Invar 36 (Fe-36Ni, UNS K93600): Round Bars, Seamless Tubes & Plates — Technical Data Sheet

Quick Answer: What Is Invar 36?

Invar 36 (Fe-36Ni, UNS K93600) (UNS K93600 / W.Nr. 1.3912 / 4J36) is a premier iron-nickel low-expansion alloy formulated for service environments demanding high mechanical strength and exceptional corrosion resistance. Its high performance stems from the a stable austenitic matrix with approximately 36% nickel, whose low coefficient of thermal expansion (CTE) arises from magnetostrictive effects near the Curie point within its stable austenitic iron-nickel matrix. It is typically supplied in the solution-annealed or stress-relieved condition; final dimensional stability requires careful heat treatment. Operating efficiently designed for service from cryogenic temperatures up to approximately 230°C (450°F) with ultra-low expansion, Invar 36 is widely utilized in precision instruments, optical benches, laser resonators, LNG tanks, and composite tooling.

Product Overview

At the atomic level, its face-centered cubic (FCC) austenitic matrix that remains stable over the low-expansion temperature range. Its primary advantage is an extremely low coefficient of thermal expansion (approximately 1.2 × 10⁻⁶ /°C at 20°C) for dimensional stability, which yields corrosion resistance is comparable to mild steel; Invar is generally used with protective coatings in aggressive environments.

Shanghai Hangbo Alloy Group Co., Ltd., established in 2012, stands as a top-tier global manufacturer and supplier of Invar 36. Operating under a certified ISO 9001:2015 quality management system, we command an export network covering 50+ countries. Our portfolio contains high-precision centerless ground round bars, heavy industrial plates, and high-pressure seamless tubing engineered for critical industrial applications. By managing carbon distribution and grain refinement during melting and forging, we ensure our material provides robust structural performance under severe stress. Every order comes with 100% material traceability and certified documentation, ensuring compliance with strict global engineering standards.

Executive Standards

Shanghai Hangbo Alloy Group Co., Ltd. manufactures Invar 36 in strict compliance with international technical specifications:

Note: Shanghai Hangbo executes 100% confirmation of chemical compliance using Optical Emission Spectroscopy (OES) for every melt lot.

Chemical Composition

The corrosion-resistant profile of Invar 36 depends on its exact chemical balance. Chromium ensures high-temperature oxidation resistance, while molybdenum safeguards against localized pitting in chloride environments.

Mechanical Properties

Invar 36 delivers excellent design allowable stresses. The data below outlines typical properties for annealed stock.

Room-Temperature Mechanical Properties

High-Temperature Performance: Strength Retention Analysis

Invar 36 retains remarkable mechanical properties under thermal stress, establishing its credentials as a critical superalloy:

How Invar 36 Is Produced

Round Bar & Forging

• 1. VIM + ESR Double Melting: ensures high purity and uniform nickel distribution.
• 2. Hot Forging / Rolling: worked to refine grain and ensure homogeneity.
• 3. Solution Annealing / Stress Relieving: optimized to stabilize CTE.
• 4. Precision Grinding: bars ground to tight tolerances for dimensional stability.

Sheet, Plate & Strip

• 1. Hot Rolling: controlled reduction.
• 2. Cold Rolling: precise gauge control for strip and foil.
• 3. Stress Relieving: heat treatment to stabilize dimensions.
• 4. Surface Finish: bright or pickled finish as required.

Wire

• 1. Hot Drawing: precise diameter control.
• 2. Stress Relieving: optimized for low CTE.
• 3. Surface Finish: bright, clean wire for electronic applications.

Industry Applications: Solving Engineering Challenges

Precision Metrology

Invar 36 is essential for precision measuring instruments, optical benches, and laser resonator structures where thermal drift must be minimized.

Cryogenic Engineering

Used for LNG tank supports, transfer lines, and cryogenic instrumentation because its low CTE remains stable at very low temperatures.

Composite Tooling

Its dimensional stability makes it ideal for molds and tooling used in composite aerospace structures.

Electronics & Telecommunications

Invar is used for shadow masks, lead frames, and precision frames in electronic packaging.

Quality Assurance: 7-Stage Zero-Defect Inspection Protocol

Shanghai Hangbo Alloy Group Co., Ltd. deploys an intensive inspection matrix to support a zero-defect mandate across all production lines:

• 1. Chemical verification: OES analysis on every melt batch alongside handheld PMI validation on finished products ensures composition parameters match executive limits.
• 2. Ultrasonic Testing (UT): Performed per ASTM A388 standards across all bars and plates to confirm the absence of inner voids, seams, or gas inclusions.
• 3. Eddy Current Testing (ET): Applied 100% to tubes following ASTM E309 protocols to check surface and sub-surface continuity.
• 4. Hydrostatic Pressure Verification: Tubes undergo hydrostatic tests up to 10,000 PSI to verify wall integrity under high-pressure parameters.
• 5. Mechanical Destructive Testing: Tensile, offset yield, elongation, and Brinell hardness examinations are executed per heat lot to verify strength criteria.
• 6. Dimensional Metrology Check: Digital calipers and computerized laser sensors measure geometry, guaranteeing all diameter, wall, and length tolerances match orders.
• 7. Visual and Microstructure Audit: Surface quality checks are paired with metallographic microscope tests to evaluate grain size (ASTM E112) and phase homogeneity.

All items leave our facilities accompanied by ISO 9001:2015 certification and EN 10204 3.1 Mill Test Certificates. Third-party inspection options through SGS, TUV, or Bureau Veritas (BV) are organized upon customer request.

Frequently asked questions