Gogaev and V. I. Ul'shin UDC 621.762Optimum temperatures for deforming powder tool steels are determined. It is established that the ductility limit during deformation of these steels in the dynamic recrystallization temperature region is higher than that at 1100-1150°C. Jet moulding technology followed by deformation in the temperature range established is shown to be promising.Tool steels are most in demand in enterprises of various branches of industry as a material for cutting tools and measuring instruments, and forging equipment. A considerable increase in the quality of tool steels due a sharp increase in the dispersion of carbides and their uniform distribution within the volume of the metal has been achieved due to the use of powder metallurgy technology.The main industrial process for preparing graded metal made from powder tool steels, in particular high-speed steels, is the ASIA-STORA process [1]. It includes the following operations: preparation of powder by atomizing molten metal with an inert gas, loading the powder into capsules, evacuating and sealing the powder, hydro-and gasostatic treatment of capsules with the powder, forging the capsules in forging presses, and rolling graded metal. For low-series production of tool steels made from high-speed steels the authors in [2] have developed technology for preparing powder billets without using capsules and binders. The main operations for this technology are preparing powder by atomizing molten metal with gas, vacuum annealing, cold powder compaction, vacuum sintering of the powder billet, and hot extrusion.Recently in the technologically developed countries of the world new production technology has been developed and introduced for preparing powder billets of a prescribed shape by jet moulding [3]. Jet moulding (OSPREY-process) combines gas atomizing of molten metal and deposition of liquid droplets on a substrate (solidifier) where a billet with a density of 96-98% is formed from the droplets in the liquid, solid-liquid, and solid states. This makes it possible to heat a billet for subsequent deformation in furnaces without a protective atmosphere. The high cooling rate (10 3 -10 5 deg/sec) during solidification provides formation of a highly dispersed structure with uniaxial grains and uniformly distributed carbides.Jet moulding of powder billets made from alloy steels is more economic than the traditional powder metallurgy technology. Compared with the processes described in [1, 2] jet moulding excludes a whole series energy-consuming operations such as vacuum annealing, cold compaction, and vacuum sintering. After jet moulding billets are compacted by means of hot plastic deformation (rolling, forging, extrusion).It is very important in metal forming to have a specific deformation temperature range. For powder tool steels the temperature range for deformation is normally 900-1200°C, i.e. it is the same as for steels of the traditional production method (melting, pouring into an ingot, and preparation of graded metal by forming). Due to the di...
A method for producing strips by titanium powder rolling is proposed. The effect from powder annealing on the porosity of the initial billet is analyzed. The optimal temperatures of sintering and annealing after intermediate rolling are determined. It is shown that, under the optimal deformation conditions, the strip has mechanical properties that compare well with those of strips produced conventionally.
Показано, що структура загартованої сталі 40Х3Н5М3Ф при нагріванні від кімнатної температури до температури експлуатації (800С) змінюється: мартенситна структура перетворюється на аустенітну. Залежність кількости аустеніту від температури близька до експоненційної. Підтверджено, що в інтервалі температур експлуатації (750-800С) дослідна сталь має аустенітну структуру з невеликою кількістю карбідної складової (1,55-1,68%). Ключові слова: сталь, термічне оброблення, структура, твердість. Показано, что структура закалённой стали 40Х3Н5М3Ф при нагреве от комнатной температуры до температуры эксплуатации (800С) изменяется: мартенситная структура превращается в аустенитную. Зависимость количества аустенита от температуры близка к экспоненциальной. Подтверждено, что в интервале температур эксплуатации (750-800С) исследованная сталь имеет аустенитную структуру с небольшим количеством карбидной составляющей (1,55-1,68%).
It is shown, using electron microscopy, magnetic and friction methods, that a mixture of magnetic g-Fe 2 O 3 and abrasive powders, properly processed, can be used as a material for magnetoabrasive machining and polishing of variously shaped components.In recent years, a great deal of attention in mechanical engineering has been focused on finishing operations aimed at tightening the finishing tolerance of machined components; in this connection, there has been increased interest in the use of the magnetic abrasive machining (MAM) method. In the MAM method, a magnetic field is used to generate cutting and polishing forces to treat the surface of a machined part. The magnetic field behaves as an elastic bond for the abrasive ferromagnetic grains and allows more effective use of the abrasive's cutting edges; furthermore, it provides conditions for a small cutting force and a low surface temperature for finishing operations.The MAM method offers a number of advantages over the conventional techniques of abrasive treatment [1, 2]: (i) abrasive grains are spread uniformly over the treated surface, which allows effective finishing of complex-shaped components; (ii) the abrasive grains do not suffer from overloading; (iii) instantaneous temperature spikes can be readily avoided; (iv) the cutting temperature can be lowered to 473 K; (v) selective polishing is possible on ferromagnetic materials in which surface asperities (magnetic field concentrators) are cut off; (vi) the force (typically up to 1 MPa) at which the abrasive grains act on the surface treated promotes the formation of a new high-disperse phase and converts the tensile stresses into compressive.The readjustment of machine-tool equipment for handling components of different size and shape by the MAM method is not usually an easy task, and for this reason the use of MAM techniques is cost-effective either on large-scale production, or for solving special technological problems.The MAM machine tools can be classified with regard for the arrangement of magnetic poles: for cylinder-shaped components, for flat-surface components, and for small-size complex-shaped components; schematically, this is shown in Fig. 1 [3 , 4]. Magnetic abrasive (MA) materials with particles of different shape can be used; schematically, this is shown in Fig. 2.A general-purpose MA powder which would be equally good for roughing, cutting and polishing operations is yet to be developed. The conventional methods for preparation of adhesive powders are purpose-oriented and the powders pre-
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