Thread: Cold rolled steel

as soon as I posted thread, Morrisman's thread on same subject popped up.

Dave

Hi Dave,
I saw the thread title and thought "oh god here we go again......"

But i'm glad it is not so.

If you looking for round bar i have always found Herzogs (Fyshwick store) to have plenty in stock, big and small sizes, and are far cheaper than metalmart. I'm not sure about onesteel in Hume.

Cheers,
Ew

Dear all

Have now done the searching and reading that I should have done before my original post. I conclude that I am not going to worry too much whether I am using hot or cold roll. I'm don't purchase enough new stuff. nearly all my projects use indeterminate stuff from my extensive scrap pile of 30 years. Occasionally I do have to worry about strength or hardening ability or weldability but will cross those bridges when I come to them.

Dave

Originally Posted by YarrD

Dear all

US fellas on YouTube often refer to cold roll steel. What is the difference with hot rolled(?) steel and how can I tell which is which.

Dave

Cold rolled / "Bright": They start with a bar of stock that has been hot rolled to be near the required size, cool it, pickle it and pass it through a series of rollers whilst the metal is at room temperature. The process leaves the metal with quite a nice, shiny finish and relatively dimensionally accurate stock. Its generally used in basic machined parts because its got a nice blend of low price and some machineability.

Hot rolled / "black": They start with the stock at high temperatures and roll it into shape while its still soft, then it is allowed to cool. It forms a scale that is harder than the inner metal and leaves it with a black appearance. The metal has slightl different alloying elements than cold rolled stock (though the accepted ranges do overlap, so they are rather similar). Its dimensionally inaccurate, the least accurate way to buy new stock that I can think of. Its usually not particularly straight and definately not round, due to distortions in the cooling process. It gets used in more welding / bending / general fabrication sorts of jobs because its very cheap (the manufacutring process doesnt use expensive machines and it can all be done straight out of the steelmaking process). If youre really pedantic about your work, you should be removing the scale before welding to keep impurities out, but for the sort of work you would typically use it in (non critical stuff), it can be used as is.

The last guy that asked questions relating to this was actually doing it to stir the pot, which ruined what could have been an interesting discussion on metalurgy of metals that we frequently use. Instead it turned into a bizzare display of holier than thou behaviour that didnt make a whole lot of sense to me.