What is A-Number in Welding & ASME?​


What is A-Number in Welding & ASME?​

A number are groupings for the ferrous metal weld deposits and are specified into BPVC ASME Section IX Table QW-442 as shown below. A-Number are applicable for the procedure qualification as they impact the weld metal mechanical properties. A number is not applicable for the performance qualification as they do not affect the soundness of the deposit weld, an essential parameters for the performance qualification. Remember that for welders or performance, the F-Number and P-Numbers are used as essential variables, not A-numbers. A number is only applicable for ferrous metal as we can see in below table, and hence A-number is not applicable for non-ferrous weld metal deposit.

a number in welding

A Number can be determined based on the filler metal chemistry when welding matching base metal. For example, welding of ASTM A516 with E7018 or ER70S-6, the A number based on the filler metal chemistry will be 1. In other cases, for example when welding dissimilar metals, the filler wire gets diluted with the base metals chemistry and hence above method will not work. In these scenarios, a section of the weld deposit need to be tested for chemical analysis and then review which A number it matches according to ASME Section IX, table QW-442.

a number of welding

Please note, P- Number, Group Number, and S numbers are groupings of base metals with similar weldability as defined in ASME Section IX Table QW 422 or AWS D1.1. F numbers are groupings of filler metals, and A numbers are weld deposit chemistries.

 P- Number, Group Number, and S numbers are groupings of base metals with similar weldability as defined in ASME Section IX Table QW 422 or AWS D1.1. F-numbers are groupings of filler metals, and A-numbers are weld deposit chemistries.

Please note the A-number in WPS does not refer to the filler wire or electrode chemical composition; it refers to the deposited weld metal chemical composition. The filler metal and deposited weld metal have different chemical compositions.

How to determine A-Number

we can easily decide the A number based on the filler metal specification. In case it is not possible or a weld deposit resulted due to dissimilar metallurgy, a chemical analysis is performed on the actual weld metal, and those results are then compared against Table QW-442 and the A-Number is selected based on the chemical result. In lieu of an A-Number designation, the nominal chemical composition of the weld deposit shall be indicated on the WPS and on the PQR. 

The following typical methods are used in determining the A-Number of the ferrous weld metal composition:

1. All welding processes: by chemical analysis of the actual PQR sample 

2. SMAW, GTAW, LBW, & PAW processes: one of the following

-by chemical analysis of a sample (other than the PQR) per SFA 5.XX, or

-by chemistry reported in the filler metal specification, or

-Supplier Certificate of Compliance (COC)

3. GMAW/FCAW & EGW processes: one of the following

-by chemical analysis of a sample (other than the PQR) per SFA 5.XX, or

-by supplier COC when the shielding gas is the same for the COC and PQR/WPS

4. SAW: one of the following

-by chemical analysis of a sample (other than the PQR) per SFA 5.XX, or

-by supplier COC when the flux is the same for the CofC and PQR/WPS

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