Papers by Keyword: Direct Rolling

Abstract: This paper focuses on the mechanical property differentiation and phase content differentiation of HRB400 rebars under the direct rolling of without-heating (DROW) process. The results showed that the temperature distribution from the head region to the tail region of the billet before rolling under the DROW process was different compared to the traditional hot rolling (THR) process, which resulting in the difference of each phase volume fractions and the grain size of the rebar. Compared with the THR process, the phase distribution of the rebars under the DROW process is not uniform, showing the characteristics of low ferrite content in the head region, followed by the tail region, and the highest in the middle region. It was demonstrated that the DROW process could improve the mechanical properties of the rebar, but the difference in phase content and grain size distribution leads to a large variability in the enhancement of the mechanical properties of rebar rolled in different areas of the billet.

Abstract: 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.

Abstract: The macro structures, microstructures, textures and precipitates in non-oriented electrical steels were studied by means of optical microscopy, scanning electron microscopy (SEM), electron back scattering dispersion (EBSD) and transmission electron microscopy (TEM) in the specimens produced by conventional continuous casting process and thin slab continuous casting and direct rolling process. Results showed the macro structures in as-cast slabs and the microstructures in as-rolled strips were more fine-grained and uniform with regard to compact strip production (CSP) process, compared with that in conventional process. No obvious texture was observed in hot rolled strips produced by CSP process.

Abstract: The effect of hot rolling parameters including different hot rolling reduction, soaking time of ingots and chemical composition on cold rolling texture by TSCR process was studied. The result indicates that α fibers and γ fiber texture were affected by hot rolling reduction, and oriented density αfibers texture increases with hot rolling reduction rate increasing, and the texture components is same in the surface and different in the center. The strength of γ fiber texture, from {111}<110>to {111}<112>, is decreasing trendency for ingot soaked for 10min and 20min. however, changing trendency from {111}<110>to {111}<112> in 1/8 thickness and 1/4 thickness of cold rolling strip for ingot soaked for 30min. The volume fraction of {111}<112> is rising with the ingot soaked time and the maxium is 3.5 percent, and the volume fraction of {111}<112> is higher in every layer of cold rolling strip whose chemical composition includes Sn than without Sn, the volume fraction of {111}<112> is higher in 1/8 and 1/4 layers than the surface and center layers.

Abstract: 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. 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 fine-grained HSLA steel or multiphase hot strip on the runout table. The product range covers low carbon as well as medium and high carbon steel grades comprising IF-, HSLA-, API-, electrical- and multiphase steel grades. CSP® processed thin hot strip is used for non-exposed parts and may substitute cold rolled strip. Hot strip from thin slab can be easily further processed to cold rolled and/or surface treated strip. Today process and material developments e.g. go for energy saving, rise in productivity, advanced surface requirements, HSLA and multiphase steel grades combining higher strength and ductility as well as multiphase steel grades for hot dip galvanizing.

Abstract: 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.

Abstract: 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.