FLUX DAM ASSEMBLY AND METHOD

Technical Field

This invention relates generally to sub- merged arc welding and more particularly to dam assemblies for retaining granular flux in position during welding.

Background Art

Submerged arc welding with granular flux is a common commercial welding technique. In this technique granular flux is spread in a mound in front of a welding head as the welding head moves across the area of the workpiece being welded. The purpose of the flux is to prevent the welding arc from being exposed to the atmosphere. The electrode in the welding head runs through the flux and the welding arc is fully submerged in the mound of flux. To hold the flux in place while the- electrode is passing through the mound, a flux dam is used. A flux dam also aids in forming the mound, reduces the amount of flux required to submerge the welding head and prevents flux from being wasted.

Since a flux dam is positioned adjacent to the welding head, the dam is subjected to high heat from the arc. Typically flux dams overheat, rapidly deteriorate, and burn up in a short period of time. In addition ₅ when the dam begins to deteriorate, its surface becomes irregular and its shape distorts. Flux then can bleed out underneath the dam causing flux to be wasted and possibly leading to exposure of

the arc to the atmosphere.

There have been several solutions suggested to the problem of deterioration of flux dams. One technique is the use of a stationary dam that is physically attached to the workpiece. This type of dam rapidly deteriorates and is usually not reused. A second solution has been the use of a traveling dam. A traveling dam moves with the welding head and is water cooled. Prior patents in this area of technology include U.S. Patent 2,808,500 to Pandjiris issued October 1, 1957; U.S. Patent 2,900,487 to Danhier issued August 18, 1959; and U.S. Patent 2,972,042 to Ashbaker issued February 14, 1961. Prior solutions to the problem of dam deterioration have never proven to be totally satisfactory. In production situations these dams still deteriorate too rapidly. This requires that the welding process be stopped, the apparatus be disassembled, and the dams replaced.

A further problem is the long setup time required. In production situations the flux dam and the welding head must constantly be positioned on new workpieces and then moved out of the way when the weld is completed. It is desirable to speed up the positioning of the flux dams as much as possible but heretofore flux dams have slowed production because they are awkward to move and must be constantly adjusted. The present invention is directed to overcoming one or more of the problems as set forth above.

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Disclosure of the Invention

In one aspect the present invention is incorporated into a submerged arc welding apparatus having a platform for a supporting workpiece, a traveling welding head mounted for movement with respect to the platform and a flux dam positionable adjacent to the workpiece for granular flux. The improvement disclosed herein includes an elongate flux dam which is stationary during welding and extends for the length of the weld. The flux dam is supported by a support arm that is pivotally connected to an axle mounted on one side of the platform.

The invention also contemplates a method for welding a workpiece wherein the flux dam is pivoted back and forth with respect to the workpiece along an arcuate path utilizing a support arm that is pivotally connected to a shaft mounted on the welding apparatus. The present invention solves the problem of flux dam deterioration by using an elongate stationary flux dam and traveling welding heads. The traveling welding heads cause the point of heat generation to continuously move along the length of the workpiece. Thus the point of highest temperature on the adjacent dam continuously moves along the length of the dam from one end to the other. The present invention also solves the problem of flux dam deterioration by cooling the dam using an attached heat exchanger.

The problem of heat distortion is overcome by using a copper bar that longitudinally expands when heated and a support that permits this thermal

elongation. With regard to minimizing setup time, the flux dams are pivotally mounted on shafts and are moved back and forth using hydraulic cylinders.

Other objects and features of the present invention are also set forth below and are illustrated in the attached drawings.

Brief Description of the Drawings

Fig. 1 is a partial perspective view in cross section and broken away of an embodiment of the present invention.

Fig. 2 is a front elevational view, broken away and in cross section taken along line 2-2 of Fig. 1.

Figs. 3A and B are partial side elevational views of ^* the apparatus of Fig, 1.

Best Mode for Carrying Out the Invention

Figs. 1-3 illustrate a submerged arc welding apparatus according to the present invention. The apparatus includes ^* a stationary platform 6 or table, shown in phantom, which forms the bed of an automatic process welding machine. The welding machine has two traveling welding heads 8, 8' which move along a parallel path with respect to the platform. The process welder and the welding heads are of conventional construction and are designed to weld a workpiece 11 using a submerged arc process. The work piece 11, Fig. 2, includes two side plates 12, 12' a -top plate 14 and a bottom plate 15. The plates are fabricated from - rolled steel and the welding machine joins the plates together to form a rectangular box section. As illustrated in Fig. 2, the welding heads 8, 8' join the margins between the

top plate 14 and the two side plates 12, 12'. During the welding process flux is deposited ahead of the traveling welding heads 8, 8* in a mound 17. The electrodes on the welding heads move through the flux in a manner such that the arc remains unexposed to the atmosphere.

The mounds of flux 17 are partially formed and maintained in place by a flux dam 19. The flux dam is an elongate copper bar of rectangular cross section that is stationary and positioned against the workpiece 11 during welding. As illustrated in Fig. 3, the flux dam extends for the full length of the weld and for the full length of the workpiece. A solid copper bar is used because of its high heat conductivity and durability when exposed to flux and a welding arc. In addition, copper has the quality of not mechanically distorting under conditions of elevated temperature if it is properly secured. The copper flux dam disclosed herein uniformly elongates along its longitudinal axis when heated but does not twist nor create gaps between. he flux dam and the workpiece.

The flux dam 19 is secured to a mounting plate 21 which is designed to minimize thermal distortion of the flux dam and to permit longitudinal thermal elongation. The mounting plate contains- a plurality of lateral slots 22, Fig. 1, located along the edge of the plate beneath the flux dam 19. The slots pass completely through the plates. The purpose of the slots ^' 22 is to allow limited lateral thermal distortion of the mounting plate 21 to occur without distorting the heat exchangers 24. As illustrated in Fig. 1 the slots are spaced apart and between each slot are elongated mounting holes 23.

These holes are elongated along an axis parallel to the longitudinal axis of the flux dam. The flux dam is secured to the mounting plate by bolts, not shown, which pass through the elongated holes. The purpose of the elongated holes is to allow the copper flux dam 19 to elongate longitudinally with respect to the mounting plate without bending or twisting.

The mounting plate 21 is rigidly attached by welding to a heat exchanger 24. The heat exchanger consists of a tubular cooling water conduit that extends for the full length of the flux dam 19. The heat exchanger supports and cools the flux dam and is utilized to.extend the service life of the copper bar. At each end of the heat exchanger is either an inlet or an outlet 25, Fig. 3, for the cooling water.

Each flux dam 19 and heat exchanger 24.is supported for movement by an adjustable, telescoping support arm 26. Each support arm consists of an upper member 27 welded to the bottom of the heat exchanger 24 and reinforced by a pair of gussets 30 and a lower member 28. The upper member 27 engages a channel- shaped end of the lower member 28 and the two members are bolted together to form a rigidly securable arm. The upper ^• and lower members each contain an elongate slot to permit both adjustment and telescoping action between the two members. The support arms telescope in order ^' to provide adjustment to the height of the flux dam 19. This permits the dam to be moved and leveled relative to the workpiece 11 and is also used to level the flux dam if necessary.

The support arms 2β are each pivotally connected at the side of the platform 6 to a supporting pivot pin 32. This pin is mounted to a

frame rail 33 which is part of the frame of the welding apparatus and the platform 6. As illustrated in Fig. 2, each flux dam 19 travels an arcuate path about the pin 32 between a first position adjacent to the workpiece 11 and a second position remote from the workpiece. In the first position the flux dam aides in forming the mound 17 and facilitates heat transfer from the welding arc. In the second position the flux dam is swung out away from the platform 6 and the workpiece 11 so that the workpiece can be loaded and unloaded quickly. The outward swing of the flux dam 19 is arrested by a stop 35 which is contoured to engage the frame rail 33. The stop is rigidly attached to the lower member 28. The flux dams 19, 19' Fig. 2 are moved between the welding and loading positions as_ illustrated in Figs. 1-3 by a plurality of hydraulic actuators 39- These actuators are pivotally connected by pins and brackets to the bottoms of the heat exchangers, 24, 24'. Hydraulic actuators can also be attached be'tween the flux dams and the platform 6 so that the flux dams can be moved individually relative to the platform. Each hydraulic actuator includes a cylinder 40 and an operating arm 41 that extends and retracts in the conventional manner. The actuators are powered by a hydraulic pump 42, Fig. 3 , and a plurality of control valves. The hydraulic actuators 39 maintain the flux dams in intimate contact with the workpiece 11 during welding. The hydraulic actuators lock the dams against the workpiece and tend to stabilize the plates 12-15 prior to welding. In a production situation the dams move back and forth either automatically or by remote control.

Industrial Applicability

The apparatus disclosed herein is used by the Caterpillar Tractor Co. of Peoria, Illinois to fabricate track roller box sections for its Model 245 excavator. ^' The apparatus incorporates a 12M 3509 Fauser Automatic Welder. The platform 6, Fig. 3 , is approximately fourteen feet long and the flux dam 19 is a copper bar having a one and one-half inch square cross section. To place the apparatus in Operation, the flux dams 19, 19' are first moved to the outward position by extending the operating arms 41 of the hydraulic actuators 39. Next, the flow of water through the heat exchangers 24, 24' is started and the plates 12-15 are assembled together on the platform 6 to form the box section.

When the plates 12-15 are assembled as illustrated in Fig. 2, the flux dams 19, 19' are moved into position for welding by retracting the operating arms 41 into the cylinders 40. Thereafter, the welding heads 8, 8' are positioned by the .welding machine and the welding process is commenced. Granular flux is distributed in front of the welding heads in a mound 17- as illustrated in Fig. 2. The welding heads move from one end of the platform to the other and depending on the application make one or- more passes. When the final welding pass is complete, the flux dams 19 are moved apart by actuation of the hydraulic cylinders 39 and the workpiece is either removed or inverted on the platform 6.

It should be appreciated that the welding heads 8, 8' move relative to the stationary flux dam 19, workpiece 11 and platform 6. The point of maximum

temperature elevation thus moves relative to the dam and no one point on the flux dam is continuously subjected to elevated temperatures. The heat exchangers 24 also continuously carry away the heat. It should also be -understood that although the embodiment described herein is disclosed for making linear welds along straight lines, ^' the present invention also contemplates welding along paths of controlled curvature. In this context a flux dam is used that conforms to the path of the welding head and the support arms 26 are relocated to permit the loading and offloading of workpieces.

From the foregoing it can be seen that by using an elongate stationary flux dam and traveling welding heads and by cooling the flux dam with a heat exchanger, the problem of deterioration of the flux dam is overcome. Further, the present invention overcomes the problem of heat distortion by using a water cooled copper bar and an expansion mounting. In addition, set up time is minimized by pivotally mounting the flux dams on pivot pins and moving th'em back and forth using hydraulic cylinders.

Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.