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II. Common Materials for MIM
One of the core advantages of MIM technology lies in its wide material adaptability. It covers almost all metal and alloy materials that can be made into powder. Specifically, they can be divided into the following categories:
- Structural steel category: It includes low-alloy steels (such as 42CrMo, 20CrMnTi, etc., suitable for stress-bearing structural parts), various stainless steels (such as 304, 316L, etc., which balance corrosion resistance and mechanical properties), and tool steels (such as high-speed steel, die steel, etc., with high hardness and wear resistance).
- High-temperature and special alloy category: Examples include nickel-based alloys (with high temperature resistance and corrosion resistance, often used in the aerospace field), titanium alloys (with high strength and low density, suitable for medical and aviation scenarios), and Kovar alloys (with expansion coefficient matching that of glass, widely used in electronic packaging).
- Functional and hard material category: It covers magnetic materials (such as ferrite, neodymium-iron-boron, used in electronic components), tungsten alloys (with high density and high melting point, suitable for counterweight and military fields), and hard alloys (such as tungsten carbide-based alloys, used for wear-resistant components like cutting tools and dies).
- Other materials: Besides metals and alloys, the MIM process can also be applied to non-metallic materials such as fine ceramics. It produces high-precision ceramic structural parts through a similar process flow.
| Material Category | Typical Grades/Compositions | Core Performance Characteristics | Main Application Fields |
|---|---|---|---|
| Iron-based Alloys | Fe-2Ni, Fe-8Ni, etc. | Good magnetic properties, heat resistance, relatively low cost, and excellent formability | Automotive industry (e.g., sensor housings, transmission gears); machinery industry (e.g., small structural parts, connectors); home appliance field (e.g., motor components) |
| Stainless Steels | 316L, 17-4PH, 420, 440C, etc. | Excellent corrosion resistance, high strength, good surface finish; some grades feature wear resistance or high-temperature resistance | Medical devices (e.g., surgical instruments, implant accessories); watch parts (e.g., watch cases, strap buckles); electronic equipment (e.g., connectors, shielding covers); kitchen utensil accessories |
| Cemented Carbides | WC-Co (Tungsten Carbide-Cobalt) series | Extremely high hardness, high strength, outstanding wear resistance and impact resistance, high-temperature resistance | Cutting tools (e.g., micro-drills, milling cutters); watch parts (e.g., wear-resistant gears, hand shafts); mold accessories (e.g., small punches) |
| Ceramics | Al₂O₃ (Alumina), ZrO₂ (Zirconia), SiO₂ (Silica) | High-temperature resistance, chemical corrosion resistance, good insulation, high hardness; some ceramics (e.g., zirconia) have good toughness | IT electronics (e.g., chip carriers, insulating bases); daily necessities (e.g., ceramic knives, tableware accessories); watches (e.g., ceramic bezels, cases); precision instrument components |
| Heavy Alloys | W-Ni-Fe, W-Ni-Cu, W-Cu (Tungsten-Copper) | High density (especially tungsten-based alloys), good thermal conductivity (e.g., tungsten-copper), high strength, radiation resistance | Communication field (e.g., RF shielding parts, antenna counterweights); daily necessities (e.g., lighter flint holders, fishing tackle weights); medical equipment (e.g., radiation shielding parts); aerospace (e.g., balance weights) |
| Titanium Alloys | Ti (Commercially Pure Titanium), Ti-6Al-4V, etc. | High strength, low density (significant lightweight advantage), excellent corrosion resistance and biocompatibility | Medical field (e.g., artificial joints, orthopedic internal fixation plates, dental implant accessories); aerospace (e.g., engine blades, structural connectors); high-end sports equipment (e.g., bicycle parts, golf club heads) |
| Magnetic Materials | Fe (Pure Iron), Fe₅₀Ni (Permalloy-type), Fe-Si (Silicon Steel) | Excellent magnetic permeability, high saturation magnetic induction; some materials have soft magnetic properties (easy to magnetize and demagnetize) | Electronic components (e.g., transformer cores, inductor cores); sensor parts (e.g., magnetic shielding covers, yokes); motor parts (e.g., stator and rotor cores) |
| Tool Steels | 42CrMo4, M2 (High-Speed Steel), etc. | High hardness, high wear resistance, good hardenability and heat resistance, excellent fatigue resistance | Various tools (e.g., micro-taps, screwdriver bits, mold ejector pins); mechanical equipment (e.g., wear-resistant guide rails, bearing rings); automotive industry (e.g., engine valve guides, gear-cutting tools) |
III.MIM Manufacturing Process Description
IV. Technical Features of MIM Process
The core process of Metal Injection Molding (MIM) works as follows: First, mix metal powder (such as stainless steel powder) with plastic binder evenly. Then, use injection molding technology to create green parts with the same complexity as plastic products. Next, remove the plastic component from the green parts through thermal debinding or solvent debinding. Finally, conduct high-temperature sintering on the debinded green parts. Compared with the traditional compacted powder metallurgy method, MIM process has obvious advantages. Because the mixture of metal powder and plastic binder fills the mold evenly, the sintered products have no density difference between the surface and the center. This allows stable production of precision parts with uniform and high density.
V. Technical Advantages of MIM Process
As an efficient near-net-shape technology for producing high-quality precision parts, MIM relies on its unique process principle. It shows unparalleled advantages over conventional powder metallurgy, machining and precision casting methods – especially in manufacturing near-net-shape products with 3D complex geometries, uniform structures and high performance. The specific advantages are as follows:
- Strong Forming Capacity: It can realize one-time forming of small and complex parts, just like producing plastic products. No multiple subsequent processing procedures are needed. The applicable product weight ranges from 0.1g to 500g. It should be noted that the heavier the product, the higher the proportion of material cost in the total cost, and the longer the overall production process takes.
- Excellent Product Performance
- High Structural Uniformity: The structure of each part of the product is highly uniform, with no obvious performance differences.
- High Dimensional Accuracy: It controls dimensional tolerance precisely, which can meet the strict requirements of precision parts.
- Outstanding Density and Mechanical Properties: The relative density of products can reach 95% - 99.5% (mixed density), close to the level of cast or forged parts. This brings excellent mechanical properties, such as high strength, high hardness and high elongation. At the same time, the products have good wear resistance and fatigue resistance, and can adapt to complex working conditions.
- Significant Advantages in Cost and Appearance
- Low Comprehensive Cost: Due to the high one-time forming rate, it reduces the costs of equipment, labor and material loss in subsequent processing links. This makes the overall product cost more competitive.
- Good Surface Quality: It has high surface finish, with surface roughness (Ra) less than 5μm. No additional surface polishing or other treatment procedures are needed to meet the appearance requirements of most application scenarios.
- High Sintering Precision: The sintered products have strong dimensional stability. The general precision can be controlled within 0.003 - 0.005 inch/inch, and the precision of high-precision products is even less than 0.05%.
- High Production Efficiency and Automation Level
- Strong Production Stability: Standardized process flow ensures small fluctuations in product quality and high consistency between batches.
- Outstanding Production Efficiency: The process is simple and compact. The flow from raw material mixing to finished product output is smooth, enabling continuous production.
- High Raw Material Utilization Rate: The mixture of metal powder and binder has almost no waste during the forming process. Its raw material utilization rate is much higher than that of traditional processing methods.
- Easy Large-Scale Production: The process links are easy to realize automatic control. By equipping with automatic production lines, it can quickly achieve mass and large-scale production to meet the huge market demand for precision parts.
- Wide Material and Application Range
- Strong Material Adaptability: It is not only applicable to various conventional alloy materials, but also compatible with multiple mixed materials and materials with special properties. This breaks the limitations of traditional processes on material selection.
- Diverse Application Scenarios: It can meet the needs of different fields for precision parts with complex geometries. It is widely used in electronics, automotive, aerospace, medical, military and other industries
- Strong Structural Adaptability: It can produce parts with a minimum thickness of more than 0.5mm. This can meet the design requirements of lightweight and thin products, while ensuring the structural strength of the parts.
- High Material Performance Plasticity: By virtue of flexible material formulas and process adjustments, it can produce products with various special properties. These include high strength, high toughness, high hardness, high temperature resistance, excellent electrical conductivity, magnetism, high thermal conductivity and low thermal expansion. It can accurately meet the personalized performance requirements of parts in different industries.
VI. Application Fields of MIM Technology
- Computers and auxiliary equipment: Parts like printer components, magnetic cores, plunger pins, and drive parts.
- Tools: Items such as drills, tool bits, nozzles, gun drills, spiral milling cutters, punches, sleeves, wrenches, electrical tools, and hand tools.
- Household appliances: Components including watch cases, watch bands, electric toothbrushes, scissors, fans, golf club heads, jewelry links, ballpoint pen clips, and cutting tool bits.
- Medical equipment parts: Products like orthodontic brackets, scissors, and tweezers.
- Military parts: Components such as missile fins, gun parts, warheads, and shaped charge liners.
- Electrical parts: Items like micro-motors, electronic components, and sensor parts.
- Mechanical parts: Parts for equipment such as cotton openers, textile machines, crimping machines, and office machinery.
- Automotive and marine parts: Components including clutch inner rings, shift fork sleeves, distributor sleeves, valve guides, synchronizer hubs, and airbags.
