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/T3217-95 (permanent magnet
(hard magnet) material test trial method),GJB2453-95 (rare
earth permanent magnet material general criterion) and relevant
enterprise standard. GB/T3217 stipulated the test method.
Enterprise standard stipulated the test process and sampling
method.
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
for reference.
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 flux density With a transverse sensor.
Magnetic flux can be tested by permanent magnet tesla meter
and Helmholtz coil.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) material properties.JISC 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 permanent magnet.
Purchasing Guide
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 10-15 days.
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 to us.
5) Shipment method:  express
air mail, transit time 2~4days, EMS,transit
time3~7days. express
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 necessary.
2)The 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.
3) geometry 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:
As for the ring magnets magnetized radially (B),only the
isotropic magnetic ring is available. The anisotropic ones
are still in research.
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 We suggest the
user to refer to our national military standard GJB2453 rare
earth permanent magnet general criterion
in the design of the tolerance of the permanent magnet.
Surface protection and surface coating for the permanent
magnet
1) 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 or dew.
2)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.
Operation 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 their application.
3)Types of the protection coating:©There 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. Metal 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. Organic coating:The
basic organic coating is epoxy. Lacquer spraying is also adoptable.Temporary
anti-corruption coating/surface passivation:For the protection
in transit or storage period, this temporary coating is usually
used.
Quality warranty
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 committee.
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 level
class,AQL1.5.
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 in operation.
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 2mThe collision of the attracting forces
between two permanent magnets will bring enormous sparkles.
Therefore, the flammable or explosive matters should not be
placed around them
3)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.
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