Understanding Common Welding Terms — A Guide for Beginners | MillerWelds

Understanding Common Welding Terms — A Guide for Beginners

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Are you a home hobbyist new to welding? This list of common welding terms and definitions will help you learn the basics.
Closeup image of operator MIG welding in a shop
Welding involves a lot of terms that can be confusing for beginners. Check out these frequently asked questions about common welding terms so you understand the difference between duty cycle and direct current.

Welding term FAQs

Q: What is the difference between stick, MIG and TIG welding?

A: The three main arc welding processes are stick, MIG and TIG. Stick is the informal term for SMAW (shielded metal arc welding), MIG is the informal term for GMAW (gas metal arc welding), and TIG is the informal term for GTAW (gas tungsten arc welding).

Stick welding is an arc welding process that melts and joins metals by heating them with an arc between a covered metal electrode and the work. Shielding gas is obtained from the electrode outer coating, often called flux. Filler metal is primarily obtained from the electrode core.

MIG welding is also sometimes referred to as solid wire welding. It is an arc welding process that joins metals by heating them with an arc. The arc is between a continuously fed filler metal (consumable) electrode and the workpiece. Externally supplied gas or gas mixtures provide shielding.

TIG welding is a welding process that joins metals by heating them with a tungsten electrode, which should not become part of the completed weld. Filler metal is sometimes used, and argon inert gas or inert gas mixtures are used for shielding.

Flux-cored arc welding (FCAW) is another common process. This is an arc welding process that melts and joins metals by heating them with an arc between a continuous, consumable electrode wire and the work. A flux contained within the electrode core provides shielding. Added shielding may or may not be provided from externally supplied gas or gas mixture.

Q: What are common shielding gas types?

A: Shielding gas is the protective gas used to prevent atmospheric contamination of the weld pool. The proper shielding gas for the job depends on the welding process being used and the base material you are welding. A common shielding gas for TIG welding is 100% argon, while a common shielding gas for MIG welding mild steel is 75% argon/25% carbon dioxide mixture.

Q: What is filler metal?

A: The metal or alloy to be added in making a welded joint. The filler metal is what fills the weld joint or gap between the parts. Filler metals come in many different types and sizes (diameters). Spools of solid wire are used in MIG welding, electrodes are used in stick welding and filler rods are used in TIG welding. Solid wire is a continuous length of wire that is wound onto a spool. Electrodes are metal rods with a flux coating that is designed to protect the weld from contamination. Filler rods are solid metal rods used in TIG welding.

Q: What is amperage?

A: Also referred to as current, amperage is the measurement of the flow of electrons moving in a circuit. Amperage is important because the number of amps produced by the power source (220 amps, for example) determines the amount of heat available to melt the filler metal and the workpiece. The more amps your machine provides, the more heat you can use; and the thicker the material being welded, the more amps you will need. There are different types of current used in welding. Alternating current (AC) reverses its direction at regular intervals; it’s commonly used for aluminum welding. Direct current (DC) flows in one direction and does not reverse its direction of flow. DC welding is the preferred form of welding for most applications. It provides a smoother welding output, less spatter and a more stable arc in most cases.

Q: What is voltage in welding?

A: Voltage measures the pressure of the electrons flowing through the electrical current. Voltage does not flow but it causes amperage to flow. Welding voltage controls your arc length, which is the distance between the weld pool and the filler metal at the point of melting within the arc. As your voltage increases, the weld bead will flatten out. A constant voltage (CV) welding power source has output that provides relatively stable, consistent voltage regardless of the amperage output. A constant current (CC) welding power source has limited maximum short-circuit current. Welding power sources are CV, CC or both. Stick and TIG welding use CC because they require a stable current to maintain a consistent arc length and prevent the electrode from sticking to the workpiece. MIG and flux-cored welding use CV because they require a stable voltage to maintain a consistent wire feed speed and prevent the welding arc from becoming unstable.

Q: What is arc control?

A: The arc is the physical gap between the end of the electrode and the base metal. Arc control refers to the ability to adjust the drive of the electrode in stick welding specifically to achieve more or less penetration into the weld joint. A machine that allows you to adjust these “dig” settings watches the arc voltage and will boost output amperage when the arc length falls into low volts.

Q: What does duty cycle mean in welding?

A: Duty cycle is the number of minutes out of a 10-minute time period an arc welding machine can be operated at its maximum rated output. Take for example a machine rated for 60% duty cycle at 300 amps. This means that at 300 amps the machine can be used for six minutes and then must be allowed to cool with the fan motor running for four minutes.

Q: What is polarity in welding?

A: An electrical circuit is formed when a welding power source is turned on. The circuit has either a positive or negative pole, and this property is referred to as polarity. Polarity directly impacts the quality and strength of your weld. There are two types of polarity: direct current electrode negative (DCEN, which is also called straight polarity) and direct current electrode positive (DCEP, which is also called reverse polarity). The difference between these two is the direction of current flowing through the welding circuit, depending on whether the electrode lead and work lead are connected to the negative terminal or the positive terminal. Welding processes run in either DCEN/straight polarity or DCEP/reverse polarity.

Q: What are welding leads?

A: A welding lead is an encased cable of stranded wire used to conduct electricity and power an electrode from a welding machine. It may also be called an electrode cable. It connects the welding power source to the ground clamp and the electrode holder in stick welding. On a Millermatic® or Multimatic® power source, this cable connects to a Dinse connector on the front of the machine.

Q: What is slag?

A: Slag is the hardened layer left on the top of a weld made using MIG, flux-cored or stick welding. It protects the weld from oxidation and atmospheric contamination. It also helps keep the molten weld pool in the joint as it cools, which is especially important for out-of-position welding. Slag can be removed after welding or in between passes by chipping or grinding.

Q: What is porosity?

A: Porosity is a cavity-type defect in a finished weld caused by gas entrapment during solidification of the weld. It’s a common problem in MIG welding.

Q: What is spatter?

A: Spatter refers to the droplets of molten material blown away from the welding arc. These particles do not become part of the completed weld, but they can stick to the metal workpiece and require chipping or grinding off after welding.

Q: What are a stinger and a whip?

A: Stinger is another name for the stick electrode holder in stick welding. The term whip refers to the cable connected to the stick electrode holder or stinger.

Q: What does the puddle or pool refer to in welding?

A: Weld puddle and weld pool are terms that are often used interchangeably and refer to the molten metal produced while the weld is being made, prior to its solidification as weld metal.

Q: What are the toes of the weld?

A: The weld toe refers to the junction of the weld face and the base metal. This term is often used when discussing how the sides of the weld penetrate the base metal. In a cold weld, the toes aren’t tied in properly. In a too-hot weld, the toes dig in too much.

Q: What is the weld face?

A: The exposed surface of a weld on the side from which welding was done.

Q: What is the weld root?

A: The points at which the weld metal intersects the base metal and extends furthest into the weld joint.

Q: What is penetration in welding?

A: Also known as depth of fusion, penetration refers to the distance that the fusion extends from the surface into the base metal or previous bead during welding. A weld needs enough penetration to be sound.

Q: What is a tack weld?

A: A frequently used technique in welding, tack welding fastens two pieces of metal together by welding them at various isolated points. It’s often a method of temporary welding that serves to hold parts together for final welding.

Q: What is a stitch weld?

A: Stitch welding, also called intermittent welding or skip welding, involves laying multiple welds with spacing between them rather than having a long, continuous weld.

Q: What is an alloy?

A: The term alloy may be used in reference to the base material being welded or to the filler metal being used. An alloy is a substance composed of two or more elements mixed together. For example, 4140 is a very common steel in welding. It’s a low-alloy steel containing chromium, molybdenum and manganese.

Q: What does the phrase “stacking dimes” mean?

A: This welding slang term is used to describe a good-looking weld bead, one that looks like a shiny string of dimes stacked on top of each other. It’s most frequently used to describe the weld bead produced in TIG welding.

Q: What is frying bacon in welding?

A: This term is a common descriptor for the sound produced during MIG welding. The frying sound — sizzle with an occasional pop — usually means your welder is set up properly and you are laying a quality bead.

Q: What does it mean to weave?

A: Weaving is a welding technique. Also referred to as oscillating or stitching, it is the technique of moving the electrode or gun from side to side to wash the sides of the weld pool into the base material.

Click here to download a glossary of common welding terms.