Kappa Carbide Precipitation in Duplex Fe-Al-Mn-Ni-C Low-Density Steel

The microstructural evolution of a Fe-Mn-Al-Ni-C low-density steel was studied. The lightweight low-density steels are a promising material for the transportation industry, due to their good mechanical properties and low density. The base microstructure of the investigated steel consists of ferrite and austenite. Thermo-Calc calculations showed the formation of an ordered BCC (body-centred cubic) B2 phase below 1181 °C and kappa carbides below 864 °C. The steel was produced in a vacuum induction furnace, cast into ingots and hot forged into bars. The forged bars were solution annealed and then isothermally annealed at 350, 450, 550, 650, 750, and 850 °C. The microstructure of the as-cast state, the hot forged state, solution annealed, and isothermally annealed were investigated by optical microscopy and scanning electron microscopy. The results showed the formation of kappa carbides and the ordered B2 phase. The kappa carbides appeared in the as-cast sample and at the grain boundaries of the isothermally annealed samples. At 550 °C, the kappa carbides began to form in the austenite phase and coarsened with increasing temperature.

Features of heat treatment of high-strength lean alloyed cold-resistant steel

Mechanical characteristics of an alloy, used for manufacturing parts of heavy-duty machines, operating under conditions of dynamic and cyclic loads, should meet increased requirements. According to the concept of lean alloying, quality of an alloy and highest possible properties of a chemical composition are determined by the modes of heat treatment. Results of a study of quenching temperature effect on microstructure and properties of a new lean alloyed steel MAGSTRONG 450L having the following chemical composition, %, mass: 0.21 С; 0.23 Si; 0.96 Mn; 0.03 Cr; 0.41 Ni; 0.023 Ti; 0.0021 B presented. Smelting of ingots of a given chemical composition was carried out in a vacuum induction furnace ZG-0.06L. Reduction of ingots was carried out on a hydraulic press П6334 and on a single-stand reversing hot rolling mill 500 duo. The samples were heated in a ПКМ 3.6.2/12,5 chamber furnace. Best mode of the hardening heat treatment of sheet rolled product of steel MAGSTRONG H450L was established, ensuring forming of a mixed structure, comprising 80% of lath martensite and about 20% of high temperature lamellar martensite. Such a structure ensures maximum values of impact toughness KCV–40 = 38 J/сm2 at high strength parameters (tensile strength σв = 1514 МPa, offset yield strength σ0,2 = 1243 МPа, hardness 460 HBW) and satisfactory indices of plasticity (percent elongation δ50 = 16 %) which correspondents to requirements ТС 14-101-1034–2015. Based on results obtained, recommendations were elaborated for heat treatment of the sheet steel MAGSTRONG H450L, thickness 8–20 mm as per OJSC “BELAZ” order. Application of the obtained results of the study will enable to create and perfect the technological modes of heat treatment of alloys with similar composition.

STUDY ON REMOVAL OF COPPER, TIN AND ARSENIC FROM IRON ORE, SCRAP AND STEEL IN THE LIGHT OF THE LATEST STATE OF METALLURGICAL TECHNOLOGY

The study investigates the ability to remove copper, tin and arsenic from iron ore, scrap and liquid steel based on the literature and thermodynamic calculations using the FactSage 7.2 software. Methods of removing Cu, Sn and As from iron-bearing materials, feasible in industrial conditions in the near term, were selected. Simulation tests with the use of the FactSage 7.2 software showed that under reduced pressure conditions Cu and Sn can be removed from the steel bath, while As evaporation is not possible. Laboratory tests were carried out, including the removal of Sn and Cu in the process of degassing of liquid steel in a deep vacuum in a vacuum induction furnace and the removal of Sn from iron ore in the sintering process. Under conditions of deep vacuum (below 40 Pa), high temperature (1670°C) and a correspondingly long vacuum treatment time (over 30 minutes), the efficiency of removing the copper and tin contents from the liquid steel of approximately 14 and 17% respectively was obtained. The iron ore sintering test with a high Sn content showed the effectiveness of reducing the Sn content during this process, amounting to approx. 30%.

Microstructure and Properties of TiAl-Based Alloys Melted in Graphite Crucible

This paper presents the chemical and phase composition, microstructure, and selected properties both at room temperature and at the temperature corresponding to the expected operating conditions of three successive generations of TiAl-based alloys (Ti-47Al-2W-0.5Si, Ti-45Al-8Nb-0.5(B,C), and Ti-45Al-5Nb-2Cr-1Mo-0.5(B,C)-0.2Si) melted in a vacuum induction furnace with high-density isostatic pressed graphite crucibles. The obtained results of mechanical and physical properties of the produced alloys were compared to the properties of reference alloys with similar chemical composition and melted in a cold copper crucible furnace. The effect of increased carbon content in the produced alloys due to the degradation of the graphite crucible during melting is higher strength properties, lower plastic properties, higher coefficient of thermal expansion, and improved creep resistance. It was shown that the proposed technology could be successfully used in the production of different generation TiAl-based intermetallic alloys.

Crystallographic texture of hot rolled uranium-molybdenum alloys

The uranium molybdenum (U-Mo) alloys have potential to be used as low enriched uranium nuclear fuel in research, test and power nuclear reactors. U-Mo alloy with composition between 7 and 10 wt% molybdenum shows excellent body centered cubic phase (γ phase) stabilization and presents a good nuclear fuel testing performance. Hot rolling is commonly utilized to produce parallel fuel plate where it promotes the cladding and the fuel alloy bonding. The mechanical deformation generates crystallographic preferential orientation, the texture, which influences the material properties. This work studied the texture evolution in hot rolled U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace, homogenized at 1000°C for 5 h and then hot rolled at 650°C in three height reductions: 50, 65 and 80%. The crystalline phases and the texture were evaluated by X-ray diffraction (XRD). The as-cast and processed alloys microstructures were characterized by optical and electronic microscopies. The as-cast, homogenized and deformed alloys have γ phase. It was found microstructural differences between the U7.4Mo and U9.5Mo alloys. The homogenized treatment showed effective for microsegregation reduction and were not observed substantial grain size increasing. The deformed uranium molybdenum alloys presented α, γ, θ texture fibers. The intensity of these texture fibers changes with deformation step.

Effect of Trace Mg on Impact Toughness of 2.25Cr1Mo Steel Doped with 0.056% P at Medium Temperature Aging Process

In order to investigate the effect of Mg addition on the embrittlement of Cr-Mo steels, the 2.25Cr1Mo steel plates containing Mg, P contents were refined with vacuum induction furnace and rolled with double-stick reversible rolling mill. The impact toughness evolution and microstructural characteristics of these steels after aging at 580 °C for up to 5000 h were systematically investigated. The grain boundary segregation behaviors of P, S, and Mg before and after aging were analyzed with auger electron spectroscopy (AES), and the microstructure characteristics of the steels were detected with optical electron microscope (OM) and transmission electron microscope (TEM). The research results show Mg addition can improve the impact toughness of the 2.25Cr1Mo steel to a certain extent even with 0.056 wt.% P doping. It was clarified that Mg can segregate to grain boundary during the aging process, and its strong segregation tendency can reduce the grain boundary segregation of P to some degree. The effects of Mg on the impact toughness after subjecting to 580 °C ageing, including element segregation behaviors at grain boundary, ferrite formation, prior austenite grain characteristics, and carbides at grain boundary were also identified and discussed.

TECHNOLOGY FOR THE MANUFACTURE OF CATHODES INTENDED FOR SPRAYING BACTERICIDAL COATINGS ON GLASS SURFACES

The paper presents the course and results of research into the production of cathodes for sputtering bactericidal coatings on glass surfaces in an industrial magnetron line at D.A. Glass. The study included the development of an innovative and comprehensive technology for producing various types of cathodes using a vacuum induction furnace. FactSage software was used for numerical simulations of phase transformations in the liquid and solid phase during the cooling and solidification of alloys, and the liquidus and solidus temperatures were determined using the thermal analysis method (DTA). The cathodes were made by casting plates that are components of ready-made cathodes. Zonal macrosegregation tests were carried out in the plate casting, which showed that the cast plates were characterised by high homogeneity in the entire volume. The chemical compositions of the cathodes corresponded to the required compositions, and their quality met the requirements for installation in a magnetron, which proves the correctness of the developed technologies of their production. The layers on the glass, sputtered in a magnetron device, were subjected to microbiological tests to determine the bactericidal (biocidal) properties of the glass. Preliminary results of these studies showed that the cathodes based on brass and bronze of the following type exhibited the best bactericidal properties: Cu90Sn10, Cu90Zn10, Cu80Zn10Al10, Cu80Ti20 and Cu65Ni18Zn17. The layers produced on the glass with the use of these cathodes exhibited the ability to deactivate the tested strains of microorganisms, including the elimination of bacterial growth. To further improve these properties, the composition of copper-based cathodes with various additions of tin and titanium, and with the addition of the following rare earth elements: cerium and lanthanum, which will be subjected to layer sputtering in the magnetron and microbiological tests as part of the next stages of the project, was modified.

The effect of M (M = Ce, Zr, Ce–Zr) on rolling microstructure and mechanical properties of FH40

Ce, Zr and Ce–Zr composite experimentl steel were prepared by vacuum induction furnace and 550 twin-roll reversible rolling mill. Optical microscope (OM), scanning electronic microscopy (SEM) and energy dispersive spectrometer (EDS) were used to observe the rolling microstructure of the experimental steel. The mechanical properties of the experimental steel were tested and analyzed. The effect of cerium zirconium oxide inclusions on nucleation, tensile and impact fracture mechanism of intragranular acicular ferrite (IAF) was investigated. The results show that the rolling microstructure of steel containing 0.0052% Ce and the steel under composite treatment containing 0.0053% Ce and 0.0055% Zr is refined. IAF generation can be induced by Al–Ce–O inclusion of the size of 4 µm or induced by Al–Ce–Zr–O + MnS inclusion of the size of 3 µm. The yield strength and tensile strength of the steel treated by Ce–Zr are 428 and 590 MPa, respectively, the elongation is 23.55%, the longitudinal impact energy at −60°C is 189 J, which are 31, 45, 46 J and 6.25%, respectively, higher than those of the matrix steel. The dimple of the experimental steel at the fracture surface is larger and deeper than that of the matrix steel. The small inclusions in uniform distribution contribute to the high tensile strength of the experimental steel.

Effect of vacuum smelting method on the quality of pipe steel of northern application

Pipe metal of Northern application must meet increased requirements of strength properties, low-temperature ductility, cold resistance and weldability. Cracks, skins, flaws, roll-ins and other defect are not allowed on the surface of pipes. The fulfillment of the requirements substantially can be provided by the process of steel smelting by a vacuum remelting method. Study of the effect of 03ХГ grade pipe steel smelting in vacuum and without vacuum on its contamination by nonmetallic inclusions and resistance against hydrogen cracking was accomplished. The smelting of ingots of adjusted chemical composition was carried out in a vacuum induction furnace ZG-0.06L. To imitate the process of hot roughing rolling, hydraulic press П6334 of 250 t force was used. Finishing rolling was carried out at reversible hot rolling mill 500 duo, combined with a controlled cooling facility. It was determined, that the samples, smelted in vacuum, had insignificant number of nonmetallic inclusions and withstand the test of resistance against hydrogen cracking; cracks were not detected on them. After testing on resistance against hydrogen cracking of the samples smelted without vacuum, cracks were discovered, located on both the surface and central layers amounting to 600 mm and 1700 mm length correspondently. It was shown, that steel smelting in vacuum allows to reach a high degree of the steel purity, results in increased crack growth resistance and in decreased number of nonmetallic inclusions in the pipe steel of Northern application.

Effect of Alloying Elements on Mechanical Properties of High-Strength Low-Alloy Steel

In this study, the two types of high-strength low-alloy steels were melted and cast in a vacuum induction furnace. Phase transition temperature of HSLA steel was calculated by JMatPro software. The calculation results show that the two different types of HSLA steels which have equal phase proportions of ferrite and austenite at a temperature of approximately 820 and 800 °C in HSLA-I and HSLA-II, respectively. In addition, the effect of chemical composition on the microstructure and mechanical properties of steels were studied. The results indicate that the ultimate tensile stress value of HSLA-II samples was greater than the HSLA-I samples by about 35%, and the yield stress and breaking strength value of HSLA-II were higher than HSLA-I as well.