Presentation on theme: "1st Year Apprenticeship Metal Work In this block you will learn about: Metals and their properties Deformation effects after impact Tools used for effective."— Presentation transcript:
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 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
HSS 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!
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 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/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 whatsoever is to be applied to any component of this designation!No heat whatsoever is to be applied to any component of this designation! These steels are generally not repairable Require special considerations when removing/sectioning
Identification 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)Internet sources –Mitchell manuals (estimating manuals) If you cannot positively identify the makeup of a component, you must treat it as HSS!If you cannot positively identify the makeup of a component, you must treat it as HSS!
Part 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
Terminology 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
Terminology 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
Terminology 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
Terminology 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
Terminology 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 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 F Light film of scale (iron oxide) 430 F Pale yellow / Straw / Brown / Purple / Light Blue Pale yellow / Straw / Brown / Purple / Light Blue Dark Blue / 600 degrees F Dark Blue / 600 degrees F Reddish Glow / 900 degrees F Reddish Glow / 900 degrees F Blood Red / Dark Cherry 1200 F Blood Red / Dark Cherry 1200 F Cherry Red 1550 degrees F Cherry Red 1550 degrees F Critical Point 1600 degrees F Critical Point 1600 degrees F Temperature and Colour Change Light film of scale (iron oxide) 430 F Light film of scale (iron oxide) 430 F Pale yellow / Straw / Brown / Purple / Light Blue Pale yellow / Straw / Brown / Purple / Light Blue Dark Blue / 600 degrees F Dark Blue / 600 degrees F Reddish Glow / 900 degrees F Reddish Glow / 900 degrees F Blood Red / Dark Cherry 1200 F Blood Red / Dark Cherry 1200 F Cherry Red 1550 degrees F Cherry Red 1550 degrees F Critical Point 1600 degrees F Critical Point 1600 degrees F
Buckles 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
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
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 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
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