Metal treatment – Process of modifying or maintaining internal physical... – Chemical-heat removing or burning of metal
Patent
1986-12-22
1989-05-23
Brody, Christopher W.
Metal treatment
Process of modifying or maintaining internal physical...
Chemical-heat removing or burning of metal
148154, 72341, C21D 800
Patent
active
048327646
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process in accordance with the superimposed concept of Patent claim 1 as well as a system for implementation of the process and an application of the process.
For attaining the properties such as hardness, viscosity, wear resistance, fatigue resistance required for a particular application, workpieces of hardenable metallic materials, particularly iron materials such as steels, are commonly subjected to a process of hardening/tempering. The process of hardening/tempering generally comprises several treatment steps, i.e. a hardening treatment by quenching a workpiece heated to hardening temperature and a subsequent controlled heat treatment such as annealing, tempering, or holding at a sepcified temperature and/or controlled cooling.
In order to prevent the workpiece from being subject to a change in its shape and/or its dimensions during the process of hardening/tempering, i.e. from becoming distorted, a quenching press is used in which the workpiece is chucked and quenched in its chucked state. In known processes, quenching is achieved using quenching presses in which a liquid quenching medium circulates around the workpiece. The selection of the quenching medium for this purpose depends upon its thermal capacity and the size of the temperature drop to be set, in particular the quenching speed. In general, water, saline solutions, or oils are used as quenchants. When using liquid quenchants, in particular saline solutions or oils, it is disadvantageous that after quenching the quenchant-contaminated workpiece must be cooled to near room temperature and washed before it can be subjected to the subsequent heat treatment step, heating to tempering temperature, for example. This intermediate treatment by washing is not only time-consuming and labor-intensive, but can even lead to stresses and deformation of the workpieces.
Particularly complicated is the manufacture and hardening of disk springs such as those used for clutches in the automobile industry. Such disk springs are heated to hardening temperature, if necessary preceded by cold forming of the slugs in the furnace, and then quenched in an oil bath or in quenching presses, then cooled, cleaned of oil and tempered. In these processes, deformations cannot be avoided. Various post-treatment processes are complicated and costly and, nevertheless, do not bring about any significant improvement.
Exceptionally problematic and costly is the manufacture of disk springs which have lamellae projecting radially inward from an outer closed annular part, (lamellae)* the ends of which require greater hardness than the remainder of the disk springs. In order to produce areas of differential hardness, such workpieces must be subjected to a separate treatment after completion of the hardening process. Either the areas in which greater hardness is desired are coated with a resistant material such as molybdenum, or they are hard-chromium plated, or the disk spring is subjected to a second complete hardening treatment for the area of greater hardness. Such additional treatments are in every case complicated and costly and involve an additional risk of deformation of the disk spring.
It is known that the structure of a workpiece obtained by means of a thermomechanical treatment determines its mechanical properties such as hardness, viscosity, mechanical resistance, fatigue resistance. In addition to the composition, the formation of a certain structure, in turn, depends, however, primarily upon the metallurgical parameters applied during heat treatment. Thus, it is only by their exact setting and adherence to them that the formation of a structure can be achieved which is endowed with the required properties. Disadvantages demonstrated in the processes known to this time, have been in particular the needed long heating and cooling periods, the long conveying periods between the individual treatment stations and the difficulty of exactly controlling the time-temperature response required in these processes.
The object of the invention is, therefore,
REFERENCES:
patent: 3668917 (1972-06-01), Komats et al.
patent: 3703093 (1972-11-01), Komatsu et al.
patent: 3753798 (1973-08-01), Komatsu et al.
Article Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 18-23, Sep. 1976.
Brody Christopher W.
Jenny Pressen AC
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