1. Materials

2. Metal Metals are chemical elements that are good conductors of electricity and heat. Metals are extracted from mineral ores. Metals with high density are called heavy metals: Iron, silver, gold, cadmium etc. Metals with low density are called light metals: Aluminium, magnesium, titan etc.

3. Steel Steel is an alloy of mostly iron, with 0,2%-2,1% carbon. Most common material for mechanical work. Much carbon makes steel hard and strong, but also less ductile. Other alloy materials gives the material other properties. Alloys with higher carbon than 2,1% are known as cast iron. http://en.wikipedia.org/wiki/Steel

4. Carbon content Less carbon: – Easy to machine and weld – Soft and ductile More carbon: – Strong and hard, but rigid Steel with little carbon needs a higher temperature for tempering.

5. Different kinds of steel Carbon steel – With no specified alloy materials beside carbon Alloy steel – With other alloy materials Construction steel Tool steel

6. Carbon steel 0,1-1,7% carbon, can have small amounts of silicon and manganese Easy to work with Suitable for big constructions with no special demands for strength or other properties, and tools for working with soft materials http://en.wikipedia.org/wiki/Carbon_steel

7. Alloy steel Alloyed with different materials, such as chrome, manganese, sulphur and many other, to improve certain material properties. Low alloy steel High alloy steel http://en.wikipedia.org/wiki/Alloy_steel

8. Stainless steel Stainless steel is alloyed with at least 11-12% chrome to make it withstand corrosion. May also be alloyed with other materials, such as molybdenum and nickel. Stainless steel is harder and therefore needs lower cutting speed. http://en.wikipedia.org/wiki/Stainless_steel

9. Free machining steel Alloyed with sulphur, lead or other materials to make it easier to machine. Form small chips when worked. http://en.wikipedia.org/wiki/Free_machining_st eel

10. Strength testing The steel is tested by stretching to find the limit where the atomic structure of the material is altered. Limit is called yield strength. The point of breakage is called breaking strength. http://en.wikipedia.org/wiki/Strength_of_ma terials http://en.wikipedia.org/wiki/Tensile_strength

11. Property class 10.9 Yield strength is 10·100 = 1000N/mm² Breaking strength is 0,9·1000 = 900N/mm² We can calculate the right torque or look it up in a table

12. Hardening of steel Steel is tempered to change the structure of the material. We will want to be in the lower section of the austenitic area. https://en.wikipedia.org/ wiki/Tempering_(metal lurgy)