What Is A Sintered Filter? - Powder Metallurgy

Author: Fayella

Dec. 23, 2024

What Is A Sintered Filter? - Powder Metallurgy

Have you ever been to an oceanarium?

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The oxygen foaming device in the oceanarium uses a sintered porous filter.

What is a sintered filter?

A sintered filter is a porous device created by mixing powder and then sintering it. These filters serve multiple functions, including acting as flow restrictors, pneumatic silencers, diffusers, and more. They come in various shapes, including cylindrical, conical, and disc forms.

Let's explore:

  • Types of Sintered Filters
  • Working Principle of Sintered Filters
  • Filtration Ratings
  • Manufacturing Process of Sintered Filters
  • Benefits of Sintered Filters
  • Applications of Sintered Filters

Sintered Metal Filters

Porous metal filter elements are produced by fusing metal powder particles. Here's a look at some common sintered metal filters:

Stainless steel filters are known for their excellent corrosion resistance, high strength, and ability to withstand high temperatures. They can endure harsh environments.

Porous filters are available in materials like 316L, 304L, 310, and 430.

Bronze filters also offer good corrosion resistance and thermal conductivity, making them suitable for use in hydraulic and pneumatic systems.

Sintered Titanium Filters

Sintered titanium filters are favored for their high strength, lightweight nature, and impressive corrosion resistance.

Sintered Nickel Filters

Renowned for their good magnetic properties, nickel filters are available in Inconel grades 600, 625, and 690.

Sintered Plastic Filters

Plastic porous filters are lightweight, corrosion-resistant, and economical. Common raw materials include PE, PP, and UPE.

Sintered Ceramic Filters

Ceramics excel at withstanding high temperatures and maintaining stability, making them ideal for filtering molten metals. They are also very effective in filtering air and water.

Sintered Glass Filters

Sintered glass filters are produced from glass powder, such as borosilicate glass. These filters are easy to clean and do not shed fibers, making them suitable for laboratory and biomedical applications.

The following table illustrates the filtration accuracy and operating temperatures of sintered filters made from various materials:

Material Filtration Ratings (pore size) Operating Temperature
Bronze 5-100μm (20-180μm) Not exceeding 300°C
316 Stainless Steel 0.50-80μm (10-160μm) No more than 600°C
Titanium Alloy 0.50-50μm (10-100μm) No more than 300°C
PP Plastic 0.50-100μm (10-180μm) Less than 80°C

Sintered Filter Working Principle

Gas & Liquid Filtration

Sintered metal filters can effectively remove sediment, metal fragments, algae, and other contaminants from liquids or water. Several filtering mechanisms are involved:

Surface Filtration: Sintered filters possess porous structures where larger particles are trapped on the surface, preventing clogging of the internal pore structure.

Deep Filtration: The inner pores of the filter are tortuous and interconnected. Smaller particles get adsorbed into the internal pore walls during flow.

Diffusion Filtration

Fine particles in gas diffuse onto the internal pore walls while passing through the filter, achieving the desired filtration effect.

Breather Vents

Breather vents enable pressure equalization and prevent the ingress of impurities and moisture. Sintered filters help safeguard the system against contamination while ensuring a long service life.

Protecting Sensors

Porous metal filters protect the covers of electronic components. For instance, they guard speakers against dust, liquids, and sediment intrusion, ensuring sound clarity.

You might be familiar with the filtering capabilities of porous metal filters, but did you know they can also function as pneumatic silencers?

Gas noise is typically generated when pressurized air collides with static air, creating turbulent air that results in noise. Therefore, gas silencers are installed at the valve exhaust ports. They primarily consist of porous materials that disperse the expelled gas over a larger surface area, thereby reducing turbulence and noise levels.

Diffusion Stones

Have you seen a diffuser stone in an aquarium? These devices help diffuse gas into a liquid, also known as oxygen stones. They provide a sufficient oxygen supply for aquatic life.

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Additionally, the applications of sintered filters include:

  • Soda carbonization
  • Beer carbonization
  • Oxygen stripping of cooking oil

Porous metal filters exhibit a porosity of 15%-20% and a filtration precision of 0.5μm, with uniform pores ensuring precise pore control and achieving uniform gas diffusion. This makes them an ideal choice as diffuser stones.

Filtration Ratings

ASTM E128 outlines standard testing for maximum pore size and permeability of porous filters. Sintered metal media grades are categorized by average pore size: 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 40, and 100. Grades between 0.2 and 20 provide liquid filtration ratings ranging from 1.4 to 35 μm absolute, while gas filtration ratings extend from 0.1 to 100 μm.

How Are Sintered Filters Manufactured?

Porous filters require powders with a narrow particle size distribution to ensure uniform pore sizes in the sintered product. Additionally, adding binders can help maintain a consistent powder mixture for easier molding.

Shaping

For filter elements requiring high filtration accuracy, the traditional powder pressing process is usually employed. For larger pore sizes, loose sintering is preferred. This process begins with pouring the mixed powder into a mold typically made of ceramic or graphite. The powder is placed on a vibrating device to increase its density.

Sintering occurs below the metal's melting point, and its purpose is to fuse the particles. Common sintering furnaces include vacuum sintering furnaces, push rod furnaces, and conveyor belt furnaces.

Sintered products may undergo secondary processing as required, including sizing machining, surface treatment, and ultrasonic cleaning.

Benefits of Sintered Filters

  • Good Durability: They possess excellent corrosion and high-temperature resistance.
  • Excellent Filtration Ratings: Filtration accuracy can reach up to 0.5μm.
  • Long Lifespan: Sintered filters have enduring product longevity.
  • Customizable: Pore size and filter shape can be tailored to specific requirements.

Applications of Sintered Filters

Automotive Industries

Sintered filters play a crucial role in filtering car exhaust gases, reducing environmental damage. They are also utilized as mufflers in the car exhaust systems.

Oil and Gas Industry

In the oil and gas sector, sintered filters help remove various contaminants, including sand, rust, and solid particles.

Chemical Industry

With their robust corrosion resistance, sintered filters are excellent for managing corrosive gases and liquids in chemical processing.

Water Treatment

Sintered metal filters provide exceptional filtration, effectively removing impurities and bacteria from water.

Food and Beverage Industry

Sintered metal filters help eliminate oxygen from cooking oil, preventing spoilage and extending shelf life. They are also used to consistently introduce gas into carbonated beverages and beer.

With a uniformly porous structure, sintered filters can generate uniform bubbles, and food-grade stainless steel options like 304 and 316L are available.

After reading this article, you should now have a clearer understanding of what a sintered filter is. If you have any questions or would like to share your views, please leave a comment below.

FAQ

1. What Types of Sintered Filters Can Be Supplied?

We are a leading supplier of sintered filters, offering a variety of porous filters:

  • Sintered stainless steel filters
  • Sintered bronze filters
  • Sintered titanium filters
  • Sintered plastic filters

Our filters are designed for long service life, high filtration efficiency, and excellent corrosion resistance. We also provide custom filters tailored to specific materials, shapes, and sizes.

2. What Factors Should Be Considered When Choosing a Sintered Metal Filter?

  • Filtration ratings
  • Pore size
  • Chemical compatibility
  • Working temperature
  • Flow rate
  • Product quality
  • Maintenance and cleaning

3. How to Clean Sintered Filters?

Common cleaning methods include:

  • Ultrasonic cleaning: Heat the product in a nitrogen-protected furnace at 380 degrees Celsius for two hours, then use an ultrasonic device for about 30 minutes.
  • Chemical flushing: Utilize a chemical cleaner to dissolve contaminants within the product.
  • Pyrolytic burn-off: For filters in high-temperature applications, subject them to elevated temperatures to burn off residues.

4. Why Use the Sintering Process?

The sintering process is crucial for transforming green parts into finished products, yielding structural integrity and improved strength. Compared to forging and casting, sintering eliminates the need for metal melting, resulting in cost efficiency.

5. How Long Is the Production Cycle of Sintered Filters?

The manufacturing of sintered filters typically requires about 15 to 20 days, which includes the time needed to create the molds.

Application of Sintered Filters

We’ve discussed the applications of sintered filters, but why are they preferred over other filter types in various industries? Here are some key reasons:

  • The porosity of sintered filters regulates the flow of liquids or gases effectively, without needing a pressure gauge.
  • Sintered filters are reliable in high-pressure environments, as alternatives like plastic or paper tend to fail under high psi conditions.
  • These filters can endure high-temperature environments; sintered steel mesh can resist heat up to 480°C, and different alloys can further enhance heat resistance, which is unachievable with other filter types.

Metal sintered filters can be welded directly onto filtration unit bodies, eliminating the need for seals and reducing maintenance, thus extending their lifespan.

Sintered filters have diverse applications, and if you seek a proven manufacturer in Europe at competitive prices, reach out to us. We've been making sintered filters since the beginning of Eurobalt Engineering and would gladly assist with your projects. Contact us with your designs and specifications.

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