Impact Test on SA-334 Grade 6 tubes

[teokal]

Hi guys,

Tube material SA-334 Gr6. thickness 2,77mm, diameter 1".
Client requires impact test according to SA-334 and ASTM E23, at -45 degrees Celcius (in excess of UCS-66), due to PED requirements in Europe. A lot of companies, clients etc do not take into account the UCS-66 of ASME VIII Div.1, and they demand impact test to be done, anyway.
Manufacturer claims that impact test is not applicable to this size.
Specification (SA-334) states that impact test is required for above 2,5mm thickness, with subsized specimens.
Manufacturer says that specimen cannot be obtained from the shape and its dimensions.
We revert and said that you can cut the tube on its longitudinal axis, flatten it and extract as many specimens as you like.
Manufacturer replies that flattening of tube for impact test specimen is not allowd.
Checking the Code (SA-334 paragraphs 12, 13, 14, 15, and also ASTM E23, does not forbit any flattening. Note that SA-370 is NOT applicable in this case. In SA-334, SA-370 is referred to therein, but for all mechanical tests, except impact which shall be done according to ASTM E23.
Appendix of SA-334 states that in such cases, manufacturer and purchaser shall get to an agreement.
Do you also believe that flattening is not a good idea?
We have done it several times, always with end user informed and agreed.
What do you think, will the results of the flattened piece, be reliable?

Only best result in absolutely necessary time

 

[metengr]

Why don't you follow the requirements in SA 334 and use subsize Charpy specimens? It is stated below

15.1 Except when the size of the finished tube is insufficient
to permit obtaining subsize impact specimens, all
material furnished under this specification and marked in
accordance with Section 17 shall be tested for impact resistance
at the temperature for the respective grades as prescribed
in Table 6.

Per Table 5 you can reduce the specimen to as little as 2.5mm thickness.

If the manufacturer cannot do this, find a test lab that can machine subsize Charpy beam specimens and perform impact testing in accordance with the requirements of SA 334.

 

[EdStainless]

On 1" tube you would need to weld 'wings' onto it in order to have enough metal for an impact sample.
The curvature it too great, even thought the wall looks thick enough.
I would not flatten samples unless they could be re-heatreated in the actual production HT that the tubes saw. That is a lot of strain to flatten 1" tube.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[teokal]

Thank you guys, will do so...

Only best result in absolutely necessary time

 

[fleischfresser]

Hi teokal,
your requirement concerning impact test of pipe 1 inch 2.77 thickness has nothing do with real word. Have you ever seen machining of test specimen ??

After sawing the pipe pieces will be milled in order to get two parallel surfaces. And that will not performed in 1/100 mm steps.

You can calculate the maximum theoretical obtainable height from the wall thickness for a specimen width of 10 mm (but in the real world I never require such calculation):
NPS 1 10s means : OD 33.4 mm, wall thickness 2.77 mm
With this data you can theoretical get a height of 2.004 mm

Code of construction is ASME VIII/1:
UG-84(c)(3)
"For material from which full size (10 mm × 10 mm) specimens cannot be obtained, either due to the material shape or thickness, the specimens shall be either the largest possible standard subsize specimens obtainable or specimens of full material nominal thickness which may be machined to remove surface irregularities.
.....
Toughness tests are not required where the maximum obtainable Charpy specimen has a width along the notch less than 0.099 in. (2.5 mm)."

Therefore not impact tests have to performed.

But be aware of the additional requirement for carbon and low alloyed steel
UCS-66(d)
(d) No impact testing is required for Part UCS materials 0.10 in. (2.5 mm) in thickness and thinner, but such exempted Part UCS materials shall not be used at design metal temperatures colder than −55°F (−48°C).

But in your case (Code of construction is ASME VIII/1, SA-334 Gr. 6 has SMYS=240 MPa and assigned to P-No. 1) the second part of UCS-66(d)
is applicable:
For vessels or components made from NPS 4 (DN 100) or smaller tubes or pipe of P‐No. 1 materials, the following exemptions from impact testing are also permitted as a function of the material specified minimum yield strength (SMYS) for metal temperatures of −155°F (−105°C) and warmer:
SMYS=140 to 240 MPa --> Thickness 6.0 mm
SMYS=250 to 310 MPa --> Thickness 3.2 mm
SMYS=320 and higher --> Thickness 2.5 mm
that means for your case up to 6 mm thickness is the above pipe exempted from impact testing. And that means the first part of UCS-66(d) is not applicable.


Regards - Juergen

 

[Bokkel81]

Hi Fleischfresser,

How do you respond to a design surveyor (NoBo), who says: "Well, according the ASME you don't need to do an impact test. Unfortunately the impact requirement is a PED requirement so you need to do it anyway."

Best regards,
Bokkel