ASTM A213 / ASME SA-213 / UNS N08904 / W.Nr. 1.4539
High-alloy ASTM A213 UNS N08904 seamless tubes form part of the stainless range that Thaida Stainless Steel Manufacturing (Thailand) Co., Ltd. makes at Ban Bueng, Chonburi, Thailand, for reducing acids and chloride-bearing cooling water. Nickel, molybdenum and copper together carry the corrosion duty, and European drawings number the same alloy WNR 1.4539. The grade belongs with the high-alloy types we list under stainless steel seamless tubes, and order papers are drawn up at our office in Bang Phli, Samut Prakan.
Stainless Steel 904L seamless tubeUNS N08904 / W.Nr. 1.4539
EN 10204 3.1 certificate / 3.2 on request
An order in this grade is written as an outside diameter against a wall, with the wall basis named for each item. The table sets out the dimensions we draw, the condition we deliver and the tests that every tube and every lot passes.
The scope of A213 is seamless tubing for boilers, superheaters and heat exchangers, and the alloy appears in its tables as the number N08904 with the grade column left empty. Every ASTM A213 UNS N08904 seamless tube we quote is therefore identified by that number on the order, on the mark and on the certificate, and ASME SA-213 takes the same requirements into code work. Where the line item is sized by nominal bore and schedule instead, the same alloy is produced as stainless steel 904L seamless pipes.
Two checks decide what a release is worth: the analysis that proves the steel, and the tension result that proves the finished tube.
Chemistry is verified twice over. The heat analysis is taken at the melt, and A213 then calls for a product analysis on a single piece per heat, either a billet or a finished tube, so the figures printed against your order describe metal that was actually worked. One reading outside the bands does not condemn the heat on its own either: where a product analysis result falls outside the limits for the grade, the specification provides for a retest rather than treating that single figure as final.
Tension testing is counted by lot, and a lot here is one size out of one heat. A lot of 50 tubes or fewer is covered by a single tension test, while above 50 pieces the lot needs two, so a large release carries two independent sets of results instead of one. Hardness is read separately, on two tubes drawn from the same lot, and no hardness reading is called for where the wall measures under 1.65 mm.
A213 draws a floor under its mechanical property requirements: tubing below 3.2 mm inside diameter, or thinner than 0.4 mm in the wall, falls outside them, and such items are judged on chemistry, dimensions and the per-tube proof test rather than on tensile and yield figures. Our drawn range opens at 6.35 mm outside diameter and 0.89 mm wall, so an ordinary seamless stainless steel 904L tube item sits well inside the tested band and the exemption only comes up when a special micro-bore size is discussed.
A213 fixes the composition below in weight percent, and both analyses, heat and product, are judged against it. Where only one figure is given, read it as a ceiling.
UNS N08904904L
| Element | A213 Limit for N08904, % |
|---|---|
| C (Carbon) | 0.020 max |
| Mn (Manganese) | 2.00 max |
| P (Phosphorus) | 0.040 max |
| S (Sulfur) | 0.030 max |
| Si (Silicon) | 1.00 max |
| Cr (Chromium) | 19.0 to 23.0 |
| Ni (Nickel) | 23.0 to 28.0 |
| Mo (Molybdenum) | 4.0 to 5.0 |
| N (Nitrogen) | 0.10 max |
| Cu (Copper) | 1.00 to 2.00 |
Three of those bands do the corrosion work. The 23.0 to 28.0% nickel band holds a fully austenitic structure and raises resistance to chloride stress corrosion cracking, while molybdenum at 4.0 to 5.0% answers chloride pitting and crevice attack. Copper at 1.00 to 2.00% is the band that sets this alloy apart from the molybdenum-bearing 300 series grades, and it is what puts the tube into reducing and acidic media: sulfuric, phosphoric and acetic acid are the streams it is most often asked about. Carbon capped at 0.020% keeps chromium in solution instead of in carbide, so a seamless N08904 stainless steel tube holds its resistance across a welded joint with no stabilizing element present.
Tension results for a lot come from tube that has already been solution treated, and they are measured against a single set of minimums covering every wall we draw.
| Property | Requirement for N08904 |
|---|---|
| Tensile strength, min | 490 MPa (71 ksi) |
| Yield strength, min | 215 MPa (31 ksi) |
| Elongation in 50 mm (2 in.), min | 35% |
| Hardness, max | 192 HBW / 200 HV, or 90 HRB |
No wall step interrupts those figures: a 12.7 mm wall answers the same 490 MPa as a 0.89 mm wall. The yield floor of 215 MPa stands above the 170 MPa that A213 sets for TP316L, and the 35% elongation minimum leaves the ductility that tube end expansion and bending work call for. The hardness ceiling is a requirement rather than a note, so a reading above 192 HBW puts the lot out of specification.
Austenitic tubing is furnished heat treated. For this alloy the solution treatment starts at 1100 °C (2000 °F), after which the tube is quenched in water or cooled as rapidly by other means; A213 also allows that quench to follow hot forming directly, with no separate reheat, provided the tube has not dropped below the minimum first. Nothing in the standard attaches a grain size requirement to the alloy, so no grain size figure appears on the certificate for a seamless WNR 1.4539 tube. The solution-annealed structure is also non-magnetic, which some instrument installations ask about before the order is placed.
One supplementary requirement is worth naming on the purchase order. The rapid cool is there to stop carbides re-precipitating, and A213 lets that be demonstrated by a test for intergranular corrosion under ASTM A262 Practice E. It runs only when the order calls for it, so list it with the size list rather than assuming it. The stress-relieved annealed option A213 offers is written against other grades, not against N08904.
American, European and Japanese documents name this alloy as set out below. Only the UNS number governs what we make.
European drawings usually arrive with 1.4539 written on them. We accept that line, make it to A213 as N08904, and print the number beside the UNS designation purely so the drawing and the paperwork agree. The cross-reference stops there, because the European chemistry written against 1.4539 is not identical to the A213 limits in the table above, and our certificate therefore makes no conformity statement to a European tube standard. Where a project genuinely needs the European limits, say so before the heat is melted.
Reboiler, condenser and brine heater bundles reach us as a diameter and a wall against each item, with a fixed cut length beside them. Our drawn envelope covers:
| Dimension | Figure |
|---|---|
| Outside diameter | 6.35 to 257 mm |
| Wall thickness | 0.89 to 12.7 mm |
| Length | Up to 22 m straight, or cut to size |
| Diameters A213 calls usual | 3.2 mm inside diameter up to 127 mm outside diameter |
| Walls A213 calls usual | 0.4 to 12.7 mm minimum wall |
| Larger diameters | Furnished under the clause that permits other diameters once every remaining requirement is met |
Condenser and brine heater bundles usually sit in the lower half of that envelope, where a thin wall and an exact cut length matter more than diameter, while reboiler and reactor circuits take the heavier walls. Above 225 mm the permitted diameter variation is agreed on the order, since the standard stops tabulating diameter variations at that size although we can draw a seamless 1.4539 stainless steel tube to 257 mm. Delivery condition is covered as well: lengths arrive reasonably straight with burr-free ends, and grinding out a surface imperfection is permitted as long as the remaining wall is still inside tolerance.
Two neighboring grades come up whenever a bundle in this alloy is priced.
SMO 254 seamless tubes are the step up for chloride service. A213 sets S31254 at 6.0 to 6.5% molybdenum with 0.18 to 0.25% nitrogen, against 4.0 to 5.0% molybdenum and a 0.10% nitrogen ceiling in N08904. The balance tips the other way on nickel and copper, where N08904 carries 23.0 to 28.0% nickel and 1.00 to 2.00% copper against 17.5 to 18.5% nickel with copper at 0.50 to 1.00% in S31254. Reducing acid duty therefore tends to stay with grade 904L, while warm seawater and concentrated brine are where the higher molybdenum and nitrogen earn their place.
The step down is larger. A213 gives TP316L 10.0 to 14.0% nickel, 2.00 to 3.00% molybdenum and no copper requirement at all, so 316L stainless steel seamless tubes remain the sensible choice for general process water and mild chemical duty. A 904L stainless steel seamless tube earns its extra cost only where a reducing acid is present, or where the chloride level is high enough to pit the lower-alloy grade.
The alloy is specified where a reducing acid or a chloride-bearing water rests against the bore of a seamless N08904 stainless steel tube for the working life of the plant.
Shell and tube exchangers carrying acid process streams take the alloy for its copper and molybdenum. Bundles are cut to a fixed length and supplied plain ended for rolling into the tubesheet.
Reactors and the reboilers that serve them combine heat with an aggressive liquor. Heavier walls from the middle of our range suit this duty, and each item is marked to its tested lot.
Condensers in thermal power stations and the absorber and liquor circuits of flue gas desulfurization plant both face acidic, chloride-laden water. Thin-wall tube is cut to the bundle drawing for these services.
Brine heaters concentrate chloride on the process side while steam heats the outside, which is exactly where copper and molybdenum together are worth paying for. Cut lengths are prepared before dispatch.
Reverse osmosis trains and the treated water circuits around them run pressurized saline streams through small-bore tubing. Close diameter control matters more here than wall, so these items are ordered cold finished.
Process coolers at coastal installations and offshore facilities use seawater or brackish water on the shell side. The nickel content answers chloride stress corrosion cracking, and bundles ship with caps fitted in every bore.
Bundles
Made up size by size from one heat, strapped or loaded into timber cases, and every bore gets a cap.
Marking
Our name, the specification number, the grade identification, the finishing route and the wall basis on each tube.
Surface care
Tubing is kept clear of carbon steel through cutting, bundling and loading so the pickled surface stays free of iron.
Papers in the consignment file
The EN 10204 3.1 (3.2 on request) certificate, the mill certificate for the starting material, the solution treatment record, full PMI coverage on every item and a packing note that lists each line separately.
Available on request
An independent laboratory test report, attendance by a third-party inspector, and the result of the ASTM A262 Practice E intergranular test when that test was ordered.
Commercial terms
FOB, CIF or CFR, named in the quotation.
Indicative pricing for this grade runs from about USD 9 to USD 17 per kg. Nickel is the largest part of the alloy bill, with molybdenum and copper behind it, so a quoted rate moves with those metal markets rather than with a standing list. Small diameters, thin walls, a bright annealed surface, short drawing runs and added testing all sit at the upper end. Send the size list and we price it line by line.
Indicative only. Send your sizes and specification to Thaida for a firm quotation.
Every ASTM A213 stainless steel 904L seamless tube on an order is pierced, drawn, solution treated, tested and marked at one address: 154 Moo.1 Map Phai, Ban Bueng, Chonburi 20170, Thailand. Quotations, test certificates and export papers are issued from 89/18 Moo.15 Enterprize Park, Bangna-Trad Road, Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand. Deliveries inside Thailand run direct from the factory, while consignments for Singapore, Malaysia, Vietnam, Indonesia, the Philippines and India are containerized for sea freight.
Because A213 leaves the grade column empty for it and identifies the alloy only as N08904. There is no TP designation to quote, so the order, the mark and the certificate for an ASTM A213 UNS N08904 seamless tube all carry the UNS number instead. A drawing written any other way is still produced and certified as N08904.
Copper at 1.00 to 2.00% works in reducing and acidic media, where a chromium passive film is least stable, which is why sulfuric, phosphoric and acetic acid service brings the alloy into the inquiry. Molybdenum at 4.0 to 5.0% works on chlorides instead, against pitting and crevice attack. The two cover different mechanisms.
The product analysis. A213 has a single piece from every heat analyzed, a billet or a finished tube, alongside the heat analysis taken at the melt, so the figures on your certificate describe worked metal. Should a product analysis result fall outside the limits, the specification provides for a retest rather than treating one reading as final.
One test for a lot of 50 pieces or fewer, and two once the lot runs beyond that. A lot is one size out of one heat, so an order split across several sizes carries more tension results than the same tonnage in a single size. Hardness is read on a separate pair of tubes.
Two different finished tubes. The flattening test is taken at both ends of one tube from the lot and the flaring test at both ends of a second tube, so the two tests never come off the same piece. Both sets of results are reported against the lot.
They apply right across our range. A213 stops applying its mechanical property requirements below 3.2 mm inside diameter or below 0.4 mm wall, and our drawn range begins at 6.35 mm outside diameter with a 0.89 mm wall, so every item we release is inside the tested band. Ask us before specifying anything smaller.
When a reducing acid is in the stream, or the chloride level is high enough to pit the lower-alloy grade. A213 gives TP316L 2.00 to 3.00% molybdenum and no copper requirement, against 4.0 to 5.0% molybdenum plus the 1.00 to 2.00% copper here. State the medium, its concentration and the water chemistry with the inquiry.
No. We print WNR 1.4539 beside UNS N08904 as a cross-reference so a European drawing and our paperwork line up, while the conformity statement stays with A213. The European chemistry written against that number differs from the A213 limits, so no European tube standard is claimed for a seamless 1.4539 stainless steel tube.
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