The effects of solution and aging treatment on microstructure and mechanical properties of 10Ni2Cr2MnCuMoVAl plastic mold steel were experimentally studied. The results show that the dominant microstructure of 10Ni2Cr2MnCuMoVAl steel after solid solution treatment is lath martensite, and higher solution temperature results to larger width of martensite, while the highest value of hardness could be obtained after solution treatment at 890℃. After aging, the microstructure consists of lath martensite, granular bainite and carbides. For steel aged at 460-520℃, the strength of the material gradually increased with higher aging temperature, while the toughness decreased gradually. When the temperature exceeded 520℃, higher temperature led to decreased hardness and increased toughness. Compared the mechanical properties of steel aged at 540℃ for different time, the test steel reached the peak of mechanical properties at 8h. By comparing the mechanical properties of the test steels after different aging treatments, the optimized heat treatment process of 10Ni2Cr2MnCuMoVAl steel is solution treatment at 880℃ for 2h with air cooling and tempering temperature at 540℃ for 4h with air cooling.

Abstract：Nonmetallic inclusion is a key issue of the steelmaking. The control of inclusions in the liquid steel mainly focuses on the inclusion modification, as well as the growth and removal of inclusions in the molten steel. The transformation mechanism of inclusions in solid steels during the heat treatment process is different with that in the liquid steel, including the precipitation of new phase, transformation of inclusions, and crystallization of inclusions. The transformation behaviors of inclusions in various steels were reviewed. The changed equilibrium between the steel matrix and inclusions with temperature was the driving force for the inclusion transformation during the heat treatment process. Inclusions changed from MnO-SiO2 to MnO-Cr2O3 in stainless steels during the heat treatment process, while it transformed from the Al2O3-MgO-CaO to Al2O3-MgO-CaS in Al-killed steels. The composition of SiO2-MnO inclusions changed little, and there was the crystallized SiO2 phase in inclusions.

Abstract： With increase of the pipeline failure cases caused by microbiologically influenced corrosion (MIC), it is of great engineering significance to develop new measures for MIC mitigation. The Cubearing pipeline steel is a novel strategy for MIC mitigation from the material design aspect, which has shown good MIC resistance. Based on the previous reports, this review mainly summarizes the research progresses on phase transformation kinetics, thermoplasticity, and precipitation control of nanosized Curich phase, etc., in order to help better understanding of this novel type of Cubearing MIC resistant pipeline steels, guide the future production practice, and promote the application and development of Cubearing pipeline steels.

Abstract： By the method of quantitative analysis of the microstructure, highresolution transmission electron microscopy and thermodynamical calculation, the effect of adjustment of micro composition and final forging temperature on mechanical properties and microstructure of 38MnVS6 steel was studied. As the results showed, by lowering the content of carbon and adding the content of nitrogen, the strength could be increased while plasticity and toughness could be improved obviously. And the roomtemperature impact energy increased from 52 to 83J. The mechanism was that the drop in carbon content resulted in the increase in volume fraction of ferrite which enhance the toughness; the addition of nitrogen content could increase the precipitation strengthening effect, which made up the strength loss by carbon drop; and with the decrease in final forging temperature, the grainrefined strengthening and toughening effects were improved by the grain refinement of ferrite and the increasing in ferrite percentage. The combination of adjustment of content and final forging temperature made the strength stay at a stable level and the toughness be improved.

Abstract： Forged HPD1 duplex stainless steel specimens were subjected to solution treatment at different temperatures in order to gain fatigue test samples with gradient changes of the ratio of the two phases (α, γ). The influence of phase ratio on fatigue performance and analysis of microstructure were obtained by comparing fatigue fracture times of the corresponding samples tested at room temperature. The results indicate that within the range of the ratio of the two phase, as α/γ ratio increasing, fatigue performance sustainably developed. According to the image of SEM, result of EDS and TEM image and diffraction pattern, plastic deformation mainly occurs in the austenite, and the dislocations are primarily planeslip type, which massively multiply in the austenite and pile up at the phase boundary, but dislocation motion scarcely happens in ferrite. Besides, microcracks nucleate in the austenite region and expand outward along the phase boundary. Under the combined effect of these factors, fatigue fracture finally occurs.

Abstract： Steel industries are always trying to manufacture advanced high strength steel (AHSS) product with higher efficiency and better mechanical properties. Over the past decades, replacing batch annealing by continuous annealing led to much improved production efficiency but not as much in the improvement of mechanical properties. Recently, a novel flash processing (FP), also termed as ultrafast heating (UFH) process, under which steel is heated at a rate over 100℃/s to a peak temperature and instantly cooled, has attracted more attentions due to its unprecedented high efficiency. The FP can significantly shorten the heat treatment duration to avoid grain growth, thus bringing significant strengthening effect without deteriorating ductility and toughness. The mechanical properties of typical AHSS grades subjected to FPs were summarized. The influence of process parameters, including initial microstructure, preheating, heating rate were analyzed. Moreover, the accurate microstructure tailoring via the ultrafast heating to an intercritical temperature was also briefly discussed. Finally, the industrial application of current FP technology was prospected.

Abstract： Safety, environmental protection and energy saving become the development themes of the current automobile manufacturing industry. The car body made of highstrength steel plate can not only effectively reduce the weight and fuel consumption, but also improve the safety and comfort of the car. It is the best way to realize the lightweight of the car body and improve the crash safety at the same time. The present situation and latest achievements of advanced high strength automobile steel such as DP steel, CP steel, Q&P steel, hotstamped steel, medium manganese steel and low density steel with the development trend and technical requirements of automobile body lightweight were introduced. And it also puts forward the introduction and suggestions for the optimization control of different kinds of advanced highstrength automotive steels. The related research results have certain guiding significance for the research and development and production of high performance automobile steel, and provides beneficial reference for the design, development and application of advanced high strength automobile steel with higher strength, higher plasticity and excellent service performance.

Abstract：The recent developments of V microalloying technology and its applications in HSLA steels were reviewed. EnhancedN in V microalloyed steels promote precipitation of fine V(C,N) particles, and improves markedly precipitation strengthening effectiveness of vanadium. VN process can be used effectively to refine ferrite grain size by the nucleation of intragranular ferrite promoted by V(C,N) precipitates in austenite. The latest research results show the potential benefits of V microalloying technology to advanced high strength steels (AHSS) for the automotive sector including DP steels, bainitic steel, TRIP steels and TWIP steels, etc. The wide applications of VN process in high strength rebars, section steels, forging steels and thin slab direct rolling strips, etc., had greatly promoted the rapid development of V microalloyed steels in China.

Abstract： Isothermal spheroidization annealing treatment is a vital step for bearing steels to transform the lamellar pearlite into granular pearlite, which can improve the uniformity and cutability of bearings. The effect of isothermal spheroidization annealing on the microstructure and hardness of a lowdensity bearing steel with 5 wt.% addition was studied. The result shows that, Al addition has a great effect on increasing annealing temperature and shortening holding time of spheroidization annealing and decreasing the hardness of pearlite lower than 300HV. However, there is graphitization during the isothermal annealing process, graphite particles decrease the carbon content in steel matrix and has a great contribution to decrease hardness. However, graphite particles cannot be completely dissolved into steel matrix during the final austenitization treatment, the undissolved graphite particles have a deterioration effect on the uniformity of microstructure and decrease the final hardness. Considering the uniformity of structure and mechanical properties, the isothermal spheroidising annealing treatment should not be chosen for spheroidizing the lowdensity high Al addition bearing steels.

Abstract：The mechanical properties of forged 0.15C5Mn steel and 0.15C5Mn2Al steel at room temperature and 750℃ under quasistatic tensile conditions were compared. The microstructures were characterized by scanning electron microscopy and electron backscattered diffraction. The results show that the addition of Al causes a difference in the microstructure at room temperature. There is a small amount of ferrite in the structure of aluminumcontaining steel at room temperature,which results in low strength of aluminumcontaining steel. An elongation of 90.5% and 101% was obtained in forged 0.15C5Mn steel and 0.15C5Mn2Al steel at 750℃,respectively. After 750℃ tensile deformation,the 0.15C5Mn steel obtained a martensitic structure. The addition of the Al element expanded the dual phase region and made the 0.15C5Mn2Al steel have tensile deformation in the dual phase zone,which results in the dual phase structure of ferrite + martensite. The deformation in the dual phase zone makes the 0.15C5Mn2Al steel have a higher elongation and lower tensile strength.

Abstract：The effect of tempering temperature on the microstructure evolution and hardness of Ti-V-Mo complex microalloyed steel was studied by means of OM, SEM, EBSD, TEM and Vickers hardness tester. The precipitation law of (Ti, V, Mo)C at different tempering temperatures and the mechanism of its effect on hardness were explained. The results show that the hardness of (Ti, V, Mo)C increases linearly when tempering temperature is 450~600℃. Maximum hardness can reach 450HV when tempering temperature is 600℃. When the tempering temperature at 650℃, the hardness decreases slightly. Meanwhile the average grain size of martensite lath block in Ti-V-Mo complex microalloyed steel increases from 7.3 to 9.9μm. The amount of (Ti, V, Mo)C increases monotonously, while the average size of precipitated phase particles at 600℃ is 5 nm, and (Ti, V, Mo)C particles below 10nm can be as high as 90%. The theoretical calculated precipitation strengthening increment leads hardness to increase by 90.7HV, which was much higher than the hardness loss caused by the softening of the matrix. Thus, the main factor to the increase in hardness of Ti-V-Mo complex microalloyed steel is refinement mean size of (Ti, V, Mo)C particles. Tempered at 600~650℃, the distribution ratio of grain boundaries is basically the same, the average size of martensite laths changes slightly, but the average size of precipitated is increased from 5 to 5.6 nm, and the proportion of (Ti, V, Mo)C particles less than 5 nm gradually decreases, resulting in a decrease in hardness.

Abstract： Niobium is an important microalloying element in modern highperformance steels. It has a strong segregation characteristic at the grain boundaries. In this work, three kinds of Nbvacancy complex diffusion coefficients were tested by using nonequilibrium grain boundary segregation kinetic model. According to EPMA measurement results of niobium segregation kinetics at the grain boundary in FeNb binary alloy, the final Nbvacancy complex diffusion coefficient was selected. The effects of lower isothermal temperature, matrix niobium content and prior austenite grain size on nonequilibrium grain boundary segregation kinetics were discussed accordingly. The results show that the diffusion coefficient of the niobiumvacancy complex is found. At an isothermal temperature of 1000℃, the critical time for the nonequilibrium grain boundary segregation of niobium is about 15min, and the critical time constant is 6.57×105. When isothermal temperature increases, the critical time decreases rapidly and the maximum segregation amount of Nb at the grain boundary decreases gradually. The maximum segregation of niobium at grain boundary increases linearly with the increasing of matrix niobium content. The critical time increases gradually with the prior austenite grain size increasing.

Abstract：The behavior of austenite grain growth process and grain size distribution of copperbearing low alloy strengthening steel were investigated at different heating temperatures and holding time using the confocal laser scanning microscopy. The results demonstrate that as the heating temperature increases, the austenite grain size gradually increases, and in different temperature ranges, the austenite grains have different growth rates. As the holding time increases, the austenite grains gradually grow, but the higher the heating temperature, the faster the austenite grains grow. The distributions of austenite grain size under different heating temperatures and holding time all exhibit a typical logarithmic normal distribution, whose average peak abscissa and frequency varies with heating temperature or holding time. On the basis of experimental data, a kinetic model for austenite grain growth of the tested steel is established using regression analysis. The results predicted from the kinetic model are in good agreement with the experimental ones, and the average relative errors between them are less than 5%. Therefore, it can be concluded that the established kinetic model has high accuracy and reliability to predict the austenite grain growth of the tested steel.

Abstract：The effects of 0.065 wt.% N element addition on microstructures, mechanical properties and corrosion properties of the Cr13 super martensitic stainless steel have been investigated by microstructural observation, SEM, tensile tests and electrochemical tests, in order to improve the properties of super martensitic stainless steel to meet the requirements of oil and gas exploitation. Experimental results indicated that the addition of N element significantly reduced the content of ferrite as well as increased the content of austenite. Meanwhile, proper addition of N element has obvious impact on refining the original austenite grain and shortening the tempered martensite, which can effectively improve the yield strength and tensile strength of tested steel due to the increase in grain boundaries and subgrain boundaries. As for the corrosion resistance, it was revealed from electrochemical experiments that proper amount of N element can enhance the protection and repassivation performance of passivation film, which consequently improved the corrosion resistance of test steel to a certain extent.

Abstract：According to the actual coldcoiling process of ultrahigh strength spring steel, 60Si2CrVAT, the microstructure and the mechanical properties of the tested steel after Quenching&Tempering (Q&T) and QuenchingIsthothermalQuenchingTempering (Q-I-Q-T) heat treatment processes were studied by quasistatic tensile experiments and different microcharacterization methods. Then the Deform3D finite element numerical simulation software was used to simulate the variation characteristics of the field parameters such as the stress and the strain during coldcoiling process under two process parameters, and to predict the fracture damage probability during the process. Results of tensile test show that under the same strength conditions, the plasticity of the Q-I-Q-T treated spring steel with multiphase microstructure is better than that of the Q&T treated spring steel with medium temperature tempered martensite in which percentage reduction of area and the elongation increase 65% and 66% respectively. Results of simulation show that the change law of the equivalent stress and the equivalent strain is similar for the tested steel with two different microstructures during cold coiling process, but the Q-I-Q-T treated spring steel has lower values of the equivalent stress and the equivalent strain during the process, and has lower probability of breakage.

Abstract： Taking the 800MPa grade quenched and tempered hydroelectric steel as the research object, the essential reason for the difference of low temperature toughness in different sampling positions along the thickness direction was studied by using the visualization quantitative method of microstructure, by scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and impact test. The results show that transition from surface to center in the direction of ultrahigh strength steel plate thickness, the microstructure changes from lath bainite to granular bainite, the low temperature toughness decreases and the ductile brittle transition temperature (DBTT) increases. With the transition of microstructure from the surface to the center (i.e., cooling rate decreases), the variant selection is strengthened, and the transformed microstructure dominated by single Bain group is formed in the center. The density of high angle grain boundary is significantly reduced, and the increase of DBTT is closely related to the density decrease of block boundaries. In addition, the study found that the block boundaries within austenite grain and prior austenite grain boundary can effectively deflect and prevent crack propagation. However, because the density of austenite grain boundary is significantly lower than that of block boundaries, the contribution to crack propagation resistance in the process of impact test mainly comes from the block boundaries.

Abstract：Taking cold-rolled annealed sheet DP980 as the research object and combining with the process parameters in the production process, the microstructure, hardness, strength and elongation of hotrolled coil, coldrolled coil and annealed coil samples were analyzed by means of optical microscope, scanning electron microscope, microhardness tester and room temperature tensile testing machine. The results show that the coiling speed is reduced to control the stability of strip coiling during the hot rolling process, which results in lower strip coiling temperature and uneven mechanical properties, and thus produces thickness fluctuation in cold rolling process. At present, to solve this problem, cutting the head and tail ends was carried out in each procedure of cold rolling, which also led to the low yield of DP steel.

Abstract： The lowcarbon bainite steel 07MnCrMoVR for hydropower stations was rolled with different widespread ratios, the microstructure and mechanical properties of the test steels before and after tempering were observed and tested, respectively. And the carbide precipitation behavior during tempering was analyzed by EDS. The result show that the single pass reduction rate and deformation zone coefficient of roughing rolling stage can be improved by adopt smaller widespread ratio, the fine granular bainite microstructure can be obtained after rolling by broken austenite recrystallization grains effectively at longitudinal rolling stage. After tempering at high temperature of test steels, a large number of cementite and alloy carbide are dispersed uniformly on the matrix of bainite ferrite. With the increase of tempering temperature, the strength of the test steels increases first and then decreases, the elongation and low temperature impact toughness continue to increase.

Abstract： Ferrite is one of the main structure types of pipeline steel used in acidic environment, the relationship between grain boundary structure of ferrite and hydrogeninduced cracking (HIC) susceptibility of pipeline steel was explored, which can provide guidance for further optimizing the HIC resistance of pipeline steel. The hotrolled pipeline steel was heattreated in different processes. Scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM) were used to observe the grain boundary, dislocation structure, hydrogen bubbling, and hydrogeninduced crack morphology of the sample. The HIC susceptibility and hydrogeninduced ductility loss of the samples were measured by electrochemical hydrogen charging and dynamic hydrogen charging methods. The hydrogen trapping efficiency and hydrogen distribution of the samples were observed and analyzed by electrochemical hydrogen permeation test and silver decoration technique, and the relationship between grain boundary structure of ferrite and HIC susceptibility was explored. The results show that when the material is dominated by lowangle grain boundaries or the ratio of high and lowangle grain boundaries is about 1∶1, its trapping efficiency for hydrogen atoms and HIC susceptibility is high; both high and lowgrain boundaries can trap hydrogen atoms, but the mechanism of action on hydrogen atoms is different. Highangle grain boundaries mainly promote hydrogeninduced crack initiation, while lowangle grain boundaries mainly promote hydrogeninduced crack propagation.

Abstract： The shock tunnel worked in an ultrahigh pressure hydrogen environment and faced serious risk of hydrogen damage, which put forward strict requirements for hydrogenexposed materials. At present, conventional hydrogenresistant steels might be difficult to meet the equipment requirements. Therefore, in order to ensure the safe operation of equipment in the ultrahigh pressure hydrogen environment, it was of great significance to study the hydrogen damage of steels used in the ultrahigh pressure environment. Based on the research results at home and abroad, the hydrogen damage mechanism and its influencing factors were briefly introduced, then the hydrogen resistance and development status of Cr-Mo steel, singlephase austenitic stainless steel, precipitationstrengthened austenitic alloy and nickelbased alloy was summarized. Finally, the future research focus was prospected.

Abstract：With the acceleration of global industrialization, the emission of carbon dioxide has been increasing year by year, bringing more and more extreme weather and environmental disasters. CO2 storage technology is currently recognized as a backup technology for achieving carbon neutrality. The development status and future trends of CO2 mineralization technology using steel metallurgical solid waste as feedstock were reviewed. Firstly, the pathways and principles of CO2 mineralization were introduced. The process conditions for direct mineralization are relatively strict, and the solidification of CO2 will consume a large amount of resources. However, the reaction conditions for indirect mineralization are more gentle and the effect is more significant. Then, the most representative and feasible technologies for solid waste mineralization in steel metallurgy were summarized, among which the process route using NH4Cl as a leaching agent exhibits the best industrial potential due to its dual advantages of solvent recycling and mild reaction conditions. In addition, based on the economic analysis of typical pilot experiments, raw material resources and other factors are not the main constraints on the industrialization of CO2 mineralization technology. The key to achieving industrialization is the scaleup test of CO2 mineralization process, the development of recyclable leaching solution, and the establishment of an economic evaluation system.

The wavelet analysis method was wildly used in different areas to deal with datum of figure, and can be also applied to minerals phases of iron ore. In order to distinguish inclusions, the non-ferrous minerals or metallurgic wastes, some inspection companies used the method of phase analysis. The method of characteristic information picking up for different minerals phases′ structure of iron ores was introduced on basis of wavelet analysis in Matlab. The quantitative analysis was realized about approximate volume of mineral. The different phases in different phase diagrams can be indexed through analyzing and sorting the information of characters.

The room-temperature fretting wear behavior of chromium carbide/Ni3Al composite and conventional high temperature wear-resistant materials such as Stellite 6 alloy and T800 alloy was investigated comparatively. Compared with Stellite 6 alloy and T800 alloy, chromium carbide/Ni3Al composite possessed higher fretting wear resistance. The fretting wear resistance of chromium carbide/Ni3Al composite was respectively 55 times and 26 times of that of Stellite 6 alloy and T800 alloy. The good wear resistance of chromium carbide/Ni3Al composite can be attributed to good abrasive wear resistance, the reasonable size distribution of reinforcements, and good mechanical properties of Ni3Al matrix.

The thermodynamic behavior of Ce and its compounds in molten steel was summarized, and the types of stable compounds after Ce added to molten steel and its variation were predicted. The mechanisms and rules of Ce compounds and dissolves Ce refining solidification structure of as- cast steel were summarized respectively. The improvement of homogenous by Ce was analyzed and the reason of decrease of element segregation was summarized. At last, some problems were pointed out which had not been solved in the research of rare earth Ce to improve the microstructure and homogeneity of steel, and put forward the main directions of the future research in this field.

One- step and two- step isothermal low temperature bainitic transformation were designed. The effects of heat treatments on the microstructures, mechanical properties and stirring wear resistance of low temperature bainite were discussed. The results show that the microstructures of samples under different heat treatments all consist of micro- and nano- scale bainite lath and austenite. The size of bainite lath decreases from 95 nm to 65 nm with the decrease of isothermal temperature from 300℃ to 250℃ under the one- step isothermal bainitic transformation. Moreover, the volume fraction of austenite likewise decreases from 281% to 199%. The unstable block austenite is apparently refined by the two- step isothermal bainitic transformation. The optimal balance between the tensile strength (1857MPa) and elongation (1059%) is obtained in the sample treated by two- step isothermal bainitic transformation. Also, the V- notch impact absorbed energy of the sample treated by two- step isothermal bainitic transformation reaches 11J. Compared with the one- step isothermal bainitic transformation (300, 250℃), the sample treated by two- step isothermal bainitic transformation shows the optimized wear resistance and increases by 118% and 314%, respectively, which is attributed to the better ductility and toughness.

In order to clarify the influencing factors of cold-bonded molding ore/coal composite pellets made by iron ore and coal, orthogonal experiments were done to study the performance of ore/coal composite pellets through adjusting the binding agent content, moisture, pressure, feeding speed, molding speed, baking time and baking temperature. The results show that top three factors are binding agent content, baking time and moisture. A regression equation between that three factors and pellets′ compression strength was present by further experiments. The regression equation can meet experimental results with good effects. The maximum compression strength of ore/coal composite pellets is 25167N during cold-bonded molding experiments.

The distribution characterization of compositions, microstructure and hardness in surfacing fusion zone of X80 pipeline steel was done by laser induced breakdown spectrum original position analyzer, automatic metallographic and micro Vickers hardness instruments. The results show that the content distributions are very different for some elements in the surfacing area. There is a cricoid enrichment zone of Ti in the fusion area of base metal and welding material, and significant change for the content distribution of C is not found. The microstructures in different fusion area are also very different. The grain is fine and there are a lot of strip ferrite and a little pearlite in the matrix organization of pipeline steel. In heat affected zone, recrystallization of the grain occurs and a large number of granular bainites appear. At the junction of weld melted metal, the grains get larger and a lot of lath martensites and bainites come into being. Vickers hardness of base metal is lower than welding material and a cricoid zone with higher Vickers hardness appeared in the fusion area. The micro- hardness distribution has close relationship with the composition distributions of the elements and microstructure distribution in welding area of pipeline steel.

The effect of two smelting processes (process 1: vacuum induction melting + electroslag remelting and process 2：vacuum induction melting + vacuum arc remelting) on the inclusions in C- Cr- Ni- Mo stainless steel ingot and its mechanical properties were comparatively investigated by means of Aspex Explorer, scanning electron microscopy and EDAX spectrometer. The results show that the mass fraction of gas in the steel ingot casted through process 2 is less than 25×10-6 with irregular shaped Al2O3 inclusions. On the other hand, the mass fraction of gas in the steel ingot casted through process 1 is approximate to 100×10-6 with evenly distributed Cr2O3, Al2O3 inclusions in the size around 5μm. It is obvious that the number of oxide inclusions in ingot casted through process 1 is larger than that in ingot casted through process 2, due to the higher mass fraction of oxygen. Meanwhile, the impact toughness and ductility of specimens sampling from ingot casted through process 1 are clearly lower than those sampling from ingot casted through process 2. Thus, the conclusion could be carefully drawn that taking process 2 could significantly contribute to reducing the mass fraction of gas in steel and improving the cleanliness of steel. Therefore, the higher toughness and ductility of the steel could be obtained.

The circumferential flow of hot metal has a significant influence on the hearth erosion. Because the situation of the hearth is “black box”, there is no direct examine method for the hot metal flow. Based on the computational fluid dynamics, the streamline and velocity were studied with different deadman conditions and different tapholes. The results show that when the hot metal tap with single or double tapholes (with the angle of 40°) and the deadman is at the sitting condition whose center is fine coke, the circulating hot metal is the most serious in the hearth. When the hot metal tap with double tapholes(with the obtuse angle), the circumferential flow of hot metal is weakened. The sitting deadman could strengthen the hot metal circulution. However, the floating deadman could weaken hot metal circulution, but it strengthens the hot metal flow of the bottom.

To investigate the corrosion performance of commercial automotive cold rolling sheets under severe atmospheric environment, electrochemical impedance spectroscopy was used to detect the electrochemical behaviors of three types of cold rolling sheets and a humid- temper test was carried out to explore the corrosion behavior under shipping and storage environments. Meanwhile, the effects of surface status and micro- structure of the sheets on the corrosion behaviors were analyzed based upon the results of profile measurements, contact angle tests and metallographic analysis.The results show that with the same load of anti- rust oil, 590DP steel presents the largest electric resistance of oil film and charge transfer resistance, and the longest incubation period of rust under storage environment. All these good properties could be assigned to the surface profile of the steel. However, the generation rate rust turns to be faster later on, which can be attributed to its dual- phase microstructure. In sum, the surface wetting status of different types of sheets are almost the same, which has no significant effect on the corrosion performance of the steels. Comparatively, surface profile of the steels plays an important role during the initial stage of corrosion, and the difference in microstructure has a more remarkable influence on the development stage of corrosion.

A statistic method, statistics of extreme values (SEV), was described in detail, which could evaluate the inclusion level of steel. Some BOF- CC(billet) made ultra- low oxygen (［O］ mass fraction of 5×10-6)GCr15 bearing steels were evaluated by this method. 16 standard inspection areas were chosen in each inspected steel (60mm and 30mm round bar), and the standard inspection area was 280mm2. It has a 999% probability of the characteristic size of maximum inclusion in the inspected 60mm and 30mm round bar being respectively no larger than 2577μm and 2408μm. The effectiveness of the SEV method was analyzed by comparing the experimental results. For the steels with the same quality and made by the same plant, the evaluation results are basically consistent, thus the SEV method has good reliability.

Isothermal transformation behavior of CSP (compact strip production) hot rolled 50CrV4 spring steel was systematically investigated by means of Thermecmastor- Z thermal simulation testing machine, OM, SEM and Vickers hardness tester. The results show that the isothermal phase transformation of austenite to ferrite and pearlite will take place when the steel is held at the temperature in the range of 680-550℃. With the decrease of temperature, the phase transformation kinetics firstly accelerates and then slows, the ferrite grains and lamellar pearlite are refined, and the hardness increases gradually. When the isothermal temperature is 620℃, the phase transformation completion time is 96s. Furthermore, the kinetics of transformation model is built based on the Johnson- Mehl- Avrami (JMA) theory and parameters of JMA kinetic are obtained. The time- temperature- transformation (TTT) diagrams of 50CrV4 spring steel are obtained, the results show that the calculated results agree well with the experimental measurements.

The traditional blast furnace ironmaking process has many problems such as long process flow, high dependence on coke and large environmental pollution. In order to solve these problems, the new ironmaking process of rotary kiln pre- reduction and smelting by coal and oxygen was developed. This new process has advantages of wide raw material adaptability, no coke consumption, less pollutant emissions and suitable for special iron ore resources. The mathematical model of the new process was established. Numerical simulation results show that the metallization rate of pre- reduction iron, smelting furnace gas oxidation degree and blast air oxygen content have great influence on coal and oxygen consumption. The coal and oxygen consumption reduces with the increase of pre- reduction iron metallization rate, the rise of oxygen degree of coal gas or the decrease of oxygen content of blast air. This process has a significant advantage in smelting special iron ore resources, which can make up the shortage of blast furnace ironmaking. It is also of great significance to reduce fuel consumption and CO2 emissions.

Cathodic charging, notch tension and hydrogen thermal desorption analysis test was used to study the delayed fracture behaviors of high strength steel 42CrMoVNb at different tempering temperatures, which were also compared with commercial structural steel 42CrMo. The results show that the delayed fracture resistance of experimenting steels increases with increasing tempering temperature. Since the tensile strength of 42CrMoVNb steel is higher than that of 42CrMo steel at same tempering temperature, the delayed fracture resistance of the former is lower than that of the latter. And in the high strength (more than 1250MPa), the delayed fracture resistance of 42CrMoVNb steel is evidently better than that of 42CrMo steel. This is because there is fine dispersed (V,X)C carbide precipitated in 42CrMoVNb steel when it is tempered at 550-650℃, which is regarded as a strong hydrogen trap and improve the delayed fracture resistance of the steel.

Process control was a very important content for BOF automation control. The development of the BOF control methods were summarized and introduced, the characteristics of oxygen lance control, oxygen flow control and flux feeding control were analyzed from automatic view respectively, and optimization approaches of process control for BOF were also discussed. The development trend of automatic control for BOF was prospected.

A comparative study was conducted on the effects of lamellar cementites and globular cementites on the cold drawing process and the mechanical properties of pearlitic wire steel, with the help of metallographic microscope, scanning electron microscope, transmission electron microscope, tensile tester and hardness tester. The lamellar cementites showed the deformation capacity to some extent during the cold drawing process. As the drawing strain increased, the pearlitic wire with globular cementites evolved into the fibrous form gradually and no obvious defects were found in the microstructure. The globular cementites turned to the drawing direction without any deformation of itself during the deformation process. And micro- cracks occurred in the cementite/ferrite interface due to stress concentration caused by pinning dislocations in spherical cementites. The strength and hardness of both pearlitic wires gradually increased as the drawing strain rose. And the pearlitic wire with lamellar cementites had a higher drawing hardening rate. The ferrite <110> texture formed in both pearlitic wires during the cold drawing process. Compared with the globular pearlite, the pearlitic wire with lamellar cementites had higher ferrite <110> texture intensity. And the difference of their ferrite <110> texture intensity became bigger and bigger as the drawing strain increased.

Internal nitride dispersion strengthened superalloy is a new type of high performance superalloy for combustion chamber. The background and development of this alloy were firstly introduced. And then the microstructure and properties of NS163 which is a typical internal nitride dispersion strengthened alloy were investigated. The results show that the microstructure of NS163 is simple in the temperature range of 900－1250℃, which is composed of austenite matrix and MC carbide. The recrystallization behavior of the cold- rolled sheet under the test condition was studied systematically. It is found that the solid solution temperature of the finished product should be 1200℃, and after solid solution at 1200℃, the sheet has 5 grade average grain size, excellent cold workability and low tensile strength at high temperature. The above results can help to optimize the microstructure of NS163 alloy sheet before nitriding and provide a basis for the evaluation of the strengthening effect of the alloy after internal nitriding.

The micro-structure and mechanical properties of 27SiMn steel was investigated by tensile test, hardness test, impact toughness, metallographic structure, XRD and SEM for quenching in 770-830℃, isothermal holding temperature in 360-420℃and isothermal holding time in 10-90min. The results show that 27SiMn can obtain of the ferrite, bainite and retained austenite of three-phase organization after heating at 790℃, holding 50min and isothermal holding at 380℃ for 20min. Mechanical properties are 27225MPa×% of the best overall performance, 825MPa of the tensile strength, 33% of the elongation, 47J/cm2 and HB219 of the impact toughness and hardness. This residual austenite content is 15.76% and the bainite incubation period is the shortest, which contributes to TRIP effect.

ombined with engineering practice and theoretic analysis, the bracket type-three point suspension/support type converters′ abnormal sound and vibration was investigated. According to the finite element theory analysis and engineering measurement, some phenomenon, such as ‘alternating elastic slip on brackets’ contact surface was found to be the main source of converter′s abnormal sound and vibration. An improvement proposal was raised——using four-point support suspension system on mammoth converter, finite element contrastive analysis results show that this kind of converter which was designed based on structure elasticity theory can greatly improve converter′s working quality and safety. This technique has been used for a converter with 280t of maximum tapping.

The effect of excessively edge gas flow on steel brick was investigated by numerical simulation. The model of water-cooling throat steel brick was built, and the temperature field and thermal stress field of hot face at the different gas temperature were calculated, and also the highest temperature and thermal stress of hot face, pipe and internal refractories were analyzed. The results show that when gas temperature rises from 500 to 1100℃, the highest temperature of hot face increases about 500 ℃, as well as thermal stress increases rapidly and the damage of steel brick was resulted in. Therefore, to control the growth of edge gas flow is necessary to avoid the formation of edge channeling and to make sure normal and stable working conditions of the steel brick works.