Inner Mongolia Baotou Steel Pipe Co., Ltd. owns the world's advanced production unit of seamless steel pipe as well as the main products are various hot rolled seamless steel pipes and piercing plug, the hot tool matched with piercing process of several hot rolling production lines are manufactured by the company itself. The causal chain analysis is carried out aiming at the existing problem of low yield for casting piercing plug. The process of casting system for piercing plug is optimized through taking such scheme as increasing the porous sand core of riser manufactured by exothermic materials, installing weighing device and injection of nitrogen at the bottom of moulding flask so that the above technical problem is solved.

The contents of calcium oxide, silicon dioxide, magnesium oxide, phosphorus and sulfur in metallurgical lime are determined by means of fusion sample preparation-X-ray fluorescent spectrometry. The optimum experimental conditions are determined by analyzing the influences of such factors as fusing agent, release agent, dilution ratio, melting time and temperature on the determination results. Meanwhile, the calibration curves of each element are drawn with standard samples and self-made standard samples with appropriate contents as well as the correlation coefficients are all over 0.999. The experimental samples are determined with test methods. The results showed that the measured and theoretical values of each element could meet the requirements of tolerances as well as relative standard deviations of each element in precision experiment were all less than 5%, which was with higher accuracy and precision. The operation of loss on ignition is not needed for preparing fusion samples in this method so that the experimental processes are greatly simplified and work efficiency is effectively improved, which is with certain promotional and application values.

In this paper, the effects of replacing iron ore concentrate of Inner Mongolia Autonomous Region with finely ground super special powder on production process and properties of pellet are systematically investigated based on the configuration of raw materials of producing acid pellet with the process of traveling grate-rotary kiln-rotating annular cooler of Baotou Steel. Meanwhile, the maximum proportion of Barun concentrate in producing pellet is explored based on the characteristics of low sulfur for finely ground super special powder. The results showed that the proportion of bentonite could be reduced obviously by adding the finely ground super special powder into pellet of Baotou Steel. When the proportion of finely ground super special powder is 10%, proportion of bentonite could be reduced from 2.0% to 1.2%, which is a significant reduction. When the proportion of finely ground super special powder is 5%~20%, performance indexes of green pellets and dry pellets could all meet production requirements of pellets. Under the condition of calcination temperature of 1 220~1 240 ℃, the compressive strengths of finished product, oxidized pellets prepared with different proportions of finely ground super special powder all reach over 2 500 N and reduction swelling rate is lower than 20%, which could meet the requirements of blast furnace production. It is suggested to produce pellets with the configuration of iron charge of 10% finely ground super special powder+50%~60% Barun concentrate+30%~40% iron ore concentrate of Inner Mongolia Autonomous Region for the process of traveling grate-rotary kiln-rotating annular cooler considering the grade of pellets and content of Al₂O₃. Under the raw material condition of 10% finely ground super special powder and 1.2% bentonite, the maximum proportion of Barun concentrate could reach 60%.

The drawing speed of welding wire is seriously affected and fracture of welding wire is easy to happen due to high nitrogen content of the ER70S-6 welding wire steel so that user requirements cannot be met. In order to reduce the nitrogen content in steel, the technological process of converter steelmaking is studied systematically as well as the factors influencing nitrogen content in steel and control measures are discussed. In the paper, the dissolution mechanisms of nitrogen in steel are analyzed by thermodynamics, restricted links of nitrogen removal are analyzed and studied by dynamics as well as the influences of sulfur content in molten iron in furnace, slag charge in top of converter, times of spot blowing for converter and maintenance of tap hole of converter on nitrogen content and corresponding measures for controlling nitrogen content in the technological process of steelmaking are studied based on the thermodynamic analysis and dynamic mechanical analysis.

In the paper, the effects of adding dolomite, soft burnt dolomite and serpentine into infrared micro sintering furnace with different content levels of MgO on such properties as the fluidity of liquid phase and strength of bonding phase for iron ore powder are studied. The results showed that the sintering properties of adding soft burnt dolomite were superior to those of adding dolomite and serpentine, which mainly manifested in suitable fluidity index of liquid phase for iron ore powder within 0.6~1.2 at 1 280 ℃, the highest strength of bonding phase was 476.6 N and appropriate content of MgO was 2.0%. The sinter pot test results showed that the sinter added with soft burnt dolomite was with such advantages as high low temperature reduction degradation index, narrow drippage interval and small maximum pressure differences. The sintering of adding soft burnt dolomite is considered to be more beneficial to improving metallurgical properties of sinter based on the comprehensive comparisons of sintering properties of such three magnesium fluxes as the dolomite, soft burnt dolomite and serpentine.

During the process of manufacturing automobile rims by purchased 420CL steel of one wheel plant in the winter, there is welding deformation cracking at edge of the rims with remained “rolled round edge” of steel coils. The metallographic structure and microhardness of edges with and without cracking of rim are detected with metalloscope and microhardness tester respectively as well as the causes of cracking are analyzed. The values of microhardness of weld seam, coarse grain heat affected zone, fine grain heat affected zone and parent metal at edge of the rims with remained “rolled round edge” of steel coils are 217, 215, 223 and 150 respectively, while those without “rolled round edge” of steel coils are 222, 230, 235 and 220 respectively. The difference of microhardness for welding heat affected zone and parent metal at edge of the rim with cracking is about 70, this is the main cause for cracking of rim. After flash butt welding, the difference of material hardness for welding fine grain heat affected zone and without welding heat effect along edge of rim is too large so that the deformation coordination ability at edge of rim is destroyed and the stress concentration is generated at juncture to cause cracking.

The continuous cooling transformation (CCT) curves of Q1100D steel in cooling process are obtained through the thermal simulation of welding process with Gleeble-3800 testing machine. The microstructure and properties of welded joints under different heat inputs are tested with such methods as the Y-slit welding cold crack test, metallographic analysis and mechanical performance test. The results showed that the ultra high strength steel Q1100D for lifting arm of heavy machinery of Baotou Steel was with better cold check resistance. It could be welded without preheating at room temperature with the condition of a little heat input; with the condition of greater heat input, cold cracks are not observed on the surface and cross section, which indicates that Q1100D steel plate is with good cold check resistance. The evaluation results of comprehensive mechanical and structure properties of the joint indicate that the Q1100D steel plate with thickness of 14 mm is with optimum mechanical properties (tensile, bending and impact) of welded joint under heat input of 1.05 kJ/mm.

The production rhythm of production line could be significantly improved and energy consumption per ton of steel of production line could be reduced by increasing hot charging and feeding rate of production line. In the paper, the characteristics of production line of hot charging and feeding for continuous casting billet of wide and thick plate of Baotou Steel are introduced. The hot charging and feeding rate of production line of wide and thick plate could be effectively increased through taking such measures as increasing the feedback speed of results for samples of compositions of molten steel in tundish and surface and internal qualities of plate blank as well as controlling hot charge cracks of steel plate.

The timely pipeline dredging for long distance slurry pipeline could effectively ensure the safe operations of high pressure pipeline system. For the long distance high pressure slurry pipeline with the inner diameter of Φ212.75 mm, such 5 positioning tube cleaners of 3 types as the soft tube cleaners of Φ205 mm and Φ209 mm, soft descaling tube cleaners of Φ205 mm and Φ209 mm as well as four cup tube cleaners of Φ212 mm are adopted for descaling inside pipelines. For the slurry pipeline before dredging, the water discharge was 230.45 m³/h and outlet pressure of main pump was 1 150.7 kPa, while after dredging, the water discharge was 303.13 m³/h and outlet pressure of main pump was 1 115.2 kPa under the same condition of transporting slurry so that the flow of pipeline is increased by 31.54% and outlet pressure of main pump is reduced by 3.09%. The transportation capacity of pipeline could be effectively improved and outlet pressure of main pump could be reduced with the successful applications of dredging for slurry pipeline on site, which could be as important references for descaling long distance slurry pipeline.

In this paper, the causes for higher burnup are obtained by analyzing the management and operations of heating furnace in detail based on the heat transfer of billet in heating furnace aiming at the phenomenon that the burnup per ton of steel of regenerative heating furnace in 1^# production line of Long Products Plant of Baotou Steel is obviously higher. A series of improvement measures and operation optimizations such as refining and strengthening the thermal management of heating furnace as well as improving hot charging rate, reducing heat losses, controlling exhaust gas temperature and reasonably controlling furnace pressure are put forward based on the working principles and operating features of regenerative heating furnace so that the gas consumption is effectively reduced, production costs are saved and certain economic benefits are obtained.