Numerical Simulation and Experimental Investigation of Rotating Blade Centrifugal Jet in Slurry Blast Device Used for Steel Strip Descaling

Under the requirement of clean production, a new type of slurry blast device for mechanically removing oxide scale on the surface of steel strips is presented, which can avoid the serious problems of rapid wear, low service life, and low efficiency of the traditional abrasive water jet with a nozzle. In this paper, the numerical simulation of the rotating blade centrifugal jet in the slurry blast device is conducted based on CFD, where the DPM and the erosion model are innovatively employed to simulate the movement characteristics of abrasive particles and the erosion rate of mixed slurry on the surface of the steel strip. Simulation results show that the erosion rate and particle motion velocity are proportional to the blade rotation speed and inlet pressure. Reasonable inlet pressure and rotation speed are helpful for improving the rust removal efficiency of slurry blast devices. An experimental system is established to validate the simulation results. The experimental results are consistent with the simulation trend, which exhibits that the developed slurry blast device is feasible for steel strip descaling. This work will play substantial guiding roles in the engineering optimization of slurry blast devices for steel strip descaling.

An Experimental Study on the Seismic Performance of High-Strength Composite Shear Walls

In order to study the seismic performance of high-strength concrete composite shear walls with embedded steel strips, four tests for high-strength concrete composite shear walls with embedded steel strips (SPRCW-1 to SPRCW-4) were constructed and tested. Based on the test results, a discussion is provided in the present study on the hysteresis curve, backbone curves, and strain of steel plate and distributed reinforcement of high-strength concrete mid-rise and high-rise composite shear walls with embedded steel strips under different steel ratios and different steel strip positions. The test results reveal that in high-strength composite shear walls with embedded steel strips, the ductility of the test specimen can be effectively improved when the ratio of the steel strip reaches a certain level. In parallel, when the embedded steel strip is placed on both sides of the walls, the steel strip can function better. The ultimate displacement is better than when the steel strip is placed in the middle of the walls, and can effectively improve the seismic performance of the walls. The scheme with embedded steel strips is more convenient and economical for construction, which is suitable for popularization and application in middle-high buildings in highly seismic regions.

Iron-based intermetallic particles formation in Al-Zn-Si alloy through powder metallurgy route

Corrosion of the steel products is one of the significant challenges which is managed by coating with Al-Zn-based alloys. The Galvalume alloy (Al-55%, 43.5%-Zn, Si-1.5%) is coated on steel strips via a hot-dipping process. The dissolution of iron (Fe) from steel strips and the formation of Fe-based intermetallic particles is an inevitable phenomenon during the hot-dip coating process. These intermetallic particles are a primary source of massive bottom dross build-up in the coating pot and metal spot defects in the coated steel products. Therefore, it is important to investigate the formation of Fe-based intermetallic particles. In this study, Fe-based intermetallic particles are produced via the powder metallurgy route. High energy ball milling was used for mechanical alloying of aluminum (Al), iron (Fe), silicon (Si), and zinc (Zn) powders. Optimized ball milling conditions were identified after a series of trials. After cold pressing, the mechanically alloyed samples (pellets) were sintered at various conditions in a high vacuum sintering furnace. The X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy-dispersive X-ray diffraction (EDS) were used for the analysis of raw material, mechanically alloyed powders, and sintered pellets. It is concluded that the mechanical alloying of 6h and cold pressing at 9 tons for 30 min is sufficient to produce a dense compact material. It was found that Fe-based intermetallic particles were successfully fabricated which were α-AlFeSi. However, intermetallic particles similar to those found in the bottom dross of the coating pot are difficult to fabricate through the powder metallurgy route due to the volatilization of Zn during the sintering process.

Experimental verification referring to the new shape of the perforated steel strip

Perforated steel strips are used as reliable shear connectors many years. During this time, many different shapes of the openings or recesses were developed to improve the durability and resistance of the shear connection. Behaviour of these strips were mainly verified by experimental research, but many parameters could not be measured. Numerical analysis provides not only easy and fast way of testing the behaviour of specimens, but also the possibility to improve the geometry of the strips. Modified steel strips can be deeply investigated in simulations and subsequently verified by push-out tests in laboratories. The combination of these two methods can bring the spectrum of the information that can complexly describe the behaviour, durability and also the weak points of the shear connection, especially in case of the new or modified shape.

Defectoscopic and Geometric Features of Defects That Occur in Sheet Metal and Their Description Based on Statistical Analysis

Features of the defect class “scratches, attritions, lines”, their geometric structure, and their causes are analyzed. An approach is developed that defines subclasses within this class of technological defects based on additional analysis of morphological features. The analysis of the reasons for these subclasses allows additional information to be obtained about the rolling process, identifying additional signs of defects, regulating the rolling conditions of steel strips more accurately, and diagnosing the equipment condition.

An Impedance Sensor for Distinguishing Multi-Contaminants in Hydraulic Oil of Offshore Machinery

The cleanliness of hydraulic oil can reflect the service life of the oil and the wear state of hydraulic machinery. An impedance sensor is proposed to distinguish multi-contaminants in hydraulic oil. The impedance sensor has two detection modes: the inductance-resistance mode is used to detect metal debris, and the capacitance mode is used to distinguish water droplets and air bubbles. By adding a built-in silicon steel strip and an external silicon steel strip with high magnetic permeability, the distribution area, strength, and uniformity of the magnetic field are enhanced to improve the detection sensitivity under inductance and resistance parameters. In addition, the silicon steel strips are used as electrode plates to introduce capacitance parameter detection. The experimental results show that the resistance detection method based on coil successfully improves the detection ability for non-ferromagnetic metal debris. The impedance sensor for distinguishing multi-contaminants in hydraulic oil can provide technical support for fault diagnosis of offshore hydraulic machinery.

Smoothing Complete Feature Pyramid Networks for Roll Mark Detection of Steel Strips

Steel strip acts as a fundamental material for the steel industry. Surface defects threaten the steel quality and cause substantial economic and reputation losses. Roll marks, always occurring periodically in a large area, are put on the top of the list of the most serious defects by steel mills. Essentially, the online roll mark detection is a tiny target inspection task in high-resolution images captured under harsh environment. In this paper, a novel method—namely, Smoothing Complete Feature Pyramid Networks (SCFPN)—is proposed for the above focused task. In particular, the concept of complete intersection over union (CIoU) is applied in feature pyramid networks to obtain faster fitting speed and higher prediction accuracy by suppressing the vanishing gradient in training process. Furthermore, label smoothing is employed to promote the generalization ability of model. In view of lack of public surface image database of steel strips, a raw defect database of hot-rolled steel strip surface, CSU_STEEL, is opened for the first time. Experiments on two public databases (DeepPCB and NEU) and one fresh texture database (CSU_STEEL) indicate that our SCFPN yields more competitive results than several prestigious networks—including Faster R-CNN, SSD, YOLOv3, YOLOv4, FPN, DIN, DDN, and CFPN.