Weldability of Incoloy 800H/800HT alloys
Weldability of Incoloy 800H/800HT alloys
Incoloy 800H/800HT alloys exhibit good to excellent weldability and can be easily welded using standard stainless steel welding techniques such as TIG (GTAW), MIG (GMAW), and shielded metal arc welding (SMAW), while maintaining high-temperature strength and creep resistance. However, welding requires inert gas shielding and appropriate filler materials (e.g., Inconel 82) to prevent contamination and ensure that the weld performance meets the requirements of the service environment. Key considerations include preventing weld pool contamination, using appropriate matching filler metals, and potentially requiring post-weld stress relief or annealing.
What is the composition of Inconel 800 alloy?
Inconel 800 is an alloy whose chemical composition primarily consists of nickel and chromium. Typically, this alloy contains more than 50% nickel. On the other hand, Incoloy 800 is an alloy primarily composed of nickel, iron, and chromium.
The welding methods commonly used are suitable for Alloy 800H/800HT alloys. A matching alloy filler metal should be used. If a matching alloy is unavailable, an alloy with the closest and highest content of chemical elements (nickel, cobalt, chromium, and molybdenum) should be used. All welds should be slightly convex. Preheating is not required. The surfaces to be welded must be clean and free of oil, paint, or crayon marks. The cleaned area should extend at least 2 inches on either side of the weld.
Chemical composition percentages of Incoloy 800H/800HT
| Grade | C | Al | Si | S | Ti | Cr | Mn | Fe | Ni | Cu |
| 800H | 0.05-0.10 max | 0.15-0.60 | 1.0 max | 0.015 max | 0.15-0.60 | 19.0-23.0 | 1.5 max | 39.5 min | 30.0-35.0 | 0.75 max |
| 800HT | 0.06-0.10 max | 0.15-0.60 | 1.0 max | 0.015 max | 0.15-0.60 | 19.0-23.0 | 1.5 max | 39.5 min | 30.0-35.0 | 0.75 max |
Gas Tungsten Arc Welding (GTAW): Direct current electrode negative (DCEN) is recommended. The shortest possible arc length should be maintained, and care should be taken to ensure that the hot end of the filler metal is always in a protective gas environment.
Shielded Metal Arc Welding (SMAW): Electrodes should be stored in a dry place, and if they become damp, they should be baked at 600°F for one hour to ensure dryness. Current settings range from 60 amps (for 0.062-inch thick material) to 140 amps (for 1/2-inch and thicker material). A slight weaving motion of the electrode is preferred, as the weld metal of this alloy does not spread easily. Slag removal is performed using a wire brush (manual or power-driven). All slag must be thoroughly removed before subsequent welding and after the final weld is completed.
Gas Metal Arc Welding (GMAW): Direct current reverse polarity should be used, and the best results are obtained when the welding gun is at a 90-degree angle to the weld. For short-circuit transfer GMAW, typical voltage is 20-23 volts, current is 110-130 amps, and wire feed speed is 250-275 inches per minute. For spray transfer GMAW, the voltage is 26-33 volts, the current range is 175-300 amps, and the wire feed speed is 200-350 inches per minute, depending on the filler wire diameter.
Submerged Arc Welding (SAW): The same matching filler metal as for GMAW should be used. For Alloy 800H/800HT alloys, either direct current positive or reverse polarity can be used. A convex weld bead is preferred.
Key Considerations:
Filler Metal: Use a compatible filler metal, such as INCONEL Filler Metal 82 (for gas shielded welding) or a matching welding rod, to maintain strength at high temperatures.
Protection: Inert gas (argon) shielding is crucial to prevent contamination and the formation of tightly adhering oxide scale.
Cleaning: Thorough wire brushing removes welding slag and oxides.
Heat Treatment: Preheating/post-heating is generally not required, but annealing after cold working or specific high-temperature treatments (2050-2150°F) can optimize performance.
High Strength: Due to its inherently high strength, more powerful welding equipment is required than for standard stainless steel.
Reasons for Welding:
Incoloy 800H/HT exhibits excellent resistance to carburization, oxidation, and nitridation at high temperatures, making it an ideal material for furnace components, heat exchangers, and petrochemical processing. Its good weldability ensures integrity under demanding conditions.
Why Choose Gnee as Your Nickel-Based Alloy Supplier
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All stainless steel products are packaged using the following methods:
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Gnee Steel is a supplier of incoloy 800/800H/800HT alloy, offering a wide range of products including: seamless pipe (sizes: 4-219 mm; thickness: 0.5-20 mm); welded pipe (sizes: 5.0-1219.2 mm; thickness: 0.5-20 mm); plates (thickness: 0.1 to 100 mm; width: 10-2500 mm); strips; alloy round bars (diameter: 3-800 mm); flat bars (thickness: 2-100 mm; width: 10-500 mm); hexagonal bars (size: 2-100 mm); wire rods; and extruded profiles. We collaborate with steel mills to provide our customers with incoloy 800/800H/800HT alloy products that meet or exceed numerous leading industry standards, including ASTM, ASME, SAE, AMS, ISO, DIN, EN, and BS standards.
Gnee Steel stocks and sells incoloy 800/800H/800HT, pipes, plates, strips, round bars, flat bars, forged billets, hexagonal steel, wire rods, and extruded profiles. Please feel free to contact us at ss@gneesteel.com for a quote.
