011 yeara the users of steam boilers liart5 encountered s peculiar difficulty in the form of rriicks iii the riveted areas of the boilers, as illustrated i n Figures 1 and 2 . 13ecanee the fracture resembled that of a brit.tle metal (Figure 3) more than that of a normal ductile hider plate, it was ,said that the plate had become emhrittled. Later it, he cam^ evident that, this cracking was confined to a condition OS wader supply and operation of the boiler which brought about the presence of sodium hydroxide i n the boiler. The sodiuni carhonatc iii the feed water Iireaks driwii i n the hoilcr
Figure l---Emhrlftled Drum
or the disinterested vliarixter OS the experiirient;tl results
obtained. It is rather mifort,uiii~t,cthat t,he use of the terxi "enhrittlement" had to be continued in this investigation, bnte since it has been already firmly est,ablished it was realized that the issue w(~nldonly become confused by bhe introduction of a new term. Fortunntely, tlie data which had been assembled previous t,o this investigatiou showed t.hat t,hese cracks possessed one characteristic which differentiated t,liem from all other t.ypes of boiler failures-namely, that, they were interrrystalline, as shown in Figure 4. In view of this it woold be well for us to emphasize a t this time that, the term "emhritt.lement of hoiler plat,e" as used here is nieant a condition which is indicnted by iiitercrystalline crac,king i n t,hc rivetcd areas. This type of faihlre in iion-ferrous liietalP such as hrars, hronee, aluminum alloy^, etc., has not been uncommon m d has been traced to t,he presence of high residual stresses from cold work accompanied by a mild corrosi7.e agent.' I~itcrcrystalline failure has also occurred io higli-carbon steels which hare been suddenly cooled so as to retain the :iustenitic structure accompanied by enorniou residual stresses. The occrirrence of this peculiar type of cracking in mild steel such as used in boilers has been rery limited. Attempts made io reproduce it by excessive loads working over a period of years at temperatures encoiiiitered iir boiler operatioil have been i~nsuocessful.~ Low-carbon steels wacked by fatigire its well as by fatigue accompanied by nxygen corrosion show the regihr transcrystalline failure (Figure 5 ) which is nonnal to this kind of r n e t , ~ l . ~
to gii-e sodiiiiii liydronidc and libcrateti thc carbon dioxide xitli thc steam. The fact that concentrated sodium hydroxide at temperatures encount.ered in boiler operatioil at,tacks iron with the evolution of hydrogen, coupled with t.he kirmhige that hydrogen generated in contact with iron ~'ansesthe metal to lose it,s ductilit,y, led the industry to say that hydrogen had emhrittled these boilers. Consequently, tlie term "enibrittlement of boiler plate," meaning a loss in duebility caused apparently by hydrogen as a product of mustic artion, came into general use to describe this phenomenon. Thosc mho were not satisfied that this cracking wits confined to boilers operating with excessive sodium hydroxide contended t,hat it was brought about by poor metal: excessive cold work, too high a riveting pressure, high temperature differeiitials in the seams, improper design of boiler, etc. The present imvcstigation, which is still going on, was iindcrtitken by the Engineering Experiment Station of the University of Illinois, in cooperation with a group of public Figvre 2-Embrittled Blow-Off Flange utilities of the Middle West for the purpose of obtaining information of general interest to all, whether concerned By nieans of extreme cold work, whether or iiot followed with the production of power, the fabrication of boilers, by heating, the ductility of the boiler plate is lowered and or the treatment of water. Both in the assembling of the metal becomes brittle hut cracks transcrystalline. This information and in the acquiring of experimental data, an type of brittleness is often confused with emhrittlement; attempt has been made to follow methods which would hence the definition that has been suggested. avoid any question as to the authenticity of the findings B B d t Brit. No"-FrrrourM~loisR~srorch Arroc., No.66. 11 (July. 1922). * Rorenhain, private eommunication. I Received March 17, 1927. Presentcd before the Division of Water. * Lucsr, "Microstructure of Fntipue Cracks," Trans. A m . SOC. S l c d Sexage, and Sanitation Chcmiatry at the 73rd Meeting ot the Amencan Chemicsl Society. Richmond, Va.. A p d I I to 16. 1'127~
I'rmiing, lSP6; MeAdnm. "Corrosion Fatigue of Metals,'' I b i d . . 1916.
produce sudimn liydrmido. There seems to be sufficient evidence tu indicltte that the hydroxide slowly concentrates in the srnall crevices of the seams.# 'Ih s h i n e d areas in these seams, in contact with tiie conccntr:ited liydroxidc, will become einbrittled. If the sulfate is high eilough it will prweiit this einbrittling action. Prevention of Ernhrittlement
i d o r e trent,tiient to keep the required ratio witll tliis W.iti>ryIMYC h n v n t/i:tt for yressiircs up to 150 poiinds ilio roeornincirtl~il r:r,t,ios linve stopped tiie rraeking. Tests iww uiidcr w i ~ y iiiiliciLtc timt :ill the ratios recotii~nc~ided:we snfe. reiuIt,s drove 500 pound pmssiirc are yet av:d:tble. In :wi mirlier publication of tlie resu1f.s of this in refercimc ww made to the fact t,lint sodiiirn earbrin;~teillso P i ~ u r e6--Circles Show Areas in Which Boilers Using Well Waters liavc Seen E m b r i t f k d inhilrited einlirittlcinent, arid it was statcri dliiit. ilie niidceoinpoxed sodium oarboilate tends i o retard tlie einbrittling Wlien the acolitc systerri is used, the calcium atid mageffect. In,2sniuelt as a t higher steam pressures the per- iiesiiitn bicarhontti.e are changed to sodinrn Iiiear1,onate and centage or ondecomposed carbonate becomes very sinall, the sulfates to sodium sulf:Lte. If the carbonate hardness and sirice we have riot at present any inforrnation whinli i)redominates the treated water will he higher in sodium will help lis to ret.niii the earhonate as such in tlie boiler, carbonate t,bm in sulfate. W l i e n the riitios :ire not as tlic rct.arding action of tlie earboiinte has rio real value in recommended tho iisual procedure lias been to acid-treat general boiler operat.ion. The only snfe n i l e to Sollow is the treated wtitcr until the desired rat,io is ohtaii:ed. the A. S. M. 13, code reeoinmcridati~,lr, wliic+i recognizes Wlien rttit,riral waters having free sodium carbonate aiid all c:irt.wiiate uf soda :is potroiial Iiydriixidc. low siilhte are to be used, they are usually treated by lime aiid then ~:ilougIisulfuric acid to maintain the desired ratio. or hy lime atid aluminum or iron sulfate. In :ill cases care must, be taken riot ti, overtreat with the acid or sulfate salts.
Calendar of Meetings American Chemical Society---i.ith Meeting, I)etroil, hlicli., S q trmbcr , i to 10, 192i. Midwest Regional meeting^ --Chicago,I11 Iily 27and 28, 1927. Division of Colloid Chemistry -Fiith tional Colloid Symposiuin, Ilniversity oi Michigan, Ann Arbor, Micl>., Juric 22 to 24, 1 a i . Institute of Chemistry, Stntc College, Pa., July 4 to 3 0 , I!W. Second National Symposium on Organic Chernistry~-~Culumbi,s, Ohio, Ikccmbrr 39 to 3 1 , l!i27. American Oil Chemists' Society--Aniinnl Convtntion, New Orlenns, La., May 9 m d 10, 1 W i . American Refractories Institute---Spring Sleeting, Atlantic City, S . J., M a y 18 and 19, 192i. American Association of Cereal Chemists .-..1:3th Arinual X e u l ing, Hotcl Fontencllc, Oinaha, br., M a y 3 0 t u June 3 , 1!127. American Institute of Chemical Engineers . -Clcvel;nid, Ohio, M a y :ll to J u m 3, 1!127. First International Congress of Soil Science-\iVasliiiislon, I). C., Jtmc 13 to Z2, 1!i27. American Leather Chemists' Association Cinciniiati, Ohio, June 1 5 to 17, 1927. American Electrochemical Society---Fall Meeting in the iorni oi an errursioii through the Xorthwnst, September 4 to 20, 11)Zi. 11th Annual Exposition of Chemical Industries-Graiid Central Palace, S r w York, N. P., Septcmbcr 20 to October I,I ! Y T
.
Pieure 5---Fati!Aue Crack Armco Iron.
3SOX
By adheririg to this rccoiriiiieridi~tioii,it bocmies y r y easy to tell whether the aater in use will nrt:ct tlir requirements aft,er any system of water tre:ttincnt,. The lime-soda process u ~ i i a l l ~rcquiras . tlie xoda :wli 1.n be carried about 2.0 grains in excess. If the kulfate content is high enoiigli Baumvn and Thiele, Iiandbiich fui Spuiscrisier-pflege, 1922,
