Visualization and simulation of steel metallurgy processes

Steel production involves the transfer and transformation of material and energy at different levels, structures, and scales, and this process incurs substantial information in the material and energy dimensions. Given the black-box feature of iron and steel production processes, process visualization plays an important role and inevitably benefits parameter correction, technical support decision-making, personnel training, and other aspects of the steel metallurgy industry. The technological characteristics of the entire process in the steel industry were analyzed in this study, a visualization technology route based on virtual reality(VR) was built, and the important components of visual simulation system for steel industry and the important technical points needed to realize the system were proposed. On the foundation, a visual simulation model for the process scheduling of the iron and steel enterprise raw materials' field, slab, and hot rolling processes was built, and a visualization simulation platform of the iron and steel metallurgy plant-wide process, including ironmaking, steelmaking, hot rolling, and cold rolling, was developed. Lastly, the effectiveness of platform was illustrated by practical application.

Wear and mechanical properties of carburized AISI 8620 steel produced by powder metallurgy

The effect of carburization on the tensile strength and wear resistance of AISI 8620 steel produced via powder metallurgy was investigated.Alloys 1 and 2(with 0.2wt%C and 0.25wt%C,respectively)were first pressed at 700 MPa and then sintered at 1300,1400,or 1500℃for 1 h.The ideal sintering temperature of 1400℃was determined.Afterward,Alloys 1 and 2 sintered at 1400℃were carburized at 925℃for 4 h.The microstructure characterization of alloys was performed via optical microscopy and scanning electron microscopy.The mechanical and wear behavior of carburized and noncarburized alloys were investigated via hardness,tensile,and wear tests.After carburization,the ultimate tensile strength of Alloys 1 and 2 increased to 134.4%and 138.1%,respectively.However,the elongation rate of Alloys 1 and 2 decreased to 62.6%and 64.7%,respectively.The wear depth values of Alloy 2 under noncarburized and carburized conditions and a load of 30 N were 231.2 and 100.1μm,respectively.Oxidative wear changed to abrasive wear when the load transitioned from 15 to 30 N.

Modification of MgO·Al_2O_3 spinel inclusions in Al-killed steel by Ca-treatment

The modification of MgO·Al2O3 spinel inclusions in Al-killed steel by Ca-treatment has been studied by industrial trials and thermodynamic calculations.In the industrial trials,samples were taken systematically during the refining process in which the molten steel was treated by calcium,and the characters of the inclusions were analyzed using scanning electron microscopy （SEM） and energy dispersive spectra （EDS）.The effects of Ca-treatment were evaluated by tracking the compositions of the inclusions.The results show that the modification of MgO·Al2O3 spinel inclusions by Ca-treatment is effective and the transformation sequence of the inclusions during the refining is Al2O3 →MgO·Al2O3 →liquid complex inclusions.The modification of spinel inclusions by Ca-treatment was calculated by FactSage 6.0 utilizing its free-energy minimization routines.The results of thermodynamic calculations indicate that spinel inclusions are easier to be modified than Al2O3 inclusions and the spinel inclusions in 30CrMo steel would transform to liquid complex inclusions when the content of dissolved Ca in the molten steel exceeds 1×10-6.Also,the results show that adding more calcium into the molten steel would lower the contents of Al2O3 and MgO and increase the CaO content of the inclusions,while the change in SiO2 content is little.

Basic properties of steel plant dust and technological properties of direct reduction

Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas （OG） sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 mm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces （BF） if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250℃ for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the bri-quettes were kept at 1250℃ for 6 min.

混合法添加MnS的Fe－Cu－C－MnS烧结钢中MnS的长大

MnS growth in sintered steels with admixed Fe, Cu, C and MnS has been investigated by SEM and X-ray diffraction, MnS in Fe-Cu-C-MnS sintered steels in which MnS has been admixed is not stable and MnS growth may be ascribed to sintering between MnS particles or reaction between MnS and Fe, Cu, C elements.

THEORY OF BAINITIC TRANSFORMATION: A MODEL WITH COUPLED FIRST-ORDER PHASE TRANSFORMATIONS

The Ginzbury-Landau theory for bainitic transformation was devised, which contains two first-order phase transformations, one being reconstructive represented by the diffusional proeutectoidal precipitation of ferrite, and the other the displacive transformation. It provides a coupled mechanism for the formation of bainite. With the numerical simulation results, a diffusion-induced nucleation and a diffusion-accompanied growth of displacive transformation were suggested. This theory can be helpful to over- throw the thermodynamic difficulty of displacive transformation above the Ms temperature, and also helpful to understand the Bs temperature, the partial supersaturation, the single variation of bainitic carbides, and the incomplete-reaction phenomenon of bainitic transformation, etc..

Effect of furnace atmosphere on sintering process of chromium-containing steel via powder metallurgy

During a powder metallurgy process such as sintering,the primary role played by the atmosphere in furnace is to prevent an excessive oxidation of powder compacts in case of the formation of oxides as residuals on powder surfaces.In particular,the adjustment of furnace atmosphere is the key to eliminate the phenomenon"decarburization"likely to occur in carbon-containing compacts.A continuous belt furnace was used to stabilize the potentials of carbon and oxygen in zones divided by sintering,delubrication,and cooling.Chromium and manganese,which are sensitive to oxygen,were added to improve mechanical properties in a cost-effective way.Powders of steel containing chromium were sintered in an atmosphere composed of CO,O_(2),and H_(2).The effects of atmosphere,lubricant,and graphite on oxidation(or reduction)and decarburization(or carburization)were investigated.Superior quality was achieved under the control of delubrication atmosphere.It is indicated that in a protective atmosphere,the chemical reactions occurring at various stages took remarkable effect on the quality of sintered compact.The potentials of oxygen and carbon in a continuous belt furnace were monitored and analyzed using an on-line thermal measuring unit consisting of thermocouple,oxygen probe,and carbon monoxide sensor.The avoidance of oxidation and decarburization promises desired micro structure and carbon content and satisfactory properties through the adjustment of technical parameters,e.g.,the composition of gases in delubrication and various sintering zones,the rate of gas inlet,and cooling rate.