Evolution of Microstructure and Properties of Steel 22MnB5 due to Short Austenitization with Subsequent Quenching

Grydin, Olexandr; Schaper, Mirko

doi:10.1002/srin.201600086

Cited by 23 publications

(8 citation statements)

References 21 publications

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“…A microstructure consisting of ferrite, bainite, martensite and not completely dissolved carbides is formed during steel cooling. [18,26] Furthermore, alloying elements such as manganese or chromium reduce the critical cooling rate. In microscopically small areas where high amounts of these alloying elements are present, for example around dissolved carbides, martensite is formed.…”

Section: B Micrograph and Hardness Investigationsmentioning

confidence: 99%

Characterization of Phase Transformations During Graded Thermo-Mechanical Processing of Press-Hardening Sheet Steel 22MnB5

Reitz

Grydin

Schaper

2020

Metall Mater Trans A

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Safety-relevant components in automobiles require materials that combine high strength with sufficient residual ductility and high-energy absorption. A graded thermo-mechanical treatment of the press-hardening steel 22MnB5 with graded microstructure can provide a material with such properties. Different austenitization temperatures, cooling and forming conditions within a sheet part lead to the development of microstructures with mixed phase compositions. To determine the resulting phase contents in such graded processed parts, a large number of dilatometric tests are usually required. With a non-contact characterization method, it is possible to detect local phase transformations on an inhomogeneously treated flat steel specimen. For press-hardening steel after heat treatment and thermo-mechanical processing, correlations between austenitization temperature, hot deformation strain, microstructure, and hardness are established.

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Section: B Micrograph and Hardness Investigationsmentioning

confidence: 99%

Characterization of Phase Transformations During Graded Thermo-Mechanical Processing of Press-Hardening Sheet Steel 22MnB5

Reitz

Grydin

Schaper

2020

Metall Mater Trans A

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“…One disadvantage of this method is high energy expenses ( Ref 16). Furthermore, it is possible to use alternative heating processes that ensure high heating rates and low oxidation, such as inductive ( Ref 17,18), conductive (Ref 18,19) and contact (Ref 20,21) heating. However, these might be disadvantageous due to extensive equipment, non-uniformity of heating or the necessity to use uncoated sheets.…”

Section: Introductionmentioning

confidence: 99%

Tailoring Soft Local Zones in Quenched Blanks of the Steel 22MnB5 by Partial Pre-cooling with Compressed Air

Golovko

Stolte

Wölki

et al. 2020

J. of Materi Eng and Perform

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The high-strength boron steel 22MnB5 steel is widely used for automotive lightweight constructions. A novel approach is promising to tailor strength and ductility in the hardened condition using locally pretempered sheets for the hot stamping process. It results in the formation of locally soft spots where mechanical joining is subsequently intended. A slow pre-cooling of the later joining zones with cooling rates below a certain critical cooling rate for obtaining a decreased strength in these regions is required. A tubular air cooling system suited for this task is presented and tested in a process where the subsequent quenching of the overall sheet is realized by rapid cooling in a water bath. Varying the air pressure and cooling duration allows controlling the size of the softened local spot in a wide range and still obtaining a bainitic microstructure. Using two-stage cooling with point jet nozzles and a subsequent hot stamping process with water-cooled dies resulted in a main sheet hardness of about 470 HV5 and of 260 HV5 in the pre-cooled spots, respectively.

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“…It was reported by Karthikeyan et al [ 3 ] that the grain size of 9Cr-1Mo steel was refined from 26 to 12 μm via high temperature holdings. The grain size of 22MnB5 carbon steel was significantly refined by short austenization at 900 °C for 2 s, and the tensile properties and hardness were greatly enhanced [ 4 ], whereas, high temperature holdings for a long period of time could lead to grain coarsening of steels. Fernández et al [ 5 ] carried out research on grain size evolution of 16MnNi4 steel in isothermal holdings via metallography, and it showed that the dramatic growth of grains was followed by a slow growth during holding at 1050–300 °C.…”

Section: Introductionmentioning

confidence: 99%

In Situ Investigation of Grain Evolution of 300M Steel in Isothermal Holding Process

Chen

Zheng

et al. 2018

Materials

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The relationships between initial microstructures, process parameters, and grain evolutions in isothermal holdings have drawn wide attention in recent years, but the grain growth behaviors of 300M steel were not well understood, resulting in a failure in precise microstructure controlling in heat treatment. In this work, in situ observations were carried out to characterize the grain evolutions of 300M steel with varying holding time, holding temperatures, and initial microstructures. The intriguing finding was that the grain refinement by austenization of 300M steel was followed by a dramatic grain growth in the initial stage of holding (≤~600 s), and with increasing time (~600–7200 s), the average grain size appeared to have a limit value at specific temperatures. The austenization process accelerated the grain growth by generating large quantity of grain boundaries at the initial stage of holdings, and the growth rate gradually slowed down after holding for ~600 s because the driven force was weakened due to the reduction of grain boundary energy. The initial structure and the initial grain size of 300M steel had no obvious influences on the grain size evolutions. The mechanisms of grain growth were analyzed based on in situ observations and transmission electron microscope (TEM) characterizations. A grain evolution model considering the grain boundary migration of 300M steel was established for the isothermal holding process. Good agreement was obtained between the in situ observation results and the model calculation results. This investigation aimed to understand fundamentally the grain evolutions of 300M steel in the isothermal holding process.

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Evolution of Microstructure and Properties of Steel 22MnB5 due to Short Austenitization with Subsequent Quenching

Cited by 23 publications

References 21 publications

Characterization of Phase Transformations During Graded Thermo-Mechanical Processing of Press-Hardening Sheet Steel 22MnB5

Characterization of Phase Transformations During Graded Thermo-Mechanical Processing of Press-Hardening Sheet Steel 22MnB5

Tailoring Soft Local Zones in Quenched Blanks of the Steel 22MnB5 by Partial Pre-cooling with Compressed Air

In Situ Investigation of Grain Evolution of 300M Steel in Isothermal Holding Process

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