An assessment of residual stresses on 316LN SS machined plates by hole-drilling strain-gage method

Type 316LN stainless steel (SS) is used as a major structural material in the construction of fast breeder reactor (FBR) in India. For fabrication of various components from thick 316LN SS plates, extensive machining is often necessary. It is known that machining can introduce residual stresses in the components and can affect the dimensional stability of the components in service at high temperature of 550°C (823 K). For this, the effect of machining on the residual stress distribution was studied on type 316LN SS plate material. The residual stresses introduced in the plate surfaces by two different machining sequences are measured and compared with the residual stresses present in the plate before machining. The residual stresses were measured by hole-drilling strain gage method. The residual stresses in the as-received 316LN SS plate are found to be compressive in nature. However, the machined 316LN SS plates shown tensile residual stresses transverse to the machining direction and compressive residual stresses along the machining direction.