How much do you know about heating methods for shrink-fit bearings?
Published on:
2025-09-04 14:08
How much do you know about heating methods for shrink-fit bearings?
Shrink-fit bearings (also known as "temperature differential assembly") are an efficient assembly method that heats the bearing to expand it, achieving an interference fit with the shaft sleeve or bearing seat. Reasonable selection of heating method and control of heating temperature are the key to ensuring assembly quality and avoiding bearing damage. Heating methods are usually divided into four categories based on heating efficiency, temperature uniformity and equipment conditions. The following is a detailed introduction to their methods and applicable occasions.
1. Oil bath heating method (traditional classic method)
Working principle: Immerse the bearing in heat-conducting oil, heat the oil through electric heating tubes or flames, and indirectly heat the bearing.
Key Operational Tips:
1) Use dedicated bearing heating oil (such as 32# or 46# machine oil, flash point ≥ 180°C). Avoid using flammable liquids such as gasoline and kerosene.
2) The bearing must be completely immersed in the oil, with the bottom elevated above the bottom of the container (a metal mesh or bracket can be used) to prevent localized overheating.
3) A temperature sensor must be installed to monitor the oil temperature in real time to prevent boiling or localized carbonization.
Advantages: Excellent temperature uniformity (±5°C), suitable for small and medium-sized bearings (inner diameter ≤ 100mm), low cost.
Limitations: Low heating efficiency (slow temperature rise), oil easily contaminates bearings, requiring regular oil changes.
2. Electric induction heating (mainstream method in industry)
Working principle: Using the principle of electromagnetic induction, the bearing is placed in the induction coil, and the alternating magnetic field causes eddy current heating inside the bearing metal, achieving rapid temperature rise.
Categories and Applications:
1) Portable Induction Heaters: Small, handheld devices suitable for bearings with an inner diameter of 50-300mm. They offer a short heating time (5-15 minutes) and are flexible to operate, making them widely used in field repairs.
2) Fixed Induction Heating Equipment: High-power coils capable of heating large bearings with an inner diameter of 200mm or greater. Equipped with automatic temperature control and heat preservation features, they are suitable for mass assembly lines.
Advantages: Fast heating (3-5 times faster than oil bath), no oil contamination, high temperature controllability (±3°C), and excellent safety.
Limitations: Sensitive to bearing material and structure (for example, bearings with seals must avoid localized overheating), and high equipment cost.
3. Oven heating method (batch uniform heating)
Working principle: Place the bearing in a constant temperature oven and heat it through hot air circulation or electric heating wire radiation to achieve overall uniform temperature rise.
Key points:
1) Bearings should be placed flat or suspended, avoiding stacking, to ensure even heating.
2) The heating rate should be controlled within 5-10°C/minute to prevent deformation caused by large temperature differences.
Advantages: Suitable for batch heating of small and medium-sized bearings, with excellent temperature stability (±2°C) and no risk of local overheating.
Limitations: Long heating time (typically 30-60 minutes), low energy efficiency, and unsuitable for emergency assembly.
4. Other Special Heating Methods
Infrared heating: This method uses infrared lamps to heat the bearing in a targeted manner. It is suitable for localized heating or small bearings, but it is important to avoid concentrated light spots that could cause localized overheating.
Steam heating: Utilizes the heat of saturated steam for heating. It is suitable for high-temperature demand scenarios (e.g., heating temperature > 150°C). However, the equipment is complex and is rarely used.
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