Effect of Ti/N Ratio on Impact Strength of High Strength Pipe Steel Welded Joint Heat-Affected Zone

Metallurgist - Kinetics of austenite grain growth within a heat-affected zone is studied for low carbon low-alloy steels of different alloying composition. The effect of Ti/N ratio on the metal...     

Aggregate stability of ZrO2 aqueous sols in electrolyte solutions

The aggregate stability of submicron and nanosized ZrO₂ aqueous sols of different origins and different dispersities at pH 3–10 in the KCl concentration range 10^?3–10^?1 M is investigated by flow ultramicroscopy and photometry. The results obtained are analyzed in the framework of the extended Derjaguin-Landau-Verwey-Overbeek theory and the Muller-Martynov theory of reversible aggregation. The extension of boundary layers of water near the surface of the ZrO₂ particles is estimated.     

Filter materials for fine cleaning based on metal fibers

Conclusions Permeable materials based on metallic fibers with porous layers sprayed on by the detonation gas method, in tangential filtering of media with ferromagnetic and abrasive impurities ensure fineness of cleaning 1–2 m with comparatively low hydraulic resistance. The application of a magnetic field to material with sprayed-on layer of magnetic alloy made it possible to increase permeability to ferromagnetic particles by a factor of more than 1.5.Translated from Poroshkovaya Metallurgiya, No. 1(325), pp. 77–80, January, 1990.     

On Unacceptable Use of Austenitic Sleeves and Surfacing Alloys for Repair of Carbon-Steel Equipment

Substantial part of equipment in gas-treating plants for removal of acidic impurities in oil and gas refineries needs repair, for which purpose austenitic sleeves are often used. Austenitic surfacing nickel alloys recommended for restoring the damaged surface by overlaying welding was found to be unsuitable because both the deposited material and the fusion line with the base metal are electrochemically heterogeneous, which makes repaired apparatuses insufficiently reliable. Use of sleeves is also inexpedient.__________Translated from Zashchita Metallov, Vol. 41, No. 4, 2005, pp. 441–444.Original Russian Text Copyright © 2005 by Medvedeva, Efimenko, Sidorenko.     

Special features of transformation kinetics of austenite in heat treatment of stamped and welded components made of 10G2FBYu steel

The results of investigations of the special features of austenite transformation kinetics during heat treatment of welded joints in components made of 10G2FBYu steel are used to determine the conditions for producing stamped and welded connecting components with strengths similar to that of the parent metal.     

Reduction of metals from vanadium converter slag by means of carbon and silicon

A method of alloying steel with vanadium by means of vanadium converter slag is considered. Thermodynamic analysis of the reduction of the oxides in vanadium slag during ladle treatment of the steel permits determination of the process parameters. The reduction of elements from oxides present in vanadium slag-in particular, vanadium, iron, and manganese-is evaluated in terms of the residual content of the corresponding oxides. It follows from thermodynamic calculations and experiments that, with optimal proportions of the reducing agents, relatively complete reduction of vanadium (98–99%) and iron from vanadium converter slag by carbon and silicon is possible, with limited reduction of titanium and manganese.     

Electronic control of electric motors in railway automation systems

Special linking circuits are required for the design of safe railway automation and remote control of trackside objects. They are usually based on devices with an asymmetrical failure rate, mainly first reliability class electromagnetic relays. The development of railway automation and remote control devices requires the use of state-of-the-art contactless semiconductor components. In this case, the use of functional converters or periodic testing of semiconductor switches and disconnection of the power supply from control objects in case of faults are needed. This article describes the use of a three-phase induction motor as the solution of the problem. They are used for the design of functional converters for railway automation electric motors control. It is proposed to use the low-frequency mode of power switch operation (switch frequency is 50 Hz) and to abandon the pulse-width modulation. The suggested technical solution is used in a CBI-MPC system for train traffic control at stations developed at the Center for Computer Railway Technologies of St. Petersburg State Transport University.     

Self-organization processes in the organic-inorganic disperse system containing silver nanoparticles

The morphology of complexly organized structures formed in polymer matrix under the action of silver nanoparticles has been investigated using atomic-force microscopy. The analysis of the set of experimental data and the results of the theoretical calculations of the pair interaction potentials has made it possible to propose the mechanism of formation of the “flower” structure, which is based on the interactions in the far potential minimum.