Maching Bar Stock Fittings

[ContractHome]

If Astm B366 -S5.1 is required by the end user, then what is the concern:

Does this include both boring the I.D. and turning the O.D., or is maching prohibited with no exception?

What is the concern in fitting machined from bar stock and how does it differ from which are forged?

 

[rustbuster]

I don't understand your question(s). If the fittings are to be used for pressure piping you would require an ASME recognized material.

 

[ContractHome]

What concern does astm b366 -s5.1 have with maching fittings from bar stock? or why would the end user want to invoke this as a requirment?

 

[btrueblood]

The ASTM spec. is for forged or wrought nickel-alloy fittings. Forged fittings are recognized as being generally stronger than "bar stock" machined fittings. This is in part because stringers/inclusions/cold shuts or other defects in the bar stock may intersect a wall, e.g. in a tee fitting, whereas a well-designed forging can make this unlikely.

 

[ContractHome]

btrueblood,

Does this mean the fittings must be completely forged including the socket bore in socket fittings, or can it be forged and the socket depth be machined/bored out?

If forged does b366 -s5.1 mean that a final finish can not be obtained by machining?

 

[btrueblood]

"Does this mean the fittings must be completely forged including the socket bore in socket fittings, "

No, I wouldn't think so.

"or can it be forged and the socket depth be machined/bored out?"

Yes, that is how I have commonly seen forged fittings. You might buy a copy of the standard to be sure.

"If forged does b366 -s5.1 mean that a final finish can not be obtained by machining? "

I'd think a final machining step, at least for tube sockets, threads, etc., is a must.

 

[hydtools]

Is not wrought material rolled or otherwise formed barstock? Specifying forged or wrought just means don't use cast.

Ted

 

[redpicker]

Supplemental requirement S5.1 simply states "Fittings machined from solid bar stock are not permitted."

diverdileo,

You will have to talk to the end-user to find out what their concern is about using fittings machined from bar stock.

The issue is rather clear; the end user has stated that he does not want fittings that have been machined from bar stock. If you want to find out why he has stated this, you will have to ask him. The intent is to forge them to "near net shape" and then finish by machining. I would assume the concern is, for some types of fittings such as elbows or tees, the forging process will direct the grain flow more in line with the direction of principal loading stress and that with a fitting machined from bar stock, you would not get this preferential grain flow. However, the end-user may have other concerns, as well. The only way to find out is to ask.

rp

 

[MikeHalloran]

I'm guessing the customer wants to be able to visually verify that the parts were in fact forged, e.g. by examining the unmachined as-forged surfaces and the parting line.



Mike Halloran
Pembroke Pines, FL, USA

 

[ContractHome]

Here ist the excerpt pasted from astm B366

"B366 S5. Bar Stock Fittings
S5.1 Fittings machined from solid bar stock are not permitted."

 

[ContractHome]

Is the concern in machining or in using bar stock?

If bar stock is the concern what is allowed. Isn't bar stock forged stock that has been turned.

Isn't all stock other than cast forged in some way?

What is the concern?

 

[MikeHalloran]

>>>
Isn't all stock other than cast forged in some way?
<<<
NO.


Mike Halloran
Pembroke Pines, FL, USA

 

[ContractHome]

Forging — The process of working metal to a desired shape by impact or pressure in hammers, forging
machines (upsetters), presses, rolls, and related forming equipment

Is bar stock made from the above definition?

 

[btrueblood]

Bar stock is only deformed in one (long ways) direction. Forgings produce parts in near net shape. If a bar is very close to what your end product is, then perhaps bar stock is good enough, but if your shape is a tee or elbow, then it isn't. This is (or should be, haven't read it) pretty clearly spelled out in the ASTM specification (big hint here: buy a copy, it's not that expensive). Forgings get deformed in two directions, sometimes three if upset forged. Bar stock can/will have longitudinal-direction defects, which may or may not open up under pressure or after some number of cycles of loading. Since fittings per the spec. are not intended to be hydro-tested, a machined bar stock fitting is a risk, one that your customer has not elected to take.

Redpicker has it right with "I would assume the concern is, for some types of fittings such as elbows or tees, the forging process will direct the grain flow more in line with the direction of principal loading stress and that with a fitting machined from bar stock, you would not get this preferential grain flow."

You could always call and ask your customer for an exception to the spec.

 

[hydtools]

What then is a 'wrought nickel-alloy fitting'?

Ted

 

[MikeHalloran]

"Wrought" basically means "bent", in a more general sense. It may also include some incidental stretching and shrinking and shearing, and basically any working process except application of a big hammer.

For a good example, go to the plumbing supply and look at a wrought copper tee. Typically, the branch is extruded out from the run by hydrostatic pressure, while the run is shortened, and thickened on the side opposite the branch. It's done inside a die so the resulting wrinkles are on the inside.

Mike Halloran
Pembroke Pines, FL, USA

 

[ContractHome]

According to the following definitions, bar stock and forgings are the same:


Drawing - A forging operation in which the cross section of a forging stock is reduced and the stock lengthened between flat or simple contour dies

and

Forging — The process of working metal to a desired shape by impact or pressure in hammers, forging machines (upsetters), presses, "ROLLS", and related forming equipment.

So if my bar stock is hot drawn, then isn't it technically considered forged, so what is the concern with bar stock?

 

[MikeHalloran]

I would call all those processes forMing processes, not forGing processes, except the ones that involve hammers or, maybe, very, very fast moving presses.

You can argue semantics all you want, but my friends in the oil patch will send your crap back if they can't see a thick parting line.

If you are arguing this issue with a customer, and trying to use us to back your position, you will lose.



Mike Halloran
Pembroke Pines, FL, USA

 

[ornerynorsk]

I am a hands-on tool and diemaker of nearly 30 years. I can tell you, rest assured, that barstock and forgings are NOT the same.

They have different properties, different welding characteristics, different grain structure, different machining properties, they smell different, and they taste different. No I am not kidding. When you machine and weld metals, they have distinct flavors and smells that permeate your senses, and when something is different, it's different!

I suspect that the argument is being made to your customer for the sake of cost?



It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[redpicker]

diverdileo,

You have a legitimate point in that bar stock is wrought material (wrought meaning "worked from the cast state") and you can have a forged bar or a rolled bar and they will be essentially equivalent. However, the reason the supplementary requirement S5.1 exists is to make it clear that fittings machined from bar stock are not what the customer wants, in plain and simple terms.

Any attempt to make the meaning more percise, such as to define that amount of working required in each direction or to require a specific flow pattern would make the standard much more complicated so it would become 5 to 10 times longer. This would still not satisfy some people and they would want to change it more, doubling or tripling its length, again. You end up with a document with 20 to 50 times more pages, that is much more limited since only specific general shapes could be addressed, not to mention the number of manufacturers that would just refuse to manufacture to it without taking exceptions to the parts they didn't want to fool with.

The wording used in S5.1 makes it clear that bar stock cannot be used. It doesn't matter whether its a rolled bar, forged bar, or even a double vacuum-remelt centrifugally-cast HIP processed bar; if the customer has said he does not the fitting machined from a bar, then he doesn't want it machined from bar.

rp