MP 20x8/4x3 / N38 - ring magnet
ring magnet
Catalog no 030187
GTIN/EAN: 5906301812043
Diameter
20 mm [±0,1 mm]
internal diameter Ø
8/4 mm [±0,1 mm]
Height
3 mm [±0,1 mm]
Weight
6.79 g
Magnetization Direction
↑ axial
Load capacity
3.14 kg / 30.79 N
Magnetic Induction
178.11 mT / 1781 Gs
Coating
[NiCuNi] Nickel
3.59 ZŁ with VAT / pcs + price for transport
2.92 ZŁ net + 23% VAT / pcs
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Product card - MP 20x8/4x3 / N38 - ring magnet
Specification / characteristics - MP 20x8/4x3 / N38 - ring magnet
| properties | values |
|---|---|
| Cat. no. | 030187 |
| GTIN/EAN | 5906301812043 |
| Production/Distribution | Dhit sp. z o.o. |
| Country of origin | Poland / China / Germany |
| Customs code | 85059029 |
| Diameter | 20 mm [±0,1 mm] |
| internal diameter Ø | 8/4 mm [±0,1 mm] |
| Height | 3 mm [±0,1 mm] |
| Weight | 6.79 g |
| Magnetization Direction | ↑ axial |
| Load capacity ~ ? | 3.14 kg / 30.79 N |
| Magnetic Induction ~ ? | 178.11 mT / 1781 Gs |
| Coating | [NiCuNi] Nickel |
| Manufacturing Tolerance | ±0.1 mm |
Magnetic properties of material N38
| properties | values | units |
|---|---|---|
| remenance Br [min. - max.] ? | 12.2-12.6 | kGs |
| remenance Br [min. - max.] ? | 1220-1260 | mT |
| coercivity bHc ? | 10.8-11.5 | kOe |
| coercivity bHc ? | 860-915 | kA/m |
| actual internal force iHc | ≥ 12 | kOe |
| actual internal force iHc | ≥ 955 | kA/m |
| energy density [min. - max.] ? | 36-38 | BH max MGOe |
| energy density [min. - max.] ? | 287-303 | BH max KJ/m |
| max. temperature ? | ≤ 80 | °C |
Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C
| properties | values | units |
|---|---|---|
| Vickers hardness | ≥550 | Hv |
| Density | ≥7.4 | g/cm3 |
| Curie Temperature TC | 312 - 380 | °C |
| Curie Temperature TF | 593 - 716 | °F |
| Specific resistance | 150 | μΩ⋅cm |
| Bending strength | 250 | MPa |
| Compressive strength | 1000~1100 | MPa |
| Thermal expansion parallel (∥) to orientation (M) | (3-4) x 10-6 | °C-1 |
| Thermal expansion perpendicular (⊥) to orientation (M) | -(1-3) x 10-6 | °C-1 |
| Young's modulus | 1.7 x 104 | kg/mm² |
Engineering simulation of the magnet - report
Presented information represent the outcome of a mathematical analysis. Values were calculated on algorithms for the material Nd2Fe14B. Operational performance might slightly differ from theoretical values. Use these data as a supplementary guide for designers.
Table 1: Static force (force vs gap) - power drop
MP 20x8/4x3 / N38
| Distance (mm) | Induction (Gauss) / mT | Pull Force (kg/lbs/g/N) | Risk Status |
|---|---|---|---|
| 0 mm |
1531 Gs
153.1 mT
|
3.14 kg / 6.92 LBS
3140.0 g / 30.8 N
|
strong |
| 1 mm |
1457 Gs
145.7 mT
|
2.84 kg / 6.27 LBS
2843.2 g / 27.9 N
|
strong |
| 2 mm |
1352 Gs
135.2 mT
|
2.45 kg / 5.39 LBS
2446.6 g / 24.0 N
|
strong |
| 3 mm |
1227 Gs
122.7 mT
|
2.02 kg / 4.44 LBS
2016.2 g / 19.8 N
|
strong |
| 5 mm |
963 Gs
96.3 mT
|
1.24 kg / 2.74 LBS
1241.9 g / 12.2 N
|
weak grip |
| 10 mm |
465 Gs
46.5 mT
|
0.29 kg / 0.64 LBS
289.3 g / 2.8 N
|
weak grip |
| 15 mm |
228 Gs
22.8 mT
|
0.07 kg / 0.15 LBS
69.7 g / 0.7 N
|
weak grip |
| 20 mm |
122 Gs
12.2 mT
|
0.02 kg / 0.04 LBS
20.0 g / 0.2 N
|
weak grip |
| 30 mm |
45 Gs
4.5 mT
|
0.00 kg / 0.01 LBS
2.7 g / 0.0 N
|
weak grip |
| 50 mm |
11 Gs
1.1 mT
|
0.00 kg / 0.00 LBS
0.2 g / 0.0 N
|
weak grip |
Table 2: Sliding capacity (vertical surface)
MP 20x8/4x3 / N38
| Distance (mm) | Friction coefficient | Pull Force (kg/lbs/g/N) |
|---|---|---|
| 0 mm | Stal (~0.2) |
0.63 kg / 1.38 LBS
628.0 g / 6.2 N
|
| 1 mm | Stal (~0.2) |
0.57 kg / 1.25 LBS
568.0 g / 5.6 N
|
| 2 mm | Stal (~0.2) |
0.49 kg / 1.08 LBS
490.0 g / 4.8 N
|
| 3 mm | Stal (~0.2) |
0.40 kg / 0.89 LBS
404.0 g / 4.0 N
|
| 5 mm | Stal (~0.2) |
0.25 kg / 0.55 LBS
248.0 g / 2.4 N
|
| 10 mm | Stal (~0.2) |
0.06 kg / 0.13 LBS
58.0 g / 0.6 N
|
| 15 mm | Stal (~0.2) |
0.01 kg / 0.03 LBS
14.0 g / 0.1 N
|
| 20 mm | Stal (~0.2) |
0.00 kg / 0.01 LBS
4.0 g / 0.0 N
|
| 30 mm | Stal (~0.2) |
0.00 kg / 0.00 LBS
0.0 g / 0.0 N
|
| 50 mm | Stal (~0.2) |
0.00 kg / 0.00 LBS
0.0 g / 0.0 N
|
Table 3: Vertical assembly (shearing) - behavior on slippery surfaces
MP 20x8/4x3 / N38
| Surface type | Friction coefficient / % Mocy | Max load (kg/lbs/g/N) |
|---|---|---|
| Raw steel |
µ = 0.3
30% Nominalnej Siły
|
0.94 kg / 2.08 LBS
942.0 g / 9.2 N
|
| Painted steel (standard) |
µ = 0.2
20% Nominalnej Siły
|
0.63 kg / 1.38 LBS
628.0 g / 6.2 N
|
| Oily/slippery steel |
µ = 0.1
10% Nominalnej Siły
|
0.31 kg / 0.69 LBS
314.0 g / 3.1 N
|
| Magnet with anti-slip rubber |
µ = 0.5
50% Nominalnej Siły
|
1.57 kg / 3.46 LBS
1570.0 g / 15.4 N
|
Table 4: Steel thickness (saturation) - power losses
MP 20x8/4x3 / N38
| Steel thickness (mm) | % power | Real pull force (kg/lbs/g/N) |
|---|---|---|
| 0.5 mm |
|
0.31 kg / 0.69 LBS
314.0 g / 3.1 N
|
| 1 mm |
|
0.79 kg / 1.73 LBS
785.0 g / 7.7 N
|
| 2 mm |
|
1.57 kg / 3.46 LBS
1570.0 g / 15.4 N
|
| 3 mm |
|
2.36 kg / 5.19 LBS
2355.0 g / 23.1 N
|
| 5 mm |
|
3.14 kg / 6.92 LBS
3140.0 g / 30.8 N
|
| 10 mm |
|
3.14 kg / 6.92 LBS
3140.0 g / 30.8 N
|
| 11 mm |
|
3.14 kg / 6.92 LBS
3140.0 g / 30.8 N
|
| 12 mm |
|
3.14 kg / 6.92 LBS
3140.0 g / 30.8 N
|
Table 5: Thermal stability (stability) - thermal limit
MP 20x8/4x3 / N38
| Ambient temp. (°C) | Power loss | Remaining pull (kg/lbs/g/N) | Status |
|---|---|---|---|
| 20 °C | 0.0% |
3.14 kg / 6.92 LBS
3140.0 g / 30.8 N
|
OK |
| 40 °C | -2.2% |
3.07 kg / 6.77 LBS
3070.9 g / 30.1 N
|
OK |
| 60 °C | -4.4% |
3.00 kg / 6.62 LBS
3001.8 g / 29.4 N
|
|
| 80 °C | -6.6% |
2.93 kg / 6.47 LBS
2932.8 g / 28.8 N
|
|
| 100 °C | -28.8% |
2.24 kg / 4.93 LBS
2235.7 g / 21.9 N
|
Table 6: Magnet-Magnet interaction (repulsion) - forces in the system
MP 20x8/4x3 / N38
| Gap (mm) | Attraction (kg/lbs) (N-S) | Lateral Force (kg/lbs/g/N) | Repulsion (kg/lbs) (N-N) |
|---|---|---|---|
| 0 mm |
3.71 kg / 8.17 LBS
2 815 Gs
|
0.56 kg / 1.23 LBS
556 g / 5.5 N
|
N/A |
| 1 mm |
3.55 kg / 7.83 LBS
2 998 Gs
|
0.53 kg / 1.17 LBS
533 g / 5.2 N
|
3.20 kg / 7.05 LBS
~0 Gs
|
| 2 mm |
3.36 kg / 7.40 LBS
2 915 Gs
|
0.50 kg / 1.11 LBS
503 g / 4.9 N
|
3.02 kg / 6.66 LBS
~0 Gs
|
| 3 mm |
3.13 kg / 6.90 LBS
2 815 Gs
|
0.47 kg / 1.04 LBS
470 g / 4.6 N
|
2.82 kg / 6.21 LBS
~0 Gs
|
| 5 mm |
2.63 kg / 5.81 LBS
2 582 Gs
|
0.40 kg / 0.87 LBS
395 g / 3.9 N
|
2.37 kg / 5.23 LBS
~0 Gs
|
| 10 mm |
1.47 kg / 3.23 LBS
1 926 Gs
|
0.22 kg / 0.48 LBS
220 g / 2.2 N
|
1.32 kg / 2.91 LBS
~0 Gs
|
| 20 mm |
0.34 kg / 0.75 LBS
930 Gs
|
0.05 kg / 0.11 LBS
51 g / 0.5 N
|
0.31 kg / 0.68 LBS
~0 Gs
|
| 50 mm |
0.01 kg / 0.02 LBS
143 Gs
|
0.00 kg / 0.00 LBS
1 g / 0.0 N
|
0.00 kg / 0.00 LBS
~0 Gs
|
| 60 mm |
0.00 kg / 0.01 LBS
90 Gs
|
0.00 kg / 0.00 LBS
0 g / 0.0 N
|
0.00 kg / 0.00 LBS
~0 Gs
|
| 70 mm |
0.00 kg / 0.00 LBS
59 Gs
|
0.00 kg / 0.00 LBS
0 g / 0.0 N
|
0.00 kg / 0.00 LBS
~0 Gs
|
| 80 mm |
0.00 kg / 0.00 LBS
41 Gs
|
0.00 kg / 0.00 LBS
0 g / 0.0 N
|
0.00 kg / 0.00 LBS
~0 Gs
|
| 90 mm |
0.00 kg / 0.00 LBS
30 Gs
|
0.00 kg / 0.00 LBS
0 g / 0.0 N
|
0.00 kg / 0.00 LBS
~0 Gs
|
| 100 mm |
0.00 kg / 0.00 LBS
22 Gs
|
0.00 kg / 0.00 LBS
0 g / 0.0 N
|
0.00 kg / 0.00 LBS
~0 Gs
|
Table 7: Safety (HSE) (implants) - precautionary measures
MP 20x8/4x3 / N38
| Object / Device | Limit (Gauss) / mT | Safe distance |
|---|---|---|
| Pacemaker | 5 Gs (0.5 mT) | 7.0 cm |
| Hearing aid | 10 Gs (1.0 mT) | 5.5 cm |
| Timepiece | 20 Gs (2.0 mT) | 4.5 cm |
| Phone / Smartphone | 40 Gs (4.0 mT) | 3.5 cm |
| Car key | 50 Gs (5.0 mT) | 3.0 cm |
| Payment card | 400 Gs (40.0 mT) | 1.5 cm |
| HDD hard drive | 600 Gs (60.0 mT) | 1.0 cm |
Table 8: Collisions (kinetic energy) - collision effects
MP 20x8/4x3 / N38
| Start from (mm) | Speed (km/h) | Energy (J) | Predicted outcome |
|---|---|---|---|
| 10 mm |
22.90 km/h
(6.36 m/s)
|
0.14 J | |
| 30 mm |
37.58 km/h
(10.44 m/s)
|
0.37 J | |
| 50 mm |
48.50 km/h
(13.47 m/s)
|
0.62 J | |
| 100 mm |
68.58 km/h
(19.05 m/s)
|
1.23 J |
Table 9: Corrosion resistance
MP 20x8/4x3 / N38
| Technical parameter | Value / Description |
|---|---|
| Coating type | [NiCuNi] Nickel |
| Layer structure | Nickel - Copper - Nickel |
| Layer thickness | 10-20 µm |
| Salt spray test (SST) ? | 24 h |
| Recommended environment | Indoors only (dry) |
Table 10: Electrical data (Pc)
MP 20x8/4x3 / N38
| Parameter | Value | SI Unit / Description |
|---|---|---|
| Magnetic Flux | 5 044 Mx | 50.4 µWb |
| Pc Coefficient | 0.20 | Low (Flat) |
Table 11: Submerged application
MP 20x8/4x3 / N38
| Environment | Effective steel pull | Effect |
|---|---|---|
| Air (land) | 3.14 kg | Standard |
| Water (riverbed) |
3.60 kg
(+0.46 kg buoyancy gain)
|
+14.5% |
1. Wall mount (shear)
*Warning: On a vertical wall, the magnet retains only a fraction of its perpendicular strength.
2. Steel thickness impact
*Thin metal sheet (e.g. 0.5mm PC case) drastically reduces the holding force.
3. Thermal stability
*For standard magnets, the max working temp is 80°C.
4. Demagnetization curve and operating point (B-H)
chart generated for the permeance coefficient Pc (Permeance Coefficient) = 0.20
This simulation demonstrates the magnetic stability of the selected magnet under specific geometric conditions. The solid red line represents the demagnetization curve (material potential), while the dashed blue line is the load line based on the magnet's geometry. The Pc (Permeance Coefficient), also known as the load line slope, is a dimensionless value that describes the relationship between the magnet's shape and its magnetic stability. The intersection of these two lines (the black dot) is the operating point — it determines the actual magnetic flux density generated by the magnet in this specific configuration. A higher Pc value means the magnet is more 'slender' (tall relative to its area), resulting in a higher operating point and better resistance to irreversible demagnetization caused by external fields or temperature. A value of 0.42 is relatively low (typical for flat magnets), meaning the operating point is closer to the 'knee' of the curve — caution is advised when operating at temperatures near the maximum limit to avoid strength loss.
Material specification
| iron (Fe) | 64% – 68% |
| neodymium (Nd) | 29% – 32% |
| boron (B) | 1.1% – 1.2% |
| dysprosium (Dy) | 0.5% – 2.0% |
| coating (Ni-Cu-Ni) | < 0.05% |
Environmental data
| recyclability (EoL) | 100% |
| recycled raw materials | ~10% (pre-cons) |
| carbon footprint | low / zredukowany |
| waste code (EWC) | 16 02 16 |
See also offers
Strengths as well as weaknesses of neodymium magnets.
Strengths
- They have constant strength, and over nearly 10 years their attraction force decreases symbolically – ~1% (in testing),
- Magnets perfectly protect themselves against loss of magnetization caused by foreign field sources,
- Thanks to the metallic finish, the plating of Ni-Cu-Ni, gold, or silver gives an modern appearance,
- They are known for high magnetic induction at the operating surface, which increases their power,
- Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
- Possibility of detailed forming and adapting to defined requirements,
- Significant place in innovative solutions – they are commonly used in magnetic memories, motor assemblies, advanced medical instruments, also industrial machines.
- Compactness – despite small sizes they provide effective action, making them ideal for precision applications
Cons
- Brittleness is one of their disadvantages. Upon strong impact they can break. We advise keeping them in a steel housing, which not only secures them against impacts but also raises their durability
- We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
- Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material stable to moisture, when using outdoors
- We recommend casing - magnetic mount, due to difficulties in producing nuts inside the magnet and complicated forms.
- Health risk to health – tiny shards of magnets are risky, when accidentally swallowed, which is particularly important in the context of child safety. Additionally, tiny parts of these products can disrupt the diagnostic process medical after entering the body.
- Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications
Pull force analysis
Maximum magnetic pulling force – what contributes to it?
- on a plate made of mild steel, optimally conducting the magnetic field
- whose thickness is min. 10 mm
- with an ground contact surface
- without any clearance between the magnet and steel
- during detachment in a direction vertical to the mounting surface
- at standard ambient temperature
Magnet lifting force in use – key factors
- Space between surfaces – even a fraction of a millimeter of separation (caused e.g. by veneer or unevenness) significantly weakens the magnet efficiency, often by half at just 0.5 mm.
- Pull-off angle – note that the magnet holds strongest perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the nominal value.
- Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal limits the attraction force (the magnet "punches through" it).
- Metal type – different alloys attracts identically. High carbon content worsen the interaction with the magnet.
- Surface quality – the more even the plate, the better the adhesion and higher the lifting capacity. Roughness acts like micro-gaps.
- Thermal conditions – NdFeB sinters have a sensitivity to temperature. At higher temperatures they lose power, and at low temperatures gain strength (up to a certain limit).
Lifting capacity testing was conducted on plates with a smooth surface of suitable thickness, under perpendicular forces, however under shearing force the holding force is lower. Moreover, even a slight gap between the magnet’s surface and the plate decreases the load capacity.
H&S for magnets
Magnetic media
Avoid bringing magnets near a purse, computer, or TV. The magnetism can irreversibly ruin these devices and erase data from cards.
Danger to pacemakers
Medical warning: Strong magnets can deactivate pacemakers and defibrillators. Do not approach if you have medical devices.
Dust explosion hazard
Dust produced during machining of magnets is flammable. Do not drill into magnets unless you are an expert.
Maximum temperature
Monitor thermal conditions. Exposing the magnet to high heat will destroy its magnetic structure and pulling force.
Safe operation
Handle with care. Neodymium magnets attract from a long distance and connect with massive power, often faster than you can move away.
Beware of splinters
Neodymium magnets are sintered ceramics, meaning they are prone to chipping. Clashing of two magnets leads to them cracking into small pieces.
Precision electronics
Be aware: rare earth magnets generate a field that confuses precision electronics. Keep a safe distance from your phone, device, and GPS.
Allergic reactions
Medical facts indicate that the nickel plating (standard magnet coating) is a potent allergen. If your skin reacts to metals, avoid direct skin contact and opt for versions in plastic housing.
Crushing force
Protect your hands. Two powerful magnets will join instantly with a force of massive weight, crushing anything in their path. Exercise extreme caution!
This is not a toy
Only for adults. Small elements can be swallowed, leading to serious injuries. Keep out of reach of children and animals.
