Brittle Fracture on Tensile Ti GR12

[dieselofdog]

In reviewing a PQR, I notice one of the two tensile tests is reported to have a brittle fracture in the weld metal, both fail in the weld metal. Min tensile stress for this material is 485 MPa the tests results are 650 and 696 MPa (the brittle one). Both side bends are reported as being ok. No hardness tests have been carried out.

My question, is one brittle break in a tensile grounds to reject the weld test coupon? I have read through QW-150 and it is not addressed. I am learning towards yes as clearly a brittle micro structure is not a desirable material property for my application.

 

[metengr]

You performed tensile and bend testing in accordance with ASME Section IX. The tensile strength of the weld exceeded the strength of the base metals and the bend tests passed, that is all you need for qualification. The successful bend tests demonstrate the weld region can accept up to 22% fiber tensile strain with no cracks or tears. I doubt you have brittle fracture. Grade 12 is a highly weldable alloy. The properties sheet I have shows a minimum of 18% elongation and 25% RA at RT.

 

[weldstan]

Meeting the minimum specified ultimate tensile strength of the base metals joined is all that is required along with location of failure. Fracture appearance is not germane to the test per ASME IX. Ductility is determined through the bend test. Often times fracture appearance is misinterpreted by the test lab (from personal experience).