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Aviation History
1914
1914 - 1140.PDF
[/OCHTj NOVEMBER 20, 1914. the suitability of a steel for use in the construction of a particular part vary to a great extent: in fact, so much is this the case that a material that is eminently adapted, after being correctly heat-treated for one part, may be entirely wrong for another if used in the same condition. No one grade of steel possesses to the maximum extent all the qualities which would be necessary in order that it may be indiscriminately used, neither is such actually desired. But while this is so, much can be done by 40 60 to 70 YIELD POINT (Tons per Sf In.) fin Diagram showing the effect of heat treatment upon the mechanical properties of Firth's nickel chrome steel. subjecting the steel to suitable heat treatments, which, by bringing out the properties of a steel susceptible to them in a marked manner, render it possible to employ one kind of steel for a variety of purposes for each of which it is specially suited. This is shown by inspection of the tables, as the figures quoted as obtainable in the heat- treated condition do not represent limiting values, but are those which can be obtained from a particular heat treatment. Full information as to what this treatment is and how it can be varied will be supplied by Messrs. Firth and Sons to prospective customers. ® ® " News " Made in Germany, MR. FREDERIC W. WIT.E, in his interesting article " Germany day by day," in the Daily Mail, on the 9th inst., had the following " news " : — " The Cologne Gazette of November 6th publishes as the latest and most important intelligence of the day an account headed : "BOMBS THROWN ON DOVER. " This highly exclusive information reads: " * As communications from the field inform us, a German war- We are able, however, in the accompanying graph, where the various mechanical properties are plotted against the yield point, to show the effect of the range of heat treatments upon Firth's nickel chrome steel. The yield point has been selected in preference to the ulti mate tensile strength, as the latter is of comparatively secondary importance in considering the strength of the material to resist fracture. For example, given two steels, one of 60 tons and the other of 50 tons ultimate tensile strength, the respective yield points being 35 and 40 tons respectively, the latter would be much preferable from strength considerations alone, because a stress of 36 tons which would permanently deform the former and probably ultimately cause fracture would not injure the latter in any way. It will be seen from the diagram that where the toughness, hardness, high resistance to fatigue and shock, and a high tensile strength are all desired, as for crankshafts, this nickel chrome steel, suitably heat treated so as to give a yield point of about 60 tons per sq. in., should prove highly satisfactory. TABLE I.—Steels for Aeroplanes. Grade T. of Steel. Porm- C.N. 1 Sheets F.M.S N.S. 2S „ ( F.A.S. Bar I F.S.S.... „ C.JV. 5* Bar ... TA Grade of Steel. Nickel chrome Chrome vanadium 5 per cent, nickel 3 W i» 25 >> »» Mesmeric* Crucible nickel* Condition. Annealed ... Heat treated Annealed As rolled Heat treated Annealed Heat treated »> Annealed Heat treated i» Case hardened c C ui s| ^ 29 35 18 36-6 28 30 45 70 26 49 105 99 A> m ateTens i ss. T o sq. in . gSs 35 40 26 52-6 42-9 40 55 90 44 55 129 49-88 BLE II.—Steels for Motors, Sfc. .5 "> 2g ••• 35 f 36-40 \ 75-47 1 32 \ 55-15 i 31 \ 60-SS ... 15 ... — ... — teTensil e s. Ton s q. in . 45 50-60 78-21 42 63-42 44 66-15 40 43-57 49-88 " Freedom " "50 ton " 26-32 <5o tio n o n pe r cent . C 0* W 24 20-l6 15-76 26 19 26" s 17-76 51 26-5 22 20-16 ion o f pe r cent . 6O 55-45 47-15 61 54-6 56 56-95 70 5°'95 60 45-30 h c .2 Me 0 0 W 24 26 3° 20 34'5 27 22 12 30 23 io-S 22 (A V & 26-27 82-84 52-50 60-65 50-49 — 44 54 +z tio n o f 1 pe r ce n 3 a "8< 35 40 4° 23'3 37-9 65 64 34 6S 63 34 60 a . gi (A c v •£ C K 192 807-255 340 179 280 187 30-' 134 — * These steels are case-hardening, and the tests recorded were made on the core of treated specimens after the removal of the outer surface. NOTE. — Test results in italics have been obtained after oil-hardening or other heat treatment. ® ® plane attached to the troops operating in Northern France (pilot, Reserve Lieutenant Caspar, of the 5th Dragoons, with Lieutenant Roos, of the 75th Infantry, as observer), flew the Channel on October 26th, and dropped two bombs north of Dover. After a 5J-hour flight the aeroplane returned safely to its base.' " Other details of the same exploit are supplied to the Frankische Zeitung by an officer in the field, as follows : " ' Last night we had a jolly celebration. We were guests of a flying battalion which was welcoming two of our airmen on their return from London. These officers have thrown bombs on Dover.'" I I40
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