The goal of accurately controlling various components in smelting process of high magnetic induction oriented silicon steel is realized through process optimization of the whole production line in steelmaking area of Rare Earth Steel Plate Co., where the mass fraction of total oxygen in casting blank is controlled at 0.000 4%~0.001 5%; mass fraction of aluminum is controlled at 0.027 0%~0.030 0%; mass fraction of nitrogen is controlled at 0.007 1%~0.008 3% so that the high magnetic induction oriented silicon steel could meet the needs of next step in the rolling process. As a result, its mass production is realized.

The manganese content of molten iron in the production line of steelmaking in Rare Earth Steel Plate Co. is higher so that the highly purified armco iron could not be smelted by converter process. In the paper, it is introduced the demanganization process with double slag in LF is developed through simulating the demanganization condition of converter with LF, starting with such three aspects as basicity of slag, demanganization temperature and oxidability of slag as well as taking full advantage of existing equipment conditions of production line. The slag with high oxidation after tapping of molten steel from converter is utilized in LF, the ingredient of LF clinker is reasonably adjusted to produce efficient slag of demanganization and promote the steel slag reaction through argon stirring so as to create good thermodynamic and dynamical conditions for demanganization. According to the requirements of manganese content of products, double slag and single slag processes are applied in operations to realize the stable batch production of armco iron with the manganese content less than 0.03% and 0.02%.

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 circle shear is one of the key equipment in production of cold rolling strip, which is mainly used for cutting to length and trimming of strip. In the paper, the structure and principle of equipment for trimming operation of cold rolling strip is analyzed as well as the relation among use and calibration of shear edge for circle shear, process parameter adjustment and quality of trimming is analyzed and improved by taking the circle shear of cold-rolled steel pickling crew in Inner Mongolia Baotou Steel Rare Earth Steel Plate Co., Ltd. as research object so that the stability of circle shear is improved, probability of trimming defect is reduced and quality of trimming for finished strip steel is improved effectively.

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 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.

There are more factors influencing the performances of ultra low carbon stamping products. In this paper, the influence rule of such parameters as contents of different strengthening elements and annealing temperature as well as levelling process on the performances of stamping products is explored. The results showed that the yield strength of product tended to increase with the increase of contents of carbon, manganese and phosphorus as well as the influence degrees of carbon content on the products with different thicknesses were different; with the increase of annealing temperature, the products mainly underwent such three stages as reverting, recrystallization nucleation and grain growth; tensile strength decreased with the running speed of steel strip in annealing decreased.

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 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 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.