ASME Section II Part A

[QAFitz]

A material specification table that indicates the Yield to be reported in 2:, and the production part is too small to yield a standard sized specimen, are sub-sized tensile specimens as defined in SA-370 prohibited?
If yes please site the paragraph reference chain.
If no please site the paragraph reference chain.

 

[Guest102023]

What is the product form; i.e., casting, forging ...?

 

[QAFitz]

Bar stock or fastener material.
For example:
1) A/SA-540: The strength TABLE has the elongation in 2", however, there is a paragraph in the A/SA-540 Standard that indicates that production pieces may be used (under certain conditions).
2) A-962: Paragraph 8. Mechanical Properties references A370 and also establishes specimens shall be obtained from the production material.
In both of these instances lets say 3" nuts are to be made which have a height (length) of approx 3". When a production piece like this is used the elongation cannot be measured in 2".

 

[metengr]

There is no provision for using subsize tensile specimens in at least ASME SA 540. Other ASME material specifications do allow for subsize specimens but this must be reported and corrections must be made regarding the results (especially for impact testing). There are no blanket statements or assumptions for using subsize specimens unless specifically allowed by the specification. Review SA 540, section 16.1 and 16.2, excerpts below

16.1 A discard equivalent to the diameter of the bar
when heat treated as a solid or a discard equivalent to the
wall thickness when heat treated as a seamless tube, bored
bar, or hollow forging shall be taken prior to removal of
test coupons.

16.1.1 When production pieces are not of sufficient
length to permit removal of test coupons in accordance
with 16.1, the mid-length of the specimens shall be at the
mid-length of the production pieces selected for destruction
to provide test coupon material. The production pieces
selected for test shall be identical with respect to the
quenched contour and size except for length which shall
equal or exceed the length of the represented production
pieces.

 

[QAFitz]

I saw 16.1 and 16.2 in the Standard and that is part of the reason for starting this thread. If...

16.1.1 When production pieces are not of sufficient length to permit removal of test coupons in accordance with 16.1, the mid-length of the specimens shall be at the mid-length of the production pieces selected for destruction to provide test coupon material. The production pieces selected for test shall be identical with respect to the quenched contour and size except for length which shall equal or exceed the length of the represented production pieces.

A 3" nut production piece would allow a standard 10mm x 10mm x 2" charpy specimen. What is the size of the tensile test specimen for a 3" nut production piece?

 

[metengr]

In other words from 16.1 above you can use a production blank that is the same heat and is subjected to the same heat treatment as a production nut to provide mechanical test specimens.

 

[QAFitz]

Yes, that is the point of discussion: why or why not?
Sub size specimens in A-370 are proportional to the .505 2" gauge length size specimens to assure the results are basically the same regardless of the size of the specimen: Yes / No ?

 

[metengr]

No, not for elongation. Stated gage length for elongation is what it is. Reduction of area is a different matter.

 

[MitchGufry]

Is there a paragraph reference in A-370 to support this?

 

[metengr]

QAFitz;
ASTM A 370 Note 4 indicates that the gage length for a subsize specimen must be 4X the diameter for a subsize round specimen. The elongation results are comparable to a standard specimen. Comparable does not mean equivalent and for subsize should be reported as 1" gage length for comparison, not 2" gage length.

 

[QAFitz]

The test reports I see where a sub-size specimen was used report the diameter and the elongation in 4d. the diameter is the indicator that a sub-size specimen was used.
If a sub-size specimen does not render similar results as a full-size specimen then I would believe the A-370 and E-8 Standards would prohibit their use. ASTM E-8 (2001) Table 8 Note 5 indicates that "The use of specimens smaller than 0.250-in. diameter shall be restricted to cases when the material to be tested is of insufficient size to obtain larger specimens or when all parties agree to their use for acceptance testing." However it does not prohibit .350 or .250 round specimens.

 

[MitchGufry]

When you have a test performed are you specifically requiring a full size specimen must be used?