Introduction to Welding Technology
Welding is a fabrication process used to join materials, usually metals or thermoplastics, together. During welding, the pieces to be joined (the workpieces) are melted at the joining interface and usually a filler material is added to form a pool of molten material (the weld pool) that solidifies to become a strong joint.
In contrast, Soldering and Brazing do not involve melting the workpiece but rather a lower-melting-point material is melted between the workpieces to bond them together.
Types of Welding
1. Arc Welding:
- Shielded Metal Arc Welding (SMAW):
- Gas Metal Arc Welding (GMAW)
- Gas Tungsten Arc Welding (GTAW)
3. Resistance Welding
4. Energy Beam Welding
5. Solid-State Welding
Welding Terminology
There is some special technical vocabulary (or language) that is used in welding.
Filler Material: When welding two pieces of metal together, we often have to leave
a space between the joint. The material that is added to fill this space during the
welding process is known as the filler material (or filler metal). Two types of filler
metals are commonly used in welding are welding rods and welding electrodes.
Flux: Before performing any welding process, the base metal must be cleaned form impurities such as oxides (rust). Unless these oxides are removed by using a proper flux, a faulty weld may result. The term flux refers to a material used to dissolve oxides and release trapped gases and slag (impurities) from the base metal such that the filler metal and the base metal can be fused together. Fluxes come in the form of a paste, powder, or liquid. Different types of fluxes are available and the selection of appropriate flux is usually based on the type of welding and the type of the base metal.
Types of Welded Joints
Butt Joint: it is used to join two members aligned in the same plane. This joint is frequently used in plate, sheet metal, and pipe work.
Corner and Tee Joints: these joints are used to join two members located at right angles to each other. In cross section, the corner joint forms an L-shape, and the tee joint has the shape of the letter T.
Lap Joint: this joint is made by lapping one piece of metal over another. This is one of the strongest types of joints available; however, for maximum joint efficiency, the overlap should be atleast three times the thickness of the thinnest member of the joint.
Edge Joint: it is used to join the edges of two or more members lying in the same plane. In most cases, one of the members is flanged, as seen in the figure. This type is frequently used in sheet metal work for joining metals 1/4 inch or less in thickness that are not subjected to heavy loads
4. Energy Beam Welding
5. Solid-State Welding
Welding Terminology
There is some special technical vocabulary (or language) that is used in welding.
Filler Material: When welding two pieces of metal together, we often have to leave
a space between the joint. The material that is added to fill this space during the
welding process is known as the filler material (or filler metal). Two types of filler
metals are commonly used in welding are welding rods and welding electrodes.
- Welding Rod: The term welding rod refers to a form of filler metal that does not conduct an electric current during the welding process. The only purpose Introduction to Non-Destructive Testing Techniques of a welding rod is to supply filler metal to the joint. This type of filler metal is often used for gas welding.
- Electrode: In electric-arc welding, the term electrode refers to the component that conducts the current from the electrode holder to the metal being welded. Electrodes are classified into two groups: consumable and non consumable.
- Consumable electrodes not only provide a path for the current but they also supply filler metal to the joint. An example is the electrode used in shielded metal-arc welding.
- Non-consumable electrodes are only used as a conductor for the electrical current, such as in gas tungsten arc welding. The filler metal for gas tungsten arc welding is a hand fed consumable welding rod.
Flux: Before performing any welding process, the base metal must be cleaned form impurities such as oxides (rust). Unless these oxides are removed by using a proper flux, a faulty weld may result. The term flux refers to a material used to dissolve oxides and release trapped gases and slag (impurities) from the base metal such that the filler metal and the base metal can be fused together. Fluxes come in the form of a paste, powder, or liquid. Different types of fluxes are available and the selection of appropriate flux is usually based on the type of welding and the type of the base metal.
Types of Welded Joints
Butt Joint: it is used to join two members aligned in the same plane. This joint is frequently used in plate, sheet metal, and pipe work.
Corner and Tee Joints: these joints are used to join two members located at right angles to each other. In cross section, the corner joint forms an L-shape, and the tee joint has the shape of the letter T.
Lap Joint: this joint is made by lapping one piece of metal over another. This is one of the strongest types of joints available; however, for maximum joint efficiency, the overlap should be atleast three times the thickness of the thinnest member of the joint.
Edge Joint: it is used to join the edges of two or more members lying in the same plane. In most cases, one of the members is flanged, as seen in the figure. This type is frequently used in sheet metal work for joining metals 1/4 inch or less in thickness that are not subjected to heavy loads
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