In steel works, flammable gas which generated in the manufacturing process, are used as fuel in the factory. Long pipeline is land to convey these flammable gases. Because serious accidents such as leakage of flammable gases may occur due to pipe corrosion and wall thinning, so periodic inspection of pipe is conducted. Generally, flammable gas pipes are inspected by ultrasonic thickness gauge, but the inspection area is limited.

Therefore, a remote-control wireless inspection robot is developed to expand the pipe inspection area. A robot capable of circumferential and extensive screening inspection on pipes with a diameter of 500 mm or more has been developed by combining eddy current testing using a permanent magnet, which consumes less power and does not require a contact medium, with a design that allows the body to move along the diameter of the pipe using a link mechanism. And the crawler, equipped with permanent magnets in its four wheels, is held to the surface of the steel pipe by suction. Additionally, a function to estimate self-position using an IMU (Inertial Measurement Unit) and encoders has been incorporated, enhancing the robot's practicality by visualizing the moving path on the pipe, weld beads, and thickness reduction on the inspection color map.

The robot moved on the pipe, generated the inspection color map, and successfully detected the simulated weld bead and the simulated defect on the moving path.

The work to remove the defects generated on the steel pipe surface by grinding is required to be automated because of the large load on the worker. Although automatic machining by large equipment is carried out, there is a problem of low efficiency. The authors proposed a system to automatically remove only surface defects using a 3D camera and a grinder held by a robot arm.

This system is composed of a 3D camera capable of measuring the shape of the steel pipe surface, including defect areas to be maintained, a processor and controller that automatically generate grinding operations, a robot arm as an actuator, and a pressure control device that maintains a constant grinding pressure, which is the grinding device. In this system, the shape of the grinding object is extracted by combining three-dimensional shape measurement and point group processing with two-dimensional image processing, and the machining locus including the tool contact attitude and the motion of the robot are automatically generated based on the shape.

In addition, it became possible to obtain a smooth and high-quality grinding profile by controlling the grinding depth by a pressure control device and controlling the feed rate during machining. By introducing this system into the factory, work efficiency has increased by approximately 2.5 times. And, the production process was made safe, and the engagement of the workplace was improved, because the worker did not handle the dangerous grinder directly.

Fire and explosion accidents with equipment troubles directly lead to long-term shutdowns and labor accidents related to human lives in ironworks. Panoramic thermal monitoring that can syn-thesize multiple thermal images at different viewpoints is strongly demanded for wide-area infra-structures such as material yards. In this study, we develop a mirror-drive pan-tilt telephoto infra-red camera that enables quick viewpoint switching to different directions without moving its heavy camera body and realize to capture a panoramic thermal image of 8320×4320 pixels in the view angle of 93×46 degrees by stitching 117 thermal images at intervals of 24 s in the fastest case. We demonstrate its effectiveness by verifying panoramic thermal images for material yards in ironworks and superimpose the panoramic thermal images on their 3D point cloud data toward digital-twin-based thermal monitoring.

The formation behavior of the plating films of Zn−V composite electroplated steel sheets was investigated using electrochemical techniques, and the paint adhesion and heat absorption/dissipation properties were investigated. In Zn−V composite plating, V compounds were preferentially deposited at the initial stage of plating, subsequently Zn was deposited in the form of an electric field-oriented fiber structure. As plating progressed, Zn−V composite plating films consisting of an electric field-oriented fiber structure of Zn and a non-electric field-oriented structure of V compounds were formed, and V compounds were codeposited in the gaps between Zn platelet crystals. The critical current density for initiating Zn plating was about 20 times higher in Zn−V bath than in Zn bath. In Zn−V bath, at the potential range more noble than that for initiating Zn plating, since V ions were reduced from tetravalent to trivalent along with the hydrogen evolution, the critical current density seems to be higher. The Zn−V composite plated steel sheets had better paint adhesion than EG. The excellent paint adhesion is attributed to the anchor effect caused by the large surface roughness and the formation of chemical bonds between the paint films and the oxide or hydroxide of V in the plating films. The Zn−V composite plated steel sheets had a higher emissivity than electrogalvanized steel sheets (EG). As a result, the emissivity after chemical conversion coating was high, and the sheets had high heat dissipation. This seems to be due to the oxide or hydroxide of V in the Zn−V plating films.

The permanent strengths of interstitial-free (IF) steels with different grain sizes and dislocation densities processed by severe plastic deformation (SPD) and subsequent annealing are systematically investigated. Permanent strength, which is athermal and time-independent, corresponds to the fundamental capability to bear stresses caused by external forces. Sufficiently long-time (24 h) stress relaxation tests were carried out and experimental stress–relaxation time relationships were extrapolated to estimate the permanent strength that remained after an infinite time passed. The flow stresses observed in standard uniaxial tension tests increased with repeated SPD processes, and the fraction of permanent strength to the observed flow stress was mostly above 65%. The permanent strength also increased with repetition of SPD processes, and subsequent low-temperature annealing further augmented the permanent strength. During SPD processes, the dislocation-related strengthening was dominant, while the grain-size-related strengthening was minor, i.e., the Hall–Petch relation does not hold. On the other hand, after low-temperature annealing, the grain-size-related strengthening became dominant, quickly replacing the dislocation-related strengthening. In a coarse-grain region, the grain-size-related strength was consistent with the classical Hall–Petch relation. It was confirmed that the original Hall–Petch relation holds only in the coarse-grain region and it indicates “softening with grain coarsening due to annealing”, not “strengthening by grain refinement due to SPD”.

It is known as Al₂O₃ dispersed with Ni particles composite (Ni/Al₂O₃) has self-healing function which recovers mechanical properties by the high-temperature oxidation of dispersoids. Ni/Al₂O₃ appear self-healing function not only by the contribution of high-temperature oxidation of Ni particles exposed on sample surface, but also contribution of grain boundary diffusion of Ni ions through Al₂O₃ matrix. The objective of this study is to investigate the influence of Ni ion diffusion on the growth of NiAl₂O₄ self-healing layers with different Ni volume fractions.

Dence Ni/Al₂O₃ were prepared and etched nitric acid to remove surface Ni particles. Samples were heat treated at 1100–1355°C for 6–48 h in air.

NiAl₂O₄ self-healing layer is observed on the sample surfaces with and without etching. The NiAl₂O₄ self-healing layer grows with parabolic manner with respect to the heat treatment time, indicating that the diffusion of Ni ion through the Al₂O₃ grain boundary is the rate-controlling. The contribution of surface Ni to the growth of NiAl₂O₄ layers is independent of heat treatment conditions due to the surface Ni particles are defined by the Ni dispersion ratio. The contribution of Ni ion diffusion increases linearly with increasing Ni volume fraction. It indicates that the amount of Ni ions diffused through the grain boundary is proportional to the Ni volume fraction.

The authors have studied integrated steelworks that are able to achieve carbon neutrality. The process used in the study was a combination of a blast furnace and a pre-reducing furnace. The cases where hydrogen and ethylene were used as fuel were compared based on numerical simulations. As a result, it was found that when hydrogen was used, the reduction in CO₂ emissions from the entire steelworks was only 45%, whereas when ethylene was used, CO₂ emissions from the entire steelworks could be reduced by 86%. Ethylene can be obtained by the dehydration reaction of bioethanol, and can also be synthesized using surplus renewable electricity, which is expected to increase in the future, and CO₂ emitted from steelworks.