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Ultrahigh-strength high-toughness multistep isothermal bainite steel and preparation method thereof

An ultra-high-strength, bainitic steel technology, applied in the field of ultra-high-strength steel, can solve the problems of insufficient plasticity and toughness, insufficient tensile strength, and high alloying elements, and achieve increased toughness and plasticity, increased strength, and volume stability. Good results

Active Publication Date: 2014-02-05
WUHAN UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in these bainite steels, in order to ensure the bainite isothermal reaction at a lower temperature (200~300°C), it is usually necessary to add high carbon content to reduce the bainite finish and martensite start temperature, while high Carbon content often has a very negative effect on toughness, and the production cycle is relatively long
[0008] From the above analysis, it can be seen that the existing ultra-high-strength and high-toughness steels are either slightly insufficient in tensile strength, or insufficient in plasticity and toughness, or high in cost due to high alloying elements

Method used

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  • Ultrahigh-strength high-toughness multistep isothermal bainite steel and preparation method thereof
  • Ultrahigh-strength high-toughness multistep isothermal bainite steel and preparation method thereof
  • Ultrahigh-strength high-toughness multistep isothermal bainite steel and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] An ultra-high-strength, high-toughness multi-step isothermal bainite steel and a preparation method thereof. After molten iron is made and refined, die casting or continuous casting is carried out, followed by hot rolling. First austenitize the hot-rolled steel slab at 850-1000°C for 0.5-5.0 hours, and then perform bainitic multi-step isothermal transformation to obtain ultra-high strength and high toughness multi-step isothermal bainitic steel.

[0031] The multi-step isothermal transformation of the bainite is transformed into a two-step isothermal transformation: the first step is kept at 350-450°C in a salt bath for 0.2-1.0 hours, and the second step is kept at 250-350°C in a salt bath for 2-30 hours .

[0032] The ultra-high strength and high toughness multi-step isothermal bainite steel prepared in this example: the tensile strength is 1500~1800MPa; the hardness is 450~550HV; the elongation is 15~25%; the impact toughness is 45~60J / cm 2 .

Embodiment 2

[0034] An ultra-high-strength, high-toughness multi-step isothermal bainite steel and a preparation method thereof. After steelmaking and refining, the scrap steel will be die-cast or continuous-cast and hot-rolled. First austenitize the hot-rolled billet at 950-1100°C for 0.2-4.0 hours, and then perform bainitic multi-step isothermal transformation to obtain ultra-high strength and high toughness multi-step isothermal bainitic steel.

[0035] The multi-step isothermal transformation of the bainite is transformed into a two-step isothermal transformation: the first step is kept at 250-350°C in an inert atmosphere for 1.0-3.0 hours, and the second step is kept at 220-300°C in an inert atmosphere 10~50 hours.

[0036] The ultra-high strength and high toughness multi-step isothermal bainitic steel prepared in this example: the tensile strength is 1500~1800MPa; the hardness is 450~550HV; the elongation is 15~25%; the impact toughness is 45~55J / cm 2 .

Embodiment 3

[0038] An ultra-high-strength, high-toughness multi-step isothermal bainite steel and a preparation method thereof. After the scrap steel is made and refined, die casting or continuous casting is carried out, and hot rolling is carried out. First austenitize the hot-rolled steel slab at 850-1000°C for 0.5-5.0 hours, and then perform bainitic multi-step isothermal transformation to obtain ultra-high strength and high toughness multi-step isothermal bainitic steel.

[0039] The multi-step isothermal transformation of the bainite is transformed into a three-step isothermal transformation: the first step is kept at 350-450°C in a salt bath for 0.2-1.0 hours, and the second step is kept at 250-350°C in a salt bath for 2-30 hours , the third step is to keep warm in an inert atmosphere at 220~250°C for 24~120 hours, and then cool to room temperature.

[0040] The ultra-high strength and high toughness multi-step isothermal bainite steel prepared in this example: the tensile strength...

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Abstract

The invention relates to an ultrahigh-strength high-toughness multistep isothermal bainite steel and a preparation method thereof. The technical scheme of the invention is as follows: a hot-rolled steel billet is austenitized 0.2-5.0 hours at a temperature of 850-1100 DEG C firstly, and then the steel billet is subjected to bainite multistep isothermal transformation, so that an ultrahigh-strength high-toughness multistep isothermal bainite steel is obtained. The multistep isothermal transformation is implemented through the following steps: 1, carrying out heat preservation 0.2-3.0 hours in an isothermal medium at a temperature of 250-450 DEG C; 2, carrying out heat preservation 2-50 hours in the isothermal medium at a temperature of 220-350 DEG C; 3, carrying out heat preservation 24-240 hours in the isothermal medium at a temperature of 180-250 DEG C; and 4, carrying out heat preservation 50-360 hours in the isothermal medium at a temperature of 150-220 DEG C, and cooling the obtained product to room temperature, wherein the multistep refers to step 1 to step 2, or step 1 to step 3, or step 1 to step 4. The bainite steel prepared by using the method disclosed by the invention has the characteristics of high hardness, high strength, high toughness, good volume stability and fine microstructure.

Description

technical field [0001] The invention belongs to the technical field of ultra-high strength steel. In particular, it relates to an ultra-high-strength, high-toughness multi-step isothermal bainite steel and a preparation method thereof. Background technique [0002] It is generally believed that the tensile strength exceeds 1500N / mm 2 The alloy structural steel is ultra-high strength steel. At present, the level of ultra-high-strength steel can be achieved through reasonable alloying and heat treatment process design, which can better meet the requirements of high efficiency and high safety. Ultra-high-strength steel is mainly used in construction machinery, high-rise buildings, rails, and armored vehicles , and other structural components subject to greater stress. Scholars at home and abroad have done a lot of beneficial exploration and development of ultra-high strength steel, in which martensite and bainite are the main matrix structures. [0003] Low-alloy ultra-high...

Claims

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Application Information

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IPC IPC(8): C21D1/20C21D6/00C22C38/58C22C38/50
Inventor 吴开明汪兴隆陈思思顾立媛
Owner WUHAN UNIV OF SCI & TECH
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