Preparation method of low-alloy high-carbon steel with high-strength and high ductility nano structure

Abstract

The invention discloses a preparation method of a low-alloy high-carbon steel with a high-strength and high ductility nano structure, which is characterized in that the steel contains the following chemical components in percent by weight: 0.7-0.9 percent of C, 1.4-1.6 percent of Si, 1.2-1.4 percent of Mn, 1.4-1.6 percent of Al, 0.7-0.9 percent of Cr, 0.7-0.9 percent of W, less than 0.02 percent of P, less than 0.02 percent of S and the balance of Fe. The preparation method comprises the following steps: melting the chemical components according to the weight percent, pouring to form a steel ingot and slowly cooling to the room temperature; heating the steel ingot to 1,160-1,180 DEG C, cogging, and hot rolling to form a plate blank with the thickness being less than 25 mm, wherein the finally rolling temperature is 990-1,010 DEG C; rapidly putting the plate blank into a salt bath with the temperature of 220-260 DEG C after the rolling, and keeping the constant temperature for 4-24h, and then cooling in the air to the room temperature to obtain the low-alloy high-carbon steel with a high-strength and high ductility nano structure, wherein a microstructure comprises bainitic lath ferrites with the thickness of 60-90 nm and residual austenite and has the tensile strength of 2,000-2,300MPa, the yield strength of 1,500-1,900MPa under the condition of 0.2 percent of strain, the total elongation percentage of 6.7-7.8 percent and the uniform elongation percentage of 3.8-5.6 percent; and the Charpy measured by the ASTM:E23-02 standard, i.e. room-temperature impact work of a U-shaped notch specimen, is 7-22J. The invention has simple preparation process, direct constant temperature process in the salt bath after the hot rolling, short period of thermal treatment, low cost and easy application in production.

Description

technical field [0001] The invention relates to a preparation method of high-strength steel, in particular to a preparation method of high-strength, high-toughness nanostructure low-alloy high-carbon steel. Background technique [0002] The strength of steel, which is widely used as a structural material, increases with the increase of carbon content, but its toughness and plasticity decrease. How to realize the synchronous improvement of the strength and toughness or plasticity of steel has become an important issue to improve its performance and tap its potential. [0003] Traditional low-alloy high-carbon steel is generally used to manufacture cutting tools, measuring tools and cold-working molds. The enhanced heat treatment process is mainly quenching + low-temperature tempering. After heat treatment, a tempered martensite structure is obtained, which has high strength and high hardness, but its Low toughness and plasticity. If the tempering temperature is increased, a...

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Problems solved by technology

The highest tensile strengths of these two alloy steels obtained by isothermal transformation at 200°C are 2200MPa and 2300MPa respectively, the corresponding total elongations are 4.7% and 7.6%, and the yield strengths are both 1400MPa. When the isothermal temperature is increased to 300°C, the two alloys The tensile strength decreased to 1800MPa and 1700MPa respectively, the yield strength decreased to 1300MPa, the total elongation increased to 29% and 27%, and the tensile curve had no obvious work hardening and necking (ISIJInternational, 2005, Vol.45, p. 1736), indicating that its overload safety is not good

Co, Ni, Mo, V elements are added to the above alloy steel, which will undoubtedly increase the production cost, and the casting defects will remain without thermal deformation of the ingot, resulting in a decrease in performance

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