Combined external casement window

The invention provides a combined external casement window, and relates to the technical field of doors and windows. The window comprises a window sash, a reversing frame, a window frame and an auxiliary steel frame; the auxiliary steel frame is used for being fixedly installed in an opening of the window, and the window frame can be installed on the auxiliary steel frame in a detachable mode. The window sash comprises a line-pressing frame, a ram fan, a first drainage clamping piece and accommodating glass, the accommodating glass is clamped in the line-pressing frame, and the first drainage clamping piece is hollow and penetrates through the ram fan. The reversing frame comprises a bearing frame, a connecting frame and a second drainage clamping piece, the bearing frame is fixedly connected to the connecting frame, the connecting frame is connected to one end of the window frame in a detachable mode, and the bearing frame is in lap joint with the other end of the window frame. The bearing frame is internall