The research on the defect of cold-lap on surface of DC04 cold rolled plate is carried out. The defect parts of the sample taken from defective cold rolled plate are analyzed by the metalloscope, scanning electron microscope and energy spectrometer. The results showed that the defect of cold-lap on surface of cold rolled plate was caused by inclusions containing such elements as C, O, Na, Mg, Al, Si and Ca as well as the inclusions are resulting from the compounds of casting powder in continuous casting process and inclusions in molten steel. The defect of cold-lap can be reduced by improving the cleanliness of molten steel, ensuring good conditions of continuous casting machine and constant casting speed as far as possible as well as reducing level fluctuation of crystallizer.

In the process of flattening and straightening, the iron oxide scale of beam steel is broken, dropped out and pressed into surface of steel coils so that pockmarks of different sizes are formed on surface, which seriously affects the appearance quality of products. In this paper, the relatedness between such process parameters as the inlet temperature of finishing rolling, rolling speed, cooling rate and coiling temperature as well as thickness and structure of iron oxide scale is researched. The results showed that the thickness of iron oxide scale was increased with the increase of inlet temperature of finishing rolling when it was below 980 ℃; the faster the rolling speed, the thinner the iron oxide scale on surface of strip steel. The defect of pockmarks on surface of beam steel is effectively controlled by optimizing the heating schedule, increasing rolling speed as well as optimizing laminar cooling rate and coiling temperature.

According to the characteristics of CSP production line of Baotou Steel, the trial production of 450 MPa grade weather resistant steel strip is carried out through adopting reasonable component design and formulating the process plan from processes of smelting to hot rolling. The good corrosion resistance is obtained with such alloy elements as Cu, Cr and Ni as well as grain refinement and precipitation strengthening are realized through microalloying of Ti and controlled rolling and controlled cooling. The microstructure and mechanical properties of optimized weather resistant steel strip Q450NQR1 are tested and analyzed. The results showed that the microstructure, grain size and mechanical properties of Q450NQR1 steel strip could meet the requirements of standard for railway steel Q450NQR1 as well as relative corrosion rate was 47.4%.

In this paper, the development process of SS105 grade rare earth microalloying seamless tube for drill pipe body resistant to H₂S stress corrosion is introduced. The designs of its chemical composition system and key production process are carried out according to the requirements of technical specification of a company and the API Spec 5DP 2020 Drill Pipe Specification as well as trial production of the product is carried out at the same time. The quality of continuous casting billet as well as chemical compositions, mechanical performances, metallographic structure and non-metallic inclusions of finished product are tested, all the indexes could meet design requirements. The effects of rare earth Ce on resistance to H₂S stress corrosion of SS105 grade seamless tube for drill pipe body are evaluated based on its service environment of the oil and gas drilling environment with high content of H₂S and low temperature. The results showed that the resistance to H₂S stress corrosion of the product was significantly improved after add rare earth into it.

In the article, the influences of changes of vanadium (V) content on microstructure and properties of high carbon steel are studied. The high carbon test steels with different technologies and V contents are tested and analyzed with the tensile test and hardness test as well as observation with metalloscope and scanning electron microscope. The results showed that there were influences of changes of V content on mechanical properties of high carbon steel. All the strength, hardness and ductility of high carbon steel could be slightly decreased with lower V content under conventional process conditions. Moreover, there are influences of heat treatment process on high carbon steel with different V contents. The ductility of low V test steel is better than that of high V test steel as well as the changes of strength and hardness for test steel are smaller through reasonably optimizing heat treatment process. Furthermore, it is found in the study that the influences of moderately reducing V content on microstructure of high carbon steel are smaller so that the changes of mechanical properties associated with microstructure are not obvious.

In the paper, it is introduced the studies on fixed flash welding process of 380HB grade high strength heat treated rare earth rail and normalizing process of joints are carried out with the common fixed flash welder and heat treatment equipment for normalizing of joints at home and abroad. The optimal welding process and heat treatment process of joints are summarized through comparing and analyzing the qualified rate of drop weight tear test, area of grey-spots and Rockwell hardness of longitudinal section for joints with different processes. For the joints of fixed flash welding for obtained 380HB grade high strength heat treated rare earth rail, the mean values of tensile strength R_m, elongation after fracture A and impact energy at room temperature KU₂ are 1 141 MPa, 12.5% and 16.0 J respectively, hardness ratios of joints H_J/H_P is 0.92, H_J1/H_P is 0.84 as well as width of softened zone for joints W≤15 mm so that the mechanical properties and microstructure of joints could all meet the standard requirements. As a result, the problems of lower hardness and drop hammer fracture of flash joint for high strength heat treated rail are solved so that the excellent performance matching of welded joints and rail could be achieved, which could meet the requirements of wear resistance and compliance for heavy-haul railway to joints of high strength heat treated rail.

The rail head of 43 kg/m rail with material of U71Mn after induction hardening by user is cracked during straightening process. The rail is inspected with such methods as the chemical analysis, fractography, metallography detection and scanning electron microscope analysis. The results showed that the chemical composition could meet standard requirements, fracture morphology of fracture origin and microstructure were abnormal, melting holes and oxidation characteristics at grain boundary could be seen locally. The offline quenching induction heating process is judged to be abnormal. Different degrees of overburning and overheating are formed in near surface area at round corner on one side of rail, i.e. oxidation and melting at grain boundary. The abnormal microstructure of coarse cementite+ledeburite is formed after quenching so that the rail is cracked in subsequent straightening process.

With the gradual development of rail transit system, bridges and building engineering to large scale and span, the strength of steel used is required to be continuously improved. As the union piece, working stress of bolt products is obviously improved and its working environment is worse so that the requirements of its strength and corrosion resistance are higher. The corrosion resistance of material is improved by adding elements of Cu and Ni as well as austenite structure of steel is finer by adding such elements of refining grain as V and Nb. As a result, the hardenability of steel is reduced and its good cold heading performance is ensured so that the cold heading steel with high strength and corrosion resistance is successfully researched and developed.

The purpose of testing water pressure of steel pipe is to confirm whether there is any water leakage with authorised pressure so as to ensure its performances to meet user requirements. In order to manage the test data for water pressure of steel pipes more effectively and improve flexibility of reports, the test data sheet for water pressure of steel pipes is established with Access database. The archiving and extraction of test data for water pressure of steel pipes are realized by using codes of WinCC VBScript and adopting mode of instruction programming so that the analytical capability for water pressure of steel pipes is improved. As a result, the archiving management of data is more user-friendly, which wins user’s recognition.

In the paper, the technical progress of ironmaking system of Baotou Steel is summarized and analyzed. It is thought that the technological breakthrough and innovation of beneficiation, sintering and smelting problems for special iron ore of Bayan Obo are fundamental guarantee for achieving the ironmaking production with high efficiency and quality, low consumption, long service life and environmental protection as well as technical support of great-leap-forward development for ironmaking of Baotou Steel.