Material number: Incoloy? 825 nickel-base alloy

American brand: UNS N08825

German brand:? W . N r.2.4858

China brand: NS 142

Overview and properties of 1.Incoloy825(N08825, 2.4858) nickel-based alloy;

1 and Incoloy825(N08825, 2.4858) alloys are titanium-stabilized austenitic nickel-iron-chromium alloys, and copper and molybdenum are also added.

Incoloy825 has the following characteristics:

(1), good stress corrosion cracking resistance.

(2) Good pitting and crevice corrosion resistance.

(3) Good oxidation resistance and non-oxidizing thermal acidity.

(4) It has good mechanical properties at room temperature and high temperature up to 550℃

(5) Certification of pressure vessels with manufacturing temperature of 450℃

2. Chemical composition of 2.Incoloy825(N08825, 2.4858) alloy: See table-1?

3. Physical properties of 3.Incoloy825(N08825, 2.4858) alloy:

(1), density: ρ=8. 1g/cm3.

(2) Melting temperature range: 1370 ~ 1400℃?

4. Mechanical properties of 4.Incoloy825(N08825, 2.4858) alloy:

The properties listed in the following table are applicable to Incoloy825 alloy products with specific specifications after softening annealing (stabilization annealing). Special properties of non-standard size materials can be provided according to the requirements of specific applications.

(1), mechanical properties at room temperature (minimum):

5. Conditional stress value of 5.Incoloy825(N08825, 2.4858) alloy:

The high conditional stress value of 90% yield strength can be applied to applications that allow slightly larger deformation. Permanent stress caused by these stresses will lead to dimensional changes, so it is not recommended for flange and gasket connectors.

6. Metallographic structure of 6.Incoloy825(N08825, 2.4858) alloy:

Incoloy825 alloy has stable face-centered cubic structure. Chemical composition and proper heat treatment ensure that corrosion resistance will not be weakened by sensitization.

7. Corrosion resistance of 7.Incoloy825(N08825, 2.4858) alloy:

Incoloy825 is a general engineering alloy, which is resistant to acid and alkali metal corrosion in both oxidation and reduction environments. The high nickel content makes the alloy have effective stress corrosion cracking resistance. It has good corrosion resistance in various media, such as sulfuric acid, phosphoric acid, nitric acid and organic acid, and alkali metals such as sodium hydroxide, potassium hydroxide and hydrochloric acid solution. The high comprehensive performance of Incoloy825 is shown in the nuclear combustion dissolver with various corrosive media, such as sulfuric acid, nitric acid and sodium hydroxide, which are all treated in the same equipment.

Second, Incoloy825(N08825, 2.4858) alloy application scope:

Incoloy825 is widely used in various industrial fields where the service temperature does not exceed 550℃. Typical applications include:

1, heating pipes, containers, baskets and chains used in sulfuric acid pickling plants.

2. Seawater cooling heat exchanger, seafood pipeline system and acid gas environment pipeline.

3. Heat exchangers, evaporators, washing and dipping pipes in phosphoric acid production.

4. Air heat exchanger in petroleum refining.

5. Food engineering.

6. Chemical process.

7. Flame retardant alloy for hyperbaric oxygen application. ?

Third, Incoloy825(N08825, 2.4858) alloy processing and heat treatment:

Incoloy825 alloy is easy to be processed in general industrial processes.

Preheating of 1 and Incoloy825(N08825, 2.4858) alloys;

Temperature control is very important to ensure that the corrosion resistance of the alloy will not be weakened by sensitization. Before and during heating, the surface of the workpiece must be cleaned to keep the surface clean. If the heating environment contains sulfur, phosphorus, lead or other low melting point metals, the Nicrofer 6023/6023H alloy will become brittle. Impurities come from marking paint, chalk, lubricating oil, water, fuel oil, etc. The sulfur content of fuel should be low, such as the impurity content of liquefied gas and natural gas should be lower than 0. 1%, the sulfur content of city gas should be lower than 0.25g/m3, and the sulfur content of liquefied petroleum gas should be lower than 0.5%.

Heat treatment is best carried out in vacuum resistance furnace or inert gas protective atmosphere, because it can accurately control the temperature and is not polluted by impurities. If the impurity content of fuel gas is low, the fuel gas heating furnace can also be considered, so that a neutral or weakly oxidizing atmosphere can be obtained. The fluctuation of furnace gas composition during oxidation and reduction should be avoided, and the combustion flame cannot burn directly on the workpiece.

2. Hot working of 2.Incoloy825(N08825, 2.4858) alloy:

The suitable hot working temperature of Incoloy825 alloy is 1 150-900℃, and the cooling mode can be water quenching or rapid air cooling. In the hot working process, the workpiece can be directly sent to the heating furnace. After the furnace reaches the temperature, the heat preservation time of the material is 60 minutes per 100mm thickness. After keeping the temperature for a certain time, it is taken out of the furnace immediately and processed within a certain temperature range. If the temperature of the metal drops below the minimum processing temperature, it should be heated again. After hot working, it should be annealed in time to ensure the best corrosion resistance and suitable crystal structure.

3. Cold working of 3.Incoloy825(N08825, 2.4858) alloy:

Cold working should be carried out after solution treatment. The work hardening rate of Incoloy825 is close to that of austenitic stainless steel, so the processing equipment should be adjusted accordingly. There should be an intermediate annealing process when the cold work is large. When the final cold deformation is greater than 15%, the final stabilization treatment is needed.

4, Incoloy825(N08825, 2.4858) alloy heat treatment:

The temperature range of softening annealing or stabilization treatment is 920-980℃, and the most suitable temperature is 940+10℃. For workpieces with a thickness greater than 1.5mm, it is suggested to adopt water quenching or rapid air cooling to obtain the maximum creep resistance. In any heat treatment process, attention should be paid to the above matters about keeping clean.

5. Grinding and pickling Incoloy825(N08825, 2.4858) alloy:

The oxide near the weld of Incoloy825 workpiece is more difficult to remove than stainless steel, so it needs to be polished with fine abrasive belt or grinding wheel. In order to keep the luster of metal, be very careful when grinding. Before pickling in the mixed acid of nitric acid and hydrofluoric acid, it is necessary to remove oxides with sandpaper or carry out salt bath pretreatment. Pay special attention to the curing time.

6. Processing Incoloy825(N08825, 2.4858) alloy:

Incoloy825 should be processed after solution treatment, and the work hardening of the material should be considered. Unlike austenitic stainless steel, low surface cutting speed and re-feeding are required.

Four, Incoloy825(N08825, 2.4858) alloy welding:

1, when welding nickel-based alloy, the following rules should be followed:

(1). Workplace: The workplace should be separated or far enough away from the carbon steel processing area, kept as clean as possible, provided with partitions and avoided ventilation between the two areas.

(2) Work clothes and auxiliary articles: clean fine-grained leather gloves and clean work clothes should be worn.

(3) Tools and mechanical equipment: Nickel-based alloy and nickel-chromium steel should have special tools, wire brushes should be made of stainless steel, and mechanical equipment such as scissors, punches and rolling mills should be covered with felt, cardboard or plastic paper to prevent iron and carbon metals from falling on the surface of the machine and sticking to the processed materials, causing corrosion. Remove scale, oil stain and traces, and clean the base metal and filler alloy (such as covered electrode) in the welding area with acetone. Be careful not to use trichloroethylene, tetrachloroethylene and carbon tetrachloride.

2.Incoloy825 edge preparation: It is best to use mechanical processing, such as turning, milling and planing, or plasma cutting. If the latter is used, the cutting edge (welding surface) must be polished clean and smooth, allowing fine grinding without overheating. The parent metal area about 25mm wide on both sides of the weld shall be polished until bright metal is exposed.

3.Incoloy825 groove angle: Compared with carbon steel, the physical properties of nickel-based alloy and special stainless steel are mainly low thermal conductivity and large expansion coefficient. These characteristics should be considered when preparing welding groove, including widening the bottom gap (1 ~ 3 mm). At the same time, due to the viscosity of molten metal, a large groove angle (60 ~ 70) should be used to offset the butt welding.

4.Incoloy825 Arc striking: Arc striking should not be carried out on the surface of the workpiece, but on the welding surface to prevent corrosion caused by the arc striking point.

5, Incoloy825 welding process:

(1) and Incoloy825 are suitable for welding the same material or other metals by any traditional welding process, such as tungsten inert gas welding, plasma arc welding, manual sub-arc welding, metal inert gas welding and metal inert gas welding, among which pulse arc welding is preferred. When manual arc welding is used, it is recommended to use shielding gas with a mixed composition of (Ar+He+H2+CO2).

(2) Incoloy825 shall be welded in an annealed state, and stains, dust and various traces shall be removed with a stainless steel wire brush. When welding the root of the weld, in order to obtain the best quality root weld, the operation must be very careful (argon gas 99.99), so that the weld will not produce oxide after the root weld. The color produced in the welding heat affected zone should be brushed off with a stainless steel brush when the welding zone is not cooled.

(3) Incoloy825 filler metal: covered electrode: ENiCrMo-3, welding wire: ERNiCrMo-3.

6, Incoloy825 welding parameters and influence (heat input):

The welding operation shall be carried out under the low heat input specified in the heat input table, and the surfacing process shall be adopted. The interlayer temperature shall not exceed 120℃, and the welding specifications must be observed. The heat input q is calculated according to the following formula:

7.Incoloy825 Post-welding treatment (pickling, oxide brushing and heat treatment): After welding, stainless steel wire should be brushed to remove oxide, that is, when the metal has not produced welding color, so that ideal surface quality can be obtained without pickling. Unless otherwise specified, pickling is usually the last process of welding. Please refer to the descaling and pickling section. No heat treatment is required before and after welding.

Heat input per unit length (guide value):

8. Variety specifications and supply status of Incoloy825:

1. Variety classification: Special alloy can produce various specifications of Incoloy825 seamless pipe, Incoloy825 steel plate, Incoloy825 round steel, Incoloy825 forgings, Incoloy825 flange, Incoloy825 ring, Incoloy825 welded pipe, Incoloy825 steel strip, Incoloy825 welding wire and supporting welding materials.

2, delivery status: seamless pipe: solid solution+acid white, the length can be determined; Plate: solid solution, pickling and trimming; Welded pipe: solid solution acid white +RT% flaw detection, forging: annealing+turning; Bar forging and rolling, surface polishing or turning; The strip is output after cold rolling, solution softening and descaling; The wire is delivered in the state of solution pickling, disc shape or straight bar, and the solution straight bar is finely polished.