Tool steel

Abstract: Constitutive equations including an Arrhenius term have been commonly applied to steels with the objective of calculating hot rolling and forging forces. The function relating stress and strain rate is generally the hyperbolic-sine since the power and exponential laws lose linearity at high and low stresses, respectively. In austenitic steels, the equations have been used primarily for the peak stress (strain) associated with dynamic recrystallization (DRX) but also for the critical and steady state stresses (strains) for nucleation and first wave completion of DRX. Since the peak strain is raised by the presence of solutes and fine particles, the stress is raised more than by simple strain hardening increase, thus causing a marked rise in activation energy in alloy steels. In contrast, large carbides, inclusions or segregates, if hard, may lower the peak strain as a result of particle stimulated nucleation. Due to the linear relation between stress and strain at the peak, flow curves can be calculated from the constitutive data with only one additional constant. Maximum pass stresses can also be calculated from a sinh constitutive equation determined in multistage torsion simulations of rolling schedules. Comparison is made between carbon, micro-alloyed, tool and stainless steels and to ferritic steels which usually do not exhibit DRX. Parallels to the effects of impurities and dispersoids on the constitutive equations for Al alloys are briefly discussed.

Abstract: Selective laser melting (SLM) is a powder-based additive manufacturing capable to produce parts layer- by-layer from a 3D CAD model. Currently there is a growing interest in industry for applying this technology for generating objects with high geometrical complexity. To introduce SLM process into indus- try for manufacturing real components, high mechanical properties of final product must be achieved. Properties of manufactured parts depend strongly on each single laser-melted track and each single layer. In this study, effects of the processing parameters such as scanning speed and laser power on single tracks formation are explored. Experiments are carried out at laser power densities (0.3-1.3) × 10 6 W/cm 2 by cw Yb-fiber laser. Optimal ratio between laser power and scanning speed (technological processing map) for 50m layer thickness is determined for stainless steels (SS) grade 316L (−25m) and 904L (−16m), tool steel H13 (−25m), copper alloy CuNi10 (−25m) and superalloy Inconel 625 (−16m) powders. A considerable negative correlation is found between the thermal conductivity of bulk material and the range of optimal scanning speed for the continuous single track sintering. © 2010 Elsevier B.V. All rights reserved.

Abstract: Electric discharge machining (EDM), a ‘non-traditional machining process’, has been replacing drilling, milling, grinding and other traditional machining operations and is now a well-established machining option in many manufacturing industries throughout the world. Modern ED machinery is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, etc. This paper reports the results of an experimental investigation carried out to study the effects of machining parameters such as pulsed current on material removal rate, diameteral overcut, electrode wear, and surface roughness in electric discharge machining of En-31 tool steel (IS designation: T105 Cr 1 Mn 60) hardened and tempered to 55 HRc. The work material was ED machined with copper, copper tungsten, brass and aluminium electrodes by varying the pulsed current at reverse polarity. Investigations indicate that the output parameters of EDM increase with the increase in pulsed current and the best machining rates are achieved with copper and aluminium electrodes.

Abstract: The construction of mechanism maps for hot-isostatic pressing is described. Maps are constructed for a number of materials of commercial and scientific interest: a tool steel, a superalloy, Al2O3, and ice. They allow the processes involved in hot-isostatic pressing to be examined, and suggest ways of picking optimum combinations of pressure, temperature, and time to give maximum density.

Abstract: A test methodology is described which permits a rotating sphere test, also used to measure coating thickness, to be used as a small-scale abrasive wear test. The ability of the test to measure intrinsic wear resistance for thin coatings is demonstrated together with a new method of analysis which allows simultaneous evaluation of the wear resistance of both substrate and coating from their combined wear behaviour in a single test. The method has been applied to physically vapour deposited TiN, TiCN and TiAlN coatings on tool steel substrates, as well as to bulk samples of metals, ceramics and soda-lime glass.