Significance Of A-Numbers in ASME & AWS

[tc7]

ASME Section IX QW-404.5 and AWS D1.6 Table 4.6 both discuss or list "A-Numbers" for weld metal analysis. What is the purpose of these A-Numbers? Is it the expected composition of the as-purchased fillers or is it the composition of the diluted weld metal for the entire joint?

My real task is to find out when it may be required by Code to run PQR tests beyond typical bend, tension or CVN if there may be concern about chrome depletion in various grades of 300 and 400 series stainlesses. I know it is always my perogative to run such tests, but strict adherence to Code requirements do not seem to get me there. I am wondering if the A-Number qualification variable is a cloaked requirement for running sensitization tests when qualifying new WPS's for stainless weldments.

Thankyou for advice on this.

 

[AIAIAANI]

Pay attention when you prepare the test plates for welding and in general when you transfer marking on plate. Add an arrow to indicate the direction of rolling. When you weld test coupons for KCV test put the arrows of the test pieces in line NOT PARALLEL. It means you have to be sure that your KCV coupons are longitudinal and not transverse. You might have made this mistake when you firstly prepared your samples, this justifies the lower energy result compared with those shown in MTR of the steelmaker.

 

[stanweld]

The A-Numbers provided by ASME IX have been created with respect to general weldability requirements and have no "cloaked" requirements regarding senitization testing. For example, qualification with a single classification of A-8 filler metal qualifies all other classifications meeting the A-8 analysis requirements unless impact testing is required, in which case the filler metal classification becomes an essential variable.

 

[tc7]

OK thanks Stan.
If the Codes do not drive you toward a sensitization test on SS welds, how do you know you have the WPS right? Isn't it possible to keep your interpass temps within whatever may be recommended but still cause chrome depletion in and around the HAZ? And still pass bends and tensiles?

 

[metengr]

Section IX of the ASME Boiler and Pressure Vessel Code was never intended to be an engineering consulting handbook for filler metal selection in service. As mentioned above, the A-No like P and S-No's were developed by the committee to classify materials and filler metals of similar welding characteristics.

Regarding selection of filler metal and base metals for a WPS, that is still left up to the organization that is qualifying the procedure. Section IX only provides guidance for what is necessary to assure adequate ductility and strength in service. Specific details regarding filler metal selection and behavior are up to the Engineer to figure out in service.

 

[stanweld]

The ASME Boiler & Pressure Vessel Codes do not address materials selection from a corrosion standpoint. That is the province of the Engineer and Owner/Operator of the equipment.