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• **What are the advantages of iron and steel over stone and brick? ** The advantages of iron and steel are stronger material and structures with these materials can be stronger and taller structures with less expenditure of material than stone and brick. The importances of steel and iron after the 20th century are: The evolution of steel frame construction entirely changed the concept of the wall and the support,
 * • What is the importance of steel and iron after the 20th Century? **
 * The steel and iron have made it possible to produce structures stronger and taller with less labour and material. **
 * • What are the characteristics of steel? **
 * The steel is the **alloy of iron and carbon in which the carbon content ranges up to 2 percent (with a higher carbon content, the material is defined as cast iron). By far the most widely used material for building the world’s infrastructure and industries; it is used to fabricate everything from sewing needles to oil tankers
 * • What are the disadvantages of steel and what solutions have been found? **

No
 * • What is welding? What is its importance? Its characteristics. **
 * Welding is the join (metals) by applying heat, sometimes with pressure and sometimes with an intermediate or filler metal having a high melting point.**This it’s important because made it possible to produced fused joints with less labor and material.
 * • What shapes are formed with steel? **
 * Different shaped with are formed steel as bolt, rivets, dowel and clamps. **
 * • Are aluminum and stainless steel heavy metal alloys? **