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United States Patent 3,562,470
Bobart ,   et al. February 9, 1971



Disclosed herein in a continuous heating line is an induction heating apparatus for the supplemental discrete heating of corner edges of thick elongated metal workpieces of rectangular cross section in conjunction with heating by other means along such line, in behalf of temperature uniformity sectionally of the workpieces, at which apparatus includes induction heating coil means affiliated with laminations concentrating and directing the magnetic flux produced by such coil means diagonally through such corner edges.

Inventors: Bobart; George F. (Ellicott City, MD), Emerson; William A. (Ellicott City, MD)
Assignee: Westinghouse Electric Corporation (Pittsburgh, PA)
Appl. No.: 04/835,951
Filed: June 24, 1969

Current U.S. Class: 219/646 ; 219/656; 219/660
Current International Class: H05B 6/02 (20060101); H05b 005/00 (); H05b 009/02 ()
Field of Search: 219/10.43,10.69,10.61,10.71,10.79

References Cited

U.S. Patent Documents
2448009 August 1948 Baker
2902572 September 1959 Lackner et al.
3056876 October 1962 Schmidt
3444346 May 1969 Russell et al.
Primary Examiner: Truhe; J. V.
Assistant Examiner: Bender; L. H.


We claim:

1. Induction heating apparatus for a heating line to effect localized heating of temperature deficient side corner regions of an elongated thick workpiece of rectangular cross-sectional configuration including other heating means along such line, said heating apparatus comprising: elongated induction heating coil means in extension along the length of such workpiece; a source of energizing alternating current for such coil means; and flux concentrating laminated core means magnetically coupled to such induction heating coil means, having pole pieces of opposite polarity diagonally spanning workpiece side corner regions and concentrating and directing magnetic flux lines from such coil means diagonally through such workpiece corner regions.

2. The induction heating apparatus of claim 1, wherein the aforesaid flux concentrating means is in form of stacked iron laminations.

3. The induction heating apparatus of claim 2, wherein the laminations of the aforesaid stacked iron laminations are E-shaped with the end legs of such shape longer than the central leg thereof, and the coil means encircles the aggregate central legs of the lamination stack and nests between the aggregate end legs, whereby such aggregate central legs constitute a common pole piece for two workpiece corners, and the aggregate end legs serve as respective opposite pole pieces for such corners.

4. The induction heating apparatus of claim 1, disposed in a heating line wherein said other heating means is an induction heating means including a helical coil into which the workpiece is inserted longitudinally.

5. The induction heating apparatus of claim 1, further including means for advancing the side corner regions of the aforesaid workpiece longitudinally past the pole pieces of the flux concentrating means.

6. The induction heating apparatus of claim 1, wherein the induction heating coil and flux concentrating means are plural for effecting localized heating of all of four side corner regions of the elongated rectangular cross section workpiece while permitting adjustment in relative positioning of such plural means to accommodate a grossly different cross-sectional dimension of such workpiece.


1. Field of the Invention

Induction heating apparatus of the continuous type.

2. Description of the Prior Art

In the heating of elongated metal workpieces of relatively large rectangular cross section, such as continuous strands, bars, slabs, ingots, or the like, of steel or other metal, up to a temperature such as required for hot rolling of such workpieces, for example, it frequently happens that corners along such heated workpieces are or become cooler than the more central workpiece portions, due to the nature of a preceding mode of heating and/or to the inherently greater rate of heat radiation from such corners following subjection to such previous heating and delay in presentation to the rolling mill. Since temperature deficient corners can introduce localized brittleness conditions leading to cracks and flaws in the rolled product, such cool-corner condition can be critical with respect to quality of such product. Heretofore, a compromise solution has been to return such cool-corner workpieces to the heating furnace, which at least is inconvenient. In the case of continuous or feed-through types of induction heating furnaces, it can become difficult to solve such cool-corner problem even by return to the furnace in cases where the sectionwise induction heating effect of the furnace on the workpieces passed longitudinally therethrough is of a significantly lesser degree in the workpiece corners; thereby tending to detract from the value of a desirable heating mode.


The induction corner-heating apparatus of the present invention offers a highly desirable solution to the aforedescribed cool-corner problem. By inclusion of such apparatus in a continuous heating line en route to a rolling mill, for example, the opportunity is afforded for accurate, rapid and effective heating of the workpiece corner regions selectively in cognizance of any existent or anticipated temperature deficiency in such regions. In series with a conventional tunnel-type induction heating furnace in a continuous heating line, the induction corner heating apparatus of the present invention affords opportunity for rapid and effective regulation of the cross-sectional distribution of heat produced in elongated rectangular cross section workpieces.


FIG. 1 is a simplified representation in plan view of a continuous induction heating line for elongated rectangular cross section workpieces, embodying an exemplification of the induction corner-heating apparatus of the present invention.

FIG. 2 is an elevation view of the exemplified induction corner-heating apparatus taken along the line II-II in FIG. 1; and

FIGS. 3 and 4 are plan and elevation views, respectively, of an alternate arrangement of the exemplified corner-heating apparatus of the present invention as affiliated with a relatively wide elongated rectangular cross section workpiece in a continuous heating line.


Referring to FIGS. 1 and 2 in the drawing, an exemplification of an induction corner heating means 10 is shown associated with an elongated workpiece 12 of square cross section to simultaneously heat the four 90.degree. corner regions 14 of such workpiece while travelling longitudinally along rollers 16 in a continuous heating line which includes other heating means such as a helical-coil induction heating means or furnace 18 through which such workpiece also travels.

In accord with the exemplified embodiments of the present invention as shown in FIGS. 1 and 2, the corner-heating means 10 comprises the two sets 20 of elongated straight-sided water-cooled induction coils 22, 24 extending along and parallel to the upper and lower flat faces of the workpiece 12 and formed by a number of turns of rectangular cross section copper tubing; one coil 22 encircling the other coil 24. The two coils can be connected in series, and energized via leads 26 from an AC power source at such as line frequency of 60 Hz, for example, in the case of cross-sectional workpiece dimensions measured in inches, for example.

The elongated side leg portions 26, of the induction coils 22 and 24, in extending along the corner regions 14 of the workpiece 12 create magnetic flux lines that are directed transversely of such corner regions and thereby induce longitudinal heating currents therein.

To concentrate, direct and focus such magnetic flux lines diagonally across such corner regions 14, as indicated by arrows 15 in FIG. 2, and hence also enhance the efficiency of such coils 22 and 24, the corner-heating means 10 comprises registering stacks of steel laminations 28 in which such coils are nested and secured. As exemplified, each of such laminations may be E-shaped in broadface view, to accept the side leg portions 26 of the coils in the parallel elongated recesses formed by such configuration when the laminations are stacked together. At the same time, the lamination stacks are so constructed and arranged that each stack includes pole portions 30 of one polarity at its opposite sides that project transversely of the workpiece at its opposite sides, for cooperation with the centrally projecting opposite pole portion 32 of the lamination stack encircled by the coils, to provide flux diagonally pole pieces for directing the magnetic flux across the corner regions 14 of the workpiece. Also, by virtue of use of these, or other suitably-shaped lamination arrays, the magnetic coupling distance with the workpiece is considerably less critical than were induction heating coils alone employed, so that a range of workpiece sizes may be accommodated by a single corner-heating installation, as well as variance in lateral positioning within a given installation, without significance alteration of heating effect.

Where relatively wide elongated workpieces of rectangular cross section are to be accommodated, an arrangement such as shown in FIGS. 3 and 4 may be employed, with the two corner heating means 10 disposed at opposite side edges of the wide workpiece and each spanning such workpiece thicknesswise.

The foregoing description in conjunction with showings in the drawings have been simplified in behalf of clarity. In actual construction and installation of the induction corner-heating apparatus of the present invention, it also will include the usual components such as may be required for insulating the turns f the coils, introducing cooling water to the coils and to the lamination stacks, as well as for supporting the heating assemblages, etc.

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