View Full Version : HRS vs. CRS
03-19-2002, 11:58 AM
I'm looking for some education here:
How does one know when one is looking at cold rolled vs hot rolled steel? I've always assumed that angle stock, or for that matter any structural steel, is hot rolled.
Also if it appeared to have a rust/scale layer (other than out in the weather too long) then it's HRS, whereas CRS would be cleaner looking. But I'm never sure.
Also, if 'stressproof' is called for, will drill rod work ok?
03-19-2002, 01:01 PM
You know when you put a tool to it.
Hot rolled is a better material by nature
having fewer stresses and better machinability.
As a result, parts have less distortion while machining.
Cold rolled steel is generally trash.
I wouldn't categorize cold-rolled as "trash." The composition of the steel has far, far more to do with the "trashiness" of steel than how it's rolled. In fact, I many better grades of steel are cold-rolled, because the cold-rolling process strengthens the steel and imparts other desirable properties.
Generally, I don't think there is any 100% reliable way to tell the difference. As you note, hot rolled has a surface scale, but that can be difficult to identify if the steel is weathered.
"Stressproof" is not equivalent to drill rod. It's another thing entirely. It's a trade name of LaSalle Steel for 1145 steel that has been manufactured in a certain way. "Fatigueproof" is similar in composition, differing in the the manufacturing process.
Both of them machine very nicely -- a heck of a lot better than drill rod or any of your typical hot- or cold-rolled "mild steel."
Do a web search for "Stressproof" and you should turn up a bunch of information.
03-19-2002, 02:29 PM
My local supplier charges more for CRS than the HRS. From what I've been told, the CRS machines more nicely, however I've used both and frankly with the shallow cuts that I usually make, I don't see any difference. Even the metal vendor's can't tell whether it's CRS or HRS after it's been machined.
BTW, I've used 12L14 and it does machine nicely however it doesn't seem very popular so my supplier doesn't stock too many different sizes. Why is this?
Is 1145 just as nice to machine as the 12L14?
03-19-2002, 02:57 PM
Hot rolled steel is rolled "hot", red hot.
What you get is a material that has few stresses and in the annealed condition.
Machinists don't like to work it because it's DIRTY. How about that used oil slime put on c.r.s.
COLD ROLLED steel is rolled cold which workhardens the surface (good for some applications) but also stresses the same surface.
You take a cut on one side of a piece of c.r.s. 1/4 inch thick, and end up with a potatoe chip (exagerated).
This is not the case with hrs.
Cold rolled steel is ok if you need something that looks nice with minimal machining.
Hot rolled is best when heavy machining is required.
Take a piece of c.r.s. and saw down the center to make a yoke. Your saw cut will spread to 1/8", 1/4" or more.
What you get is a Y shaped part which needs the outside cut to true it up anyway.
May as well get h.r.s. to start, and machine it all over anyway.
Save money in the long run.
Higher price dosen't make better material,
just more expensive.
03-19-2002, 03:39 PM
I use CRS more often because it holds truer in the chuck...Hot rolled is no problem to machine, as long as you cut deeper than the crust on your first cut....
And yes, CRS has stresses because it is cold worked..If you are going to make parralels, use hot rolled because cold rolled will warp as you machine it...I use 1144 not 1145 and it is a stressproof material..
12L14 machines nicely because of the lead...The only difference between 1214 and 12L14 is the added lead....Lead increases machinability, Lead does not do anything else in the material.....Do you notice the difference in smell???
Is Stressproof 1144? Could be...I can never remember if it's 1144 or 1145.
Anyway...I like the finish I get with Fatigueproof (never tried Stressproof, but supposed to be similar) very much. You can't cut it quite as fast as 12L14, but it cuts well (it doesn't "tear" the way drill rod and some mild steel does). I don't care for 12L14 all that much because I find that it rusts really easily. But it sure does cut nicely.
03-19-2002, 05:08 PM
1144 is stressproof..I use a lot of 1144 for making high pressure hydraulic cylinders...It is pretty easy to maintain a 16 RMS finish....But it does work harden semi-easy...Be careful when you drill!!!
03-19-2002, 06:20 PM
Cold finish steel (most isn't rold now) is drawen through a die, lots of stress in it. It will sometimes warp or go cork screw or go egg shape on you, sometimes all three. It is best used for shafting and such where you only have to cross drill it for a pin, cut a keyway or make a short thred on it. It is usually close to size, most of what I get is .0015 or .002 under. Just right for a little oil room in low speed bearings. Hot finish steel is much better for machining after you get past that scale, it don't warp but it is hard on end mills. Pickle it first in salt and vinegar after you degrease it if you can. Can take three four days to pickle but it will get rid of the scale. Also most hot finish steel I get is not very round any more, and it will mot clean up in the lathe to the stated size. I have to buy 15/16" to clean up to 3/4". That said once it in the scrap yard and rusted up you can't tell them apart till you go to turn them. If you buy your steel from a warehouse you should be able to tell by using a rag or scraping it with an old knife or file.
03-19-2002, 07:41 PM
I am partial to 11L17 or 12L14 or even without the lead CRS for most applications. I make parallels out of 41L50 CRS. To remove warp I mill surface light off one side, mill opp surface same - no warp here, go back to orig surface, seating on second surface, works like a charm. Most I have to take off the stock to do this is about .070 at best total stock removal.
I have had warping trouble with Hot rolled as well. The cold rolled idea is just how you work off the surface to remove stress.
I also use quite a bit of 4140 Cold and hot rolled in my shop, seems the cold rolled machines better. I can't really tell the difference after the surface cuts.
Best way to tell cold rolled from Hot rolled in the field when weathered. The hot rolled has the surface scale, the cold rolled does not. I will take a piece of 50 grit sandpaper with me and sand off some rust. If I get to steel immediately, it is cold rolled. If I get a bit of blackened dust and the surface scale shows through better, it is cold rolled. Good about 80% of the time, sand off the rust a bit - do not work too hard or you negate this.
03-19-2002, 11:55 PM
I picked up some Starrett #498 Low Carbon Killed steel off eBay - boy does it machine nice! They have added Sulphur instead of lead. Can't wait to see how it color case hardens.
03-20-2002, 03:05 PM
I don't know what you are making, but I would be cautious if using for a firearm.
Lead and/or sulfur are added to make steel free cutting. They appear as impurities in the metal, and are likely to cause catastrophic failures upon firing. There was a letter or two in HMS a while back detailing this.
Leaded and sulfur steels do not like to be welded either.
03-22-2002, 02:46 AM
I bought it for parts & tool making stock (not cutting edges or guns). As a Canadian - I avoid thinking of making much of anything beyond a scope mount or such in my shop. Our government are already gone stupid on gun control - I don't want to provoke them into taking our knives, forks, and other pointy things from us. I just make tools, parts, steam engines, Hot Air engines, and puzzles ( www.research.ibm.com/BurrPuzzles (http://www.research.ibm.com/BurrPuzzles) ).
03-22-2002, 07:26 AM
I didn't want anyone else thinking about using free machining material for highly stressed parts.
Too bad about the situation up there, but there are plenty of other areas to explore.
Interesting web site.
Seems the HRS I have used generally was what I would call "sticky". It made stringy nasty swarf and left a crappy surface with torn-looking edges on it.
The CRS seemed to be more apt to make chips, and leave a decent surface. Bad CRS seems just as bad, though
Could have been the alloys in question, too.
03-23-2002, 12:28 AM
That is a good point about the free machining stuff being unsuitable for high stress parts - but CRS and HRS should not be used for that either.
03-23-2002, 05:53 AM
Definitely not. However, there are some leaded and free cutting alloys, 41L40, for example which should also not be used.
Any alloy which has L in it is leaded, I do not know what denotes sulphur, but it should also be avoided.
03-23-2002, 09:34 PM
<font face="Verdana, Arial" size="2">Originally posted by Thrud:
I picked up some Starrett #498 Low Carbon Killed steel off eBay -
What is "killed" steel?
03-23-2002, 10:06 PM
The term “killed” indicates that the steel has been sufficiently deoxidized to quiet the molten
metal when poured into the ingot mold. The general practice is to use aluminum ferrosilicon or
manganese as deoxidizing agents. A properly killed steel is more uniform as to analysis and is
comparatively free from aging. However, for the same carbon and manganese content Killed
Steel is harder than Rimmed Steel. In general all steels above 0.25% carbon are killed, also all
forging grades, structural steels from 0.15% to 0.25% carbon and some special steels in the low
carbon range. Most steels below 0.15% carbon are rimmed steel.
03-24-2002, 10:11 PM
The term "killed" as I used it refers to its physical properties - that being very malleable, annealed, and stabilized. For instance, a killed cold rolled sheet is usually used in deep drawing operations such as oil filter cans. If they did no use these "killed" metals in this operation the result is an uneven wall thickness and tearing of the metal from overworking it. The drawing operation (cold working) greatly increases the items strength.
The term used in the context of the metals composition is as Snorman has stated.
Starrett's label on the plastic wrapper says it is a .17% Carbon Fine Grained Killed Steel with Sulphur of forging quality roughly equivelant to an AISI 1117S. Starrett claims it to be 37% better machinability than free machining AISI 1018. It can be carburized to 1/32" deep if held in carburizing salts for 3 hours @ 1700*F or can be case hardened.