Clad welding on an inclined surface

Submerged arc strip cladding of the workpiece is carried out on a workpiece which has a surface inclined to the horizontal transverse to the direction of the welding progress. The flux burden is skewed in a zone overlaying the molten metal area with a heavier burden being located on the downhill side of the weld than on the uphill side.

BACKGROUND OF THE INVENTION 
The invention relates to weld cladding of metallic workpieces and in 
particular to the cladding of the workpiece having a surface inclined in a 
direction transverse to the direction of weld travel. 
It is known to plate or clad various metallic workpieces by depositing weld 
metal by submerged arc electric welding. Multiple rod or strip electrodes 
are used for the purpose of achieving a reasonable width of surface 
coverage on a single pass. A typical application of such a cladding method 
would be to clad the interior surface of a cylindrical pressure vessel 
with a corrosion resistant alloy such as stainless steel. On occasion 
there is a sloped internal surface where the thickness of the wall plate 
changes, for instance where the straight portion of the pressure vessel 
ends and a hemispherical head begins. Such an inclined surface would be at 
approximately 10.degree. with the axis of the vessel and run for a length 
of six to eight inches. 
While the vessel may be placed in a horizontal position and rotated on 
rolls for the purpose of strip cladding, the massive size of many vessels 
makes it difficult to change the orientation of the axis so that the 
inclined surface can be placed in a horizontal position. Accordingly, 
there is a need for clad welding an inclined surface. 
It is required that the inside surface after cladding be smooth for 
purposes of ultrasonically testing the structure. This requires grinding 
in many cases, and any uneven weld deposit increases not only the cost of 
the material being deposited but the cost of removal of the excess. In 
prior art methods there were considerable problems with the weld metal 
running down the slope. Accordingly, each weld bead laid down was limited 
in width and, in fact, has a substantial overlap of the previously 
deposited bead. This required substantial grinding of all of the overlap 
material. 
Furthermore, the overlap portion would have a different composition than 
the portion which was deposited on the base metal. The dilution of the 
weld deposit by the base metal would occur only where it was deposited 
directly on the base metal with such dilution being absent in the overlap 
portion. 
Since the molten metal has a high resistance to electric current flow, 
there tended to be a burn through to the base metal in the shallow end of 
the weld metal with resultant undercutting of the base metal. Irregular 
beads formed which could not be controlled. 
SUMMARY OF THE INVENTION 
In a submerged arc cladding process carried out on an inclined surface 
uniform deposition of the weld metal is achieved by skewing the flux 
burden over the molten metal area. The flux burden being heavier on the 
downhill side of the weld exerts a force greater than the lesser burden on 
the uphill side so as to maintain the liquid metal within an area 
essentially parallel to the surface being plated. This may be accomplished 
by locating the flux chutes on the downhill side of the weld so that the 
natural flow of the flux forms this varying flux burden or it may be 
accomplished by baffling the deposited flux to obtain the desired 
variation in flux burden. 
It is an object of the invention to clad an inclined surface without arc 
burn through on an uphill side and with the resultant clad being 
essentially parallel to the surface being clad, and without excessive 
overlaps between the deposited layers.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
U.S. Pat. No. 4,027,135 issued to John Barger illustrates an apparatus and 
method for submerged arc strip cladding of metallic workpieces. It 
includes a flux breaker and electromagnetic poles located adjacent the 
molten flux area which are pulsated to agitate the pool of flux. Such 
members are efficacious when used with the present invention. 
A workpiece 10 has a surface inclined at 10.degree. from the horizontal. 
Feed roll 12 moves the strip electrode 14 downwardly while electric 
current is supplied to the electrode through contact tip 16. 
The workpiece 10 is translated to the right in FIG. 1 as indicated by arrow 
18 with respect to the electrode 14. The left side of this figure 
illustrates the leading side of the welding head or strip feeder with the 
right-hand side illustrating the trailing side. 
An arc 20 is struck between the electrode 14 and the workpiece 10 whereby 
the electrode is melted and deposited in the form of a molten pool 22. 
This forms a molten metal zone 22 since the deposited weld metal 
solidifies by location 24. The molten zone is overlaid by a volume of 
molten flux 26 and unmelted flux 28. A zone of unmelted flux 30 also 
exists on the leading side for the purpose of submerging the arc. 
Referring to FIG. 3, the previously deposited weld metal 32 is on the 
downhill side of the newly deposited weld metal 22. 
As best seen in FIGS. 1 and 4 the leading flux guide 34 deposits by natural 
flow a volume of flux 30 to the workpiece. The centerline of this flux 
guide is located on the downhill side of the centerline of the electrode 
14. The natural angle of repose of the flux causes the flux to pour 
outwardly with edges 36 in a direction transverse to the motion. The 
height and location of the flux guide are located such that the arc at the 
uphill side of the workpiece 10 is submerged in the flux. While a portion 
of this flux is consumed by the electrode 14, a significant pile of the 
flux remains on the downhill side of the workpiece to support later added 
flux or to naturally cascade into a similar pile after it passes the 
electrode. It can be seen that this already establishes an unequal flux 
burden with a greater and heavier burden of flux on the downhill side of 
the deposited weld metal as compared to the uphill side. 
A trailing flux guide 40 is located on the trailing side of the electrode 
with the flux surface cascading forward as indicated by surface 42 with 
the volume 44 being carried with the workpiece away to a point of removal. 
The flux guide 40 is also located downhill of the centerline of the 
electrode 14 with the natural angle of repose of the deposited flux again 
forming an increased burden on the downhill side of the deposited weld 
metal over the molten zone. 
Modification of the imbalance of flux burden, to an extent experimentally 
determined, is accomplished by the baffle plow 50. With respect to the 
already deposited flux which is being carried along with the workpiece 
this plow urges the flux in a downhill direction thereby effecting a 
modification of the flux burden imbalance. The flux at this time is 
flowing downwardly from the shoot toward the electrode and simultaneously 
being carried away from the electrode with the workpiece. 
This imbalanced flux load produces a greater static force on the downhill 
portion of the molten flux and molten metal. It accordingly produces a 
lower static pressure on the uphill portion. The appropriate amount of 
skewing required is a function of the relative density of the molten metal 
and the deposited flux. Since the flux is lighter than the molten metal, 
skewing significantly greater than the slope of the workpiece is required 
in this opposite direction. 
An alternate method of achieving the skewed distribution of flux is 
illustrated in FIG. 5. The trailing flux shoot 64 has an opening at the 
lower end with this opening being located a distance 66 from the workpiece 
10 which is significantly greater than the distance 68 at the uphill end. 
While the difference in elevation at these two locations cannot exceed the 
angle of repose, an imbalance in the flux loading is established at the 
flux guide from which the flux cascades forwardly to achieve a related 
flux imbalance. 
The particular dimensions and shape of the baffle must be selected and 
modified in accordance with the variables experienced including the 
density of the deposited weld metal and the density of the flux. Also the 
angle of the slope of the inclined surface and speed of welding will be 
factors. 
The results of experimental operation are indicated on FIGS. 6 through 9. 
The workpiece 70 was set up with a 10.degree. angle in a direction 
transverse to the direction of clad travel. It was clad by a series of 
stringer beads 72 starting at the lower side of the material. A strip 1" 
wide by 0.025" thick was used to deposit a clad of Type 304 stainless 
material. FIG. 6 indicates the result using conventional prior art methods 
including a uniform flux burden. 
FIG. 7 illustrates the form of beads 74 obtained using the method of this 
U.S. Pat. No. 4,027,135 but with a uniform flux burden. The isolation of 
the molten flux in accordance with the teachings of that patent operate to 
widen the deposited bead but the shingling remains. 
FIG. 8 illustrates the form of beads 76 deposited using a skewed flux 
burden in accordance with the present invention but without the use of the 
electromagnets. FIG. 9 illustrates the form of beads 78 obtained using the 
skewed flux burden of the current invention as well as the pulsating 
electromagnets. In carrying out this experiment the cladding flux was fed 
to the welding arc zone in a controlled manner to cause a pressure 
difference across the width of the weld deposit. This was accomplished by 
flux chutes to divert the flux from the top side of the deposit to the 
lower, leaving only a minimum burden to protect the arc at the upper side. 
The welding conditions were 550 amps, 28 volts direct current reverse 
polarity, and 10" per minute travel. Welding was carried out with a 1" 
pitch and a 3/16" clad thickness was deposited.