US2017488A - Arc welding electrode - Google Patents

Description

Patented Oct. 15, 1935 UNITED STATES ARC WELDING ELECTRODE Lionel E. Faulkner, Hillside, N. J., assignor to Wilson Welder & Metals Company,

Hoboken, N. 3., a corporation of New York No Drawing. Application March 3, 1934, Serial No. 713,881 I 8 Claims. (e1, 219-s)- This invention relates to electrodes for metallic-arc welding, and more particularly to that type of welding electrodes, having a relatively thick coating, which are used in the so-called shielded-arc process.

Coated electrodes are usually in the form of I a short length of metal rod or wire to which the coating has been applied by any suitable process, such as by extrusion through a die or by dipl0 ping. In use, the arc is struck between the metal rod and the work, the rod melting in the heat of the arc and being deposited on the work. The coating usually contains suitable fluxing, deoxidizing and slag-forming materials, together with a binder to make them adhere together and tothe rod, for reasons well understoodin. the art. The advantages of this type of electrode may briefly be stated' to be: (1) an increased rate of deposit by permitting the use ofa higher ourrent, (2) avoidance of a so-called wild arc,

(3) decrease of .spattering, (4) better penetra-' tionof the work by the. deposited metal, (5)

greater density and homogeneity of deposited metal with avoidance of pinholes, and (6) generally improved quality and strength of the weld.

Such coatings are either melted or consumed by the intense heat of the arc, depending upon their ingredients, some of which may be combustible. The weld is improved because the coating is so constituted as to form a shield around the end of the rod as it melts so .that the arc is projected from a crucible resulting from the consumption of the rod more rapidly than the coating, the coating which projects beyondthe end of the rod helping to protect the molten metal from contact with the air. As the coatingis melted and consumed, the noncombustible constituents cover the surface of the deposited metal with slag. This slag cover protects the metal while molten from the harmful effects of the air, to which it is susceptible while in the fluid state, and prevents the formation of scale after the metal solidifies and before it has cooled. It also slows the cooling of the deposited metal.

Many heavily coated electrodes present the difliculty of leaving a deposit of too much slag,

which runs intothe arc, particularlywhen the weld is being made in positions other than horizontal. This may cause the arc to go out and may cause a fault in the weld. Moreover when the arc is extinguished the slag may seal over the end of the electrode, forming an insulation which must be broken off before the arc canbe startedagain.

By this invention new and improved electrode coatings are provided which furnish the correct'amount of shield without an excess of slag. 5 The coatings hereinafter described are characterized by the fact that they contain, among their ingredients, pyro'genous residues, particularly pitches and asphaltites, the latter being native pyrogenous substances. As to pitches, 10 excellent results have been obtained using pitches derived from the destructive distillation of wood, fatty-acid pitches, and coal-tar pitches. As an example of an asphaltite, gilsonite has given good results. Hardwood-tar pitch has 15 been found especially well suited for the purpose. An example of a formula for a coating, using hardwood-tar pitch, is as follows:

Parts by Ingredientweight.

China clay 20 Powdered. asbestos 20 White serecite mica 35 Pumice 10 Hardwood-tar pitch l0 'Silico manganese 18 Iron oxide -(FezO4 20 to which is added about 43 parts by weight of sodium silicate (NazO SiO2 ratio 1 to 3.22) of 30 about 40-42" Baum to make the mixture-into the consistency of dough for extruding. The dry materials arefinely ground before mixing. The coating as above prepared is extruded. through a die onto a bare wire of about .156 35 inch diameter, the coated rod being about .190

inch diameter. A rod of .187 inch diameter would be coated to .240 inch diameter. These coating sizes may be varied, however, to make the rods suitable for various types of work. 40 An example of a formula for a coating using gilsonite, an asphaltite, is:

T0 the above are addedabout parts by weight 56 or gum arabic.

coating is to mix the dry ingredients, including pitch used, for example, has a flow point of about 85 C., but the flow point is not significant except as it is such as to permit the pitch to be pulverized.

While these formulae are given as examples of coatingswhich produce highly satisfactory results, the invention is not limited to the ingredients or proportions specified. The quantity of pitch or asphaltite in particular may be varied in order to increase or decrease the relative amount of the coating which is consumed by the heat of the arc and to correspondingly decrease or increase the relative amount of slag-forming material in the coating, while retaining the desired shield for the are. To maintain the proper thickness of shield without an excessive deposit of slag is very desirable, particularly when welding. in positions other than flat, that is, in vertical or overhead welding. This invention contemplates that the amount of pitch or asphaltite may be varied from the amounts given. in the above formula within wide limits. For example, in the first formula set forth above the amountof hardwood tar pitch-may readily be doubled, with only slight adjustment of the quantities of the other ingredients in the coating to maintain the proper consistency of coatingmiaterial and of the slag produced in the are. It will be noted that by reason of the relatively low specific gravity of the pitch etc., doubling the weight of pitch given in the illustrative formula will result in a relatively larger increase in the volume of combus-' tible material in the coating.

Binders other than sodium silicate may be used, for example, potassium silicate, glue, dextrine paste or vegetable gum such as gum tragacanth Another method of applying the the pitch or asphaltite, and heat the mixture to the melting point of the pitch or asphaltite, applying it to the rod while in that condition and allowing it to cool.

The foregoing description is illustrative of several embodiments of the invention, which is. not

intended to be limited thereby.

What is claimed is:

1. An arc welding electrode comprising a metallic rod having a coating of fiuxing, deoxidizing, and slag-forming materials, including a quantity of a pyro enous residue of organic materials incorporated in said coating and proportioned in and slag-forming materials, including aquantity of a pitch incorporated in said coating and proportioned in amount relative to the other ingredients so that the coating will produce in the heat of the arc the desired amount of slag while maintaining a shield for the arc.

3. An arc welding electrode comprising a metallic rod having a coating of fiuxing, deoxidizing,

and slag-forming materials, including a quantity of an asphaltite incorporated in said coating and proportioned in amount relative to the other in-' gredients so that the coating will produce in the heat of the arc the desired amountof slag while maintaining a shield for the arc.

- 4. An arc welding electrode comprising a metallic rod having a coating of fiuxing, deoxidizing, and slag-forming materials, including a quantity of gilsonite incorporated in said coating and proportioned in amount relative to the other ingredients so that the coating will produce in the heat of the arc the desired amount of slag while maintaining ashield for the arc..

5. An arc welding electrode comprising a metallic rod having a-coating of fiuxing, deoxidizing, and slag-formingmaterials, including a quantity of coal-tar pitch incorporated in said coating and proportioned in amount relative to the other ingredients so that the coating will produce in the heat of the arc the desired amount of slag while maintaining a shield for the arc.

6. An arc welding electrode comprising a metallic rod having a coating of fiuxing, deoxidizing and slag-forming materials, including a quantity of a fatty-acid pitch incorporated in said coating and proportioned in amount relative to the other ingredients so that the coating will produce in the heatof the arc the desired amount of slag while maintaining a. shield for the arc.

7. An arc welding-electrode comprising a. me-' tallic rod having a coating of fiuxing, deoxidizing, and slag-forming materials, including a quantity of a wood-tar pitch incorporated in said coating and proportioned in amount relative to the other ingredients so that the coating will produce in the heat of the arc the desired amount of slag while maintaining a shield for the arc.

.8. An arc welding electrode comprising a metallic rod having a coating of fiuxing, deoxidizing, and slag-forming materials, including a quantity of hardwood-tar pitch incorporated in said coating and proportioned in amount relative to the other ingredients so that the coating will produce in the heat of the arc the desired amount 01' slag while maintaining a shield for the arc.

LIONEL E. FAULKNER.