During the die-casting process as well as the hot forming process, the tool is subjected to complex thermal, mechanical, and chemical stresses that can cause various types of damage to different ...parts of the tool. This study was carried out to determine the resistance of various tool steels, i.e., UTOPMO1, HTCS-130, and W600, in molten Al99.7 aluminum alloy at a temperature of 700 °C. The formation kinetics of the interaction layer between the molten aluminum and tool steels was studied using differential scanning calorimetry. Light and field-emission scanning electron microscopy were used to analyze the thickness and nature of the interaction layers, while thermodynamic calculations using the Thermo-Calc software were used to explain the results. The stability of the HTCS-130 and W600 tool steels is better than the stability of the UTOPMO1 tool steel in the molten Al99.7 aluminum. Two interaction layers were formed, which in all cases indicate an intermetallic Al
Fe
layer near the aluminum alloy and an intermetallic Al
Fe
layer near the tool steels, containing small round carbides. It was confirmed that Ni reduces the activity of aluminum in the ferrite matrix and causes a reduction in the thickness of the intermetallic layer.
Benjamin Ipavec is deemed to be the key composer of Slovenian nationalistic movement in the 19th Century. But he also composed solo songs with piano accompaniment on German texts. He is typical ...representative of musical “biedermeier”. He attempted to achieve the synthesis of perfect form and profound emotional expression.
High pressure die casting is one of the leading casting processes in the modern industry. In the case of high pressure die casting, the melt is in contact with the tool, whereas the chemical ...interaction between the tool, made of hot-work tool steel and the melt occur. In addition, mechanical and heat wear of the tools also occur. For high productivity high resistance to these factors is required. The interaction between molten aluminium alloys Al99.9, Al99.7 and AlSi12 and hot-work tool steel UTOPMO1 was investigated at various experimental temperatures, i.e. 670 °C and 700 °C, whereas the differential scanning calorimetry was used. Optical and scanning electron microscopy were used in order to analyse interaction layer. The result of the interaction is the growth of a reaction layer, which is formed from intermetallic phases from Al–Fe or Al–Fe–Si systems. Reaction layer varies regarding the aluminium alloy and the temperature, to which it is exposed, whereas it is composed of three or four different layers. The thickness of the interaction layer depends only from the temperature, but the number of different layers in the interaction layer depends from the type of the aluminium alloy.
The current article presents an advanced analysis of the properties of solid-wire electric contacts produced with ultrasonic welding and soldering. Soldering is generally used to join thin, solid ...copper wires to produce electrical contacts in small-volume production, as ultrasonic welding does not provide acceptable peel force and tensile strength due to the deformation and thinning of the wires. In this article, ultrasonic welding of thin, solid copper wires using a ring before and after a thermal shock test is discussed and compared with the standard soldering technique. The thermal shock test was carried out in the temperature range from -30 to 150 °C. Half of the samples, for both the joining techniques and the wires, were subjected to the thermal shock test; the other half were not. Investigations included electrical resistance tests, optical and SEM microscopy, XRD, microhardness measurements, peel tests, tensile tests, and fractographic analysis. The electrical resistance test, microscopy, microhardness measurements, and fracture examinations showed no differences between the thermal shock-exposed and the non-exposed samples with the same joining process. In mechanical tests, the ultrasonic joint demonstrated superior strength compared to the soldered joint.
The aim of this study was to evaluate the effect of austempering compared to quenching and low-temperature tempering on wear resistance of an as-cast medium carbon high-silicon steel intended for ...rock breaking. Austempering was done by isothermal holding at 270, 300 and 350 °C in molten salt baths, while quenching was done in water. The austempering treatments resulted in microstructural combinations of bainite and martensite. The isothermal holding at 270 °C resulted in bainite and self-tempered martensite, while isothermal holdings at 300 and 350 °C resulted in bainite and untempered martensite. The two quench and temper treatments resulted in tempered martensite. In general austempering resulted in lower hardness values when compared to quenching and tempering but higher impact toughness. The wear resistance was best for quenching and low temperature tempering, followed by austempering at 270 °C, but at slightly lower hardness and 25% higher impact toughness. The other two austempering treatments resulted in worse wear resistance.
Seventeen new experimental filler metals from eight different alloy systems based on Fe–P–X and Mn–Fe–P–X (X = B, C, Si in various combinations) were created and experimented with. DSC analyses were ...performed to determine the solidus and liquidus temperatures and the melting ranges. Hardness measurements of the alloys were performed in the as-cast state. The alloys contain primary and eutectic intermetallic compounds that make them very hard with average hardness values ranging from 590 HV10 to 876 HV10. The wettability was determined at 1000 °C, 1040 °C and 1080 °C on C22 non-alloy steel and 15CrNiS6 low-alloy steel in Ar 4.6 and 78 vol% H2-22 vol% N2 atmospheres. The results show good wettability at T = 1080 °C in both atmospheres, as the contact angles were mostly ≤30°. Thirteen alloys exhibit very good wettability with average contact angles of ≤15.5°. Nine alloys exhibit excellent wettability with their average contact angles being ≤10°. Wettability improves at higher temperatures. The liquid alloys are reactive to solid steels and form a diffusion joint. Diffusion of P, B, C, and Si from the filler metal into the base material dealloys the composition of the melt near the joint interface. For the same reason, a continuous layer of solid solution forms on the joint interface. When brazing with filler metals rich in carbon, strong carburisation of steels can be observed near the joint.
The precise determination of the admixing rate of the base material for certain welding parameters is very important because of the possible negative consequences. As such, it is the basis for ...corrections in welding technology. In the article, experimental and theoretical determinations of the admixing rate in single-bead surface welds that were arc welded onto S355 steel with different alloyed-steel-coated electrodes are discussed. The admixing rate was experimentally estimated from the ratio of the surface areas of metallographic cross-sections, from the ratios of the height and from chemical analyses of different regions of the surface weld, while it was theoretically estimated from the characteristics of the welding process and material constants. One of the key characteristics of the welding process is the melting efficiency, which can be estimated by means of different equations and from knowledge of the heat balance of the welding process. Both the average melting efficiency of the surface welding on the medium-thick S355 steel plate and the average admixing rate of the S355 steel into the surface welds have the same value, i.e., approximately 30%. New equations for estimating the melting efficiency of the arc welding with a coated electrode were developed on the basis of the results.
Article is a reflection upon f. Hugolin Sattner’s cantata “Ode to Soča”, which was created in the time of First World War and great battles of Isonzo. It outlines composer’s ideological, political ...and aesthetic outlook as a basis for his creativity thus applying methods of history of mentalities.
A destructive pressure test of styrene-acrylonitrile (SAN) water-filter housings showed the influence of the shape and specific details of the housings on their critical areas and their destructive ...pressure. The destructive pressure varies by as much as 37 bar due to different dominant stresses in the individual types of housings. In critical areas of the housings, geometrical stress concentrators generally exist. For this reason, the stress caused by the internal pressure is locally 2.75-3.4 times greater than that expected based on the water pressure, which means that cracks are initiated in these places. However, the bottom of the housings can be in a form such that the maximum stress and the crack originates in its central part without the influence of local stress concentrators. The tensile strength of the SAN is theoretically estimated at 73 N/mm
, which is comparable with the literature data. The fracture toughness of the SAN is typically low, theoretically estimated in the range 1.45-3.55 MPa·m
, and strongly depends on the degree of the wall's stress-increasing rate or the crack-propagation rate. Therefore, at various crack-propagation rates, the critical crack depths are also different, in the range 100-600 μm. Due to this, the critical thickness for brittle fracture in the SAN is also different; it is ten times greater than the critical crack length. The characteristic of a sub-critical crack, i.e., the mirror zone, is its macroscopically smooth surface, which is microscopically very finely roughened. In the case of a sufficiently slowly growing sub-critical crack, the surface of the mirror zone contains characteristic parabolic markings. The over-critical, sufficiently rapidly growing cracks generally grow mainly in the plane-strain state and only the final thin layer of the remaining wall thickness breaks in the plane-stress state. The over-critical, sufficiently slowly growing cracks grow in the plane-stress state with a strong shear plastic tearing.
Fatigue cracks were initiated during the operation of a water-filter housing made from styrene-acrylonitrile (SAN). Using a destructive pressure test, it was confirmed that the sharp transition ...between the wall and the vertical external ribs of the filter housing at the point of the increased external diameter is the critical area of the water-filter housing. This is a consequence of the stress concentration due to the combined action of the sharp edges of the vertical external ribs and the increased stiffness due to the thicker wall and the mounting of the upper part of the housing onto the filter head. During the destructive pressure tests a crack was initiated on the external surface in the same place and spread in the same direction as the fatigue crack during the operation of the water filter. At the critical point the actual loads due to the stress concentrator are approximately 3.2 times higher than that expected based on the water pressure in the pipeline. The tensile strength of the styrene-acrylonitrile from the water-filter housing was comparable with the literature data. The fracture toughness of styrene-acrylonitrile is low and comparable to the fracture toughness of polymethylmethacrylate. The critical crack depth for the occurrence of an uncontrolled rupture for a continuously increasing load is approximately 100μm, while the plane-strain condition occurs at a thickness of about 1mm. A rapidly growing crack in the wall tends to grow in a layer of plane-strain conditions, and from the internal- to the external-wall surface. The possibility of determining the fracture toughness with a destructive pressure test of the housing or a pressure vessel with an external surface stress concentrator was achieved.
•The crack initiated in the high stress concentrator area•The critical crack depth of an uncontrolled rupture is approximately 100μm•The plane strain condition in SAN occurs at the wall thickness of approximately 1mm•The fracture toughness of SAN is low and is estimated to be 1,1-1,6MPam1/2
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