Weld Cap Grinding

Date 09-06-2002 11:27

Grinding a flat top onto a weld will create a stress riser. If you grind a weld you should always round the edges. Is this what you need to know?? I apologize if I have misinterpreted your question.

Respectfully,
Mike Sherman
Shermans Welding

By TolgaKantaroglu (*)

Date 09-09-2002 06:35

Yes, actually I meant if you grind the weld cap properly without leaving any stress riser point what is the difference between the ungrinded and and the grinded one from strength point of view. By grinding do i decrease the strength of the weld?

Thanks

By TolgaKantaroglu (*)

Date 09-09-2002 06:37

Yes, actually I meant if you grind the weld cap properly without leaving any stress riser point, what is the difference between the ungrinded and the grinded one, from strength point of view. By grinding the weld toe do i decrease the strength of the weld?

Thanks

By pipewelder_1999 (****)

Date 09-06-2002 11:55

It is my opinion based upon what I have read and not actual testing that as the angle at which the toe of the weld enters the base metal decreases, the fatigue life increases. Therefore a flush cap would have an angle of 0 and no notches and greater fatigue.

It would be difficult to manually grind a cap flush and not reduce the thickness at the weld joint. But if this could be done, I can't imagine any detrimental effects on the weld.

One adverse effect of this would be a considerable increase in cost.

I hope this helps.

Gerald Austin
http://www.weldinginspectionsvcs.com

By TolgaKantaroglu (*)

Date 09-09-2002 07:07

Thank you for the answer. Thats what i considered. So it is understood that other than cost effect, there is no restriction on grinding the toe of the weld. But if you want to grind you should be careful not to decrease the thickness less then the material thickness.

Thanks.

By GRoberts (***)

Date 09-06-2002 14:40

As Gerald stated, the toe of the weld is what creates the stress riser. If you grind the weld completely flush, this increases the fatigue resistance of the weldment. If you happen to reduce the thickness of the base metal though, which is easy to do, it can reduce the strength of the weldment. Also, depending on what kind of steel you are grinding, if you grind it hard enough to introduce heat tint, it can cause other potential problems. If you are welding pen stock, could you chuck it in a lathe and turn it off?

By TolgaKantaroglu (*)

Date 09-09-2002 07:15

Actually it is not possible to chuck a 7.5m diameter penstock in lathe. But it is only possible to grind by grinding wheel.

Thank you for your kind reply.

Regards.

By R. Johnson (**)

Date 09-10-2002 12:51

The grinding marks left from the grinder need to be parallel to the direction of loading. Transverse grinder marks will reduce the fatigue strength and will fail sooner under cyclic loading.