UNS N06690 Inconel Round Bars

Product Description

UNS N06690 (famously known as Inconel 690 / DIN 2.4642) is a high-chromium nickel alloy specifically engineered to deliver exceptional resistance to high-temperature corrosion and oxidizing aqueous environments.

While Inconel 718 relies on high strength via precipitation aging, Inconel 690 is essentially a solid-solution strengthened alloy designed primarily to survive where other alloys succumb to severe stress-corrosion cracking (SCC) or high-temperature sulfidation.

The Defining Feature: Ultra-High Chromium

The key differentiator for UNS N06690 is its massive 27% to 31% Chromium content (roughly double that of Inconel 600 or 713C). This creates a highly stable, self-healing chromium oxide film on the round bar's surface, providing unmatched protection against oxidizing chemicals, hot nitric acid environments, and sulfur-bearing gases.

Chemical Composition (Weight %)

• Nickel (Ni): 58.0% Minimum (Provides immunity to chloride-induced stress-corrosion cracking)

• Chromium (Cr): 27.0 31.0% (Protects against high-temp oxidation and sulfidation)

• Iron (Fe): 7.0 11.0%

• Carbon (C): 0.05% Maximum

• Silicon (Si): 0.50% Maximum

• Manganese (Mn): 0.50% Maximum

Supply Specifications & Standards for Round Bars

UNS N06690 round bars are produced via hot-rolling, cold-drawing, or forging, typically supplied in the annealed condition since the alloy cannot be hardened by heat treatment.

• Standard Specifications: ASTM B166, ASME SB166 (Rods and Bars), ASTM B564 / ASME SB564 (Forgings)

• Common Size Scope: Diameters ranging from 5 mm up to 350 mm.

• Available Finishes: Black hot-rolled, peeled/rough turned, or high-accuracy centerless bright ground.

Mechanical & Physical Properties (Typical Annealed Values)

• Density: $8.19 \text{ g/cm}^3$ ($0.296 \text{ lb/in}^3$)

• Melting Range: 1343C 1377C (2450F 2510F)

• Tensile Strength: $\ge$ 585 MPa (85 ksi)

• Yield Strength (0.2% Offset): $\ge$ 240 MPa (35 ksi)

• Elongation: $\ge$ 30% (Retains fantastic ductility and impact toughness even at cryogenic scales)

Primary Industrial Applications

Because it resists degradation in highly aggressive, high-temperature water environments, UNS N06690 round bars are heavily utilized for:

• Nuclear Power Generation: Fabricating steam generator tubesheets, structural baffles, and nuclear hardware.

• Chemical Processing: Heating coils, tank components, and tail-gas reheaters exposed to nitric/hydrofluoric acid pickling solutions.

• Waste Management: Glass vitrification equipment used to securely dispose of radioactive waste.

• Petrochemical & Gasification: Coal-gasification internals, incinerators, and sulfur-processing burner ducts.

Fabrication & Welding Checklist

• Machining: Like most high-nickel alloys, it work-hardens rapidly. Use slow cutting speeds, continuous positive feeds to stay below the work-hardened zone, and rigid tool geometry.

• Welding: Excellent overall weldability compared to 713C or 718. It is typically welded using matching high-chromium consumables to preserve corrosion integrity, specifically Inconel Filler Metal 52 (AWS A5.14 / ERNiCrFe-7) or Welding Electrode 152 (AWS A5.11 / ENiCrFe-7).