# Buying Pre-cut Coupons from the Local Steel Yard



## erikmannie (May 29, 2022)

Next week I will be calling the local steel yard to order a lot of .120” thick, 3” X 4” mild steel pre-cut coupons. They will sell me the sheet & cut it on their behemoth press brake.

I have been going to this place for 20+ years, & they are pretty reasonable for material & labor costs.

I will post here what I ended up paying by the pound for these pre-cut coupons, but here are some questions:

(1) What size coupon would *you* choose? I use these for joint & position practice for MIG, TIG, stick & gas welding. Right now I am working on 1F (i.e. flat horizontal). I do butt, lap, corner, edge, & T-joints. No bevel on .120”, obviously.

(2) Is this a good plan to order from the steel yard? They sell nice pickled & oiled coupons online (see screenshot), but they are very expensive.

(3) How would *you* prep these coupons? I *always* remove all the mill scale. I have been using a flap disk on a 4-1/2” angle grinder, but I am going to try to use a milling machine. I will process them in bulk.

(4) I will sell some to interested forum members at my cost. You remove the mill scale. Local pickup is best, but I will ship to US addresses.

(5) Any cost effective ideas on re-using these after I weld them? Pipe welding coupons easily lend themselves to re-use if you don’t mind filler material in your coupon. I could use the scrap for torch cutting practice & then take to a scrapper to be recycled.


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## stupoty (May 29, 2022)

Have you tried "strip and clean" discs for angle grinder , absolutely leave the metal unscratched (might polish it a bit) but cut through mill scale and rust and paint like it's not there.

Basically there the hard scouring pad with glued abrasive.  If you press to hard you can heat them up and make little melty plastic marks with them, apart from that they are a total dream.

Stu









						Strip Discs Stripping Wheel for Angle Grinders Clean and Remove Paint, Rust Weld  | eBay
					

Not suitable for stripper paint or drilling rigs. [Scope of application]-The peeling and cleaning disc is suitable for grinding interface grinding, oil pipe deburring, ceramic bottom polishing, surface paint removal, etc.



					www.ebay.co.uk


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## benmychree (May 29, 2022)

Bead blasting would be another option, Just blast the area that is to be welded upon.


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## benmychree (May 29, 2022)

I worked at a steel fabricating plant (Kaiser Steel)  we did a lot of processing of mostly large coupons for welder qualification tests, and vever noticed any scale removal preparation of the coupons, for the most part they were about 3/4 - 1" thick with a machine burnt angular edge, tack welded to a piece of flat bar for backing and separated from each other so that the weld was of full penetration, after the welding was done, the backing strip was machined off and the plates were sawn into strips 90 degrees to the axis of the weld and surface ground on the sides.  All production welding done there was also without scale removal, so far as I saw.


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## aliva (May 29, 2022)

Check with your state welding qualification board and see what they require. Here in Canada the CBW ( Canadian Welding Bureau) doesn't require that the mill scale be removed but all welders do it them selves to lessen any contamination that might show up in an x-ray or bend test . The scale is removed just from the weld area no more. I wouldn't remove the scale it just adds to your labour, if the buyer wants it removed they can easily do it themselves.


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## erikmannie (May 29, 2022)

I used to work as a bench hand for a guy that MIG welded about 97% of his stuff, almost always structural steel. I never saw him remove mill scale. He has made a living doing steel fab for decades.

Funny story, his workshop was in a mountainous, rural area so his building had a huge amount of dust in it (and mud in the winter). One day he was MIG welding/fabricating a gate. He had a huge gap in the joint. He rectified this by *looking down on the floor* for a rod approximately the diameter and length that he needed to fill the gap. His floor had so much stuff on it that he didn’t even have to walk anywhere. He picked up a dusty piece of scrap rod, didn’t even clean it off, put it in the gap, & kept welding. Of course, this doesn’t matter because it was just a gate for a ranch. Ya gotta fill the gap somehow!

At the welding schools I went to, the students would MIG, gas & stick weld the mild steel sheet coupons without removing mill scale.


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## General Zod (May 30, 2022)

Stick _practice _- I wouldn't bother removing millscale.  Again, for _practice_.  For _projects _I do clean the edges.
MIG short-circuit w/ C25 gas - clean the millscale off the edges as much as possible to minimize undercut.  Hard grinding disc is fastest, coarse flap disc or silicon carbide "quick strip" disc is almost as fast.  3M abrasive bristle brushes are really good I'm told.  Anything else is a waste of time.
TIG - remove all millscale and all foreign material/substances at all costs.

Depending on your own preferences and practices, you can just dunk all the practice coupons (or a lot anyways) in a large tub filled with muriatic acid from the hardware store.  It's about 50% hydrochloric acid by concentration and produces nasty fumes when reacting with the millscale on the steel, so proper respirator is necessary but in about 1 hour all your coupons could be 100% rust and millscale free.  You obviously just have to do it outdoors so the fumes don't rust nearby clean steel/tools, and neutralize the acid before properly disposing of it.  I've been doing this more and more lately.  I just keep a neutralizing solution in the tub next to it, clean off the pieces right away, and then pat them dry on an old towel and just leave them there.  Very minimal rust formation and whatever light surface rust does appear, I get rid of it very easily with a 3M Scotch Brite Clean and strip wheel 07470 on a low-RPM straight air drill I got from Grizzly.


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## erikmannie (May 30, 2022)

General Zod said:


> Stick _practice _- I wouldn't bother removing millscale.  Again, for _practice_.  For _projects _I do clean the edges.
> MIG short-circuit w/ C25 gas - clean the millscale off the edges as much as possible to minimize undercut.  Hard grinding disc is fastest, coarse flap disc or silicon carbide "quick strip" disc is almost as fast.  3M abrasive bristle brushes are really good I'm told.  Anything else is a waste of time.
> TIG - remove all millscale and all foreign material/substances at all costs.
> 
> Depending on your own preferences and practices, you can just dunk all the practice coupons (or a lot anyways) in a large tub filled with muriatic acid from the hardware store.  It's about 50% hydrochloric acid by concentration and produces nasty fumes when reacting with the millscale on the steel, so proper respirator is necessary but in about 1 hour all your coupons could be 100% rust and millscale free.  You obviously just have to do it outdoors so the fumes don't rust nearby clean steel/tools, and neutralize the acid before properly disposing of it.  I've been doing this more and more lately.  I just keep a neutralizing solution in the tub next to it, clean off the pieces right away, and then pat them dry on an old towel and just leave them there.  Very minimal rust formation and whatever light surface rust does appear, I get rid of it very easily with a 3M Scotch Brite Clean and strip wheel 07470 on a low-RPM straight air drill I got from Grizzly really helpful.



That was really helpful. How do you neutralize the muriatic acid afterwards?

Also, if I may ask, how do you get rid of the neutralized liquid?


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## General Zod (May 30, 2022)

erikmannie said:


> That was really helpful. How do you neutralize the muriatic acid afterwards?
> 
> Also, if I may ask, how do you get rid of the neutralized liquid?



baking soda neutralizes it.  It becomes salt water when properly neutralized.  The leftover sludge I can take to my local hazardous waste drop off.


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## erikmannie (May 31, 2022)

@General Zod

What thickness & dimensions would you choose for MIG, TIG, stick & gas welding practice?

I will be on 1F for awhile.


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## Firstram (May 31, 2022)

Use vinegar instead of muriatic, it's slower but not as nasty. Even with the lid screwed on tight the fumes will rust everything in your shop, never store that stuff indoors!


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## addertooth (May 31, 2022)

Depending on the welding process I will remove scale in the area where the weld bead will be. For TIG, I have a wider de-scaled zone to avoid contamination.  I would only remove ALL the scale for "cosmetic reasons".  A piece of steel which was de-scaled one inch from the bead, has a weld which is no stronger or cleaner than one de-scaled a quarter inch from the bead.

For stick, I might de-scale my strike point where the rod makes initial contact to start the arc.  The same is true for flux core wire.  Flux does a good job of floating away contamination. 

Your (long term) cheaper option is to buy a sheet of steel, and a plasma torch.  Then use a right angle grinder to clean it up.  You can get amazingly straight and clean lines with a plasma torch, and they aren't scary expensive (this is assuming you have a compressor to provide the required air for a plasma torch). You can use the rest of the steel to build useful projects once you are comfortable with your welds. 

Good luck on your learning adventure. I started my step-son in welding; he is now attending a welding school to get his certifications.  I am sure that for the basic stuff (like MIG welding), his instructors wonder why he is paying for that class.


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## General Zod (May 31, 2022)

erikmannie said:


> @General Zod
> 
> What thickness & dimensions would you choose for MIG, TIG, stick & gas welding practice?
> 
> I will be on 1F for awhile.



Unless you're getting the sheet for 2017-pricing, I wouldn't be buying anything for practice unless it's scrap, but that's just me.  I think the money would be better spent buying scrap like a combination of flat-bar, angle, square tube, C-channel, round tube/pipe and using that for practice.  But hey, it's your money.  

As for dimensions and thickness, I tend to buy scrap in similar size to my projects: 16ga, 14ga, 11ga, sch40.  Thicker if I can find it at the time.  If I don't have scrap in the same dimension as the project, then I'll use a few slivers from the length to dial in the amperage (if needed) and to get my bearings straight.



Firstram said:


> Use vinegar instead of muriatic, it's slower but not as nasty. Even with the lid screwed on tight the fumes will rust everything in your shop, never store that stuff indoors!



It's also a good method.  I just prefer the muriatic acid since it's so much faster.


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## addertooth (May 31, 2022)

General Zod brings up a good point.  For practice, a good source of FREE steel is bed frames.  On places like Facebook Marketplace and Craigslist, there is an endless supply of people giving it away.  Most are about 12 Gauge in thickness.  I provided my step-son with about three entire bed frames to practice on, before he tried anything serious.  Then I got him a half-sheet of steel to make stuff with.  Below is a picture of him cutting a whole sheet in half.  One half is his, the other is mine. Note the use of the bedframe as a guide for a straight cut.  Also note the practice piece on the bottom left, where he practiced and set his airflow and current before he did the cut on the sheet.


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## erikmannie (May 31, 2022)

It would appear that I will never have room anywhere on my property for either an air compressor or a plasma torch. We have 7 people that live on the property; I was allotted all the space in the garage and side yard. Just over the last week, I have reached the point where have filled up my area. Having said this, I still plan to cram in 2 more wire feed machines & a spool gun.


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## addertooth (May 31, 2022)

erikmannie said:


> It would appear that I will never have room anywhere on my property for either an air compressor or a plasma torch. We have 7 people that live on the property; I was allotted all the space in the garage and side yard. Just over the last week, I have reached the point where have filled up my area. Having said this, I still plan to cram in 2 more wire feed machines & a spool gun.


I understand the space issue.  I have a one car garage that all my machine shop, wood shop, and welding equipment is in.  I have to roll stuff out of the way to clear the space to use some of the tools.  Some of the equipment does not roll (lathe, mill), so the rest of the space is "negotiable".


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## General Zod (May 31, 2022)

erikmannie said:


> It would appear that I will never have room anywhere on my property for either an air compressor or a plasma torch. We have 7 people that live on the property; I was allotted all the space in the garage and side yard. Just over the last week, I have reached the point where have filled up my area. Having said this, I still plan to cram in 2 more wire feed machines & a spool gun.



That is horrible!   plasma is the best, well almost!  It sure is super handy to have.  you just have to do it outside or have really good ventilation and filtration for the fumes/dust.

And no air compressor?!?!??   What kind of hell are you living in?  I'll die before I give up air tools. 


BUT, going by this picture you posted previously...



			https://www.hobby-machinist.com/attachments/7770cb34-608f-49dd-b570-3d45803659d4-jpeg.398629/
		













You have PLENTY of space to spare for more machines.


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## Just for fun (May 31, 2022)

General Zod said:


> And no air compressor?!?!??   What kind of hell are you living in?  I'll die before I give up air tools.



Boy Howdy!

An air compressor is one of the first tools I bought for my shop...... it still had a dirt floor at the time.


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## Winegrower (May 31, 2022)

I bought a 2HP Sears compressor in 1970, and just retired it a couple years ago…actually gave it to a friend.   Now THAT was a good investment.   I could not function in life without a compressor.


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## jarhead (May 31, 2022)

I use vinegar in a immersible container, or spray bottle to remove mill scale


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## Just for fun (May 31, 2022)

I use cleaning vinegar, it's a little stronger than regular but as strong as muriatic acid.  I have just washed it off with water, but boy does it rust in a hurry.  Then I use a wheel on my angle grinder that is made with some stuff like Scotch Brite.  I guess I should try making a solution of baking soda and see if that makes it better.


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## General Zod (May 31, 2022)

Another safer option is washing soda electrolysis.  All you need is water, arm & hammer washing soda powder and a vehicle battery charger/power supply, along with some sacrificial steel.  It produces a lot of gunk in the bucket/tank, but it's mostly just rust and other harmless carbonates.  Look it up if you haven't already seen this.


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## erikmannie (Jun 1, 2022)

jarhead said:


> I use vinegar in a immersible container, or spray bottle to remove mill scale


Do you dilute the vinegar?


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## Firstram (Jun 1, 2022)

No, full strength.


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## Aaron_W (Jun 2, 2022)

I don't know what they are charging you to cut your coupons, but hot rolled flat bar stock is pretty cheap. At my local metal place I think a saw cut is around $8/cut so 2 cuts to make a 20 foot bar fit in my truck will almost double the price. 

I'm just down the street from them so they will deliver for free even on my small orders so unless I can't wait a day or two I can buy full 20 foot pieces and cut it myself which has saved me a lot of money in cutting fees. The little HF bandsaw has paid for itself many times over in saved cutting fees.  


On the vinegar, normal household vinegar is 4-8% but you can buy much stronger concentrations of 30-45% at most hardware stores.


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## erikmannie (Jun 2, 2022)

Aaron_W said:


> I don't know what they are charging you to cut your coupons, but hot rolled flat bar stock is pretty cheap. At my local metal place I think a saw cut is around $8/cut so 2 cuts to make a 20 foot bar fit in my truck will almost double the price.
> 
> I'm just down the street from them so they will deliver for free even on my small orders so unless I can't wait a day or two I can buy full 20 foot pieces and cut it myself which has saved me a lot of money in cutting fees. The little HF bandsaw has paid for itself many times over in saved cutting fees.
> 
> ...


In the case of Reliable Hardware in Santa Rosa using their humongous shearing machine to shear remnants, they charge an hourly rate. I get an experienced operator working on a machine that I could *never begin* to afford. Reliable Hardware is reasonable; they have never hit me hard in 25 years.

I really don’t have room for a bandsaw. I am saving room in the shop for 2 wire feed machines & a spool gun. If I were to buy anything beyond that, I wouldn’t have room to stand in my shop!

I get my hourly rate at my job because my customers don’t have the transportation network in place that UPS does. At some point, I will pay other professionals to do what they are tooled up to do. Believe me, the *time I save* from shearing my own metal is spent working OT.


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## Just for fun (Jun 2, 2022)

What is the reason for two wire feed machines?


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