Metal treatment – Compositions – Heat treating
Patent
1983-02-02
1984-10-30
Stallard, W.
Metal treatment
Compositions
Heat treating
148 115A, 148 115C, 148 115N, 148 12R, 148 12E, 148 12EA, C22D 104, C22D 108, C22D 110, C21D 714
Patent
active
044798334
DESCRIPTION:
BRIEF SUMMARY
The starting point of the invention is a process for manufacturing a semi-finished product or a finished component by hot working a metallic material.
In the hot working of metallic materials, efforts are made, for economic reasons, on the one hand to keep the number of process steps as low as possible and, on the other hand to approach the final shape as closely as possible, in order to restrict the extent of any expensive cutting-type machining operation which may be required. Known processes of this type are, for example, isothermal or quasi-isothermal working (working with heated tools), in the manner which has gained wide acceptance, above all, in the case of forging (die-forging). Furthermore, attempts are made, by carrying out the working operation in the so-called "superplastic" state of the material--insofar as such a state can be brought about at all--to reduce the resistance to deformation while simultaneously improving the die-filling capability (see G. Schro/o/ der, "Isothermes und superplastisches Umformen beim Gesenkschmieden [Isothermal and superplastic working in die-forging]", Werkstatt und Betrieb 113/1980/11, pages 765-770; G. H. Gessinger, "Isothermes Umformen--Ein kosteng/u/ nstiges Pr/a/ zisionsschmiedeverfahren [An economical precision-forging process]", Fachberichte H/u/ ttenpraxis Metallweiterverarbeitung 11/78, pages 954-957).
In the working processes which have been described, the possibilities of an economic production process are only incompletely utilized. Conventional isothermal deformation is, as a rule, carried out at temperatures which are comparatively low, that is to say, at temperatures which are considerably displaced, for safety reasons, from the solidus temperature. However, at these temperatures the ductility of the workpiece to be deformed is not as high as would be desired, and the necessary deformation forces and deformation energy is (sic) comparatively high. On the other hand, in the case of superplastic working, there is the requirement that the blank should have an ultrafine grain size, which can be obtained only by means of certain alloying additions and elaborate thermo-mechanical processes. Certain materials exhibit no superplasticity in any case, so that these requirements with regard to the structure of the material again come into conflict with its relevant limitations. There is accordingly a major need, quite generally, to increase the scope of the possibilities offered by the hot working of metallic materials, and to extend them to as many materials as possible, through refining the processes and through widening their applicability.
The object underlying the invention is to indicate a hot-working process for metallic materials, which, while being very simple, enables semi-finished products or finished components to be manufactured in as few steps as possible and which, by virtue of a good die-filling capability, permits the design-related limits to be widened. The process should, if possible, be applicable to a large number of materials.
This object is achieved, according to the invention, by heating a workpiece, which initially exists as a cast billet, rolled billet, or a forged blank, to a temperature which lies 5 degrees Kelvin, up to a maximum of 0.15 T.sub.sol, in degrees Kelvin, below the solidus temperature of the material. The workpiece is then brought into contact with a tool, the temperature of which is kept constant, and lower by 5 degrees Kelvin, up to 0.15 T.sub.sol, in degrees Kelvin, to the solidus temperature of the material. The temperature of the same tool is also higher than the temperature to which the workpiece is preheated. Under these conditions, the workpiece is isothermally or quasi-isothermally, deformed at a deformation rate defined as .phi. below.
This deformation rate, referred to in terms of the change in cross section, is of 0 to 10 s.sup.-1. Whereby the temperature difference over the entire cross section of the workpiece, and considered over the total duration of the working operation, does not exceed 50.degree. C.
T
REFERENCES:
patent: 3655458 (1972-04-01), Reichman
patent: 4081295 (1978-03-01), Vogel
patent: 4110131 (1978-08-01), Gessinger
patent: 4404025 (1983-09-01), Mercier et al.
Gessinger Gernot
Schr/o/ der G/u/ nther
BBC Brown Boveri & Company Limited
Stallard W.
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