Alloy Wire
Ken-tron draws 42 Alloy, 46 Alloy, 48 Alloy, and 52 Alloy — a family of controlled-expansion, low-expansion, nickel-iron sealing alloys — for customers in the aerospace, appliance, defense, power generation, lighting, medical, electronics, music, semiconductor, telecommunications, and other industries. The most commonly ordered grade is 52 Alloy (also called Alloy 52), a 50.5% nickel-iron composition formerly supplied to the ASTM F30 specification. F30 has since been withdrawn/consolidated, and Ken-tron now draws 52 Alloy to SAE AMS-I-23011, Class 2 (UNS N14052), which carries forward the same chemistry, tempers, and thermal-expansion requirements as legacy F30.
52 Alloy is a nickel-iron alloy suitable for glass and ceramic sealing to metal, engineered to match the thermal expansion of soft (potash-soda-lead and soda-lime) glasses. It is widely used in magnetic reed switch blades, lead wire for mercury switches, and hermetic glass-to-metal seals in semiconductor packages and electronic components.
Alloy Family Overview
| Alloy | Nominal Composition | Legacy Spec | Current Reference | Typical Use |
|---|---|---|---|---|
| 42 Alloy | 42% Ni, remainder Fe | ASTM F31 | AMS-I-23011 Cl. 6 (similar) | TO-header leads, glass seals |
| 46 Alloy | 46% Ni, remainder Fe | — | AMS-I-23011 Cl. 4 | Glazed-ceramic sealing |
| 48 Alloy | 48% Ni, remainder Fe | — | AMS-I-23011 Cl. 3 | Soda-lime glass sealing |
| 52 Alloy (most common) | 50.5% Ni, remainder Fe | ASTM F30 (formerly) | AMS-I-23011 Cl. 2, UNS N14052 | Reed switches, mercury-switch lead wire, semiconductor seals |
Chemical Composition
52 Alloy (UNS N14052) — SAE AMS-I-23011, Class 2 (all values weight percent; maximum unless a range or nominal value is shown):
| Element | 52 Alloy (wt%) |
|---|---|
| Nickel (Ni) | 50.5 (nominal) |
| Cobalt (Co) | 0.50 max |
| Chromium (Cr) | 0.10 max |
| Manganese (Mn) | 0.60 max |
| Silicon (Si) | 0.30 max |
| Carbon (C) | 0.05 max |
| Aluminum (Al) | 0.10 max |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.025 max |
| Iron (Fe) | Remainder |
Source: SAE AMS-I-23011C, Table II (Class 2), the current governing reference for the alloy formerly supplied to ASTM F30. The nominal nickel content is adjusted by the supplier as needed to meet the thermal-expansion requirement (see below).
Mechanical Properties
Tensile Strength by Temper (all AMS-I-23011 classes, incl. Class 2 / 52 Alloy)
| Temper | Tensile Strength (ksi) |
|---|---|
| Annealed | 85 max |
| 1/4 Hard | 90 – 115 |
| 1/2 Hard | 105 – 125 |
| Hard | 120 min |
Hardness, Rockwell B (Classes 2, 3, 4, 5, 7)
| Condition | Hardness (Rockwell B) |
|---|---|
| Annealed | 70 max |
| 1/4 Hard | 78 – 83 |
| 1/2 Hard | 84 – 88 |
Source: SAE AMS-I-23011C, Tables IV & V.
Temperature Coefficient of Thermal Expansion
| Temperature Range | Mean CTE (cm/cm/°C × 10⁻⁶) |
|---|---|
| 30 – 450°C | 9.6 – 10.1 |
| 30 – 550°C | 10.2 – 10.7 |
Source: SAE AMS-I-23011C, Table III (Class 2). 52 Alloy is formulated to match the expansion of soft, potash-soda-lead and soda-lime glasses, which have setting-point temperatures of roughly 410–590°C.
Physical Properties
| Property | Value |
|---|---|
| Density | 0.300 lb/in³ |
| Melting Point | ≈2,600°F |
| Electrical Resistivity | 260 ohm-cir mil/ft |
Sealing to Glass and Ceramic
52 Alloy belongs to the family of iron-nickel sealing alloys covered by SAE AMS-I-23011 (successor to MIL-I-23011), which groups sealing alloys by nickel content to match the thermal expansion of specific glass and ceramic families:
- Class 1 (Kovar, 29% Ni – 17% Co) — hard, low-expansivity borosilicate glasses; see Kovar Wire.
- Class 2 (52 Alloy, 50.5% Ni) — soft, potash-soda-lead and soda-lime glasses; setting points 410–590°C.
- Classes 3 & 6 — other soft-glass sealing compositions in the same family.
- Class 4 (46% Ni) — most frequently used for sealing to glazed ceramics.
Cold Forming & Drawing
52 Alloy is readily cold drawn and work-hardens predictably through the temper range shown above. Ken-tron draws the alloy to fine, close-tolerance diameters for reed switch blades and lead wire applications, and can supply bright-annealed, 1/4-hard, 1/2-hard, or full-hard tempers to suit forming and spring-back requirements downstream.
Applicable Standards & Specifications
| Standard | Scope | Grade |
|---|---|---|
| SAE AMS-I-23011, Class 2 | Iron-nickel sealing alloys — chemistry, temper, CTE, and dimensional tolerances | 52 Alloy (UNS N14052) |
| ASTM F30 (historical / superseded) | Iron-nickel sealing alloy, legacy designation | Equivalent to Class 2 |
Industries & Applications
| Industry | Typical Applications |
|---|---|
| Electronics & Semiconductor | Magnetic reed switch blades, lead wire for mercury switches, semiconductor package leads |
| Telecommunications | Relay and switch components |
| Aerospace & Defense | Hermetic glass-to-metal seals, connector pins |
| Medical & Lighting | Hermetically sealed components, lamp lead-in wire |
52 Alloy vs. Kovar
Both alloys are members of the same AMS-I-23011 sealing-alloy family but are matched to different glass types:
| Property | 52 Alloy (Class 2) | Kovar (Class 1) |
|---|---|---|
| Nominal Composition | 50.5% Ni, remainder Fe | 29% Ni, 17% Co, remainder Fe |
| Glass Type Matched | Soft potash-soda-lead / soda-lime glass | Hard, low-expansion borosilicate glass |
| CTE (30–450°C) | 9.6 – 10.1 × 10⁻⁶ cm/cm/°C | 5.1 – 5.5 × 10⁻⁶ cm/cm/°C |
| Typical Use | Reed switches, mercury-switch lead wire | Semiconductor headers, vacuum-tube leads |
Ken-tron Wire Drawing Capability
The Ken-tron Wire Division specializes in small-diameter, close-tolerance wire made to customer specifications. Our manufacturing process for 52 Alloy wire includes:
- Incoming material verification — mill certifications reviewed, chemistry confirmed against applicable standard
- Controlled cold reduction — percentage reduction between anneals managed to achieve target temper and dimensional tolerance
- In-process and final annealing — continuous strand annealing to provide uniform softening, controlled atmosphere to minimize surface oxide
- Dimensional inspection — diameter measured using calibrated gauges; tolerance held to customer specification
- Surface inspection — wire examined for seams, laps, or inclusions affecting fatigue performance or solderability
- Certification and documentation — mill certs and material traceability furnished with each shipment
Ken-tron manufactures to your custom specifications. For additional inquiries, please request a quote or contact us.
