Effects of Cooling Rate and Direct Hot Deformation Conditions after Solidification on the Austenitic Microstructure Evolved by Simulated Strip Casting and Thin Slab Casting Processes in HSLA Steels

Currently new continuous casting processes such as thin slab caster or strip casting are industrialized or under developing in the world steel makers. In these casting processes, cooling rate after solidification becomes much faster compared with thick slab caster, and hot rolling mill connected directly with casting machine tends to be installed. The present study was conducted to investigate variations of austenitic grain size and micro segregation with cooling rate after solidification and also direct hot deformation conditions in austenite immediately after solidification in HSLA steels. HSLA steels were 0.15%C-0.25%Si-1.50%Mn, 0.028%Nb and 0.028%Nb-0.015%Ti with the same basic compositions. A hot working simulator of THERMECMASTER-Z was used, and the center part of tensile specimen set up in this machine was partially or fully levitation-melted by induction heating under argon gas atmosphere. After melting, specimens were cooled at cooling rate from 0.4K/s to 40K/s, and this range covered cooling rates after solidification in heavy thick slab caster and strip casting. Direct hot tensile straining in austenite after solidification was conducted at strain rates from 1.4×10-3s-1 to 2.6s-1, corresponding to an extracting speed in a respective caster. The increase of cooling rate refined continuously as cast austenitic grain size, and it was enhanced in micro alloyed steels. Micro segregation such as Mn was improved by faster cooling. Direct straining after solidification markedly refined austenitic grain size through dynamic or static recrystallization occurring depending on strain rate.

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Effect of Coiling Temperature on Formability and Mechanical Properties of Mild Low Carbon and HSLA Steels Processed by Thin Slab Casting and Direct Rolling

ISIJ International ◽

10.2355/isijinternational.47.1204 ◽

2007 ◽

Vol 47 (8) ◽

pp. 1204-1213 ◽

Cited By ~ 16

Author(s):

Riccardo Riva ◽

Carlo Mapelli ◽

Roberto Venturini

Keyword(s):

Mechanical Properties ◽

Low Carbon ◽

Thin Slab ◽

Coiling Temperature ◽

Thin Slab Casting ◽

Hsla Steels ◽

Slab Casting ◽

Direct Rolling

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Model for the industrial prediction of carbonitride precipitation in HSLA steels cast by a thin slab casting plant

Revue de Métallurgie ◽

10.1051/metal:2003165 ◽

2003 ◽

Vol 100 (11) ◽

pp. 1067-1076

Author(s):

S. Baragiola ◽

L. Bisaccia ◽

C. Mapelli ◽

R. Venturini

Keyword(s):

Thin Slab ◽

Casting Plant ◽

Thin Slab Casting ◽

Hsla Steels ◽

Carbonitride Precipitation ◽

Slab Casting

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Primary Recrystallization Behaviors of Hi-B Steel with Lower Initial Nitrogen Produced by the Thin Slab Casting and Rolling Process

Metals ◽

10.3390/met11020189 ◽

2021 ◽

Vol 11 (2) ◽

pp. 189

Author(s):

Bing Fu ◽

Li Xiang ◽

Jia-Long Qiao ◽

Hai-Jun Wang ◽

Jing Liu ◽

...

Keyword(s):

Grain Size ◽

Electron Microscope ◽

Nitrogen Content ◽

Rolling Process ◽

Primary Recrystallization ◽

Thin Slab ◽

Nitriding Temperature ◽

Thin Slab Casting ◽

Slab Casting ◽

Inhomogeneity Factor

Based on low-temperature high-permeability grain-oriented silicon steel designed with an initial nitrogen content of 0.0055% and produced by the thin slab casting and rolling process, the effect of total nitrogen content and nitriding temperature on primary recrystallization microstructure and texture were studied by optical microscope, scanning electron microscope, transmission electron microscope, and electron backscatter diffraction. The nitriding temperature affects the primary recrystallization behaviors significantly, while the total nitrogen content has a small effect. As the nitriding temperature is 750–850 °C, the average primary grain size and its inhomogeneity factor are about 26.58–26.67 μm and 0.568–0.572, respectively. Moreover, the texture factor is mostly between 0.15 and 0.40. Because of the relatively sufficient inhibition ability of inherent inhibitors in a decarburized sheet, the nitriding temperature (750–850 °C) affects the primary recrystallization microstructure and texture slightly. However, as the nitriding temperature rises to 900–950 °C, the average primary grain size and its inhomogeneity factor increase to 27.75–28.26 μm and 0.575–0.578, respectively. Furthermore, because of the great increase on the area fraction of {112} <110> grains, part of texture factor is increased sharply. Therefore, in order to obtain better primary grain size and homogeneity, better texture composition, and stability of the decarburized sheet, the optimal nitriding temperature is 750–850 °C.

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