The sensitivities of cold crack and SRC of boiler tube of 9Cr-1Mo steel with 8mm thickness which was annealed are studied. This steel can be welding without preheating as t8/5 of the steel is less than 13s. A few of figures and tables for choosing preheat temperatures in other conditions are drawn. The toughness and hardness of simulating coarse grain zone are tested with various temper parameters. The effect of temper parameters being chosen on the aging property of high temperature is determined using lad...