With the increasing development and utilization of marine resources, corrosion of structural materials of marine engineering is facing severe challenges. In this article, it is summarized the research progress on corrosion status of steel in marine environment as well as deeply analyzed such influencing mechanisms as marine atmosphere, splash zone of seawater, tidal and splash zone as well as immersion zone of seawater on corrosion behavior of steel. The main current technical measures to retard corrosion of steel in marine environment are summarized as well as development direction and application prospect in future marine engineering of new corrosion-resistant steel are discussed by discussing the effects of such environmental factors as dissolved oxygen, salinity, temperature, pH value and microorganism on corrosion rate of steel aiming to provide the technical support for improving corrosion resistance of structural materials of marine engineering.

The experimental study on discarding tailings in advance is carried out for raw ore to be ground and ore discharged by primary ball mill of a mine with the processes of dry-type and wet-type discarding tailings in advance based on studying process mineralogy of low grade iron ore in the mine as well as size composition of raw ore to be ground and ore discharged by primary ball mill in the existing process. The experiment results showed that the tailings with productivity of 28.27% and content of magnetic iron of 0.44% could be discarded for raw ore to be ground with dry-type discarding tailings in advance; the tailings with productivity of 33.44% and content of magnetic iron of 0.49% could be discarded for raw ore to be ground with wet-type discarding tailings in advance; the tailings with productivity of 41.39% and content of magnetic iron of 0.36% could be discarded for ore discharged by primary ball mill with wet-type discarding tailings in advance.

In the paper, it is introduced the studies on fixed flash welding process of 380HB grade high strength heat treated rare earth rail and normalizing process of joints are carried out with the common fixed flash welder and heat treatment equipment for normalizing of joints at home and abroad. The optimal welding process and heat treatment process of joints are summarized through comparing and analyzing the qualified rate of drop weight tear test, area of grey-spots and Rockwell hardness of longitudinal section for joints with different processes. For the joints of fixed flash welding for obtained 380HB grade high strength heat treated rare earth rail, the mean values of tensile strength R_m, elongation after fracture A and impact energy at room temperature KU₂ are 1 141 MPa, 12.5% and 16.0 J respectively, hardness ratios of joints H_J/H_P is 0.92, H_J1/H_P is 0.84 as well as width of softened zone for joints W≤15 mm so that the mechanical properties and microstructure of joints could all meet the standard requirements. As a result, the problems of lower hardness and drop hammer fracture of flash joint for high strength heat treated rail are solved so that the excellent performance matching of welded joints and rail could be achieved, which could meet the requirements of wear resistance and compliance for heavy-haul railway to joints of high strength heat treated rail.

In the article, it is mainly introduced the hot-dip galvanized green steel product BTRC20 for home appliances is successfully developed by adding over 20% scrap steel as well as utilizing existing process equipment of smelting, hot rolling, cold rolling and galvanizing of Baotou Steel. Its yield strength is 212~279 MPa, tensile strength is 331~368 MPa and elongation is 31.0%~50.5%. Various indexes of developed hot-dip galvanized steel sheet BTRC20 for high-end home appliances such as mechanical properties, corrosion resistance and coating performance could all meet the technical standard of delivery. It is widely used for manufacturing the out board of such high-end home appliances and office equipment as computer, server, audio equipment and automatic office system, which is with stable bulk supply capacity.

In the design of blast furnaces in Baotou Steel, “long campaign of blast furnace” is always the subject. In order to adapt to the smelting of special ore in Bayan Obo, blast furnace profile is gradually developed towards low shaft, the part below middle of blast furnace shaft is constructed with microporous alumina carbon brick instead of carbon brick, thick furnace lining is gradually changed to thin skinned lining, furnace hearth is with domestic large carbon brick and high heat-conducting UCAR carbon brick as well as low heat-conducting furnace hearth is changed to high heat-conducting furnace hearth. The production technology management system that could ensure stable and smooth operations of blast furnace, high output and low consumption as well as campaign of blast furnace to be over 15 years is formulated through paying attention to construction quality, optimizing cooling equipment and medium parameters, adhering to the principle of beneficiated burden material, controlling contents of harmful elements as fired, keeping furnace hearth active as well as strengthening technologies and management measures at later stage of campaign.

In the energy consumption of sintering process, solid fuel (powdered coke and anthracite) consumption accounts for 70%~80%, so it is the key to reduce solid fuel consumption for reducing energy consumption of sintering process. In the paper, it is introduced the air leakage rate of sintering machine is decreased to 35% and effective height of sinter bed is increased to 780 mm through such measures as equipment transformation, optimizing technological operations and strengthening production management combining with the existing conditions of raw materials and fuels aiming at the problem of higher solid fuel consumption for 265 m² sintering machine of Baotou Steel; proportion of size fraction of outsourced powdered coke <1 mm for sintering is decreased from 41.02% to 22.72% through revising the purchase standard of outsourced fuels for sintering so that size composition of fuel for sintering is improved. The solid fuel consumption for 265 m² sintering machine of Baotou Steel was reduced to 50.75 kg/t in 2023 through the above measures, which was 1.70 kg/t lower than that in 2021.

In the paper, the study on effect laws of ore proportioning structure on quality of pellet is carried out aiming at such problems as low strength and high reduction swelling rate of manufactured pellet caused by high contents of such harmful elements as K, Na, F and S in iron ore concentrate of Bayan Obo. The study results showed that the pellet could be promoted to be fully oxidized, compressive strength of pellet could be improved and reduction swelling of pellet could be restrained by adding high silicon hematite and high magnesium magnetite with low contents of sulfur and alkali metal. The compressive strength of pellet could be significantly increased to 2 380 N and reduction swelling rate could be reduced to 13.2% with the scheme of optimizing ore proportioning that 52% iron ore concentrate of Bayan Obo+32% high silicon and low sulfur magnetite concentrate+8% high silicon hematite concentrate+8% high silicon high magnesium magnetite concentrate, which could provide the theoretical support and technical path for preparing high quality pellet with iron ore concentrate of Bayan Obo.

In the paper, the effects of adding rare earth element Ce into Cr12MoNiNb mold steel on its inclusions and mechanical properties are studied. The morphology, size and composition of inclusions are observed and measured with scanning electron microscope, energy spectrometer and field emission electron probe. The size, quantity and precipitation law of inclusions are statistically analyzed with analysis software as well as hardness and room-temperature impact energy of samples are measured with Vickers hardness tester and impact tester. The results showed that circular or elliptical composite inclusions containing rare earth were formed in the mold steel after adding 0.002 8% of rare earth Ce and quantity of inclusions was decreased by 21.43% compared with those of the steel without adding rare earth elements so that liquid steel was purified; average size of inclusions was decreased from 3.95 μm to 3.13 μm, which was decreased by 20.76%. The hardness and room-temperature impact energy of mold steel are increased by adding rare earth Ce. Its Vickers hardness (HV) is increased from 263.0 to 283.0 and room-temperature impact energy is increased from 16.65 J to 20.05 J, which is increased by 20.42%.

In the detection of building foundation piles, crosshole sonic logging is the important detection method to judge the integrality of pile body for cast-in-place concrete pile. In this paper, it is introduced the basic principle and judgment basis of detecting integrality of pile body with crosshole sonic logging as well as summarized the process flow and matters needing attention of on-site detection by taking the project of archives center in a city as an example, which provide accurate detection data for the quality of foundation pile in project.

In the paper, the technical progress of ironmaking system of Baotou Steel is summarized and analyzed. It is thought that the technological breakthrough and innovation of beneficiation, sintering and smelting problems for special iron ore of Bayan Obo are fundamental guarantee for achieving the ironmaking production with high efficiency and quality, low consumption, long service life and environmental protection as well as technical support of great-leap-forward development for ironmaking of Baotou Steel.