Electric heating – Metal heating – Of cylinders
Patent
1995-12-13
1998-02-24
Wong, Peter S.
Electric heating
Metal heating
Of cylinders
219105, 219611, B23K 1102
Patent
active
057214131
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for heating closely spaced end portions of two pipes to joined by forge welding or the like, wherein two diametrically opposed contacts are attached to each end portion, through which contacts each end portion is supplied with high frequency alternating current for resistance heating of the material in the respective end portion, the contacts for one of the pipes being located in close proximity to and in the same axial plane as the contacts for the other pipe.
A method of this type is disclosed in U.S. Pat. No. 4,736,084, which hereby is included by reference. This prior art method is successfully used for joining solid work pieces and thick-walled pipes, the heating current concentrating itself in the material closest to the end surfaces of the pipes due to their close proximity. However, for thin-walled pipes, e.g. made from C/Ni steel, the proximity effect may not be sufficiently high so that the current may leak away from the joint surfaces of the pipes. Furthermore, the contact points or junctions between the pipe end portions and the electrical contacts give rise to a wider heating zone resulting in a colder portion in the joint between the contacts.
SUMMARY OF THE INVENTION
The purpose of the present invention is to improve the method in question so that it may also be used successfully for thin-walled pipes and for materials having high thermal and/or electrical conductivity.
In accordance with the invention, this is achieved by a method as recited in the invention background, the method being characterized in that the contacts for one of the pipes are arranged to form an angle with the contacts for the other pipe, whereby the projections of the contacts onto said axial plane appear to cross each other.
According to an advantageous embodiment of the invention the contacts for one of the pipes are run through slots in the contacts for the other pipe.
In areas of the joint remote from the contact points or junctions the heating current may tend to spread somewhat from the joint surfaces and reduce the rate of heating. To concentrate the current close to the joint also in these areas, it is suggested according to the invention to place ferrite bars parallel to the longitudinal axes of the pipes close to the pipe wall in diametrically opposed areas between the contacts. These ferrite bars may be arranged both on the inside and on the outside of the pipes.
The effect of crossing the contacts increases with increasing angle between the contacts. Consequently, in accordance with the invention, the angle is adjusted in order to avoid overheating of the pipe material between the contacts.
The invention will be described in more detail in the following in conjunction with the exemplifying embodiments shown in the appended drawings, where
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating a prior art method,
FIG. 2 is a view similar to that in FIG. 1 but illustrating schematically an embodiment of the present invention,
FIG. 3 is an elevation view corresponding to the left part of FIG. 2 showing an alternate embodiment, partly in section along the line III--III in FIG. 4,
FIG. 4 is a section along the line IV--IV in FIG. 3, and
FIG. 5 is a section on the line V--V in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrating a prior art embodiment shows two pipes 1 and 2 having end portions 3 and 4, respectively, to be joined by means of forge welding. Prior to joining the two pipes their end portions 3, 4 are heated by means of a high frequency alternating current supplied by a source 5 through contacts 6, 7 to the upper pipe 1 and 8, 9 to the lower pipe 2.
The current density in the end portions 3, 4 is illustrated by the lines 10. As apparent from these lines, the current is less dense midway between the contacts 6, 7; 8, 9 and also near the junctions between the contacts and the respective pipe end portions. These effects lead to insufficient heating of the middle areas and the material betw
REFERENCES:
patent: 2066668 (1937-01-01), Bennett
patent: 2478640 (1949-08-01), Roberds
patent: 2542393 (1951-02-01), Chapman
patent: 2604569 (1952-07-01), Denneen
patent: 2629805 (1953-02-01), Body
patent: 2686251 (1954-08-01), Kinn et al.
patent: 2805316 (1957-09-01), Chapman
patent: 2892914 (1959-06-01), Rudd
patent: 4241284 (1980-12-01), Rudd et al.
patent: 4736084 (1988-04-01), Moe
patent: 4947462 (1990-08-01), Moe
Law Patrick B.
Levine Seymour
Wong Peter S.
LandOfFree
Method for heating closely spaced portions of two pipes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for heating closely spaced portions of two pipes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for heating closely spaced portions of two pipes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1876512