The Differences between Hot Rolled and Cold Rolled Stainless Steel

Customers often ask us about the differences between hot rolled steel and cold rolled steel. There are some fundamentaldifferences between these two types of metal. These differences relateto the ways these metals are processed at the mill, and not the productspecification or grade.

Hot Rolled Stainless Steel

Hot rolling is amill process which involves rolling the steel at a high temperature (typicallyat a temperature over 1700° F), which is above the steel’s recrystallizationtemperature. When steel is above the recrystallization temperature, it can beshaped and formed easily, and the steel can be made in much larger sizes. Hotrolled steel is typically cheaper than cold rolled steel due to the fact thatit is often manufactured without any delays in the process, and therefore thereheating of the steel is not required (as it is with cold rolled). When thesteel cools off it will shrink slightly thus giving less control on the size andshape of the finished product when compared to cold rolled.

Uses: Hot rolled products like hot rolledsteel bars are used in the welding and construction trades to makerailroad tracks and I-beams, for example. Hot rolled steel is used insituations where precise shapes and tolerances are not required.

Cold Rolled Stainless Steel

Cold rolled steel is essentially hot rolled steel that has had further processing. Thesteel is processed further in cold reduction mills, where the material iscooled (at room temperature) followed by annealing and/or tempers rolling. Thisprocess will produce steel with closer dimensional tolerances and a wider rangeof surface finishes. The term Cold Rolled is mistakenly used on all products,when actually the product name refers to the rolling of flat rolled sheet andcoil products.

When referringto barproducts, the term used is “cold finishing”, which usually consists of cold drawing and/or turning, grinding and polishing. This process results in higheryield points and has four main advantages:

Cold drawing increasesthe yield and tensile strengths, often eliminating further costly thermaltreatments.

Turning gets rid ofsurface imperfections.

Grinding narrows theoriginal size tolerance range.

Polishing improvessurface finish.

All coldproducts provide a superior surface finish, and are superior in tolerance,concentricity, and straightness when compared to hot rolled.

Cold finishedbars are typically harder to work with than hot rolled due to the increasedcarbon content. However, this cannot be said about cold rolled sheet and hotrolled sheet. With these two products, the cold rolled product has low carboncontent and it is typically annealed, making it softer than hot rolled sheet.

Uses: Any project where tolerances, surface condition,concentricity, and straightness are the major factors.

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