Development of Universal Mould Geometry for the Teeming of Cylindrical Iron-Base Alloy Ingots

The presented work is aimed at developing a mould geometry suitable for casting both low- and high-alloy steel grades into 500 kg experimental ingots. The high Height-to-Diameter (H/D)-ratio mould currently used in COMTES FHT Inc. served as a reference and for finite element method simulations (FEM) of the filling and solidification process. The optimized mould geometry, balancing the porosity and segregations, was determined using MAGMA software. Four different steel grades were defined for the simulation. Case studies were carried out for 34CrNiMo6 (W.Nr. 1.6582), DHQ8, CB2 and borated stainless steel grades ranging from low-alloy steel to high-alloy steel. Extended user-defined criteria and verified boundary conditions were used to predict the formation of A-segregations in cast steel. Both primary (PDAS) and secondary (SDAS) arm spacings were modelled as well. The optimized mould shape and the casting assembly were designed based on the simulation results.

Wettability and solubility behavior of Fe–B–C binder on (Cr–Ti–C)-reinforced composites

Iron-base matrix composites containing Cr-20Ti-10C reinforcement fabricated by infiltrating at 1200°C to 1280°C for 30 to 60 mins are investigated in this work. Peculiarities of the formation of the interfaces between Cr-20Ti-10C hard alloy and Fe-3.1B-0.1C liquid alloy (wt. pct) are determined. It includes the study of the solubility between the iron-base binder and the reinforcement combined with the investigation of the contact angles of the liquid phase formed at infiltration temperature by sessile drop method. X-ray analysis as well as optical and scanning electron microscopy is employed to investigate the binder/particulate interfaces. The interfacial zones produced as a result of contact interaction consist of (Cr,Ti)7C3 and (Ti,Cr)3C phases embedded in α-Fe3(C,B) eutectic alloyed with Cr and Ti. The origin of the formation of the interfaces is probably related to the partial dissolution of the low-melting-temperature particulate phase identified as (Cr,Ti)7C3 in the molten Fe–B–C binder. When raising the infiltrating temperature and prolonging the infiltrating period, wetting properties of Cr-20Ti-10C improve. This fact opens the possibility to replace copper-base alloys as binder by a cheaper and stronger iron-base alloy.

FERRO-TITANIT NIKRO 143

Ferro-Titanit Nikro 143 is one of a series of metal-matrix composites manufactured by a powder metallurgy process and is a range of carbide-alloyed materials from Deutsche Edelstahlwerke. The Nikro 143 grade is an iron-base alloy containing 30 wt.% titanium carbide. Because of its high wear resistance and low tendency toward cold welding, Ferro-Titanit is particularly used in forming and cutting tools, hydraulic jacks for polymer production, and pelletizing and granulating cutter blades. This datasheet provides information on composition, physical properties, hardness, elasticity, and compressive, shear, and bend strength as well as fracture toughness. It also includes information on heat treating. Filing Code: Fe-168. Producer or source: Deutsche Edelstahlwerke GmbH.

Corrosion Properties of Candidate Materials in Supercritical Water Oxidation Process

Corrosion of constructional materials in supercritical water oxidation (SCWO) is one of the main obstacles to commercializing the SCWO process. Statistical analysis of corrosion research results indicate nickel-based alloys are the most widely applied materials in SCWO system among the candidate metals. The present paper reviews the corrosion characteristics of iron-base alloy, nickel-based alloy, titanium-base alloy, ceramics, niobium, tantalum, thallium and gold under the condition of SCWO. The selection scheme of materials is presented in SCWO system flow diagram in detail. The effects of alloying elements on the corrosion behavior of materials in the water environment with high temperature and high pressure water are summarized in this paper. Moreover, some further researches for material corrosion in SCWO process are also proposed. All work was contributed to selecting the appropriate constructional materials and reducing the corrosion damage in SCWO system.

Macroscopic and Microscopic Determinations of Residual Stresses in Thin Oxide Dispersion Strengthened Steel Tubes

To improve the efficiency of components operating at high temperatures, many efforts are deployed to develop new materials. Oxide Dispersion Strengthened (ODS) materials could be used for heat exchangers or cladding tubes for the new GENIV nuclear reactors. This type of materials are composed with a metallic matrix (usually iron base alloy for nuclear applications or nickel base alloy for heat exchangers) reinforced by a distribution of nano-oxides. They are obtained by powder metallurgy and mechanical alloying. The creep resistance of these materials is excellent, and they usually exhibit a high tensile strength at room temperature. Depending on the cold working and/or the heat treatments, several types of microstructure can be obtained: recrystallised, stress relieved…. One of the key challenges is to transform ODS materials into thin tubes (up to 500 microns thick) within a robust fabrication route while keeping the excellent mechanical properties. To prevent cracking during the process or to obtain a final product with low residual stresses, it is important to quantify the effect of the heat treatments on the release of internal stresses. The aim of this study is to show how residual stresses can be determined on different thin tubes using two complementary approaches: (i) macroscopic stresses determination in the tube using beam theory (small cuts along the longitudinal and circumferential directions and measurements of the deflection), (ii) stress determination from x-ray diffraction analyses (surface analyses, using “sin²Ψ" method with different hypothesis). Depending on the material and the heat treatment, residual stresses vary dramatically and can reach 800 MPa which is not far from the yield stress; comparisons between both methods are performed and suggestions are given in order to optimize the thermo-mechanical treatment of thin ODS tubes.