FI63876C - SAETT ATT MEDELST SMAELTSVETSNING AOSTADKOMMA FOERBINDNING MELLAN TVAO METALLSTYCKEN - Google Patents

Description

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Sweden-Sweden (SE) 750U837 ~ 1 (71) Fagersta Aktiebolag, Fack, S-773 01 Fagersta, Sweden-Sweden (SE) (72) Kjell Moriin, Fagersta, Rolf Lennart Johansson, Äkersberga,

Swedish-Swedish (SE) (7M Antti Impola (5U) Method by fusion welding to achieve a joint between two metal pieces - Sätt att medelst smaltsvetsning ästad-komma förbindning mellan tvä metallstycken

The invention relates to a method of fusion welding to provide a joint between the edges of two metal pieces or a strip or plate shaped like a tube or the like, wherein the edges to be joined to the material, i.e. over the metal pieces or strip or sheet, are preheated by a first array to a temperature just above the melting point of the material. below, after which a complete fusion of the edges is achieved by the second group of arcs, and heat is supplied by the third group of arcs so that the solidification of the weld seam thus formed results in a smooth seam surface without melting recesses or the like.

For example, when fusing welded pipes with a TIG arc, in some cases several arcs in succession on the same line are used to effect welding. The disadvantage of this type of welding with a TIG arc is that the arc is too wide and its temperature is too low, which results in the weld seam on the other hand becoming relatively wide at the top, i.e. sponge shape, and that, on the other hand, welding is relatively slow due to the low temperature despite the use of multiple arcs.

2 63876 This type of welding with a TIG arc has been improved, for example, by a multi-electrode torch according to FI patent 58,600, so that different, replaceable nozzles are placed in the torches, which make the electrode and the workpiece less or less open, constricted or shielded. strangled arc. However, the patent does not show how the welding result can be improved and the operation of the different nozzles can be improved by arranging them with respect to each other.

It is therefore an object of the present invention to provide a method by means of fusion welding to obtain a homogeneous weld which is of a better and more uniform quality than has hitherto been possible with this type of welding.

Another object of the invention is to provide a fusion welding method which provides a higher welding speed.

The fusion welding method according to the invention is characterized in that the arcs, each burning between its unmelted electrode and the edges of the material, are independently controlled by adjusting the electric current and plasma gas flow and separately braking the arcs as they pass through the nozzle, suitably cooled and suitably replaceable.

The width of the arc burning between each of its non-fusible electrodes and the edges of the material is thus adjusted independently of the other arcs by constricting each arc separately as the arc passes through suitably cooled nozzles.

The advantage of the fusion welding method according to the invention compared to the known such welding methods is that the weld seam can be made much narrower, thus avoiding the so-called sponge shape, in addition to which welding goes much faster because the amount of material to be heated is smaller.

When applying the method according to the invention, three groups of arcs are used, which can be adjusted separately, whereby each group can have one, two or more arcs. Because the arcs can be individually controlled by each of the electric current, plasma gas flow, and cooled nozzles through which the arcs pass, the arcs of each group can be adapted to their specific function, i.e., preheating, complete fusing, or heat supply during solidification. The torch device used may be assembled from one or more segments, the 3 63876 CB device being guided continuously along the weldable edges of the material during welding. Of course, it is also conceivable that, on the contrary, the material, i.e. the workpiece and its weld seam, is continuously passed past the burner device, the three arc groups of the burner device being individually adapted for each function.

These functions must be adapted in such a way that heat is rapidly penetrated into the weld seam and thus the seed form of the weld seam which is common in the application of known welding methods, e.g. for welding pipes, is avoided. This means, in principle, that the arc does not have to be relatively narrowed, so it must resemble the arc used in plasma welding, and is thus the opposite of the arc of the TIG type, e.g., now commonly used for pipe welding.

When applying the method according to the invention, a separately arranged gas flow is used as plasma gas, which is introduced into each electrode space and nozzle. The plasma gas may be argon or a mixture of argon and a small amount of hydrogen gas, or a mixture of argon and a smaller amount of hydrogen gas and nitrogen. The plasma gas may also be helium or a mixture of helium and argon or a mixture of helium and a small amount of hydrogen gas or a mixture of helium, argon and a smaller amount of hydrogen gas. A mixture of helium and a small amount of nitrogen gas, or a mixture of helium, argon and a smaller amount of nitrogen gas, or a mixture of helium, a smaller amount of hydrogen gas and a quantity of nitrogen gas, or a mixture of helium, argon and a smaller amount of hydrogen gas and nitrogen can also be used as the plasma gas.

The shielding gas flow is suitably conducted from outside the nozzles to protect arcs, melt and other warm parts from the ambient air. The shielding gas stream is then suitably divided into three separately adjustable sub-streams, the first of these sub-streams being fed to one side of the arc rows, while the second sub-stream is fed to the other side of the arc rows and the third sub-stream is fed after the arc rows.

When applying the method according to the invention, a magnetic field is suitably used either at one or more arcs, suitably at all arcs, so that the magnetic effects on the arcs caused by the current of other arcs can thus be reduced or eliminated. The magnetic field can be provided by permanent magnets, electromagnets or additional current loops.

Claims (2)

11,638 7 6 A method of fusion welding to provide a joint between the edges of two metal pieces or a strip or sheet shaped like a tube or the like, wherein the edges of the material, i.e. the metal pieces or strip or sheet, are preheated by a first group of arc to a temperature just below or , after which the complete fusion of the edges is achieved by a second group of arcs, and heat is supplied by a third group of arcs so that solidification of the weld thus formed results in a smooth seam surface without fusion recesses or the like, characterized in that the arcs burn each between the edges, are adjusted independently by adjusting the electric current and the plasma gas flow and separately by arcing the arcs as they pass through the nozzle, which are suitably cooled and suitably cooled. replaceable. Method according to Claim 1, characterized in that the arc and the material are continuously moved relative to one another along the weld seam.