Alloy 690
Material
Alloy 690, UNS N06690, W.Nr.2.4642
Overview
Alloy 690 is a high-chromium-nickel alloy having excellent resistance to many corrosive aqueous media and high-temperature atmospheres, which is particularly suitable for use in oxidising media. In addition to its corrosion resistance, alloy 690 has high strength, good metallurgical stability, and favorable fabrication characteristics. The substantial chromium content gives the alloy outstanding resistance to oxidizing chemicals and to high temperature oxidizing gases. The high level of nickel imparts resistance to stress-corrosion cracking in chloride-containing environments as well as to sodium hydroxide solutions.
Character
Alloy 690 is characterised by
- ◎ Very good resistance to fluoride containing hot nitric acid
- ◎ Good resistance to stress corrosion cracking caused by alkalis
- ◎ Excellent resistance to stress corrosion cracking caused by media containing chloride and polythionic acids
- ◎ Excellent resistance to many aggressive aqueous media or in the primary and secondary loops of nuclear reactors
- ◎ Good resistance to oxidation, sulphidation and metal dusting in hot gases
- ◎ Good mechanical properties at room temperature and high temperature, paired with high ductility.
Application
The properties of alloy 690 are useful for various applications involving nitric or nitric / hydrofluoric acid solutions. Examples are tail-gas reheaters used in nitric acid production and heating coils and tanks for nitric/hydrofluoric solutions used in pickling of stainless steels and reprocessing of nuclear fuels.
The alloy’s resistance to sulfur-containing gases makes it an attractive material for such applications as coal gasification units, burners and ducts for processing sulfuric acid, furnaces for petrochemical processing, recuperators, incinerators, and glass vitrification equipment for radioactive waste disposal.
In various types of high-temperature water, alloy 690 displays low corrosion rates and excellent resistance to stress corrosion cracking. Thus, alloy 690 is widely used for steam generator tubes, baffles, tube sheets, and hardware in nuclear power generation.
Chemical composition
| Material | Fe | Ni | Cu | Cr | Mn |
|---|---|---|---|---|---|
| Alloy 690 | 7.0-11.0 | ≥58.0 | ≤0.50 | 27.0-31.0 | ≤0.5 |
| Material | C | Si | Co | S | P |
| Alloy 690 | ≤0.05 | ≤0.50 | ≤0.10 | ≤0.015 | ≤0.020 |
Mechanical property
Alloy 690 in annealed condition as per ASTM B163
| Material | Tensile strength ksi (MPa) |
Yield strength at 0.2 offset ksi (MPa) |
Elongation in 2” % min. |
|---|---|---|---|
| Alloy 690 | ≥85 (586) | ≥35 (241) | ≥30 |
Corrosion resistance
Alloy 690 has excellent resistance to corrosion in a broad range of aqueous and high temperature environments. Because of its high chromium content, the alloy is particularly resistant to oxidizing conditions. Alloy 690 also offers excellent resistance to attack by sulfur at high temperatures.
Available Process
Cold worked and bright annealed
Cold worked, bright annealed, polished (MP, EP etc.)
Common Tests
- ◎ Chemical composition
- ◎ Tension
- ◎ Hardness
- ◎ Flaring
- ◎ Flange
- ◎ Flattening
- ◎ Micro structure
- ◎ Hydrostatic
- ◎ NDT
- ◎ Intergranular Corrosion
- ◎ Surface condition
- ◎ Shape and dimension
- ◎ Positive Material Identification
Product forms
Capillary tube
- ◎ OD 0.30 ~ 3.0 mm
- ◎ WT 0.05 ~ 0.5 mm
Precision seamless tube
- ◎ OD 3.0 ~ 89 mm
- ◎ WT 0.10 ~ 10.0 mm
HP / UHP BA+ tube
- ◎ OD 3.0 ~ 76 mm
- ◎ WT 0.10 ~ 10.0 mm
Service
- ◎ Precision cutting
- ◎ Tube surface treatment, like ID surface super mirror polishing, best level could reach Ra0.0015um
- ◎ Tube deep processing, like coiling, bending, end forming, body forming, laser processing, various needles processing, built to drawing and sample, etc.