Investigation of the modification effect on performance properties of cast iron molds

Research is devoted to the influence of the technological method of modifying gray cast iron for the manufacture of steel casting molds. Heavy operation imposes stringent requirements both on the design of molds and on the materials from which they are made. They reliably withstand the effects of steel poured into them, having a temperature of 1600–1700 °C, thermal shock, which is directly proportional to this temperature, as well as significant effects of cyclic thermal stress and deformation. Specific operating conditions of molds (high heating temperature, their installation on movable and stationary ditches, intensive traffic flows, etc.) complicate the necessary processes directly during their operation. Modeling geometric shapes on a scale of geometric similarity 1:10. Tests were carried out on molds cast from cast iron for consumable electrodes, modified with ferrosilicon (FS65 GOST 1415-93), primary aluminum A99 (GOST 11069-2001), vanadium slag (SHVD-1 TU14-11-178-86), FSB-30) and silicomishmetal (SIMISH-1). These modifiers were chosen for modification, as they are widely used in production. Thus, the conducted studies of the nature of the deformation of the walls of the molds and the stress-strain state on models made of gray and modified cast iron make it possible to assess the advantages and disadvantages of the resulting structure and shape of graphite. Further, the methods of the rational formula of the outer surface of profiled and sheet molds are used, having predetermined the nature of destruction in advance. The use of thin-walled used rational forms can significantly reduce their specific consumption. The study of the quality of the metal cast into the experimental curved outer surface showed that the macrostructure of the metal of the experimental and ordinary ingots is the same. The work was attended by N.V Markina, senior lecturer at the Dept. of Machines and Foundry Technology, Volgograd State Technical University.

Mechanical properties of welded joints of the pressed aluminum-magnesium 1565Ch alloy at low and high temperatures

The paper studies structure and mechanical properties of welded joints of hot-pressed panels and profiles manufactured by JSC Arkonik SMZ from aluminum-magnesium 1565ch alloy at the temperature range of –165 to 150°C. It is established that the nature of changes in the properties of welded joints of pressed panels and profiles of 1565ch alloy made by manual argon-arc welding with non-consumable electrodes of ArDS with filler material SwAMg-61 at various test temperatures is similar to changes of welded joints of rolled sheets. When the test temperature is lowered, low-temperature hardening of the welded joints takes place – at a cryogenic temperature (–165°C), 20–30% of strength is gained comparing to 20°C. The prolonged aging of welded joints at an elevated temperature (150°C) leads to strength decrease by 25–30% compared to that of 20°C. The coefficient of strength of welded joints with reinforced joint is not less than 0.9 of the actual strength of the base metal at all test temperatures.

Preparation and Melting of Zr-1.0Nb Alloy

Zirconium alloys have many applications in industry in services too harsh for stainless steels, nickel alloys or where a noteworthy improvement in service life may be achieved, by choosing zirconium alloys instead of other metals, such as high permeability to thermal neutrons and excellent corrosion resistance in nuclear reactor environments. Mixing alloying elements, such as niobium, molybdenum, tin, titanium and tantalum, with zirconium changes its physical and chemical properties, especially its resistance to corrosion. In this study, specimens of Zr-1.0Nb alloy were obtained by melting in a furnace with non-consumable electrodes in argon atmosphere. Different samples were prepared to ensure good homogeneity of the specimens. The melting procedure was tested several times to determine the parameters that ensure proper alloy handling. These parameters include the melting point of the alloys under pressure and the current in the furnace. Using the derived melting parameters and processing parameters, it has been obtained Zr-1.0Nb alloy specimens with appropriate homogeneity, as confirmed by auxiliary characterization techniques, such as optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. For these methods, the requirements for physicochemical properties in the nuclear sector were incorporated into the analyses.

The Influence of the Current Density in the Open Welding Arc Active Spots on Cathode and Anode Voltage Breakdowns

Surfacing in gas-shielded as well as by the open arc burning between consumable electrodes, is usually made in reverse polarity. It is connected with the stable burning of arc and the minimum spatter of electrode metal. In this case, the cathode spot of the welding arc is on the plate, and the anode spot is on the wire end. These conditions of the arc spots existence affect the processes proceeding in the cathode and anode areas of the arc. The article considers the influence of the arc active spots formation conditions and its modes on the cathode and anode voltage breakdowns.