This article analyses the as-cast state of practically unknown Fe-P-based cast alloys with or without an addition of carbon and/or boron, cast into a grey cast iron mould. The melting intervals of ...the alloys were determined by DSC analysis, and the microstructure was characterized by optical and scanning electron microscopy with an EDXS detector. The hardness and microhardness of the alloys were also measured. Their hardness reached values between 52 and 65 HRC depending on chemical composition and microstructure, showing their high abrasion resistance. The high hardness is a consequence of the eutectic and primary intermetallic phases of Fe
P, Fe
C, Fe
B or mixed type. By increasing the concentration of metalloids and combining them, the hardness and brittleness of the alloys were increased. The alloys with predominantly eutectic microstructures were the least brittle. Depending on the chemical composition, the solidus and liquidus temperatures ranged from 954 °C to 1220 °C and were lower than those of the well-known wear-resistant white cast irons.
This article deals with an analysis of mixing and determines the admixing rate of a base S355 steel plate in single-bead surface welds by measuring the chemical composition using a plane-scan energy ...dispersive X-ray spectroscopy (EDXS) on metallographic cross-sections. The results show that obtaining a larger number of EDXS measurements does not necessarily lead to obtaining a more accurate admixing rate. Due to the ever-present segregations that are generally near the base material, the disadvantage of this method is the subjective influence of the SEM operator on the estimated admixing rate. To obtain relevant results, a sufficiently wide area of well-mixed melt, including segregations, must be analyzed. This study showed that by using a sufficiently large number of appropriately selected sites with a sufficiently large surface area, it is possible to estimate the admixing rate from the chemical composition with an accuracy of ≥96% for the geometrically determined admixing rate
= 30%. From several equations, the best result showed an equation which is the arithmetic mean of the two different arithmetic means and in which the artificial influencing factor of the segregations of the base material is taken into account. With this equation, the same value of admixing rate,
= 30%, was obtained using the comparative geometric method.
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.
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.
The non-alloyed hypo-eutectoid steel C45 was annealed in a steady air atmosphere at T > AC1 using three temperature ranges and annealing times ta = ½, 1 and 2 h. The oxidation and decarburization ...obeyed the parabolic law of growth with time and increased with higher temperatures and longer annealing times. The maximum visible thickness of the decarburized surface layer for all the temperature ranges can be predicted from the equations for the oxidation of iron and from the Van-Ostrand-Dewey equation (derived from Fick’s 2nd law) for the distribution of carbon. In this relation, the equation that gives the lowest values for the diffusion coefficient of carbon in austenite is appropriate. It was found that the Van-Ostrand-Dewey equation is applicable at T > AC1, despite the fact that it was derived for the decarburization of austenite at T > AG. A comparison of the results showed that the depth of the decarburization with a carbon content of 0.91–0.98C0 can be determined with optical metallography and that both the theoretical and measured values are, in general, mutually accurate in the regions of 93% to 98%. In practice, visible decarburization might not be present under some conditions while annealing in a steady air atmosphere. The reason for this is that the process of oxidation is faster than the process of decarburization. Considering the oxidation of steel under these conditions, annealing in a steady air atmosphere can be performed without any protective measures.
The paper deals with modelling of the shape and size of a crystal grain in a butt joint of ferritic high-alloy stainless steel made by TIG welding without the addition of filler material. The ...optimum, maximum, and minimum current intensities and welding speeds were experimentally determined. The welding speed is mathematically described as a function of the welding-current intensity. On the basis of macro specimens taken from three different directions with regard to the welding direction, the grain shape, size and location in the weld with regard to the welding direction were established. Individual characteristic crystal grains are shown in space. The average grain size was determined and described mathematically as a function of the welding parameters.
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
Fatigue cracks were found in water-filter housings made of styrene-acrylonitrile. These cracks initiated on the external surface, along the sharp corner between the wall of the housing and the ...vertical external ribs or at a pre-existing crack in the base of the water-filter housing. The reason for the crack was the high stress concentration due to an inappropriate design or the poor quality of the filter housing in combination with water-pressure impacts during the operation of an electromagnetic water valve and taps.
•Fatigue cracks exist in a water-filter housing made of styrene-acrylonitrile.•Quality of the styrene-acrylonitrile is good.•Cracks initiated due to water-pressure impacts in areas of high stress concentration.•Failure is due to improper design or a pre-existing crack in the base of the filter housing.
•The archaeometallurgical characterization of a 16th century suit of armour was performed.•The thickness of steel sheet was adapted deliberately to the protective requirements of the individual ...elements of the armour.•Variations in thickness across the armour are highly consistent with the intended function of the individual parts, demonstrating the great skill of the master armourer Valentin Siebenbürger.•The suit of armour was made from three different grades of steel.•Non-metallic inclusions are typical for steel made during the early modern period. This helped us detect a subsequent restoration.
This paper presents a detailed analyses of a 16th century suit of armour made by Valentin Siebenbürger, one of the most skilled and talented German armour makers of the period. The studied harness is kept at the National Museum of Slovenia. Our research focused on evaluating the individual parts of the armour in terms of protection, workmanship precision, quality, the composition of the steel used and authenticity. By accurately measuring the thickness of the individual parts of the armour, a clear distinction may be seen between the sections protecting the vital areas of the body and those covering the extremities. Furthermore, the measurements clearly indicate the level of manufacturing precision achieved in Siebenbürger's workshop, as well as the relative importance of various elements in terms of their protective qualities. Apart from thickness measurements, metallographic and radiographic analyses were also performed. The results indicated that the suit of armour was made from three different types of steel: pure carbon steel, steel containing manganese, steel containing cobalt.
Because the visor was made from pure carbon steel without major non-metallic inclusions, it may be concluded that it was added at a later date during restoration. The exceptionally even, uniform shaping and tapering of sheet thickness observed during the measurements indicates a high level of mastery in the forging of steel sheet.
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