Metal Based Materials

This section explores metal-based materials, their selection, properties, and uses in various applications. We will cover key areas like forces and stresses, ecological impact, and manufacturing processes, helping you understand how metals are used in design and technology.

Selecting Materials

When selecting metal-based materials, designers consider several factors:

• Strength: Different metals have varying levels of strength. Steel, for example, is strong and is used in structural applications, while aluminium is lighter but still strong enough for applications like aerospace or packaging.
• Weight: The weight of the material is an important consideration, especially in industries such as automotive and aerospace. Aluminium is a lightweight metal, whereas steel is heavier but offers greater strength.
• Corrosion resistance: Metals like stainless steel and aluminium are highly resistant to corrosion, making them ideal for outdoor or marine environments.
• Aesthetic qualities: For products like jewellery, cutlery, or consumer electronics, the finish and appearance of the metal are crucial. Metals can be polished, anodised, or painted to achieve a desired look.
• Cost: Some metals, such as copper or gold, are expensive, while others, like mild steel, are more affordable, which influences material choice in mass production.

Forces and Stresses

Metals are subjected to various forces and stresses in design and use:

• Tensile stress: When metals are pulled apart, the material must be able to resist breaking. For example, steel cables are used in construction because of their high tensile strength.
• Compressive stress: Metals like steel are also used in compression, for example in columns and beams for buildings, where they must withstand large compressive forces without buckling.
• Shear stress: Metals may also experience shear forces, which cause the material to slide or tear. This is common in bolts and rivets that hold metal parts together.
• Bending stress: Bending is common in sheet metals used for car bodies or structural components. Metals must have sufficient flexibility or rigidity to resist permanent deformation under bending forces.

Understanding how metals react to these stresses helps in selecting the right material for specific applications.

Ecological and Social Footprint

The ecological and social footprint of metal-based materials is a key consideration in their selection:

• Ecological footprint: The extraction of metals, particularly from ore, can have a significant environmental impact. Mining for metals like iron ore, aluminium, and copper can lead to habitat destruction, energy use, and pollution. However, recycling metals significantly reduces these impacts, as metals can often be reused without degradation in quality.
• Energy consumption: The production of metals, particularly aluminium, is energy-intensive. However, the recycling of metals like aluminium requires much less energy than producing new material from bauxite ore.
• Social footprint: The extraction and production of metals can raise social issues, including poor working conditions in some countries and the exploitation of local communities. Ethical sourcing and fair trade practices are essential to improving the social footprint of metal-based materials.

Sustainably sourced metals and recycled materials help reduce the ecological and social impact.

Sources and Origins

Metals are derived from ores, and each metal has its own source and extraction process:

• Ferrous metals: These contain iron and are derived from iron ore. Examples include:
• Mild steel: Made from iron and carbon, commonly used in construction, tools, and machinery.
• Stainless steel: Iron alloyed with chromium (and sometimes nickel) for corrosion resistance, commonly used in kitchenware, medical tools, and automotive applications.
• Cast iron: Iron with a higher carbon content, used in heavy-duty applications like engine blocks or manhole covers.
• Non-ferrous metals: These do not contain iron and are often used in applications where strength-to-weight ratio or corrosion resistance is critical. Examples include:
• Aluminium: Lightweight, corrosion-resistant, and used in aerospace, packaging, and electronics.
• Copper: Good conductor of electricity, widely used in electrical wiring and plumbing.
• Titanium: Strong and resistant to corrosion, used in aerospace and high-performance applications.
• Recycled metals: Many metals, particularly aluminium and copper, are recycled and reused, reducing the need for new mining and helping to conserve natural resources.

Use of Material Properties in Commercial Products

The properties of metals make them suitable for various commercial products:

• Steel: Its strength, durability, and formability make it ideal for construction (e.g., beams, bridges, and skyscrapers), automotive parts, and tools.
• Stainless steel: Corrosion-resistant and aesthetically appealing, it is used in kitchen appliances, medical instruments, and high-end cutlery.
• Aluminium: Lightweight and corrosion-resistant, it is used in aerospace, packaging (e.g., cans), and electronics.
• Copper: Excellent electrical conductivity makes copper ideal for electrical wiring and electronic components.
• Titanium: Due to its high strength-to-weight ratio and resistance to corrosion, it is used in aerospace, military, and medical applications (e.g., implants and prosthetics).

Designers choose metals based on these properties to ensure performance, longevity, and cost-effectiveness in their products.

Stock Forms, Types, and UK Sizes

Metals are available in various stock forms and sizes to meet different design needs:

• Sheets: Commonly used for flat products. Sheet metal comes in standard sizes, such as 2.4m x 1.2m or 2.5m x 1.25m, and is available in various thicknesses, typically measured in millimetres (e.g., 0.5mm, 1mm, 3mm).
• Bars: Metal bars are available in round, square, or rectangular shapes, with standard lengths often ranging from 1 to 6 metres, depending on the metal and supplier.
• Pipes and tubes: Available in various diameters and lengths, typically used in plumbing, construction, and mechanical engineering.
• Angles and channels: Metal profiles that are used for structural purposes in construction and manufacturing. Common dimensions include 50mm x 50mm for angles or 100mm x 50mm for channels.

The size and form of the material depend on the production process and the final product requirements.

Scales of Production

The scale of production affects the type of metal and the manufacturing methods used:

• One-off production: In bespoke or high-end products, such as custom jewellery or high-performance aircraft components, metals like stainless steel, titanium, or gold may be used. These metals are often machined or worked by hand.
• Batch production: In products like appliances or furniture, metals like mild steel and aluminium are often used. Batch production allows for efficient manufacturing but with some flexibility for design variation.
• Mass production: For products like car bodies, packaging, or construction materials, metals like mild steel, aluminium, and copper are used in large quantities. Mass production processes like stamping, casting, and welding are commonly employed.

The scale of production influences material selection, cost, and the choice of manufacturing process.

Tools, Equipment, and Processes

Metals require various tools and equipment for shaping, cutting, and joining:

• Cutting tools: Saws (e.g., hacksaw, bandsaw), shears, and plasma cutters are used for cutting metal into the required shapes.
• Forming tools: Hammers, presses, and rollers are used to shape metal, such as in forging or rolling processes.
• Joining tools: Welders (e.g., MIG, TIG welding), riveting tools, and screwdrivers are used to join metal parts together.
• Finishing tools: Sanders, grinders, and polishers are used to smooth the surface of metal products. Additionally, anodising or painting can be applied for corrosion resistance or aesthetic appeal.

Commercial Processes

Metals undergo several commercial processes to be transformed into finished products:

• Casting: Molten metal is poured into moulds to form complex shapes, such as engine blocks or components in automotive and machinery.
• Forging: Metal is heated and hammered or pressed into shape, typically used for making strong parts like tools, shafts, or automotive components.
• Rolling: Metal is passed through rollers to reduce its thickness and create sheets or coils, commonly used in steel production.
• Extrusion: Metal is forced through a die to create continuous shapes, like pipes or profiles used in construction.
• Welding: The process of joining metal parts by melting the edges and fusing them together. Common in construction and automotive industries.
• Machining: Includes processes like milling, turning, and drilling, which are used to shape and finish metal parts.

Summary

Metal-based materials are versatile and essential in modern design and technology. Understanding their properties, selection criteria, and commercial processes is critical for making informed decisions in product design and manufacturing. Whether for structural components, consumer products, or high-performance applications, metals play a crucial role in a wide range of industries.