Patent Application
20140263191
Certain embodiments relate to hybrid laser systems in welding, and joining applications. More particularly, certain embodiments relate to a system and method that uses a hybrid laser GMAW system for joining and welding applications.
Welding of stainless steel to copper is known. In many applications the stainless steel is welded to the copper using pure nickel wire. Such processes typically requires preheat due to nickel's poor watering capabilities in the welding process. Further, such welds are being performed manually using GTAW only. However, in such processes stainless steel is subject to distortion, especially when the steel is relatively thin. As such, it is desirable to avoid preheating. Nevertheless, GTAW welding of stainless steel with copper is being performed due to the nickel's better corrosion resistance as compared to a copper based wire. In known methods of welding copper to stainless steel, the copper workpiece must be cooled down, e.g. 50% to 80% of the copper workpiece may need to be submerged in chilled water to prevent overheating and penetration into the copper, and the GTAW process requires a shielding gas of 100% helium (e.g., at 35 CFH), which is relatively expensive and difficult to procure. In addition, the process is highly inefficient with deposition rates around 1.54 lb/hr (0.7 kg/hr) using a 3/32″ AWS ER Ni-1 rod. The travel speed for the GTAW process is between 8 to 10 ipm (0.2-0.25 m/min). Further, there are little to no gains in efficiency when using an automated GTAW process as opposes to manual GTAW.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.
Embodiments of the present invention comprise a system and method to use join stainless steel to copper. The method includes providing a first workpiece composed of stainless steel and providing a second workpiece composed of copper. The method also includes heating by using a laser a root area of a joint created by the workpieces. The method includes providing a consumable electrode that is composed of nickel to the joint and creating an arc between the consumable electrode and the joint using a welding current. A laser beam creates a keyhole in the puddle created by the arc weld that joins between the first workpiece and the second workpiece. The laser beam carries the arc puddle into the base workpiece using the keyhole which eliminates the need to preheat the second workpiece.
These and other features of the claimed invention, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings.
The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which:
Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist in the understanding of the invention, and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout.
Exemplary embodiments of the present invention include a hybrid laser system that is used to create the weld between a stainless steel workpiece and a copper workpiece. Use of a hybrid laser system allows for smaller weld bead size, faster travel speeds, less distortion and a more efficient welding process. This is because, by combining the focused energy of a laser beam with a conventional arc system, such as a GMAW system, to melt the base metal, the penetration of the molten puddle (i.e., weld puddle) is deeper than if just a conventional arc-only system was used. Further, greater penetration is achieved with less heat input from the process. For example, in an exemplary application of welding a T-joint in which two workpieces are joined (one of which is copper and the other is stainless steel), the hybrid laser system can provide deep penetration of the T-joint root on each side of the T-joint with a narrow heat-affected zone (HAZ). By using a laser, the weld bead size can be considerably smaller while still achieving the same, or better, cross section of fused material as that of a fillet weld made with a conventional arc-only system. In addition, due to the smaller bead size, less filler material is needed and the T-joint can be created at travel speeds that are higher than conventional arc-only systems. In some exemplary embodiments of the present invention, travel speeds can be in the range of 15 to 30 ipm, and in some embodiments in the range of 20 to 25 ipm. Further, because there is less molten metal using a laser process, there is less distortion than a conventional arc-only system. Accordingly, a cooling system—as needed in known welding operations—is not required. Further, the GMAW system does not require 100% helium shielding and inexpensive argon and be used. In some exemplary embodiments the argon is used at a flow rate of 35 to 40 CFH.
Because the general construction and operation of hybrid laser welding systems are known, the details of such a system and their general function need not be described herein. The following discussion of
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By using the laser along with the arc process as described herein, the penetration of the keyhole extends far enough into workpieces WP1 and WP2 such that appropriate bonding occurs without excessive heat input. In addition, the laser helps to preheat for the arc by allowing the arc to wet out sufficiently to achieve a smooth transition with minimal bead size. As shown in the exemplary embodiments of FIGS. 2 and 3, the T-joint utilizes fillet welds in both sides of WP1 (stainless steel) (see 114 and 116). As explained previously, in some embodiments each fillet 114/116 weld is done separately by the system 100. In other embodiments, the fillet welds 114 and 116 can be done concurrently using two GMAW systems and either a single laser 120 that can keyhole across the root of workpiece WP1, or a second laser can be used if desired.
In accordance with an exemplary embodiment of the present invention, the workpiece WP1, which can be a stainless steel (for example type 316L), is welded to workpiece WP2, which is composed of primarily of copper. These workpieces can be welded using the system of
During operation, the controller 195 also controls the wire feeder 150 such that the consumable wire 140 is properly delivered to the puddle. In exemplary embodiments the consumable 140 is a nickel based consumable of the type that can be used to join copper and stainless steel. An example of such consumables are AWS Er Ni-1, Techalloy 208 or Metrode Nickel-2Ti, or a similar wire. The wire is fed into the weld puddle created by the torch 160, as each of the fillets is created. Because the beam 110/110′ is also interacting with the puddle and creating the keyholes in WP2 the molten filler is drawn into the keyholes to provide the sufficient bonding. The wire 140 can be any standard filler diameter, e.g., 0.030 to 0.045. Because of the advantages of using embodiments of the present invention, the system 100 can provide deposit rates of the filler material in the range of 3 to 15 lb/hr. This is considerably improved over known systems. In further exemplary embodiments, the deposit rate can be in the range of 7 and 15 lbs/hr. These are speeds and deposition rates which greatly exceed that provided for by traditional systems used to join stainless steel to copper. As discussed above, preheating for the arc is achieved by the laser beam 110 which keyholes to a desired at the weld puddle. Furthermore, because of the use of the laser and the overall reduced heat input, a shielding gas of 100% argon can be used with embodiments of the present invention. Prior system required 100% helium. In exemplary embodiments of the present invention, the argon can be supplied to torch 160 in the range of 35 to 40 CFH.
Accordingly, embodiments of the present invention, unlike conventional processes, are able to take advantage of wire with the highest corrosion resistant alloys in a fully automatic process and with high production rates. In addition, due to the laser, the process can be done without having to preheat on copper. Thus, eliminating the need to providing cooling to keep the stainless from distorting.
While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the present application.
