Cast basalt composite elbows are used too many industrial areas where the abrasive, chemical and hot materials transported and which are commonly lined steel elbows. Cast basalt composite elbow is composed of steel pipe tee, cast basalt pipe and cement mortar concrete. At the same time cement mortar is selected as the filling material and this can make the inside surface of steel pipe in alkali mediums. So the surface of steel pipe generates purifying films These films can prevent being rusted.