Steel box girder welding device

The utility model belongs to the field of steel box girder welding equipment, and particularly relates to a steel box girder welding device which comprises a portal frame, a walking module, an overhead rail, a driving machine head, a welding machine and a guide rail, a plurality of spray heads are fixed on the gas conveying pipe along the length direction; in the welding process, if spark ignites residual oil liquid on a workpiece during machining, the two driving mechanisms drive the gas conveying pipes to swing towards the outer side correspondingly, then the electromagnetic control valves on the connecting pipes are opened, and fire extinguishing gas stored in the gas storage bottle is conveyed into the four gas conveying pipes through the connecting pipes and the conveying hoses correspondingly; and the gas is sprayed downwards through a plurality of spray heads on the gas conveying pipe, flame on the workpiece is covered for fire extinguishing, the fire is prevented from further spreading, and after the