Dimensional Elements Eng. Moises Castro Flores

Metals We call metals to each of the chemical elements that conduct heat and electricity, with a characteristic shine, and solid at ordinary temperature, except mercury.

Characteristics:  Good conductors of electricity and temperature  High density  Shine  Hardness  Toughness

Molecular structure  Metals differ from other elements, mainly on the type of link which are its atoms. It is a metal link, were the electrons form a "cloud" that moves, surrounding all cores. This type of link is what gives them electrical conduction properties, brightness, etc.

Steels (Ferroalloys)  Ferroalloys, are alloys based on iron and carbon, they include low carbon, alloyed tool steels, stainless steels, cast irons and more. The steels are typically produced in two ways: by refining iron ore or by recycling

Types of steels.  Low carbon steels Most of all steel produced is low in carbon. This type of steel contains less than 0.25% carbon. As a result, these steels are relatively soft and very resistant, but with extraordinary ductility and toughness; moreover, they are easy to machine and weldable. Its used to manufacture automobile bodies, beams (I- shaped, channels and angles) and sheets for building pipes, buildings, bridges and tinned cans.

 Mild carbon steels Mild carbon steels have carbon percentages comprised between 0.25% and 0.6%. They are low hardenability steels, only treatable in thin section parts. Additions of chromium, nickel and molybdenum improve the ability of these alloys to be heat treated, thereby generating many combinations strength - ductility. These steels less ductile. They are used to manufacture railway wheels and rails, gears, crankshafts and other structural components requiring high strength, resistance and toughness.

 High carbon steels The high carbon steels typically contain between 0.60 and 1.4 %, they are harder, tougher and much less ductile than the other carbon steels. They are particularly resistant to wear and able to take the form of cutting tool. The tools and dies are made from high -carbon alloy steel containing, generally, chromium, vanadium, tungsten and molybdenum. These alloy elements combine with carbon to form very hard and wear resistant carbides. These steels are used as cutting tools and dies also knives, saw blades, springs and threads of high resistance.

 Stainless steels Stainless steels resist corrosion (rust) in many environments, especially in the atmosphere. Chromium is the main alloying element in a minimum concentration of 11%. The corrosion resistance is improved with additions of nickel and molybdenum. The wide range of mechanical properties combined with excellent corrosion resistance make this type of steel is very versatile.

Activities  Create a comparative chart or a conceptual map whit all the kinds of steels  Describe the type of bonding (link) of metals.  Why metals can conduct electricity?  What is a Steel alloy?  Which characteristic posses the stainless steels?  What kind of Steel alloy will you use in the next products, explain why.  Sword  Pot  Metal door

Homework  Find at least 7 more elements applied to steel and explain what properties they provide to steel.  What kind of elements have these alloys, and explain what possible properties they have.  Alloy 5230, and 1120