Advanced Materials Research Vols. 415-417

Abstract: The grain and grain boundary characteristics of HSLA100 steel quenched in the 2-phase region were investigated by electron backscatter diffraction (EBSD).The results showed that the austenite amount was controlled by the 2-phase region heating temperature and the composition and morphology of transformation products were mostly depended on the carbon content in austenite. With the quenching temperature in 2-phase region increasing, the dislocation density in bainite decrease as a result of the block bainite coarsening and mergering, which makes the subgrains with much more low angle grain boundaries (2°~15°) decreasing and the massive ferrite with more high angle grain boundaries increasing gradually. Furthermore, the lath martensite or bainite with high angle grain boundaries and subgrains with low angle grain boundaries gradually increase owing to new austenite grain increasing and growing up. With the roles of above two interactions, some EBSD characteristics such as the packet size and the number fraction of high angle grain boundaries all have a peak present at 740°C

Abstract: The residual Mg content ,spherodize ratio and nuclei of spherodial graphites(abbreviated SG) were studied by casting a series of similar composition ductile iron rods and white samples with different holding time of spheroidizing. The results indicate that the residual Mg content in the ductile iron was less and less as the holding time grows ,which causing the morphology of graphites transfer from spherodial to oval. Spherodize ratio change law is not continuous as increasing the residual Mg content which is divided at the 0.02%. The morphologies of nuclei of SGs core are typical examples of the highly magnified structure of spherical and irregular polygons; the diameters are about 0.5~2μm, consisting of (Mg, Ca)S along with CeO₂ and MgO. Disregistry δ between the nucleus compounds and graphite are low,which indicates that nucleus compounds are good nucleating site for SGs.The Mg element in nuclei of SG just act as nucleation substrates.it is the Mg which maybe simple substance in the metallic matrix that act as the role of spherodizer determines the graphite shape.

Abstract: The experiments of high nitrogen steels refining have been researched with high pressure and bottom-blown nitrogen in laboratory. We can gain high nitrogen nickel-free stainless steels that its content is more than 0.9%. The research indicates that the temperature influences nitrogen content greatly in the processes of smelting and concreting. The results are shown that saturated nitrogen content in steel increased slightly. When the temperature is as high as 1913K, the nitrogen content can reach 1.191%.

Abstract: This paper fusions advantages of the grey forecast, fuzzy control and the traditional PID control, puts forward the grey prediction fuzzy PID control method. This method is based on PID Controlling Regulation determine interrelated parameters with the fuzzy reasoning, use online grey prediction theory forecast the system outputs which instead of the controlled object measurement value to exert feedback control for the system. The simulation results show that this control ways have more excellent control quality than traditional PID and Fuzzy PID.

Abstract: In order to verify the processability of a special-shaped stone machining center’s horizontal working portion, to process complex stone products. On the basis of analysis of the physical characteristics of diamond cutting tool and stone, create a model and use UG software to program, making this machine center’s dedicated post processor. Simulate NC code that is generated with VERICUT software, optimize the cutting parameters and analyse its surface quality. Avoid interference in the program, gouge, collisions and other phenomena by adjusting the tool axis’s attitude and the tool paths. Actual process verified the reliability of the program, technological parameter is rational, quality of the parts’ surface is well. Make precisely outline and tool wear is small, overcome the drawbacks of CNC system, get a higher efficiency.

Abstract: The δ→γ phase transformation in the steel was studied in detail, and the relationship between δ→γ phase transformation and the crack formation in continuous casting slabs was discussed as well. The results indicate that the micropores are formed at the positions where δ-phase transformation terminates during the δ→γ phase transformation for low-carbon non-peritectic steel. The micropores will also be formed at the positions where the peritectic reaction of the steel terminates, then the pores are remained on the grain boundary of γ-phase when γ-phase becomes granulated. The micropores distributing on the grain boundary of γ-phase is one of the results for the crack formation of continuous casting slabs and the obvious plasticity decrease of δ-phase zone in the steel. The theoretical analysis results are basically consistent with the experimental results.

Abstract: Nickel is difficult to be enriched from laterite nickel ore with mineral processing. The traditional processes used for manufacturing nickel need high energy consumption and yield a large amount of metallurgy waste residue. A new method was developed. Nickel and iron was enriched firstly by leaching laterite nickel ore in concentrated alkali solution. In the process, silicon entered to the solution in the form of sodium silicate, and nickel and iron were remained in the residue in form of simple oxides due to the destroying of silicate structure. Ferronickel was obtained by magnetic separation after reducing the residue with carbon. The silicon dioxide was prepared using carbonation decomposition from the leaching solution. The alkali used in the leaching process was recycled and reused using causticizing technology.

Abstract: Thermal mechanical experiment of step-cooling of 600MPa hot-rolled DP steel after compressed was carried out on Gleeble-1500 thermal mechanical simulator, using design of butterfly-shaped sample. Microstructure evolution during step-cooling and its effect on mechanical property of tested steel were analyzed. It is shown that, dual phase microstructure which martensite islands disperses in fine grain ferrite matrix is obtained by holding for 8~10s at 670°C followed accelerated cooling to 200°C. With increasing of holding time, grain size of ferrite coarsens, and volume fraction of ferrite has few changes. Meanwhile, tensile strengths of tested steel are all near 600MPa. That is to say, ferrite transformation is adequate during holding for 8~10s at 670°C and tensile strength of dual phase steel is stable accordingly.

Abstract: A new kind of bainite steel with ultra-low carbon content and Nb, Ti alloys has been developed. By applying thermomechanical control process, water quenching and tempering at different temperature, excellent properties have been obtained when tempered at 450°C, with the yield strength of 813MPa and elongation of 16.2%. The morphology observed by SEM shows that the microstructure consists of fine lath-shaped bainite, polygonal ferrite, quasi-polygonal ferrite and a small fraction of residual austenite or martensite-austenite constituents. In a TEM study plenty of precipitates with the size about 5-10nm were observed interacting with the dislocations, which is very significant for the optimization of strength and ductility.

Abstract: An Fe-6.2wt%Si as-cast strip with equiaxed grains and obvious {001} fiber texture was produced by twin-roll strip casting process. The as-cast strip was successively performed by hot rolling, warm rolling and annealing. The microstructure and texture evolution at each process stage were investigated by using electron backscatter diffraction and x-ray diffraction. It was found that the finally annealed sheet was characterized by large grain size, mild γ-fiber texture and obvious {001} fiber texture. Therefore, a high magnetic induction and a low core loss were obtained in the sheet.