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Medium-manganese TRIP (Transformation-Induced Plasticity) steel and preparation method thereof

A technology of quenched steel and cold-rolled steel plate, applied in the field of medium manganese TRIP steel and its preparation, can solve the problems of lower elongation, lower elongation, less retained austenite, etc., and achieve industrial production, lower mechanical properties, The effect of stable performance

Inactive Publication Date: 2016-12-07
INNER MONGOLIA UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, due to the very short holding time in the critical zone, generally no more than 10 minutes or even shorter, the martensite-to-austenite phase transformation process of medium manganese steel during austenitization in the critical zone is mainly controlled by manganese diffusion. Due to the relatively slow diffusion of manganese, it takes a long time to reach an equilibrium state, therefore, a short annealing time in the critical zone will affect the volume fraction of reversed austenite in the critical zone, resulting in less retained austenite in the final structure, thereby reducing elongation
[0006] Theoretically, increasing the critical annealing temperature can increase the martensite martensite→austenite transformation process speed, but there will be the following problems: First, from the perspective of thermodynamic equilibrium, although increasing the critical annealing temperature can increase the reverse austenite However, the content of carbon and manganese in the reversed austenite decreases, so that martensitic transformation occurs in the subsequent cooling process, resulting in the reduction of retained austenite in the structure and the decrease of elongation; in addition, the phase From the perspective of variable kinetics, although increasing the critical annealing temperature can obtain the required amount of reversed austenite at a shorter critical annealing time, due to the influence of manganese diffusion rate, the composition of reversed austenite is not uniform, and some austenite The content of manganese in the tenite is low, and it is easy to undergo martensitic transformation in the subsequent cooling process, resulting in the reduction of retained austenite in the final structure
Therefore, the performance deficiency of medium manganese TRIP steel caused by the short annealing time in the critical zone of the continuous annealing production line cannot be compensated by increasing the annealing temperature.

Method used

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  • Medium-manganese TRIP (Transformation-Induced Plasticity) steel and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0067] Its components are calculated by weight percentage: C: 0.21%; Mn: 4.8%; Si: 1.4%; the rest is Fe and other unavoidable impurities.

[0068] According to the above ingredients, smelt in a 50kg vacuum induction furnace, and forge into a billet (steel billet), heat the billet to 1200°C with the furnace, and keep it warm for 2 hours;

[0069] Then rolling on a hot rolling mill, the rough rolling start temperature is controlled at 1100°C, and the finish rolling finish temperature is controlled at 880°C;

[0070] Water cooling to the coiling temperature, the coiling temperature is controlled at 550°C, and kept for 2 hours;

[0071] The hot-rolled steel plate is pickled and cold-rolled into a chilled plate with a thickness of 1mm;

[0072] Heat the chilled plate to 675°C at a heating rate of 10°C / s, and keep it isothermally for 5 minutes;

[0073] Then quickly cool (>20°C / s) to 250°C and wait for 10 seconds;

[0074] Then heated to the partition temperature of 325 ° C, isot...

Embodiment 2

[0078] Each component is calculated by weight percentage: C: 0.18%; Mn: 5.3%; Si: 1.3%; the rest is Fe and other unavoidable impurities.

[0079] According to the above composition, it is smelted in a 50kg vacuum induction furnace and forged into a billet (steel billet);

[0080] The billet is heated to 1150°C with the furnace and kept for 3 hours.

[0081] Then rolling on a hot rolling mill, the rough rolling start temperature is controlled at 1050°C, and the finishing rolling finish temperature is controlled at 850°C;

[0082] Water cooling to the coiling temperature, the coiling temperature is controlled at 600°C, and kept for 1.5 hours;

[0083] The hot-rolled steel plate is pickled, cold-rolled into a chilled plate with a thickness of 2.0mm, and then heat-treated;

[0084] Heat the chilled plate to 700°C at a heating rate of 15°C / s, and keep it isothermally for 2 minutes;

[0085] Then quickly cool (>20°C / s) to 280°C and wait for 10 seconds;

[0086] Then heated to th...

Embodiment 3

[0090] Each component is calculated by weight percentage: C: 0.15%; Mn: 4.5%; Si: 1.5%; the rest is Fe and other unavoidable impurities;

[0091] According to the above composition, it is smelted in a 50kg vacuum induction furnace and forged into a billet (steel billet);

[0092] The billet is heated to 1250°C with the furnace and kept for 3 hours.

[0093] Then rolling on a hot rolling mill, the rough rolling start temperature is controlled at 1050°C, and the finishing rolling finish temperature is controlled at 900°C;

[0094] Cool in water to the coiling temperature, the coiling temperature is controlled at 500, and keep warm for 2 hours;

[0095] The hot-rolled steel plate is pickled, cold-rolled into a chilled plate with a thickness of 0.6-2.0mm, and then heat-treated;

[0096] Heat the chilled plate to 650°C at a heating rate of 15°C / s, and keep it isothermally for 5 minutes;

[0097] Then quickly cool (>20°C / s) to 240°C and wait for 10 seconds;

[0098] Then heated ...

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Abstract

The invention provides medium-manganese TRIP (Transformation-Induced Plasticity) steel and a preparation method thereof. According to the medium-manganese TRIP steel and the preparation method thereof, medium-manganese cold rolled steel is taken as a raw material; the cost is low; the performance of a final product is realized by adopting critical region heat preserving, quenching cooling and partitioning processes; the structure of the medium-manganese steel is controlled by utilizing an over-aging stage in a continuous annealing production line, and the residual austenite volume fraction of the structure is improved in a relatively short critical annealing time, so that mechanical properties of a product are ensured, and meanwhile, the cost is reduced as much as possible; the performance of the steel is stable, the process fluctuation has little influence on performance, and industrial production is facilitated; and the prepared medium-manganese TRIP steel is high in strength, high in elongation and good in forming property, can be widely applied to reinforcing structural parts, such as a B-pillar reinforcing plate, to improve the collision safety of an overall vehicle, and achieves the effects of reducing weight and reducing emission.

Description

technical field [0001] The invention relates to the technical field of metal materials, in particular to a medium manganese TRIP steel and a preparation method thereof. Background technique [0002] High-strength and high-plasticity are the performance goals pursued by automobile thin plates, especially the light weight of automobiles and the improvement of safety requirements, requiring steels for automotive structural parts to have high-strength plasticity. The strength-plastic product of the first generation of automotive steel is at the level of 10-20GPa·%, which can no longer meet the dual requirements of lightweight and high safety for the future development of the automotive industry; the tensile strength of the second-generation automotive steel can reach 800- 1000MPa, the strength-plastic product has reached 60GPa·%, but the second-generation automotive steel has added a large amount of alloying elements, making the cost higher. In the past few decades, after the f...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D1/18C22C38/04C22C38/02
CPCC21D1/18C21D6/005C21D2211/001C21D2211/005C21D2211/008C22C38/02C22C38/04
Inventor 李岩定巍龚志华
Owner INNER MONGOLIA UNIV OF SCI & TECH
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