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.

The application of eccentricity control for high precision gauge control of tandem cold mill is analyzed through comparing the conventional and extended modes in automatic gauge control (AGC) system of tandem cold mill. Moreover, such influencing factors of thinning for product thickness as eccentricity control of rolling mill, thickness variation of incoming materials, variation of tension control for rolling mill as well as precision of thickness gauge and tachymeter are analyzed by comparing the production situations of rolling mill with different thickness control modes. As a result, the improvement scheme that rolling gauge of rolling mill compensates control model is proposed to improve the thickness precision of products.

In this paper, it is elaborated the performance characteristics and strengthening mechanism of cold rolled continuous annealed low alloy high strength steel HC500LA for automobile structure as well as the whole production process plan including chemical composition, hot rolling, cold rolling and continuous annealing processes. The production practices and batch trial of automobile manufacturer showed that the HC500LA products of Baotou Steel was with good comprehensive mechanical properties as well as stable and mature production process so that it was with batch supply capacity.

The continuous annealing process of phosphorus high strength IF steel 210P1 is tested. The effects of different continuous annealing temperatures on the microstructure and mechanical properties of cold rolled strip 210P1 are investigated with such analysis methods as optical microscope, scanning electron microscope and universal tensile testing machine. The results showed that the grain size gradually increased, non-recrystallization microstructure transformed to recrystallized microstructure and form of microstructure changed from long strip to equiaxed shape with the increase of annealing temperature. The annealing microstructure of steel 210P1 was all ferrite and there was a small quantity of precipitated phase of TiN at grain boundary. The detrimental phase of FeTiP was not discovered so as to demonstrate the continuous annealing process could not cause the phase of FeTiP to be precipitated. The yield strength and tensile strength tended to decrease, elongation, n value and r value tended to increase as well as r value of steel 210P1 increased obviously especially after the annealing of 780 ℃ with the increase of annealing temperature.

In the paper, it is introduced the more elaborate distinction and logic control of different materials, categories, widths, thicknesses, coiling diameters and surface treatment methods with automatic control system through the accurate calculation of model aiming at the “heart-shaped” collapse of coil with thinner strip steel as well as the causes of collapse core for steel coil are analyzed through the change of interlaminar stress for steel coil. Moreover, the cone gradient of coiling tension is realized step by step with the change of coiling diameter as well as the realization and application of tension control scheme of hard core for preventing collapse core are discussed comprehensively.

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 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 the paper, it is expatiated the characteristics and mechanism of cold rolled phosphorous high-strength steel, analyzed various production difficulties of such processes as cold rolling and pickling combining with the chemical compositions and physical properties as well as summarized the countermeasures for such various processes as welding machine, pickling and rolling mill of producing phosphorous high-strength steel through a large number of production practices and optimization of process parameters so that the production line could be with continuous and stable production.

In the paper, it is mainly introduced how the heating zone, soaking zone, slow cooling section, fast cooling section, over aging section and exit section combine such equipment as gas-fired radiant tube, electric radiant tube, draught fan, thermocouple and infrared thermometer to conduct the temperature control of radiant tube and strip steel so that the heating or cooling temperature of strip steel in annealing furnace desired by process could be reached through this two temperature control modes.

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.