Qhov Kev Ua Haujlwm Txias Li Cas (5% vs . 20% Txo) ntawm Titanium Heater Tube Ua ntej Annealing Hloov Cov Recrystallized Grain Loj thiab Kev Ua Haujlwm Tom Qab Thermal Fatigue Cracking hauv Cua ntawm 300 degree?
Tso lus
Qhov hla ntawm titanium rhaub raj yog txo los ntawm qee feem pua ntawm cov duab txias ua ntej qhov kawg annealing hauv kev tsim cov titanium rhaub raj. Tus tsav tsheb rau recrystallization thaum lub sij hawm annealing yog qhov ua haujlwm txias. Loj recrystallized nplej ntawm ASTM 4-5 (inch 80-120 μm) yog tsim los ntawm kev ua haujlwm txias qis ntawm 5%. Nyob rau theem siab ntawm kev ua haujlwm txias ntawm 20% zoo recrystallized nplej ntawm ASTM 8-10 (inch 11-22 µm) tau txais. Cov khoom nplua-grained nyob rau hauv huab cua ntawm 300℃qhia 3-5 lub sij hawm muaj zog tiv thaiv thermal qaug zog tawg vim yog thaj tsam loj ntawm cov qoob loo muaj rau cov kev pab cuam ntawm cyclic thermal strain thiab tsis kam tawg propagation nyob rau hauv cov nplej me.
Thermal Fatigue Resistance thiab Grain Size Effect Mechanism
Lub titanium raj swells thiab cog lus thoob plaws hauv lub thermal cycling ntawm 300 degree. Slip thiab grain ciam zawv zawg kom haum rau kev sib tw cyclic. Fine- cov khoom muaj txiaj ntsig muaj ntau thaj tsam ntawm ib chav tsev ntim yog li qhov sib txawv ntau dua. Kev pib tawg yuav tshwm sim ntawm cov hlua khi thiab cov ciaj ciam ntawm cov qoob loo, cov nplej me me yuav txo qis qhov ntev thiab qhov kev ntxhov siab ntawm cov ciam teb. Tus nqi ntawm kev qaug zog pob txha propagation raws li da / dN ∝ d^0.5, qhov twg d yog cov grain loj. Ib nrab ntawm txoj kab uas hla tau muab 30% txo qis hauv kev tawg paj tawg. Tsis tas li ntawd, cov nplej nplua nuj yog cov teeb meem loj dua rau kev loj hlob tawg vim tias cov kab nrib pleb yuav tsum tau hloov cov kev taw qhia thiab dissipate lub zog.
Quantitative Cold Work piv rau Recrystallized Grain Size
Cov nram qab no recrystallized grain ntau thiab tsawg tau txiav txim los ntawm kev tswj annealing ntawm Qib 2 titanium raj ntawm 700℃rau 30 feeb tom qab ntau degrees ntawm txias ua hauj lwm. Recrystallized grain loj ntawm 5% kev ua haujlwm txias yog ASTM 3-5 (inch 50-125 µm) thiab hardness tom qab annealing yog 160-180 HV. Cov nplej loj yog ASTM 5-7 (32-64 microns) thiab hardness yog 170-190 HV ntawm 10% ua haujlwm txias. Cov nplej loj yog ASTM 7-8 (22-45 m) tom qab 15% kev ua haujlwm txias thiab qhov nyuaj yog 180-200 HV. Ntawm 20% kev ua haujlwm txias, cov nplej loj yog ASTM 8 - 9 (16 - 32 μm) thiab hardness yog 190 - 210 HV. Lub grain loj ntawm 30% txias ua hauj lwm yog ASTM 9-10 (11-22 µm) thiab hardness yog 200-220 HV. Cov qoob loo loj yog ASTM 10-11 (8-16 µm) thiab hardness yog 210-230 HV ntawm 40% ua haujlwm txias.
300℃Thermal Fatigue Life Dependence on Grain Size
Thermal fatigue crack depths rau Qib 2 titanium tau txiav txim siab los ntawm kev sim cyclic hauv huab cua ntawm 300℃nrog qhov kub ntawm qhov kub ntawm 250℃(50℃txog 300 degree) rau 10,000 cycles. Qhov tawg qhov tob tom qab 10,000 cycles yog 150-300 μm rau ASTM grain loj 3-5 (5% ua haujlwm txias) thiab lub neej qaug zog rau 1 hli tawg yog 30,000-50,000 cycles. ASTM grain loj 5-7 (10% ua haujlwm txias) muab qhov tob ntawm 80-150 µm thiab lub neej mus rau 1 hli ntawm 60,000-100,000 cycles. ASTM grain loj 7-8 (15% kev ua haujlwm txias) Qhov tob tob: 40-80 um Lub neej rau 1 hli: 120,000-200,000 cycles. Rau ASTM grain loj 8-9 (20% ua haujlwm txias) tawg qhov tob yog 20-40 micron Lub neej rau 1 hli yog 250,000-400,000 cycles. Crack qhov tob yog 10-20 µm rau ASTM grain loj 9-10 (30% ua haujlwm txias). Lub neej rau 1 hli yog ntau tshaj 500,000 cycles.
Daim Ntawv Qhia Txog Kev Ua Haujlwm Txias thiab Cov Txiaj Ntsig Loj Xaiv rau Kev Pabcuam Cua ntawm 300 degree
Cov lus hauv qab no muab cov lus pom zoo ntawm kev ua haujlwm txias ua ntej thiab cov txiaj ntsig loj rau titanium rhaub cov raj rau kev pabcuam hauv huab cua ntawm 300 degree, nyob ntawm seb muaj pes tsawg tus thermal cycles thiab lub neej ua haujlwm qaug zog.
Lub neej xav tau qaug zog ( voj voog mus rau 1 hli tawg) Cia siab rau Thermal Cycles Over Service LifeRecommended Ua ntej Cold Work (%) Resulting Grain Size (ASTM) Cia siab tias Crack Depth tom qab 10,000 cycles (µm)<30,000 >30,000 5 3-5 150-300 30,000-60,000 >60,000 10 5-7 80-150 60,000-120,000 >120,000 15 7-8 40-80 120,000-250,000 >250,000 20 8-9 20-40 >250,000 >500,000 30 9-10 10-20 Engineering Beyond Cold Work Control
The recrystallization behavior is dependent on the titanium grade. Grade 7 recrystallizes at a slightly higher temperature than Grade 2 due to the presence of palladium, but the final grain size for a given amount of cold work is similar. Grade 5 (Ti-6Al-4V) does not completely recrystallize under these conditions. Wall thickness does not directly affect grain size, but does affect crack propagation time. A 2.0 mm wall with a 20 µm crack has 98% of its wall remaining. The grain size is also affected by the annealing temperature and duration . A higher temperature or longer time coarsens the grains . Cold work > 20% is excellent for optimal thermal fatigue resistance. Too much cold labor (>40%) tuaj yeem ua rau tawg thaum kos duab.
Kev Sau Cov Lus Qhia Tshwj Xeeb
Qhia meej txog kev ua haujlwm txias ua ntej ntawm 20-30% ua ntej qhov kawg annealing rau titanium rhaub tube ua haujlwm hauv huab cua ntawm 300℃nrog kev sib tw thermal. ASTM 8 lossis finer qhov kawg recrystallized grain loj yuav tsum tau. Kev ua haujlwm txias ntawm 10 mus rau 15% yog qhov siv tau rau cov ntawv thov kwv yees kom muaj tsawg dua 60,000 cycles. Rau kev caij tsheb kauj vab hnyav (ib hnub pib{11}} nres rau 10 xyoo, ~ 3,650 cycles), qhov sib txawv ntawm ASTM 5 thiab ASTM 8 yog qhov tsis txaus ntseeg thiab kev ua haujlwm txias txias txaus. • Rau cov ntawv thov tseem ceeb uas yuav muaj kev kub ceev ceev (ntau lub voj voog ib hnub), qhia 30% kev ua haujlwm txias thiab ASTM grain loj 9 lossis finer. Tus kws ua haujlwm tswj xyuas cov haujlwm txias ua ntej annealing thiaj li tswj cov qoob loo kom tau txais qhov tsim nyog thermal qaug zog ntawm 300 degree.
