Powder Metallurgy Stainless Steel
The primary method of processing Powder Metallurgy for stainless steel is:
The processing of stainless steel powder metallurgy primarily uses this powder as the raw material, which is then sintered and refined using a forming technique. Powder mixing, pressing, Sintering, finishing, and post-processing are the primary steps in the powder metallurgy processing of stainless steel. Numerous other activities fall under the category of post-processing, including machining, packing, and oil impregnation.
In this process flow, the prepared stainless steel powder is first mixed to create a high-purity mixed powder. The powder is then loaded into a mold and pressed into shape under specific pressure. The pressed green sheet is then placed in a controlled atmosphere sintering furnace and sintered at a temperature below the melting point of the matrix material, causing the powder particles to undergo high-temperature treatment and form a metallurgical bond.
Let's introduce the process of stainless steel powder metallurgy processing in steps.
- Mixing
Mix the stainless steel powder with the additives and stir them according to the time requirements to form a high-purity mixed powder.
- Forming
According to the size, structure, shape and design mold drawings of the product, press it to make a carbide mold, then install the machine to test the mold, and test the sample. The mold design and production cycle is one week.
- Degreasing
The temperature of degreasing is controlled at 800 degrees, and the vacuum bell furnace or mesh belt furnace is used for degreasing. The purpose is to remove the added lubricant.
- Sintering
In the processing of stainless steel powder metallurgy, sintering is the key process. The final physical and mechanical properties required by the formed compact are obtained by sintering. Sintering is divided into unit system sintering and multi-component system sintering. In actual production, for the solid phase sintering of unit system and multi-component system, the sintering temperature is lower than the melting point of the metal and alloy used.
- Subsequent treatment
The subsequent treatment after sintering can be completed in different ways according to the different requirements of the product. For example, finishing, oiling, machining, heat treatment and electroplating are commonly used in actual production. In addition, in recent years, some new processes have been produced, such as rolling and forging. These processes can also be applied to the processing of powder metallurgy materials after sintering to obtain more ideal processing effects.
Methods for improving the strength and hardness of powder metallurgy stainless steel
First, stainless steel powder is formed into a body, and then the body is placed in a reducing environment and maintained at a sintering temperature to form a sintered body. Then, the sintered body is exposed to a carbon-containing atmosphere and maintained at a carburizing temperature below 600°C, so that carbon can form a carburized area on the surface and inside of the sintered body. In this way, the hardness and strength of the powder metallurgy stainless steel can be improved through the carburized area, and because the heating temperature is below 600°C, the reaction between chromium and carbon can be prevented, so that good corrosion resistance can also be maintained.
Key Stainless Steel Grades in Powder Metallurgy
- Austenitic Stainless Steels:
- SS-303:
- Properties: High strength and hardness, good corrosion resistance, non-magnetic.
- Applications: Preferred for parts requiring extensive secondary machining.
- SS-304:
- Properties: Good strength and corrosion resistance; general-purpose grade.
- Applications: Widely used across various industries due to its versatility.
- SS-316:
- Properties: Superior corrosion resistance compared to SS-303; non-magnetic.
- Applications: First choice for general-purpose applications, especially in corrosive environments.
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17-4 PH
- Properties: High strength, excellent corrosion resistance, and the ability to harden through heat treatment (precipitation hardening).
- Applications: Aerospace components, medical devices, and high-performance mechanical parts requiring strength and resistance to fatigue.
- SS-303:
- Ferritic Stainless Steels:
- SS-430:
- Properties: Magnetic with high chromium content; lower carbon content enhances corrosion resistance.
- Applications: Ideal for automotive and kitchenware applications.
- SS-430:
- Martensitic Stainless Steels:
- SS-410 and SS-420:
- Properties: Magnetic, high strength, but lower corrosion resistance compared to austenitic grades.
- Applications: Often used in cutlery and other applications requiring hardness.
- SS-410 and SS-420:
- Duplex Stainless Steels:
- These combine austenitic and ferritic structures, providing high strength and improved resistance to stress corrosion cracking.