How can we delete materials permanently from Material master?

Use transaction MM70 - Material Master->Other->Reorganization->Material->Choose.
Build variant with selection range of material master records to be selected for deletion and maintainrun parameters.Execute.
Use transaction MM71 - Material Master-> other-> Reorganizationn-->Material->Reorganization
Build a second variant, Maintain run parameters and execute.
It is also important to remove the records manually from info record, POs, PRs, reservation etcfor successful deletion of the material.