Yuav ua li cas cov Volume Fraction ntawm Primary Ferrite nyob rau hauv 316L Heater Sheath Tubing Tom qab siab -Tub (1,150 degree) tshuaj Annealing tswj lub Solidification Cracking Susceptibility Thaum kawg Cap Vuam

Ferrite Qhov rai rau Weldability ntawm Austenitic Stainless Steels

Lub ntim feem ntawm khaws cia thawj delta ferrite tom qab kev daws annealing ntawm 1,150℃(siab dua li 1,040-1,080℃feem ntau teev) ncaj qha tswj hwm qhov cuam tshuam rau solidification cracking thaum lub sij hawm autogenous gas tungsten arc vuam (GTLAW) ntawm 3athing stainless steel cap 16 vuam. Ferrite cov ntsiab lus nyob rau hauv 316L yog kwv yees li 3-8% (nyob ntawm chemistry) ntawm cov tshuaj annealing kub (1,040-1,080℃). Txawm li cas los xij, cov tshuaj annealing ntawm 1150℃(feem ntau ua haujlwm rau tag nrho cov carbides los yog coarsen nplej rau creep resistance) txav theem sib npaug ntawm austenite ntawm qhov kub siab dua, muab ferrite ntim feem ntawm 0-3% ntawm qhov txias. Nws tau pom tias thaum lub sij hawm welding, weld hlau nrog ferrite concentration tsawg dua 2-3% solidifies nyob rau hauv ib tug tag nrho austenitic hom, uas yog tshwj xeeb tshaj yog rhiab heev rau kub tawg vim segregation ntawm low-melting-point impurities (P, S, Si) rau grain ciam teb. Qhov tseem ceeb ferrite qhov pib rau kev sib tsoo tsis muaj vuam yog 3-8% ferrite hauv cov hlau vuam (4-10% ferrite hauv cov hlau hauv lub hauv paus hlau rau autogenous welds). Nyob rau hauv daim ntawv no qhov kev sib txuas ntawm kev daws annealing kub, ferrite ntim feem thiab weld kub cracking susceptibility yog quantified.

Mechanism ntawm Ferrite Tswj Solidification Cracking

316L Thawj theem tsim los ntawm cov kua ntawm solidification ntawm 316L weld hlau yuav yog delta ferrite yog hais tias muaj pes tsawg leeg nyob rau hauv lub ferrite -austenite ntau yam ntawm Schaeffler daim duab. Lub solubility ntawm impurities (P, S, Si) nyob rau hauv lub ferrite theem yog siab tshaj nyob rau hauv lub austenite. Thaum lub sij hawm solidification no impurities muab faib rau lub ferrite thiab inhibit zus tau tej cov tsawg-melting- taw tes kua films ntawm lub austenite grain ciam teb. Tus nqi ntawm ferrite tshuav nyob rau hauv chav tsev kub (feem ntau yog 3-8%) qhia tau hais tias solidification tshwm sim nyob rau hauv lub ferrite- austenite hom (FA hom), uas yog tawg -resistant. Yog tias ferrite concentration tsawg dua 2-3%, solidification tshwm sim hauv austenite hom (A hom). Nyob rau hauv hom no, austenite dendrites yog tsim ncaj qha los ntawm cov kua thiab impurities yog concentrated nyob rau hauv lub xeem-rau-solidify interdendritic cheeb tsam tsim kua films uas shatter nyob rau hauv cov kev nyuaj siab ntawm thermal contraction.

Kev sib raug zoo ntawm kev daws qhov kub thiab txias, Ferrite thiab Weld Cracking

Cov ntsiab lus ferrite hauv qab no thiab qhov tshwm sim tawg tau tshwm sim los ntawm kev tswj cov tshuaj annealing ntawm 316L tubing (0.02% C, 11.5% Ni, 2.2% Mo, sib npaug li qub) ntawm ntau qhov kub thiab txias tom qab los ntawm autogenous GTAW (tsis muaj qhov muab tub lim, cov khoom siv hluav taws xob 0.5 kJ / mm) thiab transverse bend testing.

Tshuaj Annealing Temperature (degree) Base Metal Ferrite Volume Fraction (%) (ferritescope) Weld Metal Ferrite Volume Fraction (%) (autogenous) Solidification Mode Kub Cracking Incidence (% visual at 10x) Welded End Cap Service 1,400<0.1 <0.1 A (austenitic) >80% Tsis muaj 1,150 0-1 0-1 A (austenitic) 50-80% Tsis yog 1,120 1-2 0.5-1.5 A (austenitic) 30-60% Tsis muaj 1,100 2-3 1-2 AF (austenite-ferrite) 15-30% Marginal 1},{{1} FA 5-15% Txais 1,060 4-6 3-5 FA 2-8% Yog 1,040 5-8 4-6 FA 1-5% Yog (zoo tshaj) 1,020 6-10 5-8 FA<2%Yes (but sigma risk) 980 8-12 7-10 FA <2% Yes (but carbide risk)
Lub luag haujlwm ntawm Niobium thiab lwm yam Austenite Stabilizers

Kev suav nrog austenite-stabilizing cov ntsiab lus (Ni, N, C, Cu) hloov pauv cov ntsiab lus ferrite nqes mus rau qhov kub thiab txias.

Alloy Ni (wt%) N (wt%) Ferrite @ 1,040 °C (%) Ferrite @ 1,100 °C (%)Recommended Max Annealing Temp for >3% Weld Ferrite 316L (qis Ni) 10.0-10.5 0.04-0.06 6-10 3-5 1, 100℃316L (tus qauv) 10.5-11.0 0.06-0.08 5-8 2-4 1,080℃316L (siab Ni) 11.0-11.5 0.08-0.10 4-6 1-3 1,060℃316L (siab Ni) 11.5-12.0 0.10-0.12 3-5 0-2 1,040℃347 (Nb.0/A14) 5-8 2-5 1, 080℃Tswv yim pom zoo rau Welded rhaub Manufacturing

316L rhaub sheaths xav tau kawg lub hau vuam yuav tsum ua raws li cov hauv qab no cov tshuaj annealing thiab ferrite cov cai.

Xav Weld Integrity Level Yam tsawg kawg nkaus Weld Hlau Ferrite rau Crack-Welding Dawb (%) Tshuaj Annealing Temperature Range (degree) Base Hlau Ferrite Target (%) Cov txheej txheem pov thawj
Tsawg (kev pabcuam qhuav, tsis tseem ceeb)2 1,060-1,080 3-5 Ferritescope<5 %
Txheem (dej immersion) 3 1,040-1, 060 4-6 Ferritescope 4-8%
High (pressurised, corrosive) 4 1,020-1,040 5-8 Ferritescope >5% + WPS kev tsim nyog
Tseem ceeb (nuclear, siab siab) 5 1,000-1,020 6-10 Cov txheej txheem vuam puv
Ferrite thiab Weldability Verification

Buyers that need weldable 316L sheath tubing can verify this in two ways. The first is ferritescope measurement on the base metal in the as-received condition. GTAW standard: >4% ferrite in base metal (weld metal ferrite >3%). Qhov thib ob yog ib qho kev xeem weldability: tsim ib qho autogenous GTAW weld ntawm ib lub raj coj mus kuaj, hla -section, polish, etch thiab soj ntsuam rau micro- tawg. Txais yuav tsum Tsis muaj pob txha ntawm 200 × magnification

Xaus: Specification of Solution Annealing Temperature for Weldable 316L

Rau 316L stainless hlau rhaub sheaths uas yuav tsum tau tawg -dawb kawg hau welds, cov tshuaj annealing kub yuav tsum tau tswj kom muaj ib tug puag hlau ferrite ntim feem ntawm 4-8%, ua weld hlau ferrite ntawm 3-6% thiab xyuas kom meej FA (ferrite-austenite) solidification hom Qhov no ntau yam ntawm ferrite yog tsim los ntawm kev daws annealing ntawm ib txwm 1,040-1,080 degree. Annealing ntawm 1,100℃thiab saum toj no ua rau<2-3% ferrite, resulting in full austenitic solidification. Hot cracking rates are 30-60%. The fabrication of the welded heater is carried out with 316L sheaths having annealed tubing and an allowable solution annealing temperature of 1080°C with a minimum base metal ferrite of 4% (by ferritescope). For alloys with higher nickel contents (Ni > 11.5%), a lower annealing temperature (≤1,040°C) may be necessary to retain sufficient ferrite. The framework given here allows the purchasers to set the tube annealing parameters to assure reliable end cap welding by correlating solution annealing temperature with ferrite volume fraction and weld hot cracking susceptibility .