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Everything About Soft Magnetic Alloys

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:

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% *
* of the nominal dimension

 

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.

  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