I'm looking for a strength vs. temperature graph or table for A612 steel. I couldn't find any reference.It would be a much help if any of you guys can help me with this.
That depends on what you mean by "strength" and your code/application.
Assuming this is for a ASME BPVC vessel: Section II Part D gives your allowable stresses, and you would use Table 1A for most applications (Sec VIII Div 2 and Sec IV use different tables). I've given them below:
If for some reason you are want yield strengths, those are in Table Y-1. Here they are:
What is going on at "Chemical engineers" threads sections? Why here and in the neighborhood topics are being discussed where is no a word relevant to "chemical"?
Mech and petro engineers, go home!