In the paper, the design, main components and features of high pressure water descaling system in the production line of heavy plate of Baotou Steel are introduced and analyzed. Moreover, the system equipment is improved based on the experiences of on-site maintenance and fault handling for high pressure water system in the production line, which is with greater reference significances for the design, maintenance, fault diagnosis and optimization of high pressure water descaling system in the production line of heavy plate.

In the paper, the falling accident caused by stomping on color plate is analyzed with fault tree. It is with the qualitative and quantitative analysis through drawing fault tree and successful tree as well as the fault tree is simplified with the Boolean algebra principles so as to obtain the minimum cut set and path set, probability of occurrence of top event, importance degree of basic event structure of fault tree as well as important links of accidents so as to provide the basis for preventing accidents. The results showed that the casualty accidents of falling caused by stomping on color plate were mainly due to such factors as ineffective safety belts, damaged upholder, stomping on color plate and loss of balance of body so that the measures should be taken to control them.

The trace amount of refining grain elements are added into carbon manganese steel as well as the heat treatment method of quenching and tempering is applied in production based on the standard. The mass production results showed that the mechanical properties could meet requirements and toughness was good. After the heat treatment of quenching and tempering, the yield strength of steel tube is not less than 500 MPa, tensile strength is not less than 620 MPa, longitudinal elongation is not less than 20%, average longitudinal impact value at -20 ℃ is not less than 180 J and the performances could meet customer's requirements; carbon equivalent is controlled below 0.44 to ensure the subsequent weldability.

The causes for lower qualified rate of transverse low temperature impact toughness at -20 ℃ of SM490YB hot-rolled H beam for offshore oil platform are analyzed with such instrument and equipment as the optical microscope, scanning electron microscope and energy spectrometer. The results showed that the poorer low temperature impact toughness of test steel was caused by large Al₂O₃ inclusion, harder bainite structure, coarse grain and banded structure in the steel. The transverse low temperature impact toughness at -20 ℃ of test steel is improved obviously and qualified rate of impact at -20 ℃ is increased from 80% to 100% by reducing carbon content of test steel as well as optimizing smelting and rolling processes so that the grain size and inclusions of test steel are refined as well as types of microstructure are optimized.

In the paper, the design thought and development of Φ73 mm pass series for FQM (Fine Quality Mill)-Φ100 mm mandrel pipe mill with six stands are mainly introduced. When design this series of pass of mandrel pipe mill, the “distribution method of coefficient of elongation on top of pass” is adopted so that the applications of development technology of minimum pass series of mandrel pipe mill with retained mandrel are realized. The industrial results showed that the wall thickness accuracy of seamless steel pipe produced by the pass of mandrel pipe mill designed with this technology is within±8% as well as the internal and external surface qualities of steel pipe are good.

In the paper, it is introduced the mineralogical characteristics of minerals named by geographical names and person names in Bayan Obo ore deposit. There were once 7 kinds of minerals named by geographical names, but 3 kinds are confirmed at last as well as there are 5 kinds of minerals named by person names. They are all new minerals, of which the Nioboixiolite-(□) is the most recently approved new mineral. The minerals named by geographical names are with not only their own narrow mineralogical meanings, but also other generalized meanings. The narrow meaning of minerals named by geographical names refers to just a specific kind of mineral, while their generalized meaning usually refers to various ores produced in the region.

The phase transformation law is analyzed through determining the transformation kinetics curve of supercooled austenite for U71Mn steel. The effects of cooling rate and finish cooling temperature on microstructure and hardness are studied with the thermal simulation tests of sectional type cooling strengthening based on the heat treatment process of rails on site. The results showed that the critical cooling rate of perlitic transformation for U71Mn steel was 7 ℃/s and temperature range allowing perlitic transformation was 500~600 ℃. The reasonable process parameters of sectional type cooling for U71Mn steel were that the starting cooling temperature was 850 ℃, cooling rates was 6~12 ℃/s and finish cooling temperature was 570 ℃. The perlite structrure could be obtained with this process parameter and it could meet the hardness requirements of rails.

The causes of cracks are analyzed through the observation with metalloscope and scanning electron microscopy aiming at the problem that product quality is affected by the microcracks on surfaces of web and flange of Q420NHB weathering resistant H-shaped steel. The results showed that the surface defects of flange were caused by the subcracks and intercrystalline cracks on inner arc of ingot blank, while the surface defects of web were caused by the pressfit of scale on surface of ingot blank during rolling process. The surface quality of weathering resistant H-shaped steel is effectively improved through optimizing the cooling process of crystallizer and rolling technology during continuous casting process.

The static continuous cooling transformation (CCT) curves of N80 grade steel for ERW oil casing with and without Mo are determined by Formaster-F full automatic phase transformation meter as well as the microstructures of the two types of steel at different cooling rates are observed with optical microscope. The results showed that the critical points of test steels of N80 grade steel for ERW oil casing, Ac₁ and Ac₃ were basically not affected by Mo element as well as the critical cooling rate for test steel 1 and 2 to start generating martensitic structure was 8 ℃/s. The interval range of cooling rate for bainite transformation of the test steels is expanded due to addition of Mo element and their microstructures are refined.

The fuel ratio is the main economic and technical index for blast furnace ironmaking, so it is of great significance for energy conservation and emission reduction of enterprise to reduce it. In this paper, the reasons for high fuel ratio of 6^# blast furnace of Baotou Steel are analyzed. After the overhaul and blow-in of 6^# blast furnace, the fuel ratio of blast furnace is reduced through taking such measures as tackling key problems in improving production to stabilize the feed of blast furnace, improving quality of raw fuel, strictly controlling differential pressure in blast furnace operation, adjusting charging system, stabilizing high blast temperature, reasonable use of enriched oxygen and coal injection as well as strengthening basic management. The cumulative fuel ratio in 2021 was 545.84 kg/t, which was 10.58 kg/t lower than that in 2020.