Development of New Process and Product Monitoring Technologies for the Manufacturing of High Value Alloy Steels for Use in Critical Applications

Abstract

During the mid-1700s, Benjamin Huntsman developed the crucible steelmaking process to improve the performance of steels used for making clock springs. This can be considered the beginning of the development of clean steels, which have certain requirements regarding inclusion chemistry and content arising from the potentially deleterious impacts that inclusions can have on steel properties. Today, steelmakers continue to produce clean steels for applications such as aerospace and bearings using tight control of existing process parameters, as environmental and economic drivers have pushed performance requirements. The current project introduced new methods of linking process parameters and product quality at the program sponsor, Liberty Speciality Steels, in three areas: (1) Quantification of the inclusion flotation process has traditionally relied heavily on the operator's experience, and so a great effort has been expended on monitoring ladle bubbling, with an aim to quantify bubbling so that it can be even more closely and consistently controlled. (2) Many methods of inclusion assessment have been established by producers and international bodies, all with their own benefits and limitations. However, emerging technologies, such as x-ray computed tomography, might offer more information than current techniques. (3) Although the common practice of procedural slag chemistry control has historically been used to great effect, analysis of through-process slag chemistry using x-ray fluorescence spectroscopy would allow slag mixes to achieve the best chemistry and slag additions to respond to actual slag chemistry in the ladle. Ultimately, the project aim is to assess the viability of applying these technologies to a speciality steelmaking process with the hope of allowing further process developments to improve final product properties.