Nickel-based super alloy: Hastelloy G3 (UNS N06985)
What is Hastelloy G3?
Hastelloy G3 (also known as “Alloy G3”) is designated UNS N06985 or DIN 2.4619 and is a nickel-chromium-iron alloy with added molybdenum and copper. It has good weldability and has the ability to resist intergranular corrosion under welding conditions. The low carbon content helps prevent sensitization of the welding heat-affected zone and subsequent intergranular corrosion. Hastelloy G3 is commonly used in flue gas scrubbers and processing reducing acids, such as phosphoric acid and sulfuric acid.
Hastelloy G3 is a nickel-based high-temperature alloy composed of nickel, chromium, molybdenum, cobalt and other elements, with a nickel content of about 44%. Hastelloy G3 alloy, referred to as G3, is a nickel-based corrosion-resistant alloy with superior performance. It belongs to the Ni-Cr-Fe series containing Mo and Cu. It has excellent resistance to oxidation, atmospheric corrosion and stress corrosion cracking, and has relatively High resistance to local corrosion (pitting corrosion, crevice corrosion). Due to the high content of Fe in the alloy, it has the characteristics of low cost compared to other nickel-based corrosion resistant alloys. G3 alloy is often used in flue gas desulfurization systems, papermaking, phosphoric acid production steam generators and heat exchangers. The oil well pipe made of this alloy has excellent resistance to H2S, CO2, Cl-corrosion, and is the best material for sour gas field oil well pipe.
Characteristics of Hastelloy G3 (UNS N06985)
- 1.Good resistance to heataffected-zone (HAZ) corrosion and weldability;
- 2.Excellent corrosion resistance to oxidizing chemicals and atmospheres;
- 3.Good resistance to reducing chemicals;
- 4.Exceptional stress-corrosion-cracking resistance in chloride-containing environments;
- 5.Good resistance to pitting and crevice corrosion.
- 6.Good resistance to intergranular corrosion.
Hastelloy G3 alloy is a nickel-based corrosion-resistant alloy with superior performance. Among the cold-work-strengthened nickel-based corrosion-resistant alloys, Hastelloy G3 alloy has better corrosion resistance than 825 and 028 alloys. Hastelloy G3 alloy has a temperature of 220°C, pH=3.3, and Cl ion concentration of 15.175%. H2S and CO: In a corrosive environment with a partial pressure of 2.1 MPa, it still shows good corrosion resistance.
In addition, the grain size of G-3 alloy affects its resistance to stress corrosion cracking and intergranular corrosion in simulated acidic solutions in the Gulf of Mexico (25%NaC!+1.03 MPaH2S+1.03 MPa C02, temperature is 218℃). Slow strain rate corrosion test results show that the reduction of area and elongation of G-3 alloy are greater than 92%, and no secondary cracks appear. G-3 alloy shows good resistance to stress corrosion cracking. When the grain size changes from grade 6-7.5 to grade 4-5.5, it has little effect on its resistance to stress corrosion cracking. The intergranular corrosion test shows that the corrosion rate of G-3 alloy is about 0.27～0.36 mm/a, which is significantly lower than the maximum allowable corrosion rate (0.61 mm/a) in the chemical process, and the grain size has little effect on the intergranular corrosion. , Thompson et al. studied the pitting corrosion behavior of G-3 alloy in an acidic solution with a C1 ion concentration of 100 g/L and a temperature of 50 ℃ by using the cyclic potential scanning method. The results show that the pitting potential of G-3 alloy is 0.59 V. When the potential exceeds this value, the corrosion current increases rapidly and the corrosion resistance is greatly reduced.
Production process of Hastelloy G3 alloy:
- 1. Hot rolled forming;
- 2. Hot extrusion molding.
G3 alloy has poor high-temperature plasticity, narrow hot forming temperature range, and greater resistance to deformation. At about 1150°C to 1220°C, the alloy has the best thermoplasticity. Therefore, the production of G-3 alloy pipes is mainly formed by hot extrusion. The thermal deformation of the blank in the extrusion cylinder is a key technology in hot extrusion molding, and it is also a bottleneck in the production of G-3 alloy pipes.
Types of Hastelloy
- Hastelloy B-3 nickel molybdenum alloy has excellent corrosion resistance in reducing environment
- The upgraded version of Hastelloy B-3: B-3 has excellent corrosion resistance to hydrochloric acid at any temperature and concentration
- Hastelloy C-4: good thermal stability, good toughness and corrosion resistance at 650-1040 ℃
- Hastelloy C-22: has better uniform corrosion resistance than C-4 and C-276 in oxidizing medium and excellent local corrosion resistance
- Hastelloy C-276: good resistance to oxidizing and moderate reducing corrosion, excellent resistance to stress corrosion
- Hastelloy C-2000: the most comprehensive corrosion resistant alloy with excellent uniform corrosion resistance in oxidation and reduction environments
- Hastelloy G-35: the upgraded product of G-30 has better corrosion resistance and thermal stability, and has excellent performance in phosphoric acid and other strong oxidizing mixed acid media with high chromium content
- Hastelloy X: combined with the characteristics of high strength, oxidation resistance and easy processing, each of the above grades has its own specific chemical composition, mechanical properties and strong points, so we can’t generalize the characteristics of Hastelloy.
Hastelloy alloy is mainly divided into three series B, C and G. it is mainly used in iron-based Cr Ni or Cr Ni Mo stainless steel, non-metallic materials and other occasions with strong corrosive medium.
In order to improve the corrosion resistance and cold and hot working properties of Hastelloy, three major improvements have been made to Hastelloy:
- Series B: B → B-3 (00ni70mo28) → B-3
- Series C: C → C-276 (00cr16mo16w4) → C-4 (00cr16mo16) → C-22 (00cr22mo13w3) → C-2000 (00cr20mo16)
- G Series: G → G-3 (00cr22ni48mo7cu) → G-30 (00cr30ni48mo7cu)
- The most widely used materials are N06985 (B-3), N10276 (C-276), N06985 (C-22), N06455 (C-4) and N06985 (G-3)
Chemical Composition of Hastelloy G3 (UNS N06985)
Physical Properties of Hastelloy G3 (UNS N06985)
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Mechanical Properties of Hastelloy G3 (UNS N06985)
Annealing of Hastelloy G3 (UNS N06985)
- Anneal at 2100 F and rapid air cool or water quench.
Forging of Hastelloy G3 (UNS N06985)
- Forge in the range of 2100 F to 1700 F and be sure to anneal after forging to restore corrosion resistance.
Cold Working of Hastelloy G3 (UNS N06985)
Cold forming may be done using standard tooling although plain carbon tool steels are not recommended for forming as they tend to produce galling. Soft die materials (bronze, zinc alloys, etc.) minimize galling and produce good finishes, but die life is somewhat short. For long production runs the alloy tool steels ( D-2, D-3) and high-speed steels (T-1, M-2, M-10) give good results especially if hard chromium plated to reduce galling. Tooling should be such as to allow for liberal clearances and radii. Heavy duty lubricants should be used to minimize galling in all forming operations. Bending of sheet or plate through 180 degrees is generally limited to a bend radius of 1 T for material up to 1/8″ thick and 2 T for material thicker than 1/8″. In order to avoid “orange peel” surface effect the cold work reduction of area should be greater than 15% at any given operation. Intermediate annealing may be done, to restore ductility, during the sequence of cold forming operations.
Machinability of Hastelloy G3 (UNS N06985)
Conventional machining techniques used for iron based alloys may be used. Machining characteristics are somewhat similar to those for the austenitic (300 Series) stainless steels. This alloy does work-harden during machining and has higher strength and “gumminess” not typical of steels. Heavy duty machining equipment and tooling should be used to minimize chatter or work-hardening of the alloy ahead of the cutting. Water-base coolants of premium quality are preferred. Rigid mounting of tooling and the workpiece are important to avoid “chatter” (work hardening ahead of the cut). Both carbide tools and high-speed tools may be used successfully. Carbide tooling generally permits twice, or better, the feed rate of high-speed tooling for the same depth of cut or drilling. Turning: For roughing cuts the tools should have -5 degree back rake for carbide and -10 degree back rake for high-speed steel. Normal and/or finish turning call for positive rake angles of about +10 degrees for both carbide and hig-speed cutters. Cutting speeds and feeds are in the following ranges: For High-Speed Steel Tools For Carbide Tooling Depth Surface Feed Depth Surface Feed of cut speed in inches of cut speed in inches inches feet/min. per rev. inches feet/min. per rev. 0.040″ 0.040″ 0.250″ 0.250″ Drilling: Steady feed rates must be used to avoid work hardening due to dwelling of the drill on the metal. Rigid set-ups are essential with as short a stub drill as feasible. Conventional high-speed steel drills work well. Feeds vary from 0.001 inch per rev. for holes of less than 1/16″ diameter, 0.002 to 0.003 inch per rev. for 1/4″ dia., 0.004 to 0.010 inch per rev. for holes of 7/8″diameter. Speeds of 10 to 25 surface feet/minute, are best for drilling. Milling: To obtain good accuracy and a smooth finish it is essential to have rigid machines and fixtures and sharp cutting tools. High-speed steel cutters such as M-2 or M-10 work best with cutting speeds of 30 to 50 surface feet per minute and feed of 0.002-0.007 inch per cutting tooth. Grinding: The alloy should be wet ground and aluminum oxide wheels or belts are preferred.
Welding of Hastelloy G3 (UNS N06985)
The commonly used welding methods work well with this alloy. Matching alloy filler metal should be used. If matching alloy is not available then the nearest alloy richer in the essential chemistry (Ni, Co, Cr, Mo) should be used. All weld beads should be slightly convex. It is not necessary to use preheating. Complete removal of slag is important after every weld pass and upon completion of welding. Usually this is accomplished by use of a wire brush (hand or powered). Surfaces to be welded must be clean and free from oil, paint or crayon marking. The cleaned area should extend at least 2″ beyond either side of a welded joint.
- Gas Tungsten Arc Welding (TIG): DC straight polarity (electrode negative) is recommended. Keep as short an arc length as possible and use care to keep the hot end of filler metal always within the protective atmosphere. Arc voltage should be in the range of 9 to 13 volts with current of 20-60 amps for thin material, 60-150 amps for material 1/8″ thick or so, and 100-150 amps for material 1/4″ thick.
- Shielded Metal-Arc Welding (SMAW): Electrodes should be kept in dry storage and if moisture has been picked up the electrodes should be baked at 600 F for one hour to insure dryness. Use electrode positive polarity. Current settings vary from 60 amps for 3/32″ dia. rods up to 180 amps for 3/16″ dia. rods. It is best to weave the electrode slightly as this alloy weld metal does not tend to spread.
- Metal-Arc Welding (MIG): Electrode positive polarity should be used and best results are obtained with the welding gun at 90 degrees to the joint. For Short-Circuiting-Transfer GMAW a typical voltage is 18-22 with a current of 75-150 amps and a wire feed of 8-10 inches per minute.
- Submerged-Arc Welding: Generally submerged-arc welding should be avoided. This weld process involves high heat input and may lead to cracking of the alloy workpiece.
Heat treatment of Hastelloy G3 (UNS N06985)
- The alloy may be annealed, but does not respond to age-hardening. It is normally furnished in the annealed condition. It is important to anneal after hot or cold working in order to restore optimum corrosion resistance.
Hardening of Hastelloy G3 (UNS N06985)
- Hardens due to cold working only.
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Application areas of nickel-based alloy Hastelloy G3 (UNS N06985):
G series nickel-based alloys (G3, G30, G35) are mainly used in the petrochemical industry such as oil well pipes, evaporators used in the production of wet phosphoric acid, nuclear fuel regeneration equipment in the nuclear industry, and pickling equipment in steel plants. C series alloys (C276, C22, C4) are one of the most used corrosion-resistant alloys, and they have good corrosion resistance in oxidizing or reducing environments. Therefore, it is widely used in various places with complex corrosive environments, such as the nuclear industry and the pharmaceutical industry. Alloy 690 is a very important nuclear material. It is an irreplaceable material for the steam pipe of nuclear power generation in nuclear power plants. It is a core component and has good resistance to stress corrosion cracking.
When drilling for oil and natural gas, in addition to drilling machinery and equipment, special pipes are also needed, namely drill strings, casings, tubing, etc., collectively referred to as “oil well pipes.” Oil well pipe accounts for about 40% of the total steel used in the oil and gas industry, and is an important part of oil and natural gas exploitation. According to the particularity of China’s oil and gas production environment, experts believe that ultra-high-strength tubing, high-strength tubing, tubing resistant to corrosion in acid environments, and special threaded tubing are high-performance tubing that China urgently needs today and in the future.
For a long time, China’s oil well pipe materials have mainly been 13Cr, 22Cr, 25Cr, 316 stainless steel and so on. These stainless steels have high strength and high Cr content. A dense cr2o3 passivation film is easily formed on the surface of the alloy, which can effectively resist the corrosion of CO, and with the increase of Cr content, it is resistant to CO2 corrosion. The ability to gradually increase oil. However, with the gradual discovery and exploitation of deeply buried high-acid oil and gas fields, the content of H2S, CO2, S, and C1 in the mining environment is high, and the commonly used stainless steel pipes can no longer meet the mining needs. Therefore, highly alloyed nickel-based corrosion-resistant alloys (600, 825, G-3, 2550, 050, 625, C276) are gradually used in oil well pipes. G3 alloy is a nickel-based corrosion-resistant alloy with superior performance. The Ni-Cr-Fe system containing Mo and Cu has excellent resistance to oxidation, atmospheric corrosion and stress corrosion cracking. Due to the high content of Fe in the alloy, it has the characteristics of low cost compared to other nickel-based corrosion resistant alloys. The oil well pipe made of this alloy has excellent resistance to H2S, CO2, and Cl corrosion, and is the best choice for oil well pipe in sour gas fields. With the gradual development of sour oil and gas fields, the demand for nickel-based alloy oil well pipes continues to rise. Related products have not been fully mastered by a few foreign manufacturers of nickel-based corrosion-resistant alloy pipe manufacturing technology, which seriously threatens the country’s energy security. Therefore, it is imperative to localize nickel-based alloy pipes.
Alloy G3 is an improved version of Alloy G. The alloy also has excellent corrosion resistance, but its resistance to HAz (heat affected zone) corrosion is stronger, and it has good weldability. The lower carbon content of the alloy can delay the precipitation kinetic behavior of carbides. And its slightly higher aluminum content provides excellent local corrosion resistance. G3 alloy has replaced G alloy in almost all industrial applications. At the same time, it replaces 825 alloy in many applications that require local corrosion resistance. Commonly used downhole tubing materials are 825, G3, G50, C276 and 028 alloys. According to the fluid properties of the high acid gas fields in the Sichuan-Chongqing area, the material must meet the following three requirements: high temperature resistance, high pressure resistance, and strong corrosion resistance.
It is used in flue gas desulfurization systems (scrubbers), especially in quencher, damper, and outlet ducting areas. It can be used in other air pollution control systems in the chemical and pulp and paper industries. It is a good candidate for evaporators, heatexchangers, tank liners, and other equipment in phosphoric acid manufacturing plants. Some of the more common uses of Hastelloy G3 include:
- Wire wound resistors.
- Bimetal contacts.
- Electric and electronic applications.
- Marine engineering.
- Chemical and hydrocarbon processing equipment.
- Gasoline and freshwater tanks.
- Crude petroleum stills.
- De-aerating heaters.
- Boiler feed water heaters and other heat exchangers.
- Pumps, shafts and fasteners.
- Industrial heat exchangers.
- Chlorinated solvents.
- Crude oil distillation towers.
- Meter and valve parts.
- Screw machine products.
- Oil refinery piping.
- Heat exchangers.
- Nuclear fuel production.
- Generator tubing.
- High temperature heating coils.
- Crude oil transfer piping.
- Propeller and pump shafts.
- Piping system.
- Heat exchange tubes.
- Pipe fittings.
Variety specifications and supply status of Nickel-based super alloy: Hastelloy G3 (UNS N06985):
Yaang Pipe Industry can produce various specifications of Hastelloy G3 seamless pipe, Hastelloy G3 steel plate, Hastelloy G3 round bar, Hastelloy G3 forgings, Hastelloy G3 flange, Hastelloy G3 pipe fittings, Hastelloy G3 welded pipe, Hastelloy G3 steel strip, Hastelloy G3 wire and supporting welding materials.
- Seamless pipe: solid solution + acid white, length can be set;
- Plate: solid solution, pickling, trimming;
- Welded pipe: solid solution acid white + RT% flaw detection;
- Forging: annealing + car polish; Bars are forged and rolled, surface polished or car polished;
- Strips are delivered after cold rolling, solid solution soft state, and deoxidized;
- Wire rods are finely ground in solid solution pickled disk or straight strips, solid solution straight strips Delivery in light state.
Source: China Hastelloy G3 Flanges Manufcturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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