New possible replacement alloy for 4130 tubing:

[Rex Schimmer]

I was reading a "materials" article in "Race Tech" mag and ran across a new steel alloy made by Swedish steel manufacture SSAB and it is called Docol. Properties are very similar to  4130 , 4-5 percent stronger, but the real kicker is that it does not get brittle in the heat affected zone, so no post welding treatment required. Sounds pretty neat. It looks like it will be imported to the US by AED Motorsports products. http://www.aedmotorsport.com/blog/article/docol-r8-tube. It appears that the SFI has already approved it for roll cage applications.

Rex

[dw230]

The Mormon Missile streamliner is constructed of Docol.

DW

[SteveM]

I just checked out the specs on the DOCOL tubing.   

That's a pretty sophisticated material (Dual-Phase HSLA (high strength low alloy)). 

This kind of material has been used recently in OEM auto manufacturing.  It's not just a general purpose steel, this stuff has been specifically engineered and developed for the auto industry.  HSLA steels are very formable, while retaining their high strength.

It's nice to see more advanced material science / metallurgy being put to use in the land speed racing world.  It's not just for the OEM manufacturers any more.

STeve.

[rouse]

I'm not sold yet. I spent the time to go through all the laboratory test results posted.

The conclusion I came up with is, this material may be a good substitute for mild steel tubing, but it simply is no substitute for 4130N.

I don't see a problem using it where mild steel is called for, but I would treat it as mild steel for design and characteristic purposes.

I didn't find anything posted for modulus of elasticity for this material at all, so how is it going to act under dynamic loading? What numbers do you use for moment of inertia on various product forms?

I'm not saying I wouldn't use this material, I'm just saying the jury is still out, as far as I'm concerned. Probably thumbs up only for mild steel substitute.

Rouse





 

[SteveM]

Modulus of elasticity should still be 29 x 10^6 psi. 

[Interested Observer]

The conclusion I came up with is, this material may be a good substitute for mild steel tubing, but it simply is no substitute for 4130N.

I don't see a problem using it where mild steel is called for, but I would treat it as mild steel for design and characteristic purposes.

I would agree with Rouse.  The chemistry is similar to 1117, a relatively mild steel.  The enhanced yield and ultimates are a result of significant cold-working.  The yield and ultimate are relatively close together.  Has reduced elongation.  Couldn't find any Charpy (fracture energy) info.  Yeah, it is probably more easily welded successfully, but the weld heat kills the coldwork, so you're back to mild steel near the weld.  Their own weld tests showed failure in the HAZ as would be expected from the reduced coldwork and the high-strength filler material used.

(Moment of inertia is a geometrical property, and does not depend on the material.)

[rouse]

(Moment of inertia is a geometrical property, and does not depend on the material.)

Yelp, geometry.

[hotrod]

http://www.ssab.com/Products--Services/Service--support/Technical-support/Knowledge-Service-Center/Joining/Welding-Docol/

http://www.ssab.com/Global/DOCOL/Brochures/en/312_Welding%20of%20Domex%20and%20Docol%20Advanced%20High%20Strength%20Steels.pdf?epslanguage=en

Larry

[rouse]

I have been welding race car chassis for since the late 60's, all 4130 material. One of the oldest tricks of the trade for ductile welds is to use mild steel filler wire ie. AWS A5.28 ER 70S. On thin wall tube welds you get enough delusion from the base metal to alloy up the welds. That line of thinking does not apply to heavy wall/ materials, in that case use the higher alloyed filler material.

Welds on thin walled tube will tend to gain to much alloy and become too hard, thus prone to failure when subjected to high stress dynamic loading. The lower alloy filler puts a stop to that problem.


Rouse

[javajoe79]

Do some folks still post heat treat 4130?     Like Rouse said I believe most people just use ER70S2 and call it good.  For those that do post heat treat, what rod do you use?

[rouse]

PWHT on thin wall 4130 can cause more problems than it will fix.

Some years back there were some chassis builders that got the "Bright Idea" to build race cars using 4130 HT, When those cars started breaking all to pieces, they tried to solve the problem with PWHT.
The cars still broke up, so they just kept doing the same thing until people started get "HURT", that's when there was a real engineering study done on what was causing the problem. Turns out some knot heads were building cars with 4103 HT. The aircraft industry banded the use of 4130 HT back in the 1930's because of it's fatigue problems. The engineering was there for anyone who spent the time to research what they were doing.

The only way to PWHT a chassis is to locally HT each joint, which is a big pain and time consuming if done right, could you just imagine what a noodle a chassis would look like if put into an oven complete.

Rouse

[Kiwi Paul]

Rouse--I was taught to use the softest ER70 Rod available. I used S6 for the only one I have ever done. I am more at home hammering .040 cold rolled sheet... Have used this rod and my trusty Lincoln Tig for years, weled alot of mild steel Hot Rod and Custom stuff together, but am interested in learning more about 4130. Thanks for your insight...

[Vinsky]

Any comments on using 316L filler on 4130? I have used it on just about everything except 4130.

[rouse]

ER70-S3 and ER70-S6 are the most common filler wires available in most welding supply stores around here. The last number denotes certain oxygen scavengers that are added to the alloy to improve weld quality in certain conditions. Those added ingredients, for the most part don't have a big negative effect on single pass welds, but you'd need to be more selective on multiple pass heavy wall welds.

rouse

[rouse]

Any comments on using 316L filler on 4130? I have used it on just about everything except 4130.

316 SS is not a good choice for welding any CS base metal, there are chemistry issues that comes into play.

 I have seen folks use SS filler on 4130 as a coverup for bad welding conditions or in order to fix porosity problems. If you want to use SS filler 309 or 310 would probably be a better all around choice. In certain cases I have even use Inco-82 to joint dissimilar materials to Chrome-Molly.

Rouse