Vim li cas Titanium Immersion Rhaub Nrog Polished Weld Toe (Stress Concentration Factor)<1.2) Outlast An As-Welded Joint (SCF >3) Los ntawm Ib Qhov Tseem Ceeb Ntawm 5 Hauv A 90℃Seawater Cathodic Protection System?
Tso lus
Nyob rau hauv 90℃seawater cathodic tiv thaiv system, titanium rhaub yog raug rau ob qho tib si corrosive nres thiab hydrogen embrittlement. Weld ntiv taw yog thaj tsam ntawm kev ntxhov siab ntau. Raws li -welded pob qij txha muaj ib qho kev ntxhov siab concentration (SCF) ntawm 3–5, thaum polished weld ntiv taw txo SCF mus rau<1.2. The higher SCF amplifies tensile stresses, promoting hydrogen-induced cracking and fatigue crack initiation. Reducing SCF by polishing extends service life by a factor of 5.
Quantitative Fatigue Life vs. Stress Concentration Factor
Rau Qib 2 titanium hauv 90℃seawater nrog cathodic tiv thaiv (-0.85 V vs. Ag / AgCl):
| Weld ntiv taw mob | SCF | Cycles to Crack Initiation | Lub neej txheeb ze As -Welded |
|---|---|---|---|
| Raws li -welded, ntse ntswj | 4–5 | 10,000–30,000 | 1× |
| Raws li -welded, nruab nrab | 3–4 | 20,000–50,000 | 1.5× |
| Av du | 1.5–2 | 50,000–150,000 | 3× |
| Polished (mechanical) | 1.2–1.5 | 80,000–200,000 | 4× |
| Electropolished (SCF<1.2) | <1.2 | 150,000–300,000 | 5–7× |
Cov txiaj ntsig ntawm Cathodic Protection Potential ntawm SCF Impact
| CP Potential (V vs. Ag/AgCl) | Raws li -Welded Life (cycles) | Polished Lub Neej (cycles) | Lub neej Ratio |
|---|---|---|---|
| -0.80 | 100,000–200,000 | 500,000–1,000,000 | 5× |
| -0.85 | 30,000–60,000 | 150,000–300,000 | 5× |
| -0.90 | 10,000–20,000 | 50,000–100,000 | 5× |
| -0.95 | 5,000–10,000 | 25,000–50,000 | 5× |
Weld Toe Finishing Guide
| Kev Pabcuam hnyav | Yuav tsum tau Weld Toe Finish | SCF Lub Hom Phiaj | Cia siab tias Kev Txhim Kho Lub Neej |
|---|---|---|---|
| Lub voj voog qis (<10,000 total) | Raws li -welded | <4 | 1× |
| Lub voj voog nruab nrab (10,000-50,000) | Av du | <2 | 3× |
| Lub voj voog siab (50,000-200,000) | Polished | <1.5 | 4× |
| Very high cycle (>200,000) | Electropolished | <1.2 | 5–7× |
Kev pom zoo engineering
Rau titanium heaters nyob rau hauv cathodically tiv thaiv seawater ntawm 90 degree, qhia meej tias tag nrho cov weld ntiv taw yuav hauv av du thiab electropolished kom ua tiav SCF<1.2. By reducing stress concentration, the engineer extends fatigue life by a factor of 5 compared to as-welded joints.
