Showing papers in "Metals technology in 1981"
TL;DR: In this paper, microstructural changes around non-metallic inclusions were studied using both optical and transmission electron microscopy, showing that large numbers of cyclic stresses cause the parent tempered martensite to disappear, along with the spherical cementite particles generally found in these through-hardened steels.
Abstract: Microstructural changes around non-metallic inclusions (sometimes called ‘butterflies') were studied using both optical and transmission electron microscopy. Large numbers of cyclic stresses cause the parent tempered martensite to disappear, along with the spherical cementite particles generally found in these through-hardened steels. The microstructural changes are described and the transformation products identified. Also, comparisons are made with similar events around crack tips, and a formation mechanism is proposed.
121 citations
TL;DR: In this article, a commercial low-alloy steel exhibiting combinations of mechanical properties superior to those of many other highly alloyed steels has been designed, which can be produced by isothermal heat treatment of high-carbon silicon-alloys, in the upper bainite temperature range.
Abstract: A commercial low-alloy steel exhibiting combinations of mechanical properties superior to those of many other highly alloyed steels has been designed. The good properties are achieved by a carbide-free bainitic–austenitic structure, which can be produced by isothermal heat treatment of high-carbon silicon-alloyed steels in the upper bainite temperature range. Structure–property relationships are evaluated in order to find the optimum combination of heat treatment and alloy content. The effective grain size, the austenite volume fraction, and the austenite morphology are important factors controlling the properties. The mechanical stability of the austenite is of little importance.
110 citations
TL;DR: In this paper, it was shown that mass transfer is important in the thermally activated process and that speed effects may be recognized in the mean equivalent strain rate and then combined with temperature eff...
Abstract: Extrusion is shown to be a thermally activated process in which mass transfer is important. Speed effects may be recognized in the mean equivalent strain rate and then combined with temperature eff...
45 citations
TL;DR: In this article, the effect on structure and properties of an Al-Mg-Mn alloy caused by varying the extrusion parameters over a wide range of temperature-compensated strain rate was investigated.
Abstract: The effect on structure and properties of an Al–Mg–Mn alloy caused by varying the extrusion parameters over a wide range of temperature-compensated strain rate was investigated. It was determined that subgrains exist in the extrudate structure under all processing conditions, but the structure contained recrystallized grains if the extrusion temperature was above 673K. Although the subgrain size varied linearly with temperature-compensated strain rate the properties did not. It was not possible to determine a simple relationship between properties and the temperature-compensated strain rate, but it was found that they do vary considerably with processing conditions and appear to be strain dependent.
33 citations
TL;DR: In this article, a mathematical model was used to calculate the internal stresses and strains generated during the quenching of infinite plates of a steel of high hardenability in water, oil, or a polymer solution in water.
Abstract: A mathematical model has been used to calculate the internal stresses and strains generated during the quenching of infinite plates of a steel of high hardenability in water, oil, or a polymer solution in water. As a preliminary it was necessary to determine experimentally some of the required physical and mechanical property data: they included the mechanical properties of austenite at temperatures between Ms and 800°C, the relationship between specimen length and temperature during cooling, and the effect of surface temperature on the surface heat-transfer coefficient. The results of the calculation indicate that all three quenchants produce plastic flow, which is confined to temperatures above M s This flow gives rise to a complex residual-stress distribution which, in the case of the water or polymer quenchant, involves a maximum tensile stress just below the surface and a compressive stress towards the centre: the oil quench produces the reverse stress distribution. The predicted residual str...
31 citations
TL;DR: In this article, thermal fatigue properties have been investigated and compared in five standard hot-work tool-steel grades and one newly developed grade, based on a carefully balanced alloy composition, which is found to offer superior properties in these respects.
Abstract: Thermal-fatigue properties have been investigated and compared in five standard hot-work tool-steel grades and one newly developed grade. The results demonstrate that heat-checking resistance, hot yield strength, and temper resistance can differ considerably between different martensitic hot-work grades of rather similar alloy type. The very best resistance against thermal fatigue is obtained with alloys having the highest hot yield strength and temper resistance. The new grade, which is based on a carefully balanced alloy composition, is found to offer superior properties in these respects. The findings stress further the importance of selecting a proper tool material when dealing with high-temperature hot-working applications in which the tool is subjected to large thermal fluctuations.
30 citations
TL;DR: In this paper, the nature of deformation in the roll gap during passes in which plane-strain conditions do not obtain is investigated, and it is shown that plastic flow is complex, involving material transfer for material transfer.
Abstract: The nature of deformation in the roll gap during passes in which plane-strain conditions do not obtain is investigated, and it is shown that plastic flow is complex, involving material transfer fro...
23 citations
TL;DR: In this paper, a wider range of experiments has now shown that the conditions can vary between interfacial sliding and full sticking friction or seizure, and the physical differences between sliding and seizure are discussed in detail.
Abstract: This paper is concerned with the frictional interactions at the chip/tool interface in machining. Lead, aluminium, copper, iron, and nickel have been machined over a range of cutting speeds and times. Steel, cemented carbide, and transparent sapphire cutting tools have been used; the last allowing the interface to be observed directly. When used in this way in an earlier investigation it was found that relative motion, or sliding, occurred between chip and tool. However, a wider range of experiments has now shown that the conditions can vary between interfacial sliding and full sticking friction or seizure. The physical differences between sliding and seizure are discussed in detail. In the latter case the bond between chip and tool is sufficiently strong for relative motion to occur within the chip, and material is transferred to the tool face. When cutting aluminium with the sapphire tools, comparatively long cutting times and high speeds promote transfer. The key feature of such a process is th...
23 citations
TL;DR: In this article, the temperature dependence of the flow stress of the α+γ mixture of carbon steels has been measured and an observed flow-stress minimum in the temperature range of the mixture expands with decrea...
Abstract: The temperature dependence of the flow stress of the α+γ mixture ofplain carbon steels has been measured. An observed flow-stress minimum in the temperature range of the mixture expands with decrea...
21 citations
TL;DR: A range of aluminium-alloy components made by GKN Technology Ltd using this technique is shown, and details are given of the types of component geometry amenable to the process.
Abstract: The squeeze-forming process, involving the pressurized solidification of liquid metal in re-usable dies is described, and the importance of various process parameters is discussed. A range of aluminium-alloy components made by GKN Technology Ltd using this technique is shown, and details are given of the types of component geometry amenable to the process. Mechanical-property data determined in several of these components are presented for a number of aluminium alloys. It is observed that both ‘forging’ and ‘casting’ alloys can be successfully squeeze formed, and that the mechanical properties achieved compare favourably with conventional properties. It is concluded that the work performed at GKN Technology Ltd has confirmed squeeze forming to be a potentially powerful technique for the manufacture of a wide range of aluminium components in competition with more conventional production methods.
21 citations
TL;DR: In this article, the basis and current status of development of various approaches to the prediction of the combined creep-fatigue endurance are reviewed, and it is concluded that an inadequate materials data base...
Abstract: The basis and current status of development of the various approaches to the prediction of the combined creep–fatigue endurance are reviewed. It is concluded that an inadequate materials data base ...
TL;DR: A mathematical model of radial heat flow in billets during transfer, and after upsetting in the extrusion container, has been developed in this article, which makes a number of simplifying assumptions, which e...
Abstract: A mathematical model of radial heat flow in billets during transfer, and after upsetting in the extrusion container, has been developed. The model makes a number of simplifying assumptions, which e...
TL;DR: In this article, a tool steel has been studied for its superplastic characteristics for three different structures: (a) a coarse spheroidized-annealed structure; (b) a structure of fine spheroized cementite pa...
Abstract: A 01 tool steel has been studied for its superplastic characteristics for three different structures: (a) a coarse spheroidized-annealed structure; (b) a structure of fine spheroidized cementite pa...
TL;DR: Auger electron analyses have shown evidence that, during argon atomization and subsequent processing, a thin oxide film can form on the surfaces of powder particles of a nickel-based superalloy as mentioned in this paper.
Abstract: Auger electron analyses have produced evidence that, during argon atomization and subsequent processing, a thin oxide film can form on the surfaces of powder particles of a nickel-based superalloy....
TL;DR: In this paper, a simple mechanism is proposed to explain the effect of section size on life to rupture and the implications of the interpretation are discussed from the point of view of practical applications of thin sections in turbine components.
Abstract: Creep tests have been carried out at 750°C on sheet specimens of Nimonic 90 having thicknesses between 0·15 and 1·7mm and grain sizes in the range 0·04−0·07 mm, but mostly ∼0·05 mm. The results show that there is a significant decrease in creep performance when the thickness is less than about 1mm and that failure occurs as a result of grain-boundary cavitation, irrespective of section size. For specimen thicknesses of 0·28 and 1·7mm the stress dependence of the minimum creep rate was similar to that expected for bulk material, suggesting that diffusion creep was not responsible for the decrease in creep resistance of the thinner specimens. A simple mechanism is proposed to explain the effect of section size on life to rupture and the implications of the interpretation are discussed from the point of view of the practical applications of thin sections in turbine components.
TL;DR: In this paper, the effects of varying the annealing temperature and cooling rate on the strength, ductility, and microstructure of a plain carbon steel, and a similar steel containing 0·06%V, are reported.
Abstract: The effects of varying the annealing temperature and cooling rate on the strength, ductility, and microstructure of a plain carbonsteel, and a similar steel containing 0·06%V, are reported. The tra...
TL;DR: A chromium-containing corrosion-resisting steel, provisionally designated SX 3 CR 12 (Patent application SA 78/4764), has been developed from AISI 409 grade in the laboratories of Southern Cross St...
Abstract: A chromium-containing corrosion-resisting steel, provisionally designated SX 3 CR 12 (Patent application SA 78/4764), has been developed from AISI 409 grade in the laboratories of Southern Cross St...
TL;DR: In this article, five different martensitic hot-work tool-steel alloys, two new alloys and three already established ones, have been investigated and compared with respect to decisive material properties.
Abstract: Five different martensitic hot-work tool-steel alloys, two new alloys and three already established ones, have been investigated and compared with respect to decisive material properties. It is the...
TL;DR: In this article, a thin surface layer with a very fine-grained structure was found to not affect the bulk properties, except at very low finish-rolling temperatures, where there is a risk of tensile stresses occurring at the surface.
Abstract: To reduce the long processing time in the controlled rolling of plate in one-stand reversible rolling mills, water cooling can be used. Experiments in both a pilot plant and a production mill showed no significant change in bulk mechanical properties if heavy water cooling was used during the holding period, but a thin surface layer with a very fine-grained structure was found. This surface effect is not believed to affect the bulk properties, except at very low finish-rolling temperatures, where there is a risk of tensile stresses occurring at the surface. Water cooling can also be used during the roughing stage. This method gave an even shorter processing time and no surface effects, but the toughness deteriorated somewhat. Controlled rolling with water cooling during rolling is believed to be suitable when rolling short runs of many different products.
TL;DR: The metallurgical structure and strength of inter layered joints between a WC-6Co hardmetal and Co, Cu, Ni, mild steel, and tool steel have been studied in this paper.
Abstract: The metallurgical structure and strength of inter layered joints between a WC–6Co hardmetal and Co, Cu, Ni, mild steel, and tool steel, and between two WC–Ni hard metals and Ni have been studied fo...
TL;DR: In this paper, the shape control is used to adjust the mill so that the rolled strip is free from internal stresses, which is an area of current interest in the steel industry.
Abstract: The design of shape-control systems is an area of current interest in the steel industry. The object of shape control is to adjust the mill so that the rolled strip is free from internal stresses. ...
TL;DR: Vanadium has been used for several decades in many pipeline and other structural steels to provide a high strength by its effect of refining ferrite grain size and causing precipitation of carbonit as mentioned in this paper.
Abstract: Vanadium has been used for several decades in many pipeline and other structural steels to provide a high strength by its effect of refining ferrite grain size and causing precipitation of carbonit...
TL;DR: The axial fatigue properties of nitrided En41B steel specimens of differing diameters but with constant case depth have been studied as mentioned in this paper, and significant improvements in fatigue properties were observed after nitriding; close to the fatigue limit the greatest improvement occurred in larger (5 mm dia.) specimens, but the smallest specimens showed the greatest increase in fatigue strength at lives below 105 cycles.
Abstract: The axial fatigue properties of nitrided En41B steel specimens of differing diameters but with constant case depth have been studied. The tensile residual stress in the specimen core is increased as the case/core area ratio rises. No relaxation of these stresses was detected after stressing close to the fatigue limit, although at higher stress levels a 10% reduction was measured after 50% of the expected fatigue life. Significant improvements in fatigue properties were observed after nitriding; close to the fatigue limit the greatest improvement occurred in larger (5 mm dia.) specimens, but the smallest specimens (3 mm dia.) showed the greatest increase in fatigue strength at lives below 105 cycles. The mechanisms of failure were identified metallographically in each case; Yielding of the core occurs when the sum of the applied tensile stress and the axial core residual stress exceeds the yield stress of the non-nitrided material, and this leads to a redistribution of stresses between case and cor...
TL;DR: In this article, a cast-to-shape forging dies have been produced in a specially designed alloy employing a coarse dispersion of niobium carbide in a maraging steel matrix, the dispersion being developed in the melt.
Abstract: Cast-to-shape forging dies have been produced in a specially designed alloy employing a coarse dispersion of niobium carbide in a maraging steel matrix, the dispersion being developed in the melt. Effects ofcertain foundry conditions on the structure of the cast material are examined and the development of a technique for the casting ofa forging-die insert is described. The surface finish and quality of the castings were optimized by progressive refinement of the foundry technique, based on Shaw process investment moulding. The castings were assessed in respect of surface finish and the hardness and structural characteristics of the zone immediately beneath the critical surfaces. The surface region was shown to have an atypical microstructure offering no special advantage in terms of wear resistance. A pair of the cast inserts was fitted out and put into service for the manufacture of components in an industrial forge. The service life was found to be determined by eventual wear to an oversize con...
TL;DR: In this paper, an investigation was made into the effects of thermo mechanical processing on precipitation strengthening in high-strength low-alloy steels containing vanadium with low and high nitrogen conte...
Abstract: An investigation has been made into the effects of thermo mechanical processing on precipitation strengthening in high-strength low-alloy steels containing vanadium with low and high nitrogen conte...
TL;DR: In this article, the structural changes in a high-sulphur free-cutting steel and a lead-bearing HSC steel have been determined by compounding the results of tensile tests after cold rolling the steels for differing amounts up to 98% reduction.
Abstract: The overall property changes in a high-sulphur free-cutting steel and a lead-bearing high-sulphur free-cutting steel have been determined by compounding the results of tensile tests after cold rolling the steels for differing amounts up to 98% reduction. The structural changes have been determined by optical and thin-foil transmission electron metallography, while the tensile fractures found after cold rolling have been examined by scanning electron microscopy. The high-sulphur steel showed a lower work-hardening rate than the equivalent plain carbon steel at moderate strains, but at high strains a tensile strength of 1700 MN m−2 was obtained. The MnS particles were more plastic than the matrix (plasticity ratio >1) and a fibre-reinforcing effect could give rise to the high strength. For the lead-bearing steel the work-hardening rate was lower than with the lead-free steel. The lead caused the sulphides to fragment and, hence, the final strength level achieved was much lower, but still greater, t...
TL;DR: In this paper, surface and subsurface damage in hardened and tempered En 31 steel has been examined after grinding under various conditions, including downfeed, wheel speed, wheel hardness, and dressing spee...
Abstract: Surface and subsurface damage in hardened and tempered En 31 steel has been examined after grinding under various conditions. The effects of downfeed, wheel speed, wheel hardness, and dressing spee...
TL;DR: In this paper, the effects of hot-rolling parameters and aging on the microstructure and mechanical properties of a low-carbon Cu-Ni-er-P-Nb-Ti steel have been studied.
Abstract: The paper deals with the development of strong, tough steels with intrinsic corrosion resistance for structural applications in the Arctic, based on the auto-aging effects of copper and microduplex precipitation of carbides of niobium and titanium. The effects of hot-rolling parameters and aging on the microstructure and mechanical properties of a low-carbon Cu-Ni-er-P-Nb-Ti steel have been studied. Results indicate that: (i) the nature of the matrix has an important influence on the mechanical properties (the microstructures, in order of increasing strength, are ferrite, deformed ferrite, duplex structure, and bainite); (ii) the age-hardening response, in spite of three precipitation-hardening elements, is classical in nature with an activation energy of 163 kJ mol−1 ; (iii) there is considerable scope for developing weathering steels with strength levels in the range 850–1000 MN m−2 with low transition temperatures (−40° to −100°C) based on the precipitation strengthening of copper and combined ...
TL;DR: In this paper, the influence of microstructural directionality on machining behavior was examined for two commercial steel plates with respect to both ferrite-pearlite banding and inclusions, using orthogonal cutting tests.
Abstract: The influence of microstructural directionality on machining behaviour is examined for two commercial steel plates with respect to both ferrite-pearlite banding and inclusions, using orthogonal cutting tests. In relation to machining forces, chip morphology, and surface finish, one steel exhibited marked anisotropy, and comparisons with a non-banded steel indicated that the anisotropy was primarily due to the presence of ferrite-pearlite banding. Reasons for the anisotropy are briefly discussed in terms affracture energy, and the difficulties of machining in certain directions and relevance of the results to practical machining operations are also highlighted.