Copper Precipitation Mechanism And Performance Control Of Ferritic Antibacterial Stainless Steel

Antibacterial stainless steel, as a combination of structural and antibacterial functional materials, greatly broadens the application of antibacterial material. Low-cost ferrite antibacterial stainless steel, in particular, can be widely used in metal antibacterial products, such as household appliances, kitchen utensils and sanitary ware. Hence, the development and application of excellent antibacterial stainless steel would bring huge economic benefits and social value.This paper adopt ultra purification design, addition of niobium and titanium stabilizing element, high chromium low nickel, and 1.5wt% copper into the steel. It successfully developed a ultra pure ferritic antibacterial stainless steel, with a good cooperation from antibacterial properties, mechanical properties, formability and corrosion resisting property.It simulated the influence of heating temperature and time, as well as deformation temperature and rate on hot shortness sensitivity of the tested steel through the hot tensile test. The results show that, it led to the largest hot shortness sensitivity at heating temperature of 1150℃, heating holding time of 60 min, deformation temperature of 1150℃ and medium deformation rate of 10-2 s-1, respectively. It was believed that hot shortness was the result of partial poly of copper element. The thermal deformation equation of the tested steel was obtained ε= 5.81×1013sinh(ασ)4.6825exp(-(323000)/RT) by hot compression experiment. The processing map was established by coupling the figures of energy dissipation and rheological instability.Antibacterial process plays an important role in copper precipitation behavior. With antibacterial annealing temperature increment and annealing time extension, the shape of precipitated phase changed from the ball to rod, while the size and average spacing of precipitation increased. Copper precipitated phase and ferritic matrix exists with K-S relation:(111)ε-Cu//(110)α-Fe.Fe,[110]ε-Cu//[111]α-Fe. Antibacterial annealing process should be conducted after solid solution treatment. It got the best antibacterial properties when the antibacterial annealing temperature was 800℃. The antibacterial rate increased with the extension of the annealing time and antibacterial rate was over 99%, when annealing time was for 1 h. The precipitated phase number and size achieved the critical value to obtain good antibacterial properties, respectively (54.1±2.0) nm å'Œ 173/100 μm. The volume fraction of copper precipitated phase should to be more than 0.77%. Precipitated phase size and number of precipitated phase per unit area also played an important role in antibacterial properties.The start temperature of copper precipitated phase is 926℃ and the volume fraction is about 0.775% through thermodynamic software Thermo-calc simulated. The theoretical calculation was conducted in process copper precipitated phase precipitated in tested steel, according to the misfit dislocation theory. And nuclear rate-temperature curve (NrT) curve and the precipitation phase transformation kinetics curve (PTT curve) was got. Ostwald ripening process of copper precipitated phase was characterized. Ripening rate was m=(8σVpDc0)/(9cpRT)1/3 and measured average size of precipitation was rt= 2.46t1/3.Cu-rich phase evolution with different ageing time has been characterized through the analysis of atom probe tomography(APT). As the aging time extended, the size of copper precipitated phase increased gradually, while the number density decreased correspondingly. During the precipitated phase growing up process, Mn and Ni element gathered at the surface of the precipitated phase. The antibacterial mechanism of the precipitate phase was discussed from the macroscopic and microscopic level.Average plastic strain ratio rm and anisotropic index â–³r was measured by the tensile test, and the relationship with antibacterial annealing temperature and time, and micro texture was investigated. The pitting corrosion resistance was tested by potentiodynamic polarization curve. With the increase of annealing temperature and extension of annealing time, pitting potential of test steel declined. The greater size of antibacterial phase leads to the worse pitting corrosion resistance of the material.