Iron and steel slags are being used, on a trial basis, as environmental remediation agents for marine sediments in rocky coastal waters. In addition to chemical risk such as component leakage of slag into the environment, formation of biofilms is inevitable due to the adhesion of environmental microorganisms to slag surfaces. The transformation of free-living microorganisms into biofilm forms not only alters microbial behavior and various physicochemical tolerances, but also changes the properties of the material. However, the impact and effects of biofilms on materials remain unclear due to the challenges of performing detailed analyses of biofilms on materials such as chemically active slag. Therefore, in this study, slags coated with biofilms were prepared and their chemical effects were investigated to determine whether microbes improve slag function. Furthermore, prior to determining the effects of the slag coated with biofilm, quantitative evaluation techniques for assessing slag biofilms were developed. The review is specifically focused on accurate quantitative evaluation methods for assessing biofilms on slag. Additionally, changes in the chemical properties of slag-coated biofilms are summarized. This technique for modifying slags using microbial biofilm can be applied to the development of novel materials, not only for slag but also for other materials, as material processing and surface treatment technology.

The chemical structure models for the extractions and residues of two types of bituminous coals, A and B, were constructed. The molecular weights of the extractions were determined via gel permeation chromatography (GPC). New standard materials with structures similar to those of coal extraction (i.e., 9, 10- diphenylanthracene, 5,6,11,12-tetraphenylnaphthracene, and chemical compounds A (Mw = 811) and B (Mw = 1135), which were synthesized using the coupling reaction) were adopted for GPC in order to obtain more accurate mean molecular weights than those in literature. Furthermore, a support program for constructing chemical structure models based on ¹H nuclear magnetic resonance (NMR) spectra was adopted. The coal models constructed suitably indicate the differences between the types of coal. In particular, it is found that a high pyridine-insoluble fraction extracted rate, which accounts for the most significant difference between the total extracted rates for coals A and B, enhance the coking property of coal A. In addition, the cluster size in the magic solvent-insoluble fraction might affect the softening property of coal.

The effect of C content on the formation of V carbide layer on carbon steels by a powder packed method was investigated. The continuous duplex carbide layer consisting of an outer V₂C and inner V₆C₅ and V₈C₇ layers was formed on Fe-0.7C and Fe-0.3C (in wt.%), but it was discontinuous on Fe-0.1C. Internal carbide precipitates were observed within the matrix in Fe-0.3C and -0.1C. These precipitates in Fe-0.1C were disappeared after long treatment. The inner carbide layers were confirmed to grow inwardly, which suggests that VCl₂ gas can penetrate through the carbide layers to the steel substrate.

Controlling the primary recrystallization texture is important to improve the magnetic properties of grain-oriented electrical steel through secondary recrystallization. To understand the factors influencing fine precipitates on the primary recrystallization mechanism and texture formation, changes in the recrystallization behaviors with states of precipitates (extremely fine, and coarse) were investigated through cold rolling, pre-annealing, and primary recrystallization annealing in Fe-3%Si alloy with coarse Goss ({110}<001>) grains using EBSD and TEM. Extremely fine MnS precipitated during the recovery stage had significant effects on the suppression of further recovery and recrystallization, especially after pre-annealing at 550°C. Recrystallized Goss grains were observed after primary recrystallization annealing by nucleation and growth irrespective of the states of precipitates; however, in the steel with extremely fine precipitates, {111}<112> grains remained through primary recrystallization annealing. It is assumed that fine precipitates would inhibit the growth of Goss grains and keep {111}<112> orientation, the main orientation in the cold rolled sheet, which would indicate occurrence of continuous recrystallization.

We systematically investigated changes in crystal orientation due to the cold rolling of a {110}<110> single crystal, which had not been researched to date, in a reduction range of 10–70%. The results allowed for a classification of the changes into the following three reduction cases. The first was a 10–20% reduction. For this reduction, there was almost no change in the matrix orientation, and a shear band slightly appeared near the surface layer. The second was a 30–50% reduction, at which many shear bands were introduced, and the crystal orientation inside the shear bands was rotated from the initial {110}<110> orientation to the {100}<001> orientation around the TD axis. There are cells in the shear band. And {100}<001> orientation cells are considered having lower strain than around cells to having lower GAM. Additionally, the {111}<211> orientation was also confirmed in a small area that was thought to be surrounded by shear bands. The third was a 60–70% reduction, at which the matrix rotated to {111}<110>, but there were some areas with a {111}<211> orientation. Furthermore, the shear bands increased with increasing reduction, and more inner orientations were observed for {111}<211> than for {100}<001>. {111}<211> bands and {100}<001> bands are considered different origins to change discontinuously.

The effect of dislocation density on hydrogen embrittlement resistance of tempered martensite in low alloy steels was investigated quantitatively. The various samples of which dislocation density was from 0.7×10¹⁴ m⁻² to 4.5×10¹⁴ m⁻² were prepared by changing tempering temperature and C content. Then, the yield stress of the samples was between 780 MPa and 1020 MPa. Especially, the change of the C content made various dislocation density samples even though the yield stress is almost same. The hydrogen embrittlement resistance was estimated with four-point bend test. The hydrogen embrittlement resistance decreases with increasing the dislocation density and the yield stress. Although the critical yield stress was changed dramatically by changing C content, the critical dislocation density was almost same (about 2.0×10¹⁴ m⁻²) even though the C content was different. In addition, the absorbed hydrogen content correlated with the dislocation density, and did not depend on the C content in this research. This means that the dislocation density is higher, the hydrogen trapping ability is higher. As the result, when the absorbed hydrogen content reach the critical diffusible hydrogen content, hydrogen embrittlement cracking occurs probably.