Combination of In Situ Confocal Microscopy and Calorimetry to Investigate Solidification of Super‐ and Hyper‐Duplex Stainless Steels

This paper investigates the application of cooling plate in a 4500m3 blast furnace in China. SEM‐EDS and an optical microscope were used to examine the affected area. The results demonstrate that using a cooling plate in a big blast furnace has a positive effect, notably in the belly and bosh areas, where the damage rate is less than 3%. While the cooling plates in the middle shaft are more severely damaged, with a damage rate of up to 55.40%. The majority of the copper cooling plate’s damage is centered in the water channel area, where there are furrows and numerous microcracks on the damaged surface, as well as a tiny quantity of metallurgical slag attached. Cracks form on both the inside and outside of the water channel, and the grains surrounding the cracks rise significantly, which is the primary cause of the cooling plate’s water leaking. The main factor of cooling plate damage in the early stage is wear, and the cracking caused by force in the later stage. The use of a copper cooling plate from the furnace bosh to the lower shaft is preferable to the use of a copper cooling stave.This article is protected by copyright. All rights reserved.

Damage Mechanism of Copper Cooling Plate on Large Blast Furnace

Gao

Zhang

et al. 2023

Effect of Boron on the Solidification Characteristics and Constitutive Equation of S31254 Superaustenitic Stainless Steel

Liu,

Wang,

Chen

et al. 2024

Solidification structure and segregation behavior of S31254 superaustenitic stainless steel ingot containing 0 wt% B and 0.005 wt% B are investigated. The results show that serious element segregation and massive eutectics are present in the center of the ingot. By contrast, the addition of boron reduces the secondary dendrite spacing, the degree of elemental segregation, and the σ phase. Further, the effect of boron on the solidification process is studied by using the high‐temperature confocal laser scanning microscope and combined with Thermo‐Calc thermodynamic simulation results. The results show that boron can widen the solidification temperature range and greatly retard the matrix solidification. The role of boron in refining dendrite structure and inhibiting precipitation is further confirmed. The effect of boron on the constitutive equation of S31254 superaustenitic stainless steel has also been researched through isothermal compression testing in the temperature range of 950–1200 °C and strain rate range of 0.01–10 s−1. The activation energy of the boron‐free and boron‐containing S31254 superaustenitic stainless steels based on the constitutive equation are 427.77 and 495.80 kJ mol−1, respectively. Processing maps indicate that the instability domain is significantly reduced and the hot ductility is improved after the addition of B.

Revealing the Dynamic Recrystallization Mechanism and Hot Workability of Fe–0.15C–10Mn Medium‐Mn Steel through Grain Size Distribution and 3D Processing Maps

Sun,

Liu,

Duan

et al. 2024

An in‐depth understanding of thermal deformation of medium‐Mn steels (MMnSs) is crucial for the forming fabrication of key automotive components. In this work, the Fe–0.15C–10Mn MMnSs are compressed under conditions of 900–1150 °C/0.001–10 s−1. Two‐stage models, dynamic recovery (DRV) and dynamic recrystallization (DRX), are constructed and proved to be accurately predictive with a correlation coefficient (R) of 0.997% and average absolute relative error (AARE) of 2.67%. Based on the analysis of microstructure evolution, the discontinuous DRX occured at a specific deformation condition of 900 °C–10 s−1, while the continuous DRX generated at other deformed conditions. The discontinuous DRX grains only distributed along pre‐existing grain boundaries, showing a necklace‐like grain structure with multiple small zigzag protrusions at the boundary. While continuous DRX grains with low dislocation density distributed both along and inside the pre‐existing grain boundaries. The developed 3D processing map identified high strain rate (0.1–10 s−1) as instability domains, in which heterogeneous microstructure are observed. Consequently, optimum hot working domain is determined to be 975–1150 °C/0.001–0.05 s−1. Complete DRX and subsequent growth of small DRXed grains result in a homogeneous microstructure, contributing to the optimal processing zone with η > 0.29.