Thaum tshav kub kub-Kev cuam tshuam Cheeb Tsam (HAZ) yog thaj tsam ntawm lub hauv paus hlau nyob ib sab ntawm lub vuam uas yog cua sov kom sov hauv qab lub melting point tab sis siab txaus los hloov nws cov microstructure thiab cov khoom. Rau A572 H-beams, siab - zog, nplua-grained microstructure ua tiav los ntawm kev tswj dov tuaj yeem degraded hauv HAZ yog tias vuam tsis raug tswj tau zoo. Kev tswj hwm HAZ yog qhov tseem ceeb rau kev ua kom muaj kev ncaj ncees ntawm kev sib txuas welded.
1. Microstructural Hloov hauv HAZ ntawm A572:
Thaum lub sij hawm vuam, HAZ muaj lub voj voog thermal sai: cua kub hnyav ua raws li qhov txias txias. Qhov siab tshaj plaws kub thiab txias tus nqi sib txawv nrog qhov kev ncua deb ntawm lub vuam fusion kab.
Grain Coarsening Cheeb Tsam (Zoo tshaj plaws rau cov weld): Ua kom kub siab tshaj li 1100℃(2012℃F), qhov twg cov nplej austenite loj tuaj. Thaum txias txias, cov nplej ntxhib no tuaj yeem hloov mus rau hauv cov txheej txheem nkig xws li sab sauv bainite lossis martensite yog tias lub hardenability siab txaus (cuam tshuam los ntawm Carbon Equivalent).
Grain Refined Region (Ntxiv tawm): Rhaub rau hauv thaj av austenite tab sis tsis siab txaus rau kev loj hlob ntau dhau. Thaum txias, qhov chaw no tej zaum yuav muaj qhov loj me me dua li cov hlau hauv paus, muaj peev xwm ua kom muaj zog, tab sis tejzaum nws txo cov tawv.
Tempered los yog Tshaj- thaj tsam laus (Ntawm tawm): Ua kom sov hauv qab qhov kub thiab txias (Ac1). Hauv A572, qhov no tuaj yeem ua rau ntau dua - kev laus ntawm cov precipitates ntxiv dag zog (Cb / V carbides), yaj lawv thiab txo cov nag lossis daus hardening, yog li tsim kom muaj thaj chaw mos.
2. Cov teeb meem muaj peev xwm HAZ hauv A572 H-Beams:
Hardness thiab Cracking: Ib qho ntxhib-grained HAZ nrog martensite tuaj yeem nyuaj heev thiab raug rau hydrogen-induced txias cracking, tshwj xeeb tshaj yog nyob rau hauv strained tuab seem ntawm Gr.60 khoom.
Poob ntawm Toughness: Lub coarse grain cheeb tsam feem ntau muaj qis qis toughness (Charpy cuam tshuam lub zog) dua li lub hauv paus hlau.
Softening (Tshaj -aging): Qhov poob ntawm nag lossis daus hardening tuaj yeem tsim ib txoj hlua nqaim nrog lub zog tawm los ntawm lub hauv paus hlau specification, muaj peev xwm muaj kev txhawj xeeb rau kev thauj khoom hnyav, siab - lub zog sib txuas.
3. Cov Tswv Yim Tswj Xyuas Kom Tiv Thaiv HAZ Properties:
Kev tswj cov khoom siv hluav taws xob: Siv cov khoom siv vuam kom raug (amperage, voltage, ceev ceev) kom ua tiav cov khoom siv hluav taws xob (kJ / mm lossis kJ / hauv). Kev kub siab dhau lawm ua rau qhov loj ntawm qhov ntxhib- thaj tsam grained thiab qhov hnyav dhau - laus. Tsis tshua muaj hluav taws xob input ua rau kom txias txias, txhawb zog, brittle microstructures.
Preheat thiab Interpass Temperature Control: Qhov no yog cov cuab yeej zoo tshaj plaws. Preheat slows tus nqi txias ntawm vuam thiab HAZ. Qhov no muaj ntau yam txiaj ntsig:
Nws tso cai rau hydrogen diffuse tawm ntawm HAZ, txo kev pheej hmoo tawg.
Nws txo cov tawv nqaij tawv, txhawb cov tsim ntawm softer, ntau ductile microstructures (xws li, nplua pearlite / ferrite es tsis txhob martensite).
Nws minimizes thermal stresses.
Qhov yuav tsum tau ua kom sov preheat rau A572 H-beams yog txiav txim los ntawm qhov tseeb Carbon Equivalent (los ntawm MTC), cov ntaub ntawv thickness, thiab cov hydrogen theem ntawm consumable, raws li AWS D1.1 rooj.
Kev siv qis-Hydrogen Welding Consumables: Electrodes thiab xov hlau cais raws li "low-hydrogen" (xws li, E7018, E81T1-K2) txo qis kev taw qhia ntawm hydrogen, thawj tus neeg sawv cev ntawm kev sib tsoo txias.
Tshaj tawm -Kev kho cua sov (PWHT): Tsis yog niaj hnub rau A572, tab sis tej zaum yuav raug teev rau cov kev sib txuas uas tuab heev, txwv tsis pub muaj kev sib txuas (xws li, nyob rau lub sijhawm hnyav lossis cov chaw nuclear). PWHT (kev ntxhov siab ntxhov siab annealing) tempers ib qho nyuaj martensite, relieves residual stresses, thiab tuaj yeem kho qee qhov tawv. Txawm li cas los xij, nws tuaj yeem ua rau ntau dua - hnub nyoog precipitates, ua rau softening.
Welding Sequence and Technique: Kev sib txuas kom raug txo qis kev txwv thiab kev ntxhov siab. Cov txuj ci zoo li temper hlaws vuam tuaj yeem siv los ua kom zoo dua cov qauv ntawm cov khoom siv yav dhau los HAZ.
4. Kev txiav txim siab tsim kom haum rau HAZ:
Joint Detailing: Nrhiav welds deb ntawm qhov chaw siab tshaj plaws (xws li, beam flanges ntawm nruab nrab -span) thaum ua tau.
Kev Sib Txuas Tsim: Siv "kev zam txim" hom kev sib txuas uas tso cai rau qee qhov deformation. Nkag siab tias HAZ, txawm tias me ntsis softened, yog ua hauj lwm - hardened thaum fabrication thiab yog constrained los ntawm ib puag ncig muaj zog puag hlau. Rau A572, lub zog txo qis feem ntau tsis tseem ceeb txaus los cuam tshuam kev tsim lub zog yog tias ua raws li cov txheej txheem tsim nyog.
Table: HAZ Management Practices for A572 H-Beams
| Lub hom phiaj | Thawj Txoj Kev | Ntsiab Parameter/Standard |
|---|---|---|
| Tiv thaiv Hydrogen Cracking | Preheat & Tsawg-Hydrogen Consumables | AWS D1.1 Tables based on CE & thickness. |
| Tswj HAZ Microstructure | Optimize Thaum tshav kub kub input | WPS qhia txog qhov ntsuas kub siab tshaj plaws (piv txwv li, 2.5 kJ / mm). |
| Txhim kho HAZ Toughness | Temper Bead Technique, PWHT (yog tias muaj) | Cov txheej txheem tshwj xeeb tsim nyog. |
| Tsawg Softening | Siv cov hluav taws xob qis qis, tsis txhob PWHT ntau dhau | Khoom siv - cov txheej txheem vuam tshwj xeeb. |
Hauv kev xaus, HAZ ntawm A572 H-beams yog ib qho kev tshwm sim ntawm kev vuam, tab sis nws cov kev cuam tshuam uas cuam tshuam tau zoo - nkag siab thiab tswj tau. Los ntawm kev qhuab qhia ntawm kev siv preheat kom raug, tswj cov cua sov, thiab qis- hydrogen cov txheej txheem, cov neeg tsim khoom xyuas kom meej tias HAZ khaws cov khoom muaj zog thiab tawv, khaws cia tag nrho cov kev ua tau zoo ntawm cov txheej txheem welded.