Welded are cheaper, but at the same time less durable and reliable. Direct welded products are produced from sheet steel by turning the workpiece into the cylinder and fixing the seam by electric arc welding. The second method is that the steel tape on special right equipment is curled up in a spiral into the tube and is fixed with welding. The price of this product is affected by the cost of metal, the method of production, the high cost of equipment.
