2016年MPIF金属注射成型零件材料标准概览

2016

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标题：“Materials Standards for Metal Injection Molded Parts 2016 英文版”是一份由MPIF（Metal Powder Industry Federation）发布的专业标准文档，针对金属注射成型零件的材料性能提供了详细的规定和指导。这份标准适用于粉末冶金制造领域，特别是关注用于结构件的粉末冶金过程（PM）、自润滑轴承的生产以及粉末锻造（PF）过程中制造的钢制组件。文档内容分为多个部分： 1. MPIF Standard 35: 标准定义了金属注射成型零件的基本材料标准，包括PM结构件、PM自润滑轴承以及PF钢制部件的标准。这些部分阐述了最低机械性能值、磁性性能和可控膨胀性能的最低要求。 2. 展示了如何通过实践方法来证明零件的性能，例如，给出了典型性能参数，如化学成分、机械性能、热处理、表面粗糙度、微观结构等。 3. 对于MIM（Metal Injection Molding）材料的指定和设计有明确的指南，这涉及到材料选择和等级选择的关键要素。例如，密度、极限抗拉强度、屈服强度、延伸率等机械性能参数的详细数值。 4. 提供了弹性常数（Young's Modulus E、Shear Modulus G 和 Poisson's Ratio ）等重要物理性质的定义，这些都是评估材料刚性和塑性的重要指标。 5. 还包括冲击能等关键性能指标，这对于理解和确保金属注射成型零件在实际应用中的耐冲击性和韧性至关重要。这份标准是粉末冶金行业专业人士必备的参考资料，它不仅为设计师、工程师和制造商提供了一致的质量基准，还帮助他们优化材料选择，提升产品的可靠性和使用寿命。对于那些在粉末冶金或金属注射成型工艺中工作的人来说，这份标准是确保产品质量和技术进步的关键工具。由于文档是英文版，对于非英语使用者，可能需要借助翻译工具或寻求专业解读来充分理解其内容。

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MPIF Standard 35, Metal Injection Molded Parts—2016 Edition

Typical Values

For each MIM material listed, a set of typical values is

shown for properties, e.g., density, hardness, elongation,

etc., some or all of which may be important for a specific

application. Typical values are shown for properties,

e.g., elongation, hardness, coercive field, etc., some or

all of which may be important for a specific application.

The property data were compiled from test specimens

processed by individual MIM producers.

The typical values are listed for general guidance

only. They should not be considered minimum values.

While achievable through normal manufacturing

processing, they may vary somewhat depending upon

the area of the component chosen for evaluation, or

the specific manufacturing process utilized. Those

properties listed under the “typical value section” for

each material which are required by the purchaser

should be thoroughly discussed with the MIM parts

manufacturer before establishing the specification.

Required property values, other than those expressed

as minimum should be separately specified for each

MIM part, based on its intended use.

Chemical Composition

The chemical composition of each material lists its

principal elements and allowable ranges.

Mechanical Properties

Mechanical property data indicate the minimum and

typical properties that may be expected from test

specimens conforming to the density and chemical

composition criteria listed. It should be understood that

mechanical properties used in this standard were

derived from individual test specimens prepared

specifically for material evaluation and sintered under

commercial production conditions.

Hardness values of heat treated specimens are given

first as apparent hardness and second, when available,

as equivalent particle or matrix hardness values.

Residual porosity found in MIM components will slightly

affect the apparent hardness readings. Microin-

dentation hardness values shown as Rockwell C were

converted from 100 g load (0.981 N) Knoop microin-

dentation hardness measurements.

Heat Treatment

MIM materials may be heat treated to increase strength,

hardness and wear resistance. The percentages of car-

bon, alloying elements and residual porosity determine

the degree of hardening possible. Tempering or stress

relief is required after quenching for optimum strength

and durability. Ferrous MIM parts processed with little

or no final carbon may be surface carburized for

increased surface hardness while retaining core

toughness. Martensitic and precipitation hardening

stainless steels may also be heat treated for increased

hardness and strength.

Most MIM materials respond well to normal wrought

heat treating practices and procedures. It is recommended

that the heat-treatment procedures for any MIM

material be established in cooperation with the MIM

part manufacturer to achieve the desired balance of

final properties in the finished part.

Surface Finish

The overall finish and surface reflectivity of MIM materi-

als depends on density, tool condition, particle size and

secondary operations. Effective surface smoothness of

as-sintered MIM components is usually better than an

investment cast surface. Surface finish can be further

improved by secondary operations such as coining,

honing, burnishing or grinding. The surface finish

requirements and methods of determination must be

established by mutual agreement between purchaser

and producer. (See MPIF Standard 58 for additional

details.)

Microstructure

MIM materials generally contain less than 5%

porosity, approaching the density of wrought materials.

The examination of the microstructure of a MIM part

can serve as a diagnostic tool and reveal the degree of

sintering and other metallurgical information critical to

the metal injection molding process. There are several

observations common to most sintered MIM materials,

as briefly described below. Comments on specific

materials will be found in the subsections devoted to

those particular materials.

Sintered parts are normally examined first in the

unetched condition. With a proper sinter, there will be

no original particle boundaries seen at 200X. Small,

uniformly distributed, well rounded discrete pores lead

to higher strength, ductility and impact resistance.

MIM Material Designation

The Metal Injection Molding Association has chosen

to use the designation system similar to AISI-SAE

where applicable. These designations were chosen

because MIM parts are likely to be used as

replacements for wrought products already in service.

When specifying a material made by the MIM process,

it should be so designated with a “MIM” prefix to the

material grade. For example, a part fabricated from

Type 316L stainless steel by MIM would be designated

as "MIM–316L".

Material Selection

Before a particular material can be selected, a careful

analysis is required of the design of the part and its

end use. In addition, the final property requirements of

the finished part should be agreed upon by the

manufa

cturer and the

purchaser of the MIM part.

Issues such as static and dynamic loading, wear

resistance, machinability and corrosion resistance may

also be specified.

5

MPIF Standard 35, Metal Injection Molded Parts—2016 Edition

Grade Selection

For certain magnetic materials, the material

designation will specify the material as either “Grade 1”

or “Grade 2”. The Grade 1 material, as compared with

Grade 2, will exhibit improved magnetic characteristics.

The difference between a Grade 1 and Grade 2

material can usually be found in the material’s

microstructure, with a high density, large grain size and

low amounts of interstitials (carbon, oxygen, nitrogen,

etc.) all contributing to improved magnetic properties.

A careful analysis of the design and function of the

part should determine what grade material is required

for a given application. It is recommended that a

discussion of the required magnetic performance take

place between the manufacturer and the purchaser

before the final grade selection.

Density

Density is expressed in grams per cubic centimeter

(g/cm

) and may be determined by various standardized

methods. Some common methods of MIM density deter-

mination include:

MPIF Standard 54: This method is generally used for

products that contain less than 2% porosity (impermeable

PM). It is based on the principle of water displacement.

MPIF Standard 63: This method comprises use of a

gas pycnometer. Any open porosity will not be included

as part of measured volume. The density obtained by

the gas pycnometer method will typically be higher than

the density obtained by water displacement.

MPIF Standard 42: This method is generally used for

PM products having surface-connected porosity and is

based on the use of Archimedes’ principle. MIM

materials generally contain less than 5% porosity, so

impregnation is not applicable.

Ultimate Tensile Strength

Ultimate tensile strength, expressed in 10

psi (MPa)

is the ability of a test specimen to resist fracture

when a pulling force is applied in a direction parallel to

its longitudinal axis. It is equal to the maximum load

divided by the original cross-sectional area. (See MPIF

Standard 50 for additional details.)

Yield Strength

Yield Strength, expressed in 10

psi, is the load at which

a material exhibits a 0.2% offset from proportionality on a

stress-strain tension curve divided by the original cross-

sectional area. (See MPIF Standard 50 for additional

details.)

Elongation

Elongation (plastic), expressed as a percentage of the

original gage length (typically 1.0 in. [25.4mm]), is

based on measuring the increase in gage length after

fracture, providing the fracture takes place within the

gage length.

Elongation can also be measured with a break-

away extensometer on the tensile specimen. The

recorded stress strain-curve displays total elongation

(elastic and plastic). The elastic strain at the 0.2% yield

strength must be subtracted from the total elongation to

give the plastic elongation. (See MPIF Standard 59 for

additional details.)

Elastic Constants

Data for the elastic constants in this standard were

generated from resonant frequency testing. An equation

relating the three elastic constants is:

Young’s Modulus (E)

Young’s modulus, expressed in 10

psi (GPa), is

the ratio of normal stress to corresponding strain for

tensile or compressive stresses below the proportional

limit of the material.

Shear Modulus (G)

Shear modulus, expressed in 10

psi (GPa), is the

ratio of shear stress to corresponding shear strain

below the proportional limit of the material.

Poisson’s Ratio (



)

Poisson’s ratio is the absolute value of the ratio of

transverse strain to the corresponding axial strain

resulting from uniformly distributed axial stress below

the proportional limit of the material.

Impact Energy

Impact energy, measured in foot-pounds-force

(Joules), is a measure of the energy absorbed in

fracturing a specimen in a single blow. An unnotched 5

mm X 10 mm cross- section Charpy specimen was used

to establish the MIM impact energy values. (See MPIF

Standard 59 for additional details.)

Macroindentation Hardness (Apparent)

The hardness value of a MIM part when using a

conventional indentation hardness tester is referred

to as "apparent hardness" because it represents a

combination of matrix hardness plus effect of

residual porosity. The effect of residual porosity on

hardness values is minor for MIM parts. Apparent

hardness measures the resistance to indentation.

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