N06690 / W.Nr. 2.4642 Corrosion Resistant Alloys Good Metallurgical Stability

Corrosion resistant Alloy 690 (N06690, W.Nr. 2.4642) semi-products for chemical processing application

1 PRODUCT

Corrosion resistant Alloy 690 ( UNS N06690, W.Nr. 2.4642 ) semi-products for chemical processing application

Alloy 686 is available in the following product forms: pipe, tube, sheet, strip, plate, round and hexagonal bar, forging, forging stock, wire and wire rod in coil, and welding products.

Rod and bar

Delivery conditions: forged, rolled, drawn, thermally treated, oxidised, descaled or pickled, machined, peeled or ground

Sheet and plate

Delivery conditions: hot or cold rolled, thermally treated, descaled or pickled

Wire

Delivery conditions: bright drawn, ¼ hard to hard, bright annealed in rings, containers, on spools and spiders

Strip

Delivery conditions: cold rolled, thermally treated and pickled or bright annealed

Other shapes and dimensions such as circular blanks, rings, seamless tube and forgings can be requested.

2 EQUIVALENT DESIGNATION

UNS N06690, W.Nr.2.4642, NiCr29Fe (EN), NiCr29Fe9 (ISO), NC30Fe (AFNOR), NW6690 (ISO), Inconel® Alloy 690, VDM® Alloy 690, Nicrofer 6030

3 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, tubesheets, and hardware in nuclear power generation.

4 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.

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.

5 CHEMICAL COMPOSITION

6 PHYSICAL PROPERTIES

Density at room temperature: 0.296 lb/in³ (8.2 g/cm³)

Melting range: 2470-2506°F(1390-1410°C)

Specific heat: 0.107 Btu/lb-°F (450 J/kg-°C)

Electric resistivity: 691 ohm-circ mil/ft (1.148 uΩ-m)

Permeability at 200 oersted (15.9 kA/m): 1.0001

Young’s Modulus: 30.6 10³ ksi (211GPa)

Poisson’s Ratio: 0.289

7 METALLOGRAPHY

Alloy 690 has a cubic face-centred structure.

Alloy 690 is an austenitic, solid-solution alloy with a high degree of metallurgical stability. The alloy has a low solubility for carbon, and its microstructure normally contains carbides. The major carbide present in the alloy is M₂₃C₆; the abundance of the phase varies with carbon content and thermal exposure of the material. Other phases normally present are titanium nitrides and carbonitrides. No embrittling intermetallic phases such as sigma phase have been identified in alloy 690.

8 MECHANICAL PROPERTIES

Alloy 690 has high strength over a broad range of temperatures. Mechanical properties of the alloy vary with product form and temper. Alloy 690 is normally used in the annealed temper, and strength characteristics described below are representative of annealed material.

Minimum values at room temperatures in acc. w. ASTM B166 or 168

Minimum values at room temperatures in acc. w. ASTM B166 or 168 for various product forms, size ranges and processing status

9 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.

10 WORKING INSTRUCTION

Alloy 690 is readily fabricated by conventional techniques for high-nickel alloys. In most working operations, alloy 690 exhibits characteristics similar to those of alloy 600.

Hot forming

Alloy 690 can be hot worked at a temperature range of between 1230 and 900 °C (2250 and 1650 °F) with subsequent rapid cooling down in water or by using air nozzles.

The temperature range for heavy hot forming of alloy 690 is 1900 to 2250°F (1040 to 1230°C). Light forming can be done at temperatures down to 1600°F (870°C).

Cold forming

Cold working should be carried out on annealed material. Alloy 690 has a higher work hardening rate than austenitic stainless steels. This must be taken into account during design and selection of forming tools and equipment and during the planning of forming processes. Intermediate annealing may be necessary for high degrees of cold working deformation. Before use, heat treatment is required after cold working with more than 10 % deformation.

Heat treatment

Solution annealing should be carried out at temperatures between 1020 and 1070°C (1870 to 1960°F). If use in a high-temperature range with increased creep resistance is intended, the solution annealing temperature should be raised to between 1080 and 1150°C (1980 to 2100°F).

Machining

Alloy 690 should preferably be machined in the annealed condition. Since the material exhibits a considerable work hardening rate, low cutting speeds should be used and the tool should remain continuously in contact. An adequate cutting depth is important in order to cut below the previously formed work-hardened zone.

Optimum heat dissipation through the use of large quantities of suitable, preferably aqueous, lubricants has considerable influence on a stable machining process.

11 STANDARD SPECIFICATION

Rod, Bar, Wire and Forging

ASTM B166 / ASME SB 166

ASTM B 564 /ASME SB 564

ASME Code Case N-525

ISO 9723

MIL-DTL-24801

DIN 17742

DIN 17752

DIN 17750

DIN 17753 Wire

Seamless Pipe and Tube

ASTM B 163/ ASME SB 163

ASTM B 167

ASTM B 829 /ASME SB 829

ASME Code Cases 2083, N- 20, N-525

ISO 6207

MIL- DTL-24803

Plate, Sheet, and Strip

ASTM B 168 / ASME SB 168

ASTM B 906 / ASME SB 906

ASME N-525

ISO 6208

MIL-DTL-24802

DIN 17742

DIN 17750

ISO 6208

ISO 9722

12 COMPETITIVE ADVANTAGE

(1) More than 50 years experience of research and develop in high temperature alloy, corrosion resistance alloy, precision alloy, refractory alloy, rare metal and precious metal material and products.
(2) 6 state key laboratories and calibration center.
(3) Patented and innovative technologies.
(4) Ultra-purity smelting process VIM + IG-ESR + VAR.

(5) High performance.

13 BUSINESS TERM