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In my experience the original Volvo rotors and pads are quite OK, not prone to warping. Instead, you should suspect that a brake caliper piston is not doing its return stroke. Critical for this is the piston "seal" which in fact by its elasticity pulls back the piston a tiny bit, preventing the pad to keep contacting the disk when you have released the brake pedal. The seal ages and loses elasticity, the pad stays in contact with the disk, which heats up, more on one side, and the disk bends. When it cools down it returns to its original straight configuration, unless the condition has been going on for a long time. This should be expected to be the case if you feel no or only minor vibration during first brake after starting cold and immediately testing braking. In this case, changing rotors and pads or "turning" them is just a waste of time and money, unless you renovate the calipers first.
If you are short of money you can start by removing the pads and just cleaning out the calipers from pad abrasions, plain dirt, rust etc., because if lots of this is present it might be enough to prevent the pads moving away from the disk after braking. In several markets Volvo sells factory renovated calipers which are more economical to exchange, than renovating them yourself, you get a small refund when returning your old ones making the price less than the parts (pistons + seals) for renovating the calipers.
I was contemplating using the subject title "disk bullshit" or something, but donīt want to be too provocative. However, I feel that a discussion about disk warping which totally omits what I have discussed above is not really serious.
I bet someone now will get really upset, and start telling me/us about even more fancy materials. Please do, but it would be nice if some of the real Volvo techs here would comment.
Keep the spirits up, and happy motoring!
Gustafkalle
945 T+
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