EFFECT OF MATERIAL PROPERTIES AND SURFACE TREATMENT ON THE PERFORMANCE OF STAINLESS FLAPPER VALVE STEEL FOR COMPRESSORS

摘要

Suction and discharge valves are components critical to the function of a compressor, which must work reliablyunder conditions of high cyclic stresses from bending and impact. The allowable bending stress and impact velocityfor the valve material are limiting factors for the compressor designer and it is thus of interest to compressormanufacturers to maximize the fatigue strength of the valves.This paper describes fatigue testing that has been performed on a martensitic stainless valve steel (modified AISI420) that is commonly used in compressors.Strip steel samples with different static mechanical properties, which were given three different surfacetreatments (untreated, tumbled, and tumbled + shot-peened) were investigated. The samples were tested for bending-and impact fatigue properties and the results are given in the paper.It was found that suitable surface treatments could give rise to very favorable residual stress states in thematerial, which led to very good fatigue testing results, particularly for some of the samples, which had a highertensile strength. Material with increased fatigue strength in bending and impact can offer significant designadvantages for future compressor designs leading to higher efficiency and reliability, as well as the possibility todesign smaller compressors. This is of particular interest to CO2-compressors using a high discharge pressure.