suggetion regarding project

Hollo sir,
greetings from kedar patil final year mechanical engg student from tkt warananagar kolhapur ,india. my final year project is flatness of disc . in my project i have one problem .when we assembled disc and rim by welding the flatness value of disc inceases up to 0.9-1.1mm.but we design the disc whoes flatness value up tp 0.3mm.so i want suggesion to over come this problem. can i use under water weldig techniqe here? to minimise the distortion. i am very much hopeful that you will give me a proper soluton.
thank you.