What is ASME F-Number for filler metals?

What is F-Number in Welding?

F- Numbers are given based on the usability characteristics (defined in ASME Section IIC, SFA 5.1 for example for carbon steel SMAW electrodes) and metallurgy of the welding filler metal in BPVC ASME Part-9 and AWS D1.1. F-Numbers are given to welding filler wire/ electrode by the ASME to a similar group of welding consumables (Welding electrode- Stick, TIG, MIG, FCAW, & SAW, etc.) having akin properties & characteristics. ASME Section 9, Table- QW-432 have listed the welding consumables with their respective F-Number. 

F-number is an essential variable for performance and procedure qualification as per ASME Section IX, AWS D series, and ISO 15614 series. This F-Numbers sorting for welding consumables (electrodes & wires) are founded on their welding properties (ease to use, coating type, type of rod, etc.), which affects the welder’s ability to produce a satisfactory & sound quality weld joint. Also, this F-Number grouping, helps to minimize the quantity of WPS qualifications and welder performance qualifications (WPQ), as similar welding electrodes can be used without re-qualification, and hence a potential cost saving.

F Number Alloy grouping

F-Number for electrode and filler metals are grouped based on their metallurgy. The below table gives the classification based on BPVC ASME Section IX.

Below is the list of N-Number for welding consumables most widely used. F-Number for E6010, E6011, E6012, E6013, E6014, E7024 is F. Number 1. F-Number for E7015, E7016, and E7018 is F-Number 4. F-Number for ER70S-2, ER70S-3, and ER70S-6 is F. Number 6. F-Number for E309L, E308L, and other austenitic stainless steel welding consumables is 4. Refer the below table for the full list of F-Numbers in welding.

Importance of F Number for Procedure Qualification (WPS)

F-numbers for welding consumables are listed and specified for various filler metals & rods (for stick welding, TIG, GMAW, FCAW & SAW- for example) in ASME Section IX- Table QW-432. F-Number being an essential welding variable for procedure & performance qualification if changed that actually being used for the test, require requalification of the WPS or welder/ operator. ASME Section IX does permit changes for non-essential variables or some specified range (For example current, voltage, preheat temperature) but For F-Number it is not allowed. The F-number must be the same on WPS as used in the PQR qualification stage. Refer to the below table and you will notice that F-Number is an essential variable for procedure qualification. Although the change in electrode diameter is a non-essential variable.

Importance of F Number for Performance Qualification (WPQ)

The change from one F-number to another F-number is allowed within a range for welder performance qualification in ASME section IX or AWS D1.1. If you refer to the ASME Section 9, Article III, for welder qualification, You will find the essential welding variables applicable for welder qualification in Table QW-352 to QW 357. In these tables, you can see that F-Number are an essential variable for welder/ welding operator WQT or performance qualification.

Table QW 352- QW 357, provides the range of F-Number used during WQT and the range qualified for F-Number in the Table QW-433 (abstract given below from ASME Section IX). Here, take an example for F-Number 3. If welder had used F-Number 3 rod during welding, he is qualified to perform welding using F-Number 1, 2 & 3 within the conditions specified in this table. (E.g. with/ without backing).

Making a selection of a F-Number that covers the wide range of qualified F-Number is a wise decision that should be considered before the start of the WQT. This is essential to reduce to cost of welder qualification (WQT).

For example, using carbon steel pipe or plate material instead of using the costly stainless steel for the welder qualification test coupon. ASME Section IX allows the qualification of P1 material (carbon steel) to qualify welder on P8 material (Stainless steel). This ensures financial savings by using the WPS or welder for a wider range. In this way, a welder can be qualified for stainless steel (P8) by using carbon steel (P1) but as F-Number is an essential variable, the welding electrode must be used of stainless steel only.

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