Welding Journal

Grade 91 steel was first codified in 1983 as Code Case 1943 for tubing. Additional code cases were adopted in 1986 for seamless pipe, forged pipe, forgings, and plate, followed by a code case in 1995 for castings. The widespread use of Grade 91 steel since the late 1990s coincided with the combined cycle boom in the United States and a worldwide supercritical coal-fired plant build-out that involved the installation of over 1000 miles of pipe and required hundreds of thousands of welds.

The worldwide supply c..