What weld symbol is appropriate for this

[321GO]

[tt]Hey guys,
hope you're all doing ok.

What weld symbol should be used for this pls see attachment.
I don't know, is it a fillet weld (not quite i guess) or a Y weld (also not quite it seems to me).

When going for the fillet symbol, should then "z" be used for weld size (leg length), since "a" would be confusing?

Thanks a bunch![/tt]

 

[321GO]

I couldn't find it at first but i guess it is a bevel weld.

Symbol would then be ^|/ and since the penetration must be over the complete thickness there is no need to specify depth, correct?

p.s. why is root opening sometimes necessary to specify / use?

 

[fegenbush]

You are correct that it is a bevel weld. The root opening on groove and bevel welds is specified when the designer wants to control how the welder will setup the joint. In my experience, this is done to ensure complete joint penetration, comply with company standard welding procedures, and ensure pre-cut pieces yield the correct finished dimensions. If you are specifying CJP and are not producing shop drawings, general drawing notes or CJP in the note area of the weld symbol should be sufficient. For shop drawings, I prefer to be as specific as possible.

 

[321GO]

[tt]Thanks fegenbush

why is the rootopening necessary for good penetration in the first place? I don't quit get that.
Is it because from certain thicknesses on the tourch simply cannot get deep enough in de root?

[/tt]

 

[ledon]

That is dependent on the thickness of the base materials, and the degree of penetration required to provide the designed strength. Example: if the thickness is 1/4" then a groove would be required to provide 100% penetration and 100% joint strength. Where a partial penetration or fillet joint would provide a lesser percentage of strength.

 

[gtaw]

The weld depicted by the sketch is a T-joint with a single bevel groove. The weld may or may not be a complete joint penetration groove weld depending on several characteristics and what the engineer wants.

AWS D1.1 Structural Welding Code/Steel imposes several conditions on the design. If the weld is made without backing and the WPS is not qualified by testing without steel backing, the weld is considered to be a partial joint penetration groove weld. The allowable stress on the weld is severely limited due the expectation there is a crack initiator in the unfused root, much like a fillet weld.

The groove angle is required to fall within a specific range if the detail is prequalified per figures 3.3 or 3.4 (PJP or CJP respectively).

If the groove detail is prequalified the root opening must fall within a specified range and steel backing must be used if it is welded from one side and it is necessary to be a complete joint penetration groove weld. Again, figures 3.3 or 3.4 are applicable if the groove detail is prequalified per AWS D1.1.

If the weld does not meet all the metrics of a prequalified joint, the contractor is required to qualify the WPS by testing. It would be prudent to qualify the WPS using the groove detail expected in production.

AWS A2.4 is the specification for welding symbols. In general, the welding symbol should include the depth of the bevel, the groove angle, the root opening, and if the weld is a partial joint penetration groove weld; the required weld size.

If the drawing is being generated by the Engineer, i.e., it is a structural drawing, it is only necessary to include the notation CJP in the tail of the welding symbol or both the required weld size and the notation PJP in the tail of the welding symbol if working to AWS D1.1. It would be th fabricator's responsibility to add any additional information to the welding symbol needed by the welder.

Best regards - Al

 

[AlexaS]

321Go.

=====

You wrote:
"... why is the rootopening necessary for good penetration in the first place? I don't quit get that.
Is it because from certain thicknesses on the tourch simply cannot get deep enough in de root? ..."

=====

A welding procedure is qualified by welding out a joint. The various welding variables (including the root gap) are documented. The qualification weld is tested. If all goes well, then a detailed WPS (welding procedure specification) is written up. The WPS is for the welder to follow in production welding. Production welding to the approved wps should result in a weld with similar characteristics as the original qualification weld.

The root opening (root gap) information could be required for various reasons. One is to facilitate the welding (for example: a gap would help to avoid excessive or inadequate root penetration). Another reason could be for metallurgical reasons (for example: a particular gap would achieve a desired dilution between base metal and filler metal in the weld). Another reason could be to make the penetration for accessible (for example: when welding with a backing plate the gap helps to ensure good penetration). Another reason could be for mechanical reasons (for example: a gap would help to avoid stress build up as a result of the contraction (shrinkage) of the weld during cooling.

Tanks.
Alexa

 

[pandithan]

Single bevel
kgp