Need well versed Annex I expert

Date 03-02-2009 13:51

Looking for someone with a good handle on Annex I D1.1 -08. Please assume we already know how to establish our data. Looking at I6.1.3 it states, "This energy input applies to SAW welds". Next step is I6.1.4 "for other processes .... apply the following multiplication factors to the enery estimated for the SAW process in I6.1.3". I6.1.5 states, Figure I4 can be used to dertermine fillet sizes as a function of energy input". Figure I4 only supplies a chart for two processes.
Question: Which chart on Figure I4 do we use for GMAW process? SMAW or SAW?

By MBSims

Date 03-03-2009 00:00

I'm no expert on this subject, but the AWS Welding Handbook shows that SMAW and GMAW arc thermal efficiencies are very close. So I would use the SMAW curve. Give me time to review the Annex closer, and I'll let you know if I change my mind.

Attachment: arcefficiencies.JPG (0B)

By BillC

Date 03-08-2009 20:14

I6.1.4 contains multiplication factors relating energy input of the SAW, SMAW, FCAW, and GMAW processes. The multiplication factor for SMAW from I6.1.4 is 1.5. This means that for the same size weld, the SMAW process provides 1.5 times more energy input per inch than SAW. The name "multiplication factors" is potentially confusing, as the end user of Annex I will use these factors for division.

Figure I.4 contains graphs of energy input vs leg size for SAW and SMAW. If you compare the two graphs the slope of the SMAW curve should reflect the 1.5 multiplication factor for SMAW found in I6.1.4

On the SAW graph the energy input for a 3/8 leg size is around 42 kJ/in using the DCEN curve and 55 kJ/in using the DCEP curve.

Applying the 1.5 multiplication factor to these values: 1.5 x 42 kJ/in = 63 kJ/in and 1.5 x 55 kJ/in = 83 kJ/in.

From the SMAW graph the energy input for a 3/8 leg is 65 kJ/in. This is very close to the 63 kJ/in value we just calculated for DCEN, and we can conclude that the 1.5 multiplication factor is conservatively based on the lower energy input of DCEN SAW. This is consistent with the Commentary to Annex I.

To answer the original question, if you are performing calculations using GMAW, you would use the SAW graph in Figure I.4.

For example, if you determine you need 40 kJ/inch energy input, what size GMAW fillet weld do you need?

From the DCEN curve on the SAW graph in Figure I.4, a 3/8 leg size provides 42 kJ/in heat input. That's close enough and conservative.

The multiplication factor for GMAW/FCAW from I6.1.4 is 1.25.

Therefore, we divide the leg size from the SAW graph by the multiplication factor from I6.1.4: .38/1.25 = .30

Rounding up to the next fractional weld size, a 5/16 GMAW fillet weld will provide the required 40 kJ/in energy input. This makes sense: the GMAW process provides 25% more energy input per inch than DCEN SAW, so we can use a smaller GMAW weld for equivalent energy input.

Regards,
Bill