Hot Rolled vs Cold Rolled Steel: Key Differences and How to Choose

Hot rolled 그리고 cold rolled steel are produced from the same steel, but the processes give them different surfaces, tolerances, strengths and prices. This article explains the differences and helps you choose between SPHC hot rolled steel sheet and cold rolled coil for your application.

How Hot Rolling Works

Hot rolling reheats a steel slab above its recrystallization temperature (typically above 900 °C) and rolls it down to the required thickness. The result is a plate or coil with a dark mill-scale surface, slightly rounded edges and relaxed dimensional tolerances. Hot rolled steel is cheaper, thicker (usually 1.5 mm and above) and more forgiving for welding and heavy fabrication. The JIS grade is SPHC (그냥 G3131) and the GB grade is Q235B (GB/T 700).

How Cold Rolling Works

Cold rolling takes hot rolled pickled coil and rolls it again at room temperature. The steel work-hardens, becoming stronger and harder, with a smooth bright surface and tight thickness tolerances. Cold rolled coil (the JIS grade SPCC, JIS G3141) is used for exposed panels, cabinets, precision pressings and as the substrate for electro-galvanizing and painting.

Key Differences

Which One Should You Choose?

• Choose hot rolled for structural work, 용접, heavy fabrication and anything thicker than 3 mm — see our Q235B hot rolled steel plate.
• Choose cold rolled for exposed, painted or precision parts under 3 mm.
• For galvanized sheet, hot-dip galvanizing usually starts from cold rolled or pickled hot rolled substrate.
• For coil supply in large tonnage, 우리의 Q235 carbon steel coil range covers common structural grades.

A quick rule: if the part is going to be painted or visible, or needs tight dimensions, go cold rolled; if it is going to be welded into a frame, go hot rolled. Surface preparation (pickling, shot blasting, painting) is available on both product lines.