A process for producing a flexible vulcanized joint between two electric power cables includes the steps of: producing an exposed conductor joint between each end of the two cable ends to be joined; producing an inner semi-conducting layer thereby radially surrounding and covering the exposed conductor joint; winding an insulation tape including an organic peroxide around the inner semi-conducting layer thereby radially surrounding and covering the inner semi-conducting layer; curing the insulation tape to produce an insulation layer; and producing an outer semi-conducting layer thereby radially surrounding and covering the insulation layer. The step of winding the insulation tape around the inner semi-conductor layer is performed under an oxygen-free atmosphere. The present invention also provides a flexible vulcanized joint produced by this process, and an electric power cable including such a joint.