GB1597818A

GB1597818A - Welding wire

Info

Publication number: GB1597818A
Application number: GB20505/78A
Authority: GB
Original assignee: Arbed SA
Current assignee: Arcelor Luxembourg SA
Priority date: 1977-07-18
Filing date: 1978-05-18
Publication date: 1981-09-09
Also published as: FR2397915B1; FR2397915A1; DE2829517C2; IT1106857B; IT7850340A0; CH621963A5; BE865079A; NL7803750A; LU79445A1; DE2829517A1

Abstract

The flux-cored welding wire is made up of a powder core (4) surrounded by a metal jacket which is formed by two sheaths, one in contact with the other. The inner sheath is made up of two independent strips (2, 3) extending in the axial direction and each lining part of the inner wall of the outer sheath (1). The single join of the outer sheath extends approximately along the median line of the subjacent strip of the inner sheath. In order to manufacture this wire, a thin metal sheet (2) is inserted into a preshaped metal channel, which thin sheet matches the bottom of the channel and extends at least as far as the mid-height of its side walls. A bead of welding material (4) is then deposited into the thin sheet and is subsequently covered by a second thin sheet (3) whose edges are folded downwards. <IMAGE>

Description

(54) WELDING WIRE (71) We, ACIERIES REUNIES DE BURBACH EICH DUDELANGE S.A., ARBED, a company incorporated in accordance with the laws of the Grand Duchy of Luxembourg, of Avenue de la Liberte, Luxembourg, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a filled welding wire, as well as to a method for manufacture of such a wire.

These filled wires, which may be used for welding metal parts by automatic or semiautomatic arc process with or without a protective gas atmosphere as is used for remetalling metal parts, are formed of a powder core surrounded by a metal casing.

The metal casing is most often of steel, and has a circular shape of a diameter between 0.5 and 10 mm. The powder core is formed of mineral and metal powder, e.g., slag, flux, deoxidiser and alloy, which form between 10 and 70% of the total weight of the wire.

Certain wires, called "non-closed", are known. The casing of these, formed from a metal strip, has an unsealed longitudinal joint which is formed either by the edges of the strip which abut along the length of an axial line, or by the marginal areas of the strip which overlap each other. However, the juxtaposition of the longitudinal edges or the super-position of the marginal edges is not likely to ensure an hermetically sealed insulation of the powder from the external atmosphere. The powder can also deteriorate when transported or stored or when the wire or the blank used in its production is treated. Moreover, this construction is only suitable for filled wires of relatively large diameter.

Unlike "non-closed" filled wires, "welded joint" wires are absolutely sealed.

Their manufacture, which was once practically impossible because the contamination of the edges of the blank by powder during the shaping or welding did not permit the obtaining of a welding joint sufficiently flawless for a suitable drawing out of the blank, is now very easy thanks to the method disclosed in U.K. Specification No. 1,485,571. In this method, a strip of steel is continuously formed to channel section and a mixture of powder is introduced into the bottom of the channel.

Then the powder is covered over by a thin metal ribbon which secures the powder in position at the bottom of the channel when the blank is closed and when the joint is welded. The filled blanks obtained have a flawless welded joint and an homogeneous filling and undergo drawing out without too many difficulties. However, for very small diameters the wall of the blank does not stay uniformly cylindrical in the course of drawing out, but develops thicker portions followed by thinner portions which are more brittle. This becomes more pronounced if the powder contains particles of hard metal which penetrate the wall of the blank and initiate breakage. Under these conditions interruptions in production are frequent and the waste quite significant.

In accordance with the invention there is provided welding wire having a powder core surrounded by a metal shell formed by two casings, one in contact with the other, the internal casing being formed of independent strips extending axially of the wire and each lining a part of the internal wall of the external casing, the external casing having a single joint extending approximately along the median line of the underlying strip of the internal casing.

It is possible to produce welding wire over a wide range of diameters and of either the closed or non-closed type without producing flawed casings, even where the powder filling contains particles of hard metal.

The strips which form the inner casing may be of the same material as the outer casing, usually soft steel. The two casings may be of different metals provided that the ductility of the inner casing is not significantly less than the outer. The inner casing may include, for example, metal elements which produce some particular effect during welding. The strips forming the inner casing are usually thinner than the outer casing.

With the joints in the internal casing overlapped by the external casing and at least a quarter of the circumference of the wire apart, the seal can be so good that overlapping the edges of the external casing or welding the joint formed by the edges of the external casing is unnecessary. When the edges of the two strips forming the internal casing overlap each other, the filling and inner casing alone form a more or less completely sealed assembly. The risk of deformation of the edges of the joint of the external casing on coiling and stripping is much reduced compared with the conventional "non-closed" wires, because the powder is contained by the internal casing and does not work directly on the joint. However, nothing prevents closing the external joint by welding, particularly with a view to drawing to reduced diameters of the order of 1 mm.

Since the inner metal casing surrounding the powder core maintains a smooth surface facing the external casing, the filled blanks with double casing may be drawn out to the smallest diameters without breakage.

Indeed, on drawing, flow of the material of the external casing can take place without the hindrance arising from the shape of nature of the underlying material that has been encountered previously.

The filled wires according to the invention generally have a circular section and are obtainable from circular or oval blanks.

Circular or polygonal blanks, however, can also be shaped, in particular drawn out and then rolled, in such a way that the filled wire obtained has a substantially rectangular section. In general, the width of such filled wires called "flat" is at least five times greater than their thickness. These wires are suitable for obtaining wide welding bands in assembly methods, remetalling or lining of metal parts by arc welding with or without protective gas or under flux.

Also in accordance with the invention there is a method of manufacturing a welding wire which comprises forming a metal band to a channel sectibn, introducing into the preformed channel a first metal strip which corresponds in shape to the bottom of the channel and extends to at least halfway up the height of the lateral sides of this channel, laying a band of welding powder along the first metal strip, covering the powder with a second metal strip whose edges extend downwards, forming the sides of the channel to a closure along ajoint line and reducing the section of the resulting blank.

According to one form of production the metal strip intended to form the lower part of the interior casing is preformed by means of profiled rollers and then inserted in the channel.

According to another form of production, the strip for lining the bottom of the channel travels with the preformed channel and is shaped in situ and pressed against the bottom of the latter by means of a rotary roller.

The upper strip which covers the powder band and may rest against the sides of the lower strip is so shaped that the blank can be closed in without this strip becoming wedged in the joint.

Suitable apparatus for the manufacture of these filled wires with double casing corresponds, as regards tools for the forming of the external casing and of the upper ribbon, for the supply of the powder, for any eventual welding of the joint, as well as for reduction of the section of the blank, to that described in the U.K. Patent Specification No. 1,485,571. One only has to add the tools necessary for forming and putting in place the strip to line the bottom of the external casing.

An example of a welding wire according to the invention and its productions are described hereafter in connection with the drawing which shows a section through a filled blank having a double casing with welded joint.

A strip 1 of soft steel of width 32 mm and thickness 1.8 mm is formed by means of rollers into a channel section 7 mm deep and 23 mm wide.

A strip 220 mm wide and 0.3 mm thick is bent into an arc of a circle by means of rollers and introduced against the bottom of the channel.

The channel lined with the profiled strip 2 passes under a feeder-regulator which lays in it a band of welding powder 4.

At the outlet of the feed-regulator a cover sheet 3 bent into an arc of a circle from a strip 20 mm wide and 0.3 mm thick is laid on the band of powder in such a way that the edges of the cover sheet touch the sides of the strip lining the bottom of the channel.

The preformed blank is pulled through a drawing die in which the edges of the channel are turned in so as to come into contact with each other.

After cleansing with flame the blank is ready to be sent either into a welding station for the closure of the joint, or to a station for reduction of the section of the blank.

The latter operation is effected by rolling or by drawing to allow handling of the blank without leakage of the powder.

The reduction of the section of the blank to the final diameter, e.g. 0.9 mm, of the filled wire is effected by drawing.

EXAMPLE The wire has the following characteristics: external casing: killed soft steel; internal casing: killed soft steel; -the powder core is composed of 80% metal alloy and 20% flux; -the ratio of powder casing is 30% by weight.

WHAT WE CLAIM IS: 1. Welding wire having a powder core surrounded by a metal shell formed by two casings, one in contact with the other, the internal casing being formed of independent strips extending axially of the wire and each lining a part of the internal wall of the external casing, the external casing having a single joint extending approximately along the median line of the underlying strip of the internal casing.

2. Welding wire according to Claim 1 in which at least one metal strip of the internal casing is of a different composition from the material forming the external casing.

3. Welding wire according to Claim 1 or 2 in which the metal strips which form the internal casing are less thick than the external casing.

4. Welding wire according to any of Claims 1 to 3 in which the edges of the metal strips which form the internal casing overlap.

5. Welding wire according to any of Claims 1 to 4 whose section is substantially rectangular, the width being at least five times greater than the thickness.

6. A method of manufacturing a welding wire which comprises forming a metal band to a channel section, introducing into the preformed channel a first metal strip which corresponds in shape to the bottom of the channel and extends to at least halfway up the height of the lateral sides of this channel, laying a band of welding powder along the first metal strip, covering the powder over with a second metal strip whose edges extend downwards, forming the sides of the channel to a closure along a joint line and reducing the section of the resulting blank.

7. A method according to Claim 6 in which the first metal strip is preformed by rolling between profiled rollers before being laid in the channel.

8. A method according to Claim 6 or 7 in which the first metal strip is pressed against the bottom of the preformed channel by means of a movable roller.

9. A method according to any of Claims 6 to 8 in which the edges of the second metal strip rest against the sides of the first metal strip lining the bottom of the channel.

10. Welding wire substantially as hereinbefore described with reference to the accompanying drawing.

11. Welding wire substantially as hereinbefore described in the Example.

12. A method of manufacturing welding wire the method being substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. by drawing to allow handling of the blank without leakage of the powder. The reduction of the section of the blank to the final diameter, e.g. 0.9 mm, of the filled wire is effected by drawing. EXAMPLE The wire has the following characteristics: external casing: killed soft steel; internal casing: killed soft steel; -the powder core is composed of 80% metal alloy and 20% flux; -the ratio of powder casing is 30% by weight. WHAT WE CLAIM IS:

1. Welding wire having a powder core surrounded by a metal shell formed by two casings, one in contact with the other, the internal casing being formed of independent strips extending axially of the wire and each lining a part of the internal wall of the external casing, the external casing having a single joint extending approximately along the median line of the underlying strip of the internal casing.

11. Welding wire substantially as hereinbefore described in the Example.