Why heat bearings for mounting?

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, which can damage the bearing raceways and rolling elements. Thermal mounting is the recommended method for medium and large bearings.

What is the maximum heating temperature for bearings?

Standard bearings should not be heated above 120°C (250°F) to avoid metallurgical changes in the bearing steel. Sealed or shielded bearings with grease fill should not exceed 80°C (175°F) as higher temperatures degrade the lubricant and seals.

How long should a bearing be heated?

With an induction heater, small to medium bearings reach target temperature in 2–10 minutes. In an oil bath or oven, allow 20–60 minutes depending on bearing size. The bearing should be heated uniformly — avoid localized hot spots.

What methods are used to heat bearings?

Common methods include induction heaters (fastest, most controlled), electric hot plates, oil baths (100°C max with mineral oil), and ovens/furnaces. Induction heaters are preferred for production environments as they provide uniform heating with precise temperature control.

What about sealed bearings?

Sealed (2RS) or shielded (2Z) bearings pre-filled with grease should not be heated above 80°C. At higher temperatures, the grease degrades and seals may deform. If the required heating temperature exceeds 80°C, consider using an open bearing with separate sealing arrangement.

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軸承安裝加熱溫度

計算所需的加熱溫度，以膨脹軸承內圈，用於過盈配合安裝。輸入孔徑、過盈量及所需游隙。

熱膨脹過盈配合最高 120 °C

結果

所需加熱溫度

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溫升 ΔT

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所需總膨脹量

—

孔徑膨脹量

—

膨脹係數（鋼）

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⚠️ 密封軸承限制： 溫度超過 80 °C — 不適用於填充潤滑脂的密封/帶護罩（2RS/2Z）軸承。請使用開放式軸承或減少過盈量。

🚫 超過最大值： 溫度超過 120 °C — 有損壞軸承鋼材冶金結構的風險。請重新考慮配合方式或使用液壓安裝方法。

熱膨脹原理

當軸承加熱時，其內圈會因鋼材的熱膨脹而膨脹。孔徑的增加量與溫升及原始直徑成正比：

α — 軸承鋼材的熱膨脹係數 ≈ 12.5 × 10⁻⁶ /°C
d — 軸承孔徑 (mm)
ΔT — 高於環境溫度的溫升 (°C)

所需溫升

所需的總直徑膨脹量為軸過盈量與便於滑動的額外游隙之和：

溫度限制

軸承類型	最高溫度	原因
標準（開放式）	120 °C (250 °F)	避免軸承鋼材發生冶金變化
密封 / 帶護罩（2RS, 2Z）	80 °C (175 °F)	防止潤滑脂降解及密封件損壞

實務範例

範例 — Ø60 mm 孔徑，30 μm 過盈

已知： d = 60 mm，過盈 = 30 μm，游隙 = 15 μm，T_環境 = 20 °C

所需總膨脹量 = 30 + 15 = 45 μm = 0.045 mm

ΔT = 0.045 / (12.5 × 10⁻⁶ × 60) = 0.045 / 0.00075 = 60.0 °C

T_加熱 = 20 + 60 = 80 °C ✓（在開放式軸承的允許範圍內）

💡 提示： 請務必使用經校準的溫度測量。具有內建溫度控制的感應加熱器是軸承安裝最可靠的方法。