High plasticity, high tenacity and ultra-high tensile steel, and manufacturing method thereof

Abstract

The invention discloses a steel with high plasticity, high toughness and high strength and a manufacturing method thereof. The chemical compositions of the steel are as follows in terms of weigh percentage: 0.15 to 0.30 of C, 0.20 to 1.40 of Mn, 0.10 to 0.50 of Si, less than or equal to 0.015 of P, less than or equal to 0.012 of S, less than or equal to 0.20 of Ni, 0.40 to 1.50 of Cr, 0.25 to 1.35 of Mo, 0 to 0.10 of V, less than or equal to 0.2 of Cu, 0.01 to 0.05 of Al, 0.0005 to 0.0020 of B, less than or equal to 0.010 of (O+N) and the balance of Fe and impurities. The manufacturing method comprises the following steps: smelting according to the formula, continuous casting into a blank, hot rolling into plates or tubes, quenching at the temperature of 875 to 930 DEG C and holding the temperature for 25 to 40 minutes, tempering at the temperature of 625 to 675 DEG C for 30 to 90 minutes, then air cooling, and quenching and tempering heat treatment. The steel has yield strength of more than or equal to 1000MPa, tensile strength of more than or equal to 1100MPa, zero-degree-centigrade charpy impact work of more than or equal to 100J, specific elongation of 20 to 30 percent and is applicable to manufacture important structures of engineering machinery, high buildings and oil well pipes, and the like.

Description

technical field [0001] The invention relates to a method for manufacturing ultra-high strength steel, in particular to a composite phase characterized by the formation of clean ultra-fine tempered lath martensite in the steel and dispersed nano-scale precipitates Microstructure, and thus obtain a high-performance, low-cost steel material manufacturing method with various mechanical properties such as ultra-high-strength steel, high plasticity and high toughness. Background technique [0002] At present, steel materials are still the main body of structural materials. The development of high-performance steel materials and their key manufacturing technologies with multiple characteristics such as ultra-high strength, high plasticity and excellent low-temperature impact toughness is the key to meet the needs of large-scale construction machinery and high-rise buildings. It is an important way for modern important structures such as oil well pipes and harsh geological service e...

AI Technical Summary

Problems solved by technology

For example, the ultra-high-strength steel plate disclosed in the international patent "Weldable High-Strength Steel with Excellent Low-Temperature Toughness" (publication number CN1146784A), through the use of micro-alloying combined with controlled rolling, although the tensile strength of the material has reached more than 950 MPa, it is tough and brittle. The transition temperature is below -85°C, but the relevant claims and examples do not mention the elongation data of the material, which shows that the patent does not put forward plasticity index requirements for the disclosed ultra-high-strength steel; another example is the domestic patent "Petroleum Although the yield strength and tensile strength of the material can reach above 966-1103MPa and 1034MPa respectively, the ultra-high-strength casing disclosed in "Petroleum Casing and Production Method for Mid-Deep Well and Ultra-Deep Well in Natural Gas Exploitation" (publication number CN1619005A) The dimensional impact energy is over 40J, but the relevant claims and examples do not mention the elongation data of the material, which shows that the ultra-high-strength steel disclosed in this patent does not put forward requirements on the plasticity index

[0006] 2) Although the disclosed ultra-high-strength steel has achieved high plasticity, its low-temperature impact toughness is obviously insufficient

For example, a low-alloy ultra-high-strength steel disclosed in the domestic patent "Low-alloy ultra-high-strength steel" (publication number CN1390972), the yield strength and tensile strength of the material can reach 860-1200Mpa and 1000-1300MPa respectively. The rate is 15-25%, but the full-scale low-temperature impact energy at 0°C is only ≧33J

[0007] 3) The plasticity and low-temperature impact toughness of the disclosed ultra-high-strength steel are insufficient

For example, a kind of ultra-high-strength steel disclosed in the domestic patent "Ultra-high-strength anti-collapse oil casing with special connection structure and its production method", although its yield strength and tensile strength can reach 896-1150Mpa and ≧970MPa respectively, but the extension The efficiency is only ≧9%, and the full-scale low-temperature impact energy at 0°C is only ≧33J

[0008] 4) Although the disclosed ultra-high-strength steel also achieves high low-temperature toughness, it may also achieve high plasticity, but the cost of the alloy is relatively high

But there is a problem: either the strength is insufficient, or the low-temperature impact toughness is insufficient. Similarly, they are not high-performance economical steel materials that combine ultra-high strength, high plasticity, and excellent low-temperature toughness.

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