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 pipeline steel is mainly used for transportation of oil and natural gas as well as the acid service condition means that there are such acidic mediums as H₂S,CO₂ and H⁺ in application environment, so pipeline steel in acid service condition is the pipeline steel with resistance to hydrogen induced corrosion cracking. In the paper, the development and industrial production of X46MS hot rolled coil are mainly introduced. The development includes chemical components, hot rolling process and production technology process as well as the performance tests include pulling, bending, impact, hardness, metallography, non-metallic inclusions and hydrogen induced cracking (HIC). The test results showed that the chemical components and process design of X46MS hot rolled coil in acid service condition were reasonable as well as it was with pure steel, well-closed formation and excellent mechanical properties, especially the resistance to hydrogen induced cracking.

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.

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.

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 liquid steel could be purified, inclusions could be modified and steel could be microalloyed by adding rare earth into steel, which could reduce the harmful effects of inclusions on steel so that the plasticity, toughness and resistance to low temperature impact of steel could be improved. In order to study the effects of different rare earth contents on properties of steel, the smelting of low alloy high strength steel with manganese and different quantities of rare earth added and without rare earth are carried out using the 25 kg vacuum medium frequency induction furnace as well as the rolling with production process on site is simulated. Moreover, the chemical composition, mechanical properties, fracture and metallographic structure of rolled products are analyzed. The results showed that the grain size of microstructure for steel could be refined by adding rare earth into steel; with the increase of rare earth content in steel, refined grain size of microstructure makes the resistance to crack formation and propagation between grain boundaries increased so that the plasticity, impact toughness and mechanical properties of steel are improved.

In this paper, the effect laws of adding a certain proportion of high silicon Brazilian coarse powder ore into sintering on its technical indicators and quality of sinter with current raw material conditions of Baotou Steel are studied. The experiment showed that the complementary ore proportioning could be realized by adding a certain proportion of high silicon Brazilian coarse powder ore taking the ore proportioning structure that the self-produced iron ore concentrate by Baotou Steel adding Australian limonite and semi limonite as the main framework, which was conducive to improving the quality of sinter. The industrial experiment showed that the rate of sintering finished products, drum strength of sinter and size composition were improved after add the high silicon Brazilian coarse powder ore into sintering of Baotou Steel.

In this paper, the influences of super-thick material layer on sintering process indexes as well as productivity and quality of sinter based on the iron material configuration condition that high proportion of iron concentrate of sintering of Baotou Steel are mainly elaborated. The study results showed that the FeO content of sinter could be significantly reduced by increasing thickness of sintering material layer, the thickness of material layer was increased from 700 mm to 1 000 mm and the FeO content of sinter was decreased by 1.39 percentage points, or 14.2%. The solid fuel consumption of sintering could be effectively reduced, yield and drum strength of sinter could be improved by increasing the thickness of sintering material layer. In this paper, such indexes as the fuel consumption, yield, drum strength, RI and RDI_{+3.15 mm} of sinter tend to be increased then decreased with the thickness of material layer increases as well as they are optimal when the thickness of material layer is 800 mm, which shows that the suitable thickness of material layer is 800 mm with the iron material configuration condition of 20% Barun iron concentrate+20% Mongolian iron concentrate+60% imported iron ore powder.

In the paper, it is introduced the experimental study on heat treatment at a series of temperatures of 1 000~1 250 ℃ was carried out by taking the Fe-Mn-Al-C high manganese austenitic test steel as object of study. The surface oxide layer, microstructure and grain size of test steel were detected and analyzed separately. The results showed that the thickness of surface oxide layer increased with heating temperature increased, there was grain boundary oxidation when heating temperature was above 1 150 ℃; the grain size of test steel increased with heating temperature increased, there was mixed crystal at 1 150 ℃ and the grain size increased obviously at 1 250 ℃.

In the paper, it is found that the hardness and wear resistance of working layer for cast iron roll are improved as well as the labor costs are reduced by developing continuous rolling concave roll with the metal spraying process through optimizing such key control points as the chemical composition and production process of continuous rolling roll as well as comparing and analyzing its mechanical properties and microstructure before and after optimization, which provide the technical basis for developing large grooved roll and roll collar in future.