What are the composition and heat treatment characteristics of Q355GNH weathering steel plate?

1. Q355GNH weathering steel plate composition characteristics

(1) Low carbon: Due to the high requirements for toughness, weldability and cold formability, its carbon content does not exceed 0.20%.

(2) Add manganese-based alloying elements.

(3) Adding auxiliary elements such as niobium, titanium or vanadium: a small amount of niobium, titanium or vanadium forms fine carbides or carbonitrides in the Q355GNH weathering steel plate, which is beneficial to obtain fine ferrite grains and increase the strength of steel and resilience.

In addition, adding a small amount of copper (≤0.4%) and phosphorus (about 0.1%) can improve the corrosion resistance of Q355GNH weathering steel plate. Adding a small amount of rare earth elements can desulfurize and degas, purify steel, improve toughness and process performance.

2. Heat treatment characteristics: Q355GNH weathering steel plate is generally used in hot-rolled and air-cooled conditions, and no special heat treatment is required. The microstructure in use is generally ferrite-sorbite.