1st Year Apprenticeship1st Year Apprenticeship

Metal WorkMetal WorkIn this block you will learn

about:• Metals and their properties• Deformation effects after impact• Tools used for effective repair• Stretching and shrinking• Paintless dent removal

Body SteelsBody Steels• Hot rolled

– thickness ranges 2-8 mm

– generally used for full frames, sub frames (unibody) and crossmembers

• Cold rolled– hot rolled, acid

rinsed, cold rolled thin, then annealed

– better surface quality

– good workability– most unibody panels

are cold rolled steel– stamping process

increases strength

                                                                                                                                 

                                                            

Cold Rolling Mill to Cold Rolling Mill to StampingsStampings

Grain Structures of SteelGrain Structures of Steel

HSLAHSLA

Mild SteelMild Steel

Properties of SteelProperties of Steel

• Mild Steel • HSS • HSLA• UHSS• AHSS

up to 30,000 psi yield strength30 - 70,000 psi yield strength

75 - 100,000 psi yield strength100- 160,000 psi yield strength110 – 180,000 psi yield strength

HSSHSS• Gets its initial strength

during the heating/cooling treatment from the steel manufacturer

• Is used mainly for load bearing components in the body structure, however more commonplace today throughout entire body structure

• May be repaired cold or with controlled heat

• More difficult to repair than mild steel

• Yield strength of up to 70,000 psi.

• Lack of available identification for HSS means treat all steel as HSS!

HSLAHSLA• Like HSS except

varying alloying elements (chemicals) are added during the manufacturing process to increase its strength (yield and tensile)

• May be reworked cold or with controlled heat application

• Found in areas such as:– Door intrusion beams– Bumper

reinforcements– Lock pillars– Front and rear frame

rails– Hinge pillars (A,B,C)

• Yield strength up to 110,000 psi.

UHSS/AHSSUHSS/AHSS• The strongest of the

structural steels found in today's automobiles

• Often referred to as Boron, Martensitic, Dual phase steels

• Found in these areas:– Front and rear bumper

reinforcements– intrusion beams– A,B,C pillars (some

vehicles)

• No heat No heat whatsoever is to be whatsoever is to be applied to any applied to any component of this component of this designation!designation!

• These steels are generally not repairable

• Require special considerations when removing/sectioning

Identification of SteelsIdentification of Steels• Location and application of HSS steels vary

widely from manufacturer to manufacturer• Sources of information include:

– OEM body repair manuals– Internet sources (OEM approved)– Mitchell manuals (estimating manuals)

• If you cannot positively identify the If you cannot positively identify the makeup of a component, you must treat it makeup of a component, you must treat it as HSS!as HSS!

HSS Locations

Part LoadingPart Loading• Tension:

• a load that tries to pull parts straight apart• Compression

• a load that forces parts straight into one another• Shear

• A load that pulls sideways• Cleavage

• a load that pulls parts away from each other at an angle

• Peel• a load that pulls parts straight away from one another

Loads present during a Loads present during a collisioncollision

TerminologyTerminology• Yield strength:

– The minimum amount of force any piece of metal can resist without bending or deforming permanently

• Yield Point: – The amount of force that a piece of metal can resist without tearing or breaking

• Tensile strength– is measured as the maximum force per unit of

area that causes a complete fracture of break

TerminologyTerminology• Work Hardening

– Is the upper limit of plastic deformation, causing the metal to become hard in the bent area

• Malleability– is the property which allows deformation under

compression or upsetting (shrinking)• Elasticity

– is the ability of the metal to be bent or stretched and spring back to its original shape

TerminologyTerminology• Plasticity:

– The property that permits metal to change shape when sufficient force is applied to it

• Plastic Deformation: – The ability of the metal to be bent or formed

into different shapes ( bent beyond its elastic limit)

• Elastic Deformation: – The ability of the metal to be stretched or

bent and return to its original state

TerminologyTerminology• Torsional strength

• is the property of a material to withstand a twisting force

• Shear Strength• is a measure of how well a material can

withstand forces acting to cut or slice it apart

• Compressive Strength• is the property of a material to withstand

being crushed

Metal Strength Metal Strength TerminologyTerminology

Elastic DeformationPlastic Deformation

TerminologyTerminology• Rigidity:

– Opposite of plasticity. • example: Cast iron will not bend or deform, it will

only break under load

• Ductility:– ability of a metal to plastically deform

without breaking or fracturing, with the cohesion between the molecules remaining sufficient to hold them together

Heat and Sheet MetalHeat and Sheet Metal• The point at which Steel melts is 2600

Degrees F

• We should know the effects of the temperature change between 400 - 1600 degrees F.

• Three Effects:• scaling• changes in grain structure• expansion and contraction

Temperature and Colour Change

• Light film of scale (iron oxide) 430 FLight film of scale (iron oxide) 430 F

• Pale yellowPale yellow / / Straw Straw / / BrownBrown / / PurplePurple / / Light BlueLight Blue

• Dark Blue / 600 degrees FDark Blue / 600 degrees F

• Reddish Glow / 900 degrees F Reddish Glow / 900 degrees F

• Blood Red / Dark Cherry 1200 FBlood Red / Dark Cherry 1200 F

• Cherry Red 1550 degrees FCherry Red 1550 degrees F

• Critical Point 1600 degrees FCritical Point 1600 degrees F

Low Crown

High Crown

Reverse Crown

BucklesBuckles• Buckles occur when metal has been bent

past it’s elastic limit• Work hardening has occurred and a new

shape is formed• The buckles found in indirect damage are

as follows:– simple hinge– collapsed hinge– simple rolled– collapsed rolled

Direct and Indirect Direct and Indirect DamageDamage

Impact effect on a High Crown

Effect of damage on a Low Crown PanelEffect of damage on a Low Crown Panel

Effect of impact on a combination High / LowEffect of impact on a combination High / LowCrowned PanelCrowned Panel

Tension can only be removed by “unlocking” thepressure areas

Combination of BucklesCombination of Buckles

simple hinge buckle

two types of rolled buckles

Collapsed hinge buckle

Steps in Unlocking Steps in Unlocking DamageDamage

First in last outFirst in last out

“Collapsed Roll Buckle”

What happens to the Steel upon impact?

In this case, the damage (Hinged Buckle) hascaused severe damage to the molecular structure

Hammering helps the atoms to ‘vibrate’ backinto shape, or order

ToolsTools• Hammers• Dollies• Spoons• Dent pullers• Body picks• Oxy-Acetylene • Body files

Body HammersBody Hammers

Hammers

Holding the BodyHammer

DolliesDollies

Holding the Dolly

Using the Corner of the Dolly

Using the Edge of the Dolly

Using the Dolly asa tool for bumping

SpoonsSpoons

Uses of the Body SpoonUses of the Body Spoon

• Can be used as adolly in hard to reachareas

• When used withdue care, can be used for leverage

• Great tool for dispersing the force of a hammer blow

Body Picks

Body Puller Set(Slide Hammer)

Pull Rods

Other Body Working ToolsOther Body Working Tools• Pry Bars• Suction Cups• Stud Welders• Porta-spot Dent Pullers• Body Files• Slap Files• Hydraulic Porta-Power

Dent Removal ToolsDent Removal Tools

Dent Removal Dent Removal SystemsSystems

Hammer MaintenanceHammer Maintenance

Depending on thecondition of yourhammer, severalsteps may need tobe taken to restorethe ‘mirror’ finishto the surface on the face of the hammer.

From filing towet sanding andpolishing.

Locating DamageLocating Damage• Visually

• Physically

• Mechanically

Use your senseof sight and thereflection of a light source as ameans of damageidentification

If a visual referenceis not possible, feelingfor damage will bemore than satisfactory

Mechanical Methods

Hammer and Dolly

Variables:

• Force of hammer blow

• Force of Dolly rebound

• Shape of Dolly

• Working distance

Hammer on Dolly Hammer on Dolly

Hammer off Dolly

Metal FundamentalsMetal Fundamentals

• Properties of steel• Working the metal• Heat Shrinking

Detecting an ‘Oil Can’ or stretched area

Time to Shrink! Time to Shrink!

ShrinkingShrinkingShrinking Procedure Shrinking Procedure

- Hold torchat right angleto panel

- heat metal to desireddegree

- place dollybehind areato be shrunk

- hammer areafrom centre out- quenchimmediately withwet sponge

Cold ShrinkingCold Shrinking

Using a Carbon Rod for heat shrinking

Repair PlanRepair Plan• Determine the extent of

the damage • Removal of moulding,

emblems, or sound deadening materials from behind panels

• Roughing out dents with hammer, puller, or pry bar

• Metal finishing with hammer, dolly and body file

• Panel shrinking • Removal of small dents

and bulges • Filling with body filler • Filing, sanding, and

priming the fill area • Rustproofing the back

side of panels• Completion of repairs

End of Metal Repair FundamentalsEnd of Metal Repair Fundamentals