The Cost Premium for WT vs WF Steel Members 7

[KootK]

I want to know the cost premium associated with ordering WT versus WF.

For example, if one 30' long W18x35 beam cost me $100, what would it cost me to order two 30' long WT9x17.5? $105? $150? Someone must know.

I need this for several things at the moment including this thread: Link

Rationally, I would assume that the cost of transmogrifying a WF into a WT would exhibit these trends:

1) Thicker webs beget greater cost owing to more difficult cutting.

2) For the same web thickness, the percentage cost premium relative to WF should be smaller for larger beams (same cutting cost, larger material cost).

Any body know this space well enough to be able to comment?

 

[XR250]

Perhaps you could call a local steel fabricator.

 

[phamENG]

Any body know this space well enough to be able to comment?

No, but I will anyway.

1) Thicker webs beget greater cost owing to more difficult cutting.

I suspect this will be more of a positive parabolic shape. Thinner webs will be more difficult to cut without distortion, thus costing more as they may require some post-processing to have a usable stem. The cost would likely come down to some sweet spot in web thickness and then turn back up as it takes more effort/resources to get through the thicker web.

I'd check with the fabricator I know, but I'm guessing this is going to be highly dependent on the local market and where WTs are being cut.

 

[structSU10]

As far as where they are cut the last time I spoke to a fabricator about this they received them as WTs directly. It was over a year ago and I can't recall the discussion on price.

 

[KootK]

Perhaps you could call a local steel fabricator.

I could, and maybe I will, but it's not really a local question for me at this point. Rather, I'm casting a wide net in the hope of gathering some genuine principles and insight from our cadre of steel pros here at eng-tips.

 

[KootK]

Thinner webs will be more difficult to cut without distortion, thus costing more as they may require some post-processing to have a usable stem.

Thanks for that, I'd not considered the "too thin" side of things. As you know, this actually reared its head recently: Link.

As far as where they are cut the last time I spoke to a fabricator about this they received them as WTs directly.

That alone is interesting as I had assumed that the WT's were cut at the fab shop rather than at the supplier's facility. I would expect that to lead to a lower premium on WT than if the fabricator tended to it.

 

[Once20036]

Thicker webs beget greater cost owing to more difficult cutting

I suspect this will be more of a positive parabolic shape. Thinner webs will be more difficult to cut without distortion, thus costing more as they may require some post-processing to have a usable stem. The cost would likely come down to some sweet spot in web thickness and then turn back up as it takes more effort/resources to get through the thicker web.

I`ve always assumed that the cost is flat.
Last time I went to a steel fabrication shop, they pressed a button and a machine located then end of a beam, checked it for square, coped it, but the bolt holes, the slide the beam the right distance to do the same thing on the far side. The only human involvement was a person pressing the "go" button.
If an intricate process can be so highly automated, I assumed cutting a W in half is just as automated. The cost would be related to the fact that a beam needs to be cut, rather than being related to any specific parameter of the beam.

 

[Brad805]

The equipment to cut out WT out of a WF is not your average machine. Even the smallest shops have 5'x10' + CNC plasma tables these days, but that will not work for anything but flat stock. To cut this efficiently they need a milling machine like Mill Machine That will be found in a large shop, but they will have minimums before they will even talk about a job like this.

 

[david339933]

Where are you buying a W18@35 for $100?!? That's like 10 cents /lb....sounds fishy.
Edit: sorry re-read and see it's hypothetical....I had some cut recently and was priced $70, $80 for a 30' WT and $150 to plasma.

 

[KootK]

...but they will have minimums before they will even talk about a job like this.

Yes. There have been a number of instances over the years where I've asked for very small amounts of WT for various detailing things and the fabricator has requested that my WT be changed to just two pieces of plate welded into a similar shape. HSS connections, outriggers... whatever. In my head, I'd conflated that with "WT fabrication must be costly". I seen now, however, that it probably had more to do with minimums than a high cost of fabrication in general.

 

[phamENG]

Brad - that's nuts. Thanks for sharing. Really cool stuff.

 

[Brad805]

I think the most efficient web is how Canam or others do it. They buy the stock in rolls or sheets, cut with a shear, and roll as needed. A shear is fast, and not overly expensive. Equipment to roll the shapes is not crazy either. You need to be a large producer to play in that game given the margins. We will wait and see if others have more useful practical experience. I have worked with a few shops that have Voortmans, but not a ton. Many we work with are still fairly old school.

 

[Enable]

I'm fairly new to the steel fabrication game so I haven't been around the block in terms of equipment. But from a smaller guy's perspective for WTs we've done it either with a torch + tack plate as a guide or if space permits use a metal skill saw (if web thickness isn't too big and usually isnt). The metal skill saw is actually quite fast IMHO and gives you a nice cut with a guide but it needs a deeper beam to accommodate the saw in-between the flanges (note: don't worry about the over heating thing...ways around that. I also hot swap saws since I have several in/out).

I would not want to do any of the above at any sort of commercial scale. But for one off jobs / here and there is no problem.

 

[JStephen]

I thought there was some straightening involved after the cut, maybe I just assumed that.

 

[XR250]

For giggles, I called a local fabricator. The salesman did not seem to know too much other than they used to make them in-house but now they buy them from the supplier. Something about too much waste when they do it (huh?) - He could not explain that and I did not feel like pushing the issue.

 

[KootK]

@XR250: thanks for the hustle.

 

[Deker]

I thought there was some straightening involved after the cut, maybe I just assumed that.

That's my understanding, as well. On several occasions I've had WT warping coupled with the deflected shape of an existing beam create fit-up issues when trying to strengthen an existing beam.

 

[dauwerda]

There are many ways to create WT's.
Enable hit on some of the "simplest" ways above. Depending on the cutting method used, you may have a bunch of different issues: If cutting with a torch or plasma cutter, the high heat input will result in excessive camber - this is corrected by heating the flange side of the WT as well to bring it back to straight (or at least within tolerances).

https://www.youtube.com/watch?v=s4PU-RhKPds&ab_channel=SteelSupplyL.P.

If your cutting method results in too large of a kerf, one side of the wide flange may be outside of spec (stem too short) and you only get one WT per W section instead of two (perhaps the too much waste that XR250 was talking about).

As Brad 805 said, the most efficient (at scale) way to create WT's is by shearing them, this results in minimal material loss and minimal heat input, giving you the best product without needing any post processing.

https://www.infra-metals.com/services/t-splitting/

The fabricator I worked for did not use WT's very often, but when needed they would buy the full W section and split them - I don't believe any of their regular suppliers offered WT sections.

I believe we charged around a 25% premium for WT sections. So if your fabricated cost was $2.00 a pound for standard shape stuff, it would have been $2.50 per pound for WT's. However, if you had a project that was using bunches of WT, I imagine one would look to get someone like Infra-Metals (link above) to supply the WT's and this cost *could* be reduced.

The best way to get the most competitive pricing would be to find a fabricator that is regularly using WT's and has a good relationship with a supplier like Infra-metals who has the specialized equipment for splitting the beams (or has it themselves). If this is the case, I imagine the premium gets quite small - perhaps in the 0-10% range.

Finally, I imagine that cost variation is much less regional (at least in the US) and has much more to do with the specializations of the particular fabricator. The fabricator I work for is in central Nebraska and has provided steel to projects in over 40 states. So, we are very competitive in our typical projects, but we would not be competitive when it comes to fabricating structures with lots of WT's.

 

[jike]

If WT's are cut from WF's then they need to be straightened. There are residual stresses in them that cause them to warp. Some fabricators just would rather buy them from a supplier then deal with straightening them. Best way to determine premium is to get a quote from a local fabricator.