Welding Preheating and Heat Treatment of P355GH steel

It is easy to produce a hardened structure, if the cooling rate of P355GH steel is too fast during welding, and the interlayer brittleness increases, it will lead to cracks. In order to slow down the welding cooling rate, reduce the generation of hardened structure and the appearance of cracks, pre-weld preheating and welding heat treatment must be carried out.

(1) Welding Preheating: P355GH steel should be preheated before welding. The preheating temperature should be 150~200°C. The preheated heating area should be on both sides of the weld bead, and the width shall be more than 1.5 times the thickness of the weldment at the welding place, and not less than 100mm.

(2) Heat Treatment of P355GH steel: Heat treatment immediately after welding, the method is that heat to 250~300°C within 100mm on both sides of the weld, then cover with 50mm thermal insulation cotton, and slowly cool to room temperature. The holding time is not less than 2 hours.