Q235 welding rods:
A: E43 series (E4303, E4315, etc.).
Q235 welding requires preheating?
A: Generally, preheating is not required; for thick plates (>50mm), low temperatures, or high restraint, preheat to 80~120℃.
Q235 can be bolted?
A: Yes. Ordinary bolts are grade 4.8/8.8; high-strength bolts are generally not directly used with Q235.
Q235 corrosion protection methods?
A: Rust removal (Sa2.5/St3) + primer + topcoat; or hot-dip galvanizing, epoxy coating.
Q235 fire protection methods?
A: Fire-retardant coating (thin/thick type), fireproof board wrapping, concrete encapsulation.