I just ran a B31.3 model on the same version of CAESAR II as you. Low Chrome Moly (LCM) has no allowable stress and no yield stress. All my stress reports show zero allowable.
My guess is that your material database now has the allowable limits you wish to ignore. You can go into the material database editor and "delete" an entry -- you will not delete anything -- but by requesting "delete", the program will show all materials that have been added to your database. Is LCM shown? If so, that's where the data is coming from.
I must ask... Is this material (LCM) used elsewhere in the model? If not, go ahead and type in zero for all the stress limits when you first specify LCM, that should remove the stress checks.
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Dave Diehl