Thanks RP, we have chosen 1080 as forging temp based on previou trial but as you said they are nearly in the same range. what you think about forging temp?
There are many factors that affect the optimal forging temperature, so I'd have to say if your trials indicate that 1080 works best for you, I am not sure what you are asking. My experience with forgers is they will always use as high a temperature as they can (plus a little bit, if they can get away with it), so that temperature does not surprise me.
My point was that the heat treating temperatures you posted appeared to include a homogenizing treatment, which may not be needed considering the heating cycle you use for forging. In many circumstances, a homogenizing treatment is beneficial for this alloy, which is likely why your customer has specified it. If you have a history of processing this material that indicates this treatment is not necessary, you can often negotiate with the customer, using this experience in support of your position. As metengr
points out, many manufacturers/users will appreciate this feedback, particularly if it improves their specifcations. However, if you try to support your position by information found on an internet message board, you may not be taken too seriously.