Solenoid – a basic actuator for hydraulic system, which is used to control direction, flow and pressure by electromagnetic force. Solenoid is widely used in a range of industries, such as mobile hydraulics, transportations, and hydraulic valves. Due to wide applications of solenoid, there are numerous solenoid classifications: AC and DC solenoid; linear solenoid, Rotary Solenoid, tubular solenoid. In general, solenoid is composed of solenoid coil, armature. What are these parts made of? What are features of solenoid coil and armature? Here is a simple guidance for you.

Solenoid coil

Solenoid coil is a vital component of solenoid, in another word, the quality of solenoid depends on the quality of solenoid coil. Generally, solenoid coil is powered and create electromagnetic field. Coil wire is basically covered with a coat of insulated paint. The common solenoid coil insulation classes include E, F and H.

Material of coil

Solenoid coil produces magnetism through magnetic core. Magnetic core is usually made of Mn-Zn ferrite, Ni-Zn ferrite, Mg-Zn or Alloy.

Mn-Zn Ni-Zn Silicon steel iron power core Fe-Si-Al FeNi
composition Fe2O3:71%

MnO: 20%





Zn: 26%






resistivity 100 Ω·cm 105~108Ω·cm 40~50μΩ·cm 26~125
magnetic conductivity 10~75

There are some typical units for magnetic core, including magnetic induction, magnetic flux, etc.

Features of solenoid coil

  • How to determine the direction of magnetic field? Consider a section of wire as straight line, and judge by Ampere’s rule.
  • When solenoid coil is powered, magnetic field out of solenoid coil center region is combined by magnetic field from every section current. Because magnetic field from every section is different, so the magnetic field out of solenoid coil is weaker than magnetic field in the circle.
  • For circular coil, the larger current is and the smaller radius is, so that the stronger magnetic field of coil center is.
  • Circular coil and disc-shaped thin magnetic have similar magnetic line of force.


Armature also called iron core, it increase the electromagnetic force and help solenoid control the switch, flow and pressure. Armature of solenoid is made of soft iron. Steel can’t be raw material of armature. Once steel be magnetized, it will retain a long-term magnetism and can’t demagnetize, which makes electricity lose control of armature magnetism. In brief, an armature made of steel will lose the due advantages of solenoid. How to choose proper materials for high-quality armature?

As we all know, armature is used to enhance magnetic of solenoid. When you choose the materials for solenoid, just pick the one that has magnetic conductivity larger than1. This kind of material is common, such as manganese, cobalt and such type of metallic oxide. In a word, larger magnetic conductivity armature has, larger of magnetic field of solenoid will has. Compared to iron, other metals have less magnetic conductivity and higher cost, so that they are fairly applied for armature manufacture.

Technically, material of armature pure normally can’t be iron, but fe3o4. Most types of material for armature is iron alloy like manganese zinc ferrites, it is a new material that has about18000 magnetic conductivity.

In conclusion

Both solenoid coil and armature have certain requirements about raw materials. For a solenoid buyer, check the material of solenoid coil and armature will be very important. Kaidi is a solenoid manufacturer with rich experience and projects. We can provide hydraulic solenoid for on-off valve, proportional valve, and explosion-proof valve. Besides, we supply custom solenoid according to clients’ needs. We are also the regular supplier of Rexroth, Yuken, Vickers and Parker. Based on our strict quality control and advanced technology introduce from BSO company, we have export high-quality solenoid to 20+ countries around the world.

As a professional solenoid supplier, we also prepare a series of solenoid buying guide for all beginners and hope it is helpful: how to choose solenoid manufacturer? How to choose a solenoid?