the tendency of steel to form cracks during hot pressure treatment, such as forging, stamping, and rolling, in the temperature range corresponding to red or yellow heat (850°-1150°C).
Red-shortness results mainly from the presence of a number of impurities (such as copper and sulfur) on the metal granule boundaries. Local accumulations of structurally free copper sometimes form on the surface layer of steel, which contains more than 0.4-0.5 percent copper. As a result, surface ruptures and cracks may occur upon forming. Red-shortness is also observed in steel with a high sulfur content and low manganese content. In this case, sulfur is present in the steel not in the form of relatively refractory manganese sulfide, MnS, but rather in the form of ferrous sulfide, FeS, which forms a eutectic with the iron located on the granule boundaries. At 988°C this eutectic melts, which destroys the bond between the granules and leads to the appearance of cracks upon forming. Elements such as aluminum, titanium, and zirconium, which form refractory sulfides, are introduced to eliminate red-shortness or to reduce its undesirable effects. The concentration of copper at the granule boundaries may be prevented to a certain extent by alloying with nickel, molybdenum, and boron.