Interactions under hydrostatic pressure of a mild steel with liquid aluminium alloys

Interactions of a mild steel with liquid aluminium alloys have been studied in a pressure range of 0.1 to 350 MPa, and a temperature range from solidus to 750 °C, close to the squeeze casting process conditions. After having carried out the synthesis of previous surveys at atmospheric pressure, the influence of dipping parameters, and especially pressure, along with alloying elements on the intermetallic layer formation and on the mechanical strength of samples have been considered. These results must contribute to the improvement of the processing of steel reinforced aluminium matrix composites by squeeze casting process.     

Synthesis of high-speed tool steel surfaces on mild steel

Wear-resistant, hard surfaces of high-speed tool steel were synthesized on mild steel specimens. Discs of mild steel were subjected to carburization to a depth of 2.5 mm. Thin strips of tungsten were spot welded and the specimen was subjected to electron beam surface melting. The beam power was varied from 60 kV, 10 mA to 60 kV, 20 mA. Oscillation frequency and the specimen translation velocity were kept at 1000 Hz and 2 cm s-1, respectively. The width of the modified layer was 10 mm while the depth varied from 0.7–2.3 mm. A concentration of up to 30 wt% tungsten could be achieved in the surface layer by varying the thickness of the foil spot welded prior to electron-beam melting. Tungsten concentration was uniform along the depth. The hardness achieved in the as-solidified layer was uniform along the depth and reached 800 Hv. The reprocessing of the alloyed layer with the beam promoted fine carbide precipitation which then resulted in refinement of martensite plates.     

Studies on boronising of mild steel

Mild steel was boronised using a pack-cementation process. The pack contained boron carbide as boron source and ammonium bifluoride as activator. The effect of process variables like temperature and pack composition on the phase formation at the surface was studied. Depending on the experimental conditions either two-phase (Fe₂B + FeB) or singlephase coatings are produced on the surface. In the former case the high boron containing phase, FeB forms as a continuous layer over Fe₂B. Preferred orientation of the Fe₂B layer is observed on the steel surface to a thickness of ≈ 100 μm, above which random orientation is observed.     

An investigation of the kinetics of the dissolution of metals in liquid metals by a rotating-disc method (Coefficient of diffusion of iron in liquid aluminum)

It was shown that the Levich equation can be used in the determination of the coefficients of diffusion of impurities in liquid metals when the dissolution is complicated due to the growth of protective intermetallic layers. The cause of wide (10–20-fold) discrepancies in previously published data on the coefficient of diffusion of iron in liquid aluminum was elucidated. It was shown that the dissolution of iron in liquid aluminum takes place by a mixed mechanism.     

Wear resistance of plasma coatings on mild steel

Mild steel was coated by different materials using plasma spray technique. Materials used as coatings are Ni-5% Al and WC-17% Co. The thickness of the coatings varied between 0.05 to 1.5 mm. The porosity of different coatings decreased with increase in thickness of the coat. The roughness of coating material decreased after wear testing. Microstrueture study has been conducted for coatings of different materials before and after wear testing. Wear tests have been conducted under different aqueous environments at room temperature. The wear resistance of Ni-5% Al coating was improved by heat treatment. X-ray diffractometry showed the presence of NiO in the outer layer of the Ni-5% Al coating. The thickness of the coating, type of coating, heat treatment conditions, and the environment of testing proved to affect the rate of wear resistance.     

Formation of stainless steel layer on mild steel by welding arc cladding

The discrete microstructural characterization and the formation of stainless steel layer on mild steel where produced in cladding deposits, and fusion boundary region were investigated using tungsten inert gas (TIG) arc, high current pulsed arc and constricted plasma arc. The experimental procedure involved making bead-on-plate method for controlled travel speed, employing filler metal by using tungsten inert gas arc, pulsed current gas tungsten arc and transferred plasma arc, with subsequent sectioning and examination of the reaction interface. For TIG arc cladding, using filler metal of small diameter the deposit does not become stainless steel, but on using 3.2 mm diameter filler metal it becomes stainless steel with less than 50% dilution. For pulsed arc cladding, the complete stainless steel is not obtained on account of the existence of an incomplete mixture, particularly at the fusion boundary region. However, on using a large diameter filler metal at a pulse frequency of 500 Hz, the complete stainless steel microstructure has been accomplished. The plasma arc cladding can be achieved in such a way that the conversion into stainless steel on the mild steel surface — which is the microstructures of cellular austenite in cladding deposit and cellular dendritic austenite containing δ or σ-phase in fusion boundary region — is possible irrespective of the melt penetration and the dilution. The following conditions were found to be beneficial for the formation of stainless steel microstructure layer on the mild steel: using large diameter filler metal, below 50% dilution, and further rendering arc localized and constricted.     

Effect of liquid low-melting metals on the fatigue strength of carbon steel in relation to the stress frequency

It was established that the increase in the endurance of steel under the influence of molten metals is larger in the case of specimens with stress raisers. On the other hand, increasing the stress frequency produces a reduction in the endurance of steel in molten metals.     

Cleavage fracture in mild steel

Brittle fracture of steel structures has been a matter of considerable concern to both engineers and metallurgists for many years, it now being generally recognized that the cleavage mode of failure occupies a central position with respect to the problem. The paper reviews experimental evidence pertaining to the cleavage process in mild steel, particular attention being given to very recent work on the effect of second phase particles. A physical model of the process is thereby constructed, and in so doing, previous theories are critically examined and extended or modified where appropriate.

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Zusammenfassung Seit vielen Jahren hat der bei Stahlkonstruktionen vorkommende spröde Bruch den sich dzmit befassenden Technikern und Metallurgen erhebliche Sorgen gemacht, indem jetzt allgemein anerkannt ist, dass die mit Trennbrueh bezeichnete Bruchart in dieser Hinsicht eine Schlfsselstellung hat. Die Arbeit bring eine Zusammenfassung der aus Versuchen gewonnenen Ergebrdsse beziiglich des Trennvorganges in Flussstahl; ausserdem wird, den neuesten Erkenntnissen über den Einfluss von Teilchen der zweiten Phase besondere Aufmerksamkeit geschenkt. Dabei wird ein physikalisches Modell des Vorganges gebaut und gleichzeitig werden die bisherigen Theorien kritisch überpriift and erweitert oder gegebenenfalls abgeändert.[/p]

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Résumé Depuis plusieurs années la rupture grafile des structures en acier donne bien des soucis tant aux ingénieurs qu'aux metallurgists, en l'on admet maintenant plus ou moins-généralement que le mode de rupture par clivage tient fine position centrale dans ce problème. Dans cette note on passe en revue les données expérimentales relatives au processus de clivage dans l'acier doux, et l'on discute en plus de détail des travaux tout récents portant sur l'influence des particles de seconde phase. A partir de ces données on établit un modèle physique du processus et, cc faisant, on examine critiquement les theories antécédentes, en y apportant éventuellement des amplifications ou modifications appropriées.

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In this paper brittle has a general meaning and refers to a failure that occurs at a low applied stress level. For a notched component it implies that the failure occurs below the general yield stress, which is the applied stress at which a complete cross-section of the component is plastically deformed.     

Spreading of a horizontal layer of non-Newtonian liquid

The flow of a layer of non-Newtonian liquid in an open volume is investigated numerically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, Np, 6, pp, 950–957, June, 1985.     

Cyclic moment-curvature characteristics of mild steel

An experimental study of the moment-curvature behaviour of mild steel under essentially quasistatic cyclic loading is presented. A simple and efficient test rig which allows the testing to be extended into the strain hardening range was developed and is briefly described. In all, seventeen tests were conducted on rectangular mild steel sections to enable various features of the cyclic behaviour to be observed and highlighted. In particular, it was found that the main characteristics of the cyclic moment-curvature curves are predictable, and amenable to mathematical modelling.     

Electron beam synthesised hard layers on mild steel

Abstract

Hard surfaces have been synthesised on mild steel. The technique involves surface coating followed by electron beam mixing by melting. The coating comprised metallic or metalloid powders, graphite powder, and a water soluble binder. Modified surface layers of various dimensions were prepared by controlling electron beam processing parameters. Many carbide forming elements were investigated and boron and tungsten were found to be the most promising. The hardnes of the modified layers depended on the concentration of the alloying elements and varied between ~600 and 1000 HV(500 g). The technique is advantageous mainly because hard coatings can befabricated on almost any substrate that melts under an electron beam. Modified surfaces produced on mild steel are described in the present paper.

MST/2025     

Microstructure of plasma-sprayed Ni---Al alloy coating on mild steel

Microstructure and fracture surface morphologies were characterized for a cross-sectional plasma-sprayed Ni---Al alloy coating-mild steel substrate system by scanning electron microscopy, electronic probe microanalysis (EMPA) and transmission electron microscopy. The plasma-sprayed Ni---Al coating-steel substrate interface was found to be of pure metallurgical nature. The bonding layer consisting of Fe₃Al closely relates to exothermic reactions from Ni and Al during spraying. Ni₃Al, the product from the Ni---Al reaction, and Fe₃Al kept a fixed crystallographic orientation relationship. From the coating-substrate interface toward the coating surface, the fracture mode changes from preferential interlamellar fracture, to intersplat cleavage fracture, and finally to quasi-cleavage fracture. The changes are thought to be related to the contact condition between splats. Microstructural changes observed through the coating thickness seem to be caused by the non-uniform cooling rate distribution.     

The corrosive wear of nickel coating on mild steel

The abrasive wear of nickel coatings on steel substrates, under corrosive conditions was studied. For specimens with and without heat treatment, the wear rate was observed to depend upon the nature of the corrosive solution. The composition of the wear debris was noted to be a function of the corrosive wear conditions. The wear rate of the heat treated specimens was observed to be lower than that of the non-heat treated nickel-coated steel specimens.     

Centrifugation of liquid low-melting metals

Special purity grade metallic gallium in the melted state was centrifuged for the first time at various accelerations in the range from 1000g to 12000g. The crystallized metal exhibits a small change in the lattice period and a significant increase in the microhardness with increasing acceleration. The previously observed effects of the centrifugal acceleration upon the structure, composition, and properties of multicomponent systems are confirmed for the first time in a one-component liquid metal system (with point defects probably playing the role of the second component).     

Density of liquid alkali metals

With the aid of the thermodynamic similarity method generalized equations for the density of liquid alkali metals are obtained. Values of the density of liquid rubidium and cesium are calculated up to 600°C.