A Comprehensive Guide to Nickel-based Alloy: Hastelloy G35 (UNS N06035)

What is Hastelloy G35?

Hastelloy G-35, named UNS N06035 or din 2.4643, is a nickel chromium molybdenum alloy designed to resist “wet process” phosphoric acid and is used in fertilizer production. Similar to Hastelloy G-30, Hastelloy G-35 alloy has good local corrosion resistance in the presence of chlorides, as this may be a problem beneath the deposits in the evaporator for concentrating “wet process” phosphoric acid. In addition, compared with stainless steel and nickel chromium iron alloy used in traditional “wet process” phosphoric acid, it is less susceptible to stress corrosion cracking caused by chloride ions.
Due to the high chromium content, Hastelloy G-35 is extremely resistant to other oxidizing acids (such as nitric acid) and mixtures containing nitric acid. Due to its considerable content of molybdenum, it has medium resistance to reducing acid, and, unlike other Ni Cr Mo alloys, it is very resistant to “caustic dealloying” in hot sodium hydroxide.

Hastelloy G35 Weld Neck Flanges

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 N06035 (B-3), N10276 (C-276), N06035 (C-22), N06455 (C-4) and N06035 (G-3)

Equivalent Grades of Hastelloy G35 (UNS N06035)

Trademarks	ASTM	UNS	DIN	W.Nr
Hastelloy G-35	Hastelloy G-35	N06035	NiCr33Mo8	2.4643

Chemical Composition of Hastelloy G35 (UNS N06035)

%	Ni	Cr	Fe	Mo	W	Co	C	Mn	Si	P	S	Cu	Nb+Ta
Min	balance	28	13	4	1.5							1	0.3
Max		31.5	17	6	4	5	0.03	1.5	0.8	0.04	0.02	2.4	1.5

Mechanical Properties & Physical Properties of Hastelloy G35 (UNS N06035)

Density, g/cm3	Melting Point, ℃	Tensile Strength, MPa	Yield Strength, MPa	Elongation,%	Thermal Conductivity, W/m.k	Specific Heat, J/kg.k
8.22	1332~1361	710	317	66	10	450

Weldability, Workability of Hastelloy G35 (UNS N06035)

The weldability of G-35 alloy is similar to that of C-276 alloy. To weld G-35 alloy, three processes are commonly used. For sheet welds and plate root passes, gas tungsten arc (GTAW) welding is favored. For plate welds, the gas metal arc (GMAW) process is preferred. For field welding, the shielded metal arc process, using coated electrodes, is favored. Submerged arc welding is not recommended as this process is characterized by high heat input to the base metal and slow cooling of the weld. To minimize the precipitation of second phases in regions affected by the heat of welding, a maximum interpass temperature of 93°C (200°F) is recommended for G-35 alloy. Also, welding of cold-worked materials is strongly discouraged, since they sensitize more quickly and induce residual stresses. A full solution anneal, followed by water quenching, is recommended for cold-worked structures, prior to welding. Hastelloy G-35 alloy can be hot forged, hot rolled, hot upset, hot extruded, and hot formed. However, it is more sensitive to strain and strain rates than the austenitic stainless steels, and the hot working temperature range is quite narrow. On the other hand, the referenced guideline of cold working is much stiffer than most austenitic stainless steels which means more energy is required during cold forming.

Forming of Hastelloy G35 (UNS N06035)

G-35 alloy has excellent forming characteristics, and cold forming is the preferred method of shaping. The alloy can be easily cold worked due to its good ductility. The alloy is generally stiffer than the austenitic stainless steels; therefore, more energy is required during cold forming.

Heat treatment of Hastelloy G35 (UNS N06035)

• Wrought forms of HASTELLOY G-35 alloy are furnished in the solution annealed condition, unless otherwise specified. The standard solution annealing treatment consists of heating to 1121°C (2050°F) followed by rapid air-cooling or water quenching. Parts which have been hot formed should be solution annealed prior to final fabrication or installation.

ASTM Specifications

Product Form	Standard
Sheet, Plate & Strip	ASTM B575
Billet, Rod & Bar	ASTM B574, B472
Coated Electrodes	ASTM A5.11
Bare Welding Rods & Wire	ASTM A5.14
Seamless Pipe & Tube	ASTM B622
Welded Pipe & Tube	ASTM B619, B626
Fittings	ASTM B366, B462
Forgings	ASTM B564, B462

*The mechanical properties vary according to different forms and heat treatment conditions.

Application areas of nickel-based alloy Hastelloy G35 (UNS N06035):

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.

ASTM B622 Hastelloy G35 seamless pipes

Hastelloy G35 is widely used in phosphoric acid equipment, sulfuric acid equipment, nitric acid equipment, nuclear fuel reprocessing, nuclear waste treatment, pickling operations, petrochemical products, fertilizer production, pesticide production, and gold mining extraction. Hastelloy G35 has excellent resistance to hydrofluoric acid/nitric acid mixtures used in applications such as stainless steel pickling. Compared with other nickel-based or iron-based alloys, Hastelloy G35 has excellent performance in commercial phosphoric acid Better resistance. Its application as an acid evaporator in the fertilizer industry is increasing day by day.
Comparison of corrosion resistance in commercial phosphoric acid: The corrosion resistance of Hastelloy G35 and G alloy and 625 alloy in commercial phosphoric acid is as follows. The corrosivity of commercial phosphoric acid is determined by many factors, including concentration and temperature. , Impurities and phosphate ore origin, etc. The corrosion rate of phosphoric acid of the same concentration made from different phosphate mineral sources may vary greatly. Therefore, the corrosion test is measured in different sources of phosphoric acid, and the corrosion resistance of G-30 alloy is expressed as a function of the corrosion rate of G alloy and 625 alloy, respectively. In the same acid with a corrosion rate of 0.025-2.5mm, the corrosion resistance of G-30 alloy is usually 2-10 times stronger than that of G alloy and 265 alloy. Some of the more common uses of Hastelloy G35 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.
• Flanges.
• Valves.

Variety specifications and supply status of Nickel-based super alloy: Hastelloy G35 (UNS N06035):

Variety classification:

Yaang Pipe Industry can produce various specifications of Hastelloy G35 seamless pipe, Hastelloy G35 steel plate, Hastelloy G35 round bar, Hastelloy G35 forgings, Hastelloy G35 flange, Hastelloy G35 pipe fittings, Hastelloy G35 welded pipe, Hastelloy G35 steel strip, Hastelloy G35 wire and supporting welding materials. 

Delivery status:

• 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.