The difference in temperature between two points which are a stated unit distance apart. For example, if welding has been performed at a point in a steel plate and the weld is at a temperature of 1500°C (2732°F), and a point in the plate 25 mm (1 in.) away from the weld is at 100°C (212°F), then the temperature gradient is calculated as 1500 -100 = 1400°C per 25 mm, which is a gradient of 56°C/mm (2732 -212 = 2520°F per in., which is a gradient of 2.52°F/0.001 in.). Reference: George E. Linnert, Welding Metallurgy, Vol. 1, 4th Edition. Miami, Florida: American Welding Society, 1994.