Processing of Niobium Microalloyed API Grade Steel on a Thin Slab Plant

2005 ◽  
Vol 500-501 ◽  
pp. 253-260 ◽  
Author(s):  
Christian Klinkenberg ◽  
K.-E. Hensger
Keyword(s):  
Work Hardening ◽  
Polymorphic Transformation ◽  
Thermomechanical Processing ◽  
High Strength ◽  
Low Carbon ◽  
Thin Slab ◽  
Thin Slab Casting ◽  
Slab Casting ◽  
Direct Rolling ◽  
Grade Steel

The use of thin slab casting and direct rolling is well suited for the production of niobium microalloyed low-carbon high strength linepipe grades. The slabs have excellent surface quality. Thermomechanical processing by controlling hot work hardening and softening processes of austenite and its polymorphic transformation into ferrite results in a powerful microstructure refinement. This is a sound basis for setting high strength, combined with excellent ductility and toughness.

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.

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.

scholarly journals Control of Upstream Austenite Grain Coarsening during the Thin-Slab Cast Direct-Rolling (TSCDR) Process

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 158 ◽  
Author(s):  
Tihe Zhou ◽  
Ronald O’Malley ◽  
Hatem Zurob ◽  
Mani Subramanian ◽  
Sang-Hyun Cho ◽  
...  
Keyword(s):  
Thermomechanical Processing ◽  
Liquid Core ◽  
High Strength ◽  
Thin Slab ◽  
Delta Ferrite ◽  
Two Phase ◽  
Austenite Grain Size ◽  
Grain Coarsening ◽  
Austenite Grain ◽  
Direct Rolling

Thin-slab cast direct-rolling (TSCDR) has become a major process for flat-rolled production. However, the elimination of slab reheating and limited number of thermomechanical deformation passes leave fewer opportunities for austenite grain refinement, resulting in some large grains persisting in the final microstructure. In order to achieve excellent ductile to brittle transition temperature (DBTT) and drop weight tear test (DWTT) properties in thicker gauge high-strength low-alloy products, it is necessary to control austenite grain coarsening prior to the onset of thermomechanical processing. This contribution proposes a suite of methods to refine the austenite grain from both theoretical and practical perspectives, including: increasing cooling rate during casting, liquid core reduction, increasing austenite nucleation sites during the delta-ferrite to austenite phase transformation, controlling holding furnace temperature and time to avoid austenite coarsening, and producing a new alloy with two-phase pinning to arrest grain coarsening. These methodologies can not only refine austenite grain size in the slab center, but also improve the slab homogeneity.

Sign in / Sign up

Export Citation Format

Share Document