Steel Alloy 79 H2-Anneal
Heat-treated state
UNS K94100 · also Permalloy 80, Mu-metal
Choose for finished shields/cores where maximum permeability and lowest coercivity are needed; parts must not be bent or machined afterwards.
Values for the H2-Anneal condition
Other Alloy 79 tempers and conditions
Alloy 79 is listed in 4 conditions; see the grade overview at Alloy 79.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
H2-AnnealThis page final dry-hydrogen anneal ~1100–1180 °C with controlled slow cool (magnetic properties developed) | Choose for finished shields/cores where maximum permeability and lowest coercivity are needed; parts must not be bent or machined afterwards. | 230 | 500 | 42 | 105 HB | 3 % IACS |
Hot Rolled + Annealed | Heavy-section form for machined cores, pole pieces and thick shield housings. | 260 | 560 | 38 | 130 HB | 3 % IACS |
AnnealedDefault mill (strand/bright) annealed strip, sheet and bar, soft and formable | Standard stock condition: soft enough to stamp, draw and machine, with final hydrogen anneal done after fabrication. | 270 | 550 | 40 | 120 HB | 3 % IACS |
Cold rolled | Use when springiness, flatness or thin gauge matters and the part will be magnetically annealed later; magnetic properties in this state are poor. | 700 | 830 | 3 | 22 HRC | 3 % IACS |
What is Alloy 79 H2-Anneal?
Alloy 79 H2-Anneal is Alloy 79 heat treated to H2-Anneal — choose for finished shields/cores where maximum permeability and lowest coercivity are needed; parts must not be bent or machined afterwards. Alloy 79 H2-Anneal has a yield strength of 230 MPa (33.4 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 97% of steel grades. Elongation at break is 42% and the elastic modulus is 200 GPa (29 Msi). Alloy 79 H2-Anneal has a density of 8.74 g/cm³ (0.316 lb/in³), heavier than 100% of steel grades. It melts at 1,425°C (2,597 °F). Annealed is the default condition FabDigit quotes; H2-Anneal is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 42%, better than 100% of steel grades
- Good corrosion resistance — 50/100, better than 99% of steel grades
- Polishes to a fine finish — 75/100, better than 94% of steel grades
- Forms and bends easily — 80/100, better than 93% of steel grades
Limitations
- High embodied carbon — 11 kg CO₂/kg, worse than 100% of steel grades
- Low strength — 230 MPa (33.4 ksi), worse than 97% of steel grades
- Low electrical conductivity — 3 % IACS, worse than 91% of steel grades
- Difficult to machine — 28/100, worse than 91% of steel grades
- Poor heat conductor — 31 W/m·K (17.9 BTU/hr·ft·°F), worse than 83% of steel grades
Alloy 79 H2-Anneal properties
Typical room-temperature values for Alloy 79 H2-Anneal; 22 are specific to this condition. Other listed values are Alloy 79 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
Alloy 79 H2-Anneal has a density of 8.74 g/cm³ (0.316 lb/in³), heavier than 100% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical14
Alloy 79 H2-Anneal has a yield strength of 230 MPa (33.4 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 97% of steel grades. Elongation at break is 42% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
Alloy 79 H2-Anneal is rated for continuous service to 400°C (752 °F). It conducts heat at 31 W/m·K (17.9 BTU/hr·ft·°F), worse than 83% of steel grades. Thermal expansion is 12.7 µm/m·K (7.06 µin/in·°F).
Electrical3
Alloy 79 H2-Anneal conducts electricity at 3 % IACS, worse than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), better than 99% of steel grades.
Sustainability4
Producing a kilogram of Alloy 79 H2-Anneal takes about 115 MJ of energy and emits 11 kg of CO₂ — more than 100% of steel grades. Typical recycled content is 25%.
Manufacturability6
Alloy 79 H2-Anneal's machinability is poor (28/100, worse than 91% of steel grades); weldability good (60/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Alloy 79 H2-Anneal
Is Alloy 79 easy to machine?
Gummy and work-hardening: use sharp positive-rake carbide, rigid setup, heavy coolant, slow speeds and avoid dwell; finish light to limit strained surface layer before the magnetic anneal.
Can Alloy 79 be welded?
TIG, micro-plasma, laser and resistance welding all work with matching or Ni filler, but any weld or heat-affected zone must be re-annealed in dry hydrogen to recover permeability.
Can Alloy 79 be formed, bent or molded?
Excellent deep-drawing and bending in the annealed condition (shield cans, cylinders); all cold work degrades permeability, so form first and hydrogen-anneal last with minimal handling.
What surface finishes work on Alloy 79?
Not stainless — protect finished shields with electroless nickel, tin plate, chromate or clear lacquer; polishes well, and avoid abrasive blasting or mechanical straightening after the final anneal.
Alloy 79 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| NiASTM A753 Type 4 / 1J79 nominal 79–80 % | 79 – 82 | 80 |
| MoMu-metal / HyMu 80 modification | 3.8 – 5.5 | 4.3 |
| Mn | 0.3 – 0.8 | 0.5 |
| Si | 0.1 – 0.5 | 0.3 |
| Clow C essential for permeability | ≤ 0.03 | 0.02 |
| S | ≤ 0.02 | — |
| P | ≤ 0.02 | — |
| Curesidual | ≤ 0.2 | — |
| Crresidual | ≤ 0.3 | — |
| Febalance ≈14–16 % | balance | — |
Alloy 79 H2-Anneal — frequently asked
What is Alloy 79 H2-Anneal used for?
Alloy 79 H2-Anneal is typically used for precision magnetic shielding, audio transformer cores, recording heads, sensitive relays and fluxgate sensors. In short: highest permeability Ni-Fe; best low-field shielding alloy; anneal after all forming.
What is the yield strength of Alloy 79 H2-Anneal?
Alloy 79 H2-Anneal has a typical yield strength of 230 MPa (33.4 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 97% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is Alloy 79 H2-Anneal easy to machine?
Not especially — machinability is rated poor (28/100, worse than 91% of steel grades). Gummy and work-hardening: use sharp positive-rake carbide, rigid setup, heavy coolant, slow speeds and avoid dwell; finish light to limit strained surface layer before the magnetic anneal.
Can Alloy 79 H2-Anneal be welded?
Yes — weldability is rated good (60/100). TIG, micro-plasma, laser and resistance welding all work with matching or Ni filler, but any weld or heat-affected zone must be re-annealed in dry hydrogen to recover permeability.
What surface finishes work on Alloy 79 H2-Anneal?
Not stainless — protect finished shields with electroless nickel, tin plate, chromate or clear lacquer; polishes well, and avoid abrasive blasting or mechanical straightening after the final anneal.
Can Alloy 79 H2-Anneal be formed, bent or molded?
Excellent deep-drawing and bending in the annealed condition (shield cans, cylinders); all cold work degrades permeability, so form first and hydrogen-anneal last with minimal handling.
What is the maximum service temperature of Alloy 79 H2-Anneal?
Alloy 79 H2-Anneal is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alloy 79 Annealed and Alloy 79-CR?
Annealed is the default condition — standard stock condition: soft enough to stamp, draw and machine, with final hydrogen anneal done after fabrication. CR: use when springiness, flatness or thin gauge matters and the part will be magnetically annealed later; magnetic properties in this state are poor. Yield strength is 270 MPa in Annealed versus 700 MPa in CR.
Sources
- ASTM A753 — Standard Specification for Wrought Nickel-Iron Soft Magnetic Alloys (Type 4) — ASTM International (2018)
- GB/T 15018 / YB/T 5235 1J79 (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Soft Magnetic Alloys) — ASM International (1990)
- HyMu 80 Alloy technical datasheet — Carpenter Technology (2020)
- MAGNIFER 7904 soft magnetic alloy datasheet — VAC / VDM Metals (2019)
- MuMETAL shielding alloy data — Magnetic Shield Corporation (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.