Factors Resulting in Shape Defect of Steel Billets and Strategies for Improvement on Processing Control

• Main Authors: chih-wen shih, 史智文
• Other Authors: 沈君洋
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/18105743931257871210

碩士 === 國立中興大學 === 機械工程學系所 === 100 === Rhomboidity is also called off-square. If it is serious, the billet will have diagonal crack in the interior, or crack in the corner accompanying with concave surface. Also, it would cause inconvenience in pushing billet in heating furnace and result in difficulty on biting billet between rollers. Thus reducing rhomboidity of billet is an important subject for increasing production. In this work, firstly, the effect of composition of [C] 、 [S] and [Mn] in molten steel on rhomboidity was investigated the composition and improving steel-making process, the defect was removed. Then using the orthogonal test, it was found that the most important factor on rhomboidity is casting speed, The acquired data that analyzed based on statistics. Secondly, the influence induced by continuous casting machine was considered. In the first cooling zone, the temperatures of old and new copper tubes were measured. In doing so, uneven heat removing due to worn copper tubes can be investigated. After excluding the factors in the fist cooling zone, but still have rhomboidity problem, in the secondary cooling zone an inspection of wearing at the bottom of the copper tubes and the foot roller is required. This can determine whether there is a deformation or and improper calibration of the arc. The flowrate of spray nozzle of secondary cooling water and its pressure also need to be checked .Since they might cause uneven cooling and eventually result in rhomboidity of billet.