Metal fusion bonding – Including means to force or clamp work portions together...
Patent
1998-07-06
2000-11-28
Ryan, Patrick
Metal fusion bonding
Including means to force or clamp work portions together...
228 41, 2282343, 164469, 164470, 104 15, B23K 3102, B23K 3700, B22D 1100, E01B 1144
Patent
active
061523496
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a welding mold for butt-jointing two metal parts, such as railway rails, having a specific mutual separation to define a gap between them, said mold comprising a plurality of refractory material components adapted to be assembled together to nest locally with the two parts and to complement each other so as to delimit with them, around said space, a molding imprint adapted to receive a molten filler metal.
The molten filler metal is generally obtained by aluminothermic reaction and molds of this kind are used to butt weld diverse metal parts, usually bars of constant or approximately constant cross-section, namely not only railway rails but also concrete reinforcing rods, metal beams, etc.
Experience of this method of welding indicates that, for the quality of the weld, it is important for the gap between the ends of the parts to be welded to have a specific dimension with certain tolerances. If the gap is too large, the volume of filler metal is insufficient to fill it entirely, although this defect is obvious when the mold is opened, so that it is evident that the weld must be done again; however, if the gap is too narrow, the defect is not visible and is not detected until a later time, after the railway track or other structure is put into use, in the form of a fault that must be repaired urgently.
What is more, the welding molds currently available on the market, in particular for aluminothermic welding of rails, can be placed in a position such that they are not correctly centered relative to the gap, which means that any pre-heating of the rail end pieces or other metal parts followed by their heating by the filler metal are effected under different conditions, compromising the homogeneity of the weld.
The aim of the present invention is to remedy these drawbacks and, to this end, the present invention proposes a mold of the type indicated in the preamble characterized that at least one of said components of the mold includes, inside the imprint, at least one spacer member shaped and sized so that it can be engaged in said gap if the two parts have a mutual separation at least equal to said specific mutual separation, in order to enable nesting of said component over the two parts in a specific relative position and the mutual assembly of said components of the mold and such that it cannot be engaged in said gap if the two parts have a mutual separation less than said specific mutual separation, in order to prohibit the nesting of said component over the two parts in said specific relative position and the mutual assembly of said components, said spacer members being made from a material that degrades without producing residues likely to degrade the weld at a specific temperature lower than the melting point of the parts.
A person skilled in the art will readily understand that the presence of the spacer members when the components of the mold are assembled around the end portions of the metal parts to be welded prevents their assembly if the gap between them is too small, i.e. if the welding defect caused by failure to comply with the specific mutual separation would not be immediately visible on opening the mold, it being understood that too large a mutual separation of the end portions of the parts remains possible but has less serious consequences since the defect is immediately visible and can therefore be remedied immediately.
When the spacer member can enter the gap between the end portions of the parts to be welded, and when the separation of the latter conforms to the specific mutual separation corresponding to a weld of good quality, with a permissible tolerance, the spacer member not only does not oppose the assembly of the parts of the mold, but also, by engaging between the end portions of the parts to be welded, assures centering of the assembled mold so that it is certain that the two end portions will be treated identically during any pre-heating and during welding, i.e. to assure the homogeneity of the weld.
The shape of the spacer member can naturally
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Railtech International
Ryan Patrick
Stoner Kiley
LandOfFree
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