Oceaneering Corrosion Resistant Alloys , UNS N06686 High Performance Alloys

Corrosion resistant alloy 686 (N06686) pipe, strip, bar, forging, fastener, wire for oceaneering

1 PRODUCT

Outstanding corrosion resistant alloy 686 (UNS N06686) for oceaneering and marine application.

Alloy 686 is available in product forms as pipe, tube, sheet, strip, plate, round and hexagonal bar, forging, forging stock, wire and wire rod in coil, and fastener (bolts, nuts and studs etc).

2 EQUIVALENT DESIGNATION

UNS N06686, W.Nr.2.4606, NiCr21Mo16W(DIN), Inconel® Alloy 686

3 APPLICATION

Alloy 686 is used for resistance to aggressive media in chemical processing, oceaneering, pollution control, pulp and paper manufacture, and waste management applications.

4 OVERVIEW

Alloy 686 is a single-phase, low carbon, austenitic Ni-Cr-Mo-W alloy offering outstanding corrosion resistance in a range of severe environments. Its high nickel (Ni) and molybdenum (Mo) provide good resistance in reducing conditions, and high chromium (Cr) offers resistance to oxidizing media. Molybdenum (Mo) and tungsten (W) aid resistance to localized corrosion such as pitting. Iron (Fe) is closely controlled to enhance properties. Low carbon (C) helps minimize grain boundary precipitation to maintain corrosion resistance in the heat affected zones of welded joints. Resistance to general, pitting and crevice corrosion increases with the alloying (Cr+Mo+W) content, and Alloy 686 scores higher than competitive materials.

Alloy 686 is known as the corrosion resistant alloy of the 21st century. It is the most highly alloyed of the commercial corrosion resistant alloy materials.

5 CHEMICAL COMPOSITION (wt%):

6 PHYSICAL PROPERTY

Density at room temperature: 0.315 lb/in³ (8.73 g/cm³)

Melting range: 2440-2516°F(1338-1380°C)

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

7 MECHANICAL PROPERTIES

Table 7-1 Room temperature mechanical properties

Table 7-2 High temperature tensile tests

8 CORROSION RESISTANCE

Alloy 686 offers outstanding resistance to general corrosion, to stress-corrosion cracking, and to pitting and crevice corrosion. Its resistance to intergranular precipitation during welding maintains its corrosion-resistance in the heat-affect zones of welded joints.

It offers resistance to both reducing and oxidizing acids and to mixed acid solutions. It is especially suited to handling mixed acids containing high concentrations of halides. It has shown good resistance to mixed acid media with pH levels of 1 or less, and chloride levels of over 100,000 ppm.

Alloy resistance to pitting corrosion is often compared by reference to the so-called “Pitting Resistance Equivalency Number” - the PREN. Performance potential can be compared by the calculation:

PREN = %Cr + 1.5 (%Mo + %W + %Nb)

In ascending order of excellence, the highly alloyed Alloy 686 is proved as the optimum choice among commercially available, pit-resistant, Ni-Cr-Mo alloys:

Corrosion Resistance - Marine applications

Alloy 686 exhibits excellent resistance to general, galvanic and localized corrosion and hydrogen embrittlement in seawater (Tables below). In addition, seawater has only a minor effect on the fatigue strength of the alloy (Figure 2). Thus, alloy 686 is an ideal material for marine service.

Alloy 686 fasteners (bolts, nuts, studs, etc.) perform well in marine service. Alloy 686 can be strengthened by cold working to yield strength levels of 150 ksi if high strength bolting is required. These high strength fasteners offer essentially the same resistance to corrosion in seawater as annealed material.

Table 8-1 Resistance to crevice corrosion in chlorinated seawater at 60°C for 60 days

Table 8-2 Resistance to crevice corrosion in quiescent seawater at 25°C (77°F) for 60 Days

Table 8-3 Resistance to crevice corrosion in flowing seawater at 14.4°C (58°F) for 180 Days

9 WORKING INSTRUCTION

Fabrication

Alloy 686 is readily fabricated. Forming operations can be by standard methods used for other high-nickel alloys such as Alloy C-276, Alloy 22 and Alloy 625. Work hardening during cold forming may make intermediate annealing necessary.

Hot working

Hot forming should be between 1600-2250°F (870-1230°C), with all heavy forming above 2000°F (1090°C).

Annealing

Alloy 686 is normally annealed at 2150-2200°F (1180-1200°C) with rapid cooling.

10 STANDARD SPECIFICATION

Alloy 686 allowable design stresses for ASME Section VIII, Division 1 construction for service up to 800°F are defined in ASME Code Case 2198 and Table 1B of ASME Section II, Part D. For ASME fabrication, Alloy 686 is classified as a P-No.43 material. Alloy 686 is approved by VdTÜV for use at temperatures up to 400°C in Werkstoffblatt 515/12.97. This alloy is approved under NACE MR0175 for oil and gas service.

All forms

NACE RP0294

Rod, bar, wire, forging and forging stock

ASTM B462

ASME SB564 / ASTM B564

ASME SB574 / ASTMB574

DIN 17752

DIN 17753

DIN 17754

Plate, sheet and strip

ASME SB575 / ASTMB575

ASTM B 906 / ASME SB 906

DIN 17750

Pipe and tube

ASTM B 163 / ASME SB 163

ASME SB619 / ASTM B619

ASME SB622 / ASTM B622

ASME SB626 / ASTM B626

ASME SB 751 / ASTM B751

ASME SB 775 / ASTM B775

ASME SB 829 / ASTM B829

DIN 17751

Welding products

AWS A5.14 / ERNiCrMo-14

AWS A5.11 / ENiCrMo-14

Fasteners

ASTM F467, F467M

ASTM F468, F468M

SAE AMS J2295, J2271, J2655, J2280, J2484, J2485

Composition

DIN 17744

11 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 technologies.

(4) Ultra-purity smelting process: VIM + IG-ESR + VAR

(5) Excellent high performance.

13 BUSINESS TERM