In this paper, the microstructure and properties of 700 MPa grade beam steel with such two composition designs as low C+Mn+Ti and low C+Mn+Ti+Nb are compared and analyzed. The results showed that the plasticity of single Ti microalloyed product and that of Nb-Ti multi-microalloyed product were the same with the same strength, but the low temperature impact toughness of single Ti microalloyed product was poorer so that its brittle transition was at -20 ℃, while the brittle transition of Nb-Ti multi-microalloyed product was at -50 ℃. It could be improved through increasing the rolling reduction of the first pass of rough rolling and thickness of intermediate billet so as to reach the control level of Nb-Ti multi-microalloyed products.

With the increase of task load for 2 250 mm hot rolling production line in Inner Mongolia Baotou Steel Rare Earth Steel Plate Co., Ltd., the effect of rolling rhythm on production increase is very important so that the causes influencing rolling rhythm are emphatically analyzed. The rolling rhythm is improved, gap time of rolling is shortened and average hourly output increases by 2.3 pieces through unscrambling and optimizing the factors restricting rolling rhythm in finishing area of 2 250 mm hot rolling production line so that its capacity exceeds the design target of 5.5 million tons per year.

The hot-dip galvanized extra deep drawing steel for back panel of TV with good surface quality, stamping formability, mechanical properties and paint coating property is successfully developed through scientific composition design as well as reasonable smelting, hot rolling, pickling and hot-dip galvanizing process control. Its formability, corrosion resistance, performance stability and higher level of surface quality control could all satisfy users’ requirements.

In the paper, it is elaborated such faults and problems of axial plunger pump with the existing working condition of hydraulic system in Inner Mongolia Baotou Steel Rare Earth Steel Plate Co., Ltd. as overheating of pump body, sealing failure, system pollution, noises and insufficient flow caused by damage of parts, oil pollution, leakage, friction losses and assembly accuracy. Moreover, their inducements and characteristics are analyzed aiming at the generation of faults as well as damage and operation condition of inner components, quality and cleanliness of oil, system leakage and temperature are checked so as to make effective fault diagnosis for hydraulic system as well as ensure the stable operations of axial plunger pump and hydraulic system.

In this paper, the control strategy of U shaped cooling is researched and developed through controlling coiling temperatures at head and tail of hot rolling aiming at the problems that the fluctuation and differences of mechanical properties along the length direction of steel belt are too great caused by uneven heat dissipation of hot rolling process after coiling for deep drawing series products. As a result, the flexible setup of steel belt with different steel grades and thicknesses could be realized so that the mechanical properties along the length direction of cold rolled products are even and the drawability of products is guaranteed.

The surface quality, rimhole, center porosity, center segregation, contents of oxygen and nitrogen and inclusions for the head slab of IF steel produced by a steel mill are studied as well as the rolling defects of head slab are tracked and with the treatment of peeling with flame. The study results showed that the surface quality and rimhole of head slab were improved with the increase of slab length; level of center porosity for internal soundness exceeded the standard at slab length of 1 m, while there was no abnormality seen for center segregation; contents of oxygen and nitrogen tended to decrease with the increase of slab length; number of such inclusions as Al₂O₃, TiN and complex inclusion of Al₂O₃-TiN decreased with the increase of slab length; there was large complex inclusion of Al₂O₃-MgO-CaO at 1 m of head slab; main rolling defects of head slab were such subcutaneous inclusion defects as deoxidation product of Al₂O₃ and slag entrapment of mould level fluctuation; quality of head slab could be effectively improved with the treatment of peeling with flame.

The process design and industrial trial production are carried out based on the technical requirements of 880 MPa, 930 MPa and 980 MPa packaging steel strip as well as the technological processes of conventional 2 250 mm hot continuous rolling production line and 2 030 mm production line with pickling line tandem cold rolling mill in Inner Mongolia Baotou Steel Rare Earth Steel Plate Co., Ltd. and blue annealing production line of customer. The test steel with such composition combination as medium carbon, low silicon and manganese is smelted with such technologies as KR desulfuration and calcium treatment. The mechanical properties of hot rolling, pickling and blue annealing for test steel are analyzed as well as the trial production process satisfying different strength levels of packaging steel is determined. It is found that the pearlite is basically eliminated and the microstructure of ferrite and bainite is formed with the coiling temperature of 500 ℃ so that the strength and elongation of finished product could be improved by comparing the microstructure and properties of hot rolling and performances of steel strip with blue annealing of 600 ℃ and 500 ℃ coiling temperatures. 3 strength levels of packaging steel are successfully developed through trial productions so that the production process is trouble-free as well as the stable production and batch applications are realized.

In this paper, the effects of Nb with different contents on the microstructure and properties of high strength steel are discussed by taking the hot rolled coils with 650 MPa grade structural steel as research object. The data showed that the yield strength of high strength structural steel reduced by about 15 MPa, tensile strength reduced by about 25 MPa and elongation rate increased by about 1 percentage point with reducing content of Nb by 0.010%. It is found that the fine oval precipitates are rich in Nb and square precipitates are rich in Ti in the high strength steel containing niobium and titanium by comparing the microstructures with transmission electron microscope.

The sink roll mark defect of thick gauge hot-dipped galvanization products is always the bottleneck problem of hot-dip galvanizing line of Baotou Steel. The slagging composition of sink roll is analyzed with the XRD phase analysis. The main factors influencing the defect are the temperature of liquid, Al content of liquid zinc, cleaning quality of strip steel and tension control of cooling tower after galvanizing. The effective control measures are formulated based on the influence factors so that the defect is relieved or eliminated fundamentally.

In the paper, the process of developing 500 MPa grade low alloy high strength automobile steel is mainly introduced. With the multi-microalloying treatment technology of Nb and Ti combining with controlled rolling and cooling process, the mechanical properties and cold bending property of manufactured pickled automobile structure steel QStE500TM could meet the standard requirements. Its metallographic structure is mainly quasi-polygonal ferrite and pearlite, grain size is uniform and fine, surface quality is good as well as the stable batch production has been realized. As the representative product of pickled automobile steel for Baotou Steel, it is recognized by users.