Effects of Aging Temperature on Pitting Resistance of Steel for Air Conditioning Pipes

The effect of aging temperature on the microstructure, mechanical properties and corrosion properties of steel for air conditioning pipes was studied by microscopic morphology observation, mechanical property test, electrochemical test and 6% FeCl₃ solution immersion test. The results showed that when the aging temperature was 350-535 ℃, the microstructure of the sample was martensite+residual austenite, and when the aging temperature was 625 ℃, the reverse austenite was formed. With the aging temperature increasing from 350 ℃ to 625 ℃, the tensile strength, yield strength and elongation after fracture of the sample increased firstly and then decreased, and the reduction of area and impact energy firstly decreased and then increased. When the aging temperature was 350 ℃, the sample had high strength and plasticity, good toughness (tensile strength 1 420 MPa, elongation after fracture 16.2%, impact energy 85 J) and high pitting resistance.