Diffuseable Hydrogen content in filler metal

Date 10-14-2007 12:10

Diffusible hydrogen testing is an optional attiribute in the AWS filler metal specs. What you should see as part of the electrode designation on the cert is H4, H8 or H16 (meaning the lot of material has less than 4, 8 or 16 ml/100g of deposited metal). I'm not sure what H3 means but I am not familiar with D1.1

Since diff H is an optional designation, be sure that you specify the maxiumum you will allow when you order the material.

By 803056

Date 10-14-2007 16:55 Edited 10-15-2007 02:40

H1, H2, and H3 are designators found in AWS D1.1-2004 (and other editions) Annex XI for alternate preheat determination.

H1 - extra low hydrogen (<5 ml/100g)
H2 - Low hydrogen (<10 ml/100g)
H3 - Hydrogen not controlled

A bit of clarification may be in order. These are not the optional hydrogen designators mentioned in Phil Thomas' post. They relate to the type of electrode and storage conditions use to ensure certain levels of diffusible hydrogen are not exceeded.

I use this method to determine preheat requirements when I know the chemistry of the base metal, but not the specification. I encounter this situation when doing maintenance welding on old machinery and steel castings. The preheat temperature derived using this method is usually conservative in comparison to other systems, but it hasn't failed me yet.

Best regards - Al

By darren

Date 10-15-2007 02:19

http://www.kobelcowelding.com/dw50.pdf

By PhilThomas (**)

Date 10-15-2007 02:34

sheesh....you'd think they would match, eh?

By 803056

Date 10-15-2007 02:43 Edited 10-15-2007 03:03

Hello Phil;

I tried to clean up my post to clarify the differences between the H8 and H4 designators used in conjunction with the electrode classification you mention and the one's used in Annex XI.

I hope it helps. And yes, it would be helpful, just as it would be helpful if EXXXX-C1, -C2, -C3 meant 1% nickel, 2% nickel, and 3% nickel respectively. That would be too simple.

Added thought: Remember that if an electrode is specified without the optional diffusible designator, you can use any electrode that meets -H16 or lower, i.e., -H8, -H4, but if you do use the diffusible hydrogen designator in the WPS, purchase order, or drawing, then the designator becomes the maximum diffusible hydrogen permitted. In other words, an electrode specified as E7018 can be met by any electrode meeting E7018, E7018-H8, or E7018-H4 classifications. However if the electrode classification specifies -H4, any electrode with a higher diffusible hydrogen content is not permitted.

Best regards - Al