Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company What is Materials Science and Engineering? Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company The aim of this module is to introduce you to the subject of materials science and engineering and give you an appreciation of why it is important to understand the processing, structure and properties of materials. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Materials processing Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company The session aims to introduce you to a variety of different ways in which materials can be processed. At the end of this session you should be able to: Appreciate the importance of understanding the relationship between structure, properties and processing; Explain processes for casting materials and the considerations that need to be made; Explain processes that involve the application of a force such as rolling, extrusion and forging and the types of products that can be made in this way; Describe near-net shape manufacturing processes such as 3D printing. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Materials are processed, formed, shaped or manufactured to make the products that we take for granted. Processing generally involves the application of heat and a force and these two things can both affect the structure of the material. Changing the cooling rate can affect the degree of crystallinity and grain size. Repeated deformation, particularly at lower temperatures can introduce defects to the structure. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Casting processes are ancient and in their simplest form involve pouring molten material into a mould to make a component close to its final shape. In reality there are many more considerations such as: Controlling the cooling rate Ensuring that the mould is completely full Avoiding splashing as the mould is filled Minimising waste material Some casting processes are very rapid (die casting for metals and injection moulding for polymers). Some casting processes are very time consuming such as sand and investment casting. Sometimes continuous casting is used to produce long lengths of material ready for further processing. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Injection moulding can be used for making many different components from many different polymers. The basic machinery is expensive (about £300,000) but the moulds are even more expensive as they have to be made very carefully out of very hardwearing materials. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Sand casting is used to make metal components and is a very ancient process. The mould is made by pressing a pattern into a box containing a special sand. The mould is made in two halves and once the sand has cured (so it is solid) the two parts are put together. Molten metal is carefully poured into the mould and allowed to solidify, which in very large castings can take days. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Continuous casting is used to make long lengths of metal which are cut to size for subsequent processing. Liquid metal from a ladle (1) is poured into a tundish (2) in which plasma torches (4) maintain the temperature. When the plug (5) is removed the metal flows into the water cooled mould (3) where a skin forms and it starts to solidify. Once it has solidified sufficiently in the straight zone (6), is it turned through 90 º by a set of rollers and allowed to run out on to a cooling table. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Forming processes involve the application of a force to change the shape of the material. The feedstock for these processes can take many forms, for example, slab, bar, or rod, and is dependent on the shape of the final product. Processes can be described by the temperature at which they are carried out: Hot working is performed above the recrystallisation temperature, typically about half of the melting point. Cold working is performed below the recrystallisation temperature. Forming processes include rolling, extrusion, forging, drawing, stretch forming, deep drawing, and pressing. It is generally easier to start forming at high temperature when the material is soft and easier to deform. Key properties for forming processes are ductility and malleability. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Rolling can be used to produce plates or sheets of material ranging from many centimetres to less than a millimetre thick. A reversing mill is used at high temperature to apply large forces and produce large reductions in thickness. A train of non-reversing mills can be used at lower temperature to produce thin sheet. In a typical process a steel slab measuring 220mm thick and 11m long would be reheated to 1250 º C. A hot reversing mill then applies several high deformation passes to reduce the thickness to around 30mm, with a corresponding increase in length to 80m. This is often called the roughing stage. The heavy plate is transferred to a series of non-reversing mills where it is rolled to its final thickness and coiled. The final strip would typically be 2mm thick but 1300m long. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Forging is an ancient process in which a striking force is applied to deform the material. Traditionally a hammer and anvil were the tools of the smithy. Modern forging machines use gravity or power-assisted tools to shape components weighing up to many tonnes by forcing material into a mould or die. Forging can be a very accurate and precise process and it is used to make many components including aerospace and automotive parts. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Extrusion involve forcing a rod, or bar through a die so that it takes on the desired cross section. It is a bit like squirting toothpaste out of a tube or piping icing. Extrusion can be used to produce complex profiles in metals such as aluminium or in polymers. Extrusion can also be used to make seamless tubes (including pasta!). Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Most manufacturing processes include a finishing stage which might involve machining to: Remove waste Drill holes Improve surface finish Traditional cutting tools are very hard (tungsten carbide, silicon carbide, PCD, tool steels). Modern methods include laser cutting, electrical discharge machining and water cutting. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Near net shape manufacturing (NNSM) is concerned with making components as close to their final shape with as fewer processes as possible in order to minimise waste material and conserve energy. 3D printing is the most common NNSM process and it is largely used for rapid prototyping rather than large scale manufacture as it is very time consuming. However, the technique has been used to build biological scaffolds for tissue engineering. The process involves laying down successive layers of material in order to build up a 3D component. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Materials Scientists and Engineers have a wide variety of forming techniques at their disposal in order to be able to manufacture the myriad of complex objects that we take for granted everyday. The properties required of the final component will influence the type of process used as heat and deformation can affect the structure and therefore properties of the material. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM3 Investigating casting Investigating extrusion Investigating finishing processes

Armourers and Brasiers Company A practical activity to look at fluidity is given in the Teachers Pack on Experiments in Materials Science. Use the casting facilities in your D&T department to investigate how to make a mould and running system to make a simple casting. Research products made by different casting methods such as bells, ship propellers, bottle tops, etc and compare the various techniques. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company A practical activity to look at extrusion is given in the Teachers Pack on Experiments in Materials Science. Research different products made by extrusion and identify why this has been the most relevant processing technique Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Using equipment in your D&T department investigate the materials and techniques used for cutting and polishing. Prepared by Dr Diane Aston, IOM3

Armourers and Brasiers Company Prepared by Dr Diane Aston, IOM3