Alloy 600 (UNS N06600) Bar & Plate Selection Guide

Alloy 600 (Inconel 600, UNS N06600) is a solid-solution strengthened nickel-chromium-iron alloy. Its high-nickel matrix delivers outstanding resistance to chloride stress corrosion cracking, high-temperature oxidation and comprehensive corrosion resistance, making it ideal for high-temperature and mixed corrosive service conditions. ASTM B166 and ASTM B168 are the core procurement specifications separating bar-type and plate-type products, governing chemical composition, mechanical properties, dimensional tolerances, delivery condition, sampling rules and acceptance criteria. This guide is designed for engineers, purchasers, QC specialists and overseas buyers for accurate material selection, avoiding non-conformity during production and inspection.

ZYTC Alloy supplies Alloy 600 bars, flats, wires, plates, sheets and strips in compliance with ASTM B166 and ASTM B168. PMI, tensile test, hardness test, grain size inspection and NDT are available with third-party witness service upon request.

Clear Scope of Standards – First Criterion for Material Selection

Important Note: Both standards apply to UNS N06600 with identical chemical composition range, while sampling protocols, dimensional tolerances and acceptance criteria are not interchangeable. Never specify only “Alloy 600” on purchase orders. Always mark the corresponding ASTM standard number. For pressure vessel and ASME projects, ASME SB-166 / SB-168 can be adopted alternatively.

Fundamental Properties of Alloy 600 (UNS N06600)

Chemical Composition Range: Ni ≥72.0%, Cr 14.0–17.0%, Fe 6.0–10.0%, C ≤0.15%, balanced with trace impurity elements

• Corrosion Resistance: Resists chloride-induced stress corrosion cracking which commonly attacks stainless steel. Performs steadily in dry chlorine gas, hydrogen sulfide, seawater and flue gas scrubbing media. Limited service in weak acid environments. Not recommended for strong reducing acids such as pure hydrochloric acid and concentrated hydrofluoric acid.
• Heat Resistance: Sustainable service up to around 700°C for long-term exposure, and withstands oxidation at nearly 1000°C for short intervals. Excellent low-temperature toughness is retained.
• Fabrication: Readily weldable, machinable and formable under solution annealed condition. No age-hardening response. Post-weld stress relief is optional except for critical corrosion applications.
• Reference Mechanical Properties (Solution Annealed, baseline per standard): Tensile Strength ≥550 MPa, Yield Strength ≥240 MPa, Elongation ≥30%

Form-Based Selection: ASTM B166 Bar vs ASTM B168 Plate

ASTM B166 Bar, Flat & Wire – Recommended Applications

Choose ASTM B166 when your components are:

1. Rotating parts: valve stems, shafts, fasteners, bolts, pins, thermowell core rods
2. High-temperature furnace load-bearing components: heat treatment fixtures, furnace roller supports, locating pins
3. Machining blanks for custom parts and structural components in corrosive service
4. Wire products: woven mesh, sealing wire, spot welding electrodes, flexible corrosion-resistant connections

Available supply forms: hot-finished black bar, precision ground bar, cold drawn bright bar, hex bar, flat bar, cold drawn wire. Selection Tip: For ground bars, focus on surface roughness and diameter tolerance. Cold worked grades deliver higher strength with reduced ductility. Select solution annealed condition if further forming is required.

ASTM B168 Plate, Sheet & Strip – Recommended Applications

Choose ASTM B168 when your components are:

1. Pressure shells, vessel linings, scrubber trays, seawater cooling tanks
2. Heat exchanger baffles, flue gas assemblies, furnace shrouds and radiation shields
3. Sheet metal parts for bending, stamping and rolling
4. Strip: bellow blanks, gasket blanks, feed coil for continuous stamping

Available supply forms: hot rolled plate, cold rolled sheet, slit strip. Key concerns include thickness tolerance, flatness, edge burrs and internal laminations. Selection Tip: Cold worked sheet and strip gain hardness rapidly. Solution annealed material is preferred for bending and forming. Matching filler metal and controlled heat input are required for welding thick plates.

Service Condition Matching Table

Delivery Condition Selection (Frequently Overlooked in POs)

ASTM B166 and ASTM B168 permit multiple heat treatment conditions, which directly govern mechanical performance, formability and corrosion resistance.

1. Solution Annealed (Preferred Default) Soaked at 925–1150°C followed by rapid cooling. Homogeneous microstructure, low residual stress, optimal ductility. The primary choice for most corrosion and high-temperature equipment requiring welding or complex machining.
2. Cold Worked (Cold Drawn / Cold Rolled) Higher strength and hardness with reduced elongation. Only for simple structural parts requiring high strength without bending or welding. Not recommended for corrosion-sensitive service.
3. Hot Finished Cost-effective with heavy mill scale and loose tolerances. Suitable for rough machining blanks and non-visual internal load-bearing parts.

Procurement Reminder: Clearly specify heat treatment status in technical agreements. Although many suppliers default to solution annealed Alloy 600, formal written confirmation is mandatory for critical projects.

Inspection & Acceptance Items per ASTM B166 / ASTM B168

Mandatory Tests:

• Ladle chemical analysis + product check (permissible deviations following ASTM B880)
• Room temperature tensile test (UTS, YS, Elongation)
• Hardness test (HRB / HRC)
• Dimensional and geometric inspection (straightness, flatness, camber, edge condition)
• Visual surface inspection: cracks, laps, seams, scratches and inclusions

Optional Recommended Tests for High-End, Export & Engineering Projects:

• PMI positive material identification for incoming stock to prevent mix-up
• UT ultrasonic testing for internal defects of thick plates and large diameter bars
• PT liquid penetrant testing for surface discontinuities (especially for weld zones)
• Grain size determination
• Bend test for sheet and wire forming validation
• Third-party laboratory test reports (SGS, BV, etc.)

Common Selection Risks & Pitfalls

1. Standard Mismatch: Plate orders referenced to ASTM B166 or bar orders referenced to ASTM B168 will lead to non-compliant sampling, tolerance disputes and third-party rejection.
2. Grade Confusion between Alloy 600 / 601 / 625: Alloy 601 features aluminum addition for superior oxidation resistance; Alloy 625 with Mo and Nb delivers better pitting and reducing acid resistance. Direct substitution is not allowed.
3. Corrosion Risk of Cold Worked Material: Residual stress from cold working degrades the SCC resistance of Alloy 600. Cold drawn / cold rolled hardened material shall not be used for corrosion applications.
4. Improper Welding Consumables: ERNiCr-3 matching filler metal is required for Alloy 600 welding. Stainless steel filler will cause premature weld corrosion failure.
5. Misjudged Service Media: Alloy 600 resists chloride SCC but is vulnerable to fluoride, wet chlorine and strong reducing acids. Corrosion coupon testing is suggested for complex mixed media.

RFQ Technical Checklist for Buyers

Product: Alloy 600 / UNS N06600 Standard: ☐ ASTM B166 (Bar, Flat, Wire) ☐ ASTM B168 (Plate, Sheet, Strip) Dimension: Size, thickness / diameter, tolerance, length, slitting requirement Delivery Condition: Solution Annealed / Hot Finished / Cold Worked Surface Finish: Black / Ground / Pickled / Polished Test Requirement: Mill Test Certificate (MTC), PMI, UT / PT, Tensile & Hardness, Grain Size, Third-Party Witness Application: Medium, operating temperature, corrosion environment, welding / forming requirement Quantity, Packing, Inspection & Acceptance Criteria

Quick Decision Summary

Define medium, temperature and corrosion risk → Identify component geometry (shaft / pin / fixture → ASTM B166; lining, shell, formed sheet → ASTM B168) → Select solution annealed condition as priority → Confirm inspection scope → Issue purchase specification with correct ASTM reference.

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