Lamellar Tearing

[ajk1]

I have a detail of welding a plate to the edge of an existing 26x4x26" A33 steel base plate to transmit a 25 kips factored horizontal force to the base plate. The force would be parallel to the plane of the base plate. Is lamellar tearing a concern? If so, what should be specified for the testing?

 

[kingnero]

if 4" is the thickness of the baseplate, and there is a substantial amount of welding to be done to the top surface of the plate, then yes, lamellar tearing is an issue.
Specify steel with a minimum elongation in the Z-direction (thickness) of 25 or 35%.
Sulphur is the main culprit here.

 

[ajk1]

To kingnero - there is no welding to be done on the the top surface of this 60 year old base plate. The only welding is the the vertical edges. The new force is applied in the plan X and Y directions. Is there any lamelar tearing issue in this case? Since the plate to be welded to is existing, I cannot specify the properties of that.

 

[kingnero]

No, I don't think there will be a problem in that case

 

[ajk1]

OK, that is my belief as well. Thanks. Much appreciated.

 

[dhengr]

Ajk1:
Lamellar tearing is usually caused by loads in the ‘z’ direction w.r.t. the plane of the plate which is the ‘x - y’ plane. This may be actual loads, vibrational loading and the like, or high residual stresses caused by welding of a highly restrained joint or piece. The plate has slightly lower mechanical properties in the ‘z’ direction than in the plane of rolling, the ‘x - y’ plane, because of the orientation of the grain. And, heavy rolled sections can have high residual stresses of their own due to the cooling process during hot rolling. Furthermore, impurities, slag inclusions and the like, tend to be oriented in the plane or direction of rolling, and end up causing weak planes in the plate, in the plane or direction of rolling. These weak planes would be perpendicular to a tensile loading in the ‘z’ direction. Your application has the weld and load being applied parallel to a potential lamination. In the case of rolled shapes, these imperfections are called ‘piping’ I believe, and tend to be squeezed to the area of the juncture of the flange and the web. The way we normally design and use plates and structural shapes has the primary stresses and any weak planes (laminations) running parallel to each other, so the stress fields just flow with and along/around the weak planes, not perpendicular to them.

 

[ajk1]

To dhengar - Thanks for the explanation. Very interesting.You must be a professor of engineering, or have a good memory of what we were taught in school.

 

[Ron]

ajk1....good explanation by dhengr. To expand slightly, the planar weakness is due to an incomplete metallurgical bond, parallel to the rolling direction. Welding sometimes causes these laminations to show as delaminations. Stress perpendicular to the lamination anomaly, as dhengr explained, can cause them to separate as well.

After welding, have the plate tested by ultrasonic NDT....this will show any separations that exist, either in the parent metal or in the heat affected zone from welding.

I don't think you'll have an issue unless there are lamination anomalies that currently exist in the plate.

 

[ajk1]

ok,thanks Ron. Is there any particular thickness of plate at which this become a concern, or is it independent of the late thickness?