The locations of disqualification of flaw detection for defects are accurately positioned through manual flaw detection of Q355NE plates with disqualification of online flaw detection as well as the microstructure and defects of the locations of disqualification of flaw detection are analyzed with optical microscope and electron microscope. The results showed that the defect corresponding to disqualification of flaw detection for Q355NE wind power steel was the microcrack in the center of steel plate, microstructure of the microcrack area in the center was martensite and bainite with poorer plasticity, which was caused by segregation of C and Mn. At the same time, MnS inclusions with long strip shape as well as compound of titanium and niobium distributed in chain are found at the crack. The interfacial bonding energy of them and matrix is low, continuity of matrix is destroyed so that cracks are easily initiated with the effects of stress. The microcracks in the center are avoided and qualification rate of flaw detection for wind power steel is increased by improving the segregation during solidification process of casting blank and adopting the mode of offline slow cooling of steel plate.

In the paper, the current situation of higher solid fuel consumption for 2^# sintering machine in 2^# Sintering Workshop of Iron-making Plant of Baotou Steel is systematacially analyzed. The fuel with comprehensive particle size>5 mm is controlled at 15%~20% and that with comprehensive particle size<1 mm is controlled at about 30% through classifying different fuel bands, putting them into tank and crushing them as well as controlling reasonable proportion of anthracite and coke powder; effective material layer thickness is increased and automatic heat storage effect is improved through increasing height of baffle for trolley of sintering machine to 750 mm and reducing thickness of bed charge from 85 mm to 70 mm; overdamp layer of sintering is reduced through reducing moisture of sinter mixture from 7.2% to 6.9%. The solid fuel consumption in 2^# sintering workshop is reduced significantly through taking the above measures. It reached 50.33 kg/t in 2023, which is 2.13 kg/t lower than that in 2021, which lays the foundation for further reducing energy consumption in working procedure before iron-making.

In this paper, the sealing device for patchhole of oxygen lance is redesigned based on the infinite space submerged turbulent jet theory and characteristic test of dominant frequency of oscillation for double-hole jet aiming at such phenomena as spill over of flue gas and flare-up often occurred at nitrogen sealing at oxygen lance of gasification cooling flue for converter. The new nitrogen sealing device adopts the design of seal chamber and double row of inclined holes are set on nitrogen seal seat as well as the aperture and angle of inclined hole are reasonably designed combining with theoretical calculations. It is applied on new 1^# converter of Steel-making Plant of Baotou Steel, in which the phenomenon of “smoking” in process of converting at oxygen lance as well as the frequency of cleaning and changing nitrogen seal cap for operators are reduced so that recovery amount of coal gas is improved. The engineering applications show that the modified sealing device is with such advantages as reasonable design, simple equipment and safe operations.

In this paper, it is analyzed the causes of abnormal temperature increase of side wall at tap hole for hearth of 7^# blast furnace of Baotou Steel and emphasized the treatment measures. With the long-term high-intensity smelting conditions, tap hole of hearth is relatively active and its length is controlled poorly so that scour of slag iron to carbon brick of tap hole is aggravated. As a result, the erosion of carbon brick of tap hole is the cause for temperature increase of side wall at tap hole for hearth of 7^# blast furnace. The temperature of side wall at tap hole is effectively controlled without reducing the smelting intensity and output of 7^# blast furnace through taking such measures as increasing the quantity of circulating water at tap hole to improve cooling intensity, carefully maintaining tap hole, actively eliminating air gap of hearth side wall as well as appropriately opening central gas stream and restraining gas stream at edge for the charging system.

In the paper, it is introduced a new type of wear resistant and low temperature resistant pearlitic rail with excellent performances is developed through designing material compositions and studying heat treatment process aiming at the operating environment of railway in alpine regions and performance requirements for service of rail. The test results showed that the improvement of impact energy of test steel at -40 ℃ was not obvious by adding 0.10% Ni on the basis of the chemical composition of 0.66%C-0.45%Si-1.10%Mn, but impact performance was more stable than that of test steel without Ni. After the heat treatment of test steel is started and temperature is increased to 780 ℃, the abnormal microstructure, martensite could be prevented to be generated as well as microstructure is pearlite and a small amount of ferrite and impact energy at -40 ℃ could reach 20.1 J.

When dry mechanical pump system is used to vacuumize for such vacuum refining systems as VD, VOD and RH, a large amount of dust generated in liquid steel will enter vacuum pipe with process gas. In order to protect vacuum pump, the precipitator needs to be installed in front of mechanical vacuum pump to remove dust in process gas. It is common to add a cyclone dust collector in front of bag filter so that occupied area is large as well as costs and operating costs are high. The precipitator introduced in this article is with the integrated structure of cyclone and bag. These two parts are installed in two compartments mode within one precipitator so that occupied area is small and costs are low. The integrated precipitator is with such characteristics as high dust removal efficiency, small pressure loss as well as convenient and rapid maintenance and repair through optimizing structural design so that long-term safe operations of dry mechanical vacuum pump are ensured.

In this paper, the combined process of low-nitrogen combustion+calcium-based desulfuration with fixed bed is proposed for flue gas treatment of heating furnace thorough comparing current common desulfurization technology with active carbon, SDS sodium-based desulfurization technology, calcium-based desulfurization technology with fixed bed and dry desulfurization technology with highly active calcium powder in metallurgical industry as well as selecting the desulfurization and denitrification technologies suitable for conventional walking beam reheating furnace of steel rolling mill by taking the ultra-low emission transformation for conventional walking beam reheating furnace of steel rolling mill as an example. After on-site implementation, the nitrogen oxides, sulfur dioxide and particulate matter in flue gas could all meet the ultra-low emission requirements so that the combined process could provide reference for enterprises in the same industry.

The treatment of high-salt wastewater has always been a problem for production enterprises since its salt content is high as well as it is difficult to be treated and cannot be directly discharged into the environment. The harmless treatment of high-salt wastewater is achieved by combining such technologies as membrane treatment, ozonation and evaporation crystallization as well as the salt in water is concentrated into such crystalline salts as sodium chloride and sodium sulfate. As a result, the treated water is for recycling circuit.

The small-diameter boiler tube is designed and developed through innovating process design as well as its quality indexes are improved by Inner Mongolia Baotou Steel Special Steel Pipe Co., Ltd. based on the requirements of group company, “break through and improve product quality”. The seamless steel pipe with outer diameter of 51~114.3 mm and wall thickness of 3.5~12 mm is rolled by continuous casting billet of Φ150 mm in the original design of the unit. The demand of small-diameter boiler tube with outer diameter of 38~48 mm and wall thickness of 3.5~8 mm in the boiler tube industry is greater. The seamless steel pipes of two groups of outer diameter produced with the billets of the same diameter is realized and their wall thickness accuracy is -7.14%~9.14% through researching and developing the technology of large tube reducing rate for continuous mill unit as well as producing the seamless steel pipe with outer diameter of 38~48 mm by continuous casting billet of Φ150 mm. When rolling small-diameter boiler tubes made of materials of 25MnG, 15CrMoG and 12Cr1MoVG, there are defects of “straight fold” on inner surface as well as “linear indentation” and “subsurface cracks” on outer surface of steel tube. Their causes are analyzed combining with the deformation process and material characteristics as well as the solutions are formulated so that qualified rate of ultrasonic flaw detection of product is increased from 86.82% to 91.32%. The heat-treatment schedule for small-diameter boiler tubes made of materials of 15CrMoG and 12Cr1MoVG is formulated as well as the mechanical properties of products are stable under this process schedule, which could meet the requirements of GB/T 5310-2017 standard.

In the paper, it is systematically elaborated the product defects when rolling H beam with universal pass as well as mainly discussed and analyzed from such two aspects as the steel defects and rolling defects of H beam aiming at the rolling process of H beam with universal pass in 1^# production line of Rail and Beam Rolling Plant of Baotou Steel. The steel defects include inclusions, scabs and cracks of product as well as rolling defects include dimension deviation, scratch and bending of product. The treatment methods and optimization measures are put forward according to different types of defects. The amount of waste products caused by unqualified H beam is reduced by taking such measures as reasonably controlling rolling reduction, optimizing guide and controlling rolling speed as well as optimizing control process. As a result, the first pass yield and yield of H beam are improved so that economic benefits are increased.