How are Sintered NdFeb magnets made and how to choose them?

What is the production process of Sintered NdFeb magnets?

Sintered NdFeb magnets are the strongest magnets in today's commercial market, also known as strong magnets, with high remanence, high coercivity, high magnetic energy product, cost-effective and other characteristics, and can be processed into various shapes and sizes. So how are sintered Ndfeb magnets produced? What is the process of sintering Ndfeb?

Sintered NdFeb Magnet

The sintered Ndfeb process can be divided into the following nine steps:

1.Ingredients: NdFeb permanent magnet Its main raw materials are rare earth metal neodymium 29%-32.5%, metallic element iron 63.95-68.65%, non-metallic element boron 1.1-1.2%, a small amount of added dysprosium 0.6-1.2%, niobium 0.3-0.5%, aluminum 0.3-0.5%, copper 0.05-0.15% and other elements.

2.Smelting: Mainly cast flakes or ingots according to the proportion of good raw materials, which are completed by large furnaces and small furnaces respectively.

3.Hydrogen crushing: Using the hydrogen absorption characteristics of rare earth metal compounds, the Ndfeb alloy is placed in a hydrogen environment, and hydrogen will enter the alloy along the neodymium-rich thin layer, causing it to expand and damage, so that the sheet becomes coarse powder.

4.Air mill: The principle is similar to a blender, high pressure air blows up the coarse powder, and the powder collides with each other in the air stream to become a fine powder.

5.Molding: The subdivision is pressed in the mold to make the desired shape.

6.Isostatic pressure: The working principle is PASCAL fixed force, and the pressure is gradually released to the object to gradually reduce the density of the product to meet the predetermined requirements.

7.Stripping oil: To remove the static pressure of the product packaging to prepare for sintering.

8.Sintering: Put the product into a specific sintering furnace for a series of sintering, small steps can be divided into furnace, sintering, baking, sintering basin leveling, furnace temperature calibration, demagnetization, reverse firing and other processes. The final product can be obtained.

9.Machining: Blank materials according to customer demand: grinding machine, wire cutting, slicing, drilling, electroplating, magnetization, testing, packaging, delivery, specific needs to be decided according to customer products.

Ndfeb magnet blank production tools and performance testing tools: Melting furnace, strip furnace, jaw breaking machine, air grinding, pressing machine, vacuum sealing machine, isostatic press, sintering furnace, heat treatment vacuum furnace, magnetic tester, Gauss meter. 

Ndfeb magnet machining tools: Centerless grinding, circular machine, double-end grinding, flat grinding, slicer, double-side grinding, wire cutting, bench drill, profiled grinding and so on. 

The above is the process flow of sintered Ndfeb magnets.

How to evaluate the quality of neodymium magnets?

We all know that NdFeB has different properties and can be suitable for different environments and scenarios. So, how to make sure that the magnet we buy is exactly what we need?

1.Size tolerance measurement testing

This is the most basic one test, to make sure the tolerance meet your requirement. 

2.Gauss measuring

NdFeB usually order for industrial use, the magnetism is very important, after testing the gauss with gaussmeter, we can know the rough grade, to check if the magnet is the standard grade.

3.Pull force testing

This is a testing some clients need do, for the environment they use is related to the pull force.

4.B-H curve testing

B-H curve is a point can check if the magnet is standard magnet, according to this result, we can know the Br, Hci, Hcb,BH(max).

5.Salt spray test

Salt Spray Test is an environmental test that mainly uses artificial simulated salt spray environmental conditions created by salt spray testing equipment to assess the corrosion resistance of products or metal materials. The testing time has 24 hours, 48 hours and 72 hours.

6.Aging test

Before the test, need saturate the magnet and record the surface magnetism and magnetic flux. Then, attach the product to the iron plate and put it into the aging test box. Bake it at a certain temperature for a corresponding time, and then wait for cooling. Test the magnetic flux to check if the magnetic loss is within the acceptable range.

Except the test we list, also can do the PCT(material), PCT(coating), HAST. 

Customized Shape Neodymium Magnet

However, not all tests must be done. It depends on what environment the magnet is suitable for and what requirements it needs to meet. Corresponding tests must be done depending on the situation.