The 310 zed beam is mainly used for manufacturing the automotive frame at the bottom of railway freight car and oil tank truck, so the requirements of its corrosion resistance, strength and surface quality are extremely strict as well as the surface defects could directly affect its service life. Its main surface defects include local dent at shoulder, bracing wire and roll marks. The amount of main defects is significantly decreased by taking such measures as optimizing roll pass design of UR (universal rolling) mill as well as improving guide fittings of BD2 (second breakdown) mill and CCS (compact cartridge stand) mill so that the quality of 310 zed beam is improved, which could meet the development demands of railway heavy haul traffic.

In the paper, such problems as improper shearing parameters adjustment, nonstandard replacement process of shear blades, jam of scrap edge and poor running of belt in the shearing process with circle shear of galvanizing unit in Cold Rolled Rare Earth Steel Plate Plant of Baotou Steel are mainly elaborated, which cause the normal edge trimming of production line to be incapable as required or poor edge trimming so that the improvement of first pass yield and normal delivery within delivery cycle of products with main production line are affected. In order to improve the edge trimming quality of circle shear as well as ensure continuous stable and high production, the experiment is carried out to ensure stable operations and edge trimming quality of shearing process with circle shear.

Belt wrapper is the key equipment for pickling line tandem cold mill of cold rolling mill, its stable operations directly cause successful threading and good coiling quality of strip steel. As the key link in production, the fault of threading with belt wrapper is one of the main causes for shutting down of production line. In the paper, it is deeply analyzed the working principles and fault causes of belt wrapper as well as systematically proposed corresponding troubleshooting procedures and processing schemes based on its principles and common faults, which are aimed at providing effective technical guidance for equipment maintenance and rapid fault diagnosis on site.

In order to expand the product type mix of CSP production line and break the technical bottleneck of producing microalloyed pipeline steel with compact process of strip steel, the industrial trial production is carried out based on Q355B bridge mode with smelting of KR (kambara reactor)-BOF (basic oxygen furnace)-LF (ladle furnace)-CC (continuous casting) and low C-Mn-Nb-Ti microalloying system by taking the pipeline steel L415M as the object in this paper. The results showed that the performances of sample with the specification of 9.75 mm could meet the requirements as well as there was performance fluctuation at head and in the direction of 45° for sample with the specification of 7.75 mm. Due to the limit of equipment conditions, the grain is coarser, strength is lower and yield ratio is higher for the product. The stability of product with thin specification could be improved by optimizing the composition and process, which could provide the technical support for large scale production of pipeline steel with the CSP production line.

A series of low temperature impact tests are required for the welding experiment of BT620QL6 low temperature crack arrest steel plate so that multiple times of preparation and processing for impact samples of test piece for welding are needed. The slotting positions of welded samples cannot be ensured to be precise in welding heat affected zone so that the welding impact test results could be influenced and fluctuations of series of low temperature impact absorbing energy are greater with traditional processing method of impact sample. In the paper, the slotting positions of impact sample notch of welded plate are determined, uniformity and continuity of machining dimension precision for samples in the same group are ensured, sensitivity of welded impact samples on sampling positions is eliminated as well as preparation efficiency of sample for welded plate is improved through improving the processing method of sample for welded plate combining with the standard requirements of test sample for welded plate. The test results showed that the stability of data for impact property of BT620QL6 welded plates was improved with the improved processing method of impact sample.

The hourly output and output per shift of pickling line tandem cold mill are influenced by such factors as varieties, specifications and production transition processes of products as well as the differences are significant. Currently, the evaluation of production efficiency is carried out by adopting the mode of converting into output or coil quantity for most mills, which is with such limitations as single evaluative dimension and insufficient objectivity of results. In the paper, the existing production specifications are divided into 16 class intervals combining with the actual productions of pickling line tandem cold mill and objectives of productions are set based on the characteristics of each class interval aiming at the problem. The quantitative evaluation system of monthly production efficiency and efficiency of each shift or group is established through the two core indicators, hourly coil quantity and rate of reaching the standard. Practices show that the multidimensional production efficiency evaluation could be realized with this system, which could provide the evaluation basis for optimizing production efficiency of shift and group as well as be with value of extensive promotion.

In this paper, the causes of black spot defects on hot-dip galvanized products are mainly studied and corresponding countermeasures are put forward. It is proved that the main causes of macroscopic black spot defects are the impurities on coating surface, i.e. zinc dross defect and exposure of base steel caused by indentation through microscopic analysis and research. The amount of such defects could be effectively controlled by controlling the amount of zinc dross on galvanized plate surface, repairing top roll of cooling tower and wrapping it with cloth.

In this paper, it starts with the microscopic surface topography of roll. The effects and change rules of it on PC value on surface of roll are studied through processing principles and control means of such processes as roll grinding and texturing. The mathematical models of roughness and PC value, texturing times and PC value as well as such parameters as texturing gap, current and PC value are established based on the experimental data of Sarclad electro discharge texturing machine for final forming process to study their influencing rules. Finally, the optimal countermeasures for increasing PC value are selected based on actual industrial productions. After the overall process and parameters are adjusted, the PC value on surface of roll is increased and surface quality of product is improved.

In the paper, the speed increase and strip shape optimization for producing thin strip are systematically studied aiming at such problems as low rolling speed as well as prominent shape defects of single-side wave and composite wave in the production of 0.7~1.0 mm thin strip with UCM(universal crown mill) of 2 030 mm pickling line tandem cold mill in Baotou Steel. The internal relations between speed increase and shape defects of thin strip are revealed by analyzing the characteristics of bending roll control for UCM and establishing mathematical model of roll series-strip steel coupling for strip shape control. The strategy of independent control for single-side bending roll is developed as well as the human-computer interaction interface and compensation handler of roll bending force are designed so that the risk of sudden change of strip shape is reduced by the mechanism of integral constraint. Meanwhile, the staged plan of speed increase is formulated as well as collaborative optimization of tension parameters and cooling regime is carried out. The industrial application results showed that the speed of rolling thin strip was increased by 18%, accuracy of strip shape was controlled at 8 I~20 I and hit rate of strip shape was increased to 98.5% after the optimization so that the problems of off tracking and shut-down in furnace area of subsequent process were completely solved. This study could provide the technical support for efficient and stable productions of thin strip with UCM, which is of great significances for improving the quality of such high-end products as automotive sheets.

In the paper, the effects of composition adjustment on mechanical properties and production costs of steel are systematically studied through optimizing the composition control range of such strengthening elements as Mn, Ti and N as well as adopting staged industrial tests and regulating methods of closed-loop characteristics aiming at such problems as higher strength of raw materials in hot rolling, more roll consumption of pickling line tandem cold mill, easy slipping of rolling mill, large fluctuation of yield strength and higher costs in the production of S350GD+ZAM and S450GD+ZAM Zn-Al-Mg structural steels. The results showed that the mechanical properties of both products could meet standard requirements after optimization, rate of reaching the standard for properties of S350GD+ZAM was increased from 96.4% to 98.7%, allowance of yield strength for S450GD+ZAM was sufficient and its rate of reaching the standard was 98.2%; accumulated cost reduction of them in 2024 was RMB 749,320 Yuan so that production bottleneck was effectively broken as well as cost decreasing and benefit increasing were realized, which could provide reproducible industrial technical path for low-cost and stable productions of structural steel with Zn-Al-Mg coating.