Q345B, Q345E, and Q345R are different grades of low-alloy high-strength steel according to the Chinese standard GB/T 1591. They have specific differences in their chemical compositions and applications. Here’s a detailed comparison:
1. Q345B (GB/T 1591):
- C (Carbon): ≤ 0.20%
- Si (Silicon): 0.15% – 0.50%
- Mn (Manganese): 0.60% – 0.90%
- P (Phosphorus): ≤ 0.045%
- S (Sulfur): ≤ 0.045%
- Cr (Chromium): ≤ 0.30%
- Mo (Molybdenum): ≤ 0.20%
- Ni (Nickel): ≤ 0.30%
2. Q345E (GB/T 1591):
- C (Carbon): ≤ 0.20%
- Si (Silicon): 0.15% – 0.50%
- Mn (Manganese): 0.60% – 0.90%
- P (Phosphorus): ≤ 0.045%
- S (Sulfur): ≤ 0.045%
- Cr (Chromium): ≤ 0.30%
- Mo (Molybdenum): ≤ 0.20%
- Ni (Nickel): ≤ 0.30%
Q345E has similar chemical composition to Q345B, but it is designed to have better toughness at low temperatures. It is used in applications that require high impact resistance in cold environments, such as structural components in cold climates.
3. Q345R (GB 713):
- C (Carbon): ≤ 0.20%
- Si (Silicon): 0.15% – 0.50%
- Mn (Manganese): 0.60% – 0.90%
- P (Phosphorus): ≤ 0.025%
- S (Sulfur): ≤ 0.025%
- Cr (Chromium): ≤ 0.30%
- Mo (Molybdenum): ≤ 0.20%
- Ni (Nickel): ≤ 0.30%
Q345R has similar composition to Q345B and Q345E but with stricter limits on P and S to ensure better performance under high-temperature conditions. It is specifically designed for pressure vessels and boilers, providing higher strength and durability at elevated temperatures.
Key Differences:
- Phosphorus (P) and Sulfur (S): Q345R has stricter limits for these elements, which improves its performance in high-temperature applications.
- Toughness: Q345E is optimized for better low-temperature toughness, while Q345B and Q345R have varying toughness requirements for different temperatures.
Applications:
- Q345B: Used for general construction and structural applications.
- Q345E: Designed for structures that need good toughness in low temperatures.
- Q345R: Used in high-temperature and high-pressure environments, such as pressure vessels and boilers.
Choosing the right grade depends on the specific engineering requirements and environmental conditions of the application.
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