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High temperature confocal microscopy (using cooling rates of 1 and 20 °C s−1) has been used in conjunction with segregation modeling (for cooling rates of 0.1–100 °C s−1) to understand the implications that high cooling rates, representative of that seen for belt casting, has on compositional inhomogeneity and precipitation in high strength low alloy steels. Due to the increased level of segregation (and reduced back diffusion) precipitates are predicted, and shown, to form in the interdendritic solute rich regions at temperatures higher than would be expected under equilibrium conditions at the higher cooling rate. This results in a larger volume fraction of precipitates in samples held at 1000 °C after being cooled at 20 °C s−1 compared to those cooled at 1 °C s−1. [ABSTRACT FROM AUTHOR]

In the present work, low-medium heat inputs of 15, 30, and 50 kJ cm−1 are adopted to simulate Coarse-Grain Heat-Affected Zones (CGHAZ) of a designed HSLA steel by Gleeble-3500 thermal simulator. Microstructures are characterized by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). Charpy impact tests are performed to evaluate toughness of CGHAZs. Results show that impact toughness (−50 °C) of CGHAZs with heat inputs of 15, 30, and 50 kJ cm−1 is 156.18, 172.86, and 181.49 J, respectively. Toughness stays in high level though heat input varies within low-medium range. Evolution of microstructures is investigated and micro-mechanisms of high toughness in all of the three heat inputs are discussed in detail. An original alloy design for HSLA steels with high toughness CGHAZ is proposed as well. [ABSTRACT FROM AUTHOR]

The basic concept of thermomechanical treatment (TMT) or thermomechanical controlled processing (TMCP) is responsible for the development of many advanced steel grades with improved mechanical properties during the last 50 years. A retro-perspective view, an explanation of the most important influencing factors and a presentation of the enormous benefits for the costumer are given in this review. A sound knowledge on the synergism of recrystallization, precipitation, and transformation phenomena forms the basis to produce fine, homogeneous microstructures with improved properties. Starting from structural steels, improvements can be achieved with respect to higher strength and toughness values combined with better weldability and formability, mainly based on reduction of carbon content and finer grain sizes. The benefits in the application areas are described in detail. TMCP is not only used for flat products, but also for long products and forgings of different steel grades. Physical simulation and modeling contribute significantly to these developments, which also form the basis for computer-aided control or real-time online-models. In the next years, a complete shift to cyber physical systems (CPS) is predicted, which needs an aligned education effort. [ABSTRACT FROM AUTHOR]

Industrial thin slab casting and direct rolling processing started more than 25 years ago with the world's first compact strip production (CSP®). Since that 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 this process are the homogeneous structural and mechanical properties all along the strip. The product range covers low carbon, as well as medium and high carbon steel grades comprising IF, HSLA, API, electrical, and AHSS multiphase steel grades. Hot strip from thin slab can be easily further processed to cold rolled and/or surface treated strip. A special feature is thin hot strip that may substitute cold rolled strip. Today, process and material developments, for example, go for rise in productivity, thinner gauge hot strip, as well as thicker line pipe and 3rd generation AHSS grades combining higher strength and ductility. The quality- and product-related advantages of thin slab casting and direct rolling technology are explained in this contribution at the example of the CSP® process. [ABSTRACT FROM AUTHOR]