welding ASTM A297 HH heat resistant steel with crazy low elongation ( 1.2%when minimum is 10%) 1

[Tmoose]

Some re-testing is being done, but initial tests were 1.17 and 1.2%. The ASTM A297 is minimum 10%. Tensile and yield rEpORrT3dlY were OK.

The part is a 3/8" wall cylinder 19"Ø.
One end is prepped with inside and outside bevels for full pen welds to SS pipe. The welding will be done in the field by the power plant customer or their agents.

My concern is the effect of the low elongation when welded. 1.2% is not much better at all than gray cast iron.
I'm thinking, with such low elongation, cracking will be a problem if welding with a process that would be fine with nice stretchy "steel."

The question of how a casting with good chemistry and tensile and yield strength can have such low ductility is a mystery unto itself.

 

Was this centrifugally cast? How heat treated?
Something is not right for sure, and the material should not proceed to fabrication in this condition.

I doubt this material can be remediated by further heat treatment. A metallurgical workup is in order, with assessment by a metallurgist familiar with reformer alloys.

Fabrication of a batch of tubes should not rely just on previous welding procedure qualification; weldability should be assessed for each new project.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

This is a bomb with a short fuse.
Someone screwed up, most likely chemistry.
I don't think that you could get it this bad with a wrong HT alone.
But since it doesn't meet the spec it is scrap anyway.

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P.E. Metallurgy, consulting work welcomed

 

[Tmoose]

Thanks for the replies.

I failed to mention this is a casting although ASTM A297 is "Standard Specification for Steel Castings, Iron-Chromium and Iron-Chromium-Nickel,
Heat Resistant, for General Application."

This is one of those ASTM Standards that needs to be referenced carefully, because some of the certifications and tests are "Supplementary Requirements" and not included in the Standard's basic requirements.


Since we did not note we need Supplementary requirement S9.
"The following supplementary requirements shall not apply unless specified in the purchase order."

S1. Magnetic Particle Examination
S2. Radiographic Examination
S3. Liquid Penetrant Examination
S4. Ultrasonic Examination
S5. Examination of Weld Preparation
S6. Certification
S7. Prior Approval of Major Weld Repairs
S8. Marking
S9. Tension Test​

Another example of an ASTM Standard with a monster sleeping under the bed is A48 gray cast iron.

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1.1.1 This specification subordinates chemical composition to tensile strength.
Tensile tests are ALL we can expect unless our PO or drawing says in writing ASTM A48 with a "special requirement for hardness, or chemisty or microstructure".

I guess If we just call for ASTM A48 Class 35 they could ship us a bunch of castings made from aluminum or bronze if they felt like it, as long as the tensile strength exceeded 35 ksi.
After all we did not specify any chemistry.
ASTM A48 does not have ANY chemistry even in the non-mandatory appendix section.

 

[EdStainless]

Two choices, use material with Nil ductility, and who knows what internal defects.
Or scrap it and reorder with S9.
Does the part see any stress in service?
Temperature cycling?
I am not sure that it will survive welding.

A48 material at least has to be gray cast iron, and castings that people care about is ordered with other specs listed as well.
That is actually very common with castings, using multiple specs.

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P.E. Metallurgy, consulting work welcomed

 

The trick with casting quality is knowing who to buy it from.

Kubota in Ontario is one of the best at centrifugally cast reformer tubes. Obviously you don't want to shop for it on Ali Baba (I don't doubt you can find it there).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

And living in WI I know of two or three here.
But starting with a solid spec is step #1.
We had a casting spec with a glitch in it (mistakenly copied from another spec).
Purchasing had us leave it in.
It was how they knew if people even looked at out spec.
No comment and you were off the list.

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P.E. Metallurgy, consulting work welcomed

 

[DVWE]

Purchasing had us leave it in.
It was how they knew if people even looked at out spec.
No comment and you were off the list.

Hmmm. Interesting strategy, especially from the dept that typically likes the lowest of 3 bidders...

The devil is in the details; she also wears prada.

 

[EdStainless]

They knew that they were on the hook for non-conformances.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Tmoose]

interesting/frightening tensile test results.

Decent tensile strength. Sort of.
Very low elongation.
No necking to be seen.
One sample broke completely off the gage length at a slightly low test load.

The proof strength (below yield ??) was virtually the same as the tensile strength.
The yield strength should have been ~ .5 UTS.

I think they cast our parts out of discarded meteorites and old bed frames.

 

Shippers mixed this up with an order for grey iron.

Somebody else now has some fantastic water pipe.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."