Materials Science Forum Vols. 561-565

Abstract: Based on the existing smelt condition, after exploring and practicing, 2500m3BF of the Stainless Steel Branch of Baosteel procured breakthrough on the intensifying smelting. By researching technologies of compounding many coke kinds for lessening the effect to the BF, adjusting the proportion of each ore to optimize the structure of charging, increasing the gas using ratio for cutting down fuel ratio, and taking low silicon smelting to optimize BF operation, the general indicators in the top position among the same type blast furnaces in china.

Abstract: An hBN-Y2O3 composite investment moulding material was developed for investment casting Ti-6Al-4V alloy. Hexagonal boron nitride (hBN) powders plus a few Y2O3 powders were used as the investment mould material to prepare the shell mould with colloidal yttria as binder. The results show that the hBN-Y2O3 composite investment mould can be used to cast Ti-6Al-4V alloy, and has lower cost compared with the traditional yttria based investment mould, because of chemically inert of hexagonal boron nitride and its lower density. Moreover the interfacial reaction between the Ti and hBN-Y2O3 composite shell mould was investigated with measurement of microhardness and scanning electron microscopy (SEM) with energy dispersive (EDS).

Abstract: The applications of the single-hole top lance, the 110-three-holes top lance and the 150-three-holes top lance in the speed of the decarburization are compared. The amount of the Chromium oxidized, and the temperature-increasing speed of the bath is analyzed. The result shows, if the lance gap is set suitably, the 110-three-holes top lance will be the most beneficial to the stainless steel-making in the AOD when the high-carbon pre-metal from the EAF is charged.

Abstract: The aluminium alloy and mild steel sheets were joined with mechanical clinching. Deforming behaviour of the two sheets during the clinching was observed from finite element simulation and an experiment to avoid defects. The fracture of the upper sheet, necking and separation are caused by the small upper sheet thickness in the thick total thickness, the small lower sheet thickness in the thick total thickness and the small lower sheet thickness, respectively. The joining range for the combination of the upper aluminium alloy sheet of and the lower steel sheet of is larger than that of the reverse combination. The effect of the difference between the flow stresses of the two sheets on the deformation behaviour was examined.

Abstract: As a series of fundamental study on the gas evaporation method, a levitation-melted iron was evaporated in the gas mixtures of argon + ammonia, argon + nitrogen to synthesize ultrafine particles of iron nitride that got attention as one of the magnetic materials. The particles that were obtained in the gas mixture of argon and nitrogen were α-Fe. But nitrogen was chemisorbed on the surface of the particle, because nitrogen content in the particles was larger than the solubility of nitrogen in iron. The particles that formed in the mixed gas of argon and ammonia were Fe4N. The mean size of the particles of iron nitride was approximately 60 nm. The formation ratio of iron nitride was about 86 %.

Abstract: Laser rapid forming (LRF) is introduced as a novel fabrication process for Ni-based superalloy Rene88DT. The effect of heat treatment parameters of quenching rate and aging time on size and distribution of γ′ precipitation was investigated. The heat treatment parameters were first determined by DSC, and then optimized based on the examination of the microstructure and mechanical properties of heat treated LRF Rene88DT. The experimental results show that, the precipitation of γ′ is inhomogeneously distributed as a result of uneven heat-cycle during LRF in as-deposited Rene88DT, resulting in low mechanical properties. After being heat treated at 1165°C, 2h/AC + 760°C,28h/AC, γ ′ precipitation are homogeneously distributed with the size of 40~60nm, and the tensile strength of heat treated sample shows an increase of 400MPa as compared to that for as-deposited. The yield strength is close to that of the PM+HIP standard.

Abstract: The influence of tool control in non-linear friction stir welding (FSW) on mechanical properties of joints was investigated. FSW is widely applied to linear joints. It is impossible for five axis FSW machines, however, to keep all the FSW parameters in optimum conditions at non-linear welding. Non-linear FSW joints should be made by compromise with the order of priority for FSW parameters. The tensile test results of butt joints with rectangular change in welding direction on plate plane (L-shaped butt joints) with various welding parameter change. It was found that turn to the retreating side is encouraged when welding direction change. And the method of zero inclination tool angle is effective at non-linear and plane welding.

Abstract: The article introduce the process of Electric Arc Furnace with Dephosphorized hot metal charging for melting stainless steel in Baosteel stainless steel Branch. Based on the practice of production, The main factors affecting the process of EAF with De-P HM charging are theoretically analyzed, such as using oxygen, the material charging and making slag. The optimization of hot metal charging can advance the use of chemical and physical energy, reduce the consumption of power. The optimization of using oxygen can increase the use of chemical energy. The optimization of material charging can reduce the oxidation of Cr. Making foamy slag can advance the transformer capacity and the use of power. Based on the character of the process EAF with De-P HM charging for Melting Stainless Steel, EAF productivity increased were reached with application of integrated control theory on EAF process in Baosteel stainless steel branch.

Abstract: Transitions in the mechanical behaviour of solidifying alloys influence feeding mechanisms and defect formation during many casting processes. This paper explores dendrite coherency and the cracking transition during the equiaxed dendritic solidification of Mg alloy AZ91 using the continuous-torque technique and vane rheometry. The two techniques yielded similar dendrite coherency values of ~17% solid, and the cracking transition occurred at 40% solid in vane rheometry tests. These transition values are similar to those reported for Al alloys with equiaxed dendritic morphology and a similar grain size.