# Machining weldments



## Paul Erland (May 3, 2012)

Hey folks,
I would like to use weldments for a project but not sure how to prepare them for machining. I believe the process is called normalizing but maybe that's not the right technical term. As I understand it, I need to soften the welds and relieve the stresses in the metal from the welding process by heating the part and allowing it to slowly cool. For steel, how hot does the part need to be? I'm assuming cherry red. Does the part need to stay at temp for some minimum amount of time?

Tried internet searches for weldments and normalizing but didn't really find what I was looking for. Any information or links is appreciated.

Thanks, Paul


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## Mike N (May 3, 2012)

What type of material are you welding?

Mild steel will not require any treatment.

Cast Iron & Tool Steel should preheated to prevent cracking.

Alloy steel should be anealled if you plan on machining the welded area.


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## Paul Erland (May 3, 2012)

Mild steel would be the material but wouldn't the bending stresses and hardness of the welds still be a problem?


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## ProdEng (May 3, 2012)

If you try a search for "stress relieve fabrication" you will find lots to read. Distortion of a fabrication is possible during machining and depends partly on how much material you remove.


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## Deanofid (May 3, 2012)

Paul Erland  said:
			
		

> Mild steel would be the material but wouldn't the bending stresses and hardness of the welds still be a problem?


If you use common welding rods, like 60xx or 7018, the welds won't be hard to machine. MIG welds from mild wire won't be any trouble either. Clean the flux off well before you machine. 
Not sure what you mean by "bending stresses".


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## Paul Erland (May 3, 2012)

By bending stress I refer to the pull the welds put on the parts. My experience with welding is that the cooling weld tends to pull on the parts which can cause the parts to move towards each other. Weld two parts at 90 degrees and after welding you usually find the parts at slightly less than 90 degrees when it has cooled. This stress is always in the metal like a spring. I figured that machining would allow this stress to distort the part as material is removed.


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## Entropy455 (May 3, 2012)

Assume you T together two pieces of steel. You grab some 1/16 stick electrode, and place a 3/16" fillet weld down the length of one side. The part will likely bend over a bit at the weld, forming a bent tee, unless you tack the backside prior to running the fillet.

Heres why: steel has a thermal coefficient of expansion of about 6 millionths of an inch, per inch, per degree F.

That means that a 3/16 fillet bead (0.265 across the diagonal) will shrink by 0.0042 as the weld cools from a steel solidification temperature of about 2700 degrees F, down to a room temperature of 70 degrees F. Four thousandths might not seem like a lot, but when its placed in the root of a weld, its giant. This is why steel parts bend out of shape when you weld them.

If your parts have sufficient rigidity (or if you tack the backside), they will not visibly deform, however significant residual stress remains in the part. When you attempt to machine a weldment for close tolerances, its not uncommon to see surfaces grow (or shrink) to new dimensions, as adjacent surfaces are machined.

To stabilize the part for machining, one can accomplish a post-weld stress-relief.

This is normally accomplished by heating and maintaining the weldment between 1100 to 1200 degrees F. This temperature is cold enough to prevent appreciable changes to the lattice grain structure, but hot enough to permit the grain boundaries to slip (or creep) in a slow and controlled fashion  which is the mode of stress relieving. It's normaly baked for about 12 hours, then slow cooled.

Any shop that can heat treat and temper steel, is capable of accomplishing a stress-relief heat-treatment. It should be one of the less expensive processes offered.


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## Jasonb (May 4, 2012)

If you can get the part upto red heat and hold it there for a while and then allow to cool as slowly as possible then it can be done at home, really depends on the size of the part and what heating arrangements you have. The same method can be used to get rid of hard spots in iron castings.

This is a good example and there are several other fabrications being treated later in the thread.

J


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## steamer (May 4, 2012)

I THINK Paul is talking about internal stress put up by welding and fabrication process

Once you start cutting the weldment will start to move around.  Stress Relieving is the correct term

The most "popular" method is with heat, If I recall to 1175F for 1 hour for every inch of thickness followed by slow cooling.

This is not annealing, which would be much hotter.  This would cause a lot of distortion in a weldment because the parts would probably sag in the furnas

The other method involves shaking the weldment at or near its natural frequency.....I've seen it done....but not recently.

The old school way is park the part outside for a few months in the weather...works well on iron,,,,no so well on steel due to oxidation.

Normalizing , to me anyway, implies stress relieving followed by a sub zero treatment.....that's how I've used it anyway. It imparts long term stability to the part...ie it doesn't move around as much with age.


Dave


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## Maryak (May 4, 2012)

Hi Guys,

In my experience, machining weldments, done by stick, (MMA), is a pain in the butt especially if it involves trying to blend them to the mating parts such as a Flywheel and hub. The weld will machine OK as will the 2 originals but the boundaries of the weld are usually hard and cause the tool to either rub and lose shape or jump away at this point.

I guess that IMHO Yes they need to be heated up to a bright red and then allowed to cool slowly, either in the furnace or buried under lime for 4 hours minimum.

Best Regards
Bob


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## Entropy455 (May 4, 2012)

Any steel that has more than about 0.28% carbon is going to harden up in the heat affected zone when SMAW (stick) welded. The penetration is good, but the heat input is simply too high if you intend to machine the component without stress relieving.

Ive found that TIG welding with 70S-2 or 70S-6 rod will minimize the hardening effect within the heat effective zone (to the point where you "can" get away with not stress-relieving). The 70S weld beads are easier to machine also.

FWIW, proper stress relieving is normally accomplished over many hours within an industrial oven - not over a few minutes with a torch in the garage. It must stay between 1100 and 1200 degrees F for several hours. Parts requiring high tollarance will stay in the oven for 12 hours or more. . . 

1200 degrees is where the steel is just starting to show a dull dark red.

Once you hit orange, youre in the austenitic zone, and youve completely changed the lattice structure of the steel (dissolved all of the carbon). At this point, unless you can slow-cool the weldment at a rate not to exceed 100 degrees F per hour, you are going to have more residual stress than if you just left it alone.


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## steamer (May 4, 2012)

From various sources....google is your friend.

"...STRESS RELIEVING: (300 - 1400°F) 

Thermal Stress Relieving is generally applied to metallic materials that have been cold-worked, formed, machined, flame-cut, or weld-fabricated to reduce residual stresses for dimensional stability or reduced risk of premature failure in service.

ASME Section I: (900 - 1300°F)
Stress relieve/Post-Weld Heat Treat in accordance with ASME Section I, PW-39 for carbon steel weldments....."


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## steamer (May 4, 2012)

A link to vibratory stress relieving

http://www.vsr2.net/


and another link from the Weld Journal

http://www.aws.org/wj/sept01/cullison.html


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## Entropy455 (May 4, 2012)

If you wish to cut the oven time down, you can lightly tap the steel adjacent to the welds with a hammer, and the impulse events will encourage the grain boundaries to slip.

On that note: stress relieving carbon steel below 1000 degrees is virtually ineffective, without some sort of additional mechanical help.

Compare it to cooking a turkey in the oven. Too hot, or too cold, and youll have an undesired outcome.


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## Mike N (May 4, 2012)

Paul Erland  said:
			
		

> Mild steel would be the material but wouldn't the bending stresses and hardness of the welds still be a problem?



Not if you use mild steel welding rods!


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## Deanofid (May 4, 2012)

Entropy455  said:
			
		

> On that note: stress relieving carbon steel below 1000 degrees is virtually ineffective, without some sort of additional mechanical help.


He's not using carbon steel. He told us the material he's using in the 3rd post. 
All he needs to do is weld with 60xx or 7018 or a mild wire in a MIG. He can stress relieve it to good effect with a ball pein hammer.

Paul Erland, make your weldments with equal weld beads in "symmetrical" fashion as much as possible. In other words, if you well on one side of something, try to put a similar bead on the other side of that something. Mild steel doesn't build up a lot of stress from welding, but the weld itself does make some.

On one machine job I had, we made hundreds of large clamps that were weldments to make the assembly, then machined over a fair part of the exposed surfaces. 
Right off my welding table, I had a guy with a rose bud who went around the hot weld beads a few times, then beat the thing with a large ball tipped scaler. The next day, after these things had cooled, I put them on the lathe and faced the 10" flange and brought it to diameter. We never had any warping problems (post machining), since the pieces were made from mild steel, using a mild rod. 
I'll mention that I was a welder first, and machinist second. We made so many of this kind of thing in that shop and had no trouble with warping, nor with the machining of the welds themselves. 

I don't know exactly what you are making. Maybe if you tell us, and mention how large it is, you can get some advise that doesn't wander to all aspects of machine and welding work.


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## steamer (May 4, 2012)

Deanofid  said:
			
		

> He's not using carbon steel. He told us the material he's using in the 3rd post.
> All he needs to do is weld with 60xx or 7018 or a mild wire in a MIG. He can stress relieve it to good effect with a ball pein hammer.
> 
> Paul Erland, make your weldments with equal weld beads in "symmetrical" fashion as much as possible. In other words, if you well on one side of something, try to put a similar bead on the other side of that something. Mild steel doesn't build up a lot of stress from welding, but the weld itself does make some.
> ...



Good points Dean

Dave


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## Entropy455 (May 5, 2012)

Mild steel and carbon steel are the same thing.

http://simple.wikipedia.org/wiki/Carbon_steel


Using a rosebud and a ball tipped scaler falls within the additional mechanical help category of low temperature stress relieving. As with most things in life, theres more than one way to do things. Ive designed close-tolerance industrial machine foundation components that were fabricated from weldments. Our machinists were unable to obtain satisfactory parallelism unless the pieces were fully stress-relieved at 1200 degrees, for a full 12 hours, prior to machining.


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## Ken I (May 5, 2012)

Welding introduces stress - period !

Stresses introduced throughout the assembly but typically highest in or close to the weldments.

Machine away any stressed material and your job will change shape.

Heat up your (stressed) job and your job will change shape.

How much you need to worry about it depends on the accuracy of the finished part.

If you are going to be doing machining of the weldments and accuracy is an issue then a full destressing or normalising is required.

If its a garden gate - who cares.

Ken



 what you want.


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## steamer (May 5, 2012)

Hi

Although it is nice to wax poetic regarding process....guilty as charged....it doesn't provide much assistance to the guy in his shop with little more than a torch.

Now that we all know how it "should" be done, perhaps some pragmatic useful advice is in order for the Home shop guys who don't have a controlled furnas.......and let's keep it real.



Dave


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## Jasonb (May 5, 2012)

Stick it in a fire then let it cool overnight in the ashes, I've recovered several chilled castings this way and as similar methods are needed with weldments thats how it can be done in the home.

I've also done similar with CRS that was going to have a lot cut off one side or out the middle to reduce the amount it will move.

Blasting for half an hour with a propane torch has also rescued chilled castings but this is really only economic on small castings as large items are hard to get hot enough and you would use a lot of gas.

J


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## Entropy455 (May 5, 2012)

Heres the home solution:

Obtain a used (but functional) 240-v, single-phase, electric pottery kiln. They are less expensive than you might think.

Then go online and purchase a new digital oven temperature control, with a working range up to 2000 degrees F. Important note: the oven controlers quickly go up in price based on their current switching capacity ($$$). However the temperature sensing and control circuitry is the same, even for the 110-v base models. Thus purchase the inexpensive 110-v version, then purchase a 50-dollar electric contactor thats rated for 240-v and 60 amp. This will permit the 110-v oven controller to switch current as if it were a larger and much more expensive 240 volt version.

Wire in the controller and install the thermocouple. Do not install the thermocouple directly adjacent to the heating coils, or in a position where it receives appreciable radiated heat from the coils  this will prevent unnecessary cycling of the controler relay. With the new temperature controller installed, your kiln is now a metal-working oven, capable of heating steel into its austenitic zone for hardening/annealing, capable of tempering, and also capable of proper post-weld-stress-relieving. 

Important note: the aftermarket temperature controls are required, because kiln controls are approximate at best. For example, say you want heat-treat a piece of 4340  the kiln must be able to maintain 1550 degrees F (+/- 25 degrees F). If you heat past 1650 degrees F, youll permanently damage the metal's grain structure.

Most pottery kiln controls are close within a few hundred degrees at best. 

Consider that you use a lathe for turning, and a mill for surfacing - well, the proper tool for heat treating and stress relieving is an oven. . . .


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## steamer (May 5, 2012)

Ah yes.... the proper tool for the job.  Do you have one by the way along with a vent...ect?

Dave


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## Dan Rowe (May 5, 2012)

Dave,
I have used my burn out kiln for stress relief. I have a programmable controller so holding a temp for a soak and slow cooling are a simple thing to do. My wife has a larger kiln for clay and I had to special order the 60 amp socket.

I could add my controls to the big kiln with a contactor large enough for the load but i have never had the need.

Dan


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## rake60 (May 5, 2012)

I have machined a lot of welded fabrications over the past 20 years.
Almost all of them were stress relived.

Some were heated up then buried in a lime pit for 12 hours to slow cool.
Some were sent out for the kiln type "annealing" style of stress relief.
Some went to a vibratory stress relief vendor.

Any of those processes help to stabilize the metal around the joint, and reduce the
risk of cracks in the parent metal. 

None of them are going to soften up the fusion zone or filler area.
They are going to be harder than the patent metal no matter what you do to it.

Rick


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## Deanofid (May 5, 2012)

Entropy455  said:
			
		

> *Mild steel and carbon steel are the same thing.*
> http://simple.wikipedia.org/wiki/Carbon_steel



They are not the same thing, and the link you provide even says so.

Quoted directly from your link:

_"*Mild steel* is the most common form of steel as its price is relatively low while it provides material properties that are acceptable for many applications. Mild steel has a low carbon content (up to 0.3%) and is therefore neither extremely brittle nor ductile. It becomes malleable when heated, and so can be forged. It is also often used where large amounts of steel need to be formed, for example as structural steel. Density of this metal is 7861.093 kg/m³ (0.284 lb/in³) and the tensile strength is a maximum of 500 MPa (72500 psi)

*Carbon steels* which can successfully undergo heat-treatment have a carbon content in the range of 0.30% to 1.70% by weight. Trace impurities of various other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short. Low alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melts around 14261538° C (26002800° F).[5] Manganese is often added to improve the hardenability of low carbon steels. These additions turn the material into a low alloy steel by some definitions, but AISI's definition of carbon steel allows up to 1.65% manganese by weight._"

Again, Paul; Please tell us what you wish to make, and the approximate size of the item. Maybe we can give you a specific solution that does not include industrial aspects, or building your own kiln.
Honestly, it may be as simple as getting the thing hot, and giving some blows with a hammer. It could also be as simple as; Weld it up, and machine it to size. Depends on what you're making, and the machining steps involved for the piece.


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## Paul Erland (May 5, 2012)

Thanks for all the info folks. It's the backyard/home shop solutions that will help me the most right now. I have an interest in sleeve valve engines and want to experiment around with some single cylinder variations. I am considering making the engine blocks from weldments. Castings would be nice but building a home foundry is a whole other topic.


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## steamer (May 5, 2012)

You may want to consider temperature pencils as inexpensive temperature indicators
http://www.tempil.com/products/tempilstik-original/
Dave


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## Entropy455 (May 6, 2012)

Deanofid, perhaps your point would be better made if you could identify a type of mild steel that does not meet the classification as carbon steel also? I honestly dont think it can be done, because they really are the same thing.

It is common in the steel industry to differentiate between heat-treatable and non-heat-treatable carbon steels, by calling the non-heat-treatable versions mild steel in lieu of low-carbon-steel. That was the point of the Wikipedia page that I linked. Look at it again - its titled carbon steel. And Mild Steel is clearly tabulated on that page as a Type of Carbon Steel.

There are even some shorter industry abbreviations for carbon steels, such as OS, HS, HTS, etc  its all carbon steel. . . . Some high-carbon-steels are often referred to as tool steel.

Its really not a big deal. . . . .


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## Tin Falcon (May 6, 2012)

Ok reality check !!!
Breath gentlemen!!
A guy asks a legitimate question for a hobby back yard project, and we end up disusing the semantics of metal classification, and quasi industrial heat treating. 
While a heat treating oven is a nice thing to have IMHO a little hard to justify in the home shop. I worked in an fabrication shop USAF . we had a heat treating oven . in the 6 years I was in the shop I think the oven got used once. 


> It's the backyard/home shop solutions that will help me the most right now. I have an interest in sleeve valve engines and want to experiment around with some single cylinder variations. I am considering making the engine blocks from weldments.



There have been several engines build here from welding/ fabricating. IIRC markak built a hit and miss and a guy I think Tom built a repro of a 1910 benz the engine was welded and machined. So it can be done , has been done , and you have come to the right place for help. 
Keep it simple get some A36 or 1018 structural steel of the sizes and shapes you need . mock it together tack weld the parts throw it in the oven at 400 then weld it up working opposite sides to keep the heat and stresses even . then throw back in the oven for an hour turn the oven off and let it cool slowly. 
I have welded thousands of parts, sometimes 500 in day . our customer thought we had a robot because " No human could weld that fast and that good" I have burned through countless rolls of mig wire. Unless it is a critical needs to be x-rayed inspected certified weld pre- heats and post heats do not happen a lot in the field.
This is a hobby experiment and have fun . yes ask questions and make sure you have a steel you can machine and weld. or things could get frustrating fast. and for an engine you may want to allow for a cast iron cylinder sleeve . it will wear better than steel .Also the valve sleeves may be better in CI. 
 hope this helps.
a little more info here
http://www.eaglesteel.com/download/techdocs/Carbon_Steel_Grades.pdf
there are many choices. you need to balance cost weldability and machinineability and to some extent strength 

Tin


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## steamer (May 6, 2012)

What Tin Said!


For small parts....like model engine blocks.....made by welding.

It is probably enough to just allow the movement as part of the machine process.

For instance.

Weld your parts. Rough machine the parts and allow .02"-.03"...or the amount deemed required by the situation worth of stock on all critical surfaces that provide alignment to other surfaces, like the block deck/cylinder base interface.

Once all the roughing is done, the part has probably moved all it's going to.  Now go back and finish machine the critical tight tolerance and or tight geometry surfaces.  Geometry meaning flatness/squareness ect.

Dave


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## steamer (May 6, 2012)

Another thing to consider, when using mild/low carbon steel....A36 or 1018...ect in our weldments

Use Hot rolled section instead of Cold Rolled.....and I bring this up so the new guys know this....not to tell you old salts how to suck eggs...

Cold Rolled is just that. it is processed...rolled if you will ,while cold. As such it contains quite a bit of residual stress...something Hot rolled doesn't have because of the difference in how the two sections are manufactured....its done hot!  Keeping the stress out of the raw material in the first place can't hurt.

It's tempting to go with Cold Rolled because it is cosmetically much nicer to look at..it doesn't have the black slag that hot rolled stock has.....but it comes at a cost.  In general, I find hot rolled to machine just fine so leave some padding so you can machine the ugly stuff off after.

Dave


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## steamer (May 6, 2012)

Lastly,

Consider not welding it at all!  Some parts could be advantagously silver soldered!  NO I don't want to get into the semantics of solder vs braze please.  Silver brazing has for ever been called silver soldering...it far predates me....and I suspect it will be that way long after I'm gone.

I bring up silver soldering, because advantageously, it is usually done at or around the stress relieving temperatures of steel, and generally speaking...with small model engine parts.....the whole part gets to the brazing/soldering temperature, while welding can have a very drastic temperature gradient between the melt zone and the rest of the part.

 While not an accurate stress relieving process with demonstrable process repeatablility, brazing/soldering does knock some or dare I say most of the stress out of the part.

It's like chicken soup for residual stress....probably not going to hurt you for one part....in your shop.

Dave


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## Tin Falcon (May 6, 2012)

good stuff Dave. 
This is a hobby it should be fun. there are certainty many ways a project can go wrong and we want to avoid that and many ways things can go right. the best way is the way that works for you in your shop. 
I have a cheap department store welder it is flux core wire feed. that is what I use for attaching steel to steel . 
there are many other tools and methods . I have been trained in oxy-acetalene welding (yes you can weld with one of those) stick and tig as well as brazing soldering. there is also the new multi plaz unit out there. 
when doing many parts in industry use the best most efficient tool for the job. At home use what you have that works. or what you can afford to buy.
Tin


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## Tin Falcon (May 6, 2012)

Rake 60 said:


> I have machined a lot of welded fabrications over the past 20 years.
> Almost all of them were stress relived.
> 
> Some were heated up then buried in a lime pit for 12 hours to slow cool.



jasonb Said:


> Stick it in a fire then let it cool overnight in the ashes, I've recovered several chilled castings this way and as similar methods are needed with weldments thats how it can be done in the home.



The old black smith method is get the piece red hot then put in a metal container full of lime and wood ash 50/50 by volume. 
so a black smith forge would be an option for a heat source . 
you can make one easy enough A used car or truck brake drum a pipe flange, nipples T, and cap drain strainer (fire pot) , a shop vac or hair drier for a blower and a bag of real charcoal from Walmart or other favorite place for fuel. . and a bag of garden lime to pack the heated part in. 
And you are there. 
Tin


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## steamer (May 6, 2012)

As you point out Tin....work with what you've got

I have specified welding on prints for years...but I've never WELDED anything!....at least not on purpose! :big:

I can silver solder to beat the band though....so I tend to be SS centric on that point

Do what works for you.

Dave


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## jonesie (May 6, 2012)

i agree with dave, and use hot roll if you need to weld it.i work in a large engine mfg. plant and do some building of weldments, but not the welding i am just the toolmaker. the boys that do that are the experts and if it is load bearing as below the hook it needs to be hot roll. if it gets welded we usually use hotroll, and no tool steel, and like said leave yourself some extra stock to remachine after welding. also if it is not bigger then our draw furnace it gets but in there to stress relieve. jonesie


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