The core of steel cylinder heat treatment is to optimize its mechanical properties through a controlled process of heating, holding, and cooling, ensuring compliance with safety standards such as pressure resistance and impact resistance. Your focus on steel cylinder heat treatment technology is crucial, as it directly relates to the safe use of pressure vessels. Process parameters vary for different materials (such as 30CrMo, Q345R) and cylinder types (seamless, welded), but the core process remains consistent.
### I. Core Process Types
Steel cylinder heat treatment is mainly divided into two categories, which need to be selected based on the manufacturing stage and performance requirements.
| Process Type | Main Purpose | Application Scenarios |
|--------------------|-----------------------------------------------|--------------------------------------------------------|
| Overall Heat Treatment | Eliminate welding stress, homogenize microstructure, enhance overall toughness | After welding cylinder manufacturing, after seamless cylinder forming |
| Local Heat Treatment | Target stress concentration areas such as welds to eliminate local stress | When large cylinders cannot be heated as a whole, after local repairs |
### II. Typical Process Flow (Taking Welded Cylinders as an Example)
- **Loading**: Place the cylinder steadily into a car-bottom furnace or well-type furnace, ensuring uniform gaps between cylinders to guarantee even heating.
- **Heating**: Increase temperature according to the preset curve, with the heating rate controlled at 50-150℃/h to avoid excessive temperature differences causing cylinder deformation.
- **Holding**: After reaching the target temperature (usually 550-650℃, specific to material), hold for 2-4 hours to ensure complete microstructural transformation.
- **Cooling**: Use furnace cooling or slow cooling, with a cooling rate ≤100℃/h to prevent new internal stresses from forming due to rapid cooling.
- **Inspection After Firing**: After firing, test mechanical properties such as hardness and impact toughness, and check for deformation or cracks in the appearance.
### III. Key Process Parameter Control
- **Temperature**: Must be strictly set according to the phase transformation point of the material. Excessive temperature can lead to coarse grain structure, while insufficient temperature fails to meet performance requirements.
- **Time**: Holding time needs to be adjusted according to cylinder wall thickness. Typically, holding time is extended by 30 minutes for every 10mm increase in wall thickness.
- **Cooling Rate**: A critical factor determining cylinder toughness. For high-strength steels, a slower cooling rate is required to avoid the formation of brittle microstructures.
