A240 SS347H Steel Plate Applications & Ordering Guide

ASTM A240 / ASME SA240 Type 347H (UNS S34709) stainless steel plate is specified for elevated-temperature pressure equipment where niobium-stabilized austenitic chemistry and the H-grade carbon band support creep strength and resistance to intergranular attack after welding. This applications page explains where Type 347H is used, what service conditions drive the selection, and which certificate details belong on the purchase order. Gangsteel supplies A240/SA240 347H plate with EN 10204 mill test certificates.

This page is a standalone technical article. For the primary overview on the original URL, see ASTM A240 / ASME SA240 Type 347H primary specification page.

Typical Applications and Service Conditions

Type 347H plate is ordered for fired heaters, reformer and furnace tubing adjacent platework, high-temperature process piping spools, heat-exchanger shells and channels, and pressure-vessel components that see continuous or cyclic service in the creep range. Refinery, petrochemical, and power-generation projects commonly list 347H when the design temperature and weld-exposure rules exceed what standard Type 347 or 304H can justify without stabilization.

Service drivers include long-term exposure roughly in the 540-750 deg C band (project-specific), oxidizing process atmospheres, and post-weld heat cycles that would sensitize unstabilized 18Cr-8Ni grades. Niobium (columbium) binds carbon as NbC/Nb(C,N), so chromium remains available for the passive film. The H-grade carbon window (0.04-0.10%) supports higher allowable stresses in ASME Section II Part D creep tables relative to low-carbon 347L-type chemistries.

Industry Use Cases

Oil refining and petrochemical: heater tubesheet-adjacent plate, transfer-line shells, catalytic reformer and steam-methane reformer related fabrications where drawings call SA240/A240 347H. Power and HRSG: high-temperature ducting, superheater-related casings, and boiler components under ASTM/ASME stainless plate rules. Chemical process: reactors and columns with intermittent high-temperature upsets. Always match the MTC grade mark to the calculation sheet; do not treat 347, 321H, or 304H as automatic substitutes.

Chemical Composition - Heat Analysis (ASTM A240 Type 347H)

Heat / cast analysis unless noted. Product analysis tolerances apply where A240/A240M defines them. Accept material against the ordered edition and the mill test certificate.

Element	Min %	Max % / requirement
C	0.04	0.10
Mn	-	<=2.00
Si	-	<=0.75
P	-	<=0.045
S	-	<=0.030
Cr	17.0	19.0
Ni	9.0	13.0
Nb (Cb)	8xC	1.00

Mechanical Properties - Annealed Plate (ASTM A240)

Room-temperature tensile properties for annealed plate/sheet. Confirm thickness, specimen orientation, and any supplementary hardness, corrosion, or elevated-temperature test requirements on the PO.

Property	Requirement
Tensile strength, min	515 MPa (75 ksi)
Yield strength (0.2% offset), min	205 MPa (30 ksi)
Elongation in 50 mm, min	40%
Hardness, max	201 HBW
Delivery condition	Solution annealed (mill MTC)

Related / Near-Equivalent Grades

Near-equivalents are for cross-reference only. They are not automatic code substitutes. Substitution requires engineer approval and matching certificate scope.

System	Grade	Note
ASTM / ASME	A240 / SA240 Type 347	Lower C max; not a drop-in for H creep service
EN	1.4961 / X6CrNiNb18-10H family	European H-grade counterpart - confirm edition
UNS	S34709	347H designation
JIS	SUS347H	Confirm plate product standard
Related on site	Type 321H / 304H	Different stabilizer / C strategy

Frequently Asked Questions

Where is ASTM A240 Type 347H typically applied?

Type 347H is applied in elevated-temperature pressure equipment: fired-heater and reformer fabrications, high-temperature heat-exchanger shells, process piping spools, and power/HRSG components where the design documents require Nb-stabilized austenitic plate with the H-grade carbon band. Match the MTC marking to the drawing. Primary overview: A240 / SA240 Type 347H.

What service conditions push a project from 347 or 304H toward 347H?

Design temperature in the creep range, long hold times after welding, and oxidizing process gas favor 347H. Type 347 without the H carbon floor may lack the same elevated-temperature allowables; 304H lacks Nb stabilization and is more prone to sensitization in the same thermal history. The project engineer owns the final selection against ASME/EN allowables.

Can Type 321H or Type 304H replace 347H on an applications drawing?

Not without redesign and written approval. 321H is Ti-stabilized; 304H is unstabilized high-carbon. Creep strength, sensitization resistance, and welding procedure qualifications differ. Commercial swap to cut cost creates non-conformance at inspection when the dossier names 347H.

What fabrication notes matter for 347H in heater and vessel shops?

Use approved WPS/PQR packages for the thickness and filler (often Nb-bearing or matching 347/347H consumables), control interpass temperature, and preserve heat-number traceability on cut pieces. Solution-annealed delivery is the baseline; any additional stabilizing anneal must be stated on the PO if the project specification requires it.

What certificate and marking should an applications PO demand for 347H?

EN 10204 3.1 is standard; 3.2 when a purchaser-appointed inspector witnesses tests. The MTC should show heat analysis (including Nb vs 8xC), tensile results, solution-anneal condition, and heat number. Dual marking to ASME SA240 347H is common when the vessel code is ASME.

How should I RFQ A240/SA240 347H plate from Gangsteel for a project?

Send ASTM A240 or ASME SA240 Type 347H, thickness x width x length (or nesting list), quantity, solution-annealed condition, optional PMI/UT, certificate type, destination, and any dual-mark needs. Note the end use (heater, exchanger, piping) when special flatness or cut-to-size packaging is required.

Ordering and Mill Certificates

State grade ASTM A240 / ASME SA240 Type 347H (UNS S34709), dimensions, quantity, delivery condition, optional NDT/PMI, and certificate (EN 10204 3.1 standard; 3.2 when third-party inspection is ordered). Gangsteel supplies export plate and related products with mill test certificates. Contact Gangsteel for stock and mill production RFQs.