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

2005 ◽  
pp. 221-228
Author(s):  
Fulvio Siciliano ◽  
L.L. Leduc
Keyword(s):  
Flow Stress ◽  
Microstructural Evolution ◽  
Microalloyed Steels ◽  
Thin Slab ◽  
Mean Flow ◽  
Thin Slab Casting ◽  
Slab Casting ◽  
Mean Flow Stress ◽  
Direct Rolling

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 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.

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.

Application of Deformation to Improve Hot Ductility in the Peritectic Steel

2005 ◽  
Vol 500-501 ◽  
pp. 203-210 ◽  
Author(s):  
Ahmad Rezaeian ◽  
Faramarz Zarandi ◽  
D.Q. Bai ◽  
Steve Yue
Keyword(s):  
Flow Stress ◽  
High Strength ◽  
Microalloyed Steels ◽  
Hot Strip Mill ◽  
Mean Flow ◽  
Hot Strip Rolling ◽  
Strip Rolling ◽  
Slip Ratio ◽  
Hot Strip ◽  
Mean Flow Stress

The hot strip rolling of advanced microalloyed high strength steels still represents a new task to many mills due to the lack of data on the hot deformation resistance. With the aid of processing data from the Ispat-Inland hot strip mill, the “measured mean flow stresses” are calculated from the mill force using the Sims analysis and taking into account roll flattening, slip ratio and the redundant strain. A modification of the Misaka mean flow stress equation is proposed for C – Mn – Si – Al steels microalloyed with up to 0.02 % Nb. The effects of alloying and microalloying are then estimated. A new fitting parameter shows excellent agreement with the mean flow stress data from industrial processing of advanced high strength microalloyed steels. However, during the second half of the rolling schedule (lower temperature region), indications of austeniteto- ferrite transformation were found.

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