ASTM A312 TP347 stainless steel tubes for pyrolysis furnace

Why do stainless steel tubes in pyrolysis furnaces still suffer from coking, intergranular corrosion, or premature creep failure under extremely high-temperature conditions?The key lies in whether the microstructural stability of the material and its heat treatment process are truly designed for long-term service in carbon-rich and sulfur-containing environments.

 

ASTM A312 TP347 Stainless Steel Tube Supplier

GNEE has extensive experience supplying overseas large-scale petrochemical projects and is well-versed in ASME/ASTM standards as well as 3.2 inspection and certification procedures. We specifically provide high-performance ASTM A312 TP347 stainless steel pipes for pyrolysis furnace applications.

 

TP347 stainless steel high-temperature pipes contain 17–19% Cr and 9–13% Ni, and are stabilized with Nb (typically Nb content ≥ 10 times the carbon content). This effectively prevents sensitization and ensures excellent resistance to intergranular corrosion. This is particularly critical in environments encountered during shutdown and maintenance cycles of petrochemical units, where polythionic acid stress corrosion cracking is likely to occur.

In terms of high-temperature performance, TP347 stainless steel pipes undergo solution annealing (≥1040°C, followed by rapid cooling), along with optional stabilization heat treatment (850–900°C). This enables the material to maintain structural integrity and effectively resist grain boundary degradation during long-term service in the 600–900°C temperature range.

 

To address the challenge of coking (carbon deposition), our TP347 stainless steel pipes undergo specialized surface treatment processes, with strict control of surface roughness (Ra ≤ 0.8 μm). This effectively reduces nucleation sites for coke formation, lowering the fouling rate by approximately 15%–25%, thereby significantly improving heat transfer efficiency and extending the operating cycle between decoking shutdowns.

 

ASTM A312 TP347 Stainless Steel Tubes Specification

Standard	ASTM A312 / ASME SA312, ASTM A213 / ASME SA213
Type	Seamless (SMLS) / Welded (WLD)
Outer Diameter (OD)	6.0mm – 630.0mm (1/8" to 24")
Wall Thickness (WT)	0.5mm – 40.0mm (SCH 5S to SCH 160/XXS)
Length	6.0m, 12.0m, or customized up to 18m
Non-Destructive Test	Ultrasonic (UT) + Eddy Current (ET) + Hydro-test
Certification	EN 10204 3.1 / 3.2 (BV, SGS, TUV inspection)

 

A312 TP347 Composition Analysis

ASTM A312		Mn	Si	C	Ni	P	S	Cr	Mo	N
TP347	min.	-	-	-	9.0	-	-	17.0	2.00	-
	max.	2.0	1.00	0.08	13.0	0.045	0.030	20.0	3.00	-

 

ASTM A312 SS 347 stainless steel Pipe Mechanical Characteristics

AISI	Tensile Strength minimum (MPa)	Yield Strength 0.2% Proof minimum (MPa)	Elongation minimum (% in 50mm)	Hardness
				Rockwell B (HR B) maximum	Brinell (HB) maximum
347	515	205	40	95	201

 

ASTM A312 pipe Outside Diameter Tolerance(mm)

Standard	Outside Diameter Tolerance(mm)		Thickness Tolerance		Length Tolerance (mm)
ASTM A312	[10.29~48.26]	+0.4/-0.8	10.3~73	+20% / -12.5%	+6/-0
			88.9~457 T/D≤5%	+22.5%/-12.5%
	(48.26~114.30]	±0.80	88.9~457 T/D>5%	+15%/-12.5%
	(114.30~219.08]	+1.6/-0.8	508above T/D<5%	+22.5%/-12.5%
	(219.08~457.20]	+2.4/-0.8	508above T/D>5%	+15%/-12.5%

 

What is the difference between TP347 and TP321?

Both TP347 and TP321 are stabilized austenitic stainless steels designed to prevent intergranular corrosion in high-temperature environments; specifically, TP321 is stabilized through the addition of titanium, while TP347 achieves stabilization through the addition of niobium. TP347 withstands temperatures up to 1500°F, making it particularly suitable for welding applications involving thick-walled components; in contrast, TP321 is frequently selected for cost-sensitive applications situated in environments characterized by high temperatures and moderate corrosive conditions.

 

What is the maximum service temperature for TP347?

Oxidation Resistance: It can handle continuous service up to 815°C (1500°F).
Pressure Service: For pressure-bearing applications (ASME Code), it is typically used up to 650°C (1200°F), beyond which the "H" grade (TP347H) is recommended for better creep performance.

 

High-Temperature Service Requirements (Furnace Specific)

For pyrolysis furnaces, standard ASTM A312 requirements are often supplemented by tighter controls on grain size and corrosion testing.

Feature	Requirement	Standard Reference
Grain Size	ASTM No. 7 or coarser (optimized for creep)	ASTM E112
Intergranular Corrosion	Practice E (Strauss Test) - No cracks	ASTM A262
Heat Treatment	Solution Annealed at min. 1040°C + Rapid Quench	ASTM A312
Surface Finish	Inside surface smoothness Ra < 0.8μm (optional)	Customer Spec
Hydrostatic Test	100% Mandatory (P=2St/D)	ASTM A999

 

Note：EN 10204 3.1 or 3.2: For refinery projects, a 3.1 certificate is typically provided; for critical core components, a 3.2 certificate-involving on-site inspection by a third party such as BV or SGS-is often required.
Standard Compliance: In addition to ASTM A312, compliance with ASME SA312 (Boiler and Pressure Vessel Code) is sometimes also required.

 

All our stainless steel seamless tubes are packaged in accordance with international standards to prevent any potential damage or loss. By default, we bundle the finished tubes in batches using thick woven plastic bags.
For specialized tubes that are particularly susceptible to dirt, scratches, compression, or damage during handling, we recommend the use of wooden crates for protection.