MuddyJeep05

Whats the Difference between them?
What would be better for building bumpers?


I have been playing around in the garage welding and I have had a few buddies over who have built bumpers themselves trying to teach me how to do it. I have a stick welder that the previous owner of the house left behind when I moved in. Would this be ok to use to make a bumper or should I look at borrowing another welder from someone else? I am going to try my hand at making a rear bumper first just a square with 2 tow hook brakets. Just to see how it turns out.

Thanks
Phil

FASTMETAL

you can bend hot rolled much easier than cold rolled steel,, tig welding on hot rolled sux,,

chrisdm4

cold rolled is harder and has a closer tolerances. For a bumper I do not think it would matter what you use.

Howler_GT

I work with BOTH everyday.

I can tell you this:

For your application, go with hot-rolled.
Easier to acquire and alot cheaper in the cost department.

Besides, just starting out with welding, you may need some "extra" material.

It can take a bit to "dial-in" for a smooth even weld bead with stick. But it can be done.

ADVICE: Pick up an auto-darkening helmet. Harbor Freight has them rather cheap. Once you use one, you will NEVER want to go back to the "pain-in-the-neck" (literally) regular helmet.

jd4x426

x2 on the hot rolled and iwould recomend practicing with the stick welder first they can be a bit tricky if youve never done it before so find some scrap metal and try it out first then build the bumper

never quit

My preference would be cold rolled or cold drawn. For the same grade, cold working would increase the strength and also result in improved dimensional tolerances over hot rolled product.

Never Quit

93gc40

Hot Rolled easier to work, softer and cheaper, Cold rolled harder to work, stronger and more expensive. I'd use HR for a bumper if I had a choice. The extra strength of CR is not worth the extra cost. If you ever hit something hard enough to test the strength of either type of steel, the unibody will be so twisted it wont matter.

5-90

"Hot rolled" is, of course, rolled hot. This reduces work-hardening (almost eliminates it, actually,) and provides the material in a "soft" state making it easier to work (bend, machine, drill, form, ...)

"Cold rolled" is rolled cold (<300*F, IIRC,) which has the effect of work-hardening the material. Also, since it's run through the rollers so much colder (and therefore expanded much less,) it tends to be of much closer tolerances.

Since hot rolled steel is left to cool in open air, it will have a layer of scale on the surface that will need to be removed before it can be welded - use a wire wheel or a coarse flap disc/wheel for this (the scale is oxidised iron, and will interfere with getting a good weld. This is why TIGing HRS can be a problem.)

Given that you aren't previously aware of the difference, it can be presumed that you are fairly new at this - I would suggest getting HRS for your first few projects. You'll find it more forgiving to work with, and more tolerant of noobs (get four or five projects done effectively with HRS, and you'll probably be ready to work with CRS and not waste too much of it.)

HRS and CRS can usually be visually identified, since the mill doesn't often remove the scale layer - that way they can tell which is which as well. Removing the scale from HRS isn't difficult at all, and it actually helps protect the metal from further atmospheric corrosion (read: "shelf rust") anyhow. I keep a lot of HRS stock around here for small projects where strength is "important" but not "critical" - it works well and quickly, and lets me get a quick ersatz tool made if I should suddenly need one (and it's easier to store, since the scale helps protect it from rusting. I do have a small selection of HRS around, but I check it for rust about monthly, and coat it with WD-40 [which is what the stuff was invented for anyhow] after checking.)

Schmoozer

The name comes from the manufacturing processing, hot rolled metal is worked/shaped while hot (makes sense) and then cooled which lets the molecules sort of get in line with the shape before it cools down. This results in the material being more ductile. Similarly annealing something that is cold rolled (heating it and letting it cool slowly) will also make the metal more ductile.

Cold forming, again, is worked/shaped while cold, this means the molecules are 'every which way' (thats a technical term ) making the metal overall harder to bend. Its the same idea as work-hardening a material. This is more difficult to do and hence makes the product more expensive.

I just saw 5-90 already said this, oh well.

a1racer

is it a stick arc type welder or tig welder. for the stick type make sure you don't cheap out on the wall size or you will burn through it easily.and do you have a grinder sawall what kinda setup for fab work do you have.

CRoading

Hot Rolled is the better option since you're just starting your way on making your own rear bumper...
This would make your work easier and cheaper...

MuddyJeep05

I have the stick arc welder. Also yes I d have grinders and a sawsall, band saw ect... That I will have acess to.

COSXJFAN

Since you have the stick type arc welder at your disposal, I'd say just practice, practice, practice. You can lay down some really nice beads with them, it just takes a little more Jedi skills than a M.I.G. does, that's all. One thing to feel good about, once you get savvy with the stick welder, you'll be a ninja with a M.I.G. welder for sure!! As was mentioned earlier, get an auto helmet, especially since your using a stick welder. The arc is more difficult to get started with electrodes, and being able to see your work before you strike the arc is extremely helpful for bead placement. HTH!!

a1racer

Yup I learned on a arc machine and if you can swing the loot the auto darkening helmet will help improve your starts about 100 precent. And the bast thing you can do is go to the local metal yard and get some scraps to practise on.

mcnslayer

thanks for the info this will really help in the future