Q390E is a high-strength low-alloy steel specifically designed for low-temperature environments, with very strict composition control to ensure good toughness and impact performance under low-temperature conditions. The "E" grade typically indicates higher requirements for low-temperature impact performance.

In addition to containing basic elements such as carbon, manganese, silicon, phosphorus, and sulfur, the chemical composition of Q390E strictly controls the content of these elements to reduce the material's brittleness at low temperatures. For example, the content of sulfur and phosphorus is kept very low to avoid the formation of brittle phases, which could affect the material's toughness.

Furthermore, Q390E may also include special alloying elements such as nickel (Ni), chromium (Cr), and molybdenum (Mo), which can enhance the steel's low-temperature toughness and strength. Nickel expands the austenite phase region, increasing the steel's toughness, while chromium and molybdenum improve the steel's strength and corrosion resistance.

The low-temperature composition control of Q390E ensures that the material maintains excellent mechanical properties even in extreme low-temperature environments, making it suitable for applications such as oil and gas pipelines, polar engineering structures, and other fields that require operation at low temperatures. Low-temperature performance testing for this type of steel typically includes impact tests at -40°C or lower temperatures to verify its reliability in practical applications.