Q: Which one has better impact toughness at low temperatures?
A: Standard grades have room-temperature properties. For low-temp service, specified grades like Q345D/E (for -20°C/-40°C impact) must be ordered. Q345 generally offers better low-temp toughness grades than Q235.
Q: What about corrosion resistance?
A: Both have similar, basic corrosion resistance as non-alloy steels. Protection (galvanizing, painting) is required for corrosive environments.
Q: Can both be used for ERW (Electric Resistance Welded) pipes?
A: Yes, both Q235 and Q345 are very common base materials for ERW pipes.
Q: Are they used for seamless pipes?
A: Primarily Q345 is common for hot-rolled seamless pipes (e.g., GB/T 8163). Q235 is less common for seamless, more typical for welded pipes.
Q: What is the typical heat treatment for these pipes?
A: As-delivered condition is usually hot-rolled or normalized for seamless. ERW pipes are as-welded. Annealing or normalizing can be specified for stress relief or improved properties.
