How to Improve Magnesium Recovery in Foundry

Magnesium (Mg) plays a vital role in the production of ductile iron by transforming flake graphite into spheroidal graphite, significantly enhancing the mechanical properties of the cast metal. However, one of the biggest challenges in ductile iron treatment is achieving high magnesium recovery due to Mg’s low boiling point and high reactivity.

In this guide, we explore scientifically backed, industry-verified strategies to improve magnesium recovery in foundry operations. Whether you are a metallurgist, process engineer, or purchasing manager, this article provides actionable insights and practical approaches to optimize nodulizer use, reduce fading, and enhance casting performance.

Why Magnesium Recovery Matters in Foundries

Magnesium is a volatile element, and during the nodularization process, a large portion of Mg may be lost to vaporization or slag formation. Poor magnesium recovery leads to:

• Inefficient use of expensive nodulizers

• Poor nodularity and inconsistent graphite morphology

• Increased casting defects such as carbides or shrinkage

• High treatment cost due to overcompensation

Improving magnesium recovery not only enhances metallurgical quality but also reduces material costs and ensures consistent production results.

Key Factors Affecting Magnesium Recovery

Several metallurgical and operational factors determine the success of magnesium retention during treatment:

1. Nodulizer Composition and Type

The chemical composition and alloy matrix of the nodulizer directly affect Mg release and absorption. For example:

• FeSiMg with rare earths (RE) improves stability during reaction

• Low-aluminum, low-titanium nodulizers reduce slag formation

• High-density nodulizers melt slower, allowing controlled Mg diffusion

Recommended Product: Ferro Silicon Magnesium Nodulizer

2. Treatment Method (Ladle vs. In-the-mold)

• Ladle treatment is more common but may result in higher Mg losses due to violent reactions.

• In-the-mold (ITM) nodularization can achieve over 90% magnesium recovery, especially for small castings.

ITM is less suitable for large-scale operations but ideal for precision parts.

3. Pouring Temperature

Higher temperatures accelerate magnesium vaporization. Ideally, molten iron should be treated between 1400°C and 1500°C, balancing fluidity and reaction control.

Too high temperatures (>1550°C) drastically reduce recovery rates.

4. Reaction Control and Slag Management

• Use of covering agents or treatment slag minimizes exposure to air

• Maintain a clean ladle lining and proper slag skimming

• Use of anti-reaction cones reduces splash and uncontrolled reactions

Effective Strategies to Improve Magnesium Recovery

1. Optimize Nodulizer Size and Addition Method

• Granule size between 3–10 mm is preferred for ladle treatment

• Gradual feeding improves contact time and reduces violent reaction

• Preheating nodulizers slightly (to 200–300°C) improves melting behavior

2. Use High-performance Treatment Alloys

Alloys with enhanced Mg-RE ratios and lower impurities improve reaction stability and reduce fading.

3. Improve Ladle Design

• Use ladles with conical bottoms to ensure better alloy dispersion

• Insulated or covered ladles reduce heat loss and Mg fading

• Minimize treatment time to reduce exposure to oxygen

4. Monitor Treatment Parameters with Precision

• Use thermocouples to monitor melt temperature in real-time

• Implement oxygen and sulfur sensors to fine-tune Fe-Si-Mg ratio

• Automate nodularization to minimize human error

The Role of Rare Earth Elements (RE) in Magnesium Retention

Adding trace levels of cerium (Ce) and lanthanum (La) improves nodulizer stability and promotes cleaner reaction interfaces. RE elements form stable oxysulfides, helping to:

• Trap sulfur and reduce MgS formation

• Encourage smoother Mg diffusion

• Reduce violent reactions

Case Study: Boosting Mg Recovery by 20% Using Modified FeSiMg

In a mid-size foundry producing automotive ductile iron parts, switching from standard FeSiMg to a low-aluminum, RE-enhanced nodulizer and modifying the ladle design increased average Mg recovery from 42% to 63%, while reducing nodulizer consumption by 15%. This led to:

• Material cost savings of 12%

• 30% reduction in shrinkage-related defects

• Improved dimensional stability in thin-walled castings

Common Magnesium Recovery Problems and How to Fix Them

Choosing the Right Supplier for Consistent Results

Sourcing nodulizers from a reputable ferroalloy supplier is essential. Look for:

• ISO-certified production processes

• Precise control over granule size and Mg content

• Technical support and metallurgical consulting

• Proven performance in ductile iron applications

About Hongshun Industrial

Hongshun Industrial Co., Ltd. is a leading manufacturer of ferroalloys and nodulizing agents, offering a wide range of magnesium-rich alloys, ferro silicon magnesium nodulizers, and customized solutions for ductile iron casting. Our products are optimized for high Mg recovery, low fading, and stable graphite structure.

With over 20years of export experience to Europe, the Middle East, and Southeast Asia, Hongshun provides:

• On-site technical support

• Tailored alloy formulations

• Flexible packaging and global delivery

• Data-driven quality control

???? Contact us today to get a quote or discuss your nodularization challenges.

Improving magnesium recovery in foundry operations is both a science and a craft. By optimizing nodulizer choice, refining treatment methods, and working with experienced suppliers, foundries can achieve consistent ductile iron quality, reduce waste, and enhance productivity. Every percent of Mg recovery saved is a step toward better castings and lower costs.