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Alloy800HT Corrosion Resistant High-Temperature Alloy Flanges for Oil and Gas Applications

Product Summary
Alloy 800HT forged flanges offer superior high-temperature strength, creep resistance, and corrosion/oxidation resistance for demanding oil & gas applications. With controlled carbon (0.06-0.10%), aluminum, and titanium content per ASTM B564 UNS N08811, these nickel-iron-chromium alloy flanges ensure long-term stability in furnaces, petrochemical plants, and power generation.

Product Details

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Corrosion Resistant Alloy Flanges

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High-Temperature Blind Pipe Flanges

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Oil and Gas Forged Flanges

Product Description
Alloy 800HT Corrosion Resistant Alloy Flanges for Oil and Gas Applications
Alloy 800HT (often written as Alloy 800H/800HT) is a high-temperature nickel-iron-chromium alloy used for forged flanges, pipes, fittings, and other components in heat-resistant and corrosion-resistant applications such as furnaces, petrochemical plants, and power generation.
Chemical Composition
When you see "Alloy 800HT forged flanges," the base material is the same alloy as in plate, pipe, or bar form. The chemical composition is governed by standards such as ASTM B564 (for forgings) and UNS N08811 (for 800HT).
Element Composition Range Function
Nickel (Ni) 30.0 – 35.0% Main austenite former providing excellent high-temperature strength and resistance to oxidation and carburization
Chromium (Cr) 19.0 – 23.0% Responsible for corrosion and oxidation resistance, forming a stable protective oxide layer at high temperatures
Iron (Fe) Balance Makes up the remainder of the alloy and helps control cost and mechanical properties
Carbon (C) 0.06 – 0.10% Compared with basic Alloy 800, 800HT has tighter controlled and slightly higher carbon content to improve creep and stress-rupture strength at elevated temperatures
Aluminum (Al) 0.25 – 0.60% Forms gamma prime precipitates with titanium to enhance high-temperature strength and structural stability
Titanium (Ti) 0.25 – 0.60% Forms gamma prime precipitates with aluminum to enhance high-temperature strength and structural stability
Manganese (Mn) ≤ 1.5% max Acts as a deoxidizer and improves hot working characteristics
Silicon (Si) ≤ 1.0% max Deoxidizer that improves oxidation resistance while avoiding embrittlement
Sulfur (S) ≤ 0.015% max Tightly restricted impurity element
Phosphorus (P) ≤ 0.030–0.035% max Tightly restricted impurity element
Copper (Cu) ≤ 0.75% max Typically present as a residual element
Key Characteristics for Forged Flanges
  • Consistent Chemistry: Forged flanges made to ASTM B564 UNS N08811 follow the same composition limits as bars and other forgings. The main difference lies in processing (hot working plus solution annealing and controlled grain size).
  • Controlled Elements: For 800HT, the "HT" designation means tighter control of Carbon, Aluminum, and Titanium to optimize creep strength and long-term stability at high temperatures.
  • High-Temperature Performance: 800HT is preferred over plain Alloy 800 for critical high-temperature flanges due to its superior performance characteristics.
Quality Assurance
Different codes and standards (ASTM B564, ASME SB-564, API, etc.) may have slightly different limits or additional notes. For real projects, always refer to:
  • The purchase specification and drawing
  • The applicable material standard (ASTM/ASME)
  • The Material Test Certificate (MTC) from the mill or forging shop, which lists the actual heat analysis for that batch of flanges
Summary: Alloy 800HT forged flanges are made from a nickel-iron-chromium alloy with approximately 30–35% Ni, 19–23% Cr, Fe as balance, moderately higher and controlled Carbon (0.06–0.10%), and carefully controlled Aluminum and Titanium (each about 0.25–0.60%). This specific chemistry delivers excellent high-temperature strength, creep resistance, and oxidation/corrosion resistance, making it ideal for forged flanges operating in demanding service conditions.
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