Dave Barton

Question: What is an F-Number and how can I determine what it is for an E71T-1 electrode? I can't find this information in the American Welding Society's D1.1 Structural Welding Code—Steel.

Answer: I don't have enough information here to provide a definitive answer to the question because it is not clear if you are welding to AWS D1.1 or ASME Section IX specifications.

First, the American Welding Society lists F-numbers in D1.1 - 2004 Structural Welding Code - Steel in Table 4.12. This table assigns F-numbers to shielded-metal-arc electrodes on their operational characteristics. F-numbers are assigned in increasing order of welder skill required to produce a quality weld. They range from an F1 for XX24, XX28, which are the easiest electrodes to use, through F4 for XX18 low-hydrogen electrodes, which are the most difficult.

A welder qualifying with a higher electrode F-number automatically qualifies to weld using the lower F-numbers. Within AWS D1.1, the F-number is only used as a variable for welder qualification.

On the other hand, the F-number filler-metal operating-characteristic-classification system comes from ASME Section IX Welding and Brazing Qualification. The American Welding Society adopted a portion of this system by using numbers F1 through F4, for stick electrodes only. Therefore, there is no listing for an E71T-1 electrode and it does not apply.

ASME Section IX paragraph QW-432 lists the F-numbers for a broad array of filler metals — carbon and stainless steel, and steel, aluminum, copper, nickel, titanium, and zirconium alloys. This grouping system reduces the number of qualification tests needed.

Within ASME Section IX, the F-number is an essential variable for procedure qualification. This means, for example, the procedure must be requalified if the F-number changes from F-4 to F-3.

The F-number is also an essential variable for performance qualification, but it's not as restrictive as the welding-procedure specification. For welders using F-1 through F-4 electrodes, the higher F-number electrode qualifies the lower just like in D1.1.

For other F-number electrodes, one test can only qualify electrodes with the same F-number used on the test (e. g., F-5 stainless steel SMAW electrodes only qualify other F-5 electrodes). However, other electrodes may qualify whole families (e.g., qualification with any F-20-series aluminum alloy qualifies all F-20-series aluminum alloys). Find the E71T-1 filler metal specification in SFA 5.20 (the same as AWS A5.20). This specification is listed in Table QW-432 in ASME Section IX and has been assigned F-number 6. Because it has this number, a welder who qualifies with it may weld with all other F-number 6 electrodes.

This column is sponsored by Penton and the Lincoln Electric Co., Cleveland. Dave Barton is a senior welding engineer in the Application Engineering Group. He over-sees welding procedure development for both new technology and existing products, performs failure analyses for customers, and serves as a consultant on welding-application problems. Barton has been with Lincoln for 21 yr. Send your questions to him in care of WDF by e-mail to: askdav@penton.com.