Metal fusion bonding – Process – With shaping
Patent
1991-07-26
1992-11-17
Ramsey, Kenneth J.
Metal fusion bonding
Process
With shaping
2281733, 228193, 228220, 228265, 428940, B23K 2024, B23K 2014
Patent
active
051636042
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for forge welding or the like of a first and a second metal part, wherein at least one joint is established between opposed bounding surfaces on the two parts to be joined, and wherein preferably a reducing gas is passed through the joint or joints before the parts are pressed together.
Such a method is known e.g. from the Applicant's U.S. Pat. Nos. 4,566,625 and 4,669,650, which hereby are incorporated by reference. In the known method a reduced cross-section of the parts to be joined is used in the joint area between the parts in order to obtain a triaxial stress condition during the welding. This results in a pressure in the joint area which is several times higher than the uniaxial yield stress of the material at the temperature in question, with a consequential quicker and better diffusion.
It has now surprisingly been found that an equally good triaxial and pore closing forge welding operation may be performed in a new and simplified manner particularly suited for non-rotation symmetrical joint surfaces.
BRIEF DESCRIPTION OF THE INVENTION
This is obtained according to the invention by a method of the type mentioned by way of introduction, the method being characterized in that the bounding surfaces are provided with generally matching corrugations, which matching corrugations are given a somewhat different height.
The use of this joint form provides a number of advantages. For instance, better material properties in the weld are obtained, and testing methods provide more reliable results for the material properties. The form of the joint is simplified, i.e. it becomes simpler to make because oxy/plasma cutting may be used for large joint surfaces instead of turning/milling. Furthermore, the joint becomes better self-centering properties and, besides, one can obtain a triaxial stress condition by forging sections which are not round or axisymmetrical. A further advantage is that the finished weld becomes a better appearance since a smaller upset length is required during the pressing together of the parts. This also results in less danger of buckling during the pressing together.
A major advantage of the method according to the invention is that it enables the use of forge welding regardless of the dimension and form of the cross-section. In the above mentioned patents of the Applicant the subject is welding of pipes and bolts. The form of the joint described therein satisfies all conditions for triaxiality in order to close pores in an efficient manner. Furthermore, it is described how surface oxides may be removed by means of a reducing gas.
In the present invention one can permit a larger unreduced layer of oxides since a fracture caused by fatigue, impact or bending stress will run through the base material and only cross the weld at an acute angle at some places. The form of the objects to be welded are of less importance, and the heating zone becomes simpler to establish because the distance between the joint surfaces is less.
Practical experience has shown that the joint form used in the present invention results in better Sharpy V-notch values than the earlier joint when oxides difficult to reduce are present after welding, e.e. SiO.sub.2, TiO.sub.2, Al.sub.2 O.sub.3 and to a certain extent MnO.sub.2.
Further advantageous features of the invention are given in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For better understanding of the invention it will be explained more closely with reference to the exemplifying embodiment shown schematically in the appended drawing.
FIG. 1 shows perspectively a portion of a rail, the end surface of which is shaped in accordance with the present invention.
FIG. 2 shows a side view of the end portions of two rails shaped in accordance with the invention before being welded together.
FIG. 3 shows at a larger scale a vertical section through the circled portion in FIG. 2.
It is first referred to FIG. 1, where the end portion of a rail 1 is shown. The end surface of the rail i
REFERENCES:
patent: 3766633 (1973-10-01), Lehrheuer et al.
patent: 4566625 (1986-01-01), Moe
patent: 4964564 (1990-10-01), Neal et al.
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