ASTM B622 / ASME SB-622 / UNS N06022 / W.Nr. 2.4602
ASTM B622 Alloy C22 seamless pipes are produced by Thaida Stainless Steel Manufacturing (Thailand) Co., Ltd. at its Ban Bueng works in Chonburi, Thailand, for process lines that swing between oxidizing and reducing acid duty. The alloy carries 20.0 to 22.5% chromium alongside molybdenum and tungsten, and is identified as UNS N06022, or W.Nr. 2.4602 on a European drawing. It is listed under Hastelloy Seamless Pipes, with quotations raised at our Bang Phli, Samut Prakan office.
Alloy C22 seamless pipeUNS N06022 / W.Nr. 2.4602
EN 10204 3.1 certificate / 3.2 on request
A line class names a nominal size and a schedule. The table sets out the diameter, wall and length band each piece is made within, with the delivery condition and the test regime that travel with it.
ASTM B622, Standard Specification for Seamless Nickel and Nickel-Cobalt Alloy Pipe and Tube, is the only product standard behind the range above, and ASME SB-622 is its Boiler and Pressure Vessel Code counterpart. The standard identifies the material by its UNS number, N06022, and attaches no grade name, so Alloy C22 stays a commercial name carried on requisitions rather than an ASTM designation. A pipe order is written as a standard pipe size with a schedule, and the schedule fixes the wall for that size. Alloy C22 seamless tubes take the other basis in the same standard, specified by outside diameter, by minimum or average wall, and by length.
Chemical analysis is run once on each lot and a single tension test stands for it; afterwards each finished length is proved on internal hydrostatic pressure, or by a nondestructive electric examination where the order sets that route. The figures arrive on an EN 10204 3.1 (3.2 on request) material test certificate. Supporting paperwork covers the raw material origin, a 100% PMI record, the heat treatment charts and a measured report of size and surface roughness. Where a specification calls for more, the manufacturer test certificate can carry impact, bend, pitting and intergranular corrosion, eddy current and ultrasonic results. Third-party inspection or an independent laboratory test report is organized on request.
Chromium at 20.0 to 22.5% is what separates this alloy from the older members of the C family: Alloy C276 is held to 14.5 to 16.5%. The extra chromium in a UNS N06022 seamless pipe builds a passive film that survives oxidizing acids, molybdenum at 12.5 to 14.5% covers the reducing side of the same line, tungsten adds crevice resistance in chlorides, and carbon capped at 0.015% limits carbide precipitation in a weld heat-affected zone. These are the ASTM B622 limits each heat is reported against.
UNS N06022C22
| Element | Limit per ASTM B622 / ASME SB-622 (%) |
|---|---|
| Ni (Nickel) | Remainder |
| Cr (Chromium) | 20.0 to 22.5 |
| Mo (Molybdenum) | 12.5 to 14.5 |
| Fe (Iron) | 2.0 to 6.0 |
| W (Tungsten) | 2.5 to 3.5 |
| Co (Cobalt) | 2.5 max |
| Mn (Manganese) | 0.50 max |
| V (Vanadium) | 0.35 max |
| Si (Silicon) | 0.08 max |
| P (Phosphorus) | 0.02 max |
| S (Sulfur) | 0.02 max |
| C (Carbon) | 0.015 max |
Nickel is the remainder here rather than a stated minimum, and titanium, copper and niobium carry no limit of their own. The heat analysis against the column above is what a goods-in check reconciles line by line.
ASTM B622 sets three room-temperature minimums for this alloy. The 45% elongation figure is the one that stands out, because Alloy C276 and Alloy C4 are each set at 40%, which gives an ASME SB-622 C22 seamless pipe spool more margin as it takes cold bending and end preparation before a tension specimen is at risk of falling short.
| Property | Value | Unit |
|---|---|---|
| Tensile Strength, min | 690 (100) | MPa (ksi) |
| Yield Strength (0.2% offset), min | 310 (45) | MPa (ksi) |
| Elongation in 2 in. (50.8 mm) or 4D, min | 45 | % |
Yield strength also sits above both of those grades, 310 MPa against 283 MPa for Alloy C276 and 276 MPa for Alloy C4. All three figures are tabulated in ASTM B622 against the UNS number of each alloy, which is what makes them usable side by side when a piping engineer selects wall for a line class.
Alloy C22 is written these ways on American, European and Chinese drawings. Only the UNS number is assigned by the product standard; the remaining entries are cross-references used to match a drawing callout, and they carry no conformity claim to a European, Chinese or other national standard.
N06022 is the number marked on the material. A requisition written for 2.4602 or for NS3308 describes the same nickel-chromium-molybdenum-tungsten alloy, and we confirm the match at order entry instead of substituting one national standard for another.
The production envelope for a seamless WNR 2.4602 pipe runs from 6 mm to 457 mm on diameter, 1 mm to 65 mm on wall, and reaches 18 m on length. Which limits a length is measured against follows the way it was finished. Our standard route puts a cold draw or a cold roll after extrusion, so the cold-worked bands in the second table below govern most of what we supply. Pipe extruded and brought to size hot, without a finishing cold pass, is the exception, and the hot-worked diameter and wall limits carried in ASTM B622 are the ones it answers to.
| Nominal OD (D) mm | OD Tolerance (mm) | Wall Tolerance, Nominal Wall | Wall Tolerance, Minimum Wall |
|---|---|---|---|
| 25 ≤ D ≤ 48 | +0.40 / -0.79 | +16.0% / -12.5% | +28.5% / 0 |
| 48 < D ≤ 114 | ±0.79 | +16.0% / -12.5% | +28.5% / 0 |
| 114 < D ≤ 165 | ±1.2 | +16.0% / -12.5% | +28.5% / 0 |
| 165 < D ≤ 235 | ±1.6 | +16.0% / -12.5% | +28.5% / 0 |
Swipe sideways to see the full table.
Two features of that band decide how a hot-worked order is planned. The diameter limit is asymmetric in the smallest sizes, so a 48 mm nominal piece may run 0.40 mm over size but only 0.79 mm under, and a flange or fitting bore on the drawing has to accept the plus side rather than the nominal. The wall limit is generous upward: 16.0% over on nominal wall against 12.5% under, and 28.5% over with nothing under when the order reads minimum wall. A heavy run therefore changes the mass carried on the supports and the root heat input a welder works to, which is worth settling before the spool drawings are released. The hot-worked band also stops at 235 mm nominal diameter.
Those hot-worked figures apply reading by reading up to and including 127 mm outside diameter, ovality included. Past that diameter the hot-worked table governs the mean of the readings, while a single reading on its own is allowed twice the tabulated figure. Eccentricity is counted inside the individual measurements on both sides of that break.
A finishing cold draw or cold roll is the route this grade normally takes through our mill, and these ASTM B622 cold-worked tolerances are the set a seamless alloy 2.4602 pipe is then released against. The rows cover the diameters a process line is usually built from.
| Nominal OD (D) mm | OD Tolerance (mm) | Wall Tolerance, Nominal Wall | Wall Tolerance, Minimum Wall |
|---|---|---|---|
| 114 < D ≤ 152 | ±0.51 | ±12.5% | +28% / 0 |
| 152 < D ≤ 168 | ±0.64 | ±12.5% | +28% / 0 |
| 168 < D ≤ 219 | ±0.79 | ±12.5% | +28% / 0 |
| 219 < D ≤ 356 | +1.57 / -0.79 | +15.0% / -12.5% | +30.0% / 0 |
| 356 < D ≤ 610 | +3.18 / -0.79 | +15.0% / -12.5% | +30.0% / 0 |
Swipe sideways to see the full table.
These bands apply reading by reading with ovality included, except where wall thickness brings one of two conditions into play, and their break point is 114 mm rather than the 127 mm of the hot-worked rule. Where the nominal wall is 3% or less of the nominal diameter, the mean diameter has to meet the band while each separate reading is allowed that band widened by 0.5% of the nominal diameter. Above 114 mm diameter, with a nominal wall thicker than 3% of it, the mean diameter meets the band and one reading may reach double the tabulated value. Eccentricity again sits inside the individual readings.
A 219 mm piece finished cold therefore holds 0.79 mm either way on diameter, where the same nominal size left at size hot is allowed 1.6 mm. The cold-worked bands run on to 610 mm, past the 457 mm ceiling of our own envelope, so on a large-bore line it is the diameter we can draw that sets the top of a size list rather than the tolerance table.
Carbon held to 0.015% maximum leaves little available to form grain-boundary carbides as a heat-affected zone cools, which is what limits the risk of intergranular attack along a weld in seamless Alloy C22 pipe. Material leaves the mill solution annealed, then descaled, except where the annealing furnace runs under atmosphere control and no descaling is called for. Both are conditions the standard requires rather than a temperature schedule, which stays with the mill.
The two alloys split on chromium. C22 carries 20.0 to 22.5% against the 14.5 to 16.5% in Alloy C276 seamless pipes, and that difference favors C22 wherever the stream turns oxidizing, including nitric acid, chromic acid, hot concentrated sulfuric acid, chlorine-saturated water and hypochlorite. Where the duty stays reducing, C276 remains the established choice, and both alloys share the same 690 MPa tensile minimum, so a grade change on the requisition leaves the size and schedule alone.
Alloy C4 seamless pipes are the C-family grade held to the lowest yield minimum of the group, 276 MPa against 310 MPa for C22, with 40% elongation against 45%. Both sets of figures sit in the same ASTM B622 table. A circuit with tight cold bends, or one whose wall is chosen close to the yield minimum, is usually written in C22 for that reason.
Seamless nickel alloy C22 pipe is specified where one line has to carry oxidizing and reducing chemistry in turn, and where chloride is present throughout.
Reactor nozzle piping, column feed and draw-off lines and the transfer runs between them go into Alloy C-22 seamless pipe where the acid mix changes with the campaign and no single-duty alloy covers every case.
Scrubber headers, spray laterals and ductwork carry acid chloride condensate at the wet-dry interface, where the sulfuric and hydrochloric acids that form out of a coal-fired flue gas both bear on the metal.
Bleach plant piping and digester circulation lines handle chlorine dioxide and chloride-bearing liquor, which is the service mills name when they specify seamless 2.4602 pipe for those sections.
Furnace piping, heat exchanger connections and sour gas lines sit in mixed reducing and oxidizing service, where the chromium and molybdenum balance of this alloy holds across both ends of the swing.
Leach reactor piping and solvent extraction and electrowinning circuits in copper and precious metal plants move ferric chloride and sulfate liquors that pit lower-alloyed pipework along the weld line.
Multipurpose reactor and transfer piping has to survive a change of chemistry between campaigns and the concentrated nitric acid cleaning cycles in between, which is where the higher chromium earns its cost.
Packing
Mill-finish lengths strapped into bundles on timber bearers, small-bore and close-tolerance items in wooden cases, end caps fitted to every piece.
Marking
Identification goes onto each piece without leaving contamination that could harm the alloy, and the threshold between piece marking and tag marking is set by diameter and length.
Documents
EN 10204 3.1 (3.2 on request) material test certificate stating the heat chemistry, the lot tension result and the pressure or electric test on each piece.
Commercial terms
Quoted FOB, CIF or CFR, naming the discharge port on the offer itself.
Dispatch
Against a confirmed production slot, with the date restated on the order acknowledgement.
An indicative figure for Alloy C-22 seamless pipe is USD 24 to 62 per kg. Small-bore and light-wall items, short production runs and orders calling for an independent inspector fall in the upper half of that band, large-bore mill-finish lots toward the lower end, and the whole band moves with nickel, molybdenum and chromium on the day an order is priced. A size list with quantities turns the indication into a firm, dated offer.
Indicative only. Send your sizes and specification to Thaida for a firm quotation.
Production runs at 154 Moo.1 Map Phai, Ban Bueng, Chonburi 20170, Thailand, while quotations, order follow-up and shipping documents are prepared at 89/18 Moo.15 Enterprize Park, Bangna-Trad Road, Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand. We supply plants across Thailand and export to Singapore, Malaysia, Vietnam, Indonesia, the Philippines and India.
It is the ductility floor a cold bend works against. ASTM B622 sets 45% against UNS N06022, where Alloy C276 and Alloy C4 are each held to 40%, so a spool with tight radius bends or swaged ends keeps more margin before a tension specimen falls short. Send the bend schedule with your size list.
Hot-worked pipe takes a wider and partly asymmetric band: at 48 mm nominal diameter it runs +0.40 / -0.79 mm, with nominal wall at +16.0 / -12.5%. Cold-finished sizes are held tighter and the bands reach further up the diameter range. State the condition on the order and we confirm the figures for your size.
When the stream turns oxidizing. C22 carries 20.0 to 22.5% chromium against 14.5 to 16.5% in Alloy C276, which suits nitric acid, chromic acid, hot concentrated sulfuric acid, chlorine-saturated water and hypochlorite. For acid duty that stays reducing, C276 is the usual pick. Send the medium and concentration for a check.
Each lot is chemically analyzed once and a single tension test represents it. Every finished length is then pressure tested hydrostatically, or given a nondestructive electric test in its place. Should a lot's tension specimen fall short, two further specimens from different pieces are taken and both have to meet the requirement.
The marks go on any piece at least 19.0 mm (3/4 in.) in diameter that also exceeds 914 mm (3 ft) in length: our name, UNS N06022, ASTM, the specification number, the heat and the nominal size. Below either threshold the same detail is applied piece by piece, or on a tag tied to the bundle.
457 mm outside diameter. Wall runs to 65 mm and a single length to 18 m, and the envelope opens at 6 mm on diameter and 1 mm on wall. Hot-worked diameter limits are tabulated to 235 mm nominal, so anything larger is quoted as a cold-finished item.
The specification lists its alloys by UNS designation only, and N06022 is the entry that governs this material; there is no grade-name column in it. Alloy C22 is the commercial name used on requisitions and drawings. Both are quoted on the order so the document set matches your drawing.
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