A name commonly applied to certain tool steel alloys. The most common of these are the 18-4-1 steels, with a chemical composition of 18% tungsten, 4% chromium, and 1 % vanadium. Molybdenum high speed steels are another type. They are usually composed of approximately 9% molybdenum, 4% chromium, 1.6% tungsten, and 1 % vanadium. High-speed steels usually contain from .75 to 30% carbon, and for this reason are difficult to weld by processes other than arc welding.