risky heating

[ajn22anellie]

I am working with a company that is welding grade 80 plates into very long tube sections. They use four grade 80 plates (20" x 30') and weld them into a box. The plates come precut from a vendor, and occasionally the plates are warped or bent. Also, more bending occurs during welding. To straighten the tubes after welding they heat the tube sections at different points and then air cool. This does a good job of relaxing the tube and straightening things out, but I am worried they are compromising the structural integrity of their grade 80 plate? Am I correct? Is there a way of estimating the effect of heating the plates (change in E or YS?)?

 

[unclesyd]

What is he complete specification for your plate?
What condition is received in ?
Is the person doing the heating straightening well versed in the art?
Are you welding at four corners?

Normally straighten warped steel you don't use enough heat to affect the physical properties. This is especially true if you are air cooling. Also any change would be less than what you see in the HAZ of the weld.

Her is a very good inexpensive book by Omer Blodgett that has section on controlling distortion.

https://ssl.lincolnelectric.com/lincoln/apdirect/item.asp?prodnum=DW

 

[metengr]

To straighten the tubes after welding they heat the tube sections at different points and then air cool

To what temperature??

 

[ajn22anellie]

The plate is heated until red hot. I don’t know the specific temperature. A plate could have as much as ½” of sweep – shaped like a banana. To bring the plate square the outside of the banana is heated to red hot in a few places (3” square) and then air cooled. The gentleman doing the heating is versed in the art, but has no formal education. I am most nervous when he heats the entire width of the plate. I would think that heating Grade 80 (YS of 80ksi) would weaken the plate, especially in an uncontrolled environment. Any thoughts?

 

[metengr]

I would think that heating Grade 80 (YS of 80ksi) would weaken the plate, especially in an uncontrolled environment. Any thoughts?

Here are my thoughts - uncontrolled heating (no specified maximum temperature range, no specified ramp up or cool down or procedure to document this activity) results in unpredictable mechanical properties to the Grade 80 base material.

 

[hogan666]

this link may be of some help

http://isddc.dot.gov/OLPWeb.ASP?WCI...number) LIKE '%IF-99-004%'&fr=1&lr=1&rc=1&WCU