Q550D is a kind of low alloy high-strength structural steel, and its grade means: "Q" stands for yield strength, "550" stands for the lower limit value of yield strength of 550MPa, "D D" represents the quality grade, indicating that it has -20℃ impact toughness. This product strictly follows the standard GB/T 1591-2018 "Low Alloy High Strength Structural Steel", and through micro-alloying design and controlled rolling and cooling process, it achieves a perfect combination of high strength, high toughness and good weldability, and is a key material for realizing the lightweighting of engineering structures and enhancing safety and economic benefits.

Q690D is an ultra-high-strength grade structural steel in GB/T 1591-2018, with a yield strength of not less than 690MPa. "D" and "E" grades are required to have excellent low-temperature impact toughness of -20℃ and -40℃, respectively. Adopting advanced metallurgical technology and strictly controlled thermo-mechanical rolling process, this product ensures sufficient toughness and weldability while pursuing ultimate strength, making it the ultimate choice for manufacturing ultra-heavy-duty, lightweight, and high-safety core structural components.

Q690E is an ultra-high-strength grade structural steel in GB/T 1591-2018, with a yield strength of not less than 690MPa. "D" and "E" grades are required to have excellent low-temperature impact toughness of -20℃ and -40℃, respectively. Adopting advanced metallurgical technology and strictly controlled thermo-mechanical rolling process, this product ensures sufficient toughness and weldability while pursuing ultimate strength, making it the ultimate choice for manufacturing ultra-heavy-duty, lightweight, and high-safety core structural components.