Madax:
It depends upon the welding process and the rod or wire size, amongst other variables. But, a 5/16th fillet is about the max. single pass fillet that can be made soundly and practically. Draw a full size, standing web pl. on top of a flange pl. Then show full size 1/4" and 5/16", 45̊ triangles as the fillet welds, the weld should be slightly convex to the outside. Anything larger than this is most likely a multi-pass weld made up of weld nuggets about the size of the 1/4" weld, or a little smaller.
Get yourself a couple good weld design books. Lincoln Electric has some very good weld design books by a guy name Omer W. Blodgett “Design of Welded Structures” and “Design of Weldments.” Get them, they are the best book buy you’ll ever make. Look over their other books too.
Practically, a fat 3/16" or nominal 1/4" multi-pass fillet are the smallest that can be made. Using Tig - GTAW - really skilled guys could make an 1/8" multipass weld, but now you are in the realm of making minatures and jewelry.
I demand multi-pass welds on all pressure-boundary welds, and I usually see 1/4" to 5/16" fillets.
I would think that the minimum size of a single pass on a multi-pass fillet weld would be based on the type of weld process used and the section thickness of the parts being welded. You could probably get adequate fusion in a smaller weld using TIG than you could using MIG, simply due to the way the heat is input to the weld location.
Interestingly, just this afternoon I was at a baseball game, and as I was walking down the stadium exit ramp I looked up at the structural welds used to connect the caps and webs of the huge cantilevered steel I-beams supporting the upper decks. These fillet welds were made back in the early 1960's, and the beam sections were probably 1"-2" thick. I could see that at least 3 staggered passes were used for most welds, and I could see the locations along the welds where the welder had to stop and change electrodes. The full width of the fillet welds looked to be at least 1", and each pass looked to be around 1/2" wide.
GTAW thanks for responding......my question is in regard to WPS qualification which is figure 4.19 of AWS D1.1 2008 and it refers to W2 being the min. Multiple pass weld while the table does not specify single or multiple
The tables I believe you are referring to are for prequalified fillet welds. The sizes listed are the minimum weld sizes based on metallurgical considerations, i.e., sufficient heat input to minimize the formation of undesirable microstructures. It is assumed the minimum preheat requirements are met as a condition of prequalification.
One qualifies the WPS for fillet welds when the conditions of prequalification are not met. In that case, the contractor must qualify a WPS for fillet welds. Generally, the welding parameters are established by welding the largest single pass fillet weld and a second sample is welded depositing the smallest multiple pass fillet weld. The is a practical limit to the sizes (both largest and smallest) based on the size of the filler metal used. Once the parameters required to deposit suitable welds are established, i.e., voltage, amperage, travel speed, wire feed speed, etc., the mechanical properties are verified by welding a butt joint utilizing a CJP groove weld. The groove welded assembly is then subjected to VT, volumetric NDE, reduced section tensile testing, and guided bend tests. The essential variables listed in D1.X are reqorded on the PQR and become the basis of the "qualified WPS."
