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MLTI Private Limited manufactures and exports Stainless Steel 347H Pipe based in Gujarat, India, has been making austenitic pipe since 2008 and now produces nearly 8,000 MT of pipes and tubes a year. ASTM A312 TP347H, UNS S34709, is the elevated-temperature member of the niobium-stabilised austenitic family, and SA-312 places it among the grades meant for service where creep and stress rupture properties govern the design. Carbon sits in a controlled band of 0.04 to 0.10%. Niobium, which older American drawings still call columbium, is specified as a ratio rather than a fixed figure: eight times the carbon content as a minimum, 1.0% at the ceiling. Chromium runs from 17.0 to 19.0%, and nickel from 9.0 to 13.0%. Certified minima for the pipe are 515 MPa tensile strength, 205 MPa yield strength, and elongation in 50 mm of 35% longitudinal and 25% transverse, with an ASTM E112 grain size of No. 7 or coarser.
We produce 347H stainless steel pipe to ASTM A312 / ASME SA-312, dimensioned to ASME B36.19M, from 1/8 inch NB to 10 inch NB, in lengths up to 12 metres, with square and rectangular hollow profiles formed to order. Both routes are open to us. Seamless 347H pipe is made by a process that involves no welding at any stage, so the wall carries no longitudinal joint, and it goes to the higher-pressure circuits. Welded pipe is formed from strip and closed by an automatic weld with no filler metal added, then solution annealed to SA-312; our welded line runs on electric resistance welding, and the pipe is marked WLD. SA-312 sets the same certified minima for either route. Refinery transfer lines, superheater connections, and cracked gas headers take most of the output. European drawings call the same alloy 1.4912. We hold ISO 14001 and 45001 certifications and IBR and EIL approvals. Every heat is dispatched with an EN 10204 3.1 certificate, and we can supply material with the documentation required for conformity with the Pressure Equipment Directive 2014/68/EU.
Stainless Steel 347H pipe specifications define the applicable standards, dimensions, manufacturing forms, heat treatment, finishes, and available lengths. The table below outlines the key requirements for SS 347H pipe supply and identification.
| Parameter | Value |
|---|---|
| Applicable standard | ASTM A312 / ASME SA-312: Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes |
| Dimensional standard | ASME B36.19M |
| Size range | 1/8 inch NB to 10 inch NB |
| Schedule | SCH 5S, SCH 10S, SCH 40S and SCH 80S to ASME B36.19M; SCH 20S supplied to order as a manufacturer's schedule |
| Wall thickness | 1.24 mm to 12.70 mm, by NB and schedule |
| Length | Up to 12 metres; single random, double random, and cut lengths |
| Manufacturing form | Seamless (SML) and welded (WLD) to ASTM A312; our welded pipe is produced by electric resistance welding with no filler metal added |
| Section profile | Round, square, and rectangular hollow sections to order |
| Heat treatment | Solution annealed and quenched to SA-312 Table 2: 1050°C (1925°F) min hot finished, 1100°C (2000°F) min cold finished |
| Finish | Mill finish, pickled |
| End type | Plain end; bevelled to order |
Type 347H is an 18/10 Nb stainless steel stabilised with niobium, not titanium. Element limits for UNS S34709 pipe, taken from ASME SA-312, are given in the table below, with the niobium ratio behind them explained underneath.
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.04 to 0.10 |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | 0.030 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 17.0 to 19.0 |
| Nickel (Ni) | 9.0 to 13.0 |
| Niobium (Nb) | 8 x C min, 1.0 max |
| Iron (Fe) | Balance |
Niobium enters the ASTM A312 TP347H composition as a formula rather than a flat percentage, so a heat at the top of the carbon band carries more of it than a lean one. The element locks carbon into niobium carbide ahead of chromium carbide, which keeps grain boundaries clear of chromium depletion after exposure between 427°C and 816°C. SA-312 sets no separate tantalum limit on this grade.
The mechanical properties of SS 347H pipe are listed below in the table along with elongation, tensile, and yield strength.
| Property | Requirement |
|---|---|
| Tensile strength, min | 75 ksi (515 MPa) |
| Yield strength, min | 30 ksi (205 MPa) |
| Elongation in 50 mm, min, longitudinal | 35% |
| Elongation in 50 mm, min, transverse | 25% |
| Grain size, ASTM E112 (SA-312 para 11.4) | No. 7 or coarser |
SA-312 sets no reduced strength requirement for heavy wall seamless 347H pipe, so the 515 MPa minimum holds for every wall we produce.
SS 347H pipe equivalent grades help match the alloy across UNS, EN, and JIS designation systems. The table below lists the corresponding designations used for procurement, drawings, and material identification.
| Standard or System | Designation |
|---|---|
| UNS | UNS S34709 |
| Europe (EN / W.Nr) | 1.4912 / X7CrNiNb18-10 |
| Japan (JIS) | SUS 347HTP |
Two manufacturing routes and three section profiles cover the Stainless Steel 347H Pipes we make. Seamless and welded come first, then round, square, and rectangular.
Stainless Steel 347H Seamless Pipe starts as a solid billet, pierced over a mandrel and reduced with no longitudinal joint anywhere in the wall. Refinery and boiler circuits at the higher design pressures call for it, since no seam needs qualifying and no weld decay test applies.
SS 347H welded pipe starts from strip stock, which is formed into a round and seam-welded without filler metal, then solution annealed. ERW uses resistance heating and pressure, making it ideal for thin schedules.
The round section is the only profile ASME B36.19M covers, and it spans the whole 1/8 inch to 10-inch NB range under A312.
Square
Square hollow sections come off a separate box line, not the A312 route. We form SS 347H Square Pipe from 12 x 12 mm to 100 x 100 mm in lengths up to 12 metres for framework duty rather than pressure work.
Rectangular
Rectangular profiles run on that same box line, at 13 x 25 mm through 100 x 50 mm. Certification covers dimensions and grade chemistry, not an A312 pressure test.
The Stainless Steel 347H pipe sizes are specified by nominal bore, outside diameter, and wall thickness across different schedules. The table below provides standard dimensions for Sch 5S, 10S, 20S, 40S, and 80S pipes as per ASME B36.19M.
| Nominal Bore (mm) | Nominal Bore (INCH) | Outside Diameter (mm) | Sch-5S Thickness (mm) | Sch-10S Thickness (mm) | Sch-20S Thickness (mm) | Sch-40S Thickness (mm) | Sch-80S Thickness (mm) |
|---|---|---|---|---|---|---|---|
| 6 | 1/8 | 10.30 | 1.24 | 1.50 | 1.73 | 2.41 | |
| 8 | 1/4 | 13.70 | 1.65 | 2.00 | 2.24 | 3.02 | |
| 10 | 3/8 | 17.10 | 1.65 | 2.00 | 2.31 | 3.2 | |
| 15 | 1/2 | 21.34 | 1.65 | 2.11 | 2.30 | 2.77 | 3.75 |
| 20 | 3/4 | 26.70 | 1.65 | 2.11 | 2.55 | 2.87 | 3.91 |
| 25 | 1 | 33.40 | 1.65 | 2.77 | 3.00 | 3.38 | 4.55 |
| 32 | 1 1/4 | 42.20 | 1.65 | 2.77 | 3.00 | 3.56 | 4.85 |
| 40 | 1 1/2 | 48.30 | 1.65 | 2.77 | 3.00 | 3.68 | 5.08 |
| 50 | 2 | 60.30 | 1.65 | 2.77 | 3.00 | 3.91 | 5.54 |
| 65 | 2 1/2 | 73 | 2.11 | 3.05 | 4.00 | 5.16 | 7.01 |
| 80 | 3 | 88.9 | 2.11 | 3.05 | 4.00 | 5.49 | 7.62 |
| 100 | 4 | 114.3 | 2.11 | 3.05 | 4.50 | 6.02 | 8.56 |
| 125 | 5 | 141.3 | 2.77 | 3.4 | 5.00 | 6.55 | 9.53 |
| 150 | 6 | 168.3 | 2.77 | 3.4 | 6.35 | 7.11 | 10.97 |
| 200 | 8 | 219.1 | 2.77 | 3.76 | 6.35 | 8.18 | 12.7 |
| 250 | 10 | 273.1 | 3.4 | 4.19 | 6.35 | 9.27 | 12.7 |
Lengths go out single random, double random, or cut to a nominated figure, to 12 metres.
The SS 347H pipe weight chart provides the approximate weight per meter for different nominal bore sizes and pipe schedules. It helps in material estimation, handling, and transportation planning.
| Nominal Bore (mm) | Nominal Bore (INCH) | Sch-5S Weight (Kg/mt) | Sch-10S Weight (Kg/mt) | Sch-20S Weight (Kg/mt) | Sch-40S Weight (Kg/mt) | Sch-80S Weight (Kg/mt) |
|---|---|---|---|---|---|---|
| 6 | 1/8 | 0.28 | 0.33 | 0.37 | 0.47 | |
| 8 | 1/4 | 0.49 | 0.58 | 0.631 | 0.8 | |
| 10 | 3/8 | 0.63 | 0.74 | 0.845 | 1.1 | |
| 15 | 1/2 | 0.8 | 1 | 1.08 | 1.27 | 1.62 |
| 20 | 3/4 | 1.03 | 1.28 | 1.52 | 1.68 | 2.2 |
| 25 | 1 | 1.3 | 2.09 | 1.94 | 2.5 | 3.24 |
| 32 | 1 1/4 | 1.65 | 2.7 | 2.90 | 3.38 | 4.47 |
| 40 | 1 1/2 | 1.91 | 3.11 | 3.35 | 4.05 | 5.41 |
| 50 | 2 | 2.4 | 3.93 | 4.24 | 5.44 | 7.48 |
| 65 | 2 1/2 | 3.69 | 5.26 | 6.81 | 8.63 | 11.4 |
| 80 | 3 | 4.51 | 6.45 | 8.37 | 11.3 | 15.2 |
| 100 | 4 | 5.84 | 8.36 | 12.18 | 16.07 | 22.3 |
| 125 | 5 | 9.47 | 11.57 | 16.81 | 21.8 | 31.97 |
| 150 | 6 | 11.32 | 13.84 | 25.36 | 28.3 | 42.7 |
| 200 | 8 | 14.79 | 19.96 | 33.31 | 42.6 | 64.6 |
| 250 | 10 | 22.63 | 27.78 | 41.77 | 60.5 | 96 |
Four sectors generally use our 347H SS Pipe, and in each one, metal temperature rather than pressure decides the material.
Refinery piping is where Alloy 347H earns its specification. Hot transfer lines, catalytic reformer circuits and coker overheads hold metal at temperatures that sensitise unstabilised steel. Stabilisation blocks that and polythionic acid cracking during shutdown as well.
Boiler houses draw on 347H pipe for superheater and reheater connecting pipework and high-pressure steam mains, where creep behaviour rather than room-temperature strength sets the wall.
Cracked gas lines, hot process headers, and jacketed runs cycling through the carbide precipitation band all take this grade. Field-welded spools need no solution treatment afterwards, so a tie-in closes inside the shutdown window rather than waiting on a furnace.
The ammonia and urea plant runs reformer outlet piping and hot gas ducting in 347H. Cycling is severe there, and sections are thin, so scaling resistance and hot strength both have to hold.
We prepare Stainless Steel 347H Pipe for container and break-bulk despatch.
The stainless steel 347H pipe price is quoted at approximately ₹525–₹670 per kg (approximately US$5.50–7.00 per kg) against the day's nickel and niobium input cost, not from a standing list. Five variables move it: outside diameter, schedule or specified wall, manufacturing route, quantity, and certification scope. Seamless carries a premium over ERW.
Buyers return to Moonlight Tubes for certified material, approved grades and stock that ships on schedule. Every order is backed by documented quality, a wide size range and delivery commitments we hold to.
Stainless Steel 347H pipe is supplied to ASTM A312 / ASME SA-312, dimensioned to ASME B36.19M.
SS 347H pipe runs from 1/8 inch NB to 10 inch NB in SCH 10S, 20S, 40S and 80S, with SCH 5S from 1/2 inch NB upwards, giving walls of 1.24 mm to 12.70 mm, in lengths up to 12 metres.
Both are available, and SA-312 sets the same certified minima for either route. Seamless goes to the higher-pressure circuits and is welded to everything else. Our welded pipe is made by electric resistance welding, certified and marked WLD under SA-312.
Stainless Steel UNS S34709 Pipe is the American designation, matched by 1.4912 or X7CrNiNb18-10 in Europe and SUS 347HTP in Japan.
Yes. Field welding needs no post-weld solution treatment. Niobium has already tied up the carbon that would precipitate as chromium carbide in the heat-affected zone, so the joint keeps its corrosion resistance. Stress relief is a separate question, set by restraint and wall thickness.
Specify 347H pipe where the duty is sustained heat and creep governs the wall. A 316 line answers chloride and acid service instead.