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Alloy G-30 / Alloy G-2 Plate, Sheet & Strip (SB-434, N10003/N10242)
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Alloy G-30 (UNS N10003) and Alloy G-2 (UNS N10242) are nickel-molybdenum-chromium-iron alloys supplied as plate, sheet and strip under ASME SB-434. They occupy the high-molybdenum end of the nickel-alloy family and are selected where the corrosive environment defeats the lower-molybdenum grades such as Alloy C-22 or Inconel 625.
Specification Coverage
SB-434 covers nickel-molybdenum-chromium-iron alloys UNS N10003 and UNS N10242 in the form of plate, sheet, and strip for use in general corrosive service. The same two UNS designations are covered by SB-573 for rod, and both appear in the grade listing of SB-366 for factory-made wrought nickel and nickel alloy fittings, which means fittings and fittings components can be ordered against the same alloy from the same melt family. For flat-rolled product dimensional tolerances, the general requirements of SB-906 apply.
Grade Comparison
| Grade | UNS | Ni | Mo | Cr | Fe max | Tensile min |
|---|---|---|---|---|---|---|
| Alloy G-30 | N10003 | rem. | 15.0-18.0 | 6.0-8.0 | 5.0 | 100 ksi (690 MPa) |
| Alloy G-2 | N10242 | rem. | 24.0-26.0 | 7.0-9.0 | 2.0 | 105 ksi (725 MPa) |
| Hastelloy C-22 | N06022 | rem. | 13.0-16.5 | 20.0-23.0 | 3.0 | 100 ksi (690 MPa) |
| Hastelloy C-276 | N10276 | rem. | 15.0-17.0 | 16.0-18.0 | 4.0 | 100 ksi (690 MPa) |
The comparison shows the design logic clearly. Against the C-family alloys, Alloy G-30 and G-2 trade chromium for molybdenum. Molybdenum is the element that governs resistance to reducing acids and to chloride pitting, while chromium governs oxidising acid resistance. An engineer choosing between C-276 and Alloy G-30 is therefore making a statement about which acid type dominates the exposure.
Chemical Composition (ASME SB-434 Table 1)
| Element | UNS N10242 (%) | UNS N10003 (%) |
|---|---|---|
| Nickel | Remainder | Remainder |
| Molybdenum | 24.0-26.0 | 15.0-18.0 |
| Chromium | 7.0-9.0 | 6.0-8.0 |
| Iron, max | 2.0 | 5.0 |
| Carbon | 0.03 max | 0.04-0.08 |
| Silicon, max | 0.80 | 1.00 |
| Cobalt, max | 1.00 | 0.20 |
| Manganese, max | 0.80 | 1.00 |
| Tungsten, max | – | 0.50 |
| Vanadium, max | – | 0.50 |
| Phosphorus, max | 0.030 | 0.015 |
| Sulfur, max | 0.015 | 0.020 |
| Aluminum plus titanium, max | – | 0.50 |
| Aluminum, max | 0.50 | – |
| Copper, max | 0.50 | 0.35 |
| Boron, max | 0.006 | 0.010 |
Mechanical Properties (ASME SB-434 Table 2)
| UNS | Tensile Strength min, ksi (MPa) | Yield Strength (0.2% Offset) min, ksi (MPa) | Elongation in 2 in. (50.8 mm) or 4D min, % |
|---|---|---|---|
| N10003 | 100 (690) | 40 (280) | 40 |
| N10242 | 105 (725) | 45 (310) | 40 |
D in the elongation column refers to the diameter of the tension specimen.
Grain Size for Annealed Sheets (ASME SB-434 Table 3)
| Thickness, in. (mm) | ASTM Micrograin Size Number, max | Average Grain Diameter max, in (mm) |
|---|---|---|
| 0.125 (3.175) and under | 3.0 | 0.0050 (0.127) |
| Over 0.125 (3.175) | 1.5 | 0.0084 (0.214) |
Proper heat treatment during or subsequent to fabrication is necessary for optimum performance, and the manufacturer should be consulted for details (SB-434, Appendix X1.1).
Applications
Alloy G-30 and Alloy G-2 flat-rolled product is specified in pulp and paper bleaching equipment, hydrochloric and sulphuric acid processing, brine and chlor-alkali systems handling reducing acid contaminants, and in reactor and column internals exposed to mixed acid streams. Because Alloy G-2 carries over 24 % molybdenum, it is the preferred grade in hot hydrochloric acid where the C-family alloys would suffer general corrosion. Plate is commonly cut into vessel shells, tube sheets, and flange blanks, while sheet and strip go into fabricated weld overlay and lining work.
Certification and Inspection
Material is supplied with a mill test certificate to ASME SB-434 showing heat number, chemical analysis, mechanical properties, grain size, and dimensions. Supplementary inspection options include ultrasonic testing, eddy current testing, and intergranular corrosion testing. For material that will be code-stamped, the applicable ASME Section VIII Div. 1 or Div. 2 certification can be provided on request.
Ordering Information
Please specify when requesting a quotation: grade (Alloy G-30 / N10003 or Alloy G-2 / N10242), product form (plate, sheet or strip), thickness and width, length, hot-rolled or cold-rolled condition, quantity, destination port, and any required certification or third-party inspection. We will confirm availability and lead time and quote FOB Hefei, China in USD.
Related specifications and products. Alloy G-30 and Alloy G-2 sit in the same high-temperature nickel alloy plate family. See nickel alloy plate, sheet and strip Alloy 28 plate and strip Alloy 30 plate, bar and fittings for the dimensional and material basis behind this page.
