Heat-Resistant Stainless Steel Seamless Pipe & Tube
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What is heat-resistant pipe and tube?
In hot gases – air, flue gas, furnace atmospheres – heat-resistant steel forms a dense, adherent oxide layer and does not suffer heavy scaling. This is mainly due to chromium, silicon and aluminum. Heat-resistant tube is therefore not meant to resist acids, but to work at temperatures where ordinary stainless steel would quickly lose material to flaking scale. Grades in this group are covered by EN 10095. If strength under load matters more than oxidation resistance, read our article Heat-resistant vs. creep-resistant steel: the differences.
Grades in this category: from 1.4841 to 15X25T
Most tubes – more than two thousand items – are made of 1.4841 (X15CrNiSi25-21, AISI 314): an austenitic steel with 24–26% chromium, 19–22% nickel and elevated silicon, which improves oxidation resistance. 1.4845 (X8CrNi25-21, AISI 310S) has similar chromium and nickel, but less carbon and silicon. A few items are in 1.4828, which is leaner in chromium and nickel. A separate group consists of ferritic steels 1.4746 and 1.4749 (also listed as 15X25T) with about 25% chromium and no nickel – their interchangeability is covered on the page 15X25T steel as an equivalent of grade 1.4749. The ferritic group also includes 1.4724 with added aluminum. The range is rounded out by niobium-stabilized 1.4912 / TP347H creep-resistant tube and Alloy 800H, an iron-nickel-chromium alloy. Several grades in one description indicate material that meets multiple standards at once; the grade of each heat is confirmed by an EN 10204 3.1 certificate.
Composition of austenitic heat-resistant steels
| Grade | C | Si | Cr | Ni |
|---|---|---|---|---|
| 1.4828 | ≤ 0.20 | 1.5–2.5 | 19.0–21.0 | 11.0–13.0 |
| 1.4841 / 314 | ≤ 0.20 | 1.5–2.5 | 24.0–26.0 | 19.0–22.0 |
| 1.4845 / 310S | ≤ 0.10 | ≤ 1.5 | 24.0–26.0 | 19.0–22.0 |
Composition per EN 10095 (wt. %). Equivalents: 1.4841 = X15CrNiSi25-21 = AISI 314 = UNS S31400 · 1.4845 = X8CrNi25-21 = AISI 310S = UNS S31008 · 1.4828 = X15CrNiSi20-12.
Sizes and wall selection
Heat-resistant tube is available in outside diameters from 8 to 305 mm (DN 6–300) with walls from 1 to 20 mm, plus more than a hundred heavy-wall hollow bars. In parts running red-hot, a heavier wall provides a material allowance for scaling and limits sagging under the part’s own weight, so radiant tubes and retorts are sized with a bigger margin than lines working at ambient temperature. Any tube can be cut to length.
Applications: furnaces, burners, protection tubes
1.4841 and 1.4845 tube is used in heat-treating furnaces and hardening shops as radiant tubes, muffles and retorts, in burners and nozzles, as thermocouple protection tubes and guides in the hot zone, as well as in boilers, waste and biomass incineration plants, and the cement and ceramics industries. The ferritic 1.4746 / 1.4749 grades perform well in sulfur-bearing atmospheres, where high-nickel steels are more prone to sulfidation. For an overview of grades and their typical service temperatures, see Heat-resistant steel: grades and industrial applications.
Austenitic or ferritic – and when 321H is enough
Austenitic 1.4841 and 1.4845 retain better strength and ductility at high temperatures and are easier to weld. The ferritic grades contain no nickel and handle sulfur well, but become brittle after long exposure to heat, so they require care during installation and cold working. If the service temperature does not exceed about 800°C and the resistance of welds to intergranular corrosion matters more than scaling resistance, 321H / 1.4878 tube is usually sufficient. For systems at ambient temperature, where corrosion resistance rather than oxidation resistance counts, choose 304 stainless tube, 316Ti seamless tube or duplex tube.
See also: in the same grades we offer heat-resistant round bar and heat-resistant sheet. Stainless and acid-resistant tube in other grades is in our seamless tube and hollow bar category.