S355JR and Q355B channels have identical welding properties, using the same processes and consumables:
Weldability Factors:
Carbon Equivalent (CE): S355JR (0.42) vs. Q355B (0.41)-both <0.45, so no preheating is needed for sections ≤25 mm.
Heat-Affected Zone (HAZ): Both form ductile ferrite-pearlite microstructures in the HAZ, avoiding brittle martensite. This prevents cracking in welded joints (e.g., channel-to-beam connections).
Consumable Compatibility: Both use E5015 (SMAW), ER50-6 (GMAW), and E501T-1 (FCAW) consumables-no need to source specialized materials.
Welding Parameters: Identical current/voltage settings (e.g., GMAW: 220–240 A, 28–30 V for 12 mm sections) work for both grades, reducing welder training costs.
Post-Weld Treatment: Neither grade requires post-weld heat treatment (PWHT) for standard applications, saving time and money.
This welding compatibility means Chinese fabricators can use existing equipment and expertise when substituting S355JR for Q355B.