from the conferences organized by TANGER Ltd. provisional website
Slab thermal homogenization during reheating in furnace is temperature and retention time dependent. Dissolution of microalloying element like niobium in austenite at soaking temperature is important to achieve desired strength and toughness in final rolled product. Under soaking and low set temperature may not dissolve microalloying elements and on other hand over soaking and higher temperature may lead to austenitic grain growth. In both cases, it affects, strength and toughness of the final product. The optimum temperature and retention time allows micro-allying elements to dissolve in austenite and controls austenite grain growth. These conditions are favorable to achieve both high strength and toughness in the rolled strip.Gleeble 3000 physical simulator was used to conduct trials with combination of various soaking temperatures and time. Prior austenitic grain size and dissolution of micro-alloying was evaluated. To validate experiment and check relevance of experiment with actual rolling during production, laboratory muffle furnace was used and same plant process conditions of soaking temperatures and time were used to simulate actual plant conditions. The results of validation trials were encouraging. Temperature of 1220°C and soaking for 15 and 30 Seconds in Gleeble experiments, had shown similar results, this was deciding factor for the optimizing retention time in reheating furnace. Based on laboratory trials results, plant trials were conducted with reduced furnace retention time of 160 minutes minimum against 170 minutes earlier. The test results of plant trials were satisfactory and meeting specification requirements. Special technique of micro etching was used to reveal prior austenitic grain size.With 10 minutes reduction in retention time for group of steel grade, around 6% more time will be available for rolling, contributing to increment in production and financial benefits.Keywords: Retention time, dissolution of micro-alloying elements, Austenite grain size
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