Invar 36 Bright Bar
An Invar 36 Bright Bar is a high-precision,nickel-iron alloy rod engineered for applications requiring extreme dimensional stability under temperature fluctuations.Invar 36 is a binary alloy consisting of 36% nickel and approximately 64% iron.This specific ratio gives rise to the “Invar effect,” which causes the metal’s CTE to be about one-tenth that of carbon steel over a temperature range from low temperatures to approximately 400°F (260°C).
Key Material Properties
- Minimal Thermal Expansion:
It maintains nearly constant physical dimensions across severe seasonal or operational temperature swings. - Криогенная вязкость:
Unlike many steels that become brittle,Invar 36 retains excellent mechanical strength,ductility,and impact toughness at ultra-low temperatures. - High Structural Stiffness:
It provides high load-bearing strength,meaning precision platforms and mounting plates resist sagging or flexing during operation. - Устойчивость к коррозии:
It offers good resistance to atmospheric corrosion and mild industrial environments.
Applications of Invar 36 Bright Bar
- Laser frameworks
- Optical mounts
- Aerospace tooling
- Composite molds
- Cryogenic valves
- LNG piping
- Thermostat strips
- Seismograph components
- Clock pendulums
- Metrology instruments
- Satellite structures
- Waveguide tubes
- Circuit substrates
- Radar antennas
- Shadow masks
- Scientific instruments
We offer Invar 36 (UNS K93600 / ASTM F1684) bright bars in diameters ranging from OD 2mm to 210mm, manufactured in compliance with ASTM F1684, DIN 17745, and GB/T 14985.
We also supply high-performance alloy pipes (including Hastelloy, Incoloy, Inconel, and Monel) that are fully compliant with PED 2014/68/EU and CE marks for pressure equipment and precision applications.
All our production and testing processes are certified to ISO 9001, and all products are delivered with EN 10204 3.1 Mill Test Certificates ensuring ultra-low thermal expansion coefficients.With over a decade of experience in manufacturing,import,and export,we are your most trusted wholesaler in China.
Chemical Composition of Invar 36 Bright Bar
The chemical composition of an Invar 36 Bright Bar is strictly controlled.It is primarily a binary alloy consisting of roughly 36% Nickel and 64% Iron.The detailed chemical composition by weight percentage according to standard industry specifications includes:
| Ni | Fe | Mn | Si | C | Cr | Co | п | S |
|---|---|---|---|---|---|---|---|---|
| 35.0 – 37.0 | Остаток средств | 0.20 – 0.60 | ≤ 0.35 | 0.05 - 0.10 | ≤ 0.50 | 0.50 – 1.0 | 0.02 – 0.025 | 0.02 – 0.025 |
The Physics of the "Invar Effect"
The specific 36% Nickel ratio creates a precise atomic arrangement where the thermal expansion of the crystal lattice is naturally countered by magnetostriction.This yields a CTE of roughly 1.2 × 10-6/K between 20°C and 100°C,which is one-tenth that of standard carbon steel.Altering the nickel percentage by even 1% will drastically compromise this low-expansion property.
Machining Characteristics
Invar 36 does not machine like a standard stainless steel.Its composition makes it gummy,ductile,and prone to rapid work hardening.When machining bright bars into precision fasteners or components,technicians must employ sharp carbide tools,slower cutting speeds,and massive amounts of coolant to avoid burning out the tooling or distorting the workpiece.
Коррозионное поведение
Because Invar 36 lacks significant amounts of chromium,it does not have the corrosion resistance of 304 or 316 stainless steel.It offers moderate protection against dry atmospheric environments but is prone to pitting in marine or highly humid chloride environments.Bright bars are often oiled,coated,or plated if they are destined for corrosive working environments.
Physical and Mechanical Profiles
- Density:8.05 g/cm3 (0.291 lb/in3)
- Melting Point:1427°C (2600°F)
- Curie Temperature:
279°C (535°F) — It is ferromagnetic at room temperature but turns paramagnetic above this point,affecting its expansion stability.
Invar 36 Bright Bar Standards & Equivalent Designations
| Invar 36 Alloy (Low Expansion) | |||||
|---|---|---|---|---|---|
| Стандарт / Система | Эквивалентное обозначение | Форма продукта | GB (Китай) | GJB (Military) | GOST (Russia) |
| Китайский стандарт | 4J36 (Fe-Ni36) | Cold-drawn Bright Bars | GB/T 14986.2 | GJB 227A | – |
| Russian / CIS Standard | 36H / 36H-VI (36Н) | Centerless Ground Rods | GB/T 14985 | – | GOST 14080 / 10994 |
| ISO Chemical Name | Ni36 / FeNi36 | Peeled & Polished Bars | – | – | – |
| UNS System | UNS K93600 / K93602 | Free-cutting Bright Bars | – | – | – |
| Aviation / Aerospace | ASTM F1684 / Werkstoff 1.3912 | Precision Machining Rods | – | – | – |
| UK Designation | NILO Alloy 36 / Pernifer 36 | ||||
| Generic Trade Name | Invar 36, Alloy 36, Invar Steel | ||||
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Mechanical Properties of Invar 36 Bright Bar
The mechanical properties of an Invar 36 Bright Bar depend heavily on its heat treatment condition (annealed vs. cold-drawn/work-hardened) and the specific manufacturing standard,such as ASTM F1684 or GB/T 14986.2 [GB/T 14986.2].Because bright bars undergo processing like cold-drawing or centerless grinding,they often display higher strength profile limits than standard hot-rolled plates.
| Механические свойства | Annealed Condition | Cold-Drawn / Work-Hardened |
|---|---|---|
| Предел прочности | 430 – 550 MPa (62 – 80 ksi) | 600 – 850 MPa (87 – 123 ksi) |
| Предел текучести | 240 – 350 MPa (35 – 51 ksi) | 450 – 750 MPa (65 – 109 ksi) |
| Удлинение | ≥ 30% | 10% – 20% |
| Сокращение площади | ≥ 50% | 35% – 50% |
| Твердость по Бринеллю | 130 – 160 HB | 170 – 230 HB |
| Rockwell Hardness | 70 – 85 HRB | 90 – 98 HRB |
| Модуль упругости | 144 GPa (20.9 × 10⁶ psi) | 148 GPa (21.5 × 10⁶ psi) |
| Charpy V-Notch Impact | Excellent (≥ 120 J) | Moderate (≥ 60 J) |
Impact of Cold-Working
The process of creating a “Bright Bar” involves drawing or peeling metal through a die without heating it.This cold work changes the crystal structure:
- Strength Boost:
Cold-drawing increases the yield and tensile strength,making the bar much easier to machine cleanly without the metal tearing or dragging. - Residual Stress:
Cold-working introduces internal physical stresses.For high-precision laser or aerospace applications,these bright bars must undergo stress-relief annealing before final machining to prevent dimensional warping later.
Cryogenic Mechanical Performance
Unlike common structural steels that become brittle and fracture under deep freezing conditions,Invar 36 maintains excellent ductility and impact toughness at cryogenic temperatures.
- At -196°C (Liquid Nitrogen temperature),its Tensile Strength surges up to nearly 900 – 1000 MPa while retaining over 25% elongation.This makes it an ideal mechanical selection for cryogenic valving and LNG transport mechanisms.
Modulus of Elasticity VS Temperature
The Modulus of Elasticity measures structural stiffness.For Invar 36,this value is lower than structural steel.Furthermore,the modulus changes uniquely with temperature fluctuations:
- It reaches its peak stiffness near room temperature and decreases as temperatures drop or rise.Engineers designing high-precision structural supports must factor in this lower rigidity to avoid physical deflection under heavy loads.
The Interplay Between Strength and Thermal Expansion
There is a engineering trade-off between maximizing mechanical strength and preserving the lowest possible coefficient of thermal expansion:
- Annealing provides the lowest thermal expansion rate but yields lower mechanical strength.
- Cold Drawing increases mechanical strength and hardness but slightly raises the expansion coefficient.
- To achieve an ideal balance of high strength and low expansion,bright bars are often ordered in a stabilized heat-treated condition (830°C heating,water quench,followed by a 315°C soak and air cool).
Our Advantages in Manufacturing Invar 36 Bright Bar
Strict Composition Control
We employ vacuum induction melting coupled with vacuum arc remelting to precisely manage the 36% nickel balance while minimizing residual elements.Carbon,chromium,and trace impurities are strictly suppressed below industry limits,ensuring that the critical “Invar effect” remains flawless.This metallurgical precision guarantees that every single batch delivers an ultra-low,predictable coefficient of thermal expansion across all operating temperatures.
Превосходная отделка поверхности
Our advanced centerless grinding,cold-drawing,and polishing operations eliminate all hot-rolling scale and surface micro-cracks.We achieve an exceptional surface roughness profile and maintain tight dimensional tolerances matching international h9 to h11 precision grading.This ultra-smooth,bright surface reduces material waste,eliminates the need for initial rough peeling,and enables seamless feeding into automated CNC machinery.
Specialized Heat Treatment
To resolve the structural tension created during cold processing,we utilize proprietary three-stage stabilization and stress-relief annealing protocols.This thermal cycle optimizes the mechanical properties, providing a reliable matrix that will not warp,sag,or distort during complex machining cycles.By balancing structural tensile strength with the lowest possible expansion behavior,our bright bars remain dimensionally uniform before,during,and after your production runs.
Complete Testing Traceability
Every production lot undergoes rigorous laboratory verification, including ultrasonic defect scanning,eddy current surface checks,and thermal dilatometry testing.We document these steps thoroughly to provide complete material traceability,delivering every shipment alongside comprehensive EN 10204 3.1 Mill Test Certificates.Our physical and chemical quality control protocols ensure full compliance with international engineering frameworks,making us a deeply trusted partner for aerospace,defense,and cryogenic supply chains.
FAQs About Invar 36 Bright Bar
Unlike stainless steel,Invar 36 lacks chromium protection and oxidizes easily in humid environments.While the “bright” finish provides a smooth surface less prone to trapping moisture,the bars must be stored indoors in a climate-controlled area with relative humidity kept below 50%.They should remain wrapped in their original rust-preventative oil and VCI paper until the exact moment of machining.
Yes,it can be welded using standard methods like TIG or MIG. However,to maintain a matching ultra-low expansion rate across the entire joint,you must use a dedicated filler metal with an identical chemical makeup—typically sold commercially as Invarod or Alloy 36 filler wire.Using standard stainless steel filler wire will ruin the thermal stability at the weld zone.
Electroplating with gold,silver,nickel,or chromium does not change the internal atomic structure or bulk thermal expansion of the bar.It is highly recommended for parts deployed in marine or corrosive setups to add a barrier layer against rust.However,the plating thickness must be tightly regulated,as a thick coating of a highly expansive metal can create a microscopic bimetallic warping effect on ultra-precise components.
The material should not be used for low-expansion tasks above its Curie point of 279°C (535°F).Above this specific thermal threshold,the alloy undergoes a magnetic phase transition from ferromagnetic to paramagnetic.Once it becomes paramagnetic,the magnetostrictive effect completely stops,and the bar begins expanding rapidly at a rate similar to standard carbon steel.
Yes,fiber laser marking is a standard industry practice for part tracking and does not degrade the core mechanical stability.However,technicians should use the minimum effective power and localized pulse settings.Excessive thermal input from long-pulse deep engraving can create micro-zones of unannealed structural tension,which could lead to localized expansion variations.
To safeguard the straightness tolerances and smooth h9/h11 finish,bright bars are never shipped loose.Every individual rod is coated in a heavy anti-rust oil,sleeved in protective plastic netting,and packed into reinforced wooden crates lined with waterproof barriers.This prevents metal-to-metal rubbing and bending during long-distance maritime transit or forklift handling.
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