The heat treatment process of seamless steel pipes

In the production process of seamless steel pipes, heat treatment is a critical step to ensure product quality and performance. Haihao Group, with its outstanding expertise and technical strength, demonstrates unique heat treatment technology in the field of pipeline systems.

Preheating Process: Haihao Group recognizes the crucial role of preheating in reducing heat treatment deformation. To ensure uniform temperature inside and outside large seamless steel pipes, a two-stage preheating process is implemented. The first preheating temperature is 400–500°C with a holding time of 1 min/mm, and the second preheating takes place in a fully deoxidized salt bath furnace at 840–860°C with a holding time of 40–60s/mm.

The heat treatment process of seamless steel pipes

Quenching Heating and Cooling Process: Building upon sufficient preheating, the quenching heating temperature is chosen to be 980–1000°C. Uniform temperatures inside and outside are maintained, and the holding time is calculated at 15–20s/mm to minimize quenching deformation. To further reduce quenching deformation, Haihao Group implements thorough pre-cooling measures. After air-cooling to a faint two-color stage (around 830°C), seamless steel pipes are rapidly cooled in hot oil to 180–200°C, ensuring product quality.

Low-Temperature Tempering Process: To adjust hardness and meet technical requirements, Haihao Group holds the pipes in a nitrate bath at 180–220°C for 1–3 hours and then achieves the desired state through air-cooling. Tempering temperature and holding time are determined based on the hardness after quenching, ensuring product hardness within the range of 60–62 HRC and meeting technical requirements for deformation.

Through in-depth research and the application of exquisite technology in the heat treatment process of seamless steel pipes, Haihao Group demonstrates professionalism in the field of pipeline systems. The precise execution of this series of processes ensures high-quality products and outstanding performance, providing customers with reliable pipeline solutions.