GB2121712A

GB2121712A - Filled welding electrode

Info

Publication number: GB2121712A
Application number: GB08315165A
Authority: GB
Inventors: Jorgen Stromberg
Original assignee: ESAB AB
Current assignee: ESAB AB
Priority date: 1982-06-10
Filing date: 1983-06-02
Publication date: 1984-01-04
Also published as: DE3320513C2; GB8315165D0; SE431301B; SE8203586L; GB2121712B; DE3320513A1

Abstract

The present invention relates to an arc welding electrode for the purpose of depositing an austenitic weld metal containing at least 7% Ni and at least 15% Cr, said electrode having a tubular, metal envelope and a powder filling, which contains metal powder. The envelope and the powder filling contain the same metallic constitutents together with C and Si, and the ratio of the percentage proportions by weight of each metallic constituent in the envelope in relation to the weight of the envelope to the corresponding percentage proportions by weight of the metallic constituents in the metallic powder in relation to the weight of the metal powder including the C and Si is between 0,75 and 1,33, and preferably between 0,9 and 1,1. The electrode produces weld metal of highly uniform quality.

Description

SPECIFICATION Filled welding electrode The present invention relates to a filled welding electrode having a tubular, metallic envelope and a powder filling, which contains nonalloyed and/or alloyed metal powder, for the purpose of depositing an austenitic weld metal containing at least 7% Ni and at least 15% Cr.

The filled electrode combines some of the advantages of the solid wire electrode and some of the advantages of the coated electrode. The filled electrode is, like the wire electrode, highly suitable for automatic welding. By the appropriate choice of the powder filling it is easy to regulate the amount of alloying materials supplied to the weld metal, which is also a distinguishing feature of the coated electrode.

The filled electrode is particularly suitable for welding operations of the kind in which a high rate of welding and good penetration are called for and achieves, in terms of the weight of metal deposited per unit time and the weight of metal deposited per unit of current and time, better values than the two other types of electrode. Other advantages of the filled electrode over the solid wire electrode which may be mentioned are the lower spatter losses of the filled electrode and its less tendency to form pores in the deposited weld metal.

In order to produce an austenitic weld metal which contains at least 7% Ni and at least 15% Cr, it is usual to use filled electrodes with an envelope of soft steel and with a powder filling which contains the alloying materials appropriate to the composition of the weld metal. An even distribution of these alloying materials along the entire length of the electrode is highly desirable for the uniform quality of the weld metal.

In a previously disclosed process for the manufacture of filled electrodes, a strip is first bent into a channel, which is then filled with powder. This requires the powder to be spread very evenly along the strip. Special control devices are used during filling to monitor that a constant quantity of powder per unit of length is fed into the channel. The powderfilled channel is then bent into a sealed tube.

The diameter of the sealed tube is then reduced by drawing until a diameter suitable for welding purposes has been produced, usually between about 1,2 and 3,2 mm. The distribution of the powder inside the tube can no longer be controlled during these drawing operations. The presence of a certain degree of unevenness in the distribution of the welding powder inside the tube is unavoidable in all electrodes whose diameter has been reduced by drawing.

The object of the present invention is to provide a filled electrode of the kind mentioned by way of introduction, by means of which a weld metal of very uniform quality can be achieved. In accordance with the invention a filled electrode is characterized by the envelope and the powder filling containing the same metallic constituents and by the ratio of the percentage proportions by weight of each metallic constituent in the envelope in relation to the weight of the envelope to the corresponding proportions by weight of the metallic constituents in the metal powder in relation to the weight of the metal powder including the weight C and Si being between 0,75 and 1,33, and preferably between 0,9 and 1,1. When determining the amounts of the metallic constituents no account is taken of the commonly occurring impurities.It is advisable to weld with this electrode under a protective atmosphere.

The ratio must lie within the limits 0,75 and 1,33 in order to achieve a good homogeneous weld deposit. If the ratios lie between the limits 0,9 and 1,1 the quality of the weld deposit meets all present known requirements.

The percentage proportion of each metallic constituent in the enelope must not, therefore, differ significantly from the corresponding percentage proportion in the powder. If the envelope contains, for instance, a% of Ni in relation to the weight of the envelope, then the powder must contain a minimum of 0,75 a% of Ni or a maximum of 1,33 a% of Ni, and preferably a minimum of 0,9 a% of Ni or a maximum of 1,1 a% of Ni, in relation to the weight of powder determined from the metal powder plus C and Si.

In accordance with a preferred embodiment of the invention, the filled electrode has an envelope which contains in addition to a maximum of 0,1 5% C and a maximum of 2,0% Si as metallic constituents in non-alloyed or alloyed form 17-26% Cr, 9-14% Ni, a maximum of 6% Mn, with the remainder being Fe, these percentages relating to the weight of the envelope, and a powder filling which, in that part consisting of metallic consituents together with C and Si, contains in addition to a maximum of 0,1 5% C and a maximum of 2,0% Si as metallic constituents in non-alloyed and/or alloyed form 17-26% Cr, 9-14% Ni, a maximum of 5% Mo, and a maximum of 6% Mn, with the remainder being Fe powder, these latter percentages relating to the weight of that part of the powder filling which is composed of said metallic constituents, C and Si.

In accordance with the invention it is further advantageous that the powder filling contains slag-forming constituents and/or arc stabilizers which in total amount to at least 20% of the total weight of the powder filling. For example, Awl203 and SiO2 may be used as slagforming constituents, and CaF2 and CaCO3 may be used as arc stabilizers.

It is also advantageous that the ratio of the weight of the envelope to the total weight of powder lies between 0,9 and 2,0, and preferably between 1,2 and 1,7. If the ratio is less than 0,9 the envelope will be too thin, and if it is more than 2,0 the envelope will be too thick. At ratios outside these limits, considerable problems will arise in conjunction with the manufacture of the electrodes, especially when they are to be drawn to the required diameter.

Claims

1. Filled welding electrode having a tubular metallic envelope and a powder filling, which contains non-alloyed and/or alloyed metal powder, for the purpose of depositing an austenitic weld metal containing at least 7% Ni and at least 15% Cr, wherein the envelope and the powder filling contain the same metallic constituents and the ratio of the percentage proportions by weight of each metallic constituent in the envelope in relation to the weight of the envelope to the corresponding percentage proportions by weight of the metallic constituents in the metal powder in relation to the weight of the metal powder including the weight of C and Si is between 0,75 and 1,33, and preferably between 0,9 and 1.1.

2. Filled welding electrode in accordance with Claim 1, wherein the envelope contains in addition to a maximum of 0,1 5% C and a maximum of 2,0% Si as metallic constituents in non-alloyed and/or alloyed form 17-26% Cr, 9-14% Ni, a maximum of 5% Mo, and a maximum of 6% Mn, with the remainder being Fe, these percentages being in relation to the weight of the envelope, and the powder filling which, in that part consisting of metallic constituents together with C and Si, contains in addition to a maximum of 0,1 5% C and a maximum of 2,0% Si as metallic constituents in non-alloyed and/or alloyed form 17-26% Cr, 9-14% Ni, a maximum of 5% Mo, and a maximum of 6% Mn, with the remainder being Fe powder, these latter percentages being in relation to the weight of that part of the powder filling which is composed of said metallic constituents, C and Si.

3. Filled welding electrode in accordance with Claim 1 or 2, wherein the powder filling contains slagforming constituents and/or arc stabilizers which in total amount to not more that 20% of the total weight of the powder filling.

4. Filled welding electrode in accordance with any of the Claims 1 to 3, wherein the ratio of the weight of the envelope to the total weight of powder is between 0,9 and 2,0, and preferably between 1,2 and 1.7.