Electric heating – Metal heating – For deposition welding
Patent
1993-10-18
1994-11-08
Shaw, Clifford C.
Electric heating
Metal heating
For deposition welding
21912512, 2281737, B23K 904
Patent
active
053629370
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the overlaying of weld metal onto metal plates and in particular it relates to plates of the type in which the material such as mild steel used in the production of various apparatus is faced with a layer of weld metal deposited by welding means to provide a hard facing or alloy cladding.
Overlaying of weld metal is already well known in the art and is used for instance in supplying tips to tools such as shears and the like used in agriculture and it is also known to overlay plates by welding. Overlaying may also be used to face metal with another metal or alloy.
One method of overlaying plates is to form a plate into a cylinder and then to fit this cylinder into a machine so as to rotate the cylinder beneath an array of welding heads positioned to deposit a layer of welding material onto the plates progressively as it is rotated until the entire surface of the plates in its cylindrical form is covered, after which the plate is cut and straightened to produce the hard faced sheet of material. A problem in such an arrangement is first that considerable work is entailed in forming the plates into a cylindrical form and then to straighten the plates into the form in which they will be used during manufacture of products. Certain difficulties also exist in control of the welding because of cylindrical form of the plate at the time that the welding material was applied by the heads. It is also a practical restriction on the size of a plate which can be welded by such a method.
Another problem exists with weld overlaying is that in the sheet material some portions of the sheet are heated more than others because two welding heads pass over the same area and this gives an uneven thickness of weld metal overlay and perhaps some change to the metallurgical structure of the underlying metal.
It is an object of the present invention to provide an improved method of manufacture and in order to carry out that method not subject to the difficulties encountered heretofore and this is achieved according to this invention by applying weld metal to form an overlay on the plate while the plate is in planar form and hence without any need for the step of cylindrical formation and subsequent flattening to planar form.
A further problem exists that when applying weld metal to a planar plate then some buckling can occur because of differences in temperature along the plate and hence this present invention includes means to prevent problems with distortion. Distortion causes a difference in distance between the metal and the welding head which causes arc instability and may cause irregularities in weld metal deposition.
This present invention provides solutions to the above problems or at least provides an alternative construction of machine.
In one form therefore the invention is said to reside in a weld overlaying apparatus comprising drive means to draw a metal plate substantially horizontally through the apparatus, and a plurality of welding heads arranged on a common oscillating carrier to oscillate for oscillating movement transverse to the direction of travel of the metal plate, characterized by an assembly positioned so as to be under the metal plate in use, wherein the assembly includes a slight upward convexity in the metal plate under the welding heads so as to accurately position the metal plate with respect to the welding heads.
It will be seen that by providing the slight upward convexity the metal plate is held in tension so that buckling will be minimized and hence the difference in distance between the surface of the metal plate and welding electrodes will vary as little as possible and hence a more even arc and a better lay down of weld metal will occur.
Preferably the assembly is a wheel assembly, and more preferably the wheel assembly is positioned under the welding head.
In one form of the invention the wheel assembly may include water cooling means whereby to cool the underside of the metal plate at the point of welding.
By cooling the metal plate at the point of welding minimum hea
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Browne George W.
Kostecki Gene
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