Alloy steels play a pivotal role in modern society. Their continued development improves the human condition for everyone on earth. Their broad use has resulted in a wide variety of continuing challenges to address economic, manufacturing, and industrial issues. This book contains twenty-three papers covering a wide cross-section of alloy steels and technical problems. Readers interested in solving current manufacturing and application problems will find this issue helpful. The papers contained within cover a wide range of topics by a broad set of authors from across the globe. There are papers covering structure-property relations on various alloys. Other papers discuss the proper processing of alloy steels through the welding, electroslag remelting, and rolling processes. A significant number of the papers cover optimizing the heat treatment of traditional alloys as well as new alloys. There are papers that concentrate on providing real-world performance data on alloy steels, an important but under-studied topic. Of particular interest is a review on the welding of austenitic and duplex stainless steels that gives neophytes and experienced researchers an excellent introduction to the state-of-the-art. This collection of work should be valuable to anyone interested in alloy steels.