37results about How to "Prevent re-precipitation" patented technology

The invention provides austenitic stainless steel as well as a preparation method and application thereof, and relates to the field of high-temperature-resistant austenitic stainless steel. The austenitic stainless steel comprises the following chemical components in percentage by weight: less than or equal to 0.10% of C, less than or equal to 0.12% of N, less than or equal to 2.0% of Si, 1.0-2.0% of Mn, 16.0-18.0% of Cr, 10.0-14.0% of Ni, 2.0-3.0% of Mo, 0.05-0.10% of Nb, 0.05-0.10% of Ti, less than or equal to 0.02% of S, 0.04-0.06% of P and the balance of Fe and inevitable residual elements. The content of P in the stainless steel is increased, the diffusion rate of solute atoms such as Cr and Mo can be reduced through interaction of P and vacancies at the high temperature, nucleation of M23C6 carbides and the like at the grain boundary is inhibited, the precipitation number is remarkably reduced, meanwhile, P is discharged outwards in the coarsening process of the M23C6 carbides, a core-shell result that the M23C6 carbides are wrapped by the P element is formed, the coarsening rate of the M23C6 carbides is reduced, and the corrosion resistance of the stainless steel is improved. Furthermore, a creep cavity caused by a precipitated phase in the creep process is inhibited, and the creep fracture strength is improved.

The invention discloses a chlorhexidine gluconate solution and a preparation method thereof. The method comprises the following steps: dispersing chlorhexidine free alkali in purified water, introducing carbon dioxide, pressurizing and carbonizing, and constructing a homogeneous or quasi-homogeneous reaction system; adding gluconic acid-delta-lactone under the condition that the system pressure is not lower than 0.30 MPa, maintaining the pressure, carrying out constant-pressure stirring reaction, and inhibiting carbonic acid decomposition by utilizing back pressure so as to match lactone hydrolysis kinetics; and after the reaction is finished, carrying out gradient pressure relief, vacuum degassing and filtering. According to the present invention, the gas-liquid-solid three-phase coupling and the variable pressure-pressure maintaining delayed release process are adopted, such that the low-temperature total synthesis of chlorhexidine is achieved, the generation of parachloroaniline impurities and the discoloration of the product caused by the high temperature are effectively avoided, and the technical problems of incomplete reaction and easy muddy reaction at the low temperature are solved. The process has the advantages of no residue, high product purity and good safety.