Key Aspects of Heat Treatment: Analysis of the Annealing Process for Jinmai Malleable Iron Pipe Fittings
Heat treatment is the core process in the production of malleable iron pipe fittings, directly determining the material’s toughness, strength, and service life. Among these processes, graphitization annealing is particularly crucial. Inferior annealing can lead to brittleness, easy cracking, and substandard mechanical properties, failing to meet engineering requirements. Hebei Jinmai Malleable Iron Co., Ltd. possesses industry-leading intelligent annealing furnace equipment and mature graphitization annealing technology. A senior technical team oversees the entire process, precisely controlling process parameters to ensure accurate annealing and create high-performance malleable cast iron pipe fittings.
Jinmai Malleable Iron’s graphitization annealing process consists of three precisely controlled stages: The first stage is the uniform heating stage. After the pipe blank is placed in the annealing furnace, the temperature is uniformly increased to approximately 950℃ at a rate of 50-80℃ per hour. This avoids excessive temperature differences between the inside and outside of the blank due to rapid heating, which could cause thermal stress cracking and ensure uniform heating of the entire blank. The second stage is the isothermal graphitization stage, where the material is kept at a constant temperature of 950℃ for 8-12 hours. This allows the graphitization chemical reaction to fully occur within the blank, gradually transforming free carbon elements into a flocculent graphite structure and completely eliminating brittle white iron structure. This is the core step in improving the material’s toughness, and precise control of the isothermal duration and temperature directly affects the material’s performance. The third stage is the slow cooling stage. After the isothermal treatment, the heating system is turned off, and the furnace temperature is slowly reduced to room temperature at a rate of 30-50℃ per hour. This allows the pipe blank to cool naturally, fully eliminating internal stress and preventing rapid cooling from causing the material to harden, become brittle, and crack. Through this professional and rigorous annealing process, Jinmaima steel pipe fittings achieve a tensile strength ≥330MPa, elongation ≥8%, excellent toughness, and outstanding resistance to impact, vibration, and thermal expansion and contraction, ensuring the core quality of the product from the very source of the process.
Post time: Jun-25-2026