Hi Rohit,
For special stocks, material type settings are not considered
If this is your scenario for all processes associated with account assignment category Q
then you can remove Goods receipt check box from account assignment category Q
MM>PUR>A/C ASSIGNMENT>Q
With this there will not be stock posting on GR and only consumption account will be posted for WBS
If You don't want to change standard settings for Q then you can copy and create new
But you will need to maintain account determination for this new cat
Thanks
DD