Steel Temperatures – Hot Rolled, Cold Rolled, and Cold Drawn
As we mentioned in a recent post, ordering metal fabrications can be complicated. There are the obvious elements such as shape, dimensions, and material used. But even if you know the material you want to use, there are different versions of that as well.
For example, if you need steel, there’s 1008 steels, 1010 steel, with low carbon making it relatively soft and malleable; 1045 with medium carbon making it kind of hard, still machinable and weldable, and 1070 extremely hard and brittle like glass, used for knives and cutting edges.
On top of that, there’s the method used for producing and forming the steel. Not to be confused with steel grade or specs, steel processing offers two options: hot rolled and cold rolled.
Heat, of course, is used in all steel manufacturing. Hot rolling and cold rolling simply refer to how it’s processed at the end. To know which type of steel you need, you should first understand the differences.
Hot rolling involves processing steel at a temperature above its recrystallization level, which is typically 1000° F. This allows it to be formed more easily, and it’s one less step than cold rolling, which means it’s faster.
All in all, hot rolling is cheaper, which makes it great for high quantity production.
However, the finish of hot rolled steel is scaly, rather than smooth. As hot rolled steel cools, it will shrink non-uniformly. This can be remedied through grinding, pickling, or sand-blasting. Still, it lacks the strength and density of cold rolled steel
Hot rolled steel is typically used for sheet metal, automotive frames, and rail tracks, where high-quantity and low-cost are the priority, and a clean external finish isn’t needed.
Cold rolling isn’t an alternative to hot rolling as much as it’s an additional step. Also, the term cold is a little deceptive here, as it doesn’t utilize freezing temperatures. Rather, it’s performed around room temperature, which is well below the steel’s recrystallization point.
Cold rolling hardens and strengthens steel while improving the surface’s appearance, leading to a 20% increase in strength and a smoother finish. Because the steel isn’t as hot when it’s being rolled, it requires more passes to attain the right shape and thickness. This takes longer, and therefore costs more.
Also, because it’s less malleable than hot rolled steel, cold rolled steel is limited to certain shapes: round, square, or flat.
Ultimately, it’s best used when strength, aesthetics, and visual appeal is needed. This includes home appliances, furniture, bars, rods, etc.
Cold Drawn Steel
A term you might see pop up when looking at wire rings and tube bending production is cold drawn steel. This is a technique used in the production of steel extruded products like seamless tube and wire called “long products”. The billet steel is extruded as a rod but then drawn (or pulled) through a die to attain the necessary shape. Steel used in the cold drawn process may have been hot-rolled or cold-rolled beforehand but is usually hot rolled initially.
More complex shapes may need to be drawn multiple times.
Knowing What You Need
As we mentioned before, this can all be a lot to figure out and process. The best way to determine your needs is to speak with someone who knows metal fabrication. We happen to know quite a bit. At Ever-Roll, we’ve been creating wire rings, burner rings, fabricated metal tubing, and more since 1945.
Whether you need a quote, or you’d just like to ask a few preliminary questions, we’re here for you. Contact us today!
bent on perfection.
bent on perfection.