First, the HR person will contact you to go over you resume and ask you some generic questions about how you handle stress, difficult situation, etc. More or less the same questions everybody else asks you.
Second, they go over you salary history and willingness to relocate, etc. This will be the end of the phone interview.
Third, If they like you and you are in the salary range, they will probably give you call after 1-2 months to set up a group interview with people from other departments. Once you are there, the interview might take 4-6 hours including the plant tours and lunch. Most of the questions are situational and little stressful, but ok.
Fourth, once all the candidates have been interviewed, the hiring group will go over each applicant's qualifications and salary requirements and select 1-2 candidates to recommend to that department's director for final approval.
I learned that IR has a tendency to hire people that did not participate in the hiring process and were hired mostly because they knew or is related to somebody higher up in IR. This sucks if true.
Overall, their hiring process is very slow and weak. If you don't fit their criteria, they will not ever bother to send you a thank you note or something like that. If you call to follow up they will tell you they are still interviewing, even if the position has already been filled.