Cutting a lot of big stick welds (NSFW; factory porn)

Alright good people of PM, I am at wit's end: we are in the machine shop of one of the former largest steel mills in the world. Absolutely amazing building. Each floor has 20 foot ceilings and two 10 ton cranes. At its peak, over 5000 people were said to have worked PER SHIFT in this building alone.

There must have been over 100 machines per side per floor. I know this because where each machine sat, there is a concrete pad. With a large chunk of plate inside it. Welded to larger chunks of bar stock or C channel. Which, in turn are welded to the beams that hold the floor. And let me tell you, when they say "they don't make em like they used to", they're talking about this place.

Now, between the machines used to be 2" hemlock flooring, which was removed ages ago leaving an unsuitable surface. This means we have to cut all these plates out to pour a new deck. And to put it lightly, the plates are putting up quite a fight. Turns out, the fellas that worked here did not like things falling apart, because the welds are beefy, full length stick welds with a solid 3/4" throat.

We've tried pretty much everything from demo saws to OA torches, and just can't find a way to make cutting these welds out less painful. Now, I know its probably in vain, but I figured if anyone could come up with a less hellish way for us to cut all these welds than going to town with a 9" grinder and the skinniest little discs we can find, PM seemed like the right place to look.

So please, someone, tell me there is a special weld cutting attachment for a skid steer or something that I missed, because otherwise we're gonna be at it for a looonnnggg time.

What kind of tip were you using on the torch?
I see 3 options in no particular order:
1-oxy acet with a large scarfing tip
2-500 amp+ welding machine with a carbon arc gouge
3-large plasma cutter with scarfing tip
option 2&3 also need a decent size air compressor. These will all remove only the weld metal once you get good at it.

Why can't you pour concrete over the top of it all? If too thick of concrete, put sand in as fill? You could even get some insulation in there.

Air arc, as above, link 2 500 amp machines together.

Lot's of hearing protection.

Rolling mill roll bases?

How about a much larger grinder, like this: https://www.stihlusa.com/products/cut-off-machines/professional-cut-off-machines/ts800/
Mount it onto this: https://www.stihlusa.com/products/cut-off-machines/cut-off-machine-accessories/machcart/

Regards.

Mike

I second the carbon arc option.
That is what I would want to use if I had to do that...
If you get a good rhythm going it shouldn't be that bad, just wear earplugs and a good respirator... And have a fire watch with a bucket of water handy.

Because of the square footage, pouring the whole thing high enough to cover the plates and not crack would be almost $100k more concrete, so that is out.

We have been using just a regular cutting tip with the torch, but its a little dicey where the bars are welded to the floor beams. I am not familiar with carbon arc gouging but will look into that. Only reason we haven't tried plasma gouging yet is because of the air requirement, but at this point getting a tow behind brought in isn't a big deal.

Also, because I promised factory porn, here are some pictures of the main atrium, including what looks like a faceplate for a large vertical lathe.

Finegrain said:

Rolling mill roll bases?

How about a much larger grinder, like this: https://www.stihlusa.com/products/cut-off-machines/professional-cut-off-machines/ts800/
Mount it onto this: https://www.stihlusa.com/products/cut-off-machines/cut-off-machine-accessories/machcart/


Mike

Click to expand...

We've been running a 14" demo saw, but the issue is that the blades are quite a bit thicker than regular grinding disks and seem to not do the trick much faster than a regular grinder. That coupled with trying to accurately cut just the throat of the weld. Its a bit tough (especially after a few hours) to not cut the beam below or end up with a slot above the weld and basically cutting through an inch and a half of plate.

Now what would be so awesome is if the faceplate was a functioning turntable so you never had to back your car out ever again.

Try to buy some scarfing tips for your O-A torch, they are the funny looking bent ones. Any decent weld supply should have them and you can be doing it tomorrow.

TCasals said:

We've been running a 14" demo saw, but the issue is that the blades are quite a bit thicker than regular grinding disks and seem to not do the trick much faster than a regular grinder. That coupled with trying to accurately cut just the throat of the weld. Its a bit tough (especially after a few hours) to not cut the beam below or end up with a slot above the weld and basically cutting through an inch and a half of plate.

Click to expand...

The air arc will allow a beginner to peal out just the weld.

If in digging out the weld, you nick the top flange of the beam underneath
the plate, simply weld it back up when done.

Oxygen lance will cut that no problem. It will also cut the concrete.

https://m.youtube.com/watch?v=EV4r7OKkXmU

https://m.youtube.com/watch?v=tDeiQ9Grv_I

I have gouged out stuck loader arm pins with one. Was able to plunge in 10-12 “ from the end of the pins to losen it up. It will be kinda pricey but they sure do work.

Ringleboy26 said:

Oxygen lance will cut that no problem. It will also cut the concrete.

https://m.youtube.com/watch?v=EV4r7OKkXmU

I have gouged out stuck loader arm pins with one. Was able to plunge in 10-12 “ from the end of the pins to losen it up. It will be kinda pricey but they sure do work.

Click to expand...

Without going straight down thru the floor beams below ?
Apparently the Op cannot handle a Ox torch, so I think the lance it out.

digger doug said:

Without going straight down thru the floor beams below ?
Apparently the Op cannot handle a Ox torch, so I think the lance it out.

Click to expand...

This suggestion did come up and we had about the same reaction; what a great way to make a big mistake very quickly. Air-arc seems like a winner and fairly idiot-proof. I had no idea this existed and now I wonder how in the hell I missed it.

digger doug said:

Without going straight down thru the floor beams below ?
Apparently the Op cannot handle a Ox torch, so I think the lance it out.

Click to expand...

I’m sure he is having problems because of it being incased in concrete. Torches hate steel covered in sand and concrete.

What size tip you using in your OA torch? Get a #4 or bigger and try it.

TCasals said:

Because of the square footage, pouring the whole thing high enough to cover the plates and not crack would be almost $100k more concrete, so that is out.

Click to expand...

Here in Minnesota when I am involved in big pours, concrete is about $85 per cubic yard. Sand is $2.75 per ton. 1.5 tons to a cubic yard. So 1.5 * $2.75 = $4.13 per yard. So 20.6 times cheaper. If you had $100k of extra concrete, that would be $5k of sand to bring up the level where you could just pour concrete on top. You could telebelt the sand to your second floor. The dry sand can be delivered in the ready mix truck and dumped directly into the telebelt hopper. Or you can have it delivered in dump trucks, dumped on the floor, and have your skid steer load it in the telebelt hopper. One skid steer operator can keep up with the telebelt.

There is also "flowable fill". Flyash and concrete and sand. It is pumpable with normal concrete pump truck.

Ringleboy26 said:

I’m sure he is having problems because of it being incased in concrete. Torches hate steel covered in sand and concrete.

What size tip you using in your OA torch? Get a #4 or bigger and try it.

Click to expand...

Yes the concrete is not helpful in this process. We've jackammered what we can out but the plates cover a bunch still. Torch tip is a #4.

kb0thn said:

Here in Minnesota when I am involved in big pours, concrete is about $85 per cubic yard. Sand is $2.75 per ton. 1.5 tons to a cubic yard. So 1.5 * $2.75 = $4.13 per yard. So 20.6 times cheaper. If you had $100k of extra concrete, that would be $5k of sand to bring up the level where you could just pour concrete on top. You could telebelt the sand to your second floor. The dry sand can be delivered in the ready mix truck and dumped directly into the telebelt hopper. Or you can have it delivered in dump trucks, dumped on the floor, and have your skid steer load it in the telebelt hopper. One skid steer operator can keep up with the telebelt.

There is also "flowable fill". Flyash and concrete and sand. It is pumpable with normal concrete pump truck.

Click to expand...

This is actually a pretty good idea, but we are planning on pouring a 2" top coat, which we're confident will be okay because the floor is already a brick shithouse and there's no thermal cycling. I'd think we'd want a solid 4" if there was sand beneath (which means only an extra $30k in concrete)

Miller has larger engine driven welders with built in air compressor just for gouging. Do you have electricity or do you need engine driven? Since you already have all the torch set up in the building I would still get a scarfing tip. Works great a removing the weld, it will not cut at all, just blows away the weld deposit, just like a carbon arc will.

Another vote for arc air gouging:
You need a large supply of air at at least 80 psi and large hoses ( 1 inch from compressor then 3/4 for your whip.) to provide the volume. Your power supply should at least be 500 amps 100 % duty cycle. For large beads like that you will want to use at least 3/8 diameter carbons.
A thousand amp DC power supply and half inch carbons would allow you to gouge out 3/4 beads in one big pass then a little skim to get down to the beam without marking it.
It is much like taking a butter knife sideways through a block of soft butter.
When you rent your large welder make sure that you let them know what you intend to use it for. You need the large amperage and 100 % duty cycle because gouging is really hard on the machine. Unlike welding the carbon makes dead shorts in the circuit creating huge demands.
I have seen the tears of operators that thought that they could gouge heavy equipment with their little portable pipeliner and end up with a dead machine.
People blocks away will hear the noise in that big building. LOL

I’ve used both air arc and oxygen lance. The lance is quicker and way quieter and won’t even know there is concrete in the way. If you ar going to use the air arc, you will need to invest in some good hearing protection. It’s like welding with a jet engine. And, IME, it will not deal well with dirt and debris (concrete) in the way.

I secound the air arc, but as you then have compressed aair buy a needle scaler, only takes secounds per inch or weld and the process will go so much faster.