252 



Copper and Copper-base Alloys 



be applied either as a dry powder or preferably, as an 

 alcoholic paste to the base metal and/or the filler rod. 

 Water contained in any fluxing ingredient wUl volatilize 

 as steam and maj^ be trapped as porosity in the rapidly 

 freezing weld metal. 



rUler-rod diameters are chosen so that the melting 

 of an inch of filler rod per inch of seam will provide 

 sufficient filler metal to deposit a layer of J^-inch thick- 

 ness. Thicker layers or passes are to be avoided as they 



Bead sequence 

 in vee 



Complete weld 

 bead requirements 



approx.g aper- 

 iure 



Fig. 1. — Chart of recommended carbon-arc-welding procedure for 

 silicon bronzes, single V welds, ^'fg- to 5^-in. plate, according to Bunn, 

 Hunter, and Seidlitz.^^^' 



may interfere with the welder's ability to ascertain when 

 fusion and blending have been obtained. Recom- 

 mended filler-rod sizes for various thicknesses, as well 

 as base-metal preparation, if any, are indicated in 

 Table 4 and Figs. 1 and 2. 



The use of the more expensive oxyacetylene method of 

 welding is more or less confined to joining the medium 

 and heavy gages of material. Joint setups employed 

 are the same as those employed for the carbon-arc 

 method; the seams are, however, run as free welds, a 

 tapered aperture of approximately ^fg inch being desir- 

 able to aUow for contraction of the weld metal. The 

 oxyacetylene flame is less intense and the rate of heat 

 flow considerably less than the carbon-arc method. 

 Cooling of the weld is, therefore, much slower and it is 

 necessary in order to prevent cracking to begin welding 



at some point P, 4 to 6 inches from one end of the seam 

 and run to the nearest end. After this section has cooled 

 to a black heat, welding may be started again at P and 

 the seam run to the other end. Tip sizes and filler-rod 

 diameters are essentially the same as employed for the 

 same gage of steel. The flame should be neutral to 

 slightly oxidizing — definitely not reducing. The use of 

 a flux, either in the powder form or applied as a water 

 paste to the base metal and the filler rod, is essential. 



Bead sequence 

 in vee 



Complete weld 

 qI bead requirements 



Lip edges 

 sefupin U- 

 HghibuH ~ 



Fig. 2. — Chart of recommended carbon-arc procedure for silicon 

 bronzes, double V welds, }/%- to 1-in. plate, according to Bunn, Hunter, 



and Seidlitz.'"' 



Proprietary fluxes are available, or a satisfactory flux 

 may be made up of boric acid (85 to 90 per cent) and 

 borax (10 to 15 per cent). 



The metal-arc method has found little application 

 except as a method of depositing bronze overlays on 

 steel for wear surfaces. There are to date no completely 

 satisfactory coated electrodes available. Metal-arc 

 welding with bare electrodes is characterized by globular, 

 intermittent, and somewhat wild transfer of metal across 

 the arc, necessitating maintenance of a comparatively 

 large well pool if any measure of control is to be main- 

 tained. In the lighter gages it is necessary to deposit 

 an unduly large bead if cross-bead checks are to be 

 avoided. Welds executed by this method wiU not, in 

 general, compare with those executed by either the 

 carbon-arc or oxyacetylene methods. 



