Manufacture of Iron & Steel. Prepared By: John Cawley

Transcription

1 Manufacture of Iron & Steel Prepared By: John Cawley

2 Presentation Objectives Identify the basic steps in the production of steel. Identify the properties and uses of iron ore and pig iron. Differentiate between common steel making and cast iron making processes. Discuss how rolling mills change steel ingots into different shapes. Describe how cast iron is made.

3 Steel Making Process A two step process: Convert (Melt) Iron Ore into Pig Iron. Which is done in a blast furnace. Take the pig iron and add other alloys to make steel. Which is done in either a basic oxygen or electric arc furnace.

4 U. S. Steel

5 Iron Ore Types (Raw Material) Magnetite 72% Iron (Fe 3 O 4 ) Hermatite 70% Iron (Fe 2 O 3 ) Limonite 50-60% Iron (Fe 3 O 4 ) Siderite 48% Iron (FeCO 3 ) Taconite 20-30% Iron Iron Ore is the 4 th most abundant rock-forming element on Earth. CorusBCSA Video

6 Iron Ore Deposits in Midwest U.S. Most iron ore is mined from open pits, and broken up with explosive charges. It is then shoveled into trucks which transports them to railroad cars or to a nearby processing plant.

7 Iron Ore Processing The larger chunks of rock are broken up by large giant crushers. Then the smaller pieces are broken up finer in a rotating roll mill and ball mill, which are machines that have hardened steel rollers or balls which break up the rock. When the material becomes broken down to fine particles the good iron ore can be separated from the worthless material. This is done with magnetic separators. Then the fine iron ore particles are immersed in a liquid, which allow any small impurities that float to be removed. It sometimes can take about TWO tons of Iron Ore to produce ONE ton of Iron.

8 Coke (Coal) Supplies the heat for the process. Combines with oxygen in the iron ore and liberates the metallic iron. Molten iron absorbs carbon from the coke. Coke is made by baking coal in ovens at 2,000 F to drive off water and impurities.

9 Coal/Coke

10 Limestone Used as a flux to carry away impurities. Keep the impurities at the top of the molten pool so then can be removed in the form of slag.

11 Limestone

12 Taconite

13 Loading Dock

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15 Steel ready for Shipping/Processing

16 Blast Furnace Process Tremendous heat is needed to melt the iron ore, coke, and limestone. The coke burns first, which then melts the iron ore and limestone. The furnace is tapped from the bottom every 3 to 5 hours, furnaces can run for years straight. CorusBCSA Video

17 Blast Furnace Facts The inside of a blast furnace is about 30 feet wide. The entire furnace may be as tall as 250 feet. The inside of the furnace is lined with fire resistant bricks. The slag is on top of the molten iron because it is lighter.

18 Pig Iron Molten Iron at around 2600 F is transferred to a steel making furnace. The hot metal remains in the molten state and never solidifies. Molten Iron is poured from bottle cars into long molds, eventually this material will be made into steel or cast iron.

19 Steel Making Flow Chart

20 Steel Making Furnaces Basic Oxygen Furnace Electric Arc Furnace Open-Hearth Furnace

21 Basic Oxygen Furnace Steel Barrel lined with refractory material. Barrel pivots on a shaft and tips to one side so the molten scrap material molten iron from the blast furnace can be poured into it. An oxygen lance pipe is lowered to within 6 feet of the molten pool of metal. After locking the pipe in place, the mixture is ignited, and a high pressure stream of oxygen hits the mixture at supersonic speeds. Lime and Fluorspar are added to combine with carbon and other impurities to form slag. After reaching temperature of about 3000 F and removing the oxygen lance the slag is removed and the molten steel is poured into a large ladle which transports it to the ingot center. Used to make general steel

22 Electric Arc Furnace Tea-kettle shaped with a spout on one end. The steel outer shell of the furnace is lined with heat resistant refractory bricks The roof pivots and swings aside so the raw material can be loaded into the furnace. Three retractable graphite electrodes 2 feet in diameter and 24 feet long extend up the roof of the furnace. When the electrodes are charged the electricity jumps from the electrode to the metal in a spectacular display of light and immense roar. Similar to lightning and thunder. Limestone is added as a fluxing agent. The batch may mix for a period of 3 to 7 hours depending on the steel composition. After reaching temperature of about 3000 F the slag is removed and the molten steel is poured into a large ladle which transports it to the ingot center. Used to make specialty steels, such as stainless steel, tool steel, and high-alloy steel.

23 Processing The Ingots Teeming Pouring molten steel into the ingot molds. Stripping Removing the ingots from the ingot molds. Soaking Heating the ingots to obtain more uniform properties in the metal.

24 Rolling Mill Series of rollers that squeezes the red hot ingot down into smaller shapes and sizes. Rolling also improves the mechanical properties in the steel as well.

25 Rolling Mill Products Slabs Plates, Coil Strips, Pipes. Blooms I-beams, Structural Items. Billets Bars, Rounds, Wire.

26 Continuous Casting Slabs, Blooms, and Billets can be made in one continuous and uninterrupted operation instead of pouring them into ingot molds.

27 Cast Iron Made from Pig Iron and Scrap Steel. Used to be made in a Cupola Furnace which is similar to a Blast Furnace. Made now mostly in an Electric Induction Furnace because of the pollution problem.

28 Mini Mills Use Electric Arc Furnaces. Rely on scrap steel instead of iron ore. Smaller amounts of steel can be processed to serve smaller local markets. Specific alloys steels can be produced.

29 Steel Production CRUDE STEEL PRODUCTION (million tons) (f) %Chang e 2002/200 3 EU Other Europe Former CIS North America South America Africa Middle East China Japan Other Asia Oceania Total Source: IISI 2002/3, MEPS Estimate/Forecast 2002/3

30 The End