Such elements that could refine grain as V, Nb, Ti, Al and rare earth (RE) are added into the medium carbon steel as well as the stable compound formed by N, C and elements that could refine grain is used to refine the austenite grain and increase the strength and toughness of non-quenched and tempered steel. The stable compound formed by N, C, V, Nb, Ti and Al are observed with metallographic microscope and transmission electron microscope so that the non-quenched and tempered ferrite-pearlite steel is successfully developed. Its yield strength is greater than 550 MPa, tensile strength is greater than 780 MPa, hardness (HB) is not less than 210, elongation is greater than 18%, reduction of area is greater than 45% and impact value of V-notch at room temperature is greater than 50 J. Compared with common non-quenched and tempered steel, the non-quenched and tempered steel F28MnSiVTiRE is with such advantages as high strength and toughness and free cutting so that it could be used for machining such components as vehicle crankshaft and engine connecting rod.

In this paper, it is introduced the CCT curve of 700 MPa grade high strength steel is measured with the Formastor-F full automatic phase change instrument and its microstructures at various cooling rates of 0.5~118 ℃/s are analyzed. The results showed that the transformation product was ferrite and pearlite when the cooling rate of test steel was 0.5 ℃/s; bainite structure began to form when the cooling rate was more than 1 ℃/s; bainite structure began to increase and perlite structure began to reduce with the cooling rate gradually increased; pearlite structure disappeared as well as the structure was ferrite and bainite when the cooling rate was 10 ℃/s; transformation products were mainly bainite when the cooling rate increased to 118 ℃/s. The analysis on the CCT curve and microstructure of 700 MPa grade high strength steel provide the theoretical basis for formulating heat treatment technology in actual production processes.

The aluminum is often used as the deoxidizer in production process of slab. In the theoretical thermodynamic calculation, the amount of aluminum deoxidizer could keep dynamic equilibrium of aluminum and oxygen in liquid steel within limits. If beyond the limit, the surplus aluminum forms non-metallic inclusions so that the cleanness of molten steel is deteriorated and the performances of steel are affected. In the paper, it is analyzed and studied the changes of amount and size for inclusions with different amounts of deoxidizer in converter through industrial tests by taking the L415M steel as an example, elaborated the effects of reducing the amount of deoxidizer on inclusions in the whole production process of high grade pipeline steel. The ratio of inclusions (Class B) less than grade 2 in rolled products is increased from 96.8% to 99.83% by proposing the optimization scheme for controlling the cleanness of molten steel.

Tower crane is the mechanical equipment playing a leading role in the construction of high rise buildings as well as it is widely used because it could achieve any work height and work range through installing and attaching. Its installation and disassembly are more dangerous projects, so construction organizations should pay high attention to the safety technology management of installing and disassembling tower crane. In the paper, it is introduced the construction process of demolition with tower crane, mainly discussed the problems need to be solved in the process as well as elaborated the construction preparation, order of demolition with tower crane, safety precautions and reinforcement measures of truck crane at different positions of roof for underground garage in detail, which could be as the reference for construction of demolition with tower crane.

The effect of residual stress for rail on its fatigue performance is great. In this paper, the influences of different residual stress values on fatigue crack growth rate for U75V heat-treated rail are studied with tempering test and metallographic analysis method. The influences of different tempering times on the residual tension of rail are analyzed with the tempering test. It is concluded that the residual stress gradually decreases with increase of tempering time; the crack growth path at tip of fatigue crack is analyzed by testing the metallographic structure of rail treated with tempering process and observing the metallographic structure of rail with different tempering times, the influences of different tempering times on fatigue crack growth rate are analyzed according to the mode and length of crack growth; the residual stress and fatigue crack growth rate of rail can be effectively reduced so that the anti-fatigue performance of rail can be improved through tempering process control.

In order to improve product quality and strengthen quality monitoring of high speed rail, the chemical composition of U71Mn rail is optimized, Mn content in steel is reduced and rolling process is controlled as well as the trial productions are carried out for such whole series of sections as 60 N, 60 kg/m, 50 kg/m, QU120, QU100 and QU80 of U71Mn. The results showed that the tensile strength was reduced by 7.2 MPa and mean value reached 950 MPa, tread hardness (HB) was reduced by 2.8 and mean value reached 269.2 as well as elongation is basically unchanged by comparing the performances of U71Mn rail with those before optimization. Moreover, the ideal perlite structure is obtained, performances of rail could all meet the standard requirements and is with enough margin so that the effects are better.

The basic pellet with limestone and low reduction expansion rate added 75% Bayan Obo iron concentrate is researched and developed aiming at the special nature of Bayan Obo iron concentrate. It is suggested that the proportion of bentonite is 1.5%~1.8%, alkalinity is 1.15±0.05 and proportion of limestone is 3.5%~3.8% for producing basic pellet with the process of chain grate machine-rotary kiln-ring cooler of Baotou Steel as well as explored the basic pellet is with such process system as good compressive strength, mineral composition and metallurgical properties, which could provide the technical supports for producing it with chain grate machine-rotary kiln-ring cooler of Baotou Steel.

Based on the investigation of technical requirements and production process for like products of pressure vessel steel, the chemical composition design, rolling and research of normalizing process for Q370R are carried out as well as the effects of normalizing temperature on the microstructure and properties of test steel are studied. After normalizing, the strength of steel plate added microalloying elements Nb, V and Ti is decreased, elongation and impact energy are increased significantly. With the increase of normalizing temperature, strength of test steel is decreased gradually. The strengths of steel plate with rolled state and the same normalizing process added a small amount of Cr are both higher than those of the steel plate without Cr, while the elongation and impact energy are lower than those of the steel plate without Cr. The cost of per ton of steel will be increased by adding a small amount of Cr. After normalizing, the microstructure is fine grained ferrite and pearlite. Based on the comprehensive consideration, test steel with the composition system of adding microalloying elements Nb, V and Ti as well as the properties of steel plate with controlled rolling and normalizing at 840~880 ℃ could meet the standard requirements.

The accuracy of performance characterization for material has crucial influences on the numerical simulation results. In the software CAE, it generally contains the material cards of European mainstream material suppliers and a small number of domestic manufacturers, but due to different material characteristics of each manufacturer, the corresponding material card of material with the same grade shows different data distribution law as well as the criterion of yield and hardening. Thus, it is an indispensable link in such product applications as evaluation of stamping process as well as design and manufacture of mould to accurately characterize the characteristics of their own products and establish own material cards for material manufacturers. In the paper, the test scheme suitable for presenting cold stamping performance is established and data processing method is studied by taking the typical grade DC04 for cold stamping steel as the objective. Finally, the material data card for stamping simulation analysis which could accurately characterize product characteristics of Baotou Steel is developed. After adjust the working condition of stamping based on the calculation guidance of material data card, the stamping process suitable for performance characteristics of sheet matal of Baotou Steel is obtained to ensure the accuracy of simulation technology support and accurately improve the applicability of product.

In the process of rolling wire rods with Φ5.5 mm and Φ6.5 mm in Long Products Plant, the accident of piling-up of steel is easily to happen at the water cooling section after finishing rolling so that the rhythm of production and output are affected. Its true causes are found out through analyzing its phenomena, morphology and microstructure of its samples with the scanning electron microscope so that the probability of repetitive accidents and its times of piling-up of steel at water cooling section after finishing rolling are reduced. After the rectify and reform, the ratio of piling-up of steel is reduced to 0.013%, cumulative failure time is reduced to 35.8 hours and rejection rate is reduced to 0.027%.