Hardening problem
Hardening problem
(OP)
We have a very large built up girders that had some large holes drilled into the flanges which are 3" plates, A572, Gr. 50 steel. The problem we are running into is that these holes that were drilled into the flanges were too big and revised to a smaller size. So now after fit up of the girder, including pre heating of the flange and web for welding, we are filling up the holes and when we try to re-drill the hole our drill bit is unable to do so. Any ideas why this is occuring and what can we do to prevent this or even fix it? Our guess would be hardening has occured through the preheating process along with welding of the web to flange with sub arc, and now after filling the hole even more heating up and cooling down has occured. If anyone has any ideas let me know. Thanks everyone!





RE: Hardening problem
A sharp cobalt-steel drill bit should be able to drill it. How high was the preheat?
"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein
RE: Hardening problem
RE: Hardening problem
What filler metal did you use and what temperature did you preheat to?
Bob
RE: Hardening problem
RE: Hardening problem
"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein
RE: Hardening problem
Just an observation and take this advice for what it is worth – nothing. I have a fundamental problem with your approach because you are letting tooling dictate a solution to your problem. First - you are welding on HSLA structural steel which requires a qualified welding procedure. Preheat requirements should have been spelled out. Presuming you have a qualified welding procedure, modifying the filler metal to accommodate a "softer" filler metal is not going to happen.
Suck it up and use the appropriate drill bits or tooling for drilling correctly placed holes. I have been down this path before and this is the correct approach. Attempting to modify welding on critical structural members to allow use of existing drill bits makes no sense. Local PWHT may adversely affect the base metal properties of the HSLA steel.
RE: Hardening problem
RE: Hardening problem
I couldn't agree more with what you said, but the man with the money makes the rules and my boss wanted to go in a different direction. I don't agree with it but I figured i'd try to get the informtation I could about other routes to take. But thank you for your advice.
RE: Hardening problem