A square shaped steel section with a cross-sectional shape and dimensions made by cold bending and high-frequency welding using Q235 hot-rolled or cold-rolled strip or coil as the base material. Hot rolled extra thick walled square tubes not only have increased wall thickness, but also have corner dimensions and edge flatness that reach or even exceed the level of resistance welded cold-formed square tubes. It has good comprehensive mechanical properties, weldability, cold and hot processing performance, and corrosion resistance, and has good low-temperature toughness. The scope of use of square tubes includes construction, machinery manufacturing, steel structure engineering, shipbuilding, solar power generation support, steel structure engineering, power engineering, power plants, agricultural machinery, glass curtain walls, automotive chassis, airports, boiler construction, highway railings, and high load welded structures such as building construction, pressure vessels, oil storage tanks, bridges, power station equipment, and lifting and transportation machinery. The scope of use of square tubes includes construction, machinery manufacturing, steel structure engineering, shipbuilding, solar power generation brackets, steel structure engineering, power engineering, power plants, agricultural machinery, glass curtain walls, automotive chassis, airports, boiler construction, highway guardrails, building construction, pressure vessels, oil storage tanks, bridges, power station equipment, lifting and transportation machinery and other high load welded structures