Wide gap welding method and welding part

The invention relates to the technical field of welding, and provides a wide gap welding method. The method is used for welding of a gap with the welding width ranging from 5 mm to 9 mm, and the method comprises the steps that a gasket plate with the material the same with that of a part to be welded is additionally welded to the middle of a groove, and the part to be welded is preheated to 210 to230 DEG C; when the temperature of the part to be welded reaches 210 to 230 DEG C, welding is carried out, in the welding process, the part to be welded is subject to heat preservation, the part to be welded is kept at 210 to 230 DEG C, gas metal arc welding is adopted to carry out welding on the two sides of the gasket plate in sequence; after welding is finished, cooling is carried out, when the temperature reduction rate of the welding line is controlled to range from 230 to 500 DEG C/h, in the cooling process, and the welding part is still subject to heat preservation; when the temperature of the welding line is