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Ultra-fine grain martensite ferrite dual-phase steel with two-peak ferrite grains distributed and production process of ultra-fine grain martensite ferrite dual-phase steel

A production process and ferrite technology, applied in the field of metallurgical materials, can solve the problems of low uniform elongation and achieve the effect of improving uniform elongation

Active Publication Date: 2017-09-19
NORTHEASTERN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Although the work hardening rate of ultrafine-grained dual-phase steel is improved due to the presence of hard phase martensite, its uniform elongation is still lower than that of coarse-grained dual-phase steel.

Method used

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  • Ultra-fine grain martensite ferrite dual-phase steel with two-peak ferrite grains distributed and production process of ultra-fine grain martensite ferrite dual-phase steel
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  • Ultra-fine grain martensite ferrite dual-phase steel with two-peak ferrite grains distributed and production process of ultra-fine grain martensite ferrite dual-phase steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0046] The selected ingot composition weight percent is: C 0.11%, Mn 1.83%, Si 0.062%, Al 0.38%, Mo0.17%, Cr 0.37%, Nb 0.04%, and the balance is Fe. The final rolling temperature is 800°C, and the strip thickness after rolling is 4.3mm. The hot-rolled slab was annealed at 1100°C for 10 hours, then cooled to room temperature in the furnace, then normalized at 900°C for 30 minutes, reheated to 570°C and kept for 10 minutes for warm rolling, and air-cooled to room temperature. The thickness of the obtained slab was 0.35 mm (ε=2.5 ); the warm-rolled slab is annealed on a continuous annealing test machine, the first heating (FHS) rate is 40 ° C / s, heated to Ac 1 Temperature (655°C), the second stage heating (SHS) rate is 2°C / s, and it is quenched immediately after heating to 750°C. The finally obtained ultra-fine-grained dual-phase steel sheet with bimodal ferrite distribution, the fine-grained ferrite grain size is 0.5-3 μm, and the coarse-grained ferrite grain size is 3-6.5 μm...

Embodiment 2

[0048] The selected ingot composition weight percent is: C 0.10%, Mn 1.7%, Si 0.05%, Al 0.35%, Mo0.16%, Cr 0.35%, Nb 0.037%, and the balance is Fe. The final rolling temperature is 820°C, and the strip thickness after rolling is 4mm. The hot-rolled slab was annealed at 1150°C for 12 hours, then furnace-cooled to room temperature, then normalized at 930°C for 30 minutes, reheated to 550°C and kept for 10 minutes for warm rolling, and air-cooled to room temperature. The thickness of the obtained slab was 0.4 mm (ε = 2.3); the warm-rolled slab is annealed on a continuous annealing test machine, the first heating (FHS) rate is 60 ° C / s, heated to Ac 1 temperature (663°C), the second stage heating (SHS) rate is 3°C / s, and it is quenched immediately after heating to 760°C. The final ultra-fine-grained dual-phase steel plate with bimodal ferrite distribution was obtained. The grain size of the fine-grained part of ferrite was 0.5-3 μm, and the grain size of the coarse-grained ferr...

Embodiment 3

[0050] The selected ingot composition weight percent is: C 0.08%, Mn 1.80%, Si 0.06%, Al 0.36%, Mo 0.16%, 0.38% Cr, 0.039% Nb, and the balance is Fe. The final rolling temperature is 850°C, and the strip thickness after rolling is 4.2mm. The hot-rolled slab was annealed at 1180°C for 15 hours, then furnace-cooled to room temperature, then normalized at 950°C for 20 minutes, reheated to 500°C and kept for 10 minutes for warm rolling, and air-cooled to room temperature. The thickness of the obtained slab was 0.45 mm (ε = 2.2); the warm-rolled slab is annealed on a continuous annealing test machine, the first heating (FHS) rate is 80 ° C / s, heated to Ac 1 Temperature (678°C), the second stage heating (SHS) rate is 4°C / s, and it is quenched immediately after heating to 770°C. The final ultra-fine-grained dual-phase steel sheet with bimodal ferrite distribution, the fine-grained ferrite grain size measured by scanning electron microscopy is 0.5-3 μm, and the coarse-grained ferri...

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Abstract

The invention discloses ultra-fine grain martensite ferrite dual-phase steel with two-peak ferrite grains distributed and a production process of the ultra-fine grain martensite ferrite dual-phase steel. After billet steel is obtained through smelting, casting, forging and hot rolling, the billet steel is subjected to heat treatment which comprises the following working procedures of homogenizing annealing, normalizing, warm rolling and continuous annealing, and continuous annealing comprises three stages that firstly, the billet steel is heated to the temperature of Ac1 at the speed of 40 DEG C / s-80 DEG C / s, secondly, the billet steel continues to be heated to 740 DEG C-800 DEG C at the speed of 1 DEG C / s-5 DEG C / s, and thirdly, quenching is carried out. By means of the process, austenite grains are refined, the ferrite gains are distributed in a two-peak size manner, the uniform elongation of the steel is greatly increased when the steel is pulled at the room temperature, and the yield ratio is smaller than 0.5.

Description

technical field [0001] The invention belongs to the technical field of metallurgical materials, in particular to an ultra-fine-grained martensitic ferrite dual-phase steel with bimodal ferrite grain distribution and a production process thereof. Background technique [0002] Martensitic ferritic dual-phase steel has become an important steel for automobiles due to its good strength and plasticity matching, high initial work hardening rate, and high impact energy absorption capacity, and has been widely used, but high-strength dual-phase Due to the increase of strength, the plasticity of steel decreases, which cannot meet the requirements of deep drawing performance, which limits its application in stamping parts. [0003] Refining the grains can improve the plasticity and toughness of the polycrystal while improving the strength. People have introduced the concept of ultra-fine grain into dual-phase steel. So far, scholars at home and abroad have used different methods to p...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/06C22C38/38C22C38/22C22C38/26C21D1/26C21D1/18C21D1/28C21D8/02
CPCC21D1/18C21D1/26C21D1/28C21D8/0231C21D8/0247C21D2211/005C21D2211/008C22C38/02C22C38/06C22C38/22C22C38/26C22C38/38
Inventor 邸洪双邓永刚闫宁黄慧强李云龙
Owner NORTHEASTERN UNIV
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