Descaling: Removal of Heat-Treat Scale from Stainless Steels,

Several panels of 17-7 PH stainless steels were cleaned by various procedures and heat-treated to the TH 1050 condition. The cleaning procedre which proved to be the most effective in reducing the amount of scale and decreasing the nonuniformity of the scale was used for preparing all the samples for the subsequent tests. The cleaning and descaling solutions and procedures recommended by 8 different vendors were tested for scale removal properties, along with the effect produced on the base material. Other descaling solutions were developed and tested in the same manner as the vendors samples. Heat-treated PH 15-7 Mo stainless steel was descaled by the use of the procedure selected from these tests as the best for descaling 17-7 PH TH 1050 and examined for harmful effects. The preferred procedure for producing clean scale-free heat-treated stainless steel parts was to treat the parts by vapor degreasing, cleaning in a steel passivating solution, heattreating, conditioning the scale by an alkaline permanganate immer i n, and removing the scale in an acid descaling solution composed of a mixture of H2SO4, HNO3, HF and Na2Cr2O7. Author