4291128
Description
Flashcards by Charlotte Walker, updated more than 1 year ago
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Created by Charlotte Walker
over 8 years ago
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| Question | Answer |
| describe the structure of metals | metals are made up of crystals - each crystal is bonded to its neighbor. there are strong metallic bonds holding the atoms together - giving strength in compression and tension. metallic bonds allow free electrons - gives them excellent heat and electricity conductivity. |
| what are ferrous metals and their properties? | ferrous metals contain iron. this means they rust over time and are also magnetic. ferrous metals include steels - stainless (alloy), high carbon, medium carbon and mild steel. Also, nickle and colbolt are ferrous metals. |
| what are non ferrous metals and what are their properties? | do not contain iron - will not rust over time non ferrous metals are not magnetic. examples - aluminium, lead and zinc. |
| what are alloys? | alloys are a mixture of two or more metals. They are made to improve the properties of the metals used to make them - the improvements include color change, strength increase, ductility and hardness. examples - brass, bronze and stainless steel |
| mild steel - properties and uses? | less than 0.3% carbon high ductility and toughness - low hardness. used in nuts, bolts, washers, panels for cookers and other white goods - kitchen appliances. |
| medium carbon steel - properties and uses? | 0.3%-0.6% carbon next highest ductility and toughness - next lowest hardness. used in springs and general gardening tools. |
| high carbon steel - properties and uses? | 0.6%-1.7% carbon - medium ductility, medium hardness - low toughness. used in hand tools, chisels and plane blades. |
| cast iron - properties and uses? | 3.5% carbon + low ductility, very brittle and high hardness. used in machine parts, brake disks and engine parts. Also used in vises. |
| what is aluminium used for and what 3 properties make it good for this use? | uses - aluminum fizzy drinks cans malleable therefore... good corrosion resistance therefore... recyclable... |
| what is gold used for and what properties make it good for this use? | uses - sim cards (or jewelry) excellent electrical conductivity therefore... comes in its pure form therefore... most malleable of all metals therefore... |
| what is copper used for and what properties make it good for this use? | uses - copper wire and piping. ductile therefore... god corrosion resistance therefore... good electrical conductor therefore... |
| what is platinum used for and what properties make it good for this use? | uses - thermo-coupling cables |
| what is lead used for and what properties make it good for this use? | uses - flashing on windows and roofs. very durable therefore... malleable therefore... |
| what is tin used for and what properties make it good for this use? | uses - coating for tin cans. corrosion resistant therefore... naturally shiny therefore... very hard therefore... |
| what is sliver used for and what properties make it good for this use? | uses - cutlery |
| what is titanium used for and what properties make it good for this use? | uses - medical prosthetics e.g. hip joints. good strength to weight ratio therefore... inert material therefore... |
| what is the alloy zinc used for and what properties make it good for this use? | uses - a protective coating added to steels; for screws, railings etc. extremely resistant to corrosion therefore... suitable for galvanizing therefore... |
| what is the alloy brass used for and what properties make it good for this use? | uses - valves in electrical plugs and sockets good electrical conductor... resists corrosion due to zinc content therefore... |
| what is the alloy duralumin used for and what properties make it good for this use? | uses - aircraft industry high strength to weight ratio therefore... can be age hardened therefore... |
| what is the alloy nitinol used for and what properties make it good for this use? | uses - dental braces and glasses frames. shape memory alloy therefore... |
| what is the alloy stainless steel used for and what properties make it good for this use? | uses - sinks and cutlery doesn't rust of corrode due to chromium therefore... aesthetically pleasing due to natural shiny finish therefore... |
| what is the alloy high speed steel used for and what properties make it good for this use? | uses - power tools and drill bits/saw blades can still cut at red hot temperatures therefore... cuts faster than high carbon steel and doesn't loose its hardness therefore... |
| what is the alloy tool and die used for and what properties make it good for this use? | uses - tools and extrusion dies excellent wear resistance therefore... good compression strength therefore... |
| what is the alloy high tensile steel used for and what properties make it good for this use? | uses - bridges e.g. the fourth road bridge designed by Gilbert Roberts and William Brown. good tensile strength therefore... generally corrosion resistant... |
| what is annealing? | a softening process - used to make metals more malleable and easier to work with. metal is heated until cherry red - then slowly cooled leaving the steel softer. |
| what is hardening? | steel is heated to a cherry red color - it is then quickly quenched in water or oil to cool it rapidly. this stops the crystals from moving and makes them hardened into one position. this makes the steel a lot harder but much more brittle. |
| what is tempering? | this follows the hardening process (usually of medium or high carbon steel) this removes the brittleness of a material - makes it tougher. reduced the internal crystal stresses and allows the atoms to relax. how its done - the metal is cleaned with a wire brush then heated to the correct color and then rapidly quenched again in oil or water. |
| what is normalizing? | stress revealing process used after cold working e.g. ending or twisting. crystal structure is allowed to become uniform again. steel is heated in a furnace - temperature is maintained until all the crystals have been refined. metal is then cooled off slowly in s room with still air. the metal will be tougher and more ductile after normalizing. |
| what is age hardening? | generally used in aluminium and copper alloys - aluminium. after heat treatment the material is left for a long period of time. the internal structure moves slightly making the structure stronger and harder |
| what is flame and induction hardening? | heating the surface - then cooling rapidly using a jet or water. used for gears. certain specific areas of the product can be hardened leaving areas that do not need hardening unaffected. cannot be done to mild steel. material is not affected by grain growth therefore now additional processes needed. |
| what is general case hardening? what are the advantages of this? what 2 types of case hardening are there? | case hardening is a method or hardening mild steel. carbon forced into the skin of the metal - giving a hard outer casing - containing more carbon than the core. advantages - used in products that need to be hard on the outside to resist wear and tear but soft on the inside to absorb shock or sudden impact. 2 types - carburizing and nitriding. |
| what is carburizing? advantages and disadvantages? | metal is placed in a box filled with carbon rich materials. it is then heated for a required length of time - different lengths of time give different carbon contents. after carburising the material is quenched to produce the hard case. advantages - cheaper than other methods ass lower temperatures are used disadvantages - more time consuming. |
| what is nitriding? advantages and disadvatages? | where a material is immersed in nitrogen and heated to 500 degrees. used only on specialist steels containing aluminium, chromium and vanadium. used in areo-engines. advantages - no chance of cracking on the surface, increased corrosion resistance, economical in large numbers and a clean process. disadvantages - high set up cost, if the object is over heated there can be a permanent loss of hardness. |
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