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WHEELER—A HIGH-TEMPERATURE BOLTING MATERIAL 657T A B LE 2T A B L E 3C O M PO S IT IO N A N D H E A T -T R E A T M E N T OF C R E E PS P E C IM E N SPH Y SICA L P R O P E R T IE S A T 70 F O F S P E C IM E N SB E FO R E A ND A F T E R C R E E P T E STT A B LE 4C R E E P -T E S T R ESU LTS(All stresses in pounds per square inch)creep specimen shows an apparent increase in ferritic areas due tocarbide spheroidization and migration of carbon to the grainboundaries, resulting in considerable loss in the initially lowCharpy strength.It is recognized that creep strength falls off as the quenchingrate increases, but the Charpy impact strength increased with thehigher quenching rate. The oil-quenched treatment finallyselected for commercial bolting is a compromise between creepstrength and Charpy impact strength, sacrificing slightly in creepstrength to provide much greater impact strength and, in addition,greater structural stability.R u p t u r e T e s t sLong-time rupture tests3 were made at 900 and 1000 F on materiallike creep-test item No. 866, which had been oil-quenchedand drawn. In running a long-time rupture test, a series of barsis pulled at successively lower stress, and periods of sojourn athigh temperature, required to cause failure, are plotted on log-logpaper to enable prediction of a long-time strength. At 900 F,the fractures were always transcrystalline, the longest time forfracture being about 5000 hr under 60,000-psi stress. At 1000 F,the fractures were transcrystalline up to 1200 hr, with the firstintercrystalline failure occurring at 3400 hr.Comparative tests made on normalized material, like creep-testitem No. 864, showed transcrystalline failure up to 140 hr andintercrystalline failure at 310 hr.These rupture tests are conducted like regular constant-stresscreep tests so that elongation-time plots, as well as stress-timeplots, can be made.Plotted results of rupture tests at 900 F on oil-quenched anddrawn material are shown in Fig. 19 and at 1000 F in Fig. 20.Results of rupture tests on normalized material at 1000 F areshown in Fig. 21.'F i g .'” 8 ^ D il a t a t io n C u r v e S h o w in g L in e a r C h a n g e U n d e rH e a t in g a n d C o o l in g(Specimen heated in 1 hr tto maxim um tem perature, held 1 hr, th en furnacecooledat 240 F per hr. Chemical composition: 0.45 C, 0.99 Cr, 0.45 Mo,o.ae y, o.ei Mn, 0.32 s uC o r r e l a t io n o f C r e e p a n d R u p t u r e T e s t sFig. 22 shows the results of creep and rupture tests in relationto each other, comparing the creep rate of 1 per cent per 100,000hr to the 100,000-hr rupture strength, as determined by extrapolationof the observed data. Structural changes in the materialbeyond the time of longest test may change the results butthat is a m atter of conjecture. It will be noted that the ratiobetween creep strength and rupture strength is greater in the caseof the normalized material than for the oil-quenched material, butthis is quite possible because of structural difference and is ametallurgical phenomenon which is hard to explain at the presenttime.After a larger number of comparative creep and rupture testshave been made, perhaps something more definite can be determinedin this creep-rupture relationship, but it is the belief of theauthor that changes of heat-treatment, differences in meltingpractice, and even slight changes in some alloying elements in thecomposition, will greatly affect the ratio of creep strength torupture strength.H a r d n e s s T e s t sTests were made to determine the effect of time and temperatureon the hardness of chromium-molybdenum-vanadium boltmaterial. The composition of the bar tested was carbon 0.45,chromium 0.98, molybdenum 0.35, vanadium 0.27, manganese0.57, and silicon 0.28.3 For a more complete description of methods of running long-timsrupture tests refer to “ The Fracture of Carbon Steels at ElevatedTem peratures,” by A. E. W hite, C. L. Clark, and R. L. Wilson,Trans. American Society for Metals, vol. 25, September, 1937, pp.863-888; also “Fracture of Steels a t Elevated Tem peratures AfterProlonged Loading,” by R. H. Thielemann and E. R. Parker, MetalsTechnology, April, 1939, Technical Publication No. 1034.
F ig . 9 R e l a x a t i o n C r e e p T e s t o n I te m N o . 8 1 0 ; L o g -L o g P l o t s S h o w in g R e l a t i o n B e t w e e n S t r e s s V e r s u sT im e a n d S t r e s s V e r s u s C r e e p R a t e(T est tem perature 932 F , oil-quenched m aterial. R efer toTables 2, 3, and 4.)C R EEP R A TE - PERCEN T PER 1 0 0 0 0 0 HR.F i g . 12 R e l a x a t io n C r e e p T e s t o n I t e m s N o s. 865a n d 866; L og-L og P l o t s S h o w in g R e l a t io n B e t w e e nS t r e s s V e r s u s T im e a n d S t r e s s V e r s u s C r e e p R ate(Test tem peratures 950 and 1000 F, oil-quenched m aterial.Refer to Tables 2, 3, and 4.)F ig . 10 R e l a x a t io n C r e e p T e s t o n I t e m s N o s. 837a n d 838; L og-L og P l o t s S h o w in g R e l a t io n B e t w e e nS t r e s s V e r s u s T im e a n d S t r e s s V e r s u s C r e e p R a t e(T est tem perature 932 F, air-cooled m aterial. Refer to Tables 2,3, and 4.)C R E E P RATE - PERCEN T P E R 1 0 0 0 0 0 HR.F ig . 13 R e l a x a t io n C r e e p T e s t o n I t e m s N o s. 867a n d 868; L og-L og P lo ts S h o w in g R e l a t io n B e t w e e nS t r e s s V e r s u s T im e an d S t r e s s V e r s u s C r e e p R ate(T est tem peratures 950 and 1000 F, oil-quenched material.Refer to Tables 2, 3, and 4.)F ig . 11 R e l a x a t i o n C r e e p T e s t o n I te m s N o s. 8 6 3a n d 8 6 4 ; L o g -L o g P l o t s S h o w in g R e l a t i o n B e t w e e nS t r e s s V e r s u s T im e a n d S t r e s s V e r s u s C r e e p R a t e(T est tem peratures 950 and 1000 F, air-cooled m aterial. Referto Tables 2, 3, and 4.)C R E E P RA TE-PERC EN T PER 1 0 0 0 0 0 HRF ig . 14 R e l a x a t i o n C r e e p T e s t o n I te m s N o s. 8 6 9a n d 8 7 0 ; L o g -L o g P l o t s S h o w in g R e l a t i o n B e t w e e nS t r e s s V e r s u s T im e a n d S t r e s s V e r s u s C r e e p R a t e(T est tem peratures 950 and 1000 F , w ater-quenched m aterial.Refer toJTables 2, 3, and 4.)658 TRANSACTIONS OF THE A.S.M.E. OCTOBER, 1941
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Transactionsof theHeat Transfer to
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H eat T ran sfer to H ydrogen-N itr
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COLBURN, COGHLAN—HEAT TRANSFER TO
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COLBURN, COGHLAN—HEAT TRANSFER TO
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Electric-Slip Couplings for UseW it
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ANDRIOLA—ELECTRIC-SLIP COUPLINGS
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