These process groups are shown by the Table, along with each process name and
letter designations. Each process group will be briefly described.
Solvent or rubber cements
Arc cutting (thermal)
Air carbon arc cutting
Carbon arc cutting
Gas tungsten arc cutting
Metal arc cutting
Plasma arc cutting
Oxygen cutting (thermal)
Chemical flux cutting
Metal powder cutting
Oxygen arc cutting
Oxy Fuel gas cutting
Oxygen lance cutting
Other thermal cutting processes
Electron beam cutting
Laser beam cutting
||Electric arc spraying
Adhesive bonding (AB)
is a joining process in which an adhesive is
placed between the faying surfaces which solidifies to produce an adhesive
bond. The adhesive bond is the attractive force, generally physical in
character, between an adhesive and the base materials.
The two principle interactions that contribute to the adhesion are the
van der Waals bond and the diepole bond. The van der Waals bond is defined
as a secondary bond arising from the fluctuating-diepole nature of an atom
with all occupied electron shells filled. The diepole bond is a pair of
equal and opposite forces that hold two atoms together and results from
a decrease in energy as two atoms are brought closer to one another.
Adhesive bonding of metal-to-metal applications accounts for less than 2%
of the total metal joining requirements. The bonding of metals to nonmetals,
especially plastics, is very important and is the major use of adhesive
Dextrins belong to the family of starch-derived adhesives ranging
in color from white to dark brown and are normally fluid filmy materials.
These are glues and pastes used to bond porous materials. They are spread
in a thin film.
Rubber cements or solvent cements are adhesives that contain organic
solvents rather than water. They are based on nitro cellulose or polyvinyl
acetate, normally elastomeric products, dispersed in solvent. They are free
flowing, thin set materials that dry to hard tack free films. They are used
in pressure-sensitive labeling operations and in contact bonding for the
Synthetic resins are composed of synthetic organic materials and
are relatively expensive. They are used when a high-quality bond is
required and they are relatively heat and moisture resistant. They can
be applied by automatic or semiautomatic equipment, are used for sealing
cartons and for wood, and for vinyl film laminations. One of the major
groups is the hot melts which are combinations of waxes and resins that
form a bond by applying heat and then cooling.
Epoxy Adhesives are the newest of the adhesives and can be used
to bond metal-to-metal, metal to plastics, and plastics to plastics. They
are a family of materials characterized by reactive epoxy chemical groups
on the ends of resin molecules. They consist of two components, a liquid
resin and the hardener to convert the liquid resins to solid. They may
contain other modifiers to produce specific properties for special
applications. Some epoxies will bond to concrete. One of the newer
advances is the oily metal epoxy that bonds directly to oily metals
"as received" with normal protective films on them. The oily coating need
not be removed. They achieve intimate molecular contact with the surface
to be bonded and will achieve high adhesion on almost any surface. Epoxies
are the most expensive of the adhesives; however, they offer more
These processes utilize heat and thus differ from mechanical cutting
processes such as sawing, shearing, blanking, etc.
The arc cutting processes are a group of thermal cutting processes which
melt the metals to be cut with the heat of an arc between an electrode
and the base metal. Within this group is air carbon arc cutting; carbon
arc cutting; gas tungsten arc cutting, shielded metal arc, gas metal arc,
and plasma arc cutting. Each will be briefly described.
The thermal cutting processes can be applied by means of manual,
semiautomatic, machine, or automatic methods in the same manner as the
arc welding processes.
Air Carbon Arc Cutting(AAC) is "an arc cutting process in which metals
to be cut are melted by the heat of a carbon arc and the molten metal
is removed by a blast of air."
Principle of operation is the following: a high velocity air jet
traveling parallel to the carbon electrode strikes the molten metal
puddle just behind the arc and blows the molten metal out of the
immediate area. It shows the arc between the carbon electrode and
the work and the air stream parallel to the electrode coming from
the special electrode holder.
The process is not recommended for weld preparation for stainless steel,
titanium, zirconium, and other similar metals without subsequent cleaning.
Carbon Arc Cutting (CAC) is "an arc cutting process in which metals are
severed by melting them with the heat of an arc between a carbon electrode
and the base metal."
The process is identical to air carbon arc cutting except that the air blast
is not employed. The process depends strictly upon the heat input of the
carbon arc to cause the metal to melt. The molten metal falls away by
gravity to produce the cut. The process is relatively slow, a very
ragged cut results and it is used only when other cutting equipment
is not available. It has little industrial significance.
Metal Arc Cutting (MAC) is "an arc cutting process which severs metals by
melting them with the heat of an arc between a metal electrode and the
base metal." When covered electrodes are used it is known as shielded
metal arc cutting (SMAC).
The equipment required is identical to that required for shielded metal
arc welding. When the heat input into the base metal exceeds the heat
losses the molten metal pool becomes large and unmanageable. If the
base metal is not too thick, the molten metal will fall away and create
a hole or cut. The cut produced by the shielded metal arc cutting process
is rough and is not normally used for preparing parts for welding. The
metal arc cutting process using covered electrodes is used only where
a small cutting job is required and other means are not available for
Gas Tungsten Arc Cutting (GTAC) is "an arc cutting process in which
metals are severed by melting them with an arc between a single tungsten
(nonconsumable) electrode and the work. Shielding is obtained from a gas
or gas mixture."
This process has largely been supplanted by plasma arc cutting and is of
little industrial significance except for the small jobs when other
equipment is not available.
Plasma Arc Cutting (PAC) is an arc cutting process which severs
metal by melting a localized area with a constricted arc and removing
the molten material with a high-velocity jet of hot ionized gas.
There are three major variations: (1) low-current plasma cutting which is
a rather recent development, (2) the original relatively high current
plasma cutting, and (3) plasma cutting with water added. The low-current
plasma variation is gaining in popularity because it can be manually
The principle operation of plasma cutting is almost identical with the
keyhole mode of plasma welding. The difference is that the cut is
maintained and the keyhole is not allowed to close as in the case
of welding. Heat input at the plasma arc is so high and the heat
losses cannot carry the heat away quickly enough so that the metal
is melted and a hole is formed. The plasma gas at a high velocity
helps cut through the metal.
The secondary gas can also assist the jet in removing molten metal and
limits the formation of drops at the cutting edge. Plasma cutting is
ideal for gouging and for piercing. For some operations air is used as
the plasma gas. A higher arc voltage is normally used for cutting than
The plasma arc cutting process can be used to cut metals underwater.
Oxygen Cutting (OC)
is a group of thermal cutting processes used
to sever or remove metals by means of the chemical reaction of oxygen
with the base metal at elevated temperatures. In the case of
oxidation-resistant metals the reaction is facilitated by the
use of a chemical flux or metal powder. Five basic processes
are involved: (1) oxy fuel gas cutting, (2) metal powder cutting,
(3) chemical flux cutting, (4) oxygen lance cutting, and (5) oxygen arc
cutting. Each of these processes is different and will be described.
Oxy Fuel Gas Cutting (OFC) is used to sever metals by means of the
chemical reaction of oxygen with the base metal at elevated temperatures.
The necessary temperature is maintained by means of gas flames obtained
from the combustion of a fuel gas and oxygen.
Metal Powder Cutting (POO) is an oxygen-cutting process which
severs metals through the use of powder, such as iron, to facilitate
cutting. This process is used for cutting cast iron, chrome nickel
stainless steels, and some high-alloy steels.
Chemical Flux Cutting (FOC) is an oxygen-cutting process in which
metals are severed using a chemical flux to facilitate cutting and powdered
chemicals are utilized in the same way as iron powder is used in the metal
powder cutting process. This process is sometimes called flux injection
Oxygen Lance Cutting (LOC) is an oxygen-cutting process used to
sever metals with oxygen supplied through a consumable tube. The preheat
is obtained by other means. This is sometimes called oxygen lancing. The
oxygen lance is a length of pipe or tubing used to carry oxygen to the
point of cutting.
Oxygen Arc Cutting (AOC) is an oxygen-cutting process used to
sever metals by means of the chemical reaction of oxygen with the base
metal at elevated temperatures. The necessary temperature is maintained
by means of an arc between a consumable tubular electrode and the base
Other thermal cutting processes
Electron Beam Cutting (EBC)
is a thermal cutting process which uses
the heat obtained from a concentrated beam composed of high-velocity
electrons which impinge upon the work piece to be cut. The difference
between electron beam welding and cutting is the heat input-to-heat
The electron beam generates heat in the base metal, which vaporizes the
metal and allows it to penetrate deeper until the depth of the penetration,
based on the power input, is achieved. In welding the electron beam actually
produces a hole, known as a keyhole. The metal flows around the keyhole
and fills in behind. In the case of cutting the heat input is increased
so that the keyhole is not closed.
Laser Beam Cutting (LBC) is a thermal cutting process which severs
materials with the heat obtained in the application of a concentrated
coherent light beam impinging on the workpiece to be cut. The process
can be used without an externally supplied gas.
Thermal spraying (THSP)
is a group of allied processes in which
finely divided metallic or nonmetallic materials are deposited in a
molten or semi-molten condition to form a coating. The coating material
may be in the form of powder, ceramic rod, or wire.
There are three separate processes within this group: electric arc
spraying, flame spraying, and plasma spraying. These three processes
differ considerably, since each uses a different source of heat. The
apparatus is different and their capabilities are different.
The selection of the spraying process depends on the properties desired
of the coating. Thermal spraying is utilized to provide surface coatings
of different characteristics, such as coatings to reduce abrasive wear,
cavitation, or erosion. The coating may be either hard or soft. It may
be used to provide high temperature protection. Thermal sprayed coatings
improve atmosphere and water corrosion resistance. One of the major uses
is to provide coatings resistance to salt water atmospheres. Another use
is to restore dimensions to worn parts.