Peter...
Working backwards, universally Cap Screws [SHCS] and their cousins are marketed by Grade or tensile strength
For the Steel Industry [in Australia] for impuslive applications Grade 12.9 is specified, for lower stressed applications Grade 10.9.. then to General bolts of Grade 8.8 these are produced from varying steel melts of differing chemical composition
300 Series stainless steels have higher Nickle content so therefore corrosion resistance is markedly increased, however at the loss of tensile properties
So no, using high tensile carbon steel [blackened Oxided] SHCS of Grade 10 9 or 12.9 is due to a requirement of strength, ......in that a specified
size SHCS torqued to the recommended value will maintain the induced torque without stretching or failure
A 300 Series stainless steel SHCS to attain the lockdown strength requirement of the application would need to be of
larger diameterThere are Engineering Standards to define the Grade of carbon steel fastner be they hex head or SHCS....these are by numeral or line marking in a pattern and stamped into the head of each and every bolt
I am not aware of any universal Engineering Standards used to define by
physical marking by Grade of stainless steels
So in an earlier life
I spent many years supervising electro/hydraulic maintenance of US built Gun Mounts & Missile Launchers for our Royal Australian Navy.........the subcomponents in the hydraulic systems were secured with High Tensile SHCS with a gold or black phosphated surface finish........this surface treatment was post product heat treatment and to improve corrosion resistance......
It was not unknown for smallish ~~~~5/16"x32 UNF SHCS to shear the heads literally with the sound of pistol shots when a component was pressurised........yes the secondary process of phosphating with an
incorrect heat value negated the previously attained mechanical strength by the initial heat & quench process
Derek