Roll Forming Handbook / Edited by George T. Halmos

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temperature,the materials involved in the sliding pair,and the various effects of ﬂuids and gases at the

interface.

The most commonly accepted theoryoffriction is based on the resulting adhesion between the

asperities of the contacting bodies. Te sts haveshown that regardless of how smooth the surfaces are, they

contact each other at only afraction of their apparent areaofcontact. Thus, the forming load is

supported with few asperities in contact; hence, the normal stress at the asperityjunctions is high. Under

light loads, the contact stresses may only be elastic. However,asthe load increases to some of the levels

involved in the roll forming process, elastic deformation of the asperities may take placeand the

junctions form an adhesive bond (microwelds).

Both the nature and strength of this bond depend on manyfactors. Among these are the mutual

solubilityand diffusion of the twosurfaces in contact, temperatureand time of contact, the nature and

thickness of oxide ﬁlms or contaminants present at the interface,and the presence of alubricant ﬁlm.

With clean nascent surfaces(such as those produced by cutting,orinforming operations in which

surface extensions are large) and in the absence of anycontaminants or lubricant ﬁlm, the strength of the

junctions is highbecause of cold pressurewelding. Consequently,the shear strength of the junction is

high, and hencefriction is high. As contaminants or lubricants are introduced,orasoxide layers develop

(which maytake only afew seconds in some cases), the strength of the junction is lowered because, under

these conditions, astrong bond cannot be formed. Thus, friction is lower.

Friction forceraises the temperature at the surface.The temperature increased with sliding speed,

coefﬁcient of friction, and decreasingthermal conductivityand speciﬁc heat of the materials. The higher

the thermal conductivity, the greater is the heat conduction into the bulk of the workpiece. In addition, the

higher the speciﬁc heat, the lowerthe temperaturerise is. Temperaturerise can be sufﬁciently hightomelt

the interfaceortocause phase transformations, residual stresses, and surface damage (metallurgical burn).

7.1.2 Wear

Wear is deﬁned as the loss or removal of material from asurface. Wear can take placeunder different

conditions. These maybedry or lubricated wear,sliding or rolling contact wear,and wear by fractureor

by plastic deformation.

There are four basic types of wear:adhesive, abrasive, fatigue, and corrosive wear.Generally,the ﬁrst

three types are of interest in metalworking operations, althoughthe last can also occur as aresult of tool,

die, and workpiece interactions in the presence of various liquids and gases. Particularly in this case,

appropriate choicesinlubrication chemistrymust be made, depending upon the tool and die

compositions; otherwise, excessivecorrosive tool wear takesplace.

7.1.2.1 Adhesive Wear

This type of wear is aresult of the junctions sheared during sliding.Ifthe junctions have strong bonds

(such as with clean interfaces, under highloads, and with sufﬁcient time to contact between the two

bodies), then fractureofthe junction takesplace either above or belowthe interface of the asperities.

Generally,itisthrough the softer metal that wrack forms and propagates. Under repeated cycling, the

transferredparticle becomes aloose wear particle. In severe cases of adhesive wear,the process is called

galling,scufﬁng,orseizure.

Foradhesive wear to occur,theremust be an afﬁnity(reactivity)for adhesion and welding between the

two sliding surfaces. The most severe case of wear occurs between twoclean surfaces, under highnormal

load and in vacuum. The basic roleofaneffectivelubricant is to reducethe tendency for welding of the

asperities, either by separating the surfaceswith alayer of lubricant or by reducing the shear strength of

the interfacebyforming low shear strength compounds through chemical reactions.

Surface ﬁlms are of great importanceinadhesive wear.Other than the lubricant layer,the surfacesare

almost always covered with oxide layers, contaminants, and adsorbed gases or ﬂuids. These ﬁlms

signiﬁcantly reduce the shear strength of the interface.Thus, the wear observed in practiceisgenerally

lower that it would have been otherwise. Oxide ﬁlms haveasigniﬁcant role in friction and wear.The effect

Roll Forming Handbook7 -2

depends on the relativerate at which oxide layers are destroyed during sliding and the rate at which they

form. If the rate of destruction is high, then the surfacesare not as well protected and wear is high.

7.1.2.2 Abrasive Wear

In this wear process, material is removedfromthe surfacebyscratching and producing slivers and

microchips. Thus, the softer the material, the higher is the abrasivewear rate. Also,the higher the load,

the higher the wear rate is.

Abrasive wear may be of the two- and three-body type. In the latter,the third body is composed of

wear particles or anyother hardcontaminants (such as those built up in alubricant) that are trapped

between the twosliding bodies. This mechanism may also be referred to as erosive wear.This type of wear

is importantinmetalworking processes and in the maintenanceofequipment. To reduce the buildup of

oxides, metal chips, or other metallic particles, periodic inspection, ﬁltering,orchanging the lubricants is

good practice.

7.1.2.3 Fatigue Wear

This type of wear is generally called surface fatigue or surface fracturewear.Itisaconsequence of cyclic

loading of an interface between the tool or die and the workpiece. Cracks developonthe surface over a

period of time by afatigue mechanism, resulting either from mechanical forces or from thermal stresses

(thermal fatigue). In either case, material is removed from asurface(usually the tool or die) by spalling or

pitting,whereby cracks coalesce by joining each other below the surface.

The role of lubrication in fatigue wear is complex. Lubricants reduce friction and hencereduce the

levelofstresses that could cause fatigue failure. On the other hand, if acrack develops because of some

mechanism or cause, the ﬂuid penetrates the crack by surface tension. During subsequent loading cycles,

the ﬂuid is trapped and, because it is incompressible, highhydrostatic pressureinthe crack opening

develops. This, in turn, propagates the crack farther into the body of the tool or die. Pitting,for example,

does not occur in unlubricated interfaces unless chemical attack takes place.

7.1.3 Lubricating Mechanisms

It is apparent from the foregoing discussions that friction and wear can be reduced or eliminated by

keeping the sliding surfacesapartfromeach other.Whereas in machine elements, such as lubricated

journal bearings and air bearings, this requirement maybefulﬁlled easily,the loads and speeds involved

in metalworking and the geometryofthe tool, die, and workpiece interfacesare generally such that they

do not readily permit the existence of alubricant ﬁlm. In this section, the major lubricating mechanisms

of interest to metalworking processes are described.

Lubricants are also applied as coolants to dissipate the heat generated by friction or forming. It is also

used to ﬂush away particles such as iron oxide and slivers. However,the primaryfunction of the applied

ﬂuid is lubricating, therefore, the term “coolant” is not used in this text.

7.1.3.1 Thick-Film (Hydrodynamic) Lubrication

In this areaoflubrication (also called full-ﬂuid ﬁlm), the twosurfaces are completely separated from each

other by acontinuous ﬂuid ﬁlm. The thickness of this ﬁlm is about 10 times the magnitude of the surface

roughness of the mating surfaces. The ﬂuid ﬁlm can be developed either hydrostatically (by entrapping

the lubricant) or,moregenerally,bythe wedge effect of the sliding surfaces in the presence of aviscous

ﬂuid at the interface. Thus, in this type of lubrication, the bulk properties of the lubricant (especially

viscosity)are important; chemical effects of the lubricant on metal surfaces are not signiﬁcant.

In thick-ﬁlm lubrication, the loads are usually light and the speeds are high. The coefﬁcient of friction

is very low,generally between 0.001 and 0.02. There is no wear,except from anyforeign matter (third

body) that mayhaveentered the lubricating system. This type of lubrication does not generally occur in

metalworking processes,exceptinisolated regions at die-workpiece interfaces with highviscosity

lubricants and at highoperating speeds.

Lubrication 7 -3

7.1.3.2 Mixed Lubrication

The ﬁlm thickness in thick-ﬁlm lubrication can be reduced by decreasing the viscosity (such as owing to

temperature rise), decreasingthe sliding speed, or increasing the load. The surfaces become close to each

other and the normal load between the tool or die, and the workpieceissupported partly by the ﬂuid ﬁlm

in hydrodynamic pockets in the surface roughness of the interfacesand partly by metal-to-metal contact

of the surfaces. This is generally referred to as mixed lubrication and also as the thin ﬁlm or

quasihydrodynamic regime.

The ﬁlm thickness is less than three times the surface roughness; the coefﬁcient of friction may be as

highasabout 0.4 (thus, forces and powerconsumption may increase substantially), and wear can be

signiﬁcant. There is an optimum roughness for effective lubricant entrapment, with arecommended

roughness of usually 15

.The hydrodynamic pockets also serve as reservoirs for supplying lubricant to

those regions at the interfacethat are starvedfor lubricants.

7.1.3.3 BoundaryLubrication

In this type of lubrication, athin layer of lubricant ﬁlm physically adheres to the surfacesbymolecular

forces, such as van der Waals forces, or by chemical forces (chemisorption). Typical boundarylubricants

are oils, fattyoils, fatty acids, and soaps. Boundaryﬁlms can form rapidly on clean surfaces, although

reactivityonsome metals such as titanium and stainless steel is very low;lubrication may then be

enhancedbythe formation of boundaryﬁlms on tool and die surfacesinstead of on the surfaceofthe

workpiece.

An important distinction is that, unlikeinfull-ﬂuid ﬁlm lubrication, wherethe bulk properties of the

lubricant (such as viscosity)are important, in boundarylubrication, the chemical aspects of the lubricant

and its reactivitywith metal surfaces are important; viscosity has asecondaryrole.Inthe boundary

lubrication area, the coefﬁcient of friction usually ranges from 0.1 and 0.4, depending on the strength and

thickness of the boundaryﬁlm. Boundarylubrication is often observedand practiced in metalworking

operations.

Wear rate in this regime depends on the rate at which ﬁlms are destroyed by rubbing off, or by

desorption owing to excessive temperature generated during the metalworking process. If the protective

boundarylayer is destroyed, then friction and wear will be high. The adherenceand strength of this ﬁlm

is thereforeaveryimportant factor in the effectiveness of boundarylubrication. The role of pressure,

speed, and viscosity on ﬁlm thickness should also be recognized.

7.1.3.4 Extreme Pressure Lubrication

In this sector of lubrication, the surfaceofthe metal is activated chemically by irreversible chemical

reactions. These reactions, involving sulfur,chloride, and phosphorus in the metalworking ﬂuid, form

salts on the mating metal surfaces. These surfacespreventorreduce welding of the asperities at the

interface even under highdie-workpiece contact pressure,hence the term “extreme pressure” (EP).

Furthermore, because of their low shear strength, these surfaceﬁlms also reduce friction.

As temperature increases, however,these ﬁlms may break down, the temperature for breakdown

depending on the particular EP additive (used either singly or in combination, such as both sulfur and

chlorine) and the composition of the metal surfaces. When the ﬁlm breaks down,metal-to-metal contact

takes place, with asubsequent increase in friction and wear.However,the protectiveﬁlms of sulfates and

chlorides form again with relativeease, especially on clean new surfaces. Air,oxygen, humidity, and water

also haveimportant effects on extreme pressure lubrication.

7.1.3.5 Elastohydrodynamic and Plastohydrodynamic Lubrication

We havenot yetconsidered the deﬂections and distortionsthe tools and dies mayundergo as aresult of

to the stresses encountered in metalworking operations. It has been shown that owing to the ﬁnite

modulus of elasticityofmaterials, these deﬂections can be sufﬁciently extensive to alter the geometryof

the die-workpiece interface, thus affecting the stresses, contact areas and geometry, and pressure

distribution. Hence, the term “elastohydrodynamic” (EHD). Another factor is the increase in viscosity

Roll Forming Handbook7 -4

(and even solidiﬁcation) of lubricants with pressure.This, in turn, helps develop hydrodynamic ﬁlms,

resulting in an increase in ﬁlm thickness.

An extension of EHD is plastohydrodynamic (PHD) lubrication. In this regime, encountered in

such processes as drawing and strip rolling, the lubricant is entrained or entrapped at the converging gaps in

the die-workpiece interfaces. Thus, afull-ﬂuid ﬁlm is developed with alarge drop in friction and wear.

These phenomena are particularly important in processes in drawingand in concentrated contacts

such as cold rolling of thin strip,because of the inﬂuence of small changes in the relativeinterfacial

dimensions on forces and deformation geometry.

7.1.4 Role of Surface Tension and Wetting

In addition to the lubricant viscosity and its chemical properties in reaction to the workpiece and die

materials, the surface tension and wetting also play an importantrole in lubrication. Wetting is a

phenomenon related to surface tension, which is amanifestation of surfaceenergy.

Wetting characteristics of alubricant —that is, how well the lubricant spreads itself over the surface of

the workpiece as acontinuous ﬁlm —isanimportantaspect of lubrication. There maybesituations,

however,inwhich it is desirable for the lubricant to remain in acertain area of the tool-workpiece

interface. Watch manufacturers, for example, haverecognized the need for nonmigrating (nonwetting)

lubricants for pivot point in awatch.

The shape of adrop of ﬂuid (such as metalworking lubricant) on asolid metal surface depends on the

interfacial tensions between the metal, ﬂuid, and air.The angle that the peripheryofthe droplet makes

with the surfaceiscalled the contact angle. The smaller this angle is, the better the wetting characteristics

of the ﬂuid.

Wetting in metalworking ﬂuids is improved by the addition of wetting agents, such as alcohols and

glycols, or by increasing the temperature. It is also found that wetting is improved by increasing the

surface roughness.

It can be seen from the foregoing discussion that lubrication in metalworking involves different

mechanisms, depending upon the chemistryofthe tool-lubricant-workpieceinterface, the method of

lubricant application, and the geometryofthe process, as well as the mechanics of the operation.

Furthermore,the lubrication mode often varies during the metalworking cycle, depending upon the

changes in the speed of the process as well as the amount of deformation and attendant pressures and

stresses involved.

7.2 Selection of Lubricants

There are ﬁve different categories of families of roll forming lubricants being used today in performing

operations in roll forming on the various surfaces and materials. The lubricant chosen must provide

good productivityand also meet the environmental restrictionsimposed on plant operations by the local,

state, and federal agencies.

The different types of roll forming lubricants, including their reactive physical and chemical properties

for each categoryare listed below and summarized in Table 7.1:

1. Evaporative compounds

2. Chemical solutions (synthetics)

3. Microemulsions (semisynthetics)

4. Macroemulsions (solubles)

5. Petroleum-based lubricants

7.2.1 Evaporative Compounds

Evaporative lubricants or vanishing oils are widely used rollforming lubricants. This group is quite

ﬂexible in its physical properties. The wetting capabilities can be adjusted or modiﬁed to suit the

Lubrication 7 -5

severity of the roll forming operation. The drying rate of the lubricant can also be controlled

(depending on the evaporative carrier). On heavy-dutyevaporative applications, the extreme pressure

additivescan be added to provide additional protection to both tooling and piecepart. Evaporative

lubricants are generally not cleaned from the piece partand usually requirenodegreasing.Evaporative

lubricants can be easily applied by using the roller coater method. They can also be applied by using

the proper type of airless spray system. Evaporative compounds, however,should not be recirculated.

This family of lubricants is ideal for painted, coated, vinyl, and galvanized surfaces as well as

nonferrousand ferrous materials.

Special formulations of evaporativelubricants can be used to provide for long-term rust protectionon

appliances,furniture, and automotive components. In manyinstances, the same specialized roll forming

lubricant can be used not only to producethe part, but also to provide long-term rust protection from

the applied lubricating ﬁlm.

7.2.2 Chemical Solutions (Synthetics)

Chemical solutions (synthetics) are one of the fastest growing roll forming lubricant family.They are

economical, environmentally safe, easy to handle, and are ideal for use on coated, galvanized, cold roll

steel, aluminum, and in some instances, stainless steel.

Chemical solutions allow for easy welding without prior cleaning and can be used for other secondary

operations such as punching,cutoff, and even drilling and tapping.

Chemical solutions are homogeneous mixtures, which are formed when solid, liquid, and gas are

completely dissolved in aliquid called the solvent. These solutions (also called “synthetic ﬂuids” or

“chemical ﬂuids”)donot contain oil,onlywater-solublecorrosioninhibitors,wetting

agents, lubricants (complex esters), biocides (fungicides), defoamers, and sometimes extreme pressure

agents.

TABLE 7.1 Comparison of Roll Forming Lubricants (Courtesy of TowerOil &Technology Co.)

Function Evaporative

Compounds

Chemical Solutions

(Synthetic)

Microemulsions

(Semisynthetic)

Macroemulsions

(Emulsion)

Oil-Based

(Solutions)

Reduce friction between tool and

workpiece

33 32 1

Reduce heat caused by plastic

deformationtransferring

to the tool

11 22 5

Reduce wear and galling between

tool and workpiecedue

to chemical surfaceactivity

41 22 4

Flushing action to prevent buildup

of dirt on tooling

11 23 4

Minimize subsequent processing

costs welding and painting

11 24 5

Provide lubrication at high

pressure boundaryconditions

43 32 1

Provide acushion between the

workpieceand tool to reduce

adhesion and pick-up

44 32 1

Nonstainingcharacteristicsto

protect surfaceﬁnish

11 23 5

Minimize environmental problems

with air contamination and

disposal problems

41 23 5

Note:1,Most effective; 5, Least effective.

Roll Forming Handbook7 -6

There are several different types of chemical solutions available. There are soap-typesolutions for

heavy-dutyroll forming. Extreme pressure-typesolutions are used for highstrength alloys and the

nonionic types are excellent for roll forming aluminum and coatedcomponents.

Chemical solutions can be applied by roller coater,sprayed, or used in properly designed recirculating

systems.

7.2.3 Microemulsions (Semisynthetics)

Sometimes, aroll formingoperationrequiresalubricant that provides excellent ﬂushing,cooling,and

improved lubricating qualities. Microemulsions areideal foruse on galvanized, hotrolled,coldrolled, and

stainlesssteel.Microemulsions providesomeﬁlm strengthfromthe combinationofemulsiﬁers,water-soluble

corrosioninhibitors, wetting agents, organic andinorganic salts,and sometimesextremepressure agents.

Microemulsions are emulsions in which the dispersed particles are in the range of 0.01 to 0.06

These emulsions are usually translucent or transparentinappearance. Their small particle size provides

excellent penetration and cooling for various types of roll forming.

Microemulsions can be sprayed,roller coated or used in aﬂood-typecoolant system.

7.2.4 Macroemulsions

Macroemulsions (sometimes misleadingly called “soluble oils”) contain an oil-based lubricant, such as a

mineral or compounded oil in the form of suspended droplets, which have been dispersed with the aid of

special chemical agents called emulsiﬁers. The emulsiﬁed oil droplets are large enoughtomake the made-

up lubricant milky (or sometimes translucent) in appearance. The action of emulsions as lubricants can

be close to that of the dispersed phase. Emulsions can also be formulated to include higher levels of

extreme pressure agents or barrier ﬁlms (polymers, fats, etc.) for heavy-dutyoperations. They are

generally milky white in appearance. Macroemulsions are generally used in heavy-dutyrollforming of

structural members, shelving,automotive,and furniturecomponents.

7.2.5 Petroleum-Based Roll Forming Lubricants

This family of forming lubricants provides manufacturing with widest range of choicesofvarious

lubricant properties both chemical and physical in nature.

The primaryvehicle in the make-up of most petroleum-based forming lubricants is the blending oil

(which can be of varying viscosities). Additional physical properties such as fats, polymers, and wetting

agents can also be added. If necessary, chemical extreme pressure agents such as sulfur,chlorine, and

phosphorous can be added to the formulation.

In special cases, added rust prevention can be provided and cleaning inducers can be included to

provide for easier cleaning.

Petroleum-based lubricants will continue to be used in rollforming on aselectivebasis. Cosmetic-type

pieceparts of stainless steel and some heavy-dutyformed sections may requirepetroleum-based

lubricants.

7.2.6 Additives

Properties of lubricants are adjusted and made suitable for speciﬁc applications by additives. Additives

can improvelubricating properties, protect metal surfaces, as well as perform manyother functions.

Rust or corrosion inhibitors are usually nitrates or phosphates. Extreme pressureadditives are

sulfur,chlorine, or phosphorus compounds. EP additives reduce the cold welding of metals under

pressure and prevent metal “buildup”but mayreduce lubricating properties. Additives, such as esters,

animal fats and fattyacids are added to oils to reduce surface tension or make it spread better.The

synthetic-typelubricants are modiﬁed with phosphorus compounds or other chemicals, to act as

Lubrication 7 -7

detergents. The reduced surface tension allows the lubricant to reachthe contact areamoreevenly and

quickly.

7.3 Surface Proper ties of Formed Material

7.3.1 Steel

When forming and lubricating the manytypes of cold rolled steel, there are two factors that haveadirect

bearing on the choice of lubricant; they are mill oil and foreign particulate such as scale, oxide, and rust.

Forexample, the presence of mill oil will interfere with the optimum adherence of evaporative

compounds, chemical solutions, or water-soluble systems. Another factor is that mill oil is asourceof

generated waste that should be controlled and minimized. Sometimes, the best answer is to use a

chemical solution (synthetic), which will reject the mill oil in aproperly designed clariﬁcation system.

The other alternativesare to use apetroleum-based lubricant over the mill oil or orderthe material dry.

Another contaminant to contend with on all materials (cold rolled, hot rolled, galvanized, aluminum,

and even stainless) is the presence of scale and oxide generated from these surfaces during the forming

process. The metal ﬁnes not only interfere with the rolls and piecepartappearance,but are asource of

hazardous waste that has to be controlled by removal beforeentryinto the rollformer (by brushing,

spraying,and prior cleaning).

It is important that under the aboveconditions the lubricant chosen has the physical capabilitytoﬂush

the metal particles from both the roll and piecepartsurfaces. The accumulation of metal particles can be

controlled with aproperly designed central reservoir (see Section 7.5).

When ﬂushing and penetration are required on either cold rolled, hot rolled and aluminized surfaces,

chemical solutions (synthetics) or microemulsions (semisynthetics) are the best choice in ordertoobtain

clean roll formed components (see also Table 7.2).

TABLE 7.2 Roll Forming Lubrication Guide

Material Being FormedEvaporative

Compounds

Chemical Solutions

(Synthetics)

Microemulsions

(Semisynthetics)

Macroemulsions

(Water Solubles)

Petroleum-Based

Lubricants

Electrogalvanized

and hot dip galvanized

XX XXX

Cold roll steel XX XXX

Hot roll steel XX XXX

High strength alloysteel XX XXX

Stainless steel XX XXX

Aluminum XX XXX

Paint or lacquer XX XN/A N/A

Vinylcoated XX XN/A N/A

Lubrication rating 11 123

Type of protection

corrosion (indoor)

N/A 2221

Method of application

Spray

Roll coatXXXXX

Drip XX XXX

Flood XX XXX

Method of cleaning

Alkaline N/A XXXX

Solvent N/A N/A N/A N/A X

Notes:“X” is suggested usage, application and cleaning methods. Ratings: 1, Excellent; 2, Ve ry good; 3, Good; 4, Fair;

5, Poor;N/A, Notapplicable.

Roll Forming Handbook7 -8

7.3.2 Galvanized Steel

There are various forms of galvanized coated materials available for the roll former to fabricate. Apartial

list would include hot dip,electrogalvanized, galvalum, galvaneal, and zincrometal. One common role in

lubrication for galvanized materials is to ﬂush the generated metal ﬁnes with the proper choice of

application technique and lubricant.

Light lubricants with excellent wetting are preferred to prevent roll buildup and provide clean parts.

Generally,evaporative, chemical solutions, and microemulsions perform this task well on electro-

galvanized, galvalum, and galvanneal surfaces. However,galvanized material, hot dip,orelectro-

galvanized should be closely checked, especially when achemical solution or water-soluble lubricant is to

be used. The water source ﬁrst must be analyzed to see if it will provide good coolant integrityand

stability—the actual componentsofthe lubricant to be used should be looked at on achemical and

physical basis. Another added safeguardistoperform humiditycabinet tests to screen out lubricants,

which fall shortinrust protection. Manytimes in spite of all the precautions and safetychecks, “white

rust” maystill occur (see Section 7.7.7).

7.3.3 Nonmetallic Coated Metals

Each type of coatingsuch as vinyl, mylar,and paint has its own special surface properties. It is imperative

that lubricant properties be checked in relation to each type of coating to preventsuch occurrences as

blush marks, peeling,and blistering.Evaporative lubricants and chemical solutions are ideal for use on

most coated surfaces.

7.3.4 Stainless Steel

Stainless steel is harder to lubricate than cold rolled because of its tight surface integrity(lower porosity)

and higher tensile strength. Higher energylevels are needed to form it, along with its spring-back

properties, which makeitacandidate for pressure-resistant lubricants that will not wipe offduring roll

forming.

Lubricants that perform well on stainless must haveexcellent wetting and polarityalong with

some extreme pressure protection to resist wipe off. Heavy-duty evaporative compounds, “EP”-type

chemical solutions and heavy-dutysolubles perform well on 200, 300, and 400 series stainless steel.

“Static tests”should be made with yourchosen lubricant to see if youindeed haveenoughwetting and

adherence.

7.3.5 Aluminum

When roll forming aluminum, the selection of the newer chemical solutions can be awise choice.These

new extra clean solubles are low in viscosity and haveunusually good penetration and polaritytokeepthe

metal ﬁnes from packing and adhering to tool surfaces. They also help to keep the aluminum well

lubricated and clean in appearance. Evaporating compounds are also being used successfully for roll

forming aluminum. Microemulsions (semisynthetics) can also provide the necessaryﬂushing and

penetration needed for roll forming aluminum.

Foreign metal particles, such as steel, copper,bronze, left on the surface of or embedded in the

aluminum will cause corrosion. Therefore, it is recommended that recirculatedlubricant, which has been

previously used in roll forming other metals, is not used.

7.3.6 Copper,Bronze, and Brass

Several water-soluble synthetic or occasionally water-soluble oil lubricants used to rollform aluminum

are applicable for copper based metals. High penetrating,highwetting,properties are preferred.

Lubrication 7 -9

7.4 Lubricants for the SecondaryOperations

More and moreroll forming lines are integrated with other in-line operations such as prenotching,

cutoffs, and postnotching.

7.4.1 Pre- or Postnotching and Punching

It is not uncommon to use the same lubricant for the prenotching operations that is being used in roll

forming.This can often lead to difﬁculties, because the prenotching can be, and often is, amoresevere

operation than roll forming.The shortened tool life in this operation can slow down an entirehi-speed

roll forming line. Generally,itismuch better to look at the prenotching as aseparate metal forming

operation and choose alubricant accordingly.Water-soluble materials in heavier concentrations can be

quite satisfactoryinperforming this function.

7.4.2 Cutoff

Another area in secondaryoperations is the cutoffdie. In most slug types of double shear blade cutoff

dies, it is advisable to look at the speciﬁc operation and choose the lubricant to meet this need. Heavy-

duty, superwet, soluble compounds are excellent for blade cutoffdies, and they are also used in heavier

strengths than for normal rollforming operations.

The tooling material used for cutoffblades are generally D-2, M-2, and CPM 10 V. The spray method

of applying cutoffisstrongly recommended, because it provides apositivelubricating ﬁlm on an

automatic basis and is safe and economical.

On single shear or crop-offdies, the tool life problem is generally not as severe as with the blade cutoff

dies. However,itisadvisable to grease the blade guides withanEP-type moly grease about once per week

or moreoften if it becomes necessary.

7.4.3 Other Postforming Operations and End Use

Operations following rollforming and ﬁnal application in assembly or erection can inﬂuence or restrict

the type of lubricant used. This point will be illustrated by afew examples:

1. Painting after forming requires either adry surface (i.e., evaporating lubricants) or compatible

solvents. It is usually recommended to abstain from silicon type lubricants.

2. Water-soluble lubricants, adhering to the surface of the product (especially if trapped by nesting

conﬁguration and stored for prolonged periods), can cause corrosion, rusting on “black”steel,

white rust on galvanized steel, and staining on aluminum.

3. Lubricants trapped in beads or groovescan create explosion hazards if products are to be hot-dip

galvanized after forming. Flash point and ﬂame spreading of lubricants should be checked when

products are welded or heated after forming.

4. Oiled slipperyroof sheets, installed at slope, and similar applications can create safetyhazards

during erection.

5. Drying oil or tacky lubricant, acting as an adhesive, can makeseparation of nested product

difﬁcult.

6. Lubricants applied for products subsequently used in direct contact with foodstuffsuch as grain

bins, food containers, and so on, must be free of harmful materials and usually must havehealth

authorityapproval.

7. Oily,nonevaporating lubricants on ofﬁce partitions, door frames, and similar products may stain

carpets and ﬂoors.

8. In line- or postforming,piercing adhesivebonding,foaming,orwelding mayrequire special

lubricant.

Roll Forming Handbook7 -10

7.5 Application Techniques

In roll forming,there are generally four different methods used in applying lubricant. They are drip,roller

coater, recirculating systems, and airless spray.The merits of each are nowconsidered in turn.

7.5.1 Drip

Chemical solutions, soluble oils, and evaporating compounds can be applied by using adrip lubricator in

conjunction with some type of wiper consisting of afelt pad, open cell foam, rug material, or packing.

Drip lubricators by themselves are not positive enoughtoprovide an adequate and continuous ﬁlm of

lubricant. It should be noted that containers feeding the drip lubricator should be large enoughto

contain at least an hour’ssupply of lubricant. Lubricant may be applied to the strip or to the top and

bottom rolls.

7.5.2 Roller Coat

The roller coatermethod of applying lubricant is gaining in popularity. This technique consists of asmall

movable tank and pumping unit, which feed awiping head or roller with lubricant. The thickness and the

amount of lubricant can be regulated, and the excess ﬂows back to the reservoir.When lubricating

precoated or polished materials with aroller coater, it mightbeadvisable to use polyurethane or

neoprene rolls to makesure the working surfacesare not scratched or marked. Steel rolls can sometimes

cause problems on coated surfaces.

In manyinstances, roller coaters by themselvesmay not produce enoughlubrication ﬁlm to ﬂush out

particles generated by aluminum, galvanized, and hot roll. Sometimes, asprayer installed in the critical

forming areas wherebuildup maybeoccurring can ﬂush out unnecessaryparticles.

Another problem that can occur when applying lubricant (especially on wide stock) is aresult of

material that has a“crown”condition. Here, the roller mayonly lubricate the highspots, leaving the

outside edges without lubricant. Asimilar problemmay occur on wavy stock. Asoft roller can help in

adjusting itself to this crown or wavy condition.

7.5.3 Recirculating Systems

7.5.3.1 Purpose of Recirculating

When roll forming heavy gauge and cold rolled and hot rolled steel (especially with scale), the

recirculating system of applying lubricant is usually the best approach. Here, sufﬁcient amounts of

lubricant not only havetoprotect the rolls, but the scale and metal ﬁnes that are generated by the roll

forming process are ﬂushed offthe tooling and into the reservoir.Itthen follows that the use of bafﬂes,

settling tanks and ﬁlters help collect large quantities of contaminants and metal ﬁnes, helping keep the

coolant relatively clean. Magnets can be extremely helpful in keeping the amount of metal being

recirculated down to aminimum.

7.5.3.2 Lubricant Tank Design

The function of the closed loop lubricant reservoir is to clarify and remove the foreign materials and

process contaminants being generated by the roll forming operation.

The capacityofthe tank should be 5to10times the pump capacityofthe recirculating pump (e.g.,

asystem with a10gallon per minute pump should have a50to100 gallon tank). This capacityallows

time for foreign particles to settle out and for oils and greases to be removed by skimming,and so on. It is

essential that the reservoir contains two bafﬂes, askimmer,and some form of ﬁltration such as abag ﬁlter

along with magnets to remove metal particles.

Lubrication 7 -11