Hot Rolled vs. Cold Rolled steel

**GeneStoner** · 05-06-2005, 03:44 PM

What is the difference between Hot and Cold rolled steel?

**Mike W** · 05-06-2005, 04:01 PM

There is a recent post about that. Hot rolled has the mill scale on it. Cold has a smooth finish and more precise dimensions. It will also tend to warp like crazy due to internal stresses if you try to machine it.

**MadMax** · 05-06-2005, 04:09 PM

Cold rolled is typically harder, and hot rolled is a bit more malleable. I have found cold rolled easier to weld. Also, cold rolled is a bit better structurally.

-Max

**TOMWELDS** · 05-06-2005, 09:05 PM

Originally Posted by MadMax

Cold rolled is typically harder, and hot rolled is a bit more malleable. I have found cold rolled easier to weld. Also, cold rolled is a bit better structurally.

-Max

Max, i think its the other way around. Cold rolled is easier to machine but i find it rust a hundred times more than HR. Try turning HR on a lathe and you'll see what i mean.

**MadMax** · 05-06-2005, 09:27 PM

Originally Posted by TOMWELDS

Max, i think its the other way around. Cold rolled is easier to machine but i find it rust a hundred times more than HR. Try turning HR on a lathe and you'll see what i mean.

I know

. But see which one is easier to form (ie fender, gastank etc.) Hot rolled is 'softer' which would give it worse machining propertys, but make it more malleable. As far as rust, I don't know, but it would make sense that Coldrolled rusts easier, since it has NO protection.

-Max

**TOMWELDS** · 05-06-2005, 09:35 PM

I'll try this tomorrow. I used to work in a factory were all we did was form CRS in punch press's. But then again we were after a good finish too, which HR wouldnt give us.

**glockdoc** · 05-07-2005, 10:49 PM

Doesn't the cold rolling process work harden the steel making it harder/stronger.

**MAC702** · 05-08-2005, 12:13 AM

Hot rolled product is heated and rolled at high temperatures to impart the shape, chemical and mechanical properties required in the finished item. Cold rolled products are rolled at low or room temperatures. For example, hot rolling on a continuous strip mill usually begins at about 2200 degrees F. and is completed above 1300 degrees F. In cold rolling, the product is not heated immediately prior to rolling although the temperature of the steel will rise due to the frictional effects of rolling so the finished product may have a temperature of 250 to 450 degrees F.

There are 4 principal hot rolled finished flat products: bars, plate, hot rolled strip and hot rolled sheet. Dimensions, particularily thickness and width, are the principle bases of classification. There are also 4 principal cold finished flat rolled products: flat bars, cold rolled strip, cold rolled sheet and black plate. The latter is the product which is the starting material to manufacture tin plate which is used for food packaging and beverage containers. Galvanized products can be manufactured from either hot or cold rolled strip and sheet.

Most steel products are the result of hot rolling. The difference between hot rolled steel and cold rolled steel is the mechanical and chemical properties imparted to the steel. This in turn depends on the customer's application for the steel and what properties they want in the product they are buying.

Rails, structurals, concrete reinforcing bars, wire rod, plates, and sheet and strip are all examples of hot rolled products. The plates, sheet and strip products could be used to manufacture pipes and tubes, construction materials (such as steel building cladding and decking) and body panels and stampings for the appliance and automotive industries. Wire, sheet and strip are examples of products that can be cold rolled. Wire is often used to manufacture cold formed or cold headed fasteners (eg. screws, bolts) while cold rolled sheet and strip are increasingly being demanded by the appliance and automotive industry for exterior applications due to their superior surface finish particularily as galvanized outer body panels on automobiles.

**TOMWELDS** · 05-08-2005, 12:24 AM

Amen........

**GeneStoner** · 05-08-2005, 02:53 PM

So, could it be said that Hot-Rolled steel is also "Heat Treated?," thereby relaxing the piece into a stronger item in it's post-treated form?

**TOMWELDS** · 05-08-2005, 03:27 PM

I dont know about calling it heat treated as both types go thru a hot stage (obviously), but when they're formed into there final shape, HR is formed Hot and CRS is formed cold. Heat treated is more of a process of changing the metals strength rather than its shape. Hope im making sense.

**Mike W** · 05-08-2005, 03:48 PM

Sounds good to me Tom. You can make a paper clip stronger by unfolding it and then twisting the center part. It will be stiffer until it finally breaks.