Internal plugging device for pipe welding

According to the internal plugging device for pipe welding, a flame-retardant sleeve is positioned and sleeved on the outer circumferential wall of a tray body, a flexible high-temperature-resistant fireproof sleeve with a U-shaped section is arranged on the tray body, and the flexible high-temperature-resistant fireproof sleeve wraps the flame-retardant sleeve and abuts against the inner wall ofa welding pipe; the tray body is provided with a protective gas supply device with the two ends communicated, the gas outlet end of the protective gas supply device faces the welding position of the welding pipe, and a protective gas supply pipe used for supplying gas to the welding position of the welding pipe is arranged inside the control end of the protective gas supply device located at the pipe opening of the welding pipe. The tray provides a good high-temperature-resistant sealing condition for pipe plugging, the protective gas supply device arranged on the tray body is connected with the protective gas supply