It should be noted that: 1: the heating temperature should be appropriate enough to cause plastic deformation of steel, and the temperature should not be too high, generally 650-800. 2. The size of the heating point and the distance between points should be appropriate. Under normal circumstances, depending on the thickness of the plate, the arrangement should be uniform, mostly plum-blossom layout. 3. The purpose of water quenching and wood hammer is to accelerate the shrinkage of steel plate fiber group. 4. When heating, the gas welding torch should not sway back and forth, the small flame should be perpendicular to the steel plate, and there should not be too many hot spots, so as not to increase the undue internal stress.