. Transactions. far the mostof the work was centered on nickel steels, since these are largely usedin ordnance and the writer early in the work came to the conclusion thathe was dealing with an effect similar to erosion. Also, nickel steelscan be treated above their critical change at temperatures low enough tobe practicable with ammonia. Nickel Steels.—First sample (Bar Xo. 4011-8), a per cent. per cent. Ni steel with an Ari point at 605° C. and an Aci point. Fig. 20.—Bar Xo. 4011-8. Nickel steel per cent. C, per cent. Ni-Treated 12 hr. in NH? at 650° C. Etched 15 sec. w
. Transactions. far the mostof the work was centered on nickel steels, since these are largely usedin ordnance and the writer early in the work came to the conclusion thathe was dealing with an effect similar to erosion. Also, nickel steelscan be treated above their critical change at temperatures low enough tobe practicable with ammonia. Nickel Steels.—First sample (Bar Xo. 4011-8), a per cent. per cent. Ni steel with an Ari point at 605° C. and an Aci point. Fig. 20.—Bar Xo. 4011-8. Nickel steel per cent. C, per cent. Ni-Treated 12 hr. in NH? at 650° C. Etched 15 sec. with 4 per cent, nitric acidX 50. Below critical change; center not affected. at 705° C. Treated for a few hours in NHs at 650° C, it showed a whitezone at the surface but the center structure was unchanged as in Fig. piece of the same metal was heated first to 850° C, cooled to650° C, and then treated 12 hr. in ammonia. The edge effect was muchdeeper and graded off into martensite, as shown in Fig. 21. The centerstructure was changed, as shown in Fig. 22. Repolishing and etchingwith a copper-bearing reagent gives the reverse, as shown in Fig. 23. VOL. Lxvn. — IS 274 XITROGEN IX STEEL AND THE EROSION OF GUNS 1 llp =1! m 1 ^ w ^^.M 9^^^JH9I srCr:, in i r^ m^ ^^^^^^ m 1^^ w ^;4 ,i ft IJ^^PI E30 ^■^^■l^^fi^^K^^^M ^1 Pr Fig. 21.—Same sample as ix Fig. 20 treated 12 hr. in XHs at 650° C; first HEATED TO 850° C. ShOWS MARTEXSITE BETWEEN OUTER
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
