Cold-rolled versus hot rolled mild steel 1

[Rustang]

What is the advantage of using cold rolled mild steel (round stock) when compared to hot-rolled? Traditionally we've used cold rolled for items like linkages or lightly loaded machined parts; and hot rolled for fabricated parts and weldments. The purchasing guy here says there's no difference except for finish. I disagree but have found little proof to back my arguement!

 

[MadMango]

Ultimate tensile strength and yield are higher for cold-rolled steel over hot-rolled. For average numbers, look at Machery's Handbook, or do some footwork and search a few websites for some metal mills. You can also get material specs from your suppliers, as they should be meeting some ASTM requirements.

HRPO 1020
Elongation ~25%
Ultimate ~55.1kpsi
Yield ~29.7kpsi

CRS 1020
Elongation ~15%
Ultimate ~60.9kpsi
Yield ~50.8kpsi

MadMango
"Probable impossibilities are to be preferred to improbable possibilities."
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[Rustang]

Thanks for the reply. Awhile ago I dug thru the Machinery Handbook but didn't find a chart or anything directly comparing the two from a yield standpoint. I'm going to revisit it.

 

[griffengm]

One factor not shown in the tables is that usually, HR has fewer residual internal stresses after forming than CR. In some assemblies, this can make a big difference in performance.
Then there is the surface finish issue. What kind of roughness can you tolerate?
Then finishing over scale vs bare metal in some applications.

 

[MadMango]

[blue]Rustang[/blue], there is a whole section about this, near the front of the MM called Standard Metals. In my 25th edition book, that starts on page 404. On page 432, Tables 8, 9 and 10 will interest you.

MadMango
"Probable impossibilities are to be preferred to improbable possibilities."
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[dvd]

Another big issue from my viewpoint is that cold drawn rounds have only a negative tolerance versus hot rolled which has plus-or-minus tolerance.

You can get a lot of properties and tolerance information at:

http://www.ryersontull.com/stocklist/RedbookServlet?COM=GetLevel&ID=DATA

 

[CMcF]

The residual stress in cold rolled is mostly in the skin, hence machining a small amount off crs bar, creates bannanas, as my inspection man explained to me.

 

[EdDanzer]

Hot rolled materials will need more material removed from the OD to remove any surface defects that could cause stress cracking. The primary reason to choose hot rolled over cold finished would be for applications where the tolerance of cold finished eliminates machining, or yield and tensile strength requirements.