Sintered plunger and production method therefor
View Patent ↗A sintered plunger is used for electromagnetic actuators. The sintered member includes: an outer member composed of a soft magnetic material and having an inner hole formed therein, and a shaft having an end portion which is fitted into the outer member. The shaft is composed of a ferromagnetic steel, the outer member peripheral is composed of a sintered member, and the shaft and the outer member are integrally bonded by sintering. As a result, the overall sintered plunger can have good magnetic properties, a good magnetic attraction, a good wear resistance, and a good fatigue strength. Electromagnetic actuators having high responsiveness required in recent years can be produced.
1. A sintered plunger used for electromagnetic actuators, comprising:
an outer member composed of a soft magnetic material and having an inner hole formed therein; and
a shaft having an end portion which is fitted into the outer member,
wherein the shaft is composed of a ferromagnetic steel, the outer member is composed of a sintered member, and the shaft and the outer member are integrally bonded by sintering them.
2. A sintered plunger according to claim 1 ,
wherein the ferromagnetic steel has a magnetic flux density of 0.3 T or more in a magnetic field of 10 KA/m, and has a hardness of Hv 600 or more.
3. A sintered plunger according to claim 2 , wherein the ferromagnetic steel is selected from a group consisting of a tool steel, a bearing steel, and a martensitic stainless steel.
4. A sintered plunger according to claim 3 , wherein the tool steel is a high speed steel.
5. A sintered plunger according to claim 3 , wherein the sintered plunger comprising:
a diffusion bonding layer which is formed between the shaft and the outer member; and
a ferrite phase formed in the diffusion layer proximate to the shaft, and having width of 500 μm or less.
6. A sintered plunger according to claim 1 , wherein the soft magnetic material is selected from a group consisting of a ferrite, an Fe—P-based alloy, an Fe—Si-based alloy, an Fe—Si—P-based alloy, a permalloy, a permemdur, and an electromagnetic stainless material.
7. A sintered plunger according to claim 6 , wherein the soft magnetic material has a porosity of 15% or less.
8. A production method for a sintered plunger used for electromagnetic actuators,
the sintered plunger comprising:
an outer member composed of a soft magnetic material and having an inner hole formed therein; and
a shaft having an end portion fitted in the outer member,
the production method comprising:
preparing a raw powder having a soft magnetic property;
compacting the raw powder into a green compact having an inner hole;
fitting the shaft into the inner hole of the green compact, the shaft composed of a ferromagnetic steel;
integrally diffusion bonding the shaft and the green compact during sintering at a temperature of from 1000 degrees C. to 1300 degrees C., in a nonoxidizing atmosphere which is other than a carburizing atmosphere; and
quenching and tempering the shaft and the compact which are integrally bonded, so that the sintered plunger is obtained.
9. A production method for a sintered plunger according to claim 8 , wherein fitting of the green compact and the shaft is clearance fit having a clearance therebetween of 50 μm or less which is fit size difference or is interference fit having an interference of 20 μm or less.