재료 및 공학 가이드
What metals are magnetic?
Iron, nickel, and cobalt are the best-known metals that are strongly attracted to magnets. Many iron-based alloys, including carbon steel and several stainless steel families, also show a clear magnetic response.
However, the metal name alone is not enough. Alloy structure, processing condition, part thickness, contact surface, and the test setup can all change what you observe.
Aluminum and copper do not normally stick to an ordinary permanent magnet. They still respond to magnetic fields scientifically, but the response is too weak to feel in a normal hand-held test.
What Metals Are Magnetic? Quick Reference Table
The following magnetic metals list describes the typical response to an ordinary hand-held magnet. It is suitable for preliminary screening, not material certification.
| Metal or material family | Does it normally stick to an ordinary magnet? | Important qualification |
|---|---|---|
| Iron | Yes, strongly | One of the main ferromagnetic elements |
| Carbon and mild steel | Usually yes | Response varies with composition, structure, thickness, and condition |
| 니켈 | 예 | Pure nickel is ferromagnetic at ordinary temperatures |
| 코발트 | 예 | Pure cobalt is ferromagnetic at ordinary temperatures |
| Ferritic stainless steel | Usually yes | Commonly gives a clear hand-held magnet response |
| Martensitic stainless steel | Usually yes | Normally ferromagnetic |
| Duplex stainless steel | Usually yes | Contains ferritic and austenitic phases |
| Austenitic stainless steel | Often weak or negligible | Cold work and material condition can increase its response |
| Aluminum | No noticeable ordinary attraction | Paramagnetic, but the response is very weak |
| Copper | No noticeable ordinary attraction | Diamagnetic and does not normally stick |
On smaller screens, swipe the table horizontally to see every column.
This table does not identify exact grades. Supplier documentation, material certificates, chemical analysis, or another suitable identification method is still required when grade confirmation matters.
What Does “Magnetic” Actually Mean?
In everyday language, a metal is called magnetic when it sticks to a refrigerator magnet or workshop magnet. In physics, the word covers several different types of material response.
| Term | Meaning | What you normally observe |
|---|---|---|
| Ferromagnetic | Responds strongly to an applied magnetic field and contains magnetic domains | Clear attraction to a hand-held magnet |
| Paramagnetic | Responds weakly in the direction of an applied field | Usually no noticeable hand-held attraction |
| Diamagnetic | Develops a very weak response opposite to the applied field | Usually no noticeable everyday effect |
| 영구 자석 | Retains useful magnetization and produces an external magnetic field | Can attract suitable ferromagnetic materials |
On smaller screens, swipe the table horizontally to see every column.
OpenStax University Physics classifies materials by their ferromagnetic, paramagnetic, and diamagnetic responses. It lists aluminum as paramagnetic and copper as diamagnetic, while explaining why these weak responses are very different from ferromagnetic attraction.
For engineering work, define the requirement clearly. A project may need:
- A target part that can be attracted by a magnet.
- A material that can be magnetized.
- A permanent magnet that produces a useful field.
- A complete magnetic circuit that provides a required force at a working distance.
These are related requirements, but they are not interchangeable.
Why Do Iron, Nickel, Cobalt, and Many Steels Attract Magnets?
Ferromagnetic materials contain magnetic domains that can respond strongly to an outside magnetic field. This is why an unmagnetized steel part can still be pulled toward a permanent magnet.
Iron, nickel, and cobalt are the most familiar ferromagnetic metals in ordinary engineering discussions. Many iron-based alloys are also ferromagnetic, but alloy chemistry and microstructure still matter.
It is therefore unsafe to assume that every alloy containing iron, nickel, or cobalt will behave the same way. The finished material condition must be considered.
Are All Steels and Stainless Steels Magnetic?
No. Many steels are attracted to magnets, but not every steel or stainless steel grade produces the same response.
Carbon and mild steels usually respond clearly. Stainless steel is more complicated because its magnetic behavior depends mainly on its metallurgical structure and processing condition.
그리고 British Stainless Steel Association explains that ferritic, martensitic, duplex, and most precipitation-hardening stainless steels normally show a strong response to a hand-held magnet. Austenitic stainless steels usually show little response when fully annealed.
Cold work can increase the magnetic response of some austenitic stainless steels. Composition and heat-treatment condition also matter. See the BSSA guidance on the effect of cold work and heat treatment.
This leads to two practical rules:
- A stainless steel part sticking to a magnet does not prove its exact grade.
- A weak response does not automatically prove that the part is 304 or 316 stainless steel.
Welded or heavily machined areas should be evaluated according to their actual composition and processing history rather than a general rule.
Which Metals Do Not Normally Stick to a Magnet?
Aluminum and copper do not normally show noticeable attraction in a static hand-held magnet test.
Aluminum is paramagnetic, which means it responds weakly in the direction of an applied field. Copper is diamagnetic, which means its weak induced response opposes the applied field. Neither effect normally produces useful holding force with an ordinary permanent magnet.
Aluminum can interact with changing magnetic fields through other physical effects. That is different from ordinary static attraction and belongs in a dedicated discussion of aluminum and magnets.
A plated or painted part may also give a misleading result. A thin outer layer may hide steel, a steel insert, or another ferromagnetic component underneath.
Can You Identify a Metal with a Magnet Test?
A magnet test is useful for quick screening, but it cannot identify an exact alloy.
Use the same small test magnet, similar contact conditions, and known reference samples when comparing parts. Dirt, coatings, curvature, thickness, and hidden inserts can change the result.
| Test result | What it may indicate | What it does not prove |
|---|---|---|
| Strong attraction | A ferromagnetic material or hidden ferromagnetic component may be present | Exact alloy or grade |
| Weak attraction | Austenitic stainless steel affected by processing, a thin ferromagnetic section, or another mixed structure | A specific stainless grade |
| No noticeable attraction | The part may be aluminum, copper, annealed austenitic stainless steel, or another weak-response material | Exact composition |
| Different responses across one part | Mixed materials, inserts, weld areas, coatings, or different processing conditions may be present | The cause without further inspection |
On smaller screens, swipe the table horizontally to see every column.
What Should a Magnet Test Be Used For?
| Use a magnet test for | Do not use it for |
|---|---|
| Preliminary material screening | Exact alloy certification |
| Finding obvious ferromagnetic parts | Confirming 304 versus 316 |
| Detecting a possible hidden steel insert | Approving safety-critical material |
| Comparing samples under consistent conditions | Predicting final assembly holding force |
Use the test as a screening step, not as acceptance evidence for a production specification.
Why Can Magnetic Attraction Change in a Real Assembly?
Knowing that a target metal is ferromagnetic does not tell you how much force a finished assembly will provide.
For buyers, the practical question is:
Can this target material, at its actual thickness and working gap, provide enough usable force in the final assembly?
| Assembly factor | Why it matters | Information to provide |
|---|---|---|
| Target material and condition | Different steels and structures respond differently | Grade, family, certificate, or sample |
| Target thickness | Thin steel may limit the usable magnetic circuit | Actual thickness and available target area |
| 업무 공백 | Air, paint, adhesive, plastic, and coatings separate the magnet from the target | Total nonmagnetic gap |
| Surface flatness | Curved, rough, rusty, or uneven surfaces reduce effective contact | Surface drawing or sample |
| Magnet geometry | Diameter, length, thickness, and pole area affect field distribution | 사용 가능한 설치 공간 |
| 자화 방향 | The pole orientation must match the working face | Required working face and assembly orientation |
| Steel backing or housing | A properly designed ferromagnetic structure may redirect flux | Housing material, dimensions, and layout |
| Load direction | Direct pull, sliding, and edge peel create different demands | Load direction and mounting position |
| 작동 조건 | Temperature, vibration, impact, and corrosion can affect suitability | Actual service environment |
| Acceptance method | Supplier pull-force values may use different test conditions | Required test setup and pass criteria |
On smaller screens, swipe the table horizontally to see every column.
A coating, air gap, or uneven surface can reduce usable pull force. Thin target steel may also limit performance, but the effect depends on magnet geometry, target material, and the complete magnetic circuit.
Specialist test guidance shows that steel thickness and contact conditions can materially change pull force. It also warns that calculated or catalog values should not replace application testing. See the K&J Magnetics steel-thickness guidance.
A properly designed ferromagnetic backing or housing can direct more magnetic flux toward a working face. This is not automatic; the geometry and material must form a suitable magnetic circuit.
A magnet that performs well in direct pull may behave differently under sliding or edge-peel loading. Sliding resistance also depends on friction, surface condition, and mechanical restraint.
What Should You Provide for a Magnetic Holding or Separation Project?
Provide the following information before selecting a magnet or magnetic assembly:
- Target material family and grade, if known.
- Material condition or processing history.
- Target thickness and available contact area.
- Coatings, paint, adhesive, plastic, or other working gaps.
- Surface shape, flatness, roughness, and corrosion condition.
- Available space for the magnet and housing.
- Required working distance.
- Required force and load direction.
- Whether the load is direct pull, sliding, peel, lifting, or separation.
- Operating temperature and environmental exposure.
- Vibration, impact, movement, or repeated-cycle requirements.
- Drawing, sample, sketch, or assembly layout.
- Required validation method and acceptance conditions.
For magnetic separation, also provide the material flow, contamination type, expected particle size, working distance, and cleaning method. A magnetic drum separator or another magnetic structure must be evaluated against the real process rather than selected only by magnet grade.
When Is a Custom Magnet or Magnetic Assembly Review Needed?
A simple hand-held test may be enough for basic material screening. It is not enough when the project has a defined holding force, limited space, a working gap, thin target steel, unusual load direction, or a complex steel housing.
OSENC can review drawings, samples, sketches, and application requirements for 맞춤형 네오디뮴 자석 and magnetic assemblies. The review may consider magnet geometry, grade, magnetization direction, coating, target material, working gap, and magnetic-circuit structure.
A higher magnet grade is not automatically the correct solution. Geometry, target material, available pole area, temperature, assembly design, cost, and validation requirements must be considered together.
Projects can also begin with suitable neodymium magnet samples or prototypes before moving to batch production. Actual force must be validated under agreed test conditions.
자주 묻는 질문
가장 흔한 자성 금속 세 가지는 무엇인가요?
철, 니켈, 코발트는 일반적인 공학 분야에서 가장 잘 알려진 세 가지 강자성 금속입니다. 이 원소들을 주성분으로 하는 많은 합금도 자성을 띨 수 있지만, 그 반응은 조성 및 구조에 따라 달라집니다.
강철은 자성을 띠나요?
대부분의 탄소강과 연강은 자석에 분명히 끌립니다. 그러나 스테인리스강의 반응은 종류와 가공 조건에 따라 다릅니다.
스테인리스강은 자성을 띠나요?
일부 스테인리스강은 자성을 띠는 반면, 다른 일부는 자성을 거의 나타내지 않습니다. 페라이트계, 마르텐사이트계, 듀플렉스계 스테인리스강은 일반적으로 자성을 띠는 반면, 완전히 어닐링된 오스테나이트계 스테인리스강은 자성을 약하게 나타내는 경우가 많습니다.
알루미늄은 자성을 띠나요?
알루미늄은 상자성 물질이지만, 일반적으로는 일반 영구자석에 달라붙지 않습니다. 알루미늄의 자기 반응은 너무 미약하여 표준 정적 시험에서는 감지할 수 없습니다.
구리는 자성을 띠나요?
구리는 반자성체이므로 일반적으로 자석에 달라붙지 않습니다. 눈에 띄게 자석에 끌리는 현상이 나타난다면, 부품 내에 강철 삽입물, 이물질, 도금층 또는 다른 재질이 포함되어 있을 수 있습니다.
자석으로 금속의 등급을 확인할 수 있나요?
아닙니다. 이 장비는 물질의 전반적인 자성 반응에 따라 물질을 분류할 수는 있지만, 정확한 합금 종류나 스테인리스강 등급을 확실하게 확인할 수는 없습니다.
인력이 더 강하다는 것은 그 금속에 철이 더 많이 포함되어 있다는 뜻인가요?
꼭 그렇지는 않습니다. 자력은 미세구조, 조성, 대상 물체의 두께, 가공 조건, 자석의 형상 및 시험 설정에 따라 달라집니다.
자성을 띤 금속이라면 강력한 고정력을 보장할 수 있을까요?
No. The target material is only one part of the magnetic circuit. Working gap, target thickness, surface condition, magnet geometry, housing, and load direction all affect usable force.
Discuss Your Magnetic Application with OSENC
Selecting a magnetic target material is only the first step. The final design must work with the actual target thickness, gap, surface, load direction, available space, and operating conditions.
OSENC can review your drawing, sample, or application requirements before sample validation. The goal is to match the magnet and magnetic circuit to the real application rather than selecting a magnet only by grade.
Contact OSENC with the target material, drawing, working distance, required force, load direction, and operating environment.
Request an Engineering Review
벤 — OSENC
벤은 영구자석 업계에서 10년 이상의 경력을 쌓았으며, 2019년부터 OSENC에서 근무해 왔습니다. 그는 맞춤형 NdFeB 자석, 자석 부속품 및 자석 어셈블리를 주로 담당하고 있습니다.
그는 고객이 소재, 코팅, 자화, 시험 및 생산 요건을 명확히 파악할 수 있도록 지원함으로써, 의사소통의 오류를 줄이고 불필요한 샘플 수정 과정을 최소화합니다.


