Q420GJD steel plate is a commonly used construction steel in China, characterized by high strength, good fatigue resistance, high toughness, low brittle transition temperature, excellent cold forming properties, and good weldability. In low-temperature environments, the tensile performance of Q420GJD steel plate remains at a high level.

The chemical composition of Q420GJD steel plate complies with the national standard GB/T 1591-2018 "High Strength Low Alloy Structural Steel." Its carbon content ranges between 0.12% and 0.20%, manganese content between 1.20% and 1.60%, silicon content between 0.35% and 0.65%, phosphorus content not exceeding 0.04%, sulfur content not exceeding 0.04%, chromium content between 0.70% and 1.60%, molybdenum content between 0.25% and 0.80%, copper content not exceeding 0.40%, and titanium content not exceeding 0.04%.

The tensile performance of this steel plate is primarily influenced by the following factors:

1. Alloying elements: Alloying elements in Q420GJD steel plate, such as manganese, silicon, chromium, and molybdenum, significantly enhance the yield strength and tensile strength of the steel. In low-temperature environments, these alloying elements remain highly active, ensuring the steel plate's tensile performance.

2. Microstructure: Through appropriate heat treatment processes, Q420GJD steel plate can achieve fine grains and excellent microstructures, such as tempered sorbite and tempered martensite. These microstructures exhibit good low-temperature toughness, maintaining high tensile performance in low-temperature environments.

3. Low-temperature toughness and weldability: Q420GJD steel plate possesses good low-temperature toughness with high impact absorption energy. Additionally, the steel plate has excellent weldability, allowing the tensile performance of welded joints to be ensured through suitable welding processes.

4. Production processes: Q420GJD steel plate is produced using processes such as hot rolling, normalizing, and tempering. These processes effectively enhance the tensile performance of the steel plate, ensuring good mechanical properties in low-temperature environments.

In summary, Q420GJD steel plate exhibits excellent tensile performance at low temperatures, owing to its advantages in alloying elements, microstructure, low-temperature toughness, weldability, and production processes. In practical applications, appropriate steel plate thickness and specifications should be selected based on specific usage environments and requirements to ensure structural safety and reliability.