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How is ductile iron generally welded?

Release time:

2024-07-25

Ductile iron differs from gray cast iron; it undergoes spheroidization treatment, which significantly improves its mechanical properties. It is mainly used to manufacture castings with high mechanical performance requirements and can also replace carbon steel or alloy steel within a certain range to produce high-strength, complex-shaped castings.

Ductile iron differs from gray cast iron in that its mechanical properties are significantly improved through spheroidization treatment. It is mainly used to manufacture castings with high mechanical performance requirements and can also replace carbon steel or alloy steel within a certain range to produce high-strength, complex-shaped castings. This requires that during welding, not only must welding defects be avoided, but also the strength of the weld must be considered to ensure good strength and plasticity. Ductile iron commonly uses magnesium alloys as spheroidizing agents, and magnesium is an element that hinders graphitization, which can lead to the formation of white cast structure during welding. This is one of the main difficulties in welding ductile iron. If the cooling rate during welding is too fast, the austenite in the heat-affected zone may transform into martensite, forming hardened structures that complicate post-welding processing. Due to the good strength and plasticity of ductile iron itself, cracks are generally not easy to form during welding; however, its welding quality requirements are higher than those for gray cast iron, making it relatively more difficult to weld. So how should it be welded well?

Arc Welding with Electrode

Generally, EZCQ (Z238) ductile iron electrodes can be used for welding. Preheat before welding at 500-700°C; after welding, normalizing or annealing treatment can be performed according to the requirements for base material structure. For cold welding of ductile iron, electrodes such as EZNiFe-1 (Z408) and EZNiFeCu (Z508) are mainly used for non-machined surface repairs; the process is similar to that of gray cast iron.

Gas Welding

When gas welding ductile iron, RZCQ type welding wire is used; for magnesium-containing ductile iron welding wire, its composition includes: C3.5-4.0%; Si3.5-3.9%; Mn0.5-0.8%; S≤0.03%; P≤0.10%; Mg0.035-0.06%; Y0.03-0.04%. A neutral flame or weak carburizing flame should be used, followed by slow cooling after welding.