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Up Topic Welding Industry / Technical Discussions / Weld Penetration Standards
- - By Harman (*) Date 06-12-2013 17:30
My company is in the process of establishing weld standards. I was wondering do we have any standards on weld penetration to qualify it as a good weld or bad weld ?
Example: If the penetration is 10 %, is it good or bad? We mostly weld stainless steel
Parent - - By jwright650 (*****) Date 06-12-2013 18:45
Hi Harmon,
Welcome to the forum. :cool:
1)Does your facility have any applicable "welding codes" that governs the work that you guys do there?
2)If not what type of work is this that you will be trying to work up standards for?
3)Materials that will be welded? you mentioned Stainless Steel, any others?
4)Shapes of material? (plate, sheet metal, beam, channel, angle, pipe?)
5)Welding processes used to join the materials?(stick-SMAW, solid wire-GMAW, fluxcored wire-FCAW, Tig- GTAW, etc, etc.....)
Parent - By Harman (*) Date 06-14-2013 13:19
John,
Thanks for your reply.
1/2) At present we don't have applicable welding codes and I am working on NDT and destructive testing criteria to differentiate a good weld from a bad weld.
3) We will be welding only stainless steel
4) These will be plate, beam, sheet metal and channel
5) We will be using MIG welding/TIG welding and Spot welding.

I saw AWS has NDT standards to identify a good weld, can you guide me how I should proceed to make these testing criteria?
Parent - - By G.S.Crisi (****) Date 06-12-2013 19:40
Penetration is not measured as "percentage". There is good penetration, lack of penetration and excessive penetration.
You should have on hand a set of photos showing typical welding discontinuities and defects as well as good welds.
A set like that is available at www.ndt-ed.org/index

Good luck in your search
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By cddolan74 (**) Date 06-13-2013 15:06
Harman, are you referring to % dilution
Parent - By Harman (*) Date 06-14-2013 13:30
Chris,
Thanks for your reply.
I meant the ratio of weld bead in base metal/ thickness of the base metal
Parent - - By Harman (*) Date 06-14-2013 13:30
Crisi,
Thanks for your reply.
To be on same page, by weld penetration I meant the ratio of weld bead in base metal/ thickness of the base metal. So can we mathematically quantify good penetration, lack of penetration and excessive penetration ? Can also guide me what are the other criteria I should have in the welding standards ( Macro etching, Tensile test etc) ??
Parent - By welderbrent (*****) Date 06-14-2013 18:43
The only thing that qualifies as your standard for that will be compliance with the contract documents especially the depth of bevel to weld size.  As long as you are giving the engineer, through the shop drawing specifications, what he has asked for there is no problem. 

Z-loss and other factors are all called out in such a way as to make the fitter's job, welder's job, and inspector's job pretty easy.

Have a Great Day,  Brent
Parent - By G.S.Crisi (****) Date 06-14-2013 22:24
Of course, good penetration of a weld would be one in which the weld bead occupies a little bit more than 100% of the base metal thickness. How much more?
The penetration should protrude a little bit over the bevel root. How little?
As I told you on my first posting, penetration is not measured as "percentage", It's classified as "lack of", "good" and "excessive".
To know which is your case, you should compare your weld with one of the tables that exist to analyze welds. On my first posting I mentioned one of those tables that you can download for free.
Giovanni S. Crisi
- By 803056 (*****) Date 06-15-2013 16:28
The size of the weld is dependent on the magnitude and nature of the load or force being transferred from one member to another. The type and nature of the load will dictate the size of the members required. The design is an engineering function; it is not something that is decided by consensus of the welders or the inspector.

The applicable welding standard or design standard, or where neither is applicable, good engineering judgment should determine the allowable unit stress for different welds under different load conditions. Typically a complete joint penetration groove weld using matching filler metal is permitted to be stressed to the same allowable as the base metal. Partial joint penetration groove welds and fillet welds are “derated” to some fraction of the yield strength of the adjacent base metal or a fraction of the filler metal tensile strength. The lower of the two values is the unit stress used by the designer to size the weld.

A weld member loaded in compression where the load is static, i.e., it doesn’t change over time, is often specified as a partial joint penetration groove weld. Whereas a weld loaded in tension and subject to cyclic loading is usually specified as a complete joint penetration groove weld. Again, the type of weld used is based on the load that must be transmitted, the nature of the load, i.e., compression, tension, shear, and whether the load is static or cyclic. It is the responsibility of the designer to analyze the connection and determine the type and size of the weld required to transmit the loads in a safe manner.

Failing the above, the weld should be a complete joint penetration groove weld made with matching filler metal. Even then, there is no assurance the connection will perform as expected if the members are not properly sized. 

Best regards - Al
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