Like sewing up a seam, there are many ways to run a weld bead along a joint. Yet unlike tailors, welders frequently need to perform their work in an awkward position. And along with the personal discomfort, gravity affects how molten metal gets deposited. If you're welding overhead (i.e. reaching up to apply the weld), for instance, you've got to move fast or the weld metal will end up on your face shield, and not in the joint. After preparing a joint for welding and dialing in the right machine settings, welders use a variety of techniques and hand strokes available to get the job done.
Generally speaking, torch manipulation is much the same whether you're feeding the weld pool with a separate filler rod, or using a wirefeed or stick electrode. (If you're not already familiar with welding processes, click here for an overview.) Below you'll find a description of the four most common bead types used both in the shop and field:
This is a straightforward, easy to perform bead in which you either "drag" (pull) or push the torch across the joint with minimal (if any) side-to-side movement. Dragging means the electrode is pointed back towards the puddle. This enables maximum penetration and a robust-looking weld.
For heat-sensitive or thin metals, or when welding in the vertical-up position, welders "push" the torch, which means pointing the electrode forward. (See photo above.) When welding vertical-up, the molten metal wants to fall downward, so directing the heat away from the puddle allows the weld to solidify quickly. The drawback of pushing is that penetration into the base metal is much less than when dragging (pulling) the torch.
Stringer beads are generally not very wide and can be used in any welding position. Even though you're moving in a straight line, it's still important to make sure you get "tie in" with the toe of the weld on either side. Remember, the object of welding is not just to fill a joint with new metal. It's critical to get fusion between the weld and the base metal. Sometimes, moving the torch along slowly enough so the weld puddle flows over both sides of the joint is all it takes. Other times a slight side to side manipulation is necessary, as illustrated below:
Again, the side-to-side manipulation is slight. Otherwise you'd have a weave bead. Stringer beads are also used in hardfacing, a surfacing operation that helps extend the life of scoops, fenders, plows and other exterior metal parts on industrial equipment. Here the beads are not meant to fuse the base metal, but to create a protective surface over it.
For wider welds, you can weave from side to side along a joint. For a fat joint, weaving is the fastest way to knock off a weld. This is especially true in the case of groove welds on thick stock. Weaves are also common on fillet welds.
There are different types of weaves, and every welder has his or her favorite. It can be a zig-zag, crescent or curlycue. Besides allowing a wider bead, weaving is used to control heat in the weld puddle. Moreover, you'll generally want to pause on each side of the weld to achieve good tie in and prevent undercutting of the edges. When you move across the center of the joint, however, you'll generally want to hurry. Otherwise you may end up with a high crown. It's better to have a flat or just slightly convex weld face when you weave.
A triangle weave is useful when you need to fill a steep pocket. In vertical-up welding, it allows you to build a sort of shelf, which keeps the molten metal from sliding downward.
To keep the puddle from overheating or expanding, you can try a semi-circle weave, with the center point or your stroke crossing the front of the puddle (or just ahead of it). If you want more heat in the puddle, weave the semi-circle (or crescent) back through the puddle, as shown in the drawing above.
Weaving in the overhead position, can be a challenge, since gravity can pull the molten metal out of the weld. Even with practice, laying down an overhead weave bead a half inch or wider can be a tall order. But welders learn to do it, since weaving saves time (compared to stringers).
On open groove welds, a stick welder typically performs a whipping motion with his or her wrist on the root pass, the first weld operation performed. The objective is to fuse the work plates together at the bottom with a flat bead of weld metal. The most common stick electrodes for this task are E6010 and 6011 "fast-freeze" rods, used on low-carbon steel.
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Groove weld diagram (left) an a pipe joint with a keyhole created by welding (ostensibly) from the top down.
The welder drives the electrode up through and along the gap. This is essential to achieving complete penetration. You'll see a keyhole appear in the opening at the head of the puddle. This demonstrates that the torch heat is reaching both sides of the base metal. Before the keyhole expands beyond control, you'll whip the rod a little upward and ahead of the weld. This action cools everthing down. The keyhole size stays the same, and the bead at the back of puddle solidifies. At that moment, you whip back to the molten puddle and another drop of weld metal should fall off your rod (if you're stick welding).
All of this happens pretty quickly. The rate of whipping is determined by the level of heat you observe in the weld. When you first start welding, for instance, you may not be whipping at all. By the time you reach the end of the weld, you may be flicking your wrist at a steady clip because of the high heat now flowing through the base metal. The following video shows the technique:
This is one of the most difficult strokes that welders learn. In addition to watching the puddle, you also have to maintain the size of the keyhole. If it gets too big (i.e. more than twice the diameter of the rod), then you won't be able to fuse the sides together. That's why control of heat is crucial during a root pass. In addition to proper joint design and welding machine settings, you can control the size of the hole with the frequency of your whip strokes.
A variation of the whip motion is called a J-weave. It's a combination of the crescent and whip strokes, and is used on the second (aka "hot") pass of a V-groove joint. Here, you move your E6010 or other fast-freeze electrode from one toe to the other, pausing briefly on each side, and then whip the rod ahead and upward along one side of the joint for a moment. For this task, more arc length is helpful. And just as you would on a root pass, after whipping ahead, you'll whip back to the next open area on the left (or right) toe of the weld, and repeat the stroke.
On a root pass for pipe, welders often use a TIG torch for a more precise bead than in stick welding. The process usually incorporates a specific hand stroke known as "walking the cup". The cup in this case is the ceramic insulator surrounding the torch tip and the welder drags it back and forth along the base metal on either side of the joint,. The video below describes the technique:
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