In the manufacturing of water pipeline joints, pipe fittings and valves , ductile iron is a widely used and important material. As a professional manufacturer, Judberd produces dismantling joints, pipe couplings, flange adaptors, saddle clamps, ductile iron pipe fittings, and ductile iron valves, selecting different ductile iron grades based on specific application conditions.
Among these grades, GGG40.3 (EN-GJS-400-18-LT) is specially designed for low temperature applications. So why does this material require special heat treatment? This article will explain in detail.
Special Requirements of Ductile Iron for Low Temperature Applications
In cold regions such as Northern Europe, North America, Russia, and Central Asia, underground water supply and drainage systems often operate under extreme sub-zero temperatures. Under such conditions:
The toughness of standard ductile iron decreases, making it prone to brittle fractures at low temperatures.
Ground settlement, thermal expansion, and contraction may cause minor pipe displacement; if the material lacks sufficient ductility, joints are likely to fail.
Therefore, ductile iron used in low temperature environments must meet two critical performance indicators:
Extremely high elongation (≥18%)
Excellent impact toughness at low temperatures
Why Does GGG40.3 Require Heat Treatment?
Although GGG40.3 castings already have certain mechanical properties in the as-cast state, there is still a certain proportion of pearlite and brittle structures. Heat treatment is required to optimize the microstructure and meet low temperature toughness requirements for the following reasons:
Improve low temperature toughness and prevent brittle fractures
Heat treatment eliminates pearlite, carbides, and other brittle phases, forming a uniform ferritic matrix; ferrite can maintain excellent toughness and elongation even at low temperatures.
Achieve high elongation to meet standards
The EN-GJS-400-18-LT standard requires elongation ≥18%, which can be reliably achieved through heat treatment.
Eliminate residual casting stresses and stabilize dimensions
Avoid long-term stress concentration, dimensional changes, deformation, and potential cracking during service.
Ensure consistency in mass production
Guarantee consistent microstructure and mechanical properties across production batches, ensuring stable quality.
The Adopted Heat Treatment Process — Ferritizing Annealing
For GGG40.3, the standard heat treatment process is Ferritizing Annealing, with the following steps:
Heating: Raise temperature to 900°C ~ 920°C
Holding: Maintain high temperature for 2 ~ 4 hours (adjusted according to casting wall thickness)
Slow cooling: Furnace cooling, controlled cooling rate at 10 ~ 20°C/h
Results after treatment:
Matrix structure fully transformed into ferrite;
Graphite nodules remain intact and evenly distributed;
Significantly improved low temperature impact toughness and elongation.
Why Other Heat Treatments Are Not Suitable
Normalizing: Not suitable — increases strength but reduces toughness, not recommended for low temperature use.
Quenching: Not suitable — creates hard and brittle structures, increasing brittleness.
Quenching + Tempering: Not suitable — used for high-strength ductile iron grades, but insufficient for low temperature ductility.
Summary
GGG40.3 (EN-GJS-400-18-LT) ductile iron must undergo ferritizing annealing to maintain excellent toughness and ductility even at temperatures as low as -20°C, -40°C, or below, preventing brittle failure and ensuring long-term safe operation of pipeline systems.
Judberd has comprehensive process control capabilities for ductile iron heat treatment, providing safe and reliable low temperature pipeline products for underground pipeline projects in cold regions.
Contact us: info@judberd.com
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