INTRODUCTION TO WELDING AND FABRICATION TECHNOLOGY

The term “metal fabrication” refers to the processes used to create a finished part or product by shaping, adding, or removing material from a raw or semi-finished metal workpiece. The following headings below provides an overview of the types of fabrication processes available, outlining what they entail, what materials they accommodate, and what applications for which they are.

Cutting
Cutting is the process of separating a metal workpiece into smaller pieces. There are several cutting methods employed, each of which offers unique characteristics that make it suitable for different applications.
The oldest method of cutting is sawing. This process utilizes cutting blades either straight or rotary to cut materials into different sizes and shapes. Automatic sawing operations allow manufacturers to achieve greater precision and accuracy in their cut parts without sacrificing processing speed.
One of the newer methods of cutting is laser cutting. This process employs the use of a high-powered laser to cut materials to the desired shape and size. Compared to other cutting processes, it offers higher cutting precision and accuracy, especially for complex and intricate part designs.
Machining
Machining is a subtractive process, meaning it creates parts and products by removing material from the workpiece. While some manufacturers continue to use manual machining technologies, many are turning to computer-controlled machining equipment, which offers tighter tolerances, greater consistency, and faster processing speed.
Two of the most common CNC machining processes are CNC milling and CNC turning. CNC milling operations rely on rotating multi-point cutting tools to remove excess metal from a workpiece. While the process is often used as a finishing procedure, it can be used to complete an entire project. CNC turning operations use single-point cutting tools to remove material from the surface of a rotating workpiece. This process is ideal for the creation of cylindrical components with precise internal and external elements.
Welding
Welding refers to the process of joining materials—typically metals such as aluminum, cast iron, steel, and stainless steel—together using high heat and pressure. There are many welding methods available—including tungsten inert gas (TIG) welding, metal inert gas (MIG) welding, shielded metal arc welding (SMAW), and flux-cored arc welding (FCAW)—all of which entail different welding materials and skill requirements. Manufacturers can employ manual or robotic welding technology depending on the size and complexity of the welding project.
Punching
Punching operations utilize specialized tooling (i.e., punch and die sets) and equipment (i.e., punch presses) to cut out sections from flat workpieces in medium to high production runs. CNC punching equipment is used for light and heavy metalworking applications.
Forming
Forming involves the shaping and reshaping of solid metal into the desired part or product. There are several different forming processes available, including bending, drawing, extrusion, forging, pulling, rolling, and stretching. They are commonly used with sheets and plates—as well as other material forms—to produce simple components to complex assemblies.
Metal fabrication encompasses a wide range of processes, including, but not limited to, cutting, machining, welding, punching, shearing, and forming.
WELDING
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
Types of Welding
There are many different types of welding processes and in general they can be
categorized as:
Arc Welding: A welding power supply is used to create and maintain an electric arc
between an electrode and the base material to melt metals at the welding point. In
such welding processes the power supply could be AC or DC, the electrode could be
consumable or non-consumable and a filler material may or may not be added.
The most common types of arc welding are:
1. Shielded Metal Arc Welding (SMAW): A process that uses a coated
consumable electrode to lay the weld. As the electrode melts, the (flux)
coating disintegrates, giving off shielding gases that protect the weld area
from atmospheric gases and provides molten slag which covers the filler
metal as it travels from the electrode to the weld pool. Once part of the weld
pool, the slag floats to the surface and protects the weld from contamination
as it solidifies. Once hardened, the slag must be chipped away to reveal the finish weld
2. Gas Metal Arc Welding (GMAW): A process in which a continuous and
consumable wire electrode and a shielding gas (usually an argon and carbon
dioxide mixture) are fed through a welding gun.
3. Gas Tungsten Arc Welding (GTAW): A process that uses a nonconsumable
tungsten electrode to produce the weld. The weld area is protected from
atmospheric contamination by a shielding gas, and a filler metal that is fed
manually is usually used.
Gas Welding: In this method a focused high temperature flame generated by gas
combustion is used to melt the workpieces (and filler) together. The most common
type of gas welding is Oxy-fuel welding where acetylene is combusted in oxygen.
Resistance Welding: Resistance welding involves the generation of heat by passing
a high current (1000–100,000 A) through the resistance caused by the contact
between two or more metal surfaces where that causes pools of molten metal to
be formed at the weld area. The most common types of resistance welding are
Spot-welding (using pointed electrodes) and Seam-welding (using wheel-shaped
electrodes).
Energy Beam Welding: In this method a focused high-energy beam (Laser beam or
electron beam) is used to melt the workpieces and thus join them together.
Solid-State Welding: In contrast to other welding methods, solid-state welding
processes do not involve the melting of the materials being joined. Common types
of solid-state welding include; ultrasonic welding, explosion welding,
electromagnetic pulse welding, roll welding, friction welding (including friction-stir-
welding), etc.
Special technical language used in welding. The
basic terms of the welding language include:
1. 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).
2. 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 of a welding rod is to supply filler metal to the joint. This type of filler metal is often used for gas welding.
3. 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.
4. 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.

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