Keywords : Alloy, carbon steels, low-alloy steels, high-alloy steels

2. Properties of iron & steels Prior Learning: Identify & explain different extraction processes Keywords: Alloy, carbon steels, low-alloy steels, high-alloy steels

3. Learning Objectives: By the end of the lesson I can: • The properties of pig iron and how this limits its usefulness. Pig iron is the intermediate product of smelting iron ore with coke. Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications. • That iron can be alloyed to make it more useful. • Explain how the properties of alloys (but not smart alloys) are related to models of their structures.

4. What are the properties of different metals?

5. gold (Au): This metal is unreactive. This is represented by having the band on stage, not mixing with the other elements and not doing very much. lead (Pb), zinc (Zn) and copper (Cu): These metals are heavy metals and are dressed up as heavy metal rockers. copper (Cu): This metal has been drawn into wires. aluminium (Al) and titanium (Ti): These metals are reactive. In this scene, they are getting overexcited and knocking over a table. iron (Fe): This metal has rust patches and is struggling to lift the bar stools. steel (Fe wearing ‘nerves of steel’ T shirts): These metal alloys have carbon atoms on their shoulders to show that they are alloys. The steel is shinier than the iron atom. Steel is easily lifting the bar stools that iron was unable to lift because it is stronger.

6. Let’s go back in time 3 years to Year 7 Now add a different sized particle to your model. What is this called? And draw (or make a model to show) the atom arrangement in a solid YEAR 10 YEAR 7

7. What are the general properties of most metals? • solid at room temperature • high melting point • good conductors of electricity and heat • malleable: they can be shaped • ductile: they can be drawn into wires • strong • dense Why do metals have these particular properties?

8. The atoms in a pure metal are in tightly-packed layers, which form a regularlattice structure. sea of electrons The outer electrons of the metal atoms separate from the atoms and create a ‘sea of electrons’. These electrons are delocalized and so are free to move through the whole structure. The metal atoms become positively charged ions and are attracted to the sea of electrons. This attraction is called metallic bonding. metal ions

9. How does the sea of electrons affect the properties of metals?

10. heat Delocalized electrons in metallic bonding allow metals to conduct heat and electricity. For example, when a metal is heated, the delocalized electrons gain kinetic energy. These electrons then move faster and so transfer the gained energy throughout the metal. This makes heat transfer in metals very efficient. Delocalized electrons also conduct electricity through metals in a similar way.

11. Metals are usually strong, not brittle. When a metal is hit, the layers of metal ions are able to slide over each other, and so the structure does not shatter. metal before it is hit metal after it is hit force force The metallic bonds do not break because the delocalized electrons are free to move throughout the structure. This also explains why metals are malleable (easy to shape) and ductile (can be drawn into wires).

13. How would you investigate the strength of alloy wires? What will you change? (The independent variable) What will you measure? (The dependent variable) How would you make it a fair test? (Controlled variables) Investigating Alloys

14. On a plain piece of paper add information from the following slides to create a mind map on iron including; Alloying Extraction Properties Chemical information (Anything else you wish to include)

15. The iron collected from a blast furnace is only 96% pure. Usually, this product will be treated further because the impurities make iron brittle. raw materials Removing all impurities would produce pure iron. Pure iron has a regular arrangement of atoms, with layers that can slide over each other, and so is soft and easily shaped, but too soft for many uses. hot air Most iron is converted into steels. molten iron molten slag

16. Steel is an alloy of ironand other elements, including carbon, nickel and chromium. Steel is stronger than pure iron and can be used for everything from sauce pans… …to suspension bridges!

17. The atoms in pure iron are arranged in densely-packed layers. These layers can slide over each other. This makes pure iron a very soft material. The atoms of other elements are different sizes. When other elements are added to iron, their atoms distort the regular structure of the iron atoms. It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron.

18. Steels are alloys, since they are mixtures of iron with carbon and other metals.The different sized atoms distort the layers in the structure of the pure metal, making it more difficult for them to slide over each other, and so alloys are harder.Alloys can be designed to have properties for specific uses.Low carbon steels are easily shaped, high carbon steels are hard, and stainless steels are resistant to corrosion. OVERVIEW - Steel

19. Steel is not a single substance & there are lots of different steels all being an alloy of iron with either carbon and/or other elements. 1. CARBON STEEL: made by alloying Fe with small amounts of C (from 0.03-1.5%). They are the cheapest to make & are used for car bodies, knives, ships, machinery, containers, structural steel for buildings. • low carbon steelcontains less than 0.25% carbon Soft and easily shaped. Not as strong as high carbon steel but less likely to shatter. • high carbon steelcontains more than 0.5% carbon. Very strong but brittle.

20. 2. LOW-ALLOY STEEL: made by alloying Fe with small amounts of other metals (from 1-5%). They are more expensive & may contain metals like Ni, Cr, Mn, V Ti and W. Each giving a different property. • Nickel-steel very resistant to stretching forces so are used for long-span bridges, military armour-plating • Tungsten-steel operates well under very hot conditions so it is used to make high-speed tools.

21. 3. HIGH-ALLOY STEEL: made by alloying Fe with large amounts of other metals. They are EVEN more expensive & may contain metals like Ni, Cr, Mn, V Ti and W. Each giving a different property. • Chromium-steel strong with chemical stability it is mixed with between 12-15% Cr and often some Ni • This is also known as ‘stainless steel’ These are used to make cooking utensils & cutlery, chemical reaction vessels because they combine hardness & strength with a resistance to corrosion (they do not rust!)

24. If its true it stays, if its false SEND IT OFF! plenary Ref’s Decision Steel is a mixture All steels contain cobalt (Co) Stainless steels are expensive Stainless steels rust because they contain iron The molecular formula for steel is St Yellow = TRUE, Blue = FALSE

25. Learning Objectives: By the end of the lesson I can: • The properties of pig iron and how this limits its usefulness. Pig iron is the intermediate product of smelting iron ore with coke. Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications. • That iron can be alloyed to make it more useful. • Explain how the properties of alloys (but not smart alloys) are related to models of their structures.