Nickel steel welds readily at all compositions. Nickel is a valuable addition to iron, because small percentages of it greatly increase the tensile strength without impairing the elasticity. It is also valuable because it prevents rust in its iron alloys to a marked degree. Nickel steels of from 2.05 to 4.95 per cent nickel are specifically mentioned as weldable if the carbon is kept down.1

Chrome steel2 can be welded. The first hammering must be very gentle so that the metal will not fly to pieces.

Aluminum

There is some uncertainty about the effect of small quantities in iron. In amounts above 3 per cent it forms a valuable alloy with steel, which is highly fluid on melting. 0.50 per cent increases the tensile strength and elastic limits from 3000 to 8000 pounds and lessens the ductility.3 Odel-stjerna4 says that only 0.002 aluminum gives inferior steel castings, the fracture being coarsely crystalline.

A serious count against aluminum, if it be true, is that it oxidizes in its alloys and coats them with a skin. This would seriously affect the welding, because this skin is a very refractory, unmanagable substance. Reliable data are wanting.

Copper is generally believed to be harmful in malleable iron. However Campbell5 in his welding experiments used bars containing 0.35 per cent, with excellent results. He says: "The critical temperature at which the steel ceases to be malleable and weldable varies with every steel. It is lower with each associated increment of copper; it is higher with each unit of manganese, and it is lower in steel that has been cast too hot."

Arsenic steel, with less than 0.20 per cent arsenic will weld as usual. Between o. 20 and 1.20 per cent a flux of borax and sal ammoniac is needed. 2.75 per cent arsenic prevents welding altogether, and the iron behaves like pig iron.6 Campbell7 claims that so small an amount as 0.093 impairs the welding property.

l Iron Age, July 25, 1905.

2 R. Brown, Journal of the Iron and Steel Institute, 1896, Vol. I, p. 4723 "Metallurgy of Iron and Steel," Wm. Campbell, p. 477.

4 Transactions American Institute Mining Engineers, Vol. XXIV, p. 312.

5 "Metallurgy of Iron and Steel," p. 467.

6 Iron Age, April 13, 1899.

7 "Metallurgy of Iron and Steel," p. 478.

He says that o. 20 per cent, of arsenic increases the strength and reduces toughness.

Nitrogen content is not a subject for the smith to bother about. Nitrogen has been blamed recently for otherwise unaccountable failures of chemically good iron. E. J. Sjostedt1 claims that infinitesimal quantities of it cause red and yellow shortness. He claims that a furnace producing trisilicate slag gave iron with 0.003 per cent nitrogen; bisilicate slag, 0.016 per cent nitrogen; monosilicate slag, .024 per cent nitrogen. 0.006 per cent, he says, is the limit for good steel and, presumably, for good welding steel.

However, there is at present no easy way of recognizing its presence, and it cannot be guarded against.

Tests Of Smith Welds

Campbell made a series of tests of smithed welds of all of the different kinds of steel and of wrought iron, the results of which are given in tabulated form in his "Metallurgy of Iron and Steel." Four smiths of ability and experience welded the metal in flats and rounds of size and shape most convenient for handling. And though the men knew their bars would be tested, their welds were often far from satisfactory. "Picking out the worst individual weld of each workman, blacksmith 'A' obtained only 70 per cent, of the value of the original bar, 'B' 54 per cent., 'C 58 per cent., and 'D' only 44 per cent. The forging steel showed one weld with only 48 per cent., the common soft steel 44 per cent., while even the pure basic steel gave one test as low as 59 per cent."

But the, tensile strengths of the bars are fairly uniform when compared with the elongation. "In some cases where the break took place away from the weld, the elongation was nearly up to the standard." The elongation test of a basic open-hearth steel of low carbon gave greater elongation in welded pieces than in the natural bar; "but in the other pieces the stretch was low and the fracture so silvery that it was plain the structure of the bar had been ruined. In most cases where the test bar broke in the weld, the pieces parted at the surfaces of contact, showing that no true union had taken place; one or two fractures were homogeneous, but they showed the coarse crystallization that follows overheating." 2

1 Iron Age, May 5, 1904.

2 "Metallurgy of Iron and Steel," Wm. Campbell.

Welding Tests Of The Royal Prussian Testing Institute 1

These results agree substantially with those of Campbell. The lowest result for soft steel was 33 per cent., the average 71.

The lowest result for medium steel was 23 per cent., the average 58.

The lowest result for puddled iron was 62 per cent., the average 81.

These results confirm the general impression that puddled iron is the best iron for welding. Contrary to one authority who says that iron before puddling welds more easily because of the presence of the slag in the iron.

The welding test2 is occasionally specified in this country on account of the common use of welds in structural work. Two iron bars of the metal under test, of about 1 inch section, are scarfed, heated to white heat, and joined without flux. The joint is worked with an 8- or 10-pound hammer, and brought down to unit section. It is cooled without chilling. This bar is then tested for tensile and elastic strength; and a similar weld is half cut open, bent until fractured, and examined for structure.

Results Of Tests By Prof. Bauschinger

1 Journal of the Iron and Steel Institute, Vol. I, 1883, p. 425.

2 Transaction of the American Institute Mining Engineers, Vol. II, p. 628.