Alloys / stock forms

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Alloys

Alloys are a ‘mixture of metals combined to improve their properties’ such as

changing the melting point (enhanced thermal properties)
colour
Increasing strength
Improving the resistance to corrosion

Ferrous Alloys

Stainless steel

The main Ferrous Alloy is Stainless Steel which is a mixture of Chromium, Nickel and Magnesium added to Steel.

It has a high resistance to corrosion, is very clean and hygienic and is tough and wear resistant making it particularly suitable for kitchenware.

Properties of Stainless Steel:

Hygenic
Non-corrosive
Outstanding surface finish
Excellent toughness
Can be formes using a variety of processes
*difficult to coldwork

tool steel

Also known as die Steel is a high carbon steel with the addition of Chromium and Tungsten. The steel is available in various grades depending on the metal content which varies depending on the application for the steel, but it is hard, tough and durable.

Due to the addition of other metals, tool steel can also be classed as an alloy.

High carbon steel

High Carbon Steel (0.7-1.7% Carbon) is also referred to as High Speed Steel (HSS) and is used for tools, cutting and drilling bits, blades etc.

These can also be considered a Ferous metal!

alloyed with tungsten (7%) or molybdenum, together with percentages of chromium, vanadium and cobalt.

Non ferrous alloys

Brass

Brass is a non-ferrous alloy; a mixture of Copper and Zinc (35%). It is used for valves and taps, ornamental fittings, boat fittings and keys as well as the pins on a plug as it has good conductivity but is stronger than pure Copper.

Properties of Brass

Versatile production
recyclable
Good machinability
good corrosion resistance
good hotworking properties
good combination of strength and ductility

Has been traditionally associated with music "brass band"

Bronze

Bronze is a mixture of Copper and Tin (10%). It is used to make coins, statues and bearings. Due to the high Copper content it can be very expensive!

Duralumin

Duralumin is an Aluminium alloy containing 4% Copper, 1% Manganese and 0.1% Magnesium. It is stronger than Aluminium yet lighter and is therefore ideal for use in the aerospace industry.

Pewter

Pewter is made mainly from Tin with a small amount of Copper and Antimony. It is often used to make decorative items such as tankards picture frames, models and metal gifts. It is now ‘Lead free’ and has a relatively low cost with a very low melting point around 200 degrees C.

Stock forms of metal

When processed, metal takes on a liquid form but it cannot be transported hot so it is available in solid blocks (ingots) once cooled for casting etc.

For fabrication purposes it is available in sheet in a variety of sizes and thicknesses (often referred to as gauge).

It can also be bought in bar, rod and tube (square, rectangle and round) as well as a variety of profiles such as angle (L-shaped), channel (U-shaped). Tee (T shaped) These can be specified in a variety of diameters, wall thicknesses etc

Ingot

Ecological and social footprint

You should have a knowledge and understanding of the ecological and social footprint left by designers, including:

The effect of deforestation, mining, drilling and farming on social communities and on the environment.
Mileage of product from raw material source, distribution, user location and final disposal.
The effect of carbon being produced during the manufacture of products.
The six R’s and their relevance to this material group.
Safe working conditions.
Reducing oceanic/atmospheric pollution and
Reducing the detrimental (negative) impact on others any other current or topical concern relating to the material group studied and their effect directly or indirectly on the environment.

To obtain ores, we need to mine the earth which results in deforestation, loss of animal habitat etc. It also leaves quarries which can be unsightly (ugly).

Ores require heat and power to process them and separate the metal from the earth and other minerals. This increases their carbon footprint.

Ferrous metals can easily be separated from non-ferrous metals in scrap as they are attracted to magnets.

Ferrous metals, when discarded will rust and leave iron oxide as well as potentially sharp edges.

Most metals can be recycled, and responsible disposable of metals will reduce the need for new metals from ores.

Metals are common in industry and commercial products, so their use is often unavoidable.

Designer case study:

Watch from minute 3:19 to see discussion about Marc Newson's Lockheed lounge chair.

Marc Newsons Lockheed lounge

The lockheed lounge is one of australian designer Marc Newson's most famous designs.

The main shape is fiberglass and is clad in riveted aluminum sheet.

The feet of its 3 legs are coated in rubber.

The Lockheed Lounge is named after the aircraft manufacturer.

The aluminum panels that make up the surface of the chair were blind riveted to the hand sculpted fiberglass body.

Summary

Metals are derived from ores found in the earths crust which need to be processed to extract the metal. There are metals that contain Iron (Ferrous) and those that do not (Non-ferrous).

Only Ferrous metals are prone to rust.

Metals are hardwearing and good conductors of heat and electricity.

Most Ferrous metals require a finish to protect them from rust while most non-ferrous do not need a surface finish.

An Alloy is a mixture of metals combined to improve its properties.

Metals are used to make vehicles such as cars, trains and planes as well as cases and housings for phones, washing machines, tv’s etc.

revision notes

For metals and alloys, you should be familiar with the classification, properties and stock forms available for each material.

We will also look at the workshop tests undertaken to identify the mechanical properties of metals (L15).

In a later unit we will look at how metal can be enhanced and finished in the production of products and components.

In your exam answers you will be expected to make reference to the physical and mechanical properties of metal where appropriate and why those properties make them suitable for the particular application.

Make your own chart which puts metals and alloys into categories with key properties and common applications. Alternatively, print the chart off from this presentation.

Exam Question

Go to 1.2 Performance characteristics >

L5-6-Metals.ppsx

L5 - L6 Powerpoint

This presentation contains all of the L5 - L6 content should you wish to review it.