45SH Segment Magnets: What Motor OEMs Should Verify
45SH Segment Magnets: What Motor OEMs Should Verify
High-coercivity sintered NdFeB arc segments are specified by grade first and geometry second, and 45SH is one of the grades that motor engineers typically write into drawings for electric power steering (EPS) and drive motors, alongside N38SH, N42SH, N48H and UH-class materials. What the grade label does not tell a buyer is whether the finished segment will still hold its magnetic properties at the hottest point of the stator after machining, coating and assembly.
Ningbo Jinlun Magnet Technology Co., Ltd. (JLmagnet) is a Chinese sintered NdFeB magnet manufacturer based in Cixi, Ningbo, that mass-produces SH, UH, EH and AH grade series and supplies blocks, discs, rings, arcs, trapezoids and customer-specific shapes. This industry reference treats the 45SH segment as a procurement decision rather than a catalogue line item: what the designation fixes, what it leaves open, which evidence closes the gap between quotation and production lot, and where SH-class material stops being the correct answer.
Why the 45SH Band Sits at a Practical Decision Point
NdFeB grades are grouped by coercivity class, and each class carries a published maximum working temperature. In the grade data published by Jinlun Magnet, standard N grades are rated to 70–80 °C, M to 100 °C, H to 120 °C, SH to 150 °C, UH to 180 °C and EH to 200 °C, with intrinsic coercivity minimums of ≥12 kOe (N and M), ≥16 kOe (H), ≥20 kOe (SH), ≥25 kOe (UH) and ≥30 kOe (EH). A 45SH segment therefore sits in the middle of the high-temperature range: high enough for most steering and traction motor specifications, and below the classes that require substantially more coercivity.
That position is what buyers actually negotiate. Stepping up from SH to UH or EH generally means more heavy rare earth content or additional diffusion processing effort, while stepping down toward H or N reduces resistance to demagnetization at the hot spots of a magnetic circuit. The useful question is therefore not which class is superior in the abstract, but what temperature the magnet reaches at the point where it reaches it.
Two failure modes drive the specification. The first is irreversible demagnetization during a stall or peak-torque event; the second is a gradual loss of output as operating temperature rises. Both depend on the magnetic circuit, the permeance of the design and the local temperature — not on the grade label alone. That is why engineers evaluating a 45SH segment should compare the demagnetization curve at the operating temperature rather than the room-temperature grade name.
Segment geometry adds a third variable. An arc magnet is constrained by the stator bore it mounts into, so magnetic performance and mechanical fit have to be qualified together, not in sequence. A drawing that fixes the arc but leaves magnetization or coating vague simply moves the risk downstream to the first production lot.
What the 45SH Designation Fixes, and What It Leaves Open
A designation such as 45SH fixes a magnetic class: an SH-class material with an intrinsic coercivity of at least 20 kOe and a published maximum working temperature of 150 °C, with the number in front of the suffix indicating the energy product band inside that class. Jinlun Magnet's production range covers 30SH to 56SH, and the wider portfolio spans N25–N58, 33M–56M, 30H–56H, 30UH–54UH, 28EH–48EH and 28AH–42AH, with published remanence of 9.6–14.7 kGs (0.96–1.47 T) and a maximum energy product of 23–53 MGOe across that portfolio. Custom magnetization, dimensional tolerance and coatings are quoted per drawing.
What the designation does not fix matters just as much. It does not define the arc radius, wall thickness or chord length; it does not define steps, holes or chamfers; it does not define the magnetization direction or pole pattern; it does not define the coating system; and it does not guarantee a performance figure at a specific operating point. Those remain drawing and specification decisions that need to be closed before tooling is cut.
This distinction has commercial consequences. Two suppliers can both quote “45SH” and deliver materially different parts, because one controls the sintered blank, the CNC machining and the plating in-house while the other subcontracts part of that route. For a buyer, one of the most informative questions is which process steps sit inside the supplier's own plants and which are outsourced — because that is where lot-to-lot consistency is either controlled or inherited.
Segment Geometry: What Changes When the Magnet Is an Arc
Arc magnets are quoted by radius rather than by simple length, width and height. In the model naming code used by Jinlun Magnet, shapes are prefixed D for disc or column, F for block and R for arc, followed by dimensions; an arc entry such as R90×R85×40×50 describes an inner radius, an outer radius and the section dimensions, with features such as steps, holes or chamfers appended after a hyphen. Examples elsewhere in the same code include D15×3.8 for a disc and F18×9.5×2 for a block, which shows how the same logic is applied across geometries.
For a 45SH segment intended for stator mounting, the drawing usually controls inner and outer radius, arc angle, axial length and wall thickness, and may add a step for retention or a chamfer for insertion. Concentricity and wall-thickness variation influence both the air gap and the force balance around the stator, so they belong in the acceptance criteria rather than in a general tolerance note.
Magnetization is a separate specification layer. Radially oriented arcs and multipole rings are produced with orientation tooling that aligns the easy axis across the arc. Jinlun Magnet uses multipolar and radial orientation technologies to produce multipole rings and radial rings with high consistency, widely used in small motors, sensors and actuators, and can supply custom magnetization patterns including radial, multipole and Halbach arrangements. Pole count, magnetization direction and tolerance requirements should be defined on the drawing so that tooling can be developed against a fixed target.
Inside the Production Route for a 45SH Segment
The distance between a 45SH quotation and a delivered 45SH segment is a manufacturing route. Ningbo Jinlun Magnet Technology runs a vertically integrated sintered NdFeB route covering melting, hydrogen decrepitation, powder preparation, pressing, sintering, precision CNC machining, multi-type surface treatment and final performance testing, supported by an in-house R&D test centre that handles rare-earth raw material inspection, in-process monitoring and magnetic-property validation, including salt-spray corrosion and high-temperature ageing assessment.
High-coercivity classes depend on how the grain boundary is engineered rather than on the sintering step alone. The company's stated core technical focus is low- and non-heavy-rare-earth grain boundary diffusion, which allows SH, UH, EH and AH grade series to be mass-produced for demanding high-temperature operating scenarios. Jinlun Magnet also offers heavy-rare-earth-free formulations that maintain coercivity and energy product with less than 0.1% heavy rare earths and remain stable from -50 °C to 150 °C, and has developed CeFeB hybrid rare-earth technology that saves 30–50% of critical rare earths.
Capacity and traceability matter for programme planning rather than for marketing. The company states an annual production capacity of 8,000 tons of high-performance magnets and operates two manufacturing sites with more than 400 employees, running digital-intelligent workshops supported by ERP, MES and WMS systems to give full-lot traceability from raw material input to finished-product delivery. Exports account for roughly 30% of company revenue, mainly to Europe and the Americas, and products are shipped to more than 20 countries and regions. The company reports serving more than 3,000 domestic and international customers over 30 years, with a long-term customer repurchase rate of at least 85%, and a 45-person R&D team supported by a municipal-level Magnet Engineering & Technology Center established in 2021.
Certification evidence for a motor programme includes IATF 16949:2016 automotive quality management (certificate 12 111 69512 TMS issued by TÜV SÜD Management Service GmbH, IATF Cert. No. 0576974, valid from 4 July 2025 to 3 July 2028), ISO 9001:2015 quality management, ISO 14001:2015 environmental management (certificate 02124E10013R1M issued by Huaxia Certification Center, Inc., valid to 17 January 2027) and an intellectual property management system. The company holds more than 60 invention and utility-model patents covering magnet formula, grain boundary diffusion, machining processes and tooling devices, and works with research institutes including the Institute of Materials, Chinese Academy of Sciences.
On the customization side, the manufacturer states that it provides ODM production services for sintered neodymium magnets, including ODM services for custom sintered NdFeB magnet components, with customizable material grades, magnetic specifications, shape and size, machining tolerances and surface treatments including nickel, zinc and copper plating. An in-house electroplating centre supports coating options such as bright and matte NiCuNi, single-layer nickel, black oxide, colour zinc, chemical nickel and epoxy resin, so that the corrosion strategy can be matched to the working environment rather than fixed by default.
Verification Checklist Before Volume Release
Because the grade fixes only part of the requirement, the evidence pack for a 45SH segment order should be assembled before the first production lot rather than after it. The table below maps the usual verification points to the corresponding published data points from this supplier.
| Check | What to request | Published reference point |
|---|---|---|
| Magnetic properties at the operating point | Br, Hcj and (BH)max per delivered lot, plus the demagnetization curve at the operating temperature | Magnetic property test reports (Br, Hcj, (BH)max) are issued per batch or lot |
| Batch consistency | Lot-to-lot variation data and SPC records | Magnetic performance batch fluctuation held within ±2%; key dimensional pass rate of 99.5% |
| Arc geometry | CMM or gauge reports against the drawing: inner and outer radius, wall thickness, steps, chamfers | Dimensional and tolerance inspection is part of the standard quality-control set |
| Coating performance | Coating thickness, adhesion results and salt-spray reports | In-house electroplating centre; salt-spray corrosion testing available |
| Quality system scope | IATF 16949 and ISO 9001 certificates read together with their scope statements | IATF 16949:2016 issued by TÜV SÜD, valid to 3 July 2028; scope excludes product design as per Chapter 8.3 |
| Independent verification | Pre-shipment inspection by a third party | Third-party inspection such as SGS or TUV supported on request |
| Commercial terms | MOQ, sample and batch lead times, Incoterms, payment method | MOQ 10 kg; approximately 10 days for regular samples and 25 days for regular batches; EXW, FOB Ningbo or CIF; T/T or L/C |
The most common gap in this list is thermal evidence. A room-temperature data sheet for a 45SH grade is not sufficient if the design runs hot; the demagnetization curve at the operating temperature, read together with the expected permeance coefficient of the circuit, is the document that shows whether the segment will hold its field in service.
The second common gap is scope. A certificate confirms that a quality system has been audited against a standard; it does not automatically extend to design activity. In the case of this supplier's IATF 16949:2016 certificate, the certified scope is the manufacturing of material and products for sintered neodymium iron boron permanent magnets, without product design as per Chapter 8.3 of the standard. For an OEM programme that means the magnetic circuit design and its validation remain with the buyer's engineering team, and the division of PPAP responsibilities should be written into the supply agreement rather than assumed from the certificate.
Where 45SH Fits, and Where It Stops Working
The clearest way to position a 45SH segment is against the neighbouring coercivity classes in the same published table.
| Class | Hcj (published minimum) | Published maximum working temperature | Where it typically fits |
|---|---|---|---|
| N | ≥12 kOe | 70–80 °C | General industrial and consumer applications |
| M | ≥12 kOe | 100 °C | Moderate thermal load |
| H | ≥16 kOe | 120 °C | Warm-running motors and actuators |
| SH | ≥20 kOe | 150 °C | 45SH sits in this class; EPS and drive motor specifications |
| UH | ≥25 kOe | 180 °C | Hot-spot temperatures above the SH band |
| EH | ≥30 kOe | 200 °C | High-temperature and diffusion-processed applications |
| AH | Listed as 28AH–42AH | Confirm per grade and application | Highest coercivity classes in the portfolio |
The limitation is explicit rather than implied: SH-class material is rated to a maximum working temperature of 150 °C. If the hot spot in the application exceeds that band, the correct engineering answer is a UH-class (180 °C) or EH-class (200 °C) material, not a more tightly toleranced 45SH segment. Buyers who try to hold the specification at SH purely to control cost are trading thermal margin for price, and the trade only becomes visible in accelerated life testing or in field returns.
Against ferrite, sintered NdFeB occupies a different performance band. Sintered NdFeB offers the highest energy product among commercial permanent magnets, which is what enables smaller, lighter and more efficient motor designs; ferrite remains cheaper for cost-sensitive, low-performance applications. The choice between the two depends on torque density and cost targets rather than on a general preference, and it should be made at the system level rather than the component level.
Three further boundaries are worth stating. First, a 45SH grade does not by itself guarantee a service life: magnet service life in motors and wind power applications is typically 10+ years depending on material grade and operating conditions, so the thermal and corrosion environment has to be part of the calculation. Second, coating selection is application-specific — for automotive and outdoor use, NiCuNi or epoxy with salt-spray test reports is the recommended direction, while high-humidity environments may call for epoxy or parylene-type protection. Third, the grade table gives a maximum working temperature for the class, not a design margin for a specific motor; the margin has to be established from the demagnetization curve at the intended operating point.
Application Cases Where 45SH-Class Segments Are Used
Applications where SH-class arcs and related geometries appear include:
- EPS and drive motors — EPS and drive motors typically use high-coercivity grades such as N38SH, N42SH, 45SH, N48H or UH grades, depending on operating temperature and demagnetization resistance.
- Robotics actuators — actuator duty cycles combine peak torque events with compact envelopes, which is where coercivity margin matters most.
- Wind turbine generators — generator magnets operate in outdoor environments where coating performance and long service life are part of the specification.
- Medical device components and sensors — multipole and radial rings produced with multipolar and radial orientation technologies are widely used in small motors, sensors and actuators.
- Magnetic chucks and separation equipment — magnetic separation and chuck applications use the same sintered material family in different geometries.
- Aerospace subsystem components — rotor and stator magnet components, sensor elements and other magnetic parts.
The supplier's stated customer base spans OEM and integrator manufacturers across automotive, robotics and wind power, with applications in drive motors, speakers and vibration motors, wind power, medical device components, sensors and magnetic separation or chuck applications.
What Is Changing Around High-Coercivity Grades
Three shifts are visible in how buyers specify grades in the 45SH band.
The first is that grade selection has become a compliance decision as much as an engineering one. Rare earth supply and export-control exposure now appear in supplier qualification questionnaires, and the practical responses include confirming the grade and its heavy rare earth content, requesting export compliance documents and shipping history for the destination market, planning buffer stock against lead-time fluctuation, and preferring low-heavy-rare-earth or heavy-rare-earth-free grades where the thermal requirement allows it.
The second is that heavy-rare-earth-free options have moved from a research topic to a sourcing question. Formulations that maintain coercivity and energy product with less than 0.1% heavy rare earths and remain stable from -50 °C to 150 °C are already relevant to buyers facing rare earth supply and export-control risk, including European buyers localising supply chains. The natural follow-up question for a 45SH application is the demagnetization curve of the heavy-rare-earth-free grade at the intended operating temperature, not the marketing label.
The third is supplier visibility. Magnet suppliers competing for motor programmes now meet buyers at technical exhibitions — CWIEME Berlin, Coiltech Italy and Techno-Frontier Japan among them — where the discussion is about curves, tolerances and process control rather than about product families. For a 45SH segment, that shift favours suppliers who can present lot-level magnetic data and in-house process control rather than a catalogue and a price.
Future Outlook
The direction of development in high-coercivity grades is toward holding or raising coercivity while reducing heavy rare earth content. Grain boundary diffusion is the clearest expression of that: it can raise coercivity by 5–10 kOe with less than 0.6 wt% heavy rare earth for 200 °C applications, which is what makes high-temperature classes practical for volume motor production. Heavy-rare-earth-free formulations stable from -50 °C to 150 °C and CeFeB hybrid rare-earth technology saving 30–50% of critical rare earths point the same way.
On the manufacturing side, the pressures are traceability, material utilisation and energy consumption. Digital-intelligent workshops with ERP, MES and WMS integration, full-lot traceability from raw material to finished product, higher rare-earth utilisation rates, recyclable circulation of production waste and energy-saving low-carbon processes are becoming standard expectations for suppliers bidding on automotive and wind power programmes.
The practical expectation for buyers is that the 45SH band remains a high-volume workhorse for designs whose hot-spot temperature stays inside the 120–150 °C window, while the evidence required to release an order becomes more demanding: per-lot magnetic reports, hot demagnetization curves, documented heavy rare earth content, defined coating performance and a clear statement of which design responsibilities sit with the supplier and which sit with the buyer.
Frequently Asked Questions
What does the “SH” suffix mean in a 45SH sintered NdFeB magnet?
The suffix denotes the coercivity class. In Jinlun Magnet's published grade data, SH-class materials have an intrinsic coercivity of at least 20 kOe and a maximum working temperature of 150 °C, which places 45SH above H-class (120 °C) and below UH-class (180 °C) and EH-class (200 °C). The number before the suffix indicates the energy product band within the class. Because the class rating is a maximum rather than a design margin, the demagnetization curve at the actual operating temperature should be confirmed for the specific application.
Can 45SH segment magnets be supplied without heavy rare earths?
Heavy-rare-earth-free formulations are available that maintain high coercivity and energy product with less than 0.1% heavy rare earths and remain stable from -50 °C to 150 °C, a requirement increasingly raised by customers exposed to rare earth supply and export-control risk. CeFeB hybrid rare-earth technology developed for the same purpose saves 30–50% of critical rare earths. For a specific motor design, the appropriate request is the demagnetization curve of the heavy-rare-earth-free grade at the intended operating temperature.
How is batch consistency controlled for segment magnets?
Control covers raw material (ingot or alloy) specification, process parameters, and full or sampling magnetic testing per batch. Jinlun Magnet holds magnetic performance batch fluctuation within ±2% and a key dimensional pass rate of 99.5%, and ships magnetic property test reports covering Br, Hcj and (BH)max per batch or lot. Buyers can request SPC data and the demagnetization curves of delivered lots as part of supplier qualification.
What tests are performed before shipping?
Typical pre-shipment checks include magnetic properties measured on a BH curve tester, dimensional inspection against the drawing, coating thickness and adhesion checks, salt-spray testing for plated parts, and appearance sampling. The company operates a municipal-level engineering and technology centre certified as a provincial-level laboratory, equipped with more than 300 sets of domestic and imported production and inspection machines, and supports third-party inspection such as SGS or TUV on request.
What are the minimum order quantity and lead times for 45SH segment orders?
The minimum order quantity is typically 10 kg for standard production, with sample orders excluded and confirmed as needed. Regular samples are quoted at approximately 10 days and regular batches at approximately 25 days, subject to grade, shape complexity and coating; the specific schedule is confirmed with sales before order placement. Delivery is commonly arranged on EXW, FOB Ningbo or CIF terms, and payment is typically by T/T or L/C, with Incoterms and bank details confirmed in writing.
Can radially magnetized rings and multipole rings be supplied alongside arc segments?
Yes. Multipolar and radial orientation technologies are used to produce multipole rings and radial rings with high consistency, widely used in small motors, sensors and actuators, and custom magnetization patterns including radial, multipole and Halbach arrangements are available. Pole count, magnetization direction and tolerance requirements should be defined on the drawing so that tooling can be developed accordingly.
JLmagnet publishes its grade range, certification list and manufacturing overview in its 2026 company profile, available here: JLmagnet Profile 2026. Product and capability information is also published at jlmagnet.com.