Besplatni inženjerski alat
Temperatura zagrijavanja ležaja za montažu
Izračunajte potrebnu temperaturu zagrijavanja za širenje unutarnjeg prstena ležaja za montažu s preklopnim dosjedom. Unesite promjer provrta, preklop i potreban zazor.
Rezultati
Princip toplinskog širenja
Kada se ležaj zagrijava, njegov unutarnji prsten se širi zbog toplinskog širenja čelika. Povećanje promjera otvora proporcionalno je porastu temperature i izvornom promjeru:
- α — koeficijent toplinskog širenja za ležajni čelik ≈ 12,5 × 10⁻⁶ /°C
- d — promjer otvora ležaja (mm)
- ΔT — porast temperature iznad temperature okoline (°C)
Potreban porast temperature
Ukupno potrebno dijametralno širenje je zbroj preklopa osovine i dodatnog zazora za lako klizanje:
Temperaturna ograničenja
| Vrsta ležaja | Maks. temperatura | Razlog |
|---|---|---|
| Standardno (otvoreno) | 120 °C (250 °F) | Izbjegavajte metalurške promjene u čeliku ležaja |
| Zabrtvljeni / zaštićeni (2RS, 2Z) | 80 °C (175 °F) | Spriječite degradaciju masti i oštećenje brtvi |
Praktični primjer
Dano: d = 60 mm, preklop = 30 μm, zazor = 15 μm, Tambijentalni = 20 °C
Ukupno potrebno širenje = 30 + 15 = 45 μm = 0,045 mm
ΔT = 0,045 / (12,5 × 10⁻⁶ × 60) = 0,045 / 0,00075 = 60,0 °C
Tgrijanje = 20 + 60 = 80 °C ✓ (unutar granica za otvorene ležajeve)
💡 Savjet: Uvijek koristite kalibrirano mjerenje temperature. Indukcijski grijači s ugrađenom kontrolom temperature najpouzdanija su metoda za montažu ležajeva.
Heating the bearing expands the inner ring bore, allowing it to slide easily over the shaft for an interference fit. This avoids the need for mechanical force (hammering, pressing), which can damage the bearing raceways and rolling elements.
Thermal mounting is the recommended method for medium and large bearings (bore > 50 mm) and for any bearing with significant interference.
Temperature limits depend on bearing type:
- Standard open bearings: Max 120 °C (250 °F) — higher temperatures risk metallurgical changes in the bearing steel that reduce hardness and fatigue life
- Sealed/shielded bearings (2RS, 2Z): Max 80 °C (175 °F) — grease degrades and seals may deform at higher temperatures
Heating duration depends on the method and bearing size:
- Induction heater: 2–10 minutes (fastest, most controlled)
- Oil bath: 20–40 minutes (limited to ~100 °C with mineral oil)
- Oven/furnace: 30–60 minutes depending on size
The bearing should be heated uniformly. Avoid localized hot spots that could cause distortion.
Common heating methods:
- Induction heaters — fastest, most precise, recommended for production. Demagnetize after heating.
- Electric hot plates — simple, suitable for small bearings
- Oil baths — uniform heating, max ~100 °C with mineral oil
- Ovens/furnaces — good for batch heating, slow but uniform
Never use open flames — they cause uneven heating and localized overheating.
Sealed (2RS) or shielded (2Z) bearings are pre-filled with grease and must not be heated above 80 °C. At higher temperatures:
- Grease properties degrade permanently
- Rubber seals may deform and lose sealing effectiveness
- Grease may leak out of the bearing
If the required heating temperature exceeds 80 °C, consider using an open bearing with a separate sealing arrangement, or reduce the interference fit.
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