The LPG cylinder heat treatment process involves three stages. In the preheating zone, welded cylinders are gradually heated to remove residual stresses and prepare for normalizing. In the main heating zone, cylinders are raised to the normalizing temperature (870-930°C) and held for a specified time to achieve complete austenitization of the steel. In the cooling zone, cylinders are cooled in a controlled manner (typically in still air) to achieve the desired normalized microstructure with uniform grain size. The furnace uses gas-fired burners with zone-wise temperature control to ensure each cylinder receives identical thermal treatment. Conveyor or walking beam mechanisms transport cylinders through the furnace at calculated speeds to achieve the required soak times.