scholarly journals Vanadium Microalloyed Steel for Thin Slab Casting and Direct Rolling

2005 ◽  
Vol 500-501 ◽  
pp. 237-244 ◽  
Author(s):  
Yu Li ◽  
T.N. Baker
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Grain Structure ◽  
High Yield ◽  
Microalloyed Steels ◽  
Dispersion Strengthening ◽  
Thin Slab ◽  
Thin Slab Casting ◽  
Slab Casting ◽  
Direct Rolling

Vanadium microalloyed steels with high yield strength (»600MPa), good toughness and ductility have been successfully produced in commercial thin slab casting plants employing direct rolling after casting. Because of the high solubility of VN and VC, most of the vanadium is likely to remain in solution during casting, equalisation and rolling. While some vanadium is precipitated in austenite as cuboids and pins the grain boundaries, a major fraction is available for dispersion strengthening of ferrite. Despite a coarse as-cast grain size, significant grain refinement can be achieved by repeated recrystallisation during hot rolling. Consequently, a fine and uniform ferrite grain structure is produced in the final strip. Increasing the V and N levels increases dispersion strengthening which occurs together with a finer ferrite grain size. The addition of titanium to a vanadium containing steel, decreases the yield strength due to the formation of V-Ti(N) particles in austenite during both casting and equalisation. These large particles reduced the amount of V and N available for subsequent precipitation of fine (~5nm) V rich dispersion strengthening particles in ferrite.

Modeling of the Microstructural Evolution and Mean Flow Stress during Thin Slab Casting/Direct Rolling of Niobium Microalloyed Steels

2005 ◽  
Vol 500-501 ◽  
pp. 221-228 ◽  
Author(s):  
Fulvio Siciliano ◽  
L.L. Leduc
Keyword(s):  
Flow Stress ◽  
Microalloyed Steels ◽  
Hot Strip Mill ◽  
Thin Slab ◽  
Mean Flow ◽  
Thin Slab Casting ◽  
Slab Casting ◽  
Mean Flow Stress ◽  
Direct Rolling ◽  
The Mean

Mill logs obtained from the Hylsa CSPTM (thin slab casting/direct rolling – TSC/DR) mill were examined so that the mean flow stresses at each pass were calculated using the Sims equation modified to take into account the forward slip ratio, the redundant strain and the work roll flattening. The mean flow stresses were then compared to predicted values obtained from a model. The microstructures during the CSP process were predicted by a mathematical model which was initially derived for conventional slab/roughing mill/hot strip mill (HSM) processing route. The adapted model takes into account the deformation of the as-cast structure in the finishing CSP mill, by using particular microstructural equations to calculate the softening kinetics and grain sizes. The main metallurgical features such as the occurrence of Nb(C,N) precipitation, the softening mechanism which takes place (static or metadynamic recrystallization) as well as the strain accumulation between passes were calculated. The mean-flow-stress results obtained from the calculations are in good agreement with the mill data. The present analysis indicates that it is possible to produce fine-grained microalloyed steels with homogeneous microstructure in thin slab casting/direct rolling processing.

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

Metals ◽  
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.

Potential of Hot Rolled Dualphase Steel from Compact Strip Production CSP® in Automotive Applications

2012 ◽  
Vol 706-709 ◽  
pp. 2278-2283
Author(s):  
Carl Peter Reip ◽  
Christian Klinkenberg ◽  
Long Chang Tong ◽  
Pavel Hora
Keyword(s):  
Mechanical Properties ◽  
Forming Limit ◽  
Thin Slab ◽  
Forming Simulation ◽  
Thin Slab Casting ◽  
Hot Strip ◽  
Slab Casting ◽  
Direct Rolling ◽  
Hot Rolled ◽  
Strip Production

Industrial thin slab casting and direct rolling processing started in 1989 with the world’s first CSP® plant at Crawfordsville (USA). Since this time CSP® and competing thin slab casting and direct rolling concepts have been developed to a standard process for hot strip production [1]. Typical features of the CSP® process are the homogeneous structural and mechanical properties all along the strip. Direct hot rolling of thin slabs may be followed by a well defined cooling pattern to produce hot strip from high strength multiphase steel, like dualphase (DP) grades, on the runout table. These steel grades are characterized by a favorable combination of strength and ductility based on hard martensitic particles embedded in a ductile ferritic matrix. This paper highlights the mechanical properties of hot rolled DP steel from CSP® production. To this purpose, multiple tests and modeling have been applied to determine e.g. r-values, forming limit curves and yield locus. In addition, forming simulation as well as laboratory and industrial deep drawing tests have been performed.

New Trends and Technologies in Thin-Slab Direct Rolling: Improved Microstructure & Mechanical Behavior

2012 ◽  
Vol 706-709 ◽  
pp. 2752-2757 ◽  
Author(s):  
Christian Klinkenberg ◽  
C. Bilgen ◽  
J.M. Rodriguez-Ibabe ◽  
Beatriz López ◽  
P. Uranga
Keyword(s):  
Rolling Process ◽  
Recrystallization Temperature ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Thin Slab ◽  
Present Contribution ◽  
Thin Slab Casting ◽  
Finishing Mill ◽  
Direct Rolling ◽  
Cast Microstructure

The use of CSP®thin slab casting followed by direct thermomechanical rolling is well placed for the production of low-carbon Nb microalloyed steels. In this process thin slabs of between 48 and 90 mm thickness are cast and directly hot rolled to hot strip typically between 1 and 12 mm thick. To obtain optimum strength and toughness property combinations in a direct rolling process, hot rolling has to compact the dendritic as-cast microstructure and to achieve a fine-grained microstructure. This affords a two-stage rolling strategy with start rolling above the recrystallization stop temperature and finish rolling in the non-recrystallization temperature range. Temperature and deformation in the first stand should be as high as possible in order to delete the initial as-cast microstructure by complete recrystallization. Based on these considerations, SMS Siemag further developed the CSP®concept including features allowing isothermal rolling in the first stands of the finishing mill. The present contribution gives the results of a laboratory study of this innovative approach. The report concludes with resulting new plant configurations for improved high strength and API linepipe grade production.

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