Combined with the performance requirements and development direction of crusher lining material, a new bainite Martian multiphase wear-resistant cast steel with high strength, high hardness and qualified toughness is designed. The microstructure evolution law and performance regulation method during heat treatment are studied. By putting forward a multi-dimensional wear analysis method, the wear-resistant mechanism of experimental steel is explained, The theoretical research of experimental steel is industrialized, and the research conclusions are as follows:
(1) The composition system (wt.%): 0.37-0.40c, l.l-1.6si, 2.0-2.5mn, 0.003-0.006b, 1.2-1.5cr, 0.3-0.5mo, 0.04-0.06nb, 0.01-0.03ti ０．０１-０．０３Ｙ。 The laboratory smelting and casting process of Bei Ma multiphase wear-resistant cast steel is determined: melting of pure iron – adding alloy elements – adding modifier – tapping at 1500-1550 ° C – casting at 1450-1470 ° C – natural cooling.
(2) By studying the transformation law of bainitic Martian multiphase wear-resistant cast steel, the measured temperatures of AC1, AC3 and MS are 762 ° C, 843 ° C and 281 ° C respectively. The static CCT curve of bainitic Martian multiphase wear-resistant cast steel shows that its hardenability is good, and martensitic transformation can occur in the cooling rate range of 40 ° C / s-0.05 ° C / s, A certain amount of bainite can be obtained in the cooling rate range of 5 ° C / s-0.05 ° C / s.
(3) The quenching and holding temperature of bainitic Martian duplex wear-resistant cast steel directly affects the size of original austenite grain, martensite lath bundle and lath block, and has a hysteresis effect on the width of martensite lath. The quenching cooling rate seriously affects the content of bainite and martensite in the microstructure. In the microstructure dominated by martensite, Mn, s, C and Si compounds at the grain boundary seriously damage the toughness. In the microstructure dominated by bainite, large angle grain boundary and Y203 precipitates are beneficial to the toughness. Martensite has higher density of dislocation entanglement and finer lath structure, so the nano hardness is higher than bainite. The substructure at the bainite martensite interface is characterized by martensite twins between bainite laths.
(4) The optimum heat treatment process of bainitic Martian multiphase wear-resistant cast steel in the laboratory is 900 ° x2h air cooling or furnace cooling + 300 ° cx2h. At this time, the tensile strength is 1478mpa, the yield strength is 1233mpa, the hardness is 52.1hrc and the impact energy is 20.6j.
(5) In the two body pin disc wear test, the wear resistance of bainite Martian composite wear-resistant cast steel is nearly three times that of mnl3cr2; In the three body impact abrasive wear test, the wear resistance of bainite Martian multiphase wear-resistant cast steel is 38%, 99% and 246% higher than mnl3cr2 at 1J, 2J and 4J, respectively; In the three body impact abrasive wear test after salt spray corrosion, the wear resistance of bainite Martian multiphase wear-resistant cast steel decreased by 10%, 42%, 54%, 57% and 58% respectively after salt spray corrosion for 1h, 2h, 4h, 8h and 24h.
(6) A multi-dimensional wear analysis method is proposed to explain the wear-resistant mechanism of bainitic Martian multiphase wear-resistant cast steel. One dimensional wear analysis reveals the microstructure evolution and work hardening along the normal direction of the wear surface. The work hardening mechanism of bainitic Martian multiphase wear-resistant cast steel is twinning, high-density dislocation and residual austenite transformation, The work hardening mechanism of mnl3cr2 is dislocation entanglement and stacking fault.
(7) The two-dimensional wear analysis explains the wear mechanism on the two-body friction and wear surface. The two-body friction and wear forms of mnl3cr2 and Bei Ma multiphase wear-resistant cast steel are adhesive wear and abrasive wear respectively.
(8) The wear mechanism of three body impact abrasive wear surface is clarified by three-dimensional wear analysis. Strain fatigue, crack, furrow, embedded abrasive particles and extrusion accumulation are the main wear mechanisms of bainitic Martian multiphase wear-resistant cast steel. Embedded abrasive particles, furrow, strain fatigue, cutting, extrusion accumulation and spalling pit are the main wear mechanisms of mnl3cr2. The difference of wear mechanism is due to the difference of yield strength and initial hardness.
(9) Four dimensional wear analysis was used to study the wear behavior under the combined action of salt spray corrosion and impact abrasive wear. The wear mechanism of low-level corrosion samples is still characterized by furrow, strain fatigue and embedded abrasive particles, and the deformation zone of wear subsurface is narrow. After that, with the extension of salt spray corrosion time, the furrow becomes shorter and deeper, the wear weight loss increases, the wear subsurface deformation zone of the sample disappears, and the wear resistance of the material deteriorates. A theoretical formula is established to estimate the wear weight loss of bainitic Martian multiphase wear-resistant cast steel under the synergistic action of salt spray corrosion and impact abrasive wear.
(10) A set of bainitic Martian multiphase wear-resistant cast steel lining plate was trial produced. The heat treatment parameters for industrial production were determined as 910 ± 10 ° C, heat preservation for 5h, forced air cooling, tempering at 310 ± 10 ° C for 8h and air cooling. The microstructure and properties of the trial produced liner meet the index requirements, and the overall mechanical properties and wear resistance of the liner are uniform. After industrial application, the service life reaches 209 hours and 51 minutes, more than 50% of the average service life of the domestic liner currently used.