How to improve the low-temperature toughness of 304 precision tubes?

Low-temperature toughness refers to a material’s ability to resist brittle fracture in cold environments. For 304 precision tubes, this property ensures that the pipes can withstand impact, stretching, bending, and other mechanical loads at low temperatures without sudden failure, while maintaining a certain degree of plastic deformation.

Importance of Low-Temperature Toughness in 304 Precision Tubes

In applications like liquefied natural gas (LNG) transportation and low-temperature refrigeration systems, maintaining good low-temperature toughness is crucial for safety and reliability. For instance, in LNG storage and transport, pipelines must operate in extreme conditions around -162°C. If the material lacks adequate toughness, it may become brittle and crack, leading to LNG leaks and severe safety hazards.

How to Improve the Low-Temperature Toughness of 304 Precision Tubes?

1. Chemical Composition Optimization

✔ Increase Nickel Content
Nickel plays a vital role in stabilizing the austenitic phase of stainless steel. Increasing nickel content enhances low-temperature toughness by preventing crack propagation. Raising nickel levels from the standard 8% to around 9%-10% can significantly improve the material’s performance in cold conditions.

✔ Control Impurity Elements
Impurities such as carbon, sulfur, and phosphorus weaken grain boundary bonding, leading to increased brittleness at low temperatures. Advanced smelting techniques, such as vacuum induction melting or electroslag remelting, help minimize these impurities, improving overall toughness.

2. Optimizing Processing Technology

✔ Refining Hot Processing Parameters
During hot rolling or forging, controlling temperature, deformation, and cooling rate is essential. Gradual controlled cooling prevents excessive thermal stress, which can lead to material embrittlement. Proper hot processing helps refine the microstructure, enhancing toughness.

✔ Balancing Cold Processing and Annealing
Excessive cold working (such as cold drawing or cold rolling) increases work hardening, making the material more brittle. Timely annealing restores toughness by eliminating internal stresses. The ideal annealing temperature ranges from 1010°C to 1150°C, with a holding time of 30-60 minutes depending on pipe size and processing history.

3. Surface Treatment Measures

✔ Shot Peening
Shot peening induces compressive stress on the pipe’s surface, counteracting thermal shrinkage-induced tensile stress at low temperatures. This process inhibits crack formation and propagation, significantly enhancing toughness.

✔ Applying Protective Coatings
Coatings such as ceramic or polymer layers provide an additional protective barrier against environmental factors. These coatings also help reduce stress concentration, further improving the pipe’s resistance to low-temperature brittleness.

Conclusion

Improving the low-temperature toughness of 304 precision tubes requires a combination of chemical composition adjustments, optimized processing techniques, and surface treatments. By increasing nickel content, reducing impurities, refining processing methods, and applying surface enhancements, manufacturers can ensure that 304 precision tubes maintain high durability and safety in extreme cold environments—making them suitable for LNG transport, refrigeration systems, and other cryogenic applications.