Cored wire for treating molten metal and method of manufacture

Specialized metallurgical processes – compositions for use therei – Compositions – Solid treating composition for liquid metal or charge

Reexamination Certificate

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Details

C075S314000, C075S316000, C075S567000, C075S746000, C075S770000

Reexamination Certificate

active

06280497

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention pertains to cored wires for treating molten metals to remove unwanted impurities and in particular to the manufacture of cored wires having a reactive metal core.
Cored wires, in particular a calcium core surrounded by a sheath has found wide application in the treating of molten ferrous metals. The cored wire is used to introduce calcium into the molten ferrous metal, after being tapped from a furnace, in order to reduce unwanted elements such as sulfur and oxygen in the molten bath. A detailed discussion of the overall process is contained in U.S. Pat. No. 4,481,032, the specification of which is incorporated herein by reference.
U.S. Pat. Nos. 4,512,800, 4,705,261, 4,094,666, 4,698,095, 4,035,892, 4,097,268, and 4,671,820 all disclosed various methods of treating molten metals using a clad reactive cored metal composite in the form of an enlongated wire.
In one method of manufacture, a calcium metal core is extruded into an elongated shape or wire which has a generally circular cross section. The core wire is inserted into a metallic sheath, e.g. steel, as it is continuously roll formed into a tube. The tube is formed with a mechanical lock seam so that reactive metal, e.g. calcium, is encapsulated or locked inside. The resulting structure or product is a continuous tube or wire being a composite of a reactive core and a roll formed metallic sheath. One of the problems with the prior art roll forming process is insertion of the core into the metallic sheath.
Another problem with the prior art process has been monitoring the roll forming process to identify a problem with the lock seam at the earliest possible stage of the process in order to prevent excessive amounts of malformed lock seams and thus scrap cored wire.
BRIEF SUMMARY OF THE INVENTION
In order to facilitate the production of a suitable cored wire having a reactive metal core it has been discovered that insertion of the extruded reactive core material (wire) into the roll formed sheath can be delayed until that time in the process where the sheath has been partially formed and that the roll forming of the sheath can be married to a continuous extrusion of the solid core to achieve an improved cored wire.
Therefore, in one aspect, the present invention is a cored wire for introducing a reactive metal into a bath of molten metal produced by extruding the reactive metal into an elongated core wire having a generally cylindrical shape with a continuous flat surface, concurrently with the extrusion of the reactive metal core partially roll forming a sheath using a multi-step roll forming process, the sheath partially formed into a generally trough shaped member with peripheral edges having formed therein surfaces adapted to be mated and formed into a lock seam, inserting the core wire into the trough shaped portion of the partially formed sheath with the flat surface portion of the core positioned to accommodate a lock seam to be formed into the sheath and thereafter finishing the cored wire by further roll forming steps including closing the sheath around the cored wire and forming a continuous folded lock seam in the sheath.
In another aspect, the present invention is a method for forming a cored wire for treating a bath of molten metal comprising the steps of extruding a reactive metal core material into an elongated core wire having a generally cylindrical shape with a continuous flat surface, concurrently partially roll forming a sheath using a multi-step roll forming process, the sheath partially formed into a generally trough shaped member with peripheral edges having formed therein surfaces adapted to be mated and formed into a lock seam, inserting the core wire into the trough shaped portion of the partially formed sheath with the core positioned to accommodate a lock seam to be formed in the sheath and finishing manufacture of the cored wire by further roll forming steps closing the sheath around the cored wire and forming a continuous lock seam in the sheath.
In yet another aspect the present invention is a process for forming a cored wire wherein a core is surrounded by a metallic sheath closed by a mechanical lock seam, the sheath formed around the core from an elongated strip by a continuous multi-step roll forming process by progressively forming the sheath around the core including a roll forming step wherein the sheath has a generally cylindrical cross sectional shape with mating vertical surfaces used to form the lock seam extending from mating edges of the cylindrical portion of the sheath, the vertical surfaces extending generally perpendicular to a longitudinal axis of the generally cylindrical portion of the sheath with one of the vertical surfaces being longer than the adjacent vertical surface and overlying the adjacent vertical surface at an angle of approximately 45° to the mating surfaces, and continuously observing the roll forming process after this step to determine if the angular relationship between portions of the lock seam is being maintained. If the angular relationship is seen to deviate from that which is described to produce an acceptable lock seam the process can be adjusted or stopped to minimize production of malformed lock seam and consequently scrap cored wire.
It is within the scope of the present invention to use optical or electro-optical means to achieve the inspection step.


REFERENCES:
patent: 3777361 (1973-12-01), Fuchs, Jr.
patent: 4832742 (1989-05-01), Ototani

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