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Abstract

This research paper shows the influence of a repeated SPD (Severe Plastic Deformation) plastic forming with the DRECE technique (Dual Rolls Equal Channel Extrusion) on hardening of low carbon IF steel. The influence of number of passes through the device on change of mechanical properties, such as tensile strength TS and yield stress YS, of tested steel was tested. The developed method is based on equal channel extrusion with dual rolls and uses a repeated plastic forming to refinement of structure and improve mechanical properties of metal bands [1-2]. For the tested steel the increase of strength properties after the DRECE process was confirmed after the first pass in relation to the initial material. The biggest strain hardening is observed after the fourth pass.
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Abstract

Cast high-manganese Hadfield steel is commonly used for machine components operating under dynamic load conditions. Their high fracture toughness and abrasive wear resistance is the result of an austenitic structure, which - while being ductile - at the same time tends to surface harden under the effect of cold work. Absence of dynamic loads (e.g. in the case of sand abrasion) causes rapid and premature wear of parts. In order to improve the abrasive wear resistance of cast high-manganese steel for operation under the conditions free from dynamic loads, primary titanium carbides are produced in this cast steel during melting process to obtain in castings, after melt solidification, the microstructure consisting of an austenitic matrix and primary carbides uniformly distributed therein. After heat treatment, the microhardness of the austenitic matrix of such cast steel is up to 580 μHV20 and the resulting carbides may reach even 4000 μHV20. The impact strength of this cast steel varies from 57 to 129 and it decreases with titanium content. Compared to common cast Hadfield steel, the abrasive wear resistance determined in Miller test is at least twice as high for the 0.4% Ti alloy and continues growing with titanium content.
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Abstract

The paper deals with the properties and microstructure of Reactive Powder Concrete (RPC), which was developed at Cracow University of Technology. The influence of three different curing conditions: water (W), steam (S) and autoclave (A) and also steel fibres content on selected properties of RPC was analyzed. The composite characterized by w/s ratio equal to 0.20 and silica fume to cement ratio 20%, depending on curing conditions and fibres content, obtained compressive strength was in the range from 200 to 315 MPa, while modulus of elasticity determined during compression was about 50 GPa. During three-point bending test load-deflection curves were registered. Base on aforementioned measurements following parameters were calculated: flexural strength, stress at limit of proportionality (LOP), stress at modulus of rapture (MOR), work of fracture (WF), and toughness indices I₅, I₁₀ and I₂₀. Both amount of steel fibres and curing conditions influence the deflection of RPC during bending.
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