Acceptance Criteria of Tension Test for Welding Procedure Qualification Record


Why tension test is required for procedure qualification

In ASME Section IX, AWS D series or ISO 15614, The manufacturer or Contractor shall prepare a written WPS that specifies all of the applicable essential variables referenced in the relevant code & standards. The specific values for these WPS variables shall be obtained from the procedure qualification record (PQR), which shall serve as written confirmation of a successful WPS qualification. This PQR needs to verify against the set requirements based on the minimum mechanical properties of the material or design specifications.

The one of the main test to verify these properties are the tension test. Tension test or simply called Tensile Test provides information on the Ultimate Tensile strength, Yield strength & percentage elongation, or reduction in the area.

Click here to Read what is Tensile Testing & it procedure & testing standards.

Tension Test requirements in ASME Section IX

As defined in ASME Section IX, for a WPS to be considered qualified, the mechanical properties are to be tested by welding a test coupon. Tension Test or Tensile Test shall demonstrate that the Weld Metal is stronger than or equal to the strength of Base Metal. Therefore, the result of the Tension Test will have Acceptance Criteria as follows.

Click here to Learn How to write a WPS or a Welding Procedure Specification.

In order to pass the tension test, the specimen shall have a tensile strength that is not less than:

Condition 1. The test specimen broke from the base metal (BM)

(a) the specified minimum tensile strength of the base metal; or
(b) the specified minimum tensile strength of the weaker of the two (In case of dissimilar material welding or material with different tensile strength) in the annealed condition, if base metals of different specified minimum tensile strengths are used.

(c) the minimum specified tensile strength (SMTS) of the weld metal when the applicable Section provides for the use of
weld metal having lower room temperature strength than the base metal;
(d) if the specimen breaks in the base metal outside of the weld or weld interface, the test shall be accepted as meeting the requirements, provided the strength is not more than 5% below the minimum specified tensile strength of the base metal. That is the material is having minimum 95% tensile strength of the material in test as shown in below example.

Condition 2. The test specimen broke from the Weld metal (WM)

(a)Ultimate Tensile Strength or Failure Stress of Weld Metal must be equal to or greater than the minimum specified tensile strength of Base Metal.

(b) In the case of Dissimilar material weld or Base Metal having different tensile strength (SMTS), Weld Metal‘s Ultimate Tensile Strength or Failure Stress must be equal to SMTS of base metal having less strength.

(c) the specified minimum tensile strength is for full-thickness specimens including cladding for Aluminum Alclad
materials (P‐No. 21 through P‐No. 23) less than 1/2 in. (13 mm). For Aluminum Alclad materials 1/2 in. (13 mm) and greater, the specified minimum tensile strength is for both full-thickness specimens that include cladding and specimens taken from the core.

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