Metal deforming – With cleaning – descaling – or lubrication of work or product – Lubricating
Reexamination Certificate
2000-11-30
2002-08-13
Crane, Daniel C. (Department: 3725)
Metal deforming
With cleaning, descaling, or lubrication of work or product
Lubricating
C072S282000
Reexamination Certificate
active
06430980
ABSTRACT:
BACKGROUND OF THE INVENTION
a.) Field of the Invention
The invention relates to the field of metallurgy and is directed to a method and a device for coating and shaping strand-shaped metallic material by drawing using lubricants in solid to liquid state.
b.) Description of the Related Art
In shaping metallic materials by drawing, solid, semi-solid and liquid lubricants are used, so that a lubricant layer is generated on the material to be shaped.
In a known method and a device for applying solid or semi-solid lubricants for cold-forming of metallic materials, the shaping stock is introduced into a closed chamber containing a lubricant which is liquefied under the influence of pressure and/or heat (DD 147 209). The chamber is constructed as a heatable pressure chamber and is connected with a charging and pressure-generating device for the lubricant. The pressure chamber has an inlet nozzle and an outlet nozzle through which the shaping stock to be coated passes.
This method and this device, which are suitable only for applying lubricant but not for simultaneous shaping in the outlet nozzle, have the disadvantage that the utilized lubricant has a low viscosity in its liquefied state. This limits the range of variation with respect to layer thickness and, because of the very thin lubricant layers that are achievable between the two elements in a frictional relationship, namely, the shaping tool and shaping stock, metallic shaping stock which is coated in this way passes through only one or only a few shaping stages with this coating. Moreover, the sealing of the inlet nozzle and the outlet nozzle is problematic, likewise because of the low viscosity of the lubricant.
Further, methods and devices are known in which a lubricant pressure is generated hydrostatically. In one of these devices, the wire passes through a pressure chamber containing a liquid lubricant before entering the drawing die. The lubricant pressure is generated by a pump. Another drawing die is used as a sealing nozzle at the inlet side of the pressure chamber for sealing (J. Schiermeyer, Dissertation TU Clausthal 1979; U.S. Pat. No. 3,413,832). Hydrodynamic lubrication conditions are to be generated in the main drawing nozzle by this construction of the device.
Difficulties are created in this prior art by sealing the pressure chamber by the sealing nozzle since additional lubrication must be carried out in case smaller dimensional changes are realized. It is also disadvantageous that the device must be provided with a wire that is already lubricated. Another disadvantage consists in that the shaping stock shaped by this device can generally not be used for further, subsequent shaping steps without re-coating with lubricant.
Another possibility for introducing the lubricant in the shaping zone of the drawing die under high pressure consists in arranging a run-in part of varying length in front of the drawing die; this can be a pipe, a profiled funnel or a drawing die (L. Gogecki, T. Prajsnar, Draht-Fachzeitschrift [Wire—Technical Periodical] 1972, 12, pp. 768-771; J. Schiermeyer, Dissertation TU Clausthal 1979). The inner diameter of the run-in part is slightly larger than the diameter of the wire running into it. Such devices are called hydrodynamic pressure nozzles. The elevated lubricant pressure is generated automatically by the moving wire transporting the lubricant (hydrodynamic pressure buildup). Very high lubricant pressures of approximately 300 MPa are generated in this way. This procedure has the disadvantage that the lubricant is pressed out of the tools in an uncontrolled manner due to the high pressures and the tools are frequently damaged or even destroyed.
Another known method and a device for shaping and/or coating strand-shaped shaping stock uses a pressure chamber having an inlet nozzle and an outlet nozzle for the shaping stock and a special feed for solid to pasty lubricant (WO 96/14946). For this purpose, a very high pressure in the range of several hundred MPa is applied to the lubricant in the pressure chamber externally by means of a special apparatus, wherein a combination of lubricant pressure and lubricant temperature is applied which avoids liquefaction of the solid to pasty lubricant in the pressure chamber. However, this process is disadvantageous in that the external generation of the high lubricant pressure involves a very high expenditure on apparatus and, on the other hand, in that lubricant frequently exits from the inlet nozzle in an uncontrolled manner in this device in the direction opposite to the drawing direction, especially during the transition of the lubricant to the pasty state. The escape of lubricant happens particularly when drawing wire rod which is often not round and/or when the device operates in the range of high lubricant pressures.
OBJECT AND SUMMARY OF THE INVENTION
It is primary the object of the invention to develop a method and a device for coating and shaping strand-shaped metallic material by drawing which enable high-performance shaping while appreciably reducing expenditure on apparatus, wherein sealing problems are eliminated at the same time and one or more technical parameters in the shaping and coating process are further improved depending on the material to be shaped.
This object is met according to the invention by a method for coating and shaping strand-shaped metallic shaping stock by drawing using lubricants in solid to liquid state in that the shaping stock is coated with lubricant by means of a double chamber arrangement comprising a low-pressure lubricant chamber followed by a high-pressure lubricant chamber and is shaped by means of working drawing dies at the outputs of the chambers. In so doing, the low-pressure lubricant chamber is filled with solid to pasty lubricant by an external lubricant feed and a low pressure is applied to the lubricant in the low-pressure lubricant chamber by means of this lubricant feed. A high lubricant pressure is generated in the high-pressure lubricant chamber by the shaping stock which runs into this chamber and which is coated with lubricant in solid to liquid state. The lubricant pressure/lubricant temperature combination in the high-pressure lubricant chamber is adjusted in such a way that the lubricant is in solid to liquid state in the latter.
According to the invention, the lubricant pressure in the high-pressure lubricant chamber is influenced by changing the shaping parameters and process parameters, especially by changing the lubricant pressure and the lubricant temperature in the low-pressure lubricant chamber, the drawing speed, the drawing die geometry and the degree of shaping.
According to an advisable development of the invention, the thickness of the lubricant film on the shaped material is measured and/or the lubricant pressure in at least one of the pressure chambers is measured. The measurements obtained are utilized for controlling or regulating the drawing speed, the lubricant pressure and/or the lubricant temperature.
The low-pressure lubricant chamber is advisably filled with lubricant continuously and via only one feed opening by means of an extruder and/or a gear pump. In so doing, the required lubricant pressure is also generated in the low-pressure lubricant chamber with these devices simultaneously in an advantageous manner.
According to the invention, a lubricant pressure of 80 MPa to at least 500 MPa is regulated in the high-pressure lubricant chamber. A lubricant pressure ranging from 0.2 MPa to a maximum of half of the value of the lubricant pressure to be adjusted in the high-pressure lubricant chamber is generated in the low-pressure lubricant chamber depending on the lubricant pressure desired for the high-pressure lubricant chamber.
The method can be applied in a single-step process as well as repeatedly in a multiple-step process. After an interruption in the shaping processes, it is advisable to carry out a brief reversal of the relative movement between the shaping stock and double chamber arrangement taking place during the shaping process and/or to red
Huebner Armin
Kurze Bernhard
Weinhold Harri
Zschorn Gerd
Crane Daniel C.
Ecoform Umformtechnik GmbH
Reed Smith LLP
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