Shrinkage Rate of MIM Iron Alloy Materials

Iron-based materials are widely used in Metal Injection Molding (MIM) due to their good overall performance and relatively low production cost. When using MIM for iron-based materials, it is crucial to consider the shrinkage rate, as it affects the final part's dimensional accuracy and shape tolerance. The shrinkage in the MIM process primarily occurs during the debinding and sintering stages, with the most significant shrinkage happening during sintering.

Shrinkage Rate of MIM Iron Alloy Materials

For iron alloy materials (such as low carbon steel, low alloy steel, and stainless steel), the typical linear shrinkage rate during the MIM process is generally within the following ranges:

• Low Carbon Steel: 1.17 - 1.22 times the original dimension

• Alloy Steel: 1.15 - 1.20 times the original dimension

• Stainless Steel: 1.15 - 1.20 times the original dimension

Factors Affecting Shrinkage Rate

1. Binder System:

• Type and Content of Binder: The binder's type and content, as a percentage of the feedstock volume, affect the shrinkage of the sintered part.

2. Sintering Conditions:

• Sintering Temperature: Higher sintering temperatures typically lead to greater shrinkage rates.

• Sintering Time: Longer sintering times promote the densification of powder particles, increasing the shrinkage rate.

• Atmosphere: The atmosphere used during sintering (e.g., hydrogen, nitrogen, or vacuum) influences the material's densification and shrinkage behavior.

3. Powder Characteristics:

• Powder Particle Size and Shape: Finer powder particles usually exhibit higher shrinkage rates because they can pack more densely during sintering.

• Powder Density and Specific Surface Area: Powders with a high specific surface area may lead to higher shrinkage rates.

4. Material Composition:

• Content and Type of Alloying Elements: The content and type of alloying elements can affect the shrinkage rate. For example, the chromium and nickel content in stainless steel can increase the material's shrinkage rate.

Control and Prediction of Shrinkage Rate

To accurately control and predict the shrinkage rate of iron-based MIM parts, the following measures can be taken:

1. Precise Formulation: Control the formulation of materials precisely, including the ratio of powder to binder.

2. Strict Process Control: Regulate temperature, time, and atmosphere during debinding and sintering to minimize variability in shrinkage rate.

3. Experimental Validation: Conduct experimental validations in actual production, measure the shrinkage rate of real parts, and adjust process parameters based on experimental data.

4. Computational Simulation: Use computational simulation technologies (such as finite element analysis) to predict the shrinkage behavior and final dimensions of parts.

By employing these methods, the shrinkage rate of iron-based materials in MIM processes can be effectively controlled, ensuring dimensional accuracy and stability in part quality.