MAGNETIC BEHAVIOR GUIDE
17-4 PH is ferromagnetic in every normal heat-treatment condition.
Heat treatment can change measured response, but H900, H1150 and Condition A do not turn 17-4 PH into a non-magnetic alloy.
Need a pass/fail value?
Specify permeability, residual field or pull force—“magnetic” alone is not a measurable acceptance criterion.
Need grade verification?
Use PMI or chemistry records. A handheld magnet cannot distinguish 17-4 PH from other ferromagnetic stainless steels.
Engineering caution: Demagnetizing a part reduces residual field; it does not remove the alloy’s inherent ferromagnetic structure.
Quick answer: yes. 17-4 PH stainless steel (Type 630, UNS S17400) is normally ferromagnetic because its matrix is predominantly martensitic after solution treatment and cooling. Aging conditions such as H900, H1025 and H1150 can change magnetic measurements, but none should be assumed “non-magnetic.” If permeability, residual field or magnetic cleanliness is a functional requirement, specify a numerical limit and test the finished component.
| Question | Engineering answer |
|---|---|
| Will a magnet attract 17-4 PH? | Normally yes, but attraction is not a grade-verification method. |
| Does heat treatment remove magnetism? | No standard 17-4 PH aging condition should be assumed non-magnetic. |
| Can magnetism vary? | Yes—condition, cold work, machining, residual stress, temperature and geometry affect measurement. |
| Can a magnet identify 17-4? | No. Many ferritic, martensitic and duplex stainless steels are also magnetic. |
Why 17-4 PH Stainless Steel Is Magnetic
17-4 PH is a precipitation-hardening stainless steel containing chromium, nickel, copper and niobium/columbium additions. Its high strength is developed by aging a martensitic matrix. Martensitic stainless structures are ferromagnetic, unlike fully austenitic structures that normally show low magnetic permeability in the annealed condition.
Condition A refers to the solution-treated condition used as the starting point for subsequent aging. It is not an austenitic, non-magnetic delivery state. After solution treatment and cooling, the alloy is predominantly martensitic and remains magnetic.
Effect of H900, H1025 and H1150 Conditions
Aging changes precipitate distribution, strength, toughness and residual stress. It can also alter measured magnetic properties. However, generic labels such as “Condition A is moderately magnetic” or “H900 is more magnetic” are not suitable purchase requirements because they omit the test method, field strength, specimen geometry and temperature.
| Condition | Primary reason to specify | Magnetic note |
|---|---|---|
| Condition A | Solution-treated starting condition for fabrication or aging | Ferromagnetic; not a non-magnetic condition |
| H900 | High strength/hardness | Test the finished condition if a numerical magnetic limit applies |
| H1025 | Strength-toughness balance | Do not infer permeability from the condition name alone |
| H1150 | Greater toughness and stress-corrosion resistance than peak-aged conditions | Still magnetic; verify the actual component when required |
Why a Simple Magnet Test Is Not Enough
A permanent magnet can distinguish a strongly magnetic item from a low-response material, but it cannot prove that the material is 17-4 PH. Grades 410, 420, 430, duplex 2205 and many carbon or alloy steels are also attracted to magnets. Component thickness, air gap, surface coating and magnet strength also change the perceived pull.
For positive grade identification, use traceability and an approved PMI method. Handheld XRF can verify many major alloying elements but has limitations for light elements and cannot determine heat-treatment condition. Optical emission spectroscopy or laboratory chemistry may be required. Hardness and mechanical testing can help verify condition when specified.
How to Measure Magnetic Requirements
- Relative permeability: define the test method, applied field, temperature and acceptance value.
- Residual magnetic field: specify the measurement location, instrument, units and maximum value after machining or inspection.
- Magnetic particle examination: use the governing NDT procedure and apply demagnetization requirements when needed.
- Functional testing: sensors, actuators, MRI-adjacent equipment or precision instruments may require assembly-level verification.
Magnetic response also changes with temperature. A room-temperature magnet test cannot validate performance across a cryogenic or elevated-temperature operating range.
17-4 PH Compared With Other Stainless Families
| Material family | Typical magnetic behavior | Important limitation |
|---|---|---|
| 17-4 PH / Type 630 | Ferromagnetic | Condition and processing affect measured values |
| 304/316 austenitic | Low response when fully annealed; can become magnetic after cold work or welding | “Non-magnetic” is not guaranteed without a permeability limit |
| 410/420 martensitic | Ferromagnetic | Lower corrosion resistance and different heat treatment than 17-4 PH |
| 430 ferritic | Ferromagnetic | Not a strength/corrosion substitute for 17-4 PH |
| 2205 duplex | Magnetic due to ferrite-containing structure | Different strength, corrosion and fabrication behavior |
Procurement Checklist
Specify Type 630/UNS S17400, governing material standard, product form, dimensions, heat-treatment condition, mechanical properties, certificate type, PMI/NDT requirements and any numerical magnetic acceptance criterion. Do not write only “magnetic” or “non-magnetic” when component function depends on permeability.
For available forms, review stainless steel bar, stainless steel sheet and plate and stainless steel pipe, then provide the exact 17-4 PH condition and inspection scope with the RFQ.
Frequently Asked Questions
Is 17-4 PH suitable for a non-magnetic component?
Generally no. It is a ferromagnetic precipitation-hardening stainless steel. Select a material with verified permeability data if low magnetic response is essential.
Can demagnetization make 17-4 PH non-magnetic?
Demagnetization can reduce residual magnetism after processing or magnetic-particle inspection, but it does not change the alloy’s ferromagnetic material behavior.
Can magnetic attraction verify H900 or H1150?
No. Verify aging condition through traceable heat treatment and the specified mechanical or hardness tests, not magnet pull.
Request 17-4 PH material with defined testing
Send the product form, standard, condition, dimensions, quantity, magnetic or NDT limits, certificate and destination to sales@sakysteel.com.
Technical RFQ
Turn the article into a usable purchase specification.
Send the condition, dimensions and magnetic acceptance method to sales@sakysteel.com.
Post time: Jun-24-2025