Metal fusion bonding – Process – With shaping
Patent
1983-12-12
1986-01-28
Ramsey, Kenneth J.
Metal fusion bonding
Process
With shaping
2281732, 228193, B23K 2000
Patent
active
045666253
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The present invention relates to a method for joining parts of metal by means of diffusion welding, comprising the following steps: establishing a joint between opposed bounding surfaces on the respective parts to be joined, heating of the parts to a predetermined temperature in at least those areas bordering on the joint, joining the parts by pressing the parts together, and cooling the parts.
Advantages and disadvantages of diffusion welding are known i.a. from Welding Handbook, 7. edition, volume III, pages 312 et sec.
Among the advantages can be mentioned that joints can be formed having properties and microstructures which are very similar to those of the base material and joining is possible where the form of the work pieces makes it difficult to use other methods. Furthermore, joints can be made having minimal deformations and without consecutive machining or forming.
Among the disadvantages can be mentioned that the cost of the equipment is usually very high, a fact that limit the size of the parts that may be diffusion welded in an economic manner. Furthermore, the necessity of supplying heat and a high compressive force in an environment such as vacuum or protective atmosphere will give rise to grave problems as regards the necessary equipment and therefore constitute a substantial limitation in the applicability of the method. In addition, one has assumed that the method requires very careful and thorough surface preparation and, besides, that it requires more time than conventional methods.
Nevertheless, it is an object of the present invention to adapt a method of the above mentioned type for making a pipeline for offshore transportation of gas and oil. Making of such pipelines today is done by welding together pipe sections manually or by CO.sub.2 automatic equipment on board a laying vessel. Usually the welding of the pipes occurs at several stations concurrently in order to increase the laying speed. Due to practical reasons the stations are placed on a horizontal line and several welders can weld on each station concurrently. The finished pipe is let out behind the laying vessel over a so-called "stinger" which prevents the pipe from breaking directly behind the laying vessel and runs in a S-shaped curve down towards the sea floor. A certain tension is maintained in the laid pipeline, and for this purpose the laying vessel must have anchors by means of which it is pulling itself forward during the laying of the pipeline. These anchors must from time to time be moved forward in front of the vessel and for this purpose it is necessary to use auxiliary vessels.
For various reasons it would be desirable to be able to run the pipeline generally vertically downwards from the laying vessel, so that the pipeline would run in a single bend down towards the sea floor. This would i.a. entail better control of the stresses in the laid pipeline, and one could avoid anchors and auxiliary vessels and instead make do with dynamic positioning of the laying vessel. With the pipeline vertically oriented on board the laying vessel, however, it would be very difficult to use more than one welding station. With the present slow welding procedures this would therefore not give sufficient laying speed to be of practical interest.
According to the present invention it is provided a method which makes it possible to join two pipe sections so quickly that sufficient laying speed can be obtained in order to use vertical orientation of the pipeline on board the laying vessel, thus enjoying the advantages this will entail.
This is obtained according to the invention by a method of the above mentioned type, which is characterized in that the joint at the outset is given the form of a cavity which has a generally increasing height from the periphery towards the middle and is provided with at least one connecting conduit, in that the cavity of the joint during the heating first is supplied with an inert or reducing flushing gas until the joint is tightly closed along its periphery, in that the ca
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Jordan M.
Ramsey Kenneth J.
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