Lubricants

The lubricant’s main duty is to diminish the influence of friction
between the tooling and the material. Ideally, lubricants should also act as a coolant and
thermal insulator, while not being causative of any detrimental action against the tooling or
the material, the press equipment or the operator. The lubricant should not cause rusting of
metal parts, and should be easily removable by some accessible means.
Lubricants are of utmost importance in forming and drawing processes, where these can
be divided into two categories, based on the type of lubricants used:
• Wet drawing or forming, using mineral oils, vegetable oils, fat, fatty acids, soap, and water
• Dry drawing or forming, using metallic coatings (Cu, Zn, brass) with graphite or emulsions,
Ca-Na stearate on lime, borax or oxalate, chlorinated wax or soap phosphate
In metal forming, the danger of entrapping the lubricant with the fast action of the tooling
presents additional possibilities of surface deformation. Usually, areas affected by a
restrained lubricant display a sudden roughness, often resembling a matte finish.
Lubricating Components. The actual process of lubrication is provided by several
basic ingredients. These are:
• Mineral oils, which are petroleum derivates, such as motor oil, transmission fluid, and
SAE-oils.
• Water-soluble oils, which are a combination of mineral oils, adjusted by an addition of
other elements to become emulsifiable with water.
• Fats and fatty oils, most often of vegetable or animal origin, such as lard, fish oil, tallow,
all vegetable oils, and beeswax.

Fatty acids, such as oleic and stearic acids, generated from fatty oils.
• Chlorinated oils, a combination of fatty oils and chlorine.
• Soaps, which are basically water-soluble portions of fatty acids, combined with the alkali
metals.
• Metallic soaps, which are insoluble in water, such as aluminum stearate and zinc stearate.
• Sulfurized oils, or hydrocarbons, treated with sulfur.
• Pigments, such as graphite, talc, or lead. These are actually minute particles of solids, not
soluble in water, fats, or oil. They are often supplied in a mixture of oils or fats, which
provide for their retention and spreading.
These ingredients when added into but three groups of compounds form a metal-forming
lubricant. These compounds are as follows:
• Base material, a carrier.
• Wetting or polarity agent.
• Parting agent, or an extreme-pressure agent.
For example, in drawing process, the carrier may be oil, solvent, water, or a combination
of several compounds. The wetting agent often consists of emulsifiers, animal fats or
fatty acids, or long chain polymers. The parting agent, where added, is chlorine, sulfur, or
phosphorus. Also added may be physical barriers, such as graphite, talc, and mica.
It is expected of a lubricant to be able to control friction, prevent galling, dissipate heat,
and reduce tool wear. The dissipation of heat depends on the function and properties of the
carrier. All the additional qualities and properties depend on the other ingredients and on
that particular lubricant’s mechanism.
According to the lubricating mechanism, there are three basic types that are being used:
1. Hydrodynamic lubrication, or fluid film lubrication. This type of lubrication works well
where the lubricating film is not disrupted by an increase in temperature or speed. It is
efficiently used for lubricating of auto engines, but unfortunately, in metal stamping and
metal forming it has not found an application yet.
2. Boundary lubrication occurs where the lubricant is combined with surfactants, also
called wetting agents or polar additives. These become attracted to the surface of metal
of the tooling and that of the sheet-metal material as well, acting as a protective layer of
these surfaces. Surfactants can be soaps, their base carrier being fat, oil, fatty alcohols,
and the like. This type of lubricant further benefits from its enhanced wetting capacities.
Of disadvantage are the temperature-related functionality limits, which top off with
100°C, or a boiling point of water.
3. EP lubricants can be chemical or mechanical. In chemical EP form, chlorinated hydrocarbons
are added to stamping lubricants, where they form protective metallic salts on the
surface of the part and its tooling. During the stamping process, the heat of the operation
forces the released chlorine to interact with iron and the resulting iron-chloride film
becomes the actual lubricant. Where sulfur is used in the lubricating base (i.e., carrier),
the chemical reaction produces an iron-sulfide film. Mechanical EP lubricants’ additives
are molybdenum disulfide and calcium carbonate. The disadvantage of this lubricant
type lies in the buildup it leaves on the part and on the tooling, which can affect some
sensitive portions of the tool and cause their breakage.
A fourth type of lubricating mechanism exists in the form of various combinations of
the above-described three methods.

Many materials used in the production of electronics are incompatible with the third, EP
method of lubrication. With bronze, beryllium copper, or phosphor bronze materials, their
surfaces do not respond well to these lubricants. Actually, where sulfur is being used, staining
of some alloys may occur. For this reason, a boundary method of lubrication using a
combination of chlorine and fatty materials is preferable.
According to their basic component, lubricants can be further divided into:
• Oil-based
• Water-based
• Solvent-based
• Synthetic
• Dry-film
Oil-based lubricants are useful for processes where high loads are present. These are
petroleum-based lubricants and their applications include punching, blanking, coining,
embossing, extruding, some demanding forming operations, and drawing.
Water-based lubricants may sometimes contain oils as well, with which they form
emulsions. These lubricants are easier to remove from the surface of parts than those based
on petroleum. Lately this type of lubricating approach is becoming quite popular, since the
performance of some heavy-duty types are on par with petroleum-based products. Waterbased
lubricants are well suited for progressive dies, transfer presses, and for drawing
operations.
Solvent-based lubricants are of importance where the basic sheet-metal material is
already coated, such as vinyl-coated materials, lacquered and painted surfaces, or laminates.
In some instances, these lubricants do not require any cleaning nor degreasing afterwards,
for which advantage they are preferred for manufacture of appliances, electrical
hardware, and similar components.
Synthetic lubricants are very easy to clean, as they usually consist of solutions of chemicals
in water. These can be used on coated surfaces, with vinyl-clad parts, painted parts, or
aluminum. Many synthetic lubricants are biodegradable and as such they do not possess
any environment-harming qualities.
Dry-film lubricants previously consisted of high melting point soaps. Some new types
that emerged on the market are synthetic esters and acrylic polymers. These produce good
results where applied to blanks or strips of sheet-metal material. Of a distinct advantage is
their cleanliness, ease of handling and performance. Unfortunately, their cost is not always
compatible with the requirements of the metal stamping industry, which is further complemented
by their inability to dissipate heat of the operation.
As a rule, with all lubricants, their use and methods of application must be compatible
with those they were developed for. Where a wrong lubricant should be used, the results of
such manufacturing operation may be pitiful. Therefore, the lubricant’s characteristics
must be fully understood and tried out prior to production, to make sure these will be used
only for processes they were intended for.