Material Standards for Metal Injection Molded Parts

When developing technical specifications for MIM materials, the MIM Association adopts the same brand system as AISI-SAE. The reason for choosing these brand names is because MIM parts are often used to replace products of corresponding forged and rolled materials that are already in use. When indicating that a certain material is manufactured using the MIM process, "MIM" should be added before the material. For example, 316L stainless steel manufactured using the MIM process can be represented by "MIM-316L".

Before selecting a specific material, it is necessary to carefully analyze the design of the part and its ultimate use, including dimensional tolerances, part design, and mold design. In addition, the manufacturer and buyer of MIM parts must agree on the final performance requirements for the finished parts, such as static and dynamic loads, wear resistance, cutting resistance, and corrosion resistance can also be specified.

MIM Some Concept

The Metal Powder Industry Federation has adopted the concept of minimum mechanical property value for powder metallurgy materials used in structural components. When using the MIM process to manufacture parts, these values can be used as a basis for users to choose specific application materials. To assist users in selecting materials, in addition to the minimum mechanical property values, standard values for other properties are also listed. Thus, users can choose and determine suitable MIM materials and the most suitable performance for specific applications. The provided data specifies the minimum mechanical property values of the material and lists the standard mechanical property values that can be achieved under industrial production conditions. Through more complex technological processes, mechanical properties can be enhanced and other performance improvements can be made. To choose the best material that is feasible in terms of both performance and price, it is most important for users to discuss the use of the part with the MIM component manufacturer.

The minimum value of MIM materials is represented by yield strength (0.2% offset method), ultimate tensile strength, and elongation for all materials in the sintered and/or heat treated states. Because the density of MIM materials is close to the true density, their performance is similar to that of forged and rolled materials.

HEAT TREATMENT

Except for austenitic stainless steel, MIM materials can undergo heat treatment to increase strength, hardness, and wear resistance. MIM iron based parts with a combined carbon content of 0.3% or higher can be quenched, hardened, and tempered. The percentage content of carbon, alloy elements, and residual pores determines the degree of hardenability under any given quenching condition. By using quenching, the hardness can be increased to 55HRc (650HK) or higher. In order to achieve optimal strength and wear resistance, tempering or stress relief is required after quenching, and the tempering temperature is an important factor in determining the final hardness. When the MIM iron based parts manufactured are ultimately free of carbon or have low carbon content, surface carburization quenching can be carried out to improve surface hardness and maintain the toughness of the core. Martensitic and precipitation hardened stainless steel can also be heat treated to improve hardness and strength.

MIM Material Technical Standards

(1) Low alloy steel

This includes MIM materials made by mixing pre alloy powder and iron powder with other alloy element (such as Ni, Al, and C) powders. To achieve various performance, the proportion of each element added and the heat treatment conditions may vary. Alloys can achieve high strength and appropriate toughness through quenching. In order to achieve surface wear resistance and toughness at the core, alloys with low carbon content can undergo surface carburization quenching.

The material characteristics are generally characterized by sufficient diffusion of alloy elements during sintering. Uniformly organized individuals have excellent strength performance. High density can be obtained using MIM technology, so these materials also have good toughness.

Low alloy steel is generally used for lightweight structural parts, especially after carburizing quenching treatment. They can be used in situations where high strength and hardness are required.

The residual pores in the microstructure should be small, evenly distributed, and relatively rounded. The microstructure of the sintered body should contain varying amounts of ferrite and eutectoid depending on the carbon content.

The nominal chemical composition is shown in Table, and the properties of low alloy steel MIM materials and the physical mechanical properties of MIM low alloy steel are shown

STAINLESS STEEL INTRODUCTION AND PROPERTIES

Stainless steel includes MIM materials made of pre alloyed or elemental powder prepared stainless steel, including grades of austenitic stainless steel, duplex stainless steel, and precipitation hardened stainless steel.

The material properties are improved by the use of MIM technology to obtain high density, thereby improving the strength, toughness, and corrosion resistance of these materials. There are several grades of MIM stainless steel used, each with special properties and a wide range of applications.

1. MIM-316L austenitic stainless steel: This grade is used in situations where excellent corrosion resistance is required

The parts made of materials have good comprehensive strength and toughness.

2. MIM duplex (316L) stainless steel: The so-called duplex refers to this type of stainless steel with ferrite austenite

Composite tissue. Compared with 316L, it has similar corrosion resistance, but higher apparent hardness and more or less improved mechanical properties. These alloys are all ferromagnetic.

2. MIM-17-4PH precipitation hardened stainless steel: In situations where high strength and hardness are required, this type of stainless steel can be used

Grade of stainless steel. Due to its low carbon content, its corrosion resistance is generally better than that of 400 series stainless steel. By changing the aging temperature during heat treatment, various properties and hardness can be obtained.