>>> Welding Beads and Parameters <<<

Like sewing up a seam, there are many ways to run a weld bead along a joint. More often than not, welders have to perform their welds out-of-position. Along with the personal discomfort, gravity can affect how molten metal gets deposited. If you're welding overhead, for instance, you've got to move fast or the weld will end up on your face shield, not in the weld joint. In addition to adjusting the machine settings, you'll learn choose from a variety of hand strokes in order to get the job done.

Torch manipulation is much the same whether you're feeding the weld pool with a separate filler rod, or using a MIG or stick welder. Click here for an overview of different welding processes and machine types. Below you'll find a description of three common bead types :

Stringer beads

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.

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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.

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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:

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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.

Weave Beads

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.

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There are different types of weaves, and every welder has his or her favorite. It can be a zig-zag, crescent, triangle or curlycue. Naturally, your current setting , travel speed, arc length and other variables figure into the equation when performing a weave. More on welding parameters below.

Besides allowing a wider bead, weaving is used to control heat in the weld puddle. It's also important to keep the puddle at a consistent size as you pause on each side of the weld to achieve good tie in. 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.

Pausing on each side will also prevent any undercut of the base metal along the toes of the weld. Weaving in the overhead position, however, 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.

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.

Whip Motion

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.

Welding Parameters

As mentioned above, producing a weld bead that's the right size, shape and depth involves many variables. Arc welding students are taught to remember most of them using the acronym CLAMS :

Current - Amperage generally dictates the size of the weld bead if you're moving at the correct speed.

Length of Arc - How close to the work plates the welder holds the arc of a wire or welding electrode can affect the amount of current and heat going into the joint. Held close to the work plates, the current and heat in the weld remains high. Held farther away, the electrode produces less heat and more spatter.

As a general rule, arc length should closely approximate the diameter of the electrode metal. You may increase the length to reduce heat to the puddle, or to limit the deposition of weld metal (as in the whip motion).

Angle - There are two angles in welding. The first is the work angle, which is the relationship between the joint and the torch. Ideally, it's perpendicular, or 90 degrees, except in the case t-joints, where the work angle varies between 30 to 50 degrees. The second angle used in welding is the travel angle. This is the relationship between the torch and line of travel. In order to see the joint and puddle, the welder may tip the rod up to 10 degrees in the direction of travel.

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As you can see in the first diagram, the angle of the torch to the work piece (left) is 90 degrees, allowing maximum heat and current focused down into the open groove joint. Think of this as the front view of the joint. In the diagram on the right, the travel angle involves about a 10 degree tilt along the joint, allowing for a better view of what's going on in the puddle. This is a side view of the joint. When you drag the torch or electrode, the tilt is directed towards the puddle. When you push, the tilt is pointed away from it.

Manipulation - This refers to the micro-movements of the welder's hand guiding the electrode along the joint. Achieving tie-in at the toes is paramount, but it's also important to control penetration in the joint and the heat in the puddle and base metal. A weave, whip, drag or push are all types of manipulation.

Speed - If you move too fast, the size of the weld will be small and get insufficient penetration. Move too slow and you'll end up with an fat weld bead with a high crown, overheated base metal and spatter everywhere.

The following chart shows how some these variables impact a weld bead:

In the last two examples, "WFS" stands for wirefeed speed, which is how MIG and flux cored welding machines regulate current. Notice that when the voltage is too high, the bead is wide and flat. Also, when the rate of voltage is inadequate, the weld bead sits on top of the base metal rather than penetrates into it. So voltage determines the overall profile or geometry of the weld.

By adjusting travel speed, you'll increase or decrease the volume of weld metal that gets deposited along the joint.

Although the photos don't show it, too long of an arc can cause porosity (air bubbles) inside the weld, spatter and undercutting at the toes of the joint. See Weld Defects for more on this subject.

In addition to CLAMS, here are a few other variables to think about when planning a weld operation:

Joint Design and Fit-Up: How you prepare your work plates (or stationary structure) for welding may contribute more to the outcome of the operation than anything else. Your joints, beveled edges, grinded root faces and surfaces should fit together in a smooth and uniform manner before you start the weld. There shouldn't be any burrs, gaps or evenness.

As a student, it's easy to assume that once the metal heats up, everything falls together naturally and all the little rough spots will disappear like magic. In fact, you can make things worse if you don't take the time to do your fit-up correctly. Needless to say, the angle of your beveled sides should be appropriate for the thickness of the metal and the welding process being used. (In MIG welding, steeper angles are possible than in stick welding.) You should also tack your plates and use clamps as needed to prevent the joint from closing up in advance of the weld, or other distortion caused by heat.

Cleaning your weld edges in advance is also important. While some stick electrodes are designed to penetrate through rust and millscale, those impurities can still cause problems. And while low-carbon steel is much easier to work with than other metals, you should still adopt the habit of cleaning or grinding the areas you plan to weld.

Size: The thickness of the base metal should factor into the decision about which diameter electrode, rod, wire or torch tip you use to make the weld, as well as your voltage and/or current settings. There are other things to consider, but metal thickness usually comes first.

Heat Dispersal: Different metals disperse heat differently. The mass of your work pieces also has an effect, with tinier plates heating up much faster than larger ones. Low-carbon steel can be very forgiving when overheated, but other metals may lose their tensile strength or other qualities if you don't monitor the heat going in and out of them.

As you learn more about chemical and mechanical properties, you may decide to include a pre and post heat treatment to the base metal as part of the welding operation. Quenching plates after welding (to cool them down) is a practice that's generally frowned upon after the first semester of welding school. That's because the quench has a sort of traumatizing effect to the metal and can make it brittle. A metallurgy class teaches welders the many forms of heat treatment and their advantages - like hardening, tempering and annealing.

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Stick Welding TheFabricator.com

Intro to Hardfacing
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Improving Your Stick Welding Technique MillerWelds.com

Stringer bead along a lap joint video

Open root v groove butt joint 3G vertical up video

Using CLAMS paramenters in Stick Welding
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