for permanent magnet
and surface coating for the permanent magnet
for manual operation of permanent magnet
Inspection standard for permanent magnet
1) When the permanent magnet is not
supplied with specific size and shape, the properties of material
should be tested. The test standard is as per GB/T3217-95permanent
magnet (hard magnet) material test trial method,GJB2453-95rare
earth permanent magnet material general criterion
and relevant enterprise standard. GB/T3217 stipulated the test
method. Enterprise standard stipulated the test process and sampling
2)When the permanent magnet is supplied
with specific size and shape, the properties of the magnetic component
should be tested. The properties of the material are only tested
3) For different permanent magnetic
components, the test parameters and test methods are different.
For magnetic ring, the test parameter is diametric flux density.
For magnetic segment and block, the parameters can be surface
field, magnetic flux etc. The magnetic flux is better.
A digital tesla meter can test diametric
With a transverse sensor. Magnetic
flux can be tested by permanent magnet tesla meter and Helmholtz
For more information about the international
standard, you may
turn to the following reference:
IEC 404-5(1982) magnetic
material Part 5:test measure for hard magnet(permanent magnet)
2501-1989 Test method for magnetic material(Japan)
4) When the permanent magnet is supplied
as magnetic assembly or component,the properties of the magnetic
assembly or component should be tested. The buyer and seller
will negotiate and decide the specific test method with each other.
5) Unless specified by the user, we
will adopt standard sampling method for the final test of the
1) Permanent magnetic component is not
a standard mechanical component , but a functional
component. It is generally produced as per the customer's demand.
So a certain process period is involved. The lead time is about
2) In order to meet the urgent need,
we keep the following rough semi-finished products in stock. You
may choose among them according to your design requirement to
save the production time.
3)The maximum dimension of the magnet
is 60mm,the maximum dimension in magnetization direction is 200mm;the
minimum dimension of the magnet is 2mm. For small size, the waste
during production is more, so the cost per unit weight is high.
Preferential size of the produc:
4) The products will be tested strictly
as per relevant standard. Unless specified by the user, the discrepancy
of the properties of the product is below 5%.For quality problem
found by the user, please give reasons and return the products
Shipment method: express
air mail, transit time 2~4days,EMS,transit
transportation by train,transit time5~10days normal
mail service Normal
transportation by train. The specific shipment method is decided
by the order quantity and the price.
Permanent magnet supply direction
1) Permanent magnet supplied under two
conditions,Magnetized or no magnetized, is usually not marked
its polarity. If the user require, we could mark the polarity
by the means agreed on. When pacing the order, the user should
inform the supply condition and if the mark of the polarity is
magnetization field of permanent magnet is related to the permanent
magnetic material type and its intrinsic coercive force. If the
magnet need magnetization and demagnetization, please contact
with us and ask for technique support.
There are two methods to magnetize the
magnet: DC field and pulse magnetic field.
There are three methods to demagnetize
the magnet:demagnetization by heat is a special
process technique.demagnetization in AC field. Demagnetization in DC field. This asks
for very strong magnetic field and high demagnetization skill.
shape and magnetization direction of permanent magnet: in principle,
we produce permanent magnet in various shapes. Usually, it includes
block, disc, ring, segment etc. The detailed illustration of the
magnetization direction is below:
for the ring magnets magnetized radially (B),only the isotropic
magnetic ring is available. The anisotropic ones are still in
4) Size and tolerance of the permanent
magnet: Except for the dimension in the direction of magnetization,
the maximum dimension of the permanent magnet is not exceed 60mm,
which is limited by the orientation field and sintering equipment.
The dimension in the magnetization direction is up to 200mm.
Usually the permanent magnet should
be ground. The tolerance after grinding is usually +/-0.05.
Tolerance +/-0.02mm is available too, but the cost will be higher.
suggest the user to refer to our national military standard GJB2453rare
earth permanent magnet general criterion
in the design of the tolerance of the permanent magnet.
Surface protection and surface coating for the permanent magnet
Surface protection: Under the normal atmospheric condition(room
temp. humidity 50%),it
is unnecessary for special surface protection to the permanent
magnet. However, for many applications, the surface protection
is a must. This is for the following reasons:
Anticorruption protection: The rare
earth permanent magnet exposed to acid, alkaline solution,salt,cooling
lubricant or deleterious gas is usually protected by a surface
coating. For NdFeB material, it is easy to erode by high humidity
Protection from magnetic
granules:rare earth permanent magnet is a sintered magnet,so
the magnetic granules on the surface are unavoidable. For some
applications, for example the hard disc machine or sound coil
system, the soft magnetic granules will influence the function,even
damage the magnetism system. The surface protection coating could
protect the permanent magnet from extra accumulation and keep
its surface clean thoroughly.
protection: In a certain system, the permanent magnet is
usually installed by mechanical pressure. Under some conditions,
the pressure install process will cause smashes. The sharp brim
is insecure. So we should consider the coating for every application.
We suggest the user to choose the most appropriate coating for
3) Types of the protection coating:㏕here
are two basis coatings, metal coating and organic coating. To
meet special requirement of the user, we could also adopt metal/metal,metal/organic
double-coating and many other special coatings.
coating: Usually, the metal coating is made by electrical plating
technique. In addition to standard Nickel-plating and Zn-plating,
other coating is also available, if the user require.
coating:The basic organic coating is epoxy. Lacquer spraying is
coating/surface passivation:For the protection in transit or storage
period, this temporary coating is usually used.
1) Quality management of SmCo permanent
magnetic product has been approved by the China electronic
component quality system (i.e. China military standard approval),GB/T9001-ISO9001
quality system, IECQ international electrotechnics committee quality
assessing system, China national Exp. & Imp. Enterprise approving
2) The sintered permanent magnet made
from rare earth alloy is bristle, especially for the SmCo permanent
component, for which the crack slimmer than a hair thread or crack
brim is easy to occur. But this phenomenon won’t influence the
magnetic properties and mechanical characteristics greatly. For
NdFeB permanent magnet, cracks are not very familiar.
3) Under the proper processing technic
condition,the magnetized permanent magnetic component is usually
adhered with little magnetic dust and small chips. To avoid this
phenomenon, we could wipe them off manually and packed the component
individually. To do this, the lead-time will be longer and the
cost will be higher.
4) For the final inspection of permanent
magnet, we usually adopt standard sampling method. Our sampling
inspection is as per the National military standard GJB179A,inspection
Safety principle for manual operation of permanent magnet
1) The magnetized permanent magnets
with strong magnetic field attract the iron and other magnetic
matters around them greatly. Under common condition, the manual
operator should be very careful to avoid any damage. Due to the
strong magnetic force, the big magnet close to them takes the
risk of damage. People always process these magnets separately
or by clamps. In this case, we should ware the protection gloves
2) In this circumstance of
strong magnetic field, any sensible electronic component and test
meter may be altered or damaged. Please see to it that the computer,
display and magnetic media , for example the magnetic disc
,magnetic cassette tape and video record tape etc., are far from
the magnetized components, say farther than 2m.
The collision of the attracting forces
between two permanent magnets will bring enormous sparkles. Therefore,
the flammable or explosive matters should not be placed around
4) When the magnet is exposed to hydrogen,
it is prohibited to use permanent magnets without protection coating.
The reason is that the sorption of hydrogen will destroy the microstructure
of the magnet and lead to the deconstruction of the magnetic properties.
The only way to protect the magnet effectively is to enclose the
magnet in a case and seal it.