Hot Flat Product Rolling, Rolls, Safety & Health
To ensure sound internal quality and performance of a steel plate, some grades require not only through-thickness tensile testing (Z-test) but also mid-thickness Charpy V-notch testing. To meet these requirements, the rolling schedule needs to be optimized to not only ensure the final dimensions of the product but also break up the as-cast structure. Most importantly, deformation from rolling needs to penetrate the plate centerline to refine the microstructure at that location. In the present study, two pass schedules were examined to assess the effect of pass reduction on deformation penetration to the plate centerline.
Nucor Steel–Hertford County contracted Tenova to upgrade the burner management system on its walking beam reheat furnace. The objective of the project was to attain compliance with the current NFPA-86 (2015) requirements, remotely ignite the furnace and heat it to operating temperature. The scope included installation of a new burner management panel, modifications to the main gas train and zone piping, replacement of the existing pilot burner system with spark ignition and flame detection, an upgraded combustion control programmable logic controller, and all associated software.
Some cracks were found along the route of a spline gear at an output shaft of a main rougher reducer in a hot strip mill of JFE Steel, Fukuyama. As a result of torque measurement, the maximum torque was 260% of motor rated, and a full-model finite element method (FEM) analysis confirmed the calculated fatigue life is close to an actual life. Therefore the spline was cut off from the shaft and a new coupling hub was installed with thermal insert and key design. In addition, 3D FEM analysis at the key components was performed and optimized the dimensions.
For many years, the majority of backup rolls have been monobloc rolls, either cast or forged, with chromium contents of 1–5%. Gontermann-Peipers (GP) is the only producer worldwide of cast compound backup rolls with a hard working layer and a ductile core. The GP process allows higher alloying of the outer shell since core/neck properties and forgeability are not affected. This paper introduces two innovations in the field of backup rolls: a cast high-alloyed 8% chromium compound roll with superior wear resistance and a forged 5% chromium compound roll with superior fatigue properties.
High-strength steel (HSS) plates with yield stresses of 800 to 1,600 MPa can be produced due to advances in material science and heat treatment technology. HSS plates are applied for abrasion-resistant parts for mining and construction machines and transportation vehicles with lightweight or higher capacity, however they can have large deviations of flatness and high residual stress from the quenching process. HSS plate leveling is much more difficult than middle-level plate as with as-rolled plates. Leveling such hard material requires high leveling force capacity and high torque with small bending radius (small roll diameter, etc.).
Micro/nanostructure introduced by femtosecond laser surface process (FLSP) is a key factor contributing to its special wetting property. Imprinting is one of most commonly used technologies for manufacturing this structure. This study combined two technologies, providing a new method to produce superhydrophobic surface for mass production. The experimental results have proved that the counter-metal surface (aluminum 6061) of FLSP structure varies from hydrophilic to hydrophobic by changing the pressure, temperature and deposition conditions. During the imprinting process, little FLSP die surface (tungsten carbide) degradation was observed. Superhydrophobic iron alloy surface is also expected by applying the method mentioned above.
Argon gas stirring is applied at ladle treatment stations by the lance from the top surface at ArcelorMittal Burns Harbor. Homogenization and inclusion control are important issues for large-sized ladles (275 metric tons) with limited processing time. The optimal mixing condition was investigated with copper tracer trials. The immersion depth and flowrates were varied. Literature review of top stir lances shows generally 80–90% immersion at the off-center position to be the best condition. However, shallower immersion (65–70%) had a shorter mixing time in this study. Top stir literature data were collected and used to compare existing correlations. Stirring power with length scale correction was best fitted to many experimental data. The optimal radial and immersion positions were found based on the circulation efficiency defined as the kinetic energy to input stirring power ratio.