Engineering Materials

Resource 4

Manufacturing Techniques

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Aims & Objectives

• Identify engineering materials & uses• Differentiate metallic & non-metallic materials• Understand the hardening & tempering processes

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• Select appropriate materials for manufacturing activities• Identify materials properties & uses• Manufacturing processes for a range of materials• Harden & temper materials

Aims & Objectives

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Materials

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Ferrous Metals

• Mild steel• Cast iron• Wrought iron• High carbon steel• Stainless steel

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Uses

• Mild steel – Structures, Bridges, Steel products, Nuts & bolts

• Cast Iron – Castings, Engines, Machine vices

• Wrought Iron – Gates, railings

• High Carbon Steel – Tools, drills, centre punch, chisels, files

• Stainless Steel – Cutlery, Kitchen & bathroom appliances, medical instruments

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Non Ferrous Metals

• Copper • Brass• Lead• Aluminium• Silver• Gold• Zinc

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Uses

• Copper – Pipes, electrical wiring, kitchen ware

• Brass – musical instruments, tableware, ornaments

• Lead – Batteries, soldering, roofing & cladding

• Aluminium – Aircraft, Window frames, Kitchen ware, cans

• Silver – Jewellery, coins, cutlery

• Gold – Jewellery, coins, cutlery, dentistry

• Zinc – Galvanising steel products

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Alloys

Some metals can be used in their pure form or combined with other metals to produce an Alloy metal. An alloy is a combination of two or more metals to improve the mechanical properties of the materials. A few materials are listed below: -

• Brass• Bronze• Stainless steel• High carbon steel

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Forms of supply

Materials can be cut in various shapes & sizes.

Round Flat Square Hexagonal Octagonal Sheet Channel Angle Square Tube Round Tube

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Grain Structures

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Crystalline & Amorphous

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Crystalline

During the solidification process, crystals begin to form, multiply and grow until the material is completely solidified. These crystal contain atoms that are packed tightly together forming patterns.

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Amorphous

Rapidly increasing the cooling rate during the solidification process can produce minuscule micro crystals or in some cases amorphous that

is, non-crystalline solid liquid metals. The non-crystalline liquid structure is retained since the opportunity

for crystallisation is avoided due to the extreme temperature change.

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Heat treatment processes

HardeningHardening is accomplished by heating the material (metal) to a required temperature between 800°C & 1500°C (depending on the properties required) then quenching in either oil or water.

TemperingTempering consists of re-heating the material between 200°C & 600°C (depending on the properties required) then quenching in either oil or water.

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Case Hardening

Case hardening produces a hard, wear resistant surface on low carbon steels.

The process is accomplished by heating the material between 800°C & 1500°C and infusing carbon elements onto the materials surface.

Re-heat material between 800°C & 1500°C (depending on the properties required) then quenching in either oil or water.