Steel Making: Lecture open hearth furnace

Steel Making: Lecture open hearth furnace

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  MY: 301 SteelMaking Processes Page 1 of 5 Why Bessemer Process has become Out-dated? This process has got some limitation:  Pig iron of selected composition is required to be charged.  Phosphorus and sulphur (to some extent) can only be oxidized by basic Bessemer process.  The steel contains high content of nitrogen, because air is blown for oxidation. This provides adverse effects and makes the steel unsuitable for most application such as deep drawing purpose. Comparison between Bessemer and Open Hearth Process: S.No Bessemer Process Open Hearth Process 1. Alone scrap iron cannot be used. Alone scrap iron can be used. 2. Refining and finishing requires 10 to 20 minutes. Refining and finishing are completed within 8 to 10 Hours. 3. Operation depends entirely on eye judgment, so that it is very difficult to produce a uniform product. Operation is guided by laboratory analysis, so that it is comparatively possible to produce a uniform product. 4. It produces inferior quality steel associated with blow-holes and inclusion. Open hearth steel is of much superior quality containing lesser blow-holes and inclusion. 5. Carbon is completely eliminated first and so requires large amount of recarburizer and the product become less homogeneous. Carbon is partially removed and requires smaller amount of recarburizers and the product is more homogeneous. 6. Low capital investment. High capital investment. 7. Because of rapidity of the process, the control of different operation is rather difficult and careful working is necessitated. Operation is comparatively easy and finishing up to the desired analysis is feasible.
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  MY: 301 SteelMaking Processes Page 2 of 5 Open Hearth Steel Making Process or Furnace (Siemens furnace):  Introduction  Working Procedure  Construction of the Furnace INTRODUCTION TO OPEN HEARTH PROCESS:
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  MY: 301 SteelMaking Processes Page 3 of 5 Figure: Schematic arrangement of an early type of Siemens furnace with about a 4.5 metric ton (5 net ton) capacity. A. gas and air enter B. pre-heated chamber C. molten pig iron D. hearth E. heating chamber (cold) F. gas and air exit. Working Procedure Steps: The process is divided into four steps. i) Fettling.
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  MY: 301 SteelMaking Processes Page 4 of 5 ii) Charging. iii) Melting. iv) Refining. v) Tapping
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  MY: 301 SteelMaking Processes Page 5 of 5 i) Fettling:  The furnace lining gets eroded because of the action of the slag and/or metal, particularly at the slag-metal interface line.  It is repaired after every heat this is called fettling.  It is to be done to improve the furnace life.  Earlier it was done manually but now fettling machine do the job very efficiently.  Granular material of the same composition as that of the furnace lining is used for that purpose.