Alloy 600 Plate: Material Overview and Service Range
Alloy 600 plate is a nickel-chromium-iron material designated UNS N06600 and supplied to ASTM B168 / ASME SB168. Its high nickel content allows it to tolerate reducing environments, while chromium builds a protective oxide that resists oxidising and carburising conditions. The grade is regarded as virtually immune to chloride-ion stress corrosion cracking in the annealed condition and combines good strength with reasonable machinability.
The alloy is used from cryogenic temperature up to about 1093 °C (2000 °F), where oxidation resistance rather than structural load governs the selection. Typical duties include chemical process vessels and reactors, nuclear power plant components, heat-treating furnace internals, and aerospace parts exposed to hot gases. Because the material is austenitic and single phase as supplied, it is not strengthened by heat treatment, and cold work is the only practical way to raise its strength.
Chemical Composition Limits per ASTM B168
ASTM B168 specifies the following limits for UNS N06600 plate, sheet and strip. Product analysis must fall inside these ranges.
| Element | Limit, % | Function |
|---|---|---|
| Nickel, Ni | 72.00 min | Matrix; resistance to reducing media and stress corrosion cracking |
| Chromium, Cr | 14.00-17.00 | Oxide scale formation, oxidation and corrosion resistance |
| Iron, Fe | 6.00-10.00 | Matrix substitution; distinguishes the grade from iron-free nickel-chromium alloys |
| Carbon, C | 0.15 max | Strength contribution; upper limit for weldability and ductility |
| Manganese, Mn | 1.00 max | Desulphurisation and deoxidation during melting |
| Silicon, Si | 0.50 max | Deoxidation; higher levels impair hot workability |
| Copper, Cu | 0.50 max | Residual element, controlled for consistent corrosion behaviour |
| Sulphur, S | 0.015 max | Residual element, controlled to protect hot ductility |
Purchasers should compare the certified heat analysis against these limits rather than against a nominal composition quoted verbally, because the iron range is what separates this grade from iron-free nickel-chromium alloys and changes both magnetic behaviour and thermal expansion.
Mechanical and Physical Properties of Alloy 600 Plate
The following values are typical for annealed plate. Design values should always be taken from the applicable pressure vessel or aerospace code at the design temperature.
| Property | Typical value |
|---|---|
| Tensile strength | 655 MPa (95,000 psi) |
| Yield strength, 0.2% offset | 310 MPa (45,000 psi) |
| Elongation | 40% |
| Density | 8.47 g/cm³ |
| Melting point | About 1413 °C (2580 °F) |
| Structure | Austenitic, face-centred cubic |
| High-temperature capability | Oxidation resistant to about 1093 °C (2000 °F) |
Two practical points follow. First, the plate keeps useful strength at temperature that would destroy carbon steel, but its creep strength is lower than that of molybdenum-bearing nickel-chromium grades, so heavily loaded hot components may need greater thickness or a different grade. Second, thermal expansion is relatively high and thermal conductivity relatively low, which matters when plate is welded into mixed-material assemblies or exposed to thermal shock.
Available Sizes, Thickness and Tolerance Bands
Plate and sheet are normally stocked in the following standard formats, with thickness from 0.1 mm to 12 mm and length up to 12500 mm. Cut-to-size and custom widths are also produced to order.
| Format | Standard size (mm) |
|---|---|
| Plate | 1000 x 2000 |
| Plate | 1220 x 2440 |
| Plate | 1500 x 3000 |
| Plate | 2000 x 2000 |
| Plate | 2000 x 4000 |
| Thickness range | 0.1 mm to 12 mm |
| Maximum length | 12500 mm |
Thickness tolerance is a banded table, not a single figure. Permitted over and under deviations widen as nominal thickness increases and narrow as sheet width decreases; supplier tolerance tables cover width bands from below 1200 mm up to between 2700 mm and 3000 mm and quote allowances of roughly 0.20 mm to 1.80 mm depending on the thickness and width combination. Buyers who need close tolerance should state the width band and thickness range explicitly on the enquiry so that the correct tolerance column is applied, and should expect the tolerance to apply to the ordered nominal thickness rather than to the measured average.
Forms, Tempers and Fabrication Notes
Product forms. Coils, foils, shim sheet, perforated sheet, chequered plate, strip, flats, blank circles, ring flanges, angle, channel and tray sections are all produced from this grade.
Temper conditions. Soft, hard, half hard, quarter hard and spring hard tempers are available; the harder tempers raise strength and lower elongation, so the choice follows the forming route.
Working. Cold forming is readily carried out on annealed plate, but the alloy work hardens quickly, so generous bend radii and interstage annealing are advisable for severe shapes.
Welding. Matching nickel-chromium-iron filler is used; low heat input, controlled interpass temperature and clean surfaces minimise hot cracking risk. Post-weld pickling or mechanical descaling restores the oxide film.
Machining. Use sharp, positive rake tooling with heavy, consistent feeds and generous cutting fluid, since the alloy tends to work harden and produce stringy chips.
Frequently Asked Questions
Q: What is alloy 600 plate used for?
Chemical reactors, heat exchangers, furnace internals, nuclear plant components and aerospace hardware where a combination of oxidation resistance and immunity to chloride stress corrosion cracking is required.
Q: Is alloy 600 the same as the N06600 designation?
Yes. Alloy 600 is the widely used trade name for the nickel-chromium-iron grade that ASTM B168 lists as UNS N06600.
Q: Can the plate be hardened by heat treatment?
No. It is an austenitic single-phase alloy, so strength is raised only by cold work; annealing is used to restore ductility.
Q: What thickness tolerance should be expected?
Tolerance is banded by nominal thickness and sheet width, with allowances from about 0.20 mm to 1.80 mm across the standard width bands, so the width and thickness must be quoted together.
Q: How does it perform in chloride environments?
The high nickel content makes the annealed grade essentially immune to chloride-ion stress corrosion cracking, and chromium provides resistance to oxidising chloride conditions, although pitting resistance is lower than that of molybdenum-bearing grades.
Q: What documentation should accompany the plate?
A material test report showing the heat number, certified chemical analysis against ASTM B168, mechanical test results and the heat treatment condition, plus any dimensional or non-destructive inspection agreed with the buyer.
