Key American Standards for TP321 Stainless Steel Tubing (ASTM/ASME)

TP321 stainless steel tubing is a titanium-stabilized austenitic grade, with UNS S32100 as its standard UNS designation and TP321/TP321H as the common ASTM grade labels for industrial use. TP321H is the high-temperature variant optimized for creep resistance, making both grades a go-to choice for medium-to-high temperature and corrosion-prone applications. Below are the most widely adopted ASTM/ASME standards for this tubing in practical industrial use, with clear application scenarios and core technical requirements for easy selection and compliance.

TP321/TP321H Stainless Steel Tubing

ASTM A312 / ASME SA312

Standard	ASTM A 312/ ASME SA 312/ ASTM A213 / ASME SA 213 / ASTM A263 / ASME SA 263 / AMS 5557 / AMS 5570
Size	1/2" to 48 " NB
Wall Thickness	0.1 To 60 mm
Standard	DIN, JIS, AMS, GB, AISI, ASME, ASTM, EN, GOST
Surface Finish	Bright, Cold Finish, Annealing, Polished, Pickling
Schedule Thickness	SCH 5, SCH10, SCH 40, SCH XXS, SCH XS, SCH 160
Types	Round, Seamless, ERW, Welded, EFW
Manufacturing Technology	Hot / Cold Formed
Why Choose US?	1. MTC Mill Test Certificate (MTC) EN 10204 – 3.1 2. Quality Control Certificate 3. Certificate of Origin 4. ISO9001 5. Third-party inspection availability (SGS/TÜV)

Core Application

The most universal standard for TP321 seamless and welded stainless steel tubing, applicable to nearly all industrial scenarios involving medium-to-high temperature (400~800℃) and general corrosion conditions. It's the primary standard for TP321 tubing in petrochemical, power generation, metallurgy and mechanical processing industries, covering both process piping and fluid transfer lines.

Key Requirements

Covers seamless tubing, as well as ERW (Electric Resistance Welded) and EFW (Electric Fusion Welded) welded tubing, with nominal sizes ranging from ½" NB to 30" NB and wall thicknesses from Sch5 to XXS (per ASME B36.19 dimensional specs).

Mandatory intergranular corrosion testing in accordance with ASTM A262 to ensure no serious intergranular corrosion occurs after welding (no post-weld solution annealing required).

TP321H grade is specially specified for high-temperature creep service, with strict controls on mechanical properties retention at 400~800℃.

All tubing must pass hydrostatic pressure testing and surface quality inspection to meet industrial pressure and corrosion resistance demands.

ASTM A213 / ASME SA213

Core Application

The core standard for seamless TP321 tubing used in boilers, superheaters and heat exchangers, designed exclusively for high-temperature pressure-bearing heat transfer components. It's the top choice for TP321/TP321H tubing in power plant steam boilers, petrochemical shell-and-tube heat exchangers and high-temperature reactor heat transfer bundles.

Key Requirements

Restricted to seamless tubing only (no welded variants), with strict requirements on high-temperature hot strength and oxidation resistance for service in steam and high-temperature thermal fluid environments.

TP321H is the dominant grade for this standard; minimum yield strength ≥205 MPa and minimum tensile strength ≥520 MPa (per ASTM A370 mechanical testing methods).

Explicit heat treatment specifications for the tubing to optimize titanium carbide precipitation and eliminate intergranular corrosion risks at high temperatures.

Tight tolerances on outer diameter and wall thickness to ensure fit and heat transfer efficiency in heat exchanger and boiler tube bundle assemblies.

ASTM A269 / ASME SA269

Core Application

A standard for TP321 seamless and welded tubing for general low-to-medium pressure service, ideal for applications with strict requirements on surface finish and cleanability, as well as mild corrosion conditions. It's widely used in food and pharmaceutical processing, clean HVAC systems, light chemical engineering and sanitary fluid transfer lines.

Key Requirements

Covers both seamless and welded (ERW/EFW) tubing, with high dimensional precision and strict surface quality controls (polished bright surface tubing is available for sanitary applications).

Optimized for low-to-medium pressure working conditions; intergranular corrosion performance complies with ASTM A262, with no special high-temperature creep requirements.

Tight tolerance control on inner and outer diameters to ensure smooth fluid flow and easy connection with fittings in clean piping systems.

All tubing undergoes non-destructive testing (NDT) to eliminate surface and internal defects that could affect clean service performance.

Supplementary Key Industrial Specifications

Dimensional Standard: ASME B36.19 – Defines the unified outer diameter, wall thickness (Sch series) and length for stainless steel tubing, the mandatory dimensional reference for all above standards.

Testing Standard: ASTM A262 – The exclusive intergranular corrosion testing standard for TP321 tubing, required by all core ASTM/ASME standards for this grade.

Mechanical Testing: ASTM A370 – Specifies the test methods for tensile strength, yield strength, hardness and impact resistance of TP321 tubing.

N	NPS	OD		Sch40S
N	NPS	in	mm	in	mm
6	1/8	0.405	10.3	0.068	1.73
8	1/4	0.54	13.7	0.088	2.24
10	3/8	0.675	17.1	0.091	2.31
15	1/2	0.84	21.3	0.109	2.77
20	3/4	1.05	26.7	0.113	2.87
25	1	1.315	33.4	0.133	3.38
32	1 1/4	1.66	42.2	0.140	3.56
40	1 1/2	1.9	48.3	0.145	3.68
50	2	2.375	60.3	0.154	3.91
65	2 1/2	2.875	73	0.203	5.16
80	3	3.5	88.9	0.216	5.49
90	3 1/2	4	101.6	0.226	5.74
100	4	4.5	114.3	0.237	6.02
125	5	5.563	141.3	0.258	6.55
150	6	6.625	168.3	0.280	7.11
200	8	8.625	219.1	0.322	8.18
250	10	10.75	273.1	0.365	9.27
300	12	12.75	323.9	0.375	9.52
350	14	14	355.6	0.375	9.52
400	16	16	406.4	0.375	9.52
450	18	18	457	0.375	9.52
500	20	20	508	0.375	9.52
550	22	22	559
600	24	24	610	0.375	9.52