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Heat Transfer Modelling and Mechanical Properties Of Wide-Gap Thermite Rail Welds

Mohassel, Abbas | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43873 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi, Amir Hossain; Davami, Parviz
  7. Abstract:
  8. Wide-gap aluminothermic rail welds with root opening of 60 mm were produced using plain carbon steel rail and non-alloy aluminothermic charge. Such process can repair defective rails, each with only one wide-gap weld instead of using a relatively long plug rail and two standard welds which reduces number of welds in railways and cause saving in money. Required equipments including metallic and sand molds, crucible and self-tapping thimble were designed. Mechanical properties and micro-structure of rail welds and corresponding heat affected zones as well as impact energies and fracture toughnesses of welds were investigated. Wide-gap aluminothermic rail welds exhibited 98% and 95% of yield strength and tensile strength of the rail respectively. Failure also happened in the weld center for a tensile specimen that included both weld and HAZ of weldment. Ductile-brittle transformation temperature for wide-gap aluminothermic rail welds was about 120oC. Fracture toughness of wide-gap aluminothermic welds was 81% that of reported for carbon steel rails and 92% that of reported for narrow-gap type welds. EDS analyses revealed existence of alumina and iron oxide particles in weld metal. Simulation results showed that in low pouring temperatures and in low initial rail surface temperatures, amount of reduction in melt penetration increases with a definite drop in pouring temperature and in initial rail surface temperature respectively but in low gap size, amount of reduction in melt penetration decreases with a certain decrease in gap size
  9. Keywords:
  10. Modeling ; Heat Transfer ; Aluminothermic Reduction ; Welding ; Wide Gap ; Steel Rail ; Thermite Weld

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