Is 17 4 Stainless Steel Magnetic Properties Uses Guide

Think all stainless steel is non-magnetic? That’s where many engineers and buyers get tripped up—especially with 17-4 stainless steel.

Here’s the bottom line: 17-4 stainless steel is magnetic in every heat treatment condition. Whether you’re working with 17-4 PH, Type 630, or simply “17-4,” a magnet will stick to it because of its martensitic structure.

And that matters. If you’re designing for magnetic chucks, sensors, food processing lines, or environments that must stay non-magnetic (like around MRI equipment), choosing the wrong grade can cost you time, money, and safety.

In this guide, you’ll quickly learn:

Why 17-4 stainless steel is magnetic (even though it contains nickel)
How heat treatment (H900, H1025, H1150) affects its magnetic properties
How 17-4 compares to non-magnetic grades like 304 and 316
When its magnetism is an advantage—and when you should avoid it

If you need high-strength, magnetic stainless with reliable quality and traceability, vastmaterial supplies premium 17-4 stainless steel in bars, plates, and custom parts tailored to demanding applications.

Let’s get straight into how 17-4 behaves—and whether it’s the right choice for your next project.

What Is 17-4 Stainless Steel?

17-4 stainless steel (also known as 17-4 PH, Type 630, or UNS S17400) is a high-strength, corrosion-resistant stainless steel that I rely on when I need both toughness and dimensional stability in demanding environments. It’s widely used in the U.S. for parts that must handle high loads, moderate corrosion, and tight tolerances.

Basic Definition of 17-4 PH Stainless Steel

17-4 PH is a precipitation-hardening martensitic stainless steel.
“17-4” refers roughly to its chromium and nickel content (about 17% Cr and 4% Ni). Through heat treatment, it develops very high strength while still offering good corrosion resistance—stronger than most common 300-series stainless steels.

Chemical Composition and Key Alloying Elements

Typical composition (weight %):

Chromium (Cr): ~15–17% – corrosion resistance and hardness
Nickel (Ni): ~3–5% – strength and toughness
Copper (Cu): ~3–5% – key for precipitation hardening
Niobium/Columbium (Nb+Ta): ~0.15–0.45% – strengthens the martensitic structure
Carbon (C): ≤0.07% – controls hardness and toughness
Balance Iron (Fe) with small amounts of Mn, Si, P, S

This chemistry is exactly what drives its magnetic behavior and high mechanical performance.

Martensitic Precipitation-Hardening Grade (Type 630)

17-4 PH is a martensitic precipitation-hardening stainless steel:

Martensitic = hard, magnetic, high strength
Precipitation hardening = uses aging heat treatments to form fine copper-rich precipitates that boost strength and hardness

Under the AISI designation, it’s called Type 630, and it sits between standard martensitic (like 410) and austenitic (like 304) stainless steels in terms of corrosion resistance but far exceeds them in strength.

Core Mechanical Properties: Strength, Hardness, Toughness

Depending on heat treatment (H900, H1025, H1150, etc.), 17-4 stainless steel delivers:

Ultimate tensile strength: up to ~190–200 ksi (H900)
Yield strength: often 2–3× stronger than 304/316
Hardness: up to ~HRC 40–45 in high-strength conditions
Good toughness in many conditions, especially at H1150 and similar tempers

This combination—high strength, solid hardness, and practical toughness—is why 17-4 PH is a go-to material in critical US industrial applications.

Common Product Forms and Industrial Uses

I typically source and supply 17-4 stainless steel in:

Round bar, hex bar, and shafting
Plate and sheet
Forgings and flanges
Castings and near-net shapes

Typical U.S. applications include:

Aerospace: structural fittings, actuators, landing gear parts
Oil & gas: pump shafts, valves, downhole tools
Marine: high-strength hardware, propulsion components
Food and beverage: process equipment where strength + cleanability matter
General industrial: high-load shafts, gears, fixtures, and high-strength fasteners

Whenever you need a high-strength, corrosion-resistant, magnetic stainless steel, 17-4 PH stainless is one of the most efficient and widely available options in the market.

Is 17-4 Stainless Steel Magnetic?

Yes, 17-4 stainless steel is magnetic. It’s a martensitic precipitation-hardening (PH) stainless steel, so it behaves like other magnetic stainless grades and will clearly attract a magnet in normal shop conditions.

Why 17-4 PH Is a Magnetic Stainless Grade

17-4 (also known as 17-4 PH, Type 630, or UNS S17400) has a martensitic structure, which is naturally ferromagnetic. Unlike austenitic grades like 304 and 316, 17-4 doesn’t rely on high nickel content to stay non-magnetic. Instead, its chemistry and heat treatment are designed for high strength and hardness, which also lock in that magnetic behavior.

How Strongly a Magnet Sticks to 17-4

In real-world use:

A basic shop magnet will grab 17-4 firmly—stronger than it does on 304 or 316.
On aged conditions (like H900 or H1025), the pull feels solid and positive, good enough for magnetic chucks, clamps, and fixtures.
Compared with low-carbon or austenitic stainless from a typical stainless steel product range, 17-4 will feel noticeably more magnetic.

Quick Magnet Test You Can Do

If you want to confirm whether your part is 17-4 stainless steel magnetic:

Use a small rare-earth (neodymium) magnet or a strong fridge magnet.
Touch it to a clean, flat area of the part.
Strong snap-on and hard to slide off = likely 17-4 or another martensitic/PH stainless.
Very weak or no pull = more likely 304, 316, or another austenitic, non-magnetic grade.

This simple stainless steel magnet test is often enough for a quick check before you commit to using 17-4 in magnetic workholding, fixtures, or separation setups.

Magnetic properties of 17-4 stainless steel

Ferromagnetic behavior of 17-4 PH

17-4 stainless steel is clearly ferromagnetic. In practice, that means:

A standard shop magnet grabs it strongly
It behaves much closer to a 400-series martensitic stainless than to 304/316 in terms of magnet pull
It’s fully usable with magnetic chucks, clamps, and holders

For anyone in machining, casting, or fabrication, you can treat 17-4 as a magnetic stainless steel bar/plate grade.

Why 17-4 stainless steel is magnetic (martensite + crystal structure)

17-4 PH is a martensitic precipitation-hardening stainless steel, and that martensitic structure is what makes it magnetic.

In the hardened/aged condition, the microstructure is mainly martensite
Martensite has a BCC/BCT-type lattice (body-centered cubic / body-centered tetragonal)
These crystal structures allow the material to align magnetic domains easily, which creates strong ferromagnetism

By contrast, austenitic grades like 304 or 316 have an FCC structure (face-centered cubic) that is much more non-magnetic in the annealed state, as explained in many side-by-side alloy steel vs stainless steel comparisons like this stainless-focused guide.

Magnetic permeability and attraction strength

In real-world use, the magnetic permeability of 17-4 stainless steel is:

High enough for strong magnetic attraction
Stable across typical shop temperatures
Suitable for most magnetic workholding and magnetic separation setups

You’ll usually notice:

Stronger pull than on 304/316
Similar or slightly lower pull than some straight 400-series stainless (like 410/420) depending on heat treatment

Bar vs plate vs machined parts

Magnetism in 17-4 PH is strong in all common product forms, but you may notice small differences:

Form	Typical Magnetic Behavior
Hot-rolled / forged bar	Strong, consistent attraction
Plate / sheet	Strong; edge effects can slightly change feel
Precision machined parts	Still strongly magnetic; geometry affects pull
Thin sections / small parts	Feel “weaker” mainly due to small contact area

Key point: the base material is magnetic in all these forms. Any change you feel is usually due to part thickness, surface finish, or contact area, not a change in the alloy itself.

If you’re combining 17-4 with other steels or casting alloys in one assembly, it’s worth understanding how each material behaves magnetically and mechanically, similar to how you’d compare different alloys in a stainless steel casting process overview.

Why 17-4 PH Is Magnetic but Some Stainless Steels Are Not

When people ask, “Is 17-4 stainless steel magnetic?”, what they’re really bumping into is how different stainless steel families behave around a magnet.

Stainless steel families and magnetism

Most stainless steels fall into four main groups, and their magnetism follows their microstructure:

Austenitic (300 series like 304, 316)
- Structure: FCC austenite
- Typically non-magnetic or very weakly magnetic
- Used where low or no magnetism is important
Ferritic (430, etc.)
- Structure: BCC ferrite
- Strongly magnetic
- Lower nickel, lower cost, moderate corrosion resistance
Martensitic (410, 420, 440C)
- Structure: BCT martensite
- Strongly magnetic
- High hardness and wear resistance, moderate corrosion resistance
Precipitation hardening (PH) like 17-4 (Type 630, UNS S17400)
- Martensitic PH stainless
- Magnetic, similar to other martensitic grades
- Combines high strength, good corrosion resistance, and clear magnetic response

Nickel’s role in non-magnetic stainless steel

Nickel is the big lever here:

High nickel (like 8–12% in 304/316) stabilizes austenite, which is non-magnetic.
17-4 PH has much lower nickel (about 3–5%), not nearly enough to hold an austenitic, non-magnetic structure.
With less nickel, the steel transforms to martensite when cooled, and martensite is ferromagnetic.

In other words, high nickel = more austenite = low magnetism.
Lower nickel = martensite/ferrite = strong magnetism.

How 17-4’s chemistry promotes martensite

17-4 PH is designed to be:

High in chromium (~15–17%) for corrosion resistance
Moderate in nickel (~3–5%) – just enough for toughness, not enough to stay austenitic
Alloyed with copper (~3–5%) and niobium/columbium for precipitation hardening

This balance means:

On cooling from solution treatment, 17-4 transforms to a martensitic structure, not austenitic.
Aging heat treatments then form fine copper precipitates, boosting strength but keeping the magnetic martensitic base.

That martensitic backbone is why 17-4 stainless steel is magnetic across its normal conditions (H900, H1025, H1150, etc.).

Microstructure: 17-4 vs 300 series (304, 316)

Here’s the simple comparison:

17-4 PH (Type 630)
- Microstructure: Martensitic + precipitates
- Behavior: Clearly magnetic, strong pull with a standard shop magnet
- Use case: High strength plus corrosion resistance where magnetism is OK or helpful
304 / 316 austenitic stainless
- Microstructure: Austenitic (can pick up a bit of strain-induced martensite from cold work)
- Behavior: Generally non-magnetic in annealed state, may become slightly magnetic after heavy forming or machining
- Use case: Food equipment, medical, and general stainless applications where magnetism should be low

If you’re investing in stainless investment castings and need to control magnetism from the start, locking in the right grade and microstructure up front is critical. That’s where a process-focused partner with deep experience in stainless investment casting grades and properties can help you choose between 17-4, 304, 316, or other options based on both corrosion resistance and magnetic behavior (stainless investment casting process and grades overview).

17-4 Stainless vs 304 and 316: Magnetism and Trade-Offs

17-4 vs 304 Stainless Magnetic Comparison

17-4 PH stainless steel is strongly magnetic in all typical conditions. It’s a martensitic precipitation-hardening grade, so a magnet grabs it hard—similar to many carbon and tool steels.
304 stainless is mostly non-magnetic in annealed condition, but:

Cold-worked 304 (bent, stamped, or machined heavily) often shows light to moderate magnetism.
The magnet pull on 304 is usually much weaker than on 17-4.

If you hold the same magnet to 17-4 and 304 side by side:

17-4: firm, obvious snap
304: little to no pull, maybe a light drag on cold-worked areas

17-4 vs 316 Stainless Magnetic Comparison

316 stainless is even more stable austenitic than 304 and is the go-to “non-magnetic” stainless in many US industries. In practice:

Annealed 316 is very low magnetism to practically non-magnetic.
Cold work can add slight magnetism, but still much weaker than 304, and nowhere near 17-4.
17-4 will feel multiple times stronger in magnetic pull than either 304 or 316.

If you need a quick field check, a basic stainless steel magnet test will clearly separate 17-4 from 304/316.

Strength, Hardness, and Corrosion Resistance Trade-Offs

Here’s the basic trade-off between 17-4, 304, and 316:

Property	17-4 PH (aged)	304 Stainless	316 Stainless
Magnetism	Strongly magnetic	Low to moderate (cold-worked)	Very low to nearly non-magnetic
Tensile strength (typical)	Very high (up to ~190 ksi in H900)	Medium (~70–85 ksi)	Medium (~70–90 ksi)
Hardness	High (tooling-level in H900)	Low–medium	Low–medium
General corrosion resistance	Good	Very good	Excellent, especially with chlorides
Chloride / salt resistance	Decent but not like 316	Fair	Best of the three

If you’re familiar with high-performance alloys like Inconel from guides such as this Inconel alloys comparison resource, 17-4 sits in that same “high-strength stainless” decision space—only with clearly stronger magnetic behavior.

When 17-4 Is a Better Pick Than 304 or 316 for Magnetic Setups

Pick 17-4 stainless steel over 304/316 when you need both magnetism and strength in one package:

Parts held on magnetic chucks or clamps (tooling, fixtures, workholding)
Rotating shafts, gears, couplings, pump parts where you want strong magnetic gripping during machining
High-strength components that still need stainless corrosion resistance and reliable magnetic response
Magnetic separation components where you want stainless that responds strongly to the magnetic field

Here, 304 and 316 are simply too weak magnetically for reliable magnetic workholding, especially on smaller or precision parts.

When to Avoid 17-4 and Stay with Fully Non-Magnetic Grades

You should not use 17-4 if the spec or environment calls for non-magnetic stainless:

MRI rooms, medical implants, and surgical tools where magnetic attraction is a safety issue
Sensitive sensors, precision instruments, compasses, and lab equipment where magnetic fields can’t be disturbed
Electronics, avionics, and defense systems that are sensitive to stray magnetic fields
Any job drawing that calls out “fully austenitic, non-magnetic stainless” or explicitly points to 316L/304L for magnetic reasons

In those cases, stick with:

316/316L or 304/304L in fully austenitic conditions
Specialty non-magnetic stainless or alloy systems designed for MRI and magnet-sensitive environments

Bottom line:

If you need high strength + strong magnet pull → 17-4 PH is the right tool.
If you need corrosion first and near-zero magnetism → 316 (or other fully austenitic grades) is the safer choice.

Effect of Heat Treatment on 17-4 Stainless Steel Magnetic Behavior

Heat treatment changes the strength and hardness of 17-4 PH, but it does not turn it non-magnetic. No matter the condition, 17-4 (UNS S17400 / AISI 630) stays clearly magnetic because its structure is martensitic at room temperature.

Solution Annealed (Condition A)

In Condition A (solution annealed and air cooled):

Structure is martensitic, so it’s already magnetic
Magnetic pull feels “firm,” similar to many 400 series stainless grades
It’s softer and easier to machine or prep for later aging, especially if you plan to add coatings or other surface treatments afterward

Aging Conditions: H900, H1025, H1150

After aging (H900, H1025, H1100, H1150, etc.):

All aged conditions remain strongly ferromagnetic
H900 (hardest, highest strength) usually feels slightly stronger to a magnet because of higher hardness and more uniform martensite
H1025 and H1150 are a bit softer, but still pull a magnet very clearly
In real shop use, you won’t feel a “non-magnetic” condition—only slight differences in pull

Can Any Heat Treatment Make 17-4 Non-Magnetic?

No standard heat treatment used in industry makes 17-4 PH fully non-magnetic. You can slightly reduce magnetic response by:

Very high temperature over-aging
Refining microstructure with specific cycles

…but it will still be magnetic enough to trigger a magnet test. If you need truly non-magnetic performance (MRI, high-end sensors), you should not rely on 17-4 at all.

Cold Work and Welding Effects

Cold work and welding change the magnetic behavior, but they don’t remove it:

Cold working (forming, heavy machining, shot peening):
- Can increase hardness and often makes the part feel more magnetic
- Local areas may show stronger magnet pull than the base material
Welding:
- Weld metal and HAZ stay magnetic
- Microstructure near the weld can shift, so you may feel slight variation in magnet strength along the weld

Bottom line: every practical heat treatment, cold work step, or weld cycle keeps 17-4 stainless steel magnetic, so plan your design and inspection around that fact.

How to test if 17-4 stainless is magnetic

Testing whether 17-4 stainless steel is magnetic is simple, and you don’t need lab gear to do it.

Simple magnet test anyone can do

Use a small neodymium magnet (the shiny silver rare-earth type works best):

Clean a spot on the 17-4 surface (wipe off oil, scale, or dirt).
Touch the magnet directly to the metal.
Tilt and try to slide the magnet off.

If it “snaps” on and resists sliding, your 17-4 stainless steel is strongly magnetic. This is normal for martensitic precipitation-hardening grades like 17-4 PH (Type 630, UNS S17400).

If you’re doing shop inspections or incoming QC, you can pair this with more formal checks and basic material testing and quality methods like those outlined in our testing and quality control guide.

What strong vs weak magnetic pull feels like

Here’s what you’ll feel in your hand:

Strong pull (typical 17-4 PH)
- Magnet “jumps” to the surface from a short distance.
- Hard to slide off with your finger.
- Takes a noticeable effort to pull straight off.
Weak pull (lightly magnetic stainless, some 304/316)
- Magnet only grabs when it’s directly touching.
- Slides easily with light finger pressure.
- Feels more like it’s “sticking from friction” than true lock-on.

17-4 vs 304 vs 316 magnet pull

In real-world shop tests:

17-4 stainless steel (magnetic)
- Clear, strong attraction.
- Behaves similar to many 400-series stainless grades.
304 stainless (usually weakly magnetic or nearly non-magnetic)
- Annealed 304 is often almost non-magnetic.
- After forming or welding, it may show slight magnetism, but nowhere near 17-4.
316 stainless (more non-magnetic than 304 in most cases)
- Typically very low magnetism in annealed condition.
- Even when cold worked, still weaker than 17-4.

If your magnet sticks to one sample very hard (17-4) and just barely or not at all to another (304/316), you’re seeing the difference between martensitic precipitation-hardening and austenitic stainless.

Common testing mistakes to avoid

When you’re checking 17-4 stainless steel magnetism, avoid these issues:

Using a very weak fridge magnet
- Use a neodymium magnet; cheap fridge magnets can miss light magnetism.
Testing through coatings or thick plastic bags
- Paint, thick powder coat, or plastic spacers can make magnet pull feel weaker.
Comparing different part sizes
- A large thin sheet may feel different than a small thick bar; always compare similar shapes and thicknesses.
Assuming “non-magnetic” means zero pull
- Many “non-magnetic” stainless grades can show slight magnetism after cold work or welding.

For critical jobs—especially where magnetism ties into process choice, alloy selection, or quality requirements—combine the magnet test with proper material documentation and testing procedures, as you would for any high-spec alloy in our processes and alloy selection guide.

Applications Where 17-4 Stainless Steel Magnetic Properties Help

Magnetic workholding and fixtures

When you need parts to stay locked down, 17-4 stainless steel magnetic parts are a solid match for:

Magnetic chucks and clamps on CNC mills, grinders, and turning centers
Magnetic fixtures for repeat setups and high-volume runs
The material’s strong, consistent magnetic response means better holding force and fewer slips, which is especially useful if you’re running tight-tolerance jobs or high feed rates on modern CNC turning setups.

Magnetic separation and food processing

In U.S. food and beverage plants, 17-4 PH magnetic properties are a big plus when you need:

Magnetic separation bars, grates, and housings that must be detected and cleaned easily
High-strength, corrosion-resistant components exposed to washdowns and chemicals
You get the benefit of magnetic detectability plus good corrosion resistance, making 17-4 a better option than plain carbon steel in hygienic environments.

High-strength shafts, gears, and pump components

For rotating equipment and power transmission, 17-4 PH stainless steel offers:

Magnetic stainless steel shafts and gears that can be held on magnetic chucks during machining
Pump shafts, impellers, and housings where both strength and magnetic workholding matter
The combination of high strength, hardness, and a strong magnetic pull cuts setup time and improves stability on the machine.

Oil & gas, aerospace, and marine

In tougher environments like oil and gas, aerospace, and marine engineering, 17-4 is widely used for:

Valves, downhole tools, and fittings that are both strong and magnetic
Aerospace hardware and structural parts where inspection, handling, or fixturing leverage magnetism
Marine components (propeller hubs, shafts, and rigging parts) where strength, corrosion resistance, and magnetic workholding all count, especially alongside other marine-grade alloys used in demanding marine engineering applications.

Whenever you need high strength plus reliable magnetism for machining, handling, or separation, 17-4 stainless is one of the most practical stainless options on the table.

When 17-4 Stainless Magnetism Is a Problem

Even though 17-4 stainless steel is strong, hard, and corrosion-resistant, its magnetic behavior can be a dealbreaker in some setups.

MRI and Medical Environments

For MRI rooms, surgical tools near imaging equipment, and certain implants, any magnetic stainless, including 17-4, is usually a no-go. The strong magnetic field can:

Pull or shift magnetic parts
Distort imaging results
Create safety risks around the magnet

In these cases, you want fully austenitic, non-magnetic stainless or even non-ferrous metals like titanium or certain copper alloys instead of 17-4.

Precision Instruments and Sensors

In labs, metrology setups, and sensor housings, 17-4’s magnetism can:

Skew readings on load cells, Hall sensors, magnetometers
Cause subtle, repeatability issues in precision stages or optical mounts
Interact with external magnetic fields and create noise

Here, I’d lean toward 304, 316L, or specialty low-magnetic stainless grades, especially if you’re measuring tiny forces, fields, or displacements.

Electronics and Magnetic Interference

Around sensitive electronics and coils, 17-4 stainless steel can:

Concentrate or redirect magnetic fields
Increase EMI risk in high-frequency or high-precision circuits
Affect inductors, transformers, and magnetic sensors

If you’re building enclosures, brackets, or frames near electronics, you’re usually better off with non-magnetic stainless, aluminum, brass, or titanium alloys like those used in high-end aerospace and electronics hardware.

Choosing Non-Magnetic Stainless Alternatives Instead of 17-4

When magnetism is a problem, I typically recommend:

304 / 304L stainless – Good “low-magnetic” default for general use
316 / 316L stainless – Better corrosion resistance, still low magnetism in annealed condition
Non-ferrous metals – Aluminum, brass, or copper alloys where stainless isn’t mandatory

If your project absolutely cannot tolerate magnetic attraction (MRI, high-end lab gear, sensitive sensors), tell your supplier clearly:

“Non-magnetic or fully austenitic stainless required”
“Low permeability, no martensitic or PH stainless like 17-4”

That way you avoid accidentally getting a magnetic stainless bar like 17-4 when you needed a truly non-magnetic material.

Benefits and drawbacks of using magnetic 17-4 stainless

Key advantages of 17-4’s magnetic behavior

Magnetic 17-4 stainless (17-4 PH, Type 630) gives you a rare combo: high strength, good corrosion resistance, and solid magnetic response. In real use, that pays off when you need:

Magnetic workholding – Parts grip strongly on magnetic chucks and fixtures, so machining and grinding are more stable.
Positioning and sensing – Its ferromagnetic behavior makes it easier to use proximity sensors, magnetic pickups, and holding latches.
High-strength components – Shafts, gears, pump parts, and structural hardware that must be both strong and magnet-friendly.

If you mainly design steel parts and occasionally swap between carbon steel and stainless, 17-4 is a smooth upgrade when you still want magnetic clamping but need better corrosion resistance than plain steel or basic low-carbon steel bolts.

Limitations vs non-magnetic stainless grades

Compared with fully non-magnetic austenitic grades like 304 or 316, magnetic 17-4 stainless has some trade-offs:

Not suitable where “zero magnetism” is required – MRI rooms, sensitive lab gear, and some defense or aerospace electronics may reject any ferromagnetic material.
Higher risk of magnetic interference – Stronger magnetic pull can affect sensors, compasses, and EMI‑sensitive devices.
Slightly lower corrosion resistance than 316 – Especially in aggressive chloride or coastal environments.

If your spec calls for non-magnetic or “austenitic only,” 17-4 PH is usually not acceptable, even in Condition A.

Balancing magnetism, corrosion resistance, and strength

Here’s the basic trade-off landscape for 17-4 stainless steel magnetism:

Factor	17-4 PH (magnetic)	304 / 316 (mostly non-magnetic)
Magnetism	Strongly magnetic	Very low to mild (cold-worked)
Tensile strength	Very high (especially H900)	Moderate
Hardness / wear	High	Lower
Corrosion resistance	Good (316 usually better)	316 is excellent, 304 is good
Machining with mag chucks	Excellent	Poor (weak magnetic response)

You’re always trading magnetic response vs corrosion and “clean” non-magnetic behavior. For most industrial users in the U.S., 17-4 hits a sweet spot when you need strength + magnetic workholding + decent corrosion resistance in one material.

How to decide if 17-4 fits your project

Use this quick checklist when deciding if 17-4 stainless steel’s magnetic properties work for your project:

Choose 17-4 if:

You want a magnet to grab the part (mag chucks, clamps, separation, sensing).
You need high strength and better hardness than 304/316.
Your environment is wet or mildly corrosive, but not extremely chloride-heavy.

Avoid 17-4 and go non-magnetic if:

Your application is MRI, medical imaging, or precision sensors.
You have strict “non-magnetic stainless only” requirements.
You’re in severe marine or chemical environments where 316 or specialty austenitic alloys are preferred.

When in doubt, I always tell customers to:

Run a magnet test on sample pieces.
Confirm with the supplier which heat treatment condition (H900, H1025, H1150, etc.) you’re getting.
Match the strength and corrosion needs to your real service environment, not just the datasheet numbers.

If you need help comparing 17-4’s strength to aluminum or other metals in your design stack-up, you can use resources like this quick guide to yield strength in aluminum alloys as a reference point when you’re balancing materials.

Alternatives to 17-4 for Non-Magnetic Stainless Needs

If you need stainless parts that stay non-magnetic (or very low magnetic), 17-4 is usually the wrong pick. Here’s what I normally recommend instead.

304 and 316 as Standard Low-Magnetic Choices

For most U.S. shops and OEMs, 304 and 316 stainless are the go-to alternatives to 17-4 when low magnetism matters:

304 stainless steel
- Austenitic, low magnetic response in the annealed state
- Good all-around corrosion resistance
- Can pick up slight magnetism after heavy forming or machining
316 stainless steel
- Better corrosion resistance than 304 (especially in chloride and marine environments)
- Also austenitic and typically very weakly magnetic
- Often the first choice for food, marine, and light chemical applications

If you need zero magnetic pull near sensitive electronics, MRI, or lab equipment, let your supplier know you need fully austenitic, solution-annealed material and minimal cold work.

Fully Austenitic and Low-Magnetism Grades

For tighter magnetic limits than 304/316 can reliably hit, I look at specialty austenitic stainless grades:

Super austenitic grades (e.g., 904L, 254SMO) – very low magnetism, excellent corrosion resistance
Nitrogen-strengthened grades – higher strength while staying austenitic
Special non-magnetic alloys – for extreme cases where any pull is unacceptable

Where magnetism is a deal-breaker but you still need good wear or sliding properties, non-ferrous options like precision-machined bronze components can also be a strong fit, especially in fixture hardware or guide elements, similar to what we do in our bronze machining services.

17-4 vs 410, 420, and 440C Magnetism

If you’re comparing against other hard stainless grades, keep this in mind:

17-4 PH (Type 630) – strongly magnetic in all heat-treated conditions
410 stainless – martensitic, magnetic, moderate corrosion resistance
420 stainless – higher carbon, hardenable, very magnetic
440C stainless – high hardness, very magnetic, more tool-steel-like behavior

From a magnetism standpoint, 17-4, 410, 420, and 440C are all in the “magnetic” bucket. If your setup needs low or near-zero magnetism, none of these are ideal.

How to Pick the Right Stainless for Magnet-Sensitive Setups

When I’m helping spec stainless for magnet-sensitive environments (lab, medical, aerospace sensors, etc.), I focus on:

Magnetism requirement
- “No visible pull” with a standard shop magnet?
- Or documented max permeability / max residual magnetism?
Environment
- Indoor, outdoor, marine, chemical, food, vacuum?
- This usually pushes you toward 316 or higher-alloy austenitic grades.
Strength vs. non-magnetic
- If high strength matters: consider austenitic + design changes (thicker sections, reinforcement) rather than jumping to 17-4 or 400 series.
Verification
- Ask your supplier for:
  - Grade and condition (annealed vs cold worked)
  - Any magnetic testing data, if your project is critical
  - Certification that material is fully austenitic, solution annealed

If your priority list is non-magnetic first, corrosion resistance second, strength third, you’re almost always better off with 304/316 or other fully austenitic stainless instead of 17-4.

FAQs on 17-4 Stainless Steel Magnetism

Is 17-4 stainless steel always magnetic?

Yes. 17-4 PH (UNS S17400 / AISI 630) is a martensitic precipitation-hardening stainless steel, so it’s inherently ferromagnetic in every normal condition (Condition A, H900, H1025, H1150, etc.). The pull strength might change slightly with heat treatment, but it will not behave like non-magnetic 304 or 316.

Can heat treatment or aging make 17-4 non-magnetic?

No. No standard heat treatment will turn 17-4 into a fully non-magnetic stainless steel. Solution annealing and aging cycles only tweak hardness, strength, and toughness. The martensitic structure that makes 17-4 stainless steel magnetic stays in place.

Can I demagnetize 17-4 stainless steel parts?

Yes, you can demagnetize 17-4 using a proper degausser / demagnetizer coil. That removes residual magnetism picked up from machining, magnetic chucks, or service. But keep in mind:

The base metal is still magnetic and will attract a magnet.
It can become magnetized again during use (especially in magnetic workholding setups or high‑load rotating parts).

How does 17-4 magnetism compare to 400 series stainless?

In general, 17-4 PH is similar in magnetism to 410 or 420 and a bit less magnetic than high‑carbon 440C, but all of them are strongly ferromagnetic compared with 300 series. If you’re used to magnetic stainless shafts or gears in 410 or 420, 17-4 will feel familiar: strong attraction, easily held with a magnetic chuck, and responsive to magnetic separation.

What should I ask my supplier before buying 17-4 for magnetic applications?

Before you commit, I always recommend asking your supplier:

Exact grade and spec: Confirm it’s 17-4 PH (UNS S17400 / AISI 630).
Heat treatment condition: Condition A, H900, H1025, H1150, etc. (this affects strength and residual magnetism, not “magnetic vs non-magnetic”).
Product form: Bar, plate, forgings, or machined components – permeability can vary slightly.
Previous processing: Any cold work, grinding, or magnetic workholding that might add residual magnetism.
Certification: Material test report (MTR) listing mechanical properties and condition.

If you’re combining 17-4 parts with other high‑strength alloys (for example, 8620 or similar in assemblies), it also helps to compare their behaviors and machining needs up front; we go into that kind of detail on our 8620 steel material overview so buyers can line up the right grade for the right job.