Lec-3-Classification-of-Materials-1.pptx

Classification of Materials Materials Selection Process factors that influence both material and process Metals Metals are the most commonly used class of engineering material Metal alloys are especially common, and they are formed by combining a metal with one or more other metalli...

Classification of Materials Materials Selection Process factors that influence both material and process Metals Metals are the most commonly used class of engineering material Metal alloys are especially common, and they are formed by combining a metal with one or more other metallic and/or non-metallic materials. The combination usually occurs through a process of melting, mixing, and cooling. The goal of alloying is to improve the properties of the base material in some desirable way The metals may be further classified as: Ferrous metals and Non-ferrous metals Ferrous and Non-ferrous Metals The ferrous metals are those which have the iron as their main constituent, such as cast iron, wrought iron and steel. The non-ferrous metals are those which have a metal other than iron as their main constituent, such as copper, aluminum, brass, tin, zinc etc.  General Categories of Ferrous Metals and Alloys Ferrous alloys have iron as the base element. These alloys and include steels and cast irons Carbon steels are basically just mixtures of iron and carbon. They may contain small amounts of other elements, but carbon is the primary alloying ingredient Low-carbon steel has less than about 0.30% carbon. It is characterized by low strength but high ductility Medium-carbon steel contains between about 0.30% to 0.70% carbon. It can be heat treated to increase strength, especially with the higher carbon contents High-carbon steel contains between about 0.70% to 1.40% carbon. It has high strength but low ductility General Categories of Ferrous Metals and Alloys Low-alloy steels, also commonly called alloy steels, contain less than about 8% total alloying ingredients. Low-alloy steels are typically stronger than carbon steels and have better corrosion resistance. Tool steels are primarily used to make tooling for use in manufacturing, for example cutting tools, drill bits, punches, dies, and chisels. Stainless steels have good corrosion resistance, mostly due to the addition of chromium as an alloying ingredient. Stainless steels have a chromium composition of at least 11%. General Categories of Ferrous Metals and Alloys Cast iron is a ferrous alloy containing high levels of carbon, generally greater than 2%. Gray cast iron is the most common type. The carbon is in the form of graphite flakes The addition of magnesium to gray cast iron improves the ductility of the material. The resulting material is called nodular cast iron because the magnesium causes the graphite flakes to form into spherical nodules. It is also called ductile cast iron White cast iron has carbon in the form of carbide, which makes the material hard, brittle, and difficult to machine Malleable cast iron is produced by heat treating white cast iron  COKE Coke is formed by heating coal to 2100*F (1150 C), then cooling it in quenching towers.  Limestone (calcium carbonate) is used to remove impurities. IRON MAKING Cupola or Cupola Furnace is a melting device used in foundries that can be used to melt cast iron.