What is Q345 Steel? A Complete Guide

Q345 is a material in the Chinese GB standard, characterized as a low-alloy steel (C<0.2%). The “Q” in Q345 represents the material’s yield limit, while the number “345” indicates its yield strength of around 345MPa. The yield value tends to decrease with increasing material thickness. Q345 steel finds widespread application in bridges, vehicles, ships, buildings, pressure vessels, and more.

Q345 Steel

 

Characteristics of Q345 Steel

Characteristics of Q345 Steel

 

High Strength

The tensile strength of Q345 steel ranges from 490 to 660MPa, classifying it as a high-strength steel grade.

Strong Corrosion Resistance

Q345 steel is alloyed with certain elements, endowing it with excellent corrosion resistance.

Thickness Affects Yield Value

The yield value of Q345 steel tends to decrease with increasing material thickness.

Low-Temperature Performance

Q345 steel exhibits excellent low-temperature toughness, making it suitable for engineering applications in low-temperature environments. It can be used even in environments as cold as -40 degrees Celsius without significantly impacting its performance.

Excellent Welding Performance

Q345 steel demonstrates excellent welding characteristics, as it is less prone to defects such as cracks and porosity during the welding process. The strength of the weld joint after welding typically approaches that of the base material, ensuring a strong and reliable connection at the welded joints.

Strong Plasticity

Strong Plasticity

Despite its high strength, Q345 steel retains excellent plasticity, making it easy to process into various shapes such as plates, profiles, and pipes.

 

Equivalent Materials to Q345 Steel

ASTM A572 Steel

ASTM A572 is a high-strength low-alloy structural steel specified in the American standard. It shares similarities with Q345 steel in terms of chemical composition and mechanical properties.

JIS G3101 SS490 Steel

SS490 is a structural steel specified in the Japanese Industrial Standard JIS G3101. It possesses strength and weather resistance properties similar to Q345 steel.

EN 10025 S355 Steel

S355 is a high-strength low-alloy structural steel specified in the European standard EN 10025. It shares similarities with Q345 steel in terms of chemical composition and mechanical properties.

 

Q345 Steel Grades

Q345 Steel Grades

Similar to the naming convention of Q235, Q345 steel is classified into grades: Q345A, Q345B, Q345C, Q345D, and Q345E. These grades primarily differ in the impact temperatures they are designed for. The impact values vary accordingly at different impact temperatures.

Q345A Grade

Q345A grade typically contains:

  • Carbon (C) ≤ 0.20%
  • Manganese (Mn) 1.0~1.6%
  • Silicon (Si) ≤ 0.55%
  • Phosphorus (P) ≤ 0.045%
  • Sulfur (S) ≤ 0.045%
  • Vanadium (V) 0.02~0.15%
  • Q345A grade is not subjected to impact testing.

Q345B Grade

Q345B grade typically contains:

  • Carbon (C) ≤ 0.20%
  • Manganese (Mn) 1.0~1.6%
  • Silicon (Si) ≤ 0.55%
  • Phosphorus (P) ≤ 0.040%
  • Sulfur (S) ≤ 0.040%
  • Vanadium (V) 0.02~0.15%
  • Q345B grade is subjected to impact testing at 20 degrees Celsius under normal conditions.

Q345C Grade

Q345C grade typically contains:

  • Carbon (C) ≤ 0.20%
  • Manganese (Mn) 1.0~1.6%
  • Silicon (Si) ≤ 0.55%
  • Phosphorus (P) ≤ 0.035%
  • Sulfur (S) ≤ 0.035%
  • Vanadium (V) 0.02~0.15%
  • Aluminum (Al) ≥ 0.015%
  • Q345C grade is subjected to impact testing at 0 degrees Celsius.

Q345D Grade

Q345D Grade

Q345D grade typically contains:

  • Carbon (C) ≤ 0.20%
  • Manganese (Mn) 1.0~1.6%
  • Silicon (Si) ≤ 0.55%
  • Phosphorus (P) ≤ 0.030%
  • Sulfur (S) ≤ 0.030%
  • Vanadium (V) 0.02~0.15%
  • Aluminum (Al) ≥ 0.015%
  • Q345D grade is subjected to impact testing at -20 degrees Celsius.

Q345E Grade 

Q345E grade typically contains:

  • Carbon (C) ≤ 0.20%
  • Manganese (Mn) 1.0~1.6%
  • Silicon (Si) ≤ 0.55%
  • Phosphorus (P) ≤ 0.025%
  • Sulfur (S) ≤ 0.025%
  • Vanadium (V) 0.02~0.15%
  • Aluminum (Al) ≥ 0.015%
  • Q345E grade is subjected to impact testing at -40 degrees Celsius.

Applications of Q345 Steel

Applications of Q345 Steel

Q345 steel, as a high-strength low-alloy structural steel, plays a significant role in various sectors such as construction, transportation, energy, and more. It is instrumental in a wide range of engineering projects, contributing significantly to their success and reliability.

Shipbuilding

Q345 steel, with its excellent tensile strength and resistance to seawater corrosion, is commonly used in shipbuilding.

Pipeline Manufacturing

Q345 steel, known for its high compressive strength and corrosion resistance, is frequently employed in the manufacturing of pipelines for energy sectors such as oil and natural gas. It ensures that pipelines are less susceptible to deformation, rupture, and other issues during long-term operation.

Mechanical Manufacturing                                                                       

Q345 steel exhibits excellent plasticity and abrasion resistance, making it commonly utilized in the manufacturing of industrial equipment, machinery components, and more.

Building and Bridge Structures                                                                                     

Q345 steel, with its high strength, ductility, and excellent corrosion resistance, is extensively used in various building and bridge structures.

Building and Bridge Structures 

 

Conclusion

With the ongoing progress in modern industry and advancements in technology, the demand for materials is reaching new heights. Research and improvement in material formulation, manufacturing processes, and performance enhancements for Q345 steel will continue to meet the evolving needs of various specific applications. Furthermore, as energy-saving and environmental protection principles become more prevalent, Q345 steel will attract increased attention and see wider utilization.

 

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