Forged corrosion resistant nickel alloy Inconel 600 round bar for high temperature service
INCONEL® (nickel-chromium-iron) alloy 600 (UNS N06600/W.Nr. 2.4816) is a standard engineering material for applications which require resistance to corrosion and heat. The alloy also has excellent mechanical properties and presents the desirable combination of high strength and good workability.
The limiting chemical composition of INCONEL alloy 600 is shown in Table 1. The high nickel content gives the alloy resistance to corrosion by many organic and inorganic compounds and also makes it virtually immune to chloride-ion stress-corrosion cracking. Chromium confers resistance to sulfur compounds and also provides resistance to oxidizing conditions at high temperatures or in corrosive solutions. The alloy is not precipitation hardenable; it is hardened and strengthened only by cold work.
The versatility of INCONEL alloy 600 has led to its use in a variety of applications involving
temperatures from cryogenic to above 2000°F (1095°C).
The alloy is used extensively in the chemical industry for its strength and corrosion resistance. Applications include heaters, stills, bubble towers and condensers for processing of fatty acids; evaporator tubes, tube sheets and flaking trays for the manufacture of sodium sulfide; and equipment for handling abietic acid in the manufacture of paper pulp.
The alloy's strength and oxidation resistance at high temperatures make it useful for many applications in the heat-treating industry. It is used for retorts, muffles, roller hearths and other furnace components and for heat-treating baskets and trays.
In the aeronautical field, INCONEL alloy 600 is used for a variety of engine and airframe components which must withstand high temperatures. Examples are lockwire, exhaust liners and turbine seals.
INCONEL alloy 600 is used in the electronic field for such parts as cathode-ray tube spiders, thyratron grids, tube support members and springs.
The alloy is a standard material of construction for nuclear reactors. It has excellent resistance to corrosion by high-purity water, and no indication of chloride-ion stress-corrosion cracking in reactor water systems has been detected. For nuclear applications, the alloy is produced to exacting specifications and is designated INCONEL alloy 600T.
Chemical composition, %
Nickel (plus Cobalt)....................................................72.0 min.
Chromium..................................................................14.0-17.0
Iron ..........................................................................6.00-10.00
Carbon ......................................................................0.15 max.
Manganese ................................................................1.00 max
Sulfur.......................................................................0.015 max.
Silicon .......................................................................0.50 max.
Copper......................................................................0.50 max.
Corrosion resistance
The composition of INCONEL alloy 600 enables it to resist a variety of corrosives. The chromium content of the alloy makes it superior to commercially pure nickel under oxidizing conditions, and its high nickel content enables it to retain considerable resistance under reducing conditions. The nickel content also provides excellent resistance to alkaline solutions.
The alloy has fair resistance to strongly oxidizing acid solutions. However, the oxidizing effect of dissolved air alone is not sufficient to insure complete passivity and freedom from attack by air-saturated mineral acids and certain concentrated organic acids.
Stress-corrosion cracking
Austenitic chromium-nickel stainless steels sometimes fail catastrophically by stress-corrosion cracking. This type of failure is generally associated with an environment containing chlorides as well as with stress, water, dissolved oxygen, and other factors. The tendency of austenitic alloys to crack transgranularly in chloride solutions decreases as the nickel content of the alloy is increased. INCONEL alloy 600, with a minimum nickel content of 72%, is virtually immune to chloride-ion stress corrosion cracking.
INCONEL alloy 600 is subject to stress-corrosion cracking in high-temperature, high-strength caustic alkalies. Material for such service should be fully stress-relieved at 1650°F/1 hr or 1450°F/4 hr (900°C/1 hr or 790°C/4 hr) prior to use, and operating stresses should be kept to a minimum.
Stress-corrosion cracking may occur also in the presence of mercury at elevated temperatures. The recommendations given for caustic-alkali service should be followed if the alloy is used in an application which involves contact with mercury at high temperatures.
Microstructure
INCONEL alloy 600 is a stable, austenitic solid-solution alloy. The only precipitated phases present in the microstructure are titanium nitrides, titanium carbides (or solutions of those two compounds commonly called cyanonitrides), and chromium carbides.
Titanium nitrides and carbides are visible in polished microspecimens at magnifications of 50X or greater. They appear as small, randomly dispersed, angular-shaped inclusions. The color varies from orange-yellow for the nitride to gray-lavender for the carbide. These nitrides and cyanonitrides are stable at all temperatures below the melting point and are unaffected by heat treatment.
At temperatures between 1000° and 1800°F (540° and 980°C), chromium carbides precipitate out of the solid solution. Precipitation occurs both at the grain boundaries and in the matrix. Because of the grain-boundary precipitation, the corrosion behavior of INCONEL alloy 600 is similar to that of other austenitic alloys in that the material can be made susceptible to intergranular attack in some aggressive media (sensitized) by exposure to temperatures of 1000° to 1400°F (540° to 760°C). At temperatures above 1400°F (760°C) the predominant carbide is Cr7C3. Below 1400°F (760°C) the Cr23C6 carbide is also present.
High-temperature applications
INCONEL alloy 600 is widely used in the furnace and heat treating fields for retorts, boxes, muffles, wire belts, roller hearths, and similar parts which require resistance to oxidation and to furnace atmospheres. The alloy is the standard material for nitriding containers because of its resistance to nitrogen at high temperatures.
INCONEL alloy 600 has good resistance to carburization.
INCONEL alloy 600 resists attack by sulfur compounds at moderate temperatures, but it is subject to sulfidation in high-temperature, sulfur-containing environments. Molybdenum disulfide, a lubricant sometimes used to aid parts assembly, should not be used if the material will be subsequently exposed to temperatures above 800°F (427°C).
Working instructions
INCONEL alloy 600 is readily fabricated by either hot or cold working and can be joined by standard welding, brazing, and soldering processes. Although the alloy can be hardened and strengthened only by cold work, a wide range of mechanical properties can be obtained in finished parts by combining cold work and thermal treatments.
Heat treatment
The behavior of the alloy during heating is governed by a number of interacting variables: amount of cold work, grain size, chemical composition, and dimensions of the material. Consequently, times and temperatures for heat treatment are usually experimentally determined.
In general, an annealing treatment of about 1850°F/15 min (1010°C/15 min) will produce soft material. Brief exposure to 1900°F (1040°C) will give soft material without producing a coarse grain structure. Grain growth does not occur until the alloy is heated to about 1800°F (980°C). At that temperature, the finely dispersed carbide particles in the alloy’s microstructure, which inhibit grain growth, begin to coalesce. Solution of the carbides begins at about 1900°F (1040°C). Treatment for 1 to 2 hr at 2000° to 2100°F (1090° to 1150°C) dissolves the carbides completely and results in increased grain size. This solution treatment is beneficial in obtaining maximum creep and rupture strength.
In general, material with a fine grain structure is preferred because it has better corrosion resistance and higher tensile, fatigue and impact strength. Fine-grain material is preferred for all low-temperature applications, most intermediate temperature applications, and those high temperature applications which require resistance to shock and corrosion.
Grain size is dependent on processing. Hot-rolled products will usually have a small grain size because they are finished at relatively low temperatures. Annealing has little effect on the grain size of hot-rolled material. Cold-drawn or cold rolled material, in either the cold-worked or annealed condition, will have a small grain size. Solution treatment will produce a coarse grain structure in either hot-worked or cold-worked material.
The time and temperatures required for recrystallization of cold-worked material vary widely, depending on the amount of cold work and the specific composition.
Hot and cold forming
The normal hot-working temperature range for INCONEL alloy 600 is 1600° to 2250°F (870° to 1230°C). Heavy hot work should be done between 1900° and 2250°F (1040° and 1230°C); light work can be continued down to 1600°F (870°C). The alloy has low ductility at temperatures between 1200° and 1600°F (650° and 870°C) and should not be worked in that range. High tensile properties can be developed in the material by careful working at temperatures below 1200°F (650°C).
Machining
INCONEL alloy 600 is slightly more machinable than Type 304 stainless steel and slightly less machinable than Type 303 free-machining stainless steel.
The alloy is best handled on heavy-duty equipment using cutting tools large and heavy enough to withstand the loads and to quickly dissipate the heat generated. Tools must be sharp and have the proper geometry.
Available products and specifications
INCONEL alloy 600 is designated as UNS N06600 and Werkstoff Number 2.4816. The alloy is approved under the Boiler and Pressure Vessel Code of the American Society of Mechanical Engineers. It is approved under Section I (Power Boilers), Section III (Nuclear Vessels), and Section VIII (Pressure Vessels). Allowable design stresses are found in Section II, Part D. Section I coverage is provided by Code Case 1827.
Standard product forms are pipe, tube, round bar, flat bar, forging. The products are available in a wide range of sizes. Full information is available from the offices listed on the back cover.
Rod, Bar, and Forging - ASTM B 166/ASME SB 166, ASTM B 564/ASME SB 564, ASME Code Cases 1827 and N-253, SAE/AMS 5665 and 5687, BS 3075NA14 and 3076NA14, DIN 17752, 17753 and 17754, ISO 9723, 9724, and 9725, MIL-DTL-23229, QQ-W-390.
Pipe and Tube - ASTM B 167/ASME SB 167, ASTM B 163/ASME SB 163, ASTM B 516/ASME SB 516, ASTM B 517/ASME SB 517, ASTM B 751/ASME SB 751, ASTM B 775/ASME SB 775, ASTM B 829/ASME SB 829, ASME Code Cases 1827, N-20, N-253, and N-576, SAE/AMS 5580, DIN 17751, ISO 6207, MIL-DTL-23227
Product size range
Diameter: 100mm - 600mm
Length: on request
Production Process
