About Metal Injection Moldings
Metal Injection Moulding (MIM) is economically attractive to manufacturers-especially against parts that require machining. Machined parts require a considerable amount of labor and a lot of material is lost during the process. When parts are molded in mass quantities, MIM-type parts can offer substantial savings. Furthermore, the more complex the part, the more cost reduction the customer can realize.
The quest for industrialization and automation has seen the development of various manufacturing technologies. While traditional methods like machining, stamping, forging, casting and powder metallurgy remain important,MIM is fast becoming an integral process in metal forming.
Comparison of MIM to conventional metal-forming processes
| Parameters | PIM/MIM | Power Metalliurgy | Casting | Machining | Stamping |
| Density | 98% | 86% | 98% | 100% | 100% |
| Tensile Strength | High | Low | High | High | High |
| Surface Finish | High | Medium | Medium | High | High |
| Miniaturization | High | Medium | Low | Medium | High |
| Thin Wall Capability | High | Medium | Medium | Low | High |
| Complexity | High | Low | Medium | High | Low |
| Design Flexibility | High | Medium | Medium | Medium | Low |
| Production Quantity | High | High | Medium | Med-High | High |
| Range of Materials | High | High | Med-High | High | Medium |
| Affordability | High | High | Medium | Low | High |
MIM Advantage
Almost any high melting point ferrous metal that can be produced in a suitable powder form can be processed by MIM. MIM offers the following benefits:
- Attractive cost savings
- Wide latitude of part shape, sizes ( 0.1g to 250g) and design
- Ability to combine functions and eliminate sub-assemblies
- Good dimensional control with close tolerances of +/- 0.5%
- Net shape production, eliminating or minimizes machining
- Wide range of available alloys, composites and properties
- Cost efficient for moderate-to-high production volume
- Suitable for intricate and complex Geometries
- High Material Density and Strength
- Design Flexibility
- Produce Good Surface Finishes
MIM technology combines the shape making capabilities of plastic injection molding with the material flexibility of powder metallurgy. Taking advantage of unique process capabilities, it allows the combining of two or more components into one complex geometry or co-molding and bonding dissimilar materials. Combining fine metal powders with a "binder" system, components are injection molded, de-bound and sintered, resulting in high-density, complex, precisely-shaped parts exhibiting properties approaching that of wrought material. Alloy and stainless steel, as well as other non-ferrous alloys such as titanium, are common materials for MIM.
MIM Tolarence
MIM components can range in size from 0.1 grams to over 150 grams in weight. Mold construction may consist of either single or multiple cavities depending upon the estimated annual volume.
| Measuring tolerances | |
| Nominal dimension [mm] | Tolerance +/- [mm] |
| < 3 | 0,05 |
| 3 - 6 | 0,06 |
| 6 - 15 | 0,075 |
| 15 - 30 | 0,15 |
| 30 - 60 | 0,25 |
| > 60 | +/-0,5% * |
| Form an positional tolerances | |
| Straightness Parallelity Levelness | 0,5% of the longest dimension |
| Angle | +/- 0° 30' |
| Radii | +/- 0,3 mm |
| Surface roughness | Rz 8-12 |
MIM Material
MIM
is used by many industries-such as medical device, telecommunications,
electronics and automotive parts manufacturers-and is a viable and
cost-effective alternative to other types of metal processes, such as
machining and casting. The MIM process is particularly well suited for the
high-volume manufacture of relatively small, complex components requiring
high strength, high performance and cost efficiency.
| Material Group | Alloy/Material | Description |
| Low Alloy and Alloy Steels | · 2% Nickel-Iron (MIM 2200) · 7% Nickel-Iron (MIM 2700) · 4130 (Cr-Mo steel) · 4340 (Ni-Cr-Mo steel) | Possess good strength, fatigue resistance, and high surface hardness. |
| Austenitic Stainless Steels | · Type 304L · Type 316L | Possess excellent cryogenic properties, superior corrosion resistance, and good high-temperature strength. |
| Ferritic Stainless Steels | · Type 430L | Possess good corrosion, heat resistance, good machinability and magnetic properties. |
| Martensitic Stainless Steels | · Type 420 · Type 440C · 440-XH Alloy* | Designed to provide stainless properties with excellent hardness, strength and wear resistance. |
| Precipitation Hardening Stainless Steels | · 15- 5 PH · Custom 630 (17- 4 PH) | High strength, toughness and hardness, with excellent corrosion resistance. |
| Soft Magnetic Materials | · 2% Nickel-Iron · 50% Nickel-Iron · 80% Nickel-Iron · Nickel-Zinc Ferrite · 3% Silicon-Iron | High permeability, low loss magnetic alloys. |
| Controlled Expansion and Sealing Materials | · Carpenter Invar "36" Alloy* · Carpenter Low Expansion " 42" Alloy* · Carpenter High Permeability " 49" Alloy* · Carpenter HyMu "80" Alloy* · Kovar Alloy (F-15 Alloy)* · 50% Nickel-Copper | Uniform and low thermal expansion alloys. |
| Tool Steels | · Micro-Melt M2 Alloy* · Micro-Melt M4 Alloy* | High hardness and wear resistance, often accompanied by high toughness and resistance to softening at elevated temperature. |
| Medical Alloys | · BioDur CCM Plus Alloy* · BioDur Carpenter CCM Alloy* | Non-magnetic, cobalt-chromium-molybdenum alloys exhibiting high strength, corrosion resistance and wear resistance. |
| Heat-Resistant Alloys | · Type 310C · HK30 (Nb) · Pyromet 718* | Developed for high temperature and oxidation resistance and where relatively high stresses (tensile, thermal, vibratory, or shock) are encountered. |
| Titanium | · CP Titanium · Ti-6Al- 4V | Lightweight, high-strength, corrosion-resistant material. |
| Ceramics | · Aluminum Oxide (Alumina) · Zirconium Oxide (Zirconia) · Zirconium Oxide stabilized with MgO, CaO, or Y 2O3 · Ruby (98% Alumina, 2% CrO) · Zirconia Toughened Alumina · Alumina Toughened Zirconia | Developed for high hardness and wear resistance. |
| Cermets | · Titanium Carbonitride T10N · Titanium Carbonitride T15N | High resistance to wear, corrosion and oxidation. |
Typical Mechanical Properties of Alloys
| Material Group | Alloy* | Yield Strength (MPa) | UTS (MPa) | Elongation (%) | Density (g/cm3) | Hardness |
| Low Alloy & Alloy Steels | MIM-2200 (Fe-2%Ni) as-sintered | 140 | 300 | 35 | 7.60 | 45 HRB |
| Low Alloy & Alloy Steels | MIM-2200 (Fe-2%Ni) Heat treated** | 200- 600 | 380- 650 | 2 to 20 | 7.60 | > 55 HRC (surface) |
| Low Alloy & Alloy Steels | MIM-2700 (Fe-7%Ni) as-sintered | 300 | 390 | 25 | 7.60 | 70 HRB |
| Low Alloy & Alloy Steels | MIM-2700 (Fe-7%Ni) Carbo-nitrided | 670 | 830 | 9 | 7.60 | > 55 HRC (surface) |
| Stainless Steels | MIM-316L | 180 | 500 | 50 | 7.80 | 67 HRB |
| Stainless Steels | 304 L | 140 | 500 | 70 | 7.75 | 60 HRB |
| Stainless Steels | MIM-17-4 PH As-sintered | 730 | 900 | 6 | 7.60 | 25 HRC |
| Stainless Steels | MIM-17-4 PH Heat-treated (H 900) | 1100 | 1200 | 5 | 7.60 | 36 HRC |
| Stainless Steels | 420 HIP抏d + Heat Treated | 1500 | 1800 | 3 | 7.70 | 52 HRC |
| Soft Magnetic Alloys | MIM-430L | 240 | 410 | 25 | 7.50 | 65 HRB |
| Soft Magnetic Alloys | MIM-Fe-3%Si | 360 | 530 | 30 | 7.50 | 80 HRB |
| Soft Magnetic Alloys | MIM-Fe-50%Ni | 160 | 450 | 30 | 7.70 | 50 HRB |
| Controlled Expansion Alloy | Kovar (F-15 Alloy) | 300 | 450 | 35 | 8.0 | 75 HRB |
| Other Alloys | Pyromet 718 | 1150 | 1350 | 14 | NA | NA |
* Alloys with MIM prefix are also listed in the MPIF
Standard 35 (2005 edition) Materials Standard for
Metal Injection Molded Parts
** Depending on the
type of heat treatment a range of mechanical properties can be obtained in
MIM-2200 and MIM-2700
Typical Magnetic Properties of Alloys
| Alloy | Density (g/cm) | Maximum Permeability, max | Coercive Field Hc (Oe) | Residual Induction Br (kG) | Induction, B(kG) @ H=5 Oe 10 Oe 15 Oe |
| MIM- 2200 | 7.75 | 3,300 | 1.50 | 7.7 | 12.0 14.0 15.2 |
| MIM- 2700 | 7.85 | 1,700 | 2.30 | 6.2 | 7.8 11.5 13.9 |
| MIM-Fe- 50%Ni | 8.0 | 30,000 | 0.17 | 6.5 | 11.4 12.5 12.9 |
| MIM-Fe- 3%Si | 7.55 | 6,700 | 0.69 | 8.7 | 12.5 13.5 14.0 |
| MIM- 430L | 7.60 | 5,000 | 0.67 | 7.3 | 9.75 10.5 11.0 |
1 oersted (Oe) = 79.55 ampere/meter (A/m)
1 kilogauss (kG) = 0.1 tesla (T)
Nominal Chemical Composition (%) of Common Alloys
| Alloy* | Fe | Ni | Cr | C | Si | Mo | Cu | Mn | Others |
| MIM- 2200 | Bal | 1.5- 2.5 | ? | 0.05 max | 1.0 max | 0.5 max | ? | ? | ? |
| MIM- 2700 | Bal | 6.5- 8.5 | ? | 0.05 max | 1.0 max | 0.5 max | ? | ? | ? |
| MIM- 316L | Bal | 10- 14 | 16- 18 | 0.03 max | 1.0 max | 2- 3 | ? | 2.0 max | ? |
| 304 L | Bal | 8- 12 | 18- 20 | 0.03 max | 1.0 max | ? | ? | 2.0 max | ? |
| MIM- 17-4 PH | Bal | 3- 5 | 15.5- 17.5 | 0.07 max | 1.0 max | ? | 3- 5 | 1.0 max | 0.15- 0.45 (Nb+Ta) |
| 420 | Bal | ? | 12- 14 | 0.20- 0.35 | ? | ? | ? | ? | ? |
| MIM- 430 L | Bal | ? | ? | 0.02 max | 2.5- 3.5 | ? | ? | ? | ? |
| MIM-Fe- 50%Ni | Bal | 49- 51 | ? | 0.02 max | 1.0 max | ? | ? | ? | ? |
| Kovar (F- 15 Alloy) | Bal | 29- 30 | ? | 0.04 max | ? | ? | ? | ? | 16- 17 Co |
| Ti- 6Al-4V | Ti Bal | ? | ? | ? | ? | ? | ? | ? | 5.5- 6.7 Al, 3.5-4.5 V |
* Alloys with MIM prefix are also listed in the MPIF Standard 35 (2005 edition) Materials Standard for Metal Injection Molded Parts Materials Standard for Metal Injection Molded Parts
Microstructure Comparison
Fe-50%Ni,100X, polished, etched
Titanium MIM
Titanium (Ti) is a high-density strength, highly pliant, highly corrosive-resistant material, which in recent years is seeing ever-growing demand. On the downside, titanium is a difficult material to process and also an expensive one.
- Parts from 2 mm up to approximately 150 mm maximum dimension
- Maximum section thickness about 18 mm
- High mechanical strength
- CP titanium (un-alloyed titanium) and titanium 6/4 (Ti-6Al-4V) available now
- Suited to part runs from 1,000 to 1,000,000s
- Ideal for complex, difficult to machine parts
| MIM Ti Sintered Parts | JIS3-type Standard | |
| Relative density (%) | 97 | 100 |
| Elasticity (NPa) | 600± 20 | 480~ 620 |
| Growth (%) | 21± 2 | >= 18 |
| 0.2% durability (NPa) | 310± 39 | >= 345 |
| Hardness (Hmv) | 240± 29 | - |
Stainless Steel MIM
| Grade | Type | Description | Applications |
| MIM 430L | Ferritic | Provides a relatively low cost solution for resistance to atmospheric corrosion and general oxidation | Magnetic probes, sensors, armatures, and pole pieces that require some resistance to corrosion |
| MIM 316L | Austenitic | Provides excellent toughness, ductility, and corrosion resistance | Medical and dental devices, marine components, and non-magnetic housings |
| 17-4PH | Precipitation Hardening | Provides an excellent combination of strength, hardness, and corrosion resistance | Ordnance components, high strength fasteners, fiber optic connectors, and medical devices |
Martensitic stainless steels provide high strength and hardness with moderate corrosion resistance. Typical applications include wear plates, fuel injection nozzles, and cutting instruments. Eversun Specialties does not currently offer any MIM martenistic alloys.
Soft Magentic Alloys
Soft Magnetic Alloys are ferromagnetic materials that are easily magnetized and de-magnetized. To provide optimal magnetic performance, these alloys possess very low levels of carbon, nitrogen, and oxygen. They rely on various additions of nickel, silicon, or cobalt to optimize permeability, coercive force, or induction.
| Grade | Type | Description | Applications |
| MIM Fe MIM 2200 |
Iron | Provides a relatively cost effective solution for high magnetic output, with lower strength and hardness | Pole pieces, sensor probes, and solenoid end caps |
| MIM 2700 MIM Fe50Ni |
Nickel-Iron | Provides increased permeability and reduced coercive force | Pole pieces, cores, and relays for use with low magnetizing forces |
| MIMFe3SI | Silicon-Iron | Provides similar magnetic output to iron, but with lower coercive force and higher permeability | Solenoid switches, armatures, pole pieces, and relays that require medium electrical resistivity, high initial permeability, and low hysteresis loss |
| MIM 430L | Ferritic | Combines good magnetic output with corrosion resistance | Magnetic probes, sensors, armatures, and pole pieces that require some resistance to corrosion |
Compared with iron alloys, cobalt-iron alloys provide increased magnetic saturation and permeability. The addition of cobalt creates a significantly stronger alloy with a higher hardness than other magnetic steels. Typical applications include magnetic cores that require high permeability with high flux densities and faster response, higher strength solenoid switches, and armatures.
Low Expansion Alloys
| Grade | Type | Dedcription | Applications |
| MIM Kovar (Fe 28Ni 18Co) |
Low Expansion | Kovar possess a relatively low coefficient of linear expansion in a specific temperature range | Kovar parts include bi-metal strips, glass to metal seals, superconducting systems, and compensating pendulums |
Low Alloy Steel
| Grade | Type | Description | Applications |
| MIM 2200 | Low Carbon Steel | Provides outstanding toughness and ductility; carburized surface provides an excellent wear surface with a tough core | Lubricated safety and security devices, automotive interior components, and coated or plated hardware |
| MIM 2700 | Low Carbon Steel | Provides increased strength and toughness; carburized surface provides an excellent wear surface with a tough core | Lubricated safety and security devices, automotive interior components, and coated or plated hardware |
Medium carbon low alloy steels achieve their high strength and hardness through heat treatment. Typical applications include firearm triggers and sears, fasteners, and electric tool components.
Article courtsey of Eversun Advanced Forming Technology