the invention, the apparatus has an ultrasonic power source; and the ultrasonic transducer is connected to the ultrasonic power source. In another feature, the friction head has a shape that is one of (a) flat; and (b) curved. In still another feature, the friction assembly is also mounted for rotation. In still yet another additional feature, the apparatus is such that at least one of (a) the ultrasonic transducer operates at about 50 kHz; (b) in use, the biasing force is about 200 N; and (c) the friction head is mounted for rotation at about 1400 rpm.
There are many combinations and permutations of aspects and features. It will be understood that any of the features may be combined, as appropriate, with any of the aspects enumerated herein.
The foregoing aspects and features of the invention may be explained and understood with the aid of the accompanying illustrations, in which:
The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles of aspects and features of the invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The photograpihc views may be taken as being to scale, or generally proportionate, unless indicated otherwise.
The scope of the invention herein is defined by the claims. Though the claims are supported by the description, they are not limited to any particular example or embodiment, and any claim may encompass processes or apparatuses other than the specific examples described below. Other than as indicated in the claims themselves, the claims are not limited to apparatuses or processes having all of the features of any one apparatus or process described below, or to features common to multiple or all of the apparatus described below. It is possible that an apparatus or process described below is not an embodiment of any claimed inventions.
The terminology used in this specification is thought to be consistent with the customary and ordinary meanings of those terms as they would be understood by a person of ordinary skill in the art. Following from the decision of the Court of Appeal for the Federal Circuit in Phillips v. AWH Corp., the Applicant expressly excludes all interpretations that are inconsistent with this specification, and, in particular, expressly excludes any interpretation of the claims or the language used in this specification such as may be made in the USPTO, or in any other Patent Office, other than those interpretations for which express support can be demonstrated in this specification or in objective evidence of record in accordance with In re Lee, (for example, earlier publications by persons not employed by the USPTO or any other Patent Office), demonstrating how the terms are used and understood by persons of ordinary skill in the art, or by way of expert evidence of a person of experience in the art.
Reference is made herein to welding electrode tips and caps, which are intended to provide a generic example of a work piece that is movable with respect to at least one degree-of-freedom of motion while being coated. Other objects could also be coated. In respect of each tip or cap, it may be helpful to define a polar-cylindrical co-ordinate system, in which the axial, or z-direction defines the axis about which the cap or electrode tip is formed, or has a surface, on a body of revolution, the term radial refers to a distance away from the z-axis, and circumferential refers to an angular direction about the z-axis.
This Application relates to a surface coating modification method such as may employ ultrasonic pressurized rotating friction process. This method may be used to encourage improvment of the density of the coating layer material and the bonding of the coating material to the base metal of the substrate. This process may be applied in rrespect of the coating of welding electrodes. Coating electrodes, or other surfaces, in this manner may tend to prolong or extend the life of welding electrodes.
The following is a description of an apparatus and method for post deposition treatment of a coated resistance welding electrode, as shown in
A work table A is emploed for the clamping of the workpieces. Table A may have an equipment base or frame 2, an electric motor 3, a mechanical transmission or drive belt 4, a pulley 5, a supporting bearing 6, a transmission shaft 7, a clamping chuck, or tool-holder, in which to hold the workpiece 8, a first track or guide rail 9 and a second track or guide rail 10.
The integrated ultrasonic rotating friction head assembly B may have a slider 11, a lower panel 12, a screw shaft 13, an upper panel 14, an ultrasonic transducer positive input terminal 15, an ultrasonic transducer negative input terminal 16, a brush or shoe, or sliding conductor 17, bearings 18, a belt pulley 19, a mechanical transmission or drive belt 20, an electric motor 21, a transducer 22, a transducer horn 23, a rotating friction head 24, a housing 25 and a slider 26.
An ultrasonic power supply C may include an ultrasonic output positive terminal 27, an ultrasonic output power knob 28, an ultrasonic output negative terminal 29, and an ultrasonic power switch 30.
The apparatus may include the integration of the combined apparatus of assemblies
A, B and C. Electric motor 3 of the workstation A is fixed to, or mounted to, the main machine frame 2. Drive power from the output shaft of electric motor 3 is coupled to drive transmission shaft 7 in rotation through the transmission belt 4, pulley S and supporting bearings 6.
The workpiece having a surface coating to be treated or modified is mounted to, or in, clamping chuck 8. Clamping chuck 8 is connected to the transmission shaft 7, such that operation of motor 3 may cause corresponding driven rotation of chuck 8. Guide rails 9 and 10 of module A are fitted to, or mated to, or engaged with, sliders 11 and 26 respectively of the integrated ultrasonic rotating friction head assembly B.
Pressurized rotating friction motion from rotating friction head assembly B can be repeatedly applied to the surface coating on the workpiece 1 as required for the processing procedure. In this decription the term “pressurized” may tend to mean pressing or forcing, or biasing, the coating apparatus against workpiece 1 under some biasing force, where at least a component of the force is normal to the surface of workpiece 1 at the location of contact of the coating interace, such that the coating apparatus is biased against the workpiece such that relative motion (e.g., including a component of moton tangential to the normal vector defining the line of contact of the surfaces) between them will give rise to friction between the coating apparatus and the workpiece surface, e.g., in the tangential plane to which the normal vector of the surface is perpendicular.
Upper panel 14, which is mounted with the rotating friction head assembly, is connected to lower panel 12 through the coupling of screw rail 13. Rotating friction module B can be driven up and down with the use of the screw shaft of screw rail 13. Application of certain pressure, or force, of, or against, the coating surface of workpiece A can also be achieved with simultaneous rotational motion, be it of workpiece A or of the coating apparatus. The positive 15 and negative 16 terminals of the ultrasonic transducer are connected to the output positive 27 and negative 29 terminals, respectively, of ultrasonic power supply C. Sliding conductor 17 is connected to transducer 22 with the use of a pair of electrical wires. Transducer 22 is connected to the transmission horn 23 for the transmission of ultrasonic energy to rotating friction head 24.
The shape of the top of the friction head could be flat or curved according to the requirement of the workpiece. Ultrasonic pressurized rotating friction, i.e., friction at the contact interface of the rotating surface under a biasing force normal to that surface, can be applied onto the coating surface of workpiece 1 with the use of the integrated friction head assembly. The rotation is driven through electric motor 21, driving belt 20, belt pulley 19 and bearings 18.
In this application example, on workstation A, the transmission shaft that is mounted with a clamping chuck is driven in rotation by the electric motor through the coupling of transmission belt, pulley and bearings. The integrated ultrasonic rotating friction head assembly can be moved vertically through the fitting of the two sliders on the lower panel with the two guiding rails on workstation A. The rotating friction process can be applied to the workpiece repeatedly.
In this embodiment, the ultrasonic rotating friction head assembly is attached to upper panel 14 which is connected to lower panel 12 through screw shaft 13. The screw shaft serves two purposes, namely, first, to move the ultrasonic rotating friction head assembly vertically (up and down); and, second, to apply pressure, or a biasing force, to workpiece A.
The ultrasonic rotating friction head assembly is driven in rotation by the electric motor through the coupling of the belt and bearings, such that the workpiece rotates. It is also driven to make contact and apply pressure, that is a biasing force, to the workpiece through the control of the screw shaft. With the application of ultrasonic vibration, the apparatus is able to perform ultrasonic pressurized rotating friction processing to the surface coating of the resistance welding electrodes. That is, while the apparatus is under the biasing force against workpiece A, and while there is rotating friction, ultrasonic vibration is also being applied and transmitted across the same contact interface.
The following gives the procedure of the ultrasonic pressurized, or force-biased, rotating friction process:
The rotating friction head, with external pressure (i.e., biasing force) and ultrasonic vibration is then used to treat or modify the surface coating of the welding electrode, or to such other coated surface as may be. The rotating friction head is moved, or translated, or reciprocated, along guide rails 9, 10 to cover the complete surface of the coating on the welding electrode. The power is turned off when the process is finished.
In this example application, the ultrasonic power may be about, or is 100 W; ultrasonic frequency may be about, or is 50 kHz; pressure (i.e., biasing force) on the surface coating from the rotating friction head may be about, or is, 200 N; rotational speed of the rotating friction head may be about, or is 1400 rpm. For a welding electrode cap the process time may be about, or is, 3 minutes.
In the example described, the microscopic views show an improvement in respect of the coating defects. That is, the delaminations, cracks, discontinuities and voids are significantly reduced, or eliminated, with the application of the process described. It is also noted that the grain of copper alloy near the coating boundary zone has also been refined, i.e., made finer, after the process.
To summarise, the above example discloses a method and apparatus for the processing of a surface coating. It includes an ultrasonic pressurized, or force-biased, rotating friction head assembly that is used to apply the surface coating of the workpieces. The shape of the friction head could either be flat or curved depending on the surface of the coating on the workpiece. In this process, rotating action (i.e., rotation of the workpiece, or, more generally, relative motion between the workpiece and the coating apparatus to which the normal vector of contact is perpendicular) in conjunction with ultrasonic vibration while the applicator is force-biased against the workpiece, is used to apply the surface coating on the workpiece, and to improve the properties of the surface coating. In the particular application, the apparatus used for the ultrasonic pressurized rotating friction coating processing may have a work station in which to mount and in which to rotate a TiC coated welding electrode as the workpiece. There is an integrated rotating friction head assembly completed with an ultrasonic transducer; and an ultrasonic power source. The process includes the integration of a force-biased rotating friction device with an ultrasonic transducer. The integrated device, with the concurrent application of rotating friction and ultrasonic vibration, may tend to reduce the defects that might otherwise occur on the TiC coatings on welding electrodes produced using the electro-spark deposition process.
The process decribed, with the application of ultrasonic rotating friction under a normal force, may tend to improve the binding strength of the ESD coating layers and also may tend to reduce or eliminate coating defects. It may improve the physical and mechanical properties of the coating while preserving the material contents intact. The apparatus and process of the example described may have advantages of reduced cost and increased ease of use. In addition to treating electrospark deposition coating defects, this invention may also have other applications, such as being employed to repair other surface coatings covering a wide range of applications. This description is intended to apply to such other coatin applications as may be amenable to the application of the ultrasonic pressurized (or force-biased) rotating friction process.
What has been described above has been intended illustrative and non-limiting and it will be understood by persons skilled in the art that other combinations of the features described above, and modifications, may be made without departing from the scope of the disclosure as defined in the claims appended hereto. Various embodiments of the invention have been described in detail. Since changes in and or additions to the above-described best mode may be made without departing from those aspects, the invention is not to be limited to those details but only by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201310681599.1 | Dec 2013 | CN | national |
