Process Metallurgy & Product Applications
Cleveland-Cliffs upgraded two walking beam furnaces at its Burns Harbor plate mill to extend the working life of the components and reduce maintenance costs. This article presents the engineering development process for the casting of newly designed protective supports for the refractory on the extractor fingers. Castings were produced from a tailored high-temperature-resistant alloy. Heat transfer constraints caused by geometry and thermal expansion were calculated, as well as stresses in specific areas of the castings. Solidification integrity was confirmed after a series of finite element analysis simulations based on the geometry and alloy constraints. Surface quality, internal integrity and microstructure guaranteed the properties.
Providing a balance of strength and toughness, high-strength line pipe steels (X70) with heavier gauges are in demand. With increased thickness comes challenges to these properties related to maintaining ideal thermomechanical controlled process schedules. Here, results of a trial that produced X70 helical welded line pipes with a gauge of 25 mm are presented. Tensile tests, drop-weight tear tests and Charpy tests are reviewed. The microstructure is revealed using Nital and LePera etching and viewed with optical microscopy and scanning electron microscopy. Through these analyses, performance of the line pipe is established.
Free cutting steels are used for manufacturing high-precision components that demand extensive machining for intricacy. Processing of free cutting steels involves deoxidation by various deoxidizers such as Al, Zr, Si and Ti that form abrasive oxides which impair machinability affecting final component quality and high tool wear. At JSW Steel Ltd., the improvement in the machinability of these free cutting steels is aided through various process improvisations such as modified deoxidation process, rare earth additions and oxygen control. Effect of the process modifications on aspect ratio of MnS inclusions, hard oxide contents, chip formation characteristics and component roughness are discussed in this article.
The New Bar Mill at Tata Steel produces Tata Tiscon branded rebars for the Indian market. It is the least cost producer of rebars in Tata Steel. In FY’22 a new grade, 550SD, was introduced in the new bar mill’s product portfolio, having higher strength and ductility in accordance with the current demands of the Indian market. This paper shows how the high quality rejections in this grade were reduced by improvement of CpK of this grade of rebars, thereby leading to savings of more than INR 1 Cr, along with better quality control.