Craftsman Shielded Metal Arc Welding key terms

The intense visible and ultraviolet light from an electric arc that can burn exposed skin and damage eyes. Welders prevent it with a helmet, proper lens shade, and shielding around the work area.

A number on a welding filter lens that states how much visible light it blocks. The number rises with arc current and with the amount of time spent under the helmet.

Airborne metal oxide particles and gases produced when the electrode, flux, and base metal melt. Exposure is controlled by ventilation, fume extraction, and a respirator where required.

A written authorization issued before welding or cutting in an area where fire is possible. It records the fire watch, the area preparation, and the checks required after work ends.

A person assigned to stay in the welding area during hot work and for a set time afterward, watching for smoldering material and ready to sound an alarm or use extinguishing equipment.

The direction current flows between electrode and work: direct current electrode negative, electrode positive, or alternating current. Polarity affects penetration, deposition, and which electrodes will run properly.

A direct current setup where the electrode is the negative terminal and the work is positive. It sends more heat into the work, giving deeper penetration, and is used with certain electrodes.

The energy delivered to the weld per unit of length, found from amperage, voltage, and travel speed. It affects penetration, cooling rate, hardness, and distortion.

Unwanted change in the shape or size of a welded part caused by uneven heating and cooling. It is controlled by balanced sequences, tacking, preheat, and backstep welding.

The voltage present at the electrode holder when the machine is on but no arc is burning. It creates the shock hazard in SMAW, so holders and cables must be insulated and dry.

The percentage of a ten-minute period a power source can run at a rated current without overheating. A 60 percent duty cycle at 200 amps allows six minutes of welding.

A welding machine whose output current changes little when arc length changes. SMAW uses this characteristic so the welder's hand movements do not wildly change amperage.

A calculated number that shows how readily a steel will harden when welded, based on its carbon and alloy content. Higher values call for more preheat and stricter procedure control.

Heating the base metal before welding to slow cooling and reduce hardening, hydrogen cracking, and shrinkage stress. The required temperature depends on steel type, thickness, and code.

A dark oxide layer formed on hot-rolled steel during cooling. It must be removed from the weld area because it causes porosity, slag, and incomplete fusion if trapped.

The angle between the beveled face of a joint edge and a line perpendicular to the surface. It controls how much weld metal fills the groove and how well the root fuses.

The gap left between the two members at the bottom of a joint before welding. The gap lets the arc reach the root and allows full penetration of the root pass.

The flat, unbeveled portion of the joint edge at the root. It supports the root pass, helps prevent burn-through, and its width is set by the procedure.

A short weld used to hold parts in alignment before the main weld is made. Tacks must be the right size and be fully fused so they can be consumed by the root pass.

The alignment and clearance between the parts of a joint before welding. Poor fit-up produces gaps, mismatch, and distortion, and it cannot be corrected by welding technique alone.

The code stamped on the electrode, such as E7018, that tells its tensile strength, welding position, coating type, and current. Each part of the number has a fixed meaning.

An electrode whose coating is formulated to add very little hydrogen to the arc, such as E7018. It reduces the risk of hydrogen cracking in steels and must be kept dry.

Heating low-hydrogen electrodes in a controlled oven to a specified temperature and time to drive off absorbed moisture, restoring them to the condition the manufacturer requires.

A heated storage cabinet that keeps opened low-hydrogen electrodes dry and ready for use, typically holding them at a lower temperature than the baking oven.

Wandering or deflection of the arc caused by magnetic forces, often near the end of a joint or beside heavy steel. It causes uneven beads and spatter, and is reduced by changing the work lead position.

The gap between the electrode tip and the molten weld pool. Too long a gap spreads the arc, loses shielding, and spatters; too short a gap sticks the electrode to the work.

The angle of the electrode measured from vertical along the direction of travel. A slight drag angle pushes the arc and protects the pool; too much angle causes uneven penetration and slag.

The angle of the electrode measured from perpendicular to the joint, in the plane across the weld. It is usually 45 degrees for a fillet weld and splits heat between the two members.

A narrow bead made with little or no side-to-side movement. It is used for root passes, thin material, and where a small heat input is needed to limit distortion.

A bead made by moving the electrode side to side in a controlled pattern along the joint. Weaving spreads heat, fills wide joints, and must stay within limits set by the procedure.

The first pass deposited in a joint, which fuses the root faces and sets the shape of the weld. It controls penetration and often determines whether the joint passes inspection.

The pass deposited immediately after the root pass, before the weld cools. It refines the root, removes slag and defects from it, and prevents cracking in thick sections.

Delayed cracking in steel caused by hydrogen trapped in the weld and by restraint and hardness. It can appear hours or days later and is prevented by dry electrodes, preheat, and controlled cooling.

Nonmetallic material trapped in the weld because it was not fully removed between passes or because the arc failed to float it out. It shows on radiographs as dark, irregular lines.

Small cavities or gas pockets trapped in solidified weld metal. It comes from moisture, dirt, or paint on the metal, too long an arc, or a wet electrode.

A groove melted into the base metal beside the weld toe or root that is left unfilled. It thins the section and concentrates stress, and comes from too much current or wrong travel angle.

A condition where weld metal does not bond to the base metal or to the previous pass. Causes include low heat input, wrong angle, fast travel, or uncleaned surfaces.

A drawing notation made of a reference line, an arrow, and one or more weld symbols that tells the welder where and how to weld. The tail may carry the procedure.

A triangular weld joining two surfaces at an angle, usually 90 degrees. Its size is the leg length, and it is the most common weld in structural steel work.

A weld made in a groove between two members, such as a V, U, or square groove. It usually needs joint preparation and gives full penetration when welded from one or both sides.