1st Year Apprenticeship

Metal Work

In 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 Steels

Hot rolledthickness ranges 2-8 mmgenerally used for full frames, sub frames (unibody) and crossmembersCold rolledhot rolled, acid rinsed, cold rolled thin, then annealedbetter surface qualitygood workabilitymost unibody panels are cold rolled steelstamping process increases strength

Cold Rolling Mill to Stampings

Grain Structures of Steel

HSLA

Mild Steel

Properties of Steel

Mild Steel HSS HSLAUHSSAHSS

up to 30,000 psi yield strength

30 - 70,000 psi yield strength

75 - 100,000 psi yield strength

100- 160,000 psi yield strength

110 180,000 psi yield strength

HSS

Gets its initial strength during the heating/cooling treatment from the steel manufacturerIs used mainly for load bearing components in the body structure, however more commonplace today throughout entire body structureMay be repaired cold or with controlled heatMore difficult to repair than mild steelYield strength of up to 70,000 psi.Lack of available identification for HSS means treat all steel as HSS!

HSLA

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 applicationFound in areas such as:Door intrusion beamsBumper reinforcementsLock pillarsFront and rear frame railsHinge pillars (A,B,C)Yield strength up to 110,000 psi.

UHSS/AHSS

The strongest of the structural steels found in today's automobilesOften referred to as Boron, Martensitic, Dual phase steelsFound in these areas:Front and rear bumper reinforcementsintrusion beamsA,B,C pillars (some vehicles)No heat whatsoever is to be applied to any component of this designation!These steels are generally not repairableRequire special considerations when removing/sectioning

Identification of Steels

Location and application of HSS steels vary widely from manufacturer to manufacturerSources of information include:OEM body repair manualsInternet sources (OEM approved)Mitchell manuals (estimating manuals)If you cannot positively identify the makeup of a component, you must treat it as HSS!

HSS Locations

Part Loading

Tension: a load that tries to pull parts straight apartCompressiona load that forces parts straight into one anotherShearA load that pulls sidewaysCleavagea load that pulls parts away from each other at an anglePeela load that pulls parts straight away from one another

Loads present during a collision

Terminology

Yield strength: The minimum amount of force any piece of metal can resist without bending or deforming permanentlyYield Point: The amount of force that a piece of

metal can resist without tearing or breaking

Tensile strengthis measured as the maximum force per unit of area that causes a complete fracture of break

Terminology

Work HardeningIs the upper limit of plastic deformation, causing the metal to become hard in the bent areaMalleabilityis the property which allows deformation under compression or upsetting (shrinking)Elasticityis the ability of the metal to be bent or stretched and spring back to its original shape

Terminology

Plasticity: The property that permits metal to change shape when sufficient force is applied to itPlastic 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

Terminology

Torsional strengthis the property of a material to withstand a twisting forceShear Strengthis a measure of how well a material can withstand forces acting to cut or slice it apartCompressive Strengthis the property of a material to withstand being crushed

Metal Strength Terminology

Elastic Deformation

Plastic Deformation

Terminology

Rigidity: Opposite of plasticity. example: Cast iron will not bend or deform, it will only break under loadDuctility: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 Metal

The point at which Steel melts is 2600 Degrees FWe 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 F Pale yellow / Straw / Brown / Purple / Light Blue Dark Blue / 600 degrees F Reddish Glow / 900 degrees F Blood Red / Dark Cherry 1200 F Cherry Red 1550 degrees F Critical Point 1600 degrees F

Low Crown

High Crown

Reverse Crown

Buckles

Buckles occur when metal has been bent past its elastic limitWork hardening has occurred and a new shape is formedThe buckles found in indirect damage are as follows:simple hingecollapsed hingesimple rolledcollapsed rolled

Direct and Indirect Damage

Impact effect on a High Crown

Effect of damage on a Low Crown Panel

Effect of impact on a combination High / Low

Crowned Panel

Tension can only be removed by unlocking the

pressure areas

Combination of Buckles

simple hinge buckle

two types of rolled buckles

Collapsed hinge buckle

Steps in Unlocking Damage

First in last out

Collapsed Roll Buckle

What happens to the Steel upon impact?

In this case, the damage (Hinged Buckle) has

caused severe damage to the molecular structure

Hammering helps the atoms to vibrate back

into shape, or order

Tools

HammersDolliesSpoonsDent pullersBody picksOxy-Acetylene Body files

Body Hammers

Hammers

Holding the Body

Hammer

Dollies

Holding the Dolly

Using the Corner of the Dolly

Using the Edge of the Dolly

Using the Dolly as

a tool for bumping

Spoons

Uses of the Body Spoon

Can be used as a

dolly in hard to reach

areas

When used with

due 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 Tools

Pry BarsSuction CupsStud WeldersPorta-spot Dent PullersBody FilesSlap FilesHydraulic Porta-Power

Dent Removal Tools

Dent Removal Systems

Hammer Maintenance

Depending on the

condition of your

hammer, several

steps may need to

be taken to restore

the mirror finish

to the surface on

the face of the

hammer.

From filing to

wet sanding and

polishing.

Locating Damage

VisuallyPhysicallyMechanically

Use your sense

of sight and the

reflection of a

light source as a

means of damage

identification

If a visual reference

is not possible, feeling

for damage will be

more 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 off Dolly

Metal Fundamentals

Properties of steel Working the metal Heat Shrinking

Detecting an Oil Can or stretched area

Time to Shrink!

Shrinking

Shrinking Procedure

- Hold torch

at right angle

to panel

- heat metal

to desired

degree

- place dolly

behind area

to be shrunk

- hammer area

from centre out

- quench

immediately with

wet sponge

Cold Shrinking

Using a Carbon Rod for heat shrinking

Repair 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 filePanel shrinking Removal of small dents and bulges Filling with body filler Filing, sanding, and priming the fill area Rustproofing the back side of panelsCompletion of repairs

End of Metal Repair Fundamentals