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Effect of heat treatment process on the corrosion behavior of plastic mold steel P20

in recent years, plastic products have been more and more widely used in industry and people's daily life, which has promoted the rapid development of China's mold industry. At present, China's plastic molds have occupied the primary position in the total output value of the whole mold industry. The demand for plastic mold steel is increasing. As the most widely used plastic mold steel at home and abroad, plastic mold steel P20 (3Cr2Mo) has excellent wear resistance, polishability, machinability and thermal conductivity. Software operation characteristics:. The plastic mold will be injected with softened plastic at 200-300 ℃, and the corrosive gas containing chlorine, fluorine and their compounds released by these substances will have a certain corrosive effect on the mold cavity. For this reason, the researchers further studied the corrosion resistance of P20 steel. Through electrochemical test, weight loss test, neutral salt spray test and immersion test, the corrosion resistance of P20 steel treated by different heat treatment processes in 0.5mol/l NaCl solution was studied. The corrosion morphology was observed and analyzed by SEM, EDS, XRD and metallographic microscope, and the corrosion mechanism of P20 steel through the superposition and analysis of group experimental curves was explored, Thus, a heat treatment process of P20 steel that meets the requirements of mechanical properties and has good corrosion resistance is found

the results show that:

(1) the corrosion resistance of Bainite/Martensite Duplex structure obtained by air cooling at 860 ℃ and single-phase martensite structure obtained by oil cooling at 860 ℃ are better than that of ferrite obtained by oil cooling at 785 ℃/if the front windshield Martensite Duplex structure is made of transparent resin

(2) after tempering at 450 ℃ and 620 ℃ respectively, the samples with Bainite/martensite and martensite structure decompose, a large number of carbides precipitate, the self corrosion current density is large, and the corrosion resistance decreases

(3) after the electrochemical test, the corrosion products on the surface of the sample are divided into two layers, the outer layer is relatively loose, the main component is FeOOH, the inner layer is relatively dense, mainly Fe3O4, the anodic reaction is the dissolution of iron, and the cathodic reaction is the hydrogen evolution reaction

(4) the pitting corrosion of P20 steel in 0.5mol/l NaCl solution is centered on inclusions, and the surrounding matrix is continuously corroded. The longer the corrosion time is, the more serious the pitting corrosion is

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