3J21 Elastic Alloy (Co-Ni-Cr-Mo) - High-Strength Spring Alloy Supplier of Strip, Wire & Bar | Shanghai Hangbo Alloy Group
Date: 2026年8月4日 Categories: News Views: 353
By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012
Contact: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360
Quick Answer: What Is 3J21?
3J21 (40Co-Ni-Cr-Mo / GB/T 15018) is a cobalt-based elastic alloy that combines high elastic modulus, excellent fatigue resistance, and non-magnetic properties. It is the reference material for precision instrument hairsprings, pressure sensor diaphragms, vibrating-reed frequency standards, and aerospace elastic components that must maintain calibration through millions of stress cycles. Shanghai Hangbo Alloy Group supplies 3J21 as cold-rolled strip, wire, and round bar.
Key Properties
| Property | Value |
|---|---|
| Alloy Family | Co-Ni-Cr-Mo Elastic Alloy |
| Density | ~8.30 g/cm3 |
| Elastic Modulus (E) | ~210 GPa |
| Tensile Strength (Cold Worked+Aged) | >= 1370 MPa |
| Yield Strength | >= 1180 MPa |
| Hardness | 42-48 HRC |
| Magnetic | Non-magnetic |
| Key Standards | GB/T 15018, YB/T 5253 |
Product Overview
3J21 belongs to the "3J" series of Chinese precision elastic alloys ("J" for precise elastic limit). Unlike simple spring steels that rely on carbon for strength, 3J21 uses a cobalt-chromium-nickel-molybdenum matrix that is cold-worked and aged to achieve a unique combination of properties: high strength, constant elastic modulus across a wide temperature range, and complete non-magnetic behavior.
The alloy's dominance in precision instrumentation stems from its elinvar-like characteristics -- its elastic modulus remains nearly constant over typical ambient temperature swings (-20 to +80C), eliminating the thermal drift that corrupts mechanical clock and sensor accuracy.
Chemical Composition (wt.%)
| Element | Content |
|---|---|
| Co | 39.0-41.0 |
| Cr | 19.0-21.0 |
| Ni | 14.0-16.0 |
| Mo | 6.5-7.5 |
| Mn | 1.5-2.5 |
| C | <= 0.12 |
| Fe | Balance |
Mechanical Properties
| Condition | Tensile (MPa) | Hardness |
|---|---|---|
| Solution Treated | 700-850 | 20-25 HRC |
| Cold Worked + Aged | >= 1370 | 42-48 HRC |
Heat Treatment
Solution: 1150-1180C, water quench. Cold Work: 50-70% reduction. Age: 480-520C/3-5h.
Applications
| Industry | Component |
|---|---|
| Precision Instruments | Mechanical watch hairsprings, galvanometer suspension strips |
| Aerospace | Pressure sensor diaphragms, accelerometer springs |
| Medical | Surgical instrument springs, implantable device springs |
| Electronics | Relay contact springs, vibrating-reed frequency elements |
FAQ
Q1: 3J21 vs 17-7PH? 3J21 is non-magnetic, has superior fatigue life, and constant modulus vs. temperature. 17-7PH is lower cost but magnetic and has temperature-dependent modulus.
Q2: Is 3J21 magnetic? No. Non-magnetic (austenitic matrix). Essential for instruments where magnetic fields corrupt readings.
Q3: Price? $60-100/kg EXW (40% Co content). Contact sales@hangboalloy.com.
Q4: Forms? Strip(0.05-2.0mm), wire(0.1-5.0mm), bar(6-50mm). SGS available.
Contact & Complete Product Range
Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | Email: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360 | www.nickel-alloy.com
Ni: NI200-N6 | Monel: 400-K500 | Inconel: 600-725 | Incoloy: 800-A286 | Hastelloy: C-276-N | Nimonic: 75-263 | Haynes: 25-556 | Precision: 1J22-4J45 | High-Strength: 18Ni250-AerMet100-PH13-8Mo
Bars | Tubes | Plates | Forgings | Welded Pipes | Fittings | Wire | Strip. SGS/BV/TUV.
