It is difficult to determine which specific industries use S235J0 and DX51 steel grades without further information. However, these steel grades are commonly used in construction and manufacturing industries due to their desirable properties and cost-effectiveness. S235J0 is a non-alloy structural steel grade with a good weldability and machinability, making it suitable for various construction applications such as building frames, bridges, and offshore structures. DX51 is a galvanized steel grade commonly used in the manufacturing of automotive components, electrical appliances, and construction materials. The cost-effectiveness of these steel grades, coupled with their mechanical and chemical properties, make them attractive options for a wide range of industries.