Materials and Joins

​Materials and Joins: Safety, Properties, Processes

By

• Eye, hand, foot protection
• Guards and clamping
• Consequences of ignoring PPE

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Workshop safety and PPE

Multiple Choice

What is the best eye protection when grinding?

• Ear muffs

• Safety glasses

• Dust mask

• Welding gauntlets

• Magnetic vs non-magnetic
• Ductile vs malleable
• Properties affect join choice

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Metals & Properties

Multiple Choice

Which stock is magnetic?

• Aluminium

• Brass

• Mild steel

• Copper

• Ductile = bends/draws
• Malleable = hammered to shape
• Hard/Tough resist wear/impact

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Key Terms: Ductile, Malleable, Hardness, Toughness

Multiple Choice

“Ductile” best means the metal can…

• Resist scratching

• Be drawn or bent without cracking

• Conduct heat poorly

• Rust quickly

• Mechanical: bolts, rivets
• Fusion: welds by melting
• Choose by load and access

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Joint Families: Mechanical vs Fusion

Multiple Select

Select the mechanical fasteners.

• Bolts

• Pop-rivets

• MIG weld

• Oxy-fusion

• Wire + shielding gas
• Short, consistent stick-out
• Fit-up and tacks first

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MIG Essentials

Multiple Choice

A MIG welder uses a consumable…

• Tungsten

• Wire electrode

• Flux rod

• Plasma torch

• Stick flux makes shielding
• Less wind-sensitive than MIG
• For MIG use shields/indoors

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Stick (Arc) vs MIG Outdoors

Multiple Choice

Why is stick more reliable than MIG outdoors?

• Higher voltage

• Flux shields the arc from the wind

• Heavier cables

• Bigger nozzle

• Clean to bright metal
• Set parameters, fit-up, clamp
• Tack before full weld

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Prep & Clamping Workflow

Multiple Choice

Which option shows the correct MIG setup workflow?

• Set parameters → Weld → Clamp & tack → PPE/clean

• PPE/clean → Set parameters → Clamp & tack → Weld

• Clamp & tack → PPE/clean → Weld → Set parameters

• PPE/clean → Clamp & tack → Set parameters → Weld

• Zinc fumes risk
• Coating causes porosity
• Grind off zinc, extract fumes

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Galvanised Steel Hazards

Multiple Select

Best controls before welding galvanised steel?

• Grind off zinc near joint

• Use fume extraction

  /PPE

• Paint first

• Longer stick-out

Name the defect
• First corrective action
• Cleanliness first

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Defects & First Fixes

Multiple Choice

First fix for lack of fusion in a fillet weld?

• Paint the joint

• Clean base + adjust parameters

• Smaller gloves

• Weld faster

• Base metal changed by heat
• Properties shift near weld
• Manage with correct heat

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​Heat-Affected Zone (HAZ)

Multiple Choice

The HAZ is the…

• Area untouched by heat

• Only the weld bead

• Base metal changed by welding heat

• Quenched zone far away

• Mark and centre-punch
• HSS bit and clamp the stack
• Use washer as needed

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Drill & Rivet / Bolt Workflow

Multiple Choice

Best practice for drilling and riveting?

• Wood bit, no clamp, eyeball

• HSS bit, clamp, centre-punch

• Masonry bit, clamp optional

• Any bit, freehand