?What are black steel pipes used for ?What are black steel pipes Black steel pipes are made of steel that has not been coated with a substrate such as zinc or paint. Since it has a dark color surface that is forms by iron oxide during the manufacturing process, it is called black steel pipe. … ادامه خواندن ورق سیاه چیست؟ کاربردها و ویژگی های ورق سیاه