US1794042A - Electrode - Google Patents

Description

Feb. 24, 1931- A. P. STROHMENGER 1,794,042

ELECTRODE Filed Jan. 17, 1929 -0/5 -020 CROSS SECTION OF CORE l/Y SQUHRE INCHES ATTORNEY tory for man Patented Feb. 24, 1931 UNITED STATES PATENT OFFICE ARTHUR PERCY S'IBOHIENGEB, 01' LONDON, ENGLAND, ASSIGNOR TO QUASI-ABG IITOOBPORATED, 01' NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRODE Application filed January 17, 1929, Serial No. 333,248, and in Great Britain larch 27, 1928.

This invention relates to electrodes for use in electric arc welding or the fusion-deposition of metals, and particularly to such electrodes comprising a metallic core witha" 5 coverin of a suitable flux or slag-forming materia For general welding purposes it has been usual hitherto to employ commercial mild steel of normal composition as the core metal. This has proved to be satisfacurposes but, when the welded structure is 'a le tobe subjected to stresses at a hi h temperature such as arise in forging or ending the metal while hot, the deposited metal is liable to crack. This is the 15 case even with the use of the most carefully chosen flux covering on the electrodes, and the defect may be ascribed to hot-shortness of the metal due to its physical properties within a certain temperature range.

It is well known that pure iron is brittle when maintained within a certain range of temperature above 700 0., but that the brittle zone, wherein the iron is in the beta form, may be reduced by making additions of certain other metals to the iron. Among the metals which are alloyed with iron for this and other purposes. are manganese, tungsten, molybdenum and chromium. Mild steel contains only a small amount of mangan'ese, and the weld metal deposited from a mild steel electrode only contains about 0.1% of manganese which is insufiicient to affect materially the brittleness of the metal in the temperature range in. question. It is possible to vary the consistency of the deposited metal by adding to the flux covering ingredients such as form-manganese, which become partially incorporated in the deposit and give to it some of the characteristics of an alloy steel, but the incorporation is by no means perfect owing to the very short duration of the fusion temperature in weld ing, so that the added metal is more or less segregated, and the deposit has therefore a low resistance to corrosion, resistance to which is generally of great importance in welded work. In order to obtain afhomo- 'geneous weld metal ofierin a high resistance to corrosion, I have found hat it is necessary to introduce any additional manganese into the core ofthe electrode.

Research has shown me that if I vary the percentage of manganese in a steel there is a rapid increase in the elongation under a given stress applied to the metal when the Y manganese content has passed 0.4%, and the manganese required in a steel, more especial-.

lty when that steel has been cooled rapidly rom the igneous state and no work has been or is to be applied to its afterwards.

The percentage of manganese required in' the metal deposited from an electrode by the arc welding process is in the neighborhood of 0.45%. If this percentage of managnese is contained in the deposited metal, its physical properties are improved not only when under stress at normal temperatures but also when stressed to a condition of strain at the higher temperatures about 900 C. such as are used for forging or otherwise deforming the metal. Difiiculty, however, has been experienced in obtaining this critical percentage of manganese because of the loss which occurs in the arc when depositing the metal, and it has been found that, other conditions remaining unaltered,- the loss varies inversely with the cross-sectional area of the core metal in the electrode, so that for an electrode of small gauge the loss is much greater than for a larger gauge. Hence, in order to dBPOSlt,

weld metal having the critical content of 0.45% of manganese, it is necessary to employ compositions of core metal for the electrodes which will vary inversely according to the gauge or area of cross-section of the metal core. A certain percentage of silicon can be introduced with advantage, as it tends to reduce the loss of manganese during deposition, but the consistency of the weld metal sufit'ers if more than about 0.35% or at most .Orosssection in decimals of a square inch Percentage of manganese re quired in Gauge of electrode core metal These figures are shown in graphical form in the accompanying drawing.

A wire havlng a percentage of manganese .higher than 3.5% is diflicult to draw from the billet and 4% is about the limit fora core metal which can be drawn into wire by existing methods, but it is found possible to effect the drawing up to this limit of manganese content. By the use of a higher percentage of silicon, up to 0.35% or even 0.4%, some reduction can be made in the percentage of manganese, but this is not generally desirable except for the gauges of electrodes for which the manganese content is near the limit for a metal which can be drawn to wire.

The deposited metal from electrodes having the proper percentage of manganese in the core metal to give the critical percentage of 0.45%, is found to have a cleaner and finer micro-structure than metal having either less or more "manganese in its composition. Vhen rapidly cooled the deposited metal is much more resistant to mechanical stresses of all kinds than is a metal containing either substantially lower or higher percentages of manganese. hereinbefore referred to has been eliminated in the metal containing 0.45% manganese, rendering the deposit very tenacious at all temperatures.

As an example of atypical analysis for the core metal, the following may be given as one which is suitable for a No. 10 gauge electrode: Per cent Iron"; m. 96.52 Carbon 0.09 Manganese 3.12 Silicon 0.23 Sulphur 0.03 Phosphorus 0.01

The core metal is preferably used with a flux covering consisting of blue asbestos yarn with an added wire or strip of aluminium as set forth in the specification of Patent No.

Apparently the brittle zone- 1,144,390 granted to me on June 29th 1915. This gives the best conditions for protecting the fused metal in the arc from oxidation and unnecessary loss. According to this, invention therefore the electrodes are made of a core metal having the percentage content of manganese indicated above with regard to the gauge required, the core metal having applied to it or used with it a suitable fluxor slag-forming material preferably such as that set forth in the said Patent No. 1,144,390. The carbon content of'the manganese steel core must below, but the silicon content may be considerable as already indicated.

Although I have stated the critical percentage of manganese in the deposited metal as being 0.45%, it is to be understood that slight departures from'this percentage are possible while obtaining substantially the advantages of the invention. The nearer this percentage is approached by the use of the appropriate higher percentage of manganese in the core metal, the better will be the result. The core metal may contain small percentages of other alloying metals such as tungsten, molybdenum and chromium in addition to the manganese, for the purpose of imparting to the deposited metal other characteristics which these metals will give, and while still obtaining the results hereinbefore set forth which follow from the percentage of manganese used.

Having thus described my invention what I claim as new, and desire to secure by Letters Patent, is

An electrode for use in depositing metal by the electric arc process having a ferrous core and a flux-forming covering adapted to form a protective slag when fused, said core containing a quantity of manganese dependent upon its diameter and varying inversely as the diameter from 2.25% to 4.0% for cross sections of electrode cores from 0.042 to 0.005

iquare inches, asand for the purpose set orth. i

In witness whereof I hereunto subscribev my name this 3rd day of January, A. D." 1929.

ARTHUR PERCY STROHMENGER.

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