Welding method capable of preventing weld joint from cracking

The welding method comprises the following specific welding steps that firstly, in the carbon arc gouging back gouging process and during welding of an outer opening, a cylinder continues to be heated, and the temperature of the cylinder is not lower than the preheating temperature; secondly, welding current is properly reduced, the welding speed is increased, and pear-shaped welding seams are avoided; thirdly, multiple welding is adopted for each layer, and low-melting-point eutectic aggregation is avoided; wherein the first step is completed through cooperation of a welding heating machine, and the welding heating machine comprises a supporting device and a heating device; the two supporting devices are used for limiting the position of the workpiece and comprise bottom plates, and the bottom plates are provided with bearing assemblies making contact with the workpiece and driving assemblies for driving the bearing assemblies to move; the heating device is used for continuously heating the workpiece in the