As a high-performance pipeline material, duplex steel seamless pipe plays a vital role in modern industry. Its unique dual-phase structure - the coexistence of austenite and ferrite - gives it excellent mechanical properties and corrosion resistance, making it widely used in many fields. 

1. Definition and characteristics of duplex steel seamless pipe
Duplex stainless steel seamless pipe, as the name suggests, is a stainless steel seamless pipe with both austenite and ferrite. This special microstructure gives it a series of unique physical, chemical and mechanical properties. Compared with traditional single-phase stainless steel, duplex stainless steel seamless pipe has higher strength, better corrosion resistance, lower thermal expansion coefficient and better welding performance.

In low temperature environment, the toughness of duplex steel seamless pipe is particularly outstanding. The dual-phase structure enables this material to maintain good toughness and ductility while maintaining high strength, which is particularly important for applications with high stress or dynamic loads. Its high strength and good corrosion resistance ensure long-term stable operation in these harsh environments.

2. Low temperature toughness evaluation method
Low temperature toughness evaluation is an important link to ensure the safe use of duplex steel seamless pipes in low temperature environments. Commonly used evaluation methods include the following:
Charpy V-notch impact test: This test evaluates the toughness of the material by measuring the impact absorption energy of the specimen at low temperature. For duplex steel seamless pipes, this test can reveal its fracture toughness and energy absorption capacity at low temperatures.
Drop weight tear test (DWTT): This test is used to evaluate the tear resistance of materials at low temperatures. By simulating the dynamic tearing process in actual use, the tear toughness of duplex steel seamless pipes in low temperature environments can be judged.
Low temperature tensile test: This test evaluates the toughness of materials by measuring the tensile strength and yield strength of materials at low temperatures. For duplex steel seamless pipes, this test can reveal the balance of strength and toughness at low temperatures.
Low temperature bending test: This test is used to evaluate the bending resistance of materials at low temperatures. By measuring the bending angle and deformation degree of the specimen at low temperatures, the bending toughness of duplex steel seamless pipes in low temperature environments can be judged.

3. Application of low temperature toughness evaluation
The low temperature toughness evaluation of duplex steel seamless pipes is of great significance in many fields. The following are some typical application scenarios:
Petrochemical industry: In the petrochemical industry, duplex steel seamless pipes are often used to transport high pressure, high temperature and corrosive media. Through low temperature toughness evaluation, its safe operation in extreme environments can be ensured.
Marine engineering: In marine engineering, duplex steel seamless pipes are often used to manufacture offshore platforms and submarine pipeline systems. Its excellent corrosion resistance and fatigue resistance enable it to operate stably for a long time in the marine environment. Through low temperature toughness evaluation, its toughness performance in low temperature seawater can be ensured.
Polar scientific research: In polar scientific research, duplex steel seamless pipes are often used to manufacture various equipment and pipeline systems. Through low temperature toughness evaluation, its reliability and safety at extremely low temperatures can be ensured.

With the advancement of science and technology and the development of industry, the low temperature toughness evaluation of duplex steel seamless pipes will show the following trends:
Continuous optimization of evaluation methods: With the development of materials science, low temperature toughness evaluation methods will be continuously optimized and improved. New evaluation methods and standards will continue to emerge to more accurately reflect the toughness performance of duplex steel seamless pipes in low temperature environments.
Continuous improvement of material properties: By optimizing the alloy composition and preparation process, the low temperature toughness of duplex steel seamless pipes can be further improved. This will enable duplex steel seamless pipes to perform better under harsher environmental conditions.
Introduction of intelligent evaluation technology: With the development of intelligent technology, the low temperature toughness evaluation of duplex steel seamless pipes will gradually become intelligent and automated. This will improve the accuracy and efficiency of the evaluation and reduce the cost of the evaluation.

The low temperature toughness evaluation of duplex steel seamless pipes is an important link to ensure their safe use in low temperature environments. By continuously optimizing the evaluation methods, improving material properties and introducing intelligent evaluation technology, we can better evaluate the low temperature toughness of duplex steel seamless pipes and provide valuable references for practitioners in related fields.