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1 -RSEN --TAETOWN ARSENAL,WATT NIASS.'AD -?77--,---SWATERTOWN ARSENAL LABORATORIESW. -EPERATUREXICHAN ICAL ROPERTI ESOF 30P ERIES STAINLESS STE9-ANDTITNIUjL/TECHNICAL REPTO , 0. '1 EILECTEgRANK L. OF ISSUE -DECIUM 1461 ONS CODE 5010.,.84o20051 RESEARCH OF METALS AND NONMETALLIC MATERIALS FOR ORDNANCE CONSTRUCTIOND/A PROJECT 5993-32-002Th5is documet hasbe prvfor public reloase and s=ale; ibgdistribution is unlmited.,. 1 WATERTOWN .72p MASS. IV,,f. 0 .0191it3 ASTIA AVAILABILITY NOTICEI Qualified requesters may obtain copies of this report from available at Office of Technical services $ INTRUCTIONISD estroy; do not return1 NAD Steels, stainless -mechanical propertiesTitaniumLOW TEMPERATURE MECHANICAL PROPERTIESI OF 300 SERIES STAINLESS STEELS AND TITANIUMT echnical Report No. WAL TR S. DeSistoandIdFrank L. CarrDate of Issue -December 1961 OMS Code of Metals and Nonmetallic Materials for Ordnance Constr',ctionD/A Project 5B93-32-002K' -n ForT 4tWATERTOIN ARSENAL oWATERTOWN 72, MASS.

2 ARSENAL LABORATORIESTITLELOW TEMPERATURE MECHANICAL PROPERTIESOF 300 SERIES STAINLESS STEELS AND TITANIUMABSTRACT-A tensile test cryostat is described for the temperature range-240 F to -452 F, which consists of a temperature recording and controlsystem, and a diameter measurement system which includes a scanning con-~trol system. True stress- strain properties of the 300 series stainlesssteels and iodide and conmiercially pure titanium were obtained from roomtemperature to -452 F. Serrated load-elongation curves obtained at-452 IF and the sequence of deformation in multi-necked specimens at thistemperature are S. DeSISTOG eneral EngineerFRANK L. CARILM aterials EngineerAPPROVED:REPORT LLVAND rector Date. 6/tertown Arsenal Laboratories WAL Board of * .. 3 MATERIALS AND PROCEDURE .. 3 Materials, Chemical Analysis and H-eat Treatment ..3 Testing Procedure..#..* .0..*.. *.. 3 TensileTestCrystat ..TEST RESULTS ..7300 Series Stainless Steels.

3 8 Titanium ..* ..9 Serratd Loa-Elongation .** ..13RE FERENCES..32 INTRODUCTIONThe use of liquefied gases in electronic devices and missile propel-lant bystems, and the extremely low temperatures which are encountered inouter space, have created a demand by design engineers for mechanicalproperty data of engineering materials at cryogenic temperatures.'While recently, considerable effort has been devoted to obtainingtensile and other mechanical properties of engineering materials at cryo-genic tempevatures, instantaneous diameter measurements during tensiletesting have not been the importance of the true stress- strain test and theneed for specimen diameter measurements in tests where the material de-forms by a series of discontinuous yields, Watertown Arsenal Laboratoriescontracted with A. D. Little, Inc. to construct a tensile test cryostatcapable of measuring and recording instantaneous diameter purpose of this report is threefold:a.

4 To describe briefly the tensile test To present engineering and true stress- strain data obtained withthis equipment on the 300 series stainless steels and commercially pureand iodide To comment on observations noted on the formation and developmentof necks at -452 AND PROCEDUREM aterials, Chemical Analysis and Heat TreatmentThe materials used in this investigation together with the specimennomenclature and chemical analysis are shown in Table I. The stainlesssteel and commercially pure titanium were utilized in the as-receivedmill-annealed condition. The iodide titanium was annealed five hours at1600 F in a ProcedureRound diameter tensile specimens, as shown in Figure 1,were used in this testing program. Tests were condr'cted in a Baldwin60,000-pound hydraulic testing machine at a controlled platen speed of* inch per minute. Low temperature tests at -105 F, -240 F and -320 Fwere conducted in a double-walled metal container.

5 The coolants usedwere alcohol, with dry ice added, for -105 F; isopentane in the inner con-tainer with liquid nitrogen added to the outer container, when needed,for -240 F; and liquid nitrogen at its boiling point, -320 F. Over .b3D -C%MO IA\HP, 'O E00-000 Sclir-'I 'I .NOc r- flr t- L, \O-Ho ~rt-r-I -i00 O'l O\'C!H H 0000 HHH4 H --'- C'J 0\ OJi Cm Hr 0 0000 ;C0) d 00000 0 0 Ici 4I rOC 4O' C4 C'-E4H 00000 0 0U) -4H 0-4-temperature range, an instantaneous diameter gage2 was used to obtaindiameter data for true stress- strain calculations. For tests at -452 F,liquid helium was used in the tensile Test CryostatThe tensile test cryostat consists of a low-temperature tensile testchamber, a temaperature recording and control system, and a tensile diametermeasurement system which includes a scanning control system. The unit wasdesigned to be compatible with an existing true stress- strain schematic diagram of the test apparatus is shown in Figure 2.

6 The low-temperature test chamber, designed for the temperature range of -240 F to-452 F, consists of an inner vessel which contains the cooling medium andwhich comprises the actual test volume to be maintained at the desiredtest temperature. The inner chamber is surrounded in turn by a vacuumjacket, a liquid nitrogen bath and outside vacuum The test chamber is supported by the lower head of the testing ma-chine; the upper head moves relative to the lower top and bottom specimen holders are sealed in the cryostatagainst leakage by removable "0" rings at the ambient ends. The topholder, together with the four diameter-measuring caliper fingers, passthrough the cover plate into the test volume through the top of the testchamber, and are part of the measuring-head assembly. The specimenholders were designed to withstand 20,000 pound approximate coolant consumption rates for a test at -452 F are asfollows:Nitrogen consumption:precooling loss litersheat-leak loss liters per hourHelium consumption:precooling loss litersheat-leak loss liters per hourThe temperature in the test chamber is measured by four copper-constantan thermocouples, one at each end of the four caliper thermocouples are connected in series to increase the output temperature-controller consists of a Leeds and Northrup potentiometerand duration-adjusting type ( ) controller.

7 The cooling liquid istransferred from a storage Dewar flask to the test volume through a vacuumjacketed helium transfer tube when the solenoid valve connected to thehelium exhaust tube of the test chamber is opened on a signal from a relaycontrolled by the diameter-measurement system consists of four caliper fingersspaced at 90 degrees around the diameter specimen in a planeperpendicular to the specimen axis. The fingers are coupled each to alinear variable differential transformer through a pivoted right anglearm, and are each held against the test specimen by the unbalanced mass ofthe right angle output signal, which is proportional to the average diameter ofthe speciy,.en, is fed into the true stress- strain computer and can be readvisually on a graduated dial or, when used in conjunction with load datafrom the testing machine, can provide an autographic curve of true stress- strain on a Baldwin MD-2 recorder. If desired, diameter profile datacan be obtained on an auxiliary recording scanning motor mounted on the cover of the test chamber drives thecarriage carrying the four caliper fingers over the gage length of thespecimen seeking a minimum diameter.

8 An arm, which is friction coupledto the graduated diameter dial of the computer, serves as a memory minimum diameter is obtained, the fingers scan until a diameter greater than minimum diameter is obtained, thqn the direction of scanis reversed on a signal from a microswitch, and the motor drives thefingers back through minimum diameter to a diameter inch greater,and then the scan is again reversed. Provision is mde for a full gagelength scan to study the development of multiple necks. Limit switchesare provided to prevent travel of the fingers beyond the shoulders of of loads and platen displacement were made on a Baldwin MD-2recorder, with loads obtained from the testing machine Bourdon tube micro-former and displacement measured by a deflectometer. The deflectometer,placed under the moving platen, was capable of strain read-outs of per inch of chart displacement. The full range of the unit the specimen was mounted into the test chamber and cooled tothe desired test temperature, the diameter-indicating dial was adjustedto read the calculated diameter at the test temperature.

9 This wasnecessary as contraction of the four caliper fingers could indicate afalse diameter reduction. For tensile tests, where load displacement re-cords were obtained, the specimen gage length was scanned before and aftereach serration and the minimum diameters of the several necks were notedand recorded on the stress data were obtained by dividing the area of the specimenat the time of the serration into the peak load. These data thereforereflect the upper envelope of the flow stress RESULTSThe data obtained in this investigation are plotted in Figures 3through 19 and tabulated in Table IITENSILE PROPERTIESU ltimate TrueTesting Tensile Elon- Reduction Stress at Fracture TrueTemp Strength gation of Area Max. Load Stress strain at Fracture(deg F) (psi) (%) (%) (psi) _(psi) Max. Load StrainAISI 302 Stainless 94,400 149,600 319,550 152,400 218,700 368,850 191,300 262,900 422,300 219,300 292,150 481,150 249,500 548,500 550,900 303 Stainless 100,200 157,800 255,000 161,500 219,900 299,000 206,300 266,000 355,200 234,100 293,500 398,500 266,500 423,600 423,600 304 Stainless 95,100 154,100 330,100 151,100 211,800 387,900 193,800 264,200 447,000 221,400 301,800 488,000 242,500 363,400 478,100 316 Stainless 93,900 133,900 269,700 " 131,500 198,800 369,000 161,10O 256,000 435,000 184,300 270,500 497,400 216,400 360,200 530,250 347 Stainless 99,300 143,200 266,000 136,600 194,700 326,000 172,100 238,600 374,400 201,400 274,500 423,800 236,400 438,000 500,300 0,789A-55 68,700 77,200 111,300 87.

10 500 109,100 181,200 107,200 157,700 254,600 139,000 200,900 313,400 176,500 37,0 298,700 353,500 46,000 67,000 144,100 72,000 102,100 198,700 92,400 , 138,700 289,000 112,000 185,500 290,000 143,200 247,100 320,400 Series Stainless SteelsThe tensile strengths of the 300 series stainless steels, plotted inFigure 3, generally increase with decreasing temperature. This increaseis fairly linear to -320 F, but at -452 F the strengths of types 302, 303and 304 are lower than would be expected by extrapolating from the highertemperatures. This might be taken to indicate a slight degree of em-brittlement at -452 ductility of the stainless steels tested generally decrease withdecreasing temperature. An exception is Type 316 which increases fromroom temperature to -105 F, remains constant to -320 F and drops at-452 F. The least ductile of these materials is Type 303, which has thehighest tensile plots of true stress- strain for the temperature oange investi-gateCd re plotted in Figures 4 through 8.