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S. Topolska and J. Łabanowski

Abstract

The paper describes structure and properties of dissimilar stainless steels welded joints between duplex 2205 and austenitic 316L steels. Investigations were focused on environmentally assisted cracking of welded joints. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement was determined in slow strain rate tests (SSRT) with the strain rate of 2.2 × 10−6 s−1. Chloride-inducted SCC was determined in the 35% boiling water solution of MgCl2 environment at 125°C. Hydrogen assisted SCC tests were performed in synthetic sea water under cathodic polarization condition. It was shown that place of the lowest resistance to chloride stress corrosion cracking is heat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of HAZ comprising of large fractions of ferrite grains with acicular austenite phase. Hydrogen assisted SCC tests showed significant reduction in ductility of duplex 2205 steel while austenitic 316L steel remains almost immune to degradation processes. SSR tests of dissimilar welded joints revealed a fracture in the area of austenitic steel.

Open access

J. Przondziono, E. Hadasik and J. Szala

Abstract

The purpose of performed tests was evaluation of resistance to electrochemical corrosion of extruded magnesium alloy AZ31 with additive of 4.5% Li. Corrosion tests were performed in 0.01-2.0 M NaCl solutions. Potentiodynamic tests enabled to register polarisation curves. With application of stereoscopic microscope Nikon SMZ745T and electron scanning microscope Hitachi S-4200, the surface of the alloy was observed after immersion tests performed in 1-6 days. Results of performed tests prove explicitly deterioration of corrosion properties of the alloy with the increase of molar concentration of NaCl solution. It can be seen that corrosion process is intensive and that intensity increases with the increase of solution concentration and extension of exposure time.

Open access

P. Skubisz and A. Łukaszek-Sołek

Abstract

Results of investigation of the effect of processing conditions of medium-carbon alloy steel AISI 300M on forgeability and microstructure-properties are presented here, including as-forged and heat treated condition of the material. The presented results concern two vital aspects of plastic forming of high-duty impression-die forgings, which underlay a selection of technological conditions which enable the accomplishment of the required quality of the forged part. These are: firstly, the microstructure and mechanical properties and their uniformity within a part and secondly, technological realization of forging the required geometry in the given processing conditions.

In order to define a favourable processing window, dynamic behaviour modeling in variable forging conditions was carried out, establishing a coefficient of energy dissipation η% and the metal flow instability areas, which indicated the temperature regime and strain rate range for the forging process. The constructed processing maps were subject to experimental verification in the die-forging tests, carried out on a screw press. Hot and warm forging conditions were applied accordingly to selected areas of the processing maps, representative for unique forging conditions occurring in the industrial practice.

Open access

R. Pastirčák and J. Ščury

Abstract

This paper deals with influencing the crystallisation of Al alloys by a direct squeeze casting method. The effects of changed cooling rates of the casting is evaluated using a heat transfer coefficient at different casting conditions. The experimental results obtained by temperature measurement of the casting and the mould were used to predict the casting and mould surface temperatures using regression curves. The measured temperatures in the sub-surface layers were used to determine the amount of heat transferred from the casting to the mould. The amount of transferred heat increased 20-fold due to the effect of pressure. We also evaluated the effect of the acting pressure on the mechanical properties and microstructure of the alloy used. The process parameters were varied in the experiment.

Open access

M. Tenerowicz and M. Sułowski

Abstract

The aim of the study was to examine how a reduction of Mn content in PM steels will affect their plastic and strength properties. The results of mechanical, metallographic and fractography tests of sintered (PM) steels containing 1% and 2% Mn are reported and compared with those for 3% Mn PM steel. Höganäs iron powder grade NC 100.24, low-carbon ferromanganese Elkem and graphite powder grade C-UF were used as the starting powders. Powder mixes Fe-(1-2)%Mn-0.8%C were prepared in a Turbula mixer for 30 minutes. Following mixing, “dog bone” compacts were single pressed at 660 MPa, according to PN-EN ISO 2740 standard. Sintering of compacts was carried out in a laboratory tube furnace at 1120°C and 1250°C for 60 minutes in a mixture of 95%N2 – 5%H2 in a semi-closed container. Three types of heat treatment were then used: sinterhardening (cooling rate – 66°C/min), slow furnace cooling (cooling rate 3.5°C/min) and tempering at 200°C. The studies have shown a beneficial effect of the reduction of manganese on plastic properties (up to 7.96%), while maintaining fracture strengths (UTSs) comparable to those of steel with higher contents of manganese. Currently detailed studies of steel containing 1%Mn are conducted.

Open access

A. Mamala, P. Kwaśniewski, A. Nowak, J. Grzebinoga, W. Ściężor and R. Kowal

Abstract

The most recent and promising trends in development of renewable sources of energy are Combined Heat and Power (CHP) systems. The newest solutions from this field are hybrid compact solar panels. The correct operation of both systems, i.e. the photovoltaic panel and the heat exchanger requires an effective connection between the two. The adhesives utilized to interconnect above elements should provide a stable and hermetic joint able to withstand mechanical and thermal impacts of the surrounding environment factors. The paper presents the research results over the impact of the type and the amount of reinforcing phase on the physical and mechanical properties of epoxy resin matrix composites reinforced with particles of non-ferrous metals (Ag, Cu, W, Al), dedicated as adhesives for connections between photovoltaic panels and heat exchangers. Based on the experimental findings the usefulness of classical analytic models for valuation of polymer-metal composites properties was validated.

Open access

C. Rapiejko, B. Pisarek and T. Pacyniak

Abstract

The work presents the results of the investigations of the effect of intensive cooling of alloy AZ91 with an addition of chromium on the microstructure and mechanical properties of the obtained casts. The experimental castings were made in ceramic moulds preliminarily heated to 180°C, into which alloy AZ91 with the addition was poured. Within the implementation of the research, a comparison was made of the microstructure and mechanical properties of the castings obtained in ceramic moulds cooled at room temperature and the ones intensively cooled in a cooling liquid. The kinetics and dynamics as well as the thermal effects recorded by the TDA method were compared. Metallographic tests were performed with the use of an optical microscope and the strength properties of the obtained castings were examined: UTS (Rm), elongation (A%), and HB hardness.

Open access

S. Parzych

Abstract

This work deals with the effect of heat treatment on a microstructure and mechanical properties of a selected cast steel assigned as a material used for frogs in railway crossovers. Materials used nowadays in the railway industry for frogs e.g. Hadfield cast steel (GX120Mn13) or wrougth pearlitic steel (eg. R260) do not fulfil all exploitation requirements indicated in the UIC (International Union of Railways) Decision No. 1692/96 in terms of train speed that should be reached on railways. One of the possible solution is using a cast steel with bainitic or bainitic-martensitic microstructure that allows to gain high strength properties the ultimate tensile strength (UTS) of 1400 MPa, the tensile yield strength (TYS) of 900 MPa and the hardness of up to 400 BHN. The tested material is considered as an alternative to Hadfield cast steel that is currently used for railway frogs.

Results of an experimental analysis of the effect of conducted heat treatment on a microstructure, the volume fraction of retained austenite and mechanical properties of bainitic steel, are shown in this paper. It was found that, the heat treatment leads to a stabilization of retained austenite in grain boundaries area of the primary austenite. Additionally, the heat treatment according to the variant #3 results with an almost 3-times higher impact toughness to that exhibited by material subjected to the other treatments.

Open access

D. Kopyciński, D. Siekaniec, A. Szczęsny, E. Guzik and A. Nowak

Abstract

The results of studies of the effect of different amounts of the Fe-Ti inoculant on structure and selected mechanical properties of High Chromium Cast Iron (conventionally abbreviated as HCCI) are presented. The main purpose of the inoculation is structure refinement and hence the improvement of casting properties. Generally considered a strong carbide-forming element, titanium is an effective inoculant for the high chromium cast iron. However, there is an optimal amount of titanium addition beyond which the mechanical properties begin to deteriorate. The studies enabled determining the amount of Fe-Ti inoculant optimal for the cast iron of a given chemical composition.

Open access

B. Garbarz, M. Adamczyk and B. Niżnik-Harańczyk

Abstract

The aim of this work was to develop basic parameters of hot rolling and controlled cooling technology allowing to obtain the microlaminated (lamellar) microstructure in a lean-alloy structural steel containing 3÷5 wt % Al. Thermo-mechanical rolling tests of two experimental steels were carried out in a semi-industrial line comprising a one – stand reversing rolling mill. The final microstructure of the specimens subjected to rolling in the γ + α stability region characterised with the microlaminated morphology composed of lamellae of ferrite with thickness down to 1 μm or less and lamellae or grains of phases developed during transformation of the austenite. Determined parameters of the thermo-mechanical processing allowed to achieve very attractive mechanical properties of the experimental steels: tensile strength over 1.0 GPa and ductility level (total elongation) better than 15%.