A method for determining the kinetic curve of carbide isothermal precipitation

Abstract

The invention discloses a method for measuring an isothermal precipitation kinetics curve of carbide. The method comprises steps as follows: 1) compressed yield stress values of a to-be-tested part at set isothermal temperatures and at isothermal time are acquired through a thermal simulated test machine; 2) effective precipitation coefficients feff used for representing a relative quantity of a precipitated phase effectively strengthened in the precipitation process are acquired according to the strength increment delta sigmate y and the largest strength increment delta sigmate y, max of the compressed yield stress values relative to the smallest compressed yield stress value, and feff is equal to the quotient obtained by dividing delta sigmate y, max by delta sigmate y; 3) the precipitation kinetics curve of the carbide in the isothermal process is drawn according to corresponding relations of the effective precipitation coefficients, the isothermal temperatures and the isothermal time under various isothermal conditions. A measurement parameter adopted in the method is the compressed yield stress, the strengthening function of isothermal precipitation is directly reflected, the practicability is high, the method can be directly used for process improvement, data are more visual, sensitive and accurate, and operation is simpler, more convenient and more effective.

Description

technical field [0001] The invention relates to a method for measuring a carbide isothermal precipitation kinetic curve, which belongs to the technical field of thermal processing of metal materials. Background technique [0002] The newly developed high-strength low-alloy steel (HSLA steel) controls the uniformity of nano-scale micro-alloy carbides in the grain boundary and matrix by adding micro-alloying elements such as Nb, V, and Ti, and combining controlled rolling and controlled cooling processes. Precipitation to achieve grain refinement and precipitation strengthening of steel. Therefore, determining the precipitation kinetics of carbides in steel is very important in production practice. [0003] At present, there are few studies on isothermal precipitation kinetics, and commonly used methods include transmission electron microscopy (TEM) analysis, physicochemical phase analysis, and stress relaxation methods. However, the TEM analysis method is limited by the obs...

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Problems solved by technology

However, the TEM analysis method is limited by the observation range of precipitates, the sample error is relatively large, and the sample preparation takes a long time; the physical and chemical analysis method cannot detect the fine second phase below 12nm, so the sensitivity is not high, and the operation is cumbersome and time-consuming. Although the stress relaxation method is simple, it is difficult to carry out quantitative analysis. In many microalloyed steels, the obvious stress inflection point cannot be measured, and the adaptability is not high.

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