wrought iron ppt.pptx

wrought iron

1. BUILDING CONSTRUCTION AND MATERIALS

2. WROUGHT IRON   I s an  iron alloy  with a very low carbon content in contrast to  steel. It has fibrous inclusions, known as slag. This is what gives it a "grain" resembling wood, which is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile and easily welded . INTRODUCTION Pig iron and cast iron have high carbon content which make them very brittle, but they have a lower melting point than iron or steel. Cast and especially pig iron have excess slag which must be at least partially removed to produce quality wrought iron. Contains carbon hardly 0.15 %

3. Increase in the amount of carbon decreases the melting point of the metal. Carbon exerts the most significant effects on the microstructure and properties of iron products. STEEL CAST IRON WROUGHT IRON

4. MANUFACTURING The wrought iron is almost pure iron. Has laborious and tedious manufacturing process. Four distinct operations are:- Refining Puddling Shingling Rolling . REFINING The pig – iron is melted and a strong current of air is directed over it. Stirred well when current of air is passing over it, thus thoroughly oxidized. Then cast into moulds. Cooled suddenly to make it brittle. Known as refined pig – iron.

5. PUDDLING Conversion of pig – iron into Wrought iron by stirring in a molten state . Carried out in a reverberatory furnace . The refined pig – iron is broken into lumps and is melted in the hearth. The hearth lining acts as an oxidizing agent. other oxidizing agents like hematite ore, oxide of iron etc are added. Subjected to intense heat and strong current. Well stirred by long bars through the working doors . During this process, carbon content and other impurities are oxidized. Slag is removed through slag removal door. Purified iron becomes thick, form white spongy iron balls ; known as puddle balls.. weight – 500 N to 700 N.

6. The metal does not come into direct contact with the fuel. The flame from the fire is reverted or sent back on the metal in the hearth. Grating is provided in combustion chamber to collect ash in the ash pit. Hearth portion has shallow depth and its lining consists of molten slag or rich iron ore . It is supported on steel plates which in turn are supported on dwarf brick walls. The water jackets are provided for circulation of water to cool the furnace. Various doors or openings for fuel feeding, working and slag removal are provided. The roof is given a peculiar shape so that the flames of gas are concentrated on the hearth. REVERBERATORY FURNACE

7. Shingling To remove slag in the puddle balls. Done by forging the balls under a power hammer or by passing the balls through squeezing machine. also helps in binding or welding the different particles of puddle balls. end material known as bloom and is still in red hot condition. Rolling The bloom is passed through grooved rollers and flat bars 4 m x 100mm x 25mm are obtained. Bars of poor quality. To improve quality bars are tied together by wires and they are heated and rolled again. This process may be repeated several times to get wrought iron of desired quality.

8. ASTON’S PROCESS Developed by James Aston in 1925. Mechanical process, quick and economical. The molten steel from Bessemer converter is poured into liquid slag. Temperature of- molten steel – 1500 o C liquid slag – 1200 o C Molten steel contains large amount of dissolved gases, liberated when it strikes the slag. Molten steel freezes, spongy mass having temperature of 1370 o C is formed. The spongy mass is given the treatment of shingling and rolling.

9. PROPERTIES Becomes soft at heat and it can be easily forged and welded. Can be used to form temporary magnets, but cannot be magnetized permanently. fuses with difficulty ductile, malleable and tough moderately elastic unaffected by saline water resists corrosion in better way. fresh fracture shows clear bluish color melting point is about 1500 C specific gravity is about 7.8 ultimate compressive strength about 200N/mm 2 ultimate tensile strength about 400 N/mm 2

10. DEFECTS Defect can either be cold short or red short Cold Short:- very brittle when it is cold cracks if bent can be worked at high temperature defect occurs when phosphorous in excess quantity . Red Short:- possesses sufficient tenacity when cold cracks when bent or finished at red heat useless for welding process defect occurs when sulphur is present in excess quantity.

11. USES has been replaced by mild steel. produced to a very small extent. used where a tough material is required. presently used for -rivets , chains, ornamental iron work, -railway couplings, water and steam -pipes, bolts and nuts, roofing sheets

12. Eiffel Tower, Champs du Mars, Paris. 1889. Grew from Eiffel’s bridge-building expertise. Was world’s tallest structure for 40 years. 300 m tower built of puddled iron. The “arch” shape at the bottom is purely decorative.