What is Welding?

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld.

What is the importance of welding in engineering?

There is a tremendous importance of welding in engineering, there are even such things as welding engineers ( I am one). Welding is what holds the majority of structures together--bridges, cars, tractors, cranes, buildings, etc...If any engineer does not have a good understand of this very popular joining process major problems can exist, such as failures from designing a joint that is un-wieldable. Most companies these days are trying to hire welding engineers to help with these problems. Welding can get very specialized with more technical metals and applications.

What is Arc welding?

All position capability
Higher deposition rates than SMAW
Less operator skill required
Long welds can be made without starts and stops
Minimal post weld cleaning is required

What is Electron beam welding?

Electron beam welding (EBW) is a welding process, which produces coalescence of metals with the heat obtained from a concentrated beam composed primarily of high-velocity electrons impinging upon the surfaces to be joined. Heat is generated in the work piece as it is bombarded by a dense stream of high-velocity electrons. Virtually all of the kinetic energy-the energy of motion-of the electrons is transformed into heat upon impact.

What is Laser beam welding?

Laser beam welding (LBW) is a welding process, which produces coalescence of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the surfaces to be joined.

What is stick welding?

CShielded Metal Arc Welding (SMAW) is frequently referred to as stick or covered electrode welding. Stick welding is among the most widely used welding processes. The flux covering the electrode melts during welding. This forms the gas and slag to shield the arc and molten weld pool. The slag must be chipped off the weld bead after welding. The flux also provides a method of adding scavengers, deoxidizers, and alloying elements to the weld metal.

Stick Welding Benefits

Equipment used is simple, inexpensive, and portable
Electrode provides and regulates its own flux
Lower sensitivity to wind and drafts than gas shielded welding processes
All position capability

What is GTAW welding?

Gas Tungsten Arc Welding (GTAW) is frequently referred to as TIG welding. TIG welding is a commonly used high quality welding process. TIG welding has become a popular choice of welding processes when high quality, precision welding is required.
In TIG welding an arc is formed between a nonconsumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool. If filler wire is used, it is added to the weld pool separately.

Arc Welding Benefits

Welds can be made with or without filler metal
Precise control of welding variables (heat)
Free of spatter
Low distortion

Resistance Welding

Resistance Spot Welding (RSW), Resistance Seam Welding (RSEW), and Projection Welding (PW) are commonly used resistance welding processes. Resistance welding uses the application of electric current and mechanical pressure to create a weld between two pieces of metal. Weld electrodes conduct the electric current to the two pieces of metal as they are forged together.
The welding cycle must first develop sufficient heat to raise a small volume of metal to the molten state. This metal then cools while under pressure until it has adequate strength to hold the parts together. The current density and pressure must be sufficient to produce a weld nugget, but not so high as to expel molten metal from the weld zone.

Resistance Welding Benefits

High speed welding
Easily automated
Suitable for high rate production
Economical

Application of welding

Welding find its applications in automobile industry , and in the construction of buildings, bridges and ships submarines, pressure vessels, offshore structure, storage tanks oil, gas and pipelines, girders, press frames, and water turbines.
In making extensions to the hospital buildings, where construction noise is required to be minimum, the value of welding is significant
Rapid progress in exploring the space has been made possible by new methods of welding metallurgy. The aircraft industry cannot meet the enormous demands for aero planes, fighter and guided planes, spacecrafts, rockets and missiles without welding.
The process is used in critical application like the fabrication of fission chamber of nuclear power plants.
A large contribution, the welding has made to the society, is the manufacturer of household product like refectories, kitchen cabinets, dishwashers and other similar items

Important definition

Adhesive bonding	A process that binds materials together using a non-metallic material. Paste, glue, and tape are examples of common adhesives
Aluminum	A non-ferrous, silvery-white metal that is soft and light. Aluminum is one of the most difficult metals to weld.
American Welding Society	The non-profit society that regulates the industrial standards for welding.
Arc	The area in which electricity jumps from the electrode to the workpiece. The heat generated by the arc melts the base metals.
Arc length	The distance that the electricity must travel from the tip of the electrode to the weld puddle.
Arc welding	A fusion welding process that uses electricity to generate the heat needed to melt the base metals.
Atom	The smallest distinguishable unit of a material that maintains the same characteristics.
Autogenous weld	A welding process that does not require a filler metal. Sometimes the joint created by an autogenous weld cannot be detected.
Base metal	One of the two or more metals to be welded together to form a joint.
Bead	The end product of a joint that has been welded.
Circuit	A controlled path for electricity. During welding, the welder, work and electrode cables, electrode, and workpiece form a complete circuit.
Conductor	A material that allows for the flow of electricity. For a successful arc weld, electrodes and base metals must be good conductors.
Consumable electrode	An electrode that conducts electricity to the arc but also melts into the weld as a filler metal.
Copper	A reddish metal that is very ductile, thermally and electrically conductive, and corrosive resistant. Copper can be welded using limited methods.
Current	The flow of electricity, measured in amperes or amps. Arc welding requires a continuous flow of electricity to maintain the arc.
Electricity	The energy created by the movement of electrons. Electrical energy can be converted into light, heat, or motion.
Electrode	A device that conducts electricity. In welding, the electrode also can act as the filler metal.
Electrode cable	The path used in welding to conduct electricity from welder to the electrode. In welding, the cables are connected to the welder, the workpiece, and electrode, providing a closed electrical circuit.
Electrode holder	The insulated handle that clamps onto the electrode. The welder holds this during welding to control the arc.
Electron	A negatively charged particle that orbits the nucleus of an atom. Electrons flow between atoms in electrical conductivity.
Ferrous metal	A metal that contains iron. Ferrous metals are the most common type of welded metal.
Filler metal	A type of metal sometimes added to the joint in fusion welding. Filler metal adds to the strength and mass of the welded joint.
Flux	A non-metallic material used to protect the weld puddle and solid metal from atmospheric contamination.
Flux-cored arc welding	An arc welding process that uses a continuously fed consumable electrode that contains flux at its core. It is also referred to as FCAW.
Fusion welding	A welding process that melts the base metals at the joint. Upon cooling, the welded joint is often stronger than the base metals.
Gas metal arc welding	An arc welding process in which the bare wire electrode and inert shielding gas are fed to the weld through a welding gun. It is also referred to as GMAW or MIG welding.
Gas shielding	A layer of inert gas that protects the weld puddle and arc from atmospheric contamination.
Gas tungsten arc welding	A very precise arc welding process that uses a nonconsumable tungsten electrode. It is also referred to as GTAW or TIG welding.
Insulator	A material that inhibits the flow of electricity.
Joining	A process that brings materials together using either fasteners, adhesives, welding, or similar methods.
Joint	The meeting point of the two materials that are joined together. Welding creates a permanent joint.
Low-carbon steel	A steel that has a carbon range between 0.05 and 0.30 percent. Also referred to as mild steel, low-carbon steel is the most commonly welded metal.
Mechanical fastening	A process that joins two materials using a clamping force. Examples of mechanical fasteners include screws, bolts, and nails.
Melting point	The temperature at which a solid becomes a liquid. Welding requires metals to reach their melting points.
Metal	A hard, strong material that conducts electricity and heat, is shiny when polished, and can be bent and formed into shapes.
Molten	In a liquid state. Molten metals flow as a liquid.
Non-consumable electrode	An electrode that conducts electricity to the arc and does not become part of the finished weld.
Nonferrous metal	A metal that does not contain iron. Non-ferrous metals are more difficult to weld than ferrous metals.
Oxyfuel welding	A fusion welding process that uses a flame produced by gas containing oxygen and a gas fuel. Oxyfuel welding is also referred to as OFW.
Path	A conductor that directs electricity in a circuit. The path in welding and other applications is often copper wire.
Resistance	The opposition to current flow. Electricity flows in the path of least resistance.
Scratching	A method of striking the arc in which the welder guides the electrode across the workpiece at an angle. The scratching method closely resembles striking a match.
Shielded metal arc welding	An arc welding process that uses a flux-coated rod. It is also referred to in the shop as SMAW or stick welding.
Slag	Cooled flux that forms on top of the bead. Slag protects cooling metal and is then chipped off.
Spatter	Liquid metal droplets expelled from the welding process. Spatter can leave undesirable dots of metal on a workpiece surface.
Stainless steel	A steel that resists tarnishing. Stainless steel can be welded using many methods.
Tapping	A method of striking the arc in which the welder moves the electrode downward to the base metal in a vertical direction.
Tungsten	A gray metal that is very strong at elevated temperatures. Tungsten is used to make nonconsumable electrodes.
UV rays	Harmful rays emitted by the arc during welding. UV rays can damage a welder's vision and burn skin.
Vaporization	The process by which a liquid becomes a gas. Vaporization of a metal can ruin a weld.
Voltage	The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts
Volume	The amount of space that an object occupies. Solids and liquids have definite volume.
Weld puddle	The small area of molten metal that forms during welding. The cooled weld puddle forms the permanent joint. A weld puddle is also called a weld pool, molten pool, or molten puddle.
Welder	Either the person who performs a weld or the power source that provides the electricity needed to perform an arc weld. Printed materials may use both meanings of the term.
Welding	A joining process that uses heat, pressure, and/or chemicals to fuse two materials together permanently.
Work cable	The path used in welding to conduct electricity from welder to the workpiece. In welding, the cables are connected to the welder, the workpiece, and electrode, providing a closed electrical circuit.
Work clamp	The object that, along with the electrode, comes in direct contact with the workpiece during welding. The work clamp is connected to the work cable.
Work piece	A part that is being worked on. The workpiece may be subject to cutting, welding, forming or other operations.

Why is hydrogen a concern in welding?

Hydrogen contributes to delayed weld and/or heat affected zone cracking. Hydrogen combined with high residual stresses and crack-sensitive steel may result in cracking hours or days after the welding has been completed.
High strength steels, thick sections, and heavily restrained parts are more susceptible to hydrogen cracking. On these materials, we recommend using a low hydrogen process and consumable, and following proper preheat, interpass, and postheat procedures. Also, it is important to keep the weld joint free of oil, rust, paint, and moisture as they are sources of hydrogen

What electrode can I use to join mild steel to stainless steel?

Electrode selection is determined from the base metal chemistries and the percent weld admixture. The electrode should produce a weld deposit with a small amount of errite (3-5 FN) needed to prevent cracking.

What consumable should be used to weld cast iron?

Cast irons are alloys, which typically have over 2% carbon plus 1-3% silicon and are difficult to weld. Electrodes with a high percentage of nickel are commonly used to repair cast iron. Nickel is very ductile, making it a good choice to weld on cast iron, which is very brittle.

What is interpass temperature?

Interpass temperature refers to the temperature of the steel just prior to the depositing of an additional weld pass. It is identical to preheat, except that preheating is performed prior to any welding.
When a minimum interpass temperature is specified, welding should not be performed when the base plate is below this temperature. The steel must be heated back up before welding continues.
A maximum interpass temperature may be specified to prevent deterioration of the weld metal and heat affected zone properties. In this case, the steel must be below this temperature before welding continues.

What are the main benefits of using cold welding?

The process is quick, reliable and cost-effective. The weld cycle takes only seconds to complete and creates a permanent bond stronger than the parent material, without using heat, fillers or fluxes.

What kind of materials can be welded using cold pressure??

Cold welding can be used to join most non-ferrous wire and strip with diameters of between 0.07mm and 8mm copper and 14mm aluminium. Various aluminium alloys, brass, zinc, silver and silver alloys, nickel, gold and many other materials can also be welded using cold pressure welding.

What is welding cable?

A welding cable, sometimes referred to as a grounding cable, is a cable very finely stranded for flexibility. Most welding cables resist flame, grease, abrasion, tar, and oil and possess good color retention. A welding cable, however, is typically used because of its flexibility and versatility. separately..

What is the difference between AC and DC welding??

Both AC and AC/DC welders have a large transformer in them that converts the power from the wall outlet to a voltage that is proper for welding. AC welders simply convert the outlet AC voltage - DC welders convert the voltage AND change the AC from the wall outlet to DC. When the electricity is changed to DC, it has a polarity associated with it. AC (alternating current) power has no specific direction - it cycles back and forth 60 times a second (alternates). DC ( direct current) has a positive and a negative, just like a battery (all batteries are DC). When welding, some applications and welding rods require (or work best) with DC current.
AC/DC welders have both types of current available - they are the most versatile type of stick welders.