Research and development of 780 MPa cold rolling TRIP-aided steel

As an industry-university cooperative project, an experimental research was conducted to develop a new cold-rolled transformation-induced plasticity （TRIP） steel with a tensile strength of 780 MPa and an elongation of 25% under the conditions that some processing parameters were preestablished according to the actual conditions of factory production lines. The optimal heat treatment conditions for obtaining excellent strength-ductility balance, specifically in intercritical annealing temperature and isothermal treatment temperature, were investigated by means of thermal simulation tests. Ultimately the desirable mechanical properties were attained successfully, and the microstructure and retained austenite stability were studied by optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It has been discovered that the sizes of retained austenite grains are generally proportional to the sizes of carbon-clear space （ferrite and bainite） around them, and there is marked selectivity in their transition sequences under stress-strain.

INVESTIGATION ON HOT DUCTILITY AND STRENGTH OF CONTINUOUS CASTING SLAB FOR AH32 STEEL

By means of Gleeble-1500 testing machine, the simulation of continuous casting process forAH32 steel was carried out and hot ductility and strength were determined. The cracking sensitivity was studied under the different temperatures and strain rates. The Precipitations of AIN at different temperatures and the fractures of high-temperature tensile samples were observed by using TEM （transmission electron microscope） and SEM （scanning electron microscope）. The factors affecting the brittle temperature zone were discussed.

Temperature distribution and dynamic control of secondary cooling in slab continuous casting

To predict and optimize the temperature distribution of slab continuous casting in steady operational state, a three-dimensional model （named ＂offline model＂） based on the heat transfer and solidification theories was developed. Both heat transfer and flux distribution characteristics of the nozzle sprays on the slab were considered, and the complicated boundary conditions, such as spray cooling, natural convection, thermal radiation as well as contact cooling of individual rolls were involved in the model. By using the calibrated caster dependent model factors, the calculated temperature and shell thickness accorded well with the measured. Furthermore, a dynamic secondary water cooling control system was also developed on the basis of a two-dimensional transient heat transfer model （named ＂online model＂） and incremental PID control algorithm to reduce slab surface temperature fluctuation in unsteady state. Compared with the traditional spray table control method, the present online model and dynamic PID control demonstrate a higher capability and flexibility to adjust cooling water flowrate and reduce slab surface temperature fluctuation when the casting speed is changed.

Effect of inclusions on the formation of acicular ferrite in Ti-bearing non quenched-and-tempered steel

Nucleation of acicular ferrite and its influence factors in non quenched-and-tempered steel was studied by using TEM and thermodynamic calculation. The results show that the complex particles with a center made of Ti oxide, Al2O3, and silicate and an outside made of a small quantity of mixture of TiN and MnS are able to act as ferrite nucleation nuclei. The acicular ferrite percentage changes little with Ti. When the oxygen content was 80 ppm, the volume percentage of acicular ferrite decreased due to an increase in allotriomorphic ferrite. The larger the cooling rate and the shorter the incubation time, the finer the titanium oxide and the higher the nucleation ratio of acicular ferrite.

Separation occurring during the drop weight tear test of thick-walled X80 pipeline steels

A separation phenomenon occurring during the drop weight tear test of commercial thick-walled API （American Petroleum Institute） X80 strip steel was investigated in this work. Microstructural analysis showed that the band structure of bainite elongated along the rolling direction works as the initiation sites of separation. The propagation of separation can be promoted not only by the occurrence of the band structure of martensite/austenite constituent, prior austenite grain boundaries, and elongated bainite, but also by fine acicular ferrite and bainite. Wide separation formed in the former case, while the narrow one appeared in the latter case. acicular ferrite in thick-walled X80 pipeline steel in order Some methods were proposed to obtain fine and homogeneous to minimize the occurrence of separation.

Mathematical Model of Combustion in Blunt Annular Ceramic Burner

The computer simulation of the combustion process in blast furnace(BF) stove has been studied by using the k-ε-g turbulent diffusion flame model.The combustion process in blunt annular ceramic burner was calculated by using the software.The profiles of gas and air velocity,temperature of the combustion products,concentration of the components,and the shape and length of the flame during combustion have been researched.Compared with the original annular ceramic burner,the new design of the blunt one improves the mixing of the gas and the air significantly,and shortened the length of the flame.

Multi-boiler System Optimization in Integrated Steelworks Based on Decomposition and Coordination Method

As for the existing problems of boilers in integrated steelworks, the multi-boiler system could be quantitatively optimized with the decomposition and coordination method. Then, case studies were carried out based on the data of an integrated steelworks. Two groups of actual production records were contrastively analyzed, and the calculation results from the optimized program of these two groups indicated that for groups 1 and 2, the costs fall by 5.06% and 3.79%and the fuel consumptions decrease by 2.72% and 1.45%, respectively, compared with the actual data. To analyze the cost and fuel consumption change under the same condition of total load demand, assigned fuel consumption and water temperature, five sets of data were selected for further analysis. It was shown that the total cost and fuel consumption of the optimized program could fall by 3.5% and 1.6% respectively, compared with the actual production records. The optimal allocation significantly contributed to energy conservation and cost reduction. The effects of the system energy conservation cannot be realized by single equipment energy conservation. They were complementary to each other, and should be put on the same stage.

Austenitization Behaviors of X80 Pipeline Steel With High Nb and Trace Ti Treatment

The austenitization behaviors of two high niohium-containing X80 pipeline steels with different titanium contents, including the dissolution of microalloying precipitates and the austenite grain growth, were investigated by using physical-chemical phase analysis method and microstructural observation. The results illustrated that most niobium could be dissolved into austenite during soaking at 1 180 ℃, whereas little amount of titanium could be dissolved. It was found that during soaking, the austenite grain growth rate was initially high, and then decreased after soaking for 1 h; moreover, the austenite grains grew up more rapidly at temperatures above 1 180 ℃ than below 1 180 ℃. The results show that the steel with titanium content of 0. 016% has a larger austenite grain size than that with titanium content of 0. 012% under the same soaking conditions, which is explained by considering the particle size distribution.

露天与地下协同开采模式与方法研究（英文）

在大型金属矿山露天开采的末期,需要经历露天开采转地下开采的过渡时期,但两者存在着相互干扰的问题,造成过渡期安全生产条件差和产能衔接困难。为了解决过渡期开采安全条件差和产量衔接困难等技术难题。本文以大孤山矿山为例,针对过渡期矿体条件,提出并建立了适合协同开采的楔形转接新型过渡模式,其完全取消了境界矿柱以及人工形成覆盖层的工艺,并将挂帮矿诱导冒落法开采技术与露天底部矿量陡帮延深开采技术有机结合,用于实际开采过程中。结果显示,1)露天境界细部优化减少岩石剥离量,2)实现协同开采过渡期产能稳定衔接。研究表明,该方法地下采用诱导冒落法开采挂帮矿,露天采用陡帮开采工艺开采坑底矿,按露天与地下开采工艺的优势对比优化露天延深开采的细部境界,本研究在一定程度上为过渡期矿山露天转地下开采提供了真实准确的技术支撑。

Heterostructured Nitrogen and Sulfur co-Doped Black TiO2/g-C3N4 Photocatalyst with Enhanced Photocatalytic Activity

Conventional titanium dioxide(TiO2)photocatalyst could absorb only ultraviolet light due to its wide bandgap.In this paper,black TiO2 with narrow bandgap was prepared by introducing oxygen vacancies.Meanwhile.nitrogen(N)and sulfur(S)elements were doped to further broaden the visible light response range of TiOx(NS-BT),and then heterostructured N.S-doped black TiOz/g-C3Na(CN/NS-BT)was successfully constructed by easily accessible route.The formation of CN/NS-BT heteroiunction structure increased the generation and separation efficiency of photogenerated electron-hole pairs,as well as accelerated the transfer rate of the carriers.The as-prepared CN/NS-BT exhibited excellent photocatalytic performance towards the degradation of Rhodamine B(RhB)under visible light irradiation with satisfactory stability.The apparent reaction rate constant of CN/NS-BT(0.0079)was 15.8-fold higher than that of commercial P25(0.0005),The structure,morphology,chemical composition and optical properties of the as-prepared CN/NS-BT were characterized by various analytical methods,and possible photocatalytic enhancement mechanism was proposed.Overall,CN/NS-BT composites look promising as photocatalytic material for future environmental treatment.

Simulation and optimization of a combined cycle power plant with low heating value fuel gas

Combined cycle power plant(CCPP)usually plays an important role in balancing byproduct gas generation and consumption in integrated iron and steel plant.The low heat value fuel gases,such as blast furnace gas(BFG)or mixed gas with Coke oven gas(COG)and BFG,are preferred to be used in high-efficient CCPP for power generation.In practice,the general heat value of mixed gas can be set in the range of 3500–4400 kJ/Nm^(3).This paper presents a methodology to simulate operating parameters of CCPP with BFG.A generic model of gas turbine with open loop stage cooling employing air is used to simulate the performance of gas turbines cycle under different compressor pressure ratios and turbine inlet temperatures(TIT).The isentropic efficiencies for gas compressor and gas turbine are supposed to be constants and set corresponding to published industrial experience.The steam cycle is composed of classical double-pressure heat recovery steam generator(HRSG)and steam turbines according to gas turbine outlet temperature.Specific work,gas turbine cycle efficiency,cogeneration thermal efficiency and coolant air flow requirements are evaluated to find the optimal compressor pressure ratio and TIT.The research results are useful to select the optimum operating parameters of CCPP with BFG.Performance features were estimated with the help of compression ratios 12.5–20 and combustor exit temperature 1150–1350℃.

Technology for high performance TRIP steel

Thermodynamics of martensite transformation in low alloy TRIP steel was evaluated.It follows from the calculation that ε phase might be formed at above room temperature in the low Mn steel.Tested steel was therefore prepared according to the estimation result.High volume fraction of retained austenite(above 20%) containing 1.37%C was obtained in the steel after continuous annealing treatment.Tensile test showed that the ultimate strength of the steel was 1248 MPa,elongation rate 25%,the product of strength and elongation rate 31200 MPa%,reaching the grade of the third generation automobile steel.XRD detection indicated that after tensile test there existed ' martensite while TEM revealed that ε martensite also existed in the steel.Strengthening-toughening of the steel was thus raised due to the effect of transformation induced plasticity of two kinds of martensite.In addition,the phase stability of carbonitrates containing V was estimated and the complex micro-alloying effect was applied to the steel to control the size of austenite(about 1 μm) and enhance the stability of austenite.

Determination of Forward Slip Coefficient During Heavy Rail Rolling Using Universal Mill

The forward slip coefficient is one of the most important parameters for heavy rail rolling using universal mill.For simplifying the theoretical model,the vertical roll with box pass was simplified as an equivalent flat roll first.Second,the neutral angle of horizontal roll and vertical roll was represented.Then,the equation of neutral line on the flank of horizontal roll was determined and the forward slip coefficient of the web was derived according to different positions of neutral line.Finally,the forward slip coefficient of the top and base of heavy rail was obtained.The theoretical results were basically in agreement with the experimental data.

The Effect of Slab FC-Mold Technology on Fluctuations of Liquid Steel

The application for FC-Mold(Flow Control Mold)technology is researched in Ansteel slab caster,and the fluctuations of liquid steel in different parameters are emphasis researched.The results show that the fluctuation of liquid steel can be decreased 50%by using FC-Mold,and the value is decreased from±5mm to±2mm.The casting velocity can be increased 0.5m/min by using FC-Mold.The effect of FC-Mold is increased with increasing of current.And FC-Mold can restrain the unstable liquid steel from velocity changing.The statistic application results for 610 strands show that the degraded ratio for automobile steel is decreased 6%.

Experimental study on the 3D vibrated packing densification of binary sphere mixtures

The packing densification of binary spherical mixtures under 3D mechanical vibration was studied experimentally. The influences of vibration frequency （ω）, volume fraction of large spheres （XL）, sphere size ratio （r, diameter ratio of small to large spheres）, and container size （D） on the random binary packing density （p） were systematically analyzed. For any given set of conditions, there exist optimal ω and XL to realize the densest random binary packing; too large or small ω and XL is not helpful for densification. The influences of both r and D on p are monotonic; either reducing r or increasing D leads to a high value of p. With all other parameters held constant, the densest random packing occurs when XL is dominant, which is in good agreement with the Furnas relation. Moreover, the highest random binary packing density obtained in our work agrees well with corresponding numerical and analytical results in the literature.

Effect of magnesium injection process on hot metal desulfurization

To solve the technical problems of hot metal desulfurization by injecting magnesium particulate, a new method of hot metal desulfurization by bottom-blowing magnesium vapor combined with mechanical agitation was put forward. The effects of three different desulfurization processes on the desulfurization efficiency were studied in view of thermodynamics and kinetics. It was found that the utilization efficiency of magnesium can reach 82.6% and desulfurization efficiency can reach 86.2% during the first 4 min using the method of magnesium vapor injection combined with mechanical agitation. The gasification of magnesium powder leads to significant splashing and magnesium losses in the process of magnesium powder injection, resulting in a low utilization efficiency of magnesium of 51.8% and a low desulfurization efficiency of 55.76%. Activation energy for a first-order kinetic relationship between magnesium powder and sulfur was measured from the experiments, which was 142.82 kJ/mol in the temperature range of 1573-1723 K. The activation energy of the reaction between magnesium vapor and sulfur was around 54.8-65.0 kJ/mol in the temperature range of 1573-1723 K, which indicates that the desulfurization with magnesium vapor proceeds relatively easier than the desulfurization with magnesium powder.