Lafitte Welding Plate:

The Lafitte process was first heard of in 1905 (Iron Age May 11, 1905). It may be described as the handy application of a patent fluxing sheet between parts to be welded, and can only be used for joining iron and steel. The flux is sold as a plate, size 4 x 8 inches and about 1/16 inch thick. The plate is composed of a preparation of calcined borax and iron filings, molded over a sheet of wire gauze. The gauze is about 15 meshes to the inch in length. The iron wire is low-carbon (0.08 % by color determination (Specially analyzed).

The pieces to be welded are brought to the welding heat and forced together with a Lafitte plate between the contacts. As with all smith-welding, one of the contact surfaces should be decidedly convex, so that the point of it is first brought to bear on about the middle of the other contact surface. As the two surfaces are forced together, with the plate between, the borax melts and flows out, fluxing both surfaces as it flows. The iron gauze, which is inside the plate, is also partly melted and welds itself in place on both surfaces. It is likely that the strength of the Lafitte weld is a much due to the binding action of this low-carbon iron wire as it is to the complete fluxing of the borax. If properly done, the weld should be flawless. It is not necessary to use more of the plate then will cover both surfaces. The plate can be cut with ordinary shears.

From tests made it is claimed that the Lafitte weld is as strong as the metal, in case soft steel is welded; but the in high-carbon steel there is a slight lowering of the elongation and tensile strength (due no doubt to the reheating of a specialy treated product).

In all but on of these tests the tensile strength is greater for the Lafitte weld than for the body of the stock, which may indicate than an upset of metal was crowded in tot he weld by the pressure of welding; while with cast steel the quality of the metal might be improved by the pressure.

Hard Steel Test Mn, 1.35; C,0.45; S, 0.045; P,0.083; Si, 0.08

Tensile strength kg. Before welding Lafitte weld Common Weld 70 63.6 55.9 Elongation, per cent. 15.3 10.0 11.7 2.5

Test by the French Government - (Toulon Arsenal)

anvilfire.com Tensile Strength, lbs Elongation per cent Before Special Compound Lafitte Before Special Compound Lafitte Iron on Iron 48,700 44,729 48,938 16.33 9.66 14.33 Iron on soft steel 48,700 43,964 45,631 16.33 4.- 4.- Steel on soft steel 75,935 72,197 80,500 2.- 1.- 2.- Iron on Cast Steel 75,935 43,719 78,692 2.- 3.25 9.05 Cast steel on cast steel 95,030 92,712 102,711 5.62 3.- 5.-

The Lafitte method may suggest itself for stock welds, such as the joining of axel parts and in chain making; in other words, in instances of multiple welding, the the pressure machinery is handy. It is most used in France and Germany.

• Alphabet Soup What's that acronym?

• MACHINERY'S HANDBOOK, Industrial Press

2009 Jock Dempsey, www.anvilfire.com