Study on the fabrication of in-situ TiB2/Al composite by electroslag melting

In-situ TiB2 particles can be synthesized via the salts-Al reaction by adding mixed K2TiF6 and KBF4 (Ti/B=1/2) salts into Al melt. In this research, a novel electroslag melting technology was proposed to synthesize TiB2 particles by the salts-Al reaction in order to reduce the reaction time period and purify the melt of composite. The effects of current of electroslag melting on the synthesis of TiB2 particles and mechanical properties of composite were investigated. The results showed that TiB2 particles could be in-situ synthesized by electroslag melting at 600 A for 15min. Compared with 60 min at 850°C of traditional LSM method, the efficiency of preparation was greatly improved. In addition, the dispersion of TiB2 particles in the composite prepared by electroslag melting was improved, meanwhile the non-metallic inclusions in the composite was reduced. The values of YS, UTS and El pct of composite prepared by electroslag melting were higher than that of the composite prepared by traditional LSM method.

Eloboration of Methods for Determination on Content of the Oxygen, Nitrogen, Hydrogen Admixtures in Titanium Aluminides

Titanium intermetalides (TiAl and Ti3 Al) and alloys on theirs bases applies in air — and spacetechnology and automobile industry. Physical and mechanical properties there alloys is better, then at classical Ti — or Ni — alloys, that are utilized in aeroplanes and rocets. Alloys, based on TiAl and Ti3Al, are made with utilization vacuum — arc, plasma — arc, induction- garnisage, magnetoperating electroslag melting, electron — beam melting with intermediate capacity, electroslag melting in inert atmosphere under «active» fluxes with metallic calcium, induction melting in muchsectional crystallizator and cold crucible, argon — arc melting with unexpended tungsten electrode in copper watercooling crucible. For connection of the details, that were made from these alloys, there were used welding by pressure, contact, electron — beam, diffusion welding. Alloys, based on titanium aluminide, have essential defects — high brittleness and low plasticity, viscosity and resistance thermal impact strength. Autors a lot of articles explaines these descriptions by structural special features of titanium aluminides and alloys on their bases, but does not consider possibilities of the influence by oxygen nitrogen, hydrogen admixtures. In literature information about methods of determination gaseous admixtures (O, N, H) contents in titanium aluminides and alloys on their bases are absented. Methods of determination oxygen, nitrogen, hyd­rogen contents in titanium aluminides on ana­lysers TC436, RO316, TN114, RH402 are created. Parameters of these methods are described in this article (temperatures of heating on graphite crucibles, times, masses of analytical samples).

Optimization of electroslag melting towards to titanium morphology improvement in combined Kroll process

Purpose The paper aims to optimize calcium difluoride electrical melting process towards creating titanium production with improved morphology by combining titanium reduction and electroslag melting processes. The study aims to explore optimal electrical heating power in the slag supplied via tungsten electrode and formation of a stable skull layer on water-cooled walls of a cylindrical stainless steel reactor, which is crucial for electroslag melting. Design/methodology/approach The multi-physical numerical modelling approach using commercial software COMSOL Multiphysics is presented in the paper by coupling electrical, heat transfer and fluid flow problems. The slag material phase change and corresponding changes of physical properties such as electrical conductivity and viscosity are modelled by step function, sharply changing value of parameter near the phase change temperature. A parametric study of applied electrical power has been carried out to find optimal conditions for the skull-layer formation. Findings The paper provides an estimation of necessary electrical power to avoid overheating or solidification of the top layer of slag, which is unacceptable for the combined Kroll process. The study also revealed important poloidal buoyancy flow with characteristic velocity of few cm/s of in the reactor, which governs the heat transfer process and formation of the skull layer. Research limitations/implications The presented simplification in numerical model offers high calculation speed but lacks fully developed phase change model, e.g. excluding latent heat. Also, heat transfer through radiation is neglected in the model. Originality/value The paper presents an original way to overcome the complexity of modelling slag electrical melting/solidification phenomena using temperature-dependent properties with step functions.