Cladding Metals:
New Processes for a Centuries-Old Technique
Todd W. Romance,
Posted
07/01/2008
The cladding of
metals is a centuries-old metalworking technique From its origin as
process for bonding decorative gold or silver surfaces on base
metals, the cladding process has been refined to the point where
today it is a sophisticated technology used in hundreds of
industrial applications.
A clad metal is
two or more distinct metals or alloys metallurgically bonded
together in layers. At Engineered Materials Solutions, Attleboro,
Mass., this bond is achieved by a refined process based on the
technology of solid-state welding. This bonding technique is so
effective there is no need for intermediate brazing alloys or
adhesives. It's simple, clean and permanent.
Virtually any
combination of ductile metals can be clad-with individual
components representing from 2 to 98 percent of the total composite
thickness. As a rule of thumb, composite properties, such as
tensile strength and conductivity, can be estimated as the
arithmetic sum of the volume percent of each component times its
specific property value. Dimensions of EMS manufactured clad metals
range from 0.00157 to 0.150 inch (0.039 to 3.8 mm) in thickness and
up to 25 inches (635 mm) in width.
Clad metals can be
made by several distinct processes. The principal method of
manufacture used by Engineered Materials Solutions is a continuous
roll bonding process in which two or more strips can be clad. Prior
to bonding, the individual strips are extensively cleaned to
provide contaminant-free surfaces. When passed through a specially
designed rolling mill, a composite material is formed deriving its
bond integrity from the creation of shared electrons between the
mating surfaces. Subsequent thermal treatment is then done to
induce diffusion, improve bond strength and provide stress relief
for further cold-working operations. It should be noted that after
bonding, the ratio of component materials remains constant
throughout all cold-work operations.
Once the clad
composite has been created, finishing operations are performed,
such as rolling to intermediate and final gauge, annealing to
temper, cleaning, buffing (if luster is critical), edge trimming
and slitting prior to final shipment.
The objective of cladding is to provide in a single material the
optimum combination of functional properties needed for a
particular product. Careful selection of component materials and
control of properties can result in significant improvements in
product performance and reductions in product costs. The key is to
approach clad metals from the perspective of combining the
desirable properties of different materials for the specific
product application.
Some typical
applications for clad metals are:
Architectural metals
Bearing materials
Bright truck bumpers
Button cell battery cans
Cable shielding
CATV wire
Catalytic converter substrate
Coinage
Heat exchangers
Self-brazing materials
Cookware
Thermostat bimetal (thermal actuators, motor
protectors, fluorescent light ballasts, etc.)
Transition material
Todd W. Romance is vice president of sales and marketing and new
product development for Engineered Materials Solutions, Attleboro,
Mass. He has spent most of his career in the specialty chemicals
and metals markets. Prior to joining EMS, Romance was vice
president and general manager of the Cobalt Division of OMG in
Cleveland.