1. ASTM A638 yog dab tsi, thiab vim li cas nws tseem ceeb tshwj xeeb rau nag lossis daus - hardening alloys zoo li A-286 thiab 925, piv rau lwm yam bar specifications?
ASTM A638 yog tus qauv qhia tshwj xeeb rau "Ntxhis Hlau Base Superalloy Bars, Forgings, thiab Forging Tshuag rau High- Kev Pabcuam Kub." Nws qhov tshwj xeeb tseem ceeb yog nyob rau hauv nws txoj kev tswj hwm lub hnub nyoog tshwj xeeb- cov hlau tsis muaj zog, qhov sib txawv tseem ceeb ntawm cov qauv zoo li ASTM B637 (rau cov nickel alloy tuav, dav dav) lossis A479 (cov hlau tsis muaj steel).
Rau cov alloys xws li A-286 (hlau-nickel raws) thiab 925 (nickel-hlau raws), uas muab lawv lub zog tshwj xeeb los ntawm kev tswj xyuas thermal aging, A638 muab cov txheej txheem tseem ceeb:
Kev kho cua sov yuav tsum tau: Nws qhia meej meej cov tshuaj annealing thiab kev laus kho cua sov cycles (kub, lub sij hawm, txias tus nqi) yuav tsum tau los txhim kho qhov zoo microstructure. Qhov no suav nrog kev tsim ntawm coherent gamma-prime (') precipitates (Ni₃(Al,Ti) hauv A-286) uas muab lub zog siab.
Property Assurance Post-Kev laus: Cov khoom siv cuab yeej cuab tam (tensile, yield, elongation, hardness) yog txhais rau cov khoom nyob rau hauv lub hnub nyoog. Qhov no tau lees tias lub bar yuav ua tau raws li qhov siab - lub zog tivthaiv, tsis yog cov khoom lag luam xwb.
High-Tsub Pom Zoo: Tus qauv suav nrog cov kev xav tau ntxiv rau kev ntsuas kev nkag siab thiab kev ntxhov siab- cov khoom tawg, uas yog qhov tseem ceeb rau kev siv dav hlau thiab turbine.
Rau cov uas tsis yog- hnub nyoog- hardenable alloys xws li Incoloy 800 thiab 825 kuj muab nyob rau hauv A638, tus qauv feem ntau tswj lawv nyob rau hauv lub annealed los yog tov-annealed mob. Ntawm no, A638 ua haujlwm feem ntau yog cov khoom siv tshuaj lom neeg thiab cov cuab yeej cuab tam tau lees paub, txawm hais tias kev kho cua sov tshwj xeeb rau cov khoom siv no - kev daws teeb meem yog qhov tseem ceeb tsawg dua rau A-286/925. Hauv kev xyaum, 800 thiab 825 bars kuj feem ntau muab rau ASTM B408 / B425, ua A638 qhov kev nyiam tshaj plaws thaum lub bar yog destined rau siab - kub, siab zog forged tivthaiv.
2. Cov yam ntxwv ntawm cov hlau metallurgical tseem ceeb thiab cov kev siv tseem ceeb sib txawv li cas ntawm lub hnub nyoog -hardenable (A-286, 925) thiab solid-solution reinforced (800, 825) alloys them raws li ASTM A638?
Qhov kev faib tawm tseem ceeb nyob hauv lawv cov txheej txheem ntxiv dag zog, uas tswj hwm lawv lub hnab ntawv ua haujlwm thiab xaus - siv.
Hnub nyoog -Hardenable Alloys (A-286, 925):
Strengthening Mechanism: Tau lub zog los ntawm ob-kev kho cua sov: cov tshuaj annealing ua raws li qis dua - kub aging. Qhov no precipitates nanoscale intermetallic hais (gamma-prime) uas kaw dislocations.
A-286 (UNS K66286): Hlau-raws li (~26% Ni) superalloy. Nws cov cwj pwm tseem ceeb yog tensile siab heev thiab tawm los lub zog ntawm qhov kub txog li ~ 1300℃F (700 degree), zoo heev creep kuj, thiab zoo oxidation kuj. Daim ntawv thov yog tsav los ntawm lub zog: fasteners, bolts, turbine engine Cheebtsam, high-temperature li qub, thiab twj tso kua mis shafts nyob rau hauv aerospace thiab lub zog tsim.
925 (UNS N09925): Ib qho nickel-raws li (~42% Ni) alloy nrog ntxiv ntawm Cu thiab Mo. Daim ntaub ntawv: Downhole tool Cheebtsam, valve stems, twj tso kua mis shafts, thiab mechanical Cheebtsam nyob rau hauv aggression roj & roj ntau lawm, tshwj xeeb tshaj yog nyob rau hauv tob, qaub qhov.
Khoom-Txoj kev daws teeb meem Alloys (800/800H, 825):
Strengthening Mechanism: Muab lub zog los ntawm qhov sib txawv ntawm qhov sib txawv ntawm cov austenitic lattice los ntawm cov hlau alloying loj (Mo, Cr, Ni). Lub zog yog tsau los ntawm cov alloy muaj pes tsawg leeg thiab ua hauj lwm hardening.
Incoloy 800/800H (UNS N08800/N08810): Tseem ceeb rau cov ntsiab lus siab carbon hauv 800H rau kev txhim kho creep zog thiab cov qauv ntxhib. Lawv muaj kev tiv thaiv zoo rau oxidation, carburization, thiab sulfidation ntawm qhov kub thiab txias. Daim ntaub ntawv: Kev kho cua sov rau cov khoom siv hluav taws xob, cov raj xa hluav taws xob, cov thermowells, thiab cov khoom hauv petrochemical cracking furnaces.
Incoloy 825 (UNS N08825): Muaj cov molybdenum tseem ceeb (3%) thiab tooj liab (2%). Qhov no muab kev tiv thaiv zoo tshaj los txo cov kua qaub (xws li sulfuric, phosphoric) thiab zoo heev pitting / crevice corrosion kuj nyob rau hauv chloride media. Daim ntaub ntawv: Cov khoom siv tshuaj ua haujlwm, cov tso tsheb hlau luam pickling, kiv cua shafts, seawater system Cheebtsam, thiab nuclear roj reprocessing.
3. Rau siab -kub bolting nyob rau hauv turbines, yog vim li cas yog A-286 ib ASTM A638 feem ntau nyiam dua lwm cov high-strength alloys, thiab nws cov kev txwv tseem ceeb yog dab tsi?
A-286 yog cov khoom tseem ceeb rau siab - kub fasteners (bolts, studs, txiv ntseej) nyob rau hauv cov roj turbine engines thiab high-kev ua tau zoo tso pa system vim muaj ib tug unparalleled ua ke ntawm cov khoom:
Optimized Strength-Tsub Profile: Nws tuav lub zog tawm los siab (~ 100 ksi / 690 MPa ntawm chav tsev kub, khaws lub zog tseem ceeb mus txog 1300℃F / 700℃), uas yog qhov tseem ceeb rau kev tuav clamp load nyob rau hauv thermal cycling.
Zoo heev Creep Relaxation Resistance: Nws cov microstructure tiv thaiv qhov kev poob qis ntawm preload (kev ntxhov siab) nyob rau hauv qhov ntsuas kub ntawm qhov kub, ib hom tsis ua haujlwm rau cov hlau tsis tshua muaj zog.
Fabricability zoo: Nws tuaj yeem nkag tau yooj yim forged, machined, thiab threaded nyob rau hauv cov tshuaj -annealed lub xeev ua ntej zaum kawg aging.
Favorable Oxidation Resistance: Nws 15% Cr cov ntsiab lus tsim ib qho kev tiv thaiv kom txaus rau ntau qhov chaw turbine.
Cov kev txwv tseem ceeb ntawm A-286:
Ceiling Kub: Nws lub zog poob qis dua 1300℃F (700 degree). Rau qhov kub siab dua, nickel-raws li alloys xws li Waspaloy lossis Inconel 718 yuav tsum tau.
Kev ntxhov siab-Kev Cuam Tshuam Cracking (SCC) Kev Tiv Thaiv: Hauv cov hnub nyoog tag nrho, siab - lub zog muaj zog, nws tuaj yeem raug rau cov tshuaj chloride- ntxias SCC. Qhov no txwv nws txoj kev siv nyob rau hauv cov huab cua hauv hiav txwv yam tsis muaj cov txheej txheem tiv thaiv lossis ua tib zoo saib xyuas ib puag ncig.
Notch Sensitivity ntawm High Strength: Nyob rau hauv high-notched configurations thiab nyob rau hauv dynamic loading, yuav tsum tau ceev faj tsim los txo rhiab heev.
4. Nyob rau hauv corrosive oil & gas downhole ib puag ncig, cov khoom tshwj xeeb dab tsi ua rau ASTM A638 925 bar xaiv cov khoom tseem ceeb rau cov khoom xws li valve trim thiab hanger caj npab?
Downhole ib puag ncig nthuav tawm "cua daj zoo nkauj" ntawm corrosives: kev kub ntxhov siab, kub siab, brines nrog chlorides, carbon dioxide (CO₂), thiab hydrogen sulfide (H₂S). ASTM A638 925 bar, muab nyob rau hauv lub hnub nyoog mob, yog engineered kom ciaj sia no triad:
Sulfide Stress Cracking (SSC) Resistance: The aged microstructure, combined with a nickel content >40%, muab kev tiv thaiv zoo heev rau kev ua tsis tiav ntawm H₂S thiab tensile stress, raws li tau lees paub los ntawm NACE MR0175 / ISO 15156 tus qauv.
Chloride Stress Corrosion Cracking (Cl-SCC) Resistance: Cov ntsiab lus siab nickel hauv paus ua rau muaj kev tiv thaiv rau Cl-SCC piv rau stainless hlau.
Lub zog siab-rau- Qhov hnyav piv: Kev laus muab 925 yam tsawg kawg nkaus lub zog ntawm 100 ksi (690 MPa), tso cai rau kev tsim cov khoom muaj zog, thauj khoom-cov kabmob uas tuaj yeem tiv taus qhov sib txawv ntawm qhov sib txawv thiab cov khoom siv tshuab, uas muaj peev xwm nrog cov ntoo khaub lig thinner - ntu.
General thiab Localized Corrosion Resistance: Ntxiv ntawm Molybdenum (3%) tawm tsam pitting thiab crevice corrosion los ntawm chlorides, thaum tooj liab (2%) txhim khu kev tiv thaiv kom tsis txhob muaj acids xws li sulfuric acid, uas tuaj yeem tsim los ntawm kev kho kom zoo.
Cov khoom no ua rau 925 bar Tshuag zoo tagnrho rau kev ua haujlwm rau hauv caj npab hanger, tsaws lub txiv mis, valve stems thiab lub cev, foob vaj tse, thiab lwm yam kev nyab xeeb tseem ceeb - muaj cov khoom hauv cov dej qaub.
5. Dab tsi yog qhov tseem ceeb rau kev siv tshuab thiab kho cua sov ASTM A638 round bars, tshwj xeeb tshaj yog sib txawv cov txheej txheem rau A-286/925 piv rau 800/825?
Cov txheej txheem sib txawv heev vim yog lub xeev metallurgical koom nrog.
Rau Hnub nyoog -Hardenable Alloys (A-286, 925):
Machining: Ua nyob rau hauv cov tshuaj -annealed (soft) mob. Nyob rau theem no, lawv yog cov ductile thiab yooj yim rau txiav. Txawm li cas los xij, lawv yog gummy thiab ua haujlwm - tawv sai. Siv cov cuab yeej ntse, zoo-rake, siab pub tus nqi, thiab qis mus rau nruab nrab ceev nrog cov dej txias txaus.
Kev kho cua sov: Kev nruj ob- cov txheej txheem tom qab machining yog qhov tseem ceeb:
Kev daws Anneal: Kub rau ~ 1800℃F (980 degree) rau A-286, ~ 1750℃F (955 degree) rau 925, ces ceev ceev (feem ntau yog dej). Qhov no dissolves tag nrho cov precipitates.
Kev laus: Thaum tshav kub kub rau qis qis (~ 1300-1400℃F / 700-760 degree) thiab tuav rau 16-24 teev, ces cua txias. Qhov no precipitates lub zog theem. Dimensional stability yog qhov tseem ceeb; cov khoom yuav distort thiab yuav tsum tau tuav nyob rau hauv fixtures los yog zaum kawg hauv av.
Rau Khoom-Kev daws Alloys (800/800H, 825):
Machining: Ua nyob rau hauv qhov kawg annealed mob. Lawv kuj yog tawv thiab ua haujlwm - tawv. 825, nrog rau nws cov ntsiab lus molybdenum siab, tshwj xeeb yog abrasive thiab nyuaj, yuav tsum tau cov qib zoo tshaj plaws.
Kev kho cua sov: Feem ntau tsuas yog siv qhov kawg nkaus anneal (xws li, 1700℃F / 925℃rau 825, 2100℃F / 1150℃rau 800H) ua raws li kev ua kom txias sai kom muaj kev tiv thaiv corrosion thiab, rau 800H, coarse grain qauv. Qhov no yog ua los ntawm lub zeb. Fabricators feem ntau tsuas yog ua kom muaj kev ntxhov siab xwb{11}}reliving tom qab vuam los yog txias txias ua hauj lwm, siv ua tib zoo tswj kub kom tsis txhob rhiab heev (carbide nag lossis daus nyob rau hauv 825) los yog grain loj hlob.
Kev txiav txim siab thoob ntiaj teb: Rau tag nrho cov alloys no, thermal txiav (plasma, laser) yuav tsum tau tshem tawm cov cua sov- cuam tshuam cheeb tsam ntawm machining los kho corrosion thiab mechanical zog.
