ASTM A335 vs. ASTM A213: An Overview

ASTM A335 vs ASTM A213 is not a choice between two steels. For every Cr-Mo pair the two documents print one chemistry, because the pair carries one UNS number. What changes is the product: A335 pipe is ordered by NPS and schedule, A213 tube by outside diameter and minimum wall, usually to 5 in. The difference that returns a shipment is smaller and harder to see, and it sits in a hardness cap written on two different scales.

 

ASTM A335 vs A213

The difference between A335 and A213 comes down to eleven lines, and only four of them decide an order: the wall basis, the hardness cap, the test set, and the code that consumes the document.

Table 1 - ASTM A335 vs A213, side by side. Rows 3, 7 and 8 are the ones that come back as rejections.

Item	ASTM A335	ASTM A213
Product form	Seamless pipe, nominal or minimum wall	Seamless tube, minimum wall unless average is ordered
Function	Pressure piping between equipment	Heat-transfer surface inside it
Size basis	NPS and schedule to ASME B36.10	Outside diameter and wall thickness
Grade system	P prefix, ferritic alloy only	T prefix ferritic, TP prefix austenitic
Chemistry of a pair	One UNS number, one table	Same UNS number, same table
Tensile and yield floors	Identical for a paired grade, because the UNS number is shared
Hardness cap	89 HRB; 250 HBW (25 HRC) for 91 and 92	163 HBW for T11 and T22, 250 HBW for T91
Mechanical tests	Tension, flattening, hardness or bend	Tension, hardness, flattening, flaring
Pressure and electric test	Hydrostatic on each length, plus NDE	One of the two, at the mill's option
Heat treatment	After forming, separately	After forming, separately; TP347HFG cold finished
Code that consumes it	ASME B31.1 power piping	ASME Section I boilers, Section VIII exchangers

A335 pipe vs A213 tube is a comparison of form, not of steel. Both are seamless in the current text: ASTM A335 seamless pipe and ASTM A213 seamless tube are the only forms either document covers, which is why a mill that offers "A213 welded" is quoting a different specification entirely.

SA213 vs SA335 is only the ASME adoption of these two documents into Section II Part A. The requirements do not change; what is added is the code's own allowable stress, external pressure and joint efficiency rules.

 

What Each Order Can Actually Cover

A quotation is written against an envelope, and the two envelopes do not overlap as much as the grade tables suggest. An A213 boiler tube order and an ASTM A213 heat exchanger tube order sit in one of them; a chrome moly pipe order under A335 sits in the other.

Table 2 - Commercial supply range for each document. Ranges are what we quote, not standard limits.

Item	ASTM A335 pipe	ASTM A213 tube
Size	NPS 1/8 to 24 (10.3 to 610 mm)	3.2 to 127 mm OD, 5 in usual
Wall	SCH 10 to XXS, to 100 mm by agreement	0.4 to 12.7 mm, minimum or average
Length	5.8 m, 11.8 m, double random	Straight to 25 m, or U-bent
Ends	Plain or beveled	Plain, or prepared for welding after bend
U-bend	Not a product form; bending is fabrication	Supplied bent, with extrados wall recorded
Finish	As rolled, machined, pickled	Pickled, bright annealed, shot blasted
Documents	EN 10204 3.1 or 3.2, heat treatment chart	3.1 or 3.2, plus electric test report per length

A213 minimum wall is the field most often misread. When the order names a floor, the mill targets an average about 11 % above it so the thinnest point still clears the figure after the permitted minus tolerance; a 0.120 in call-off arrives near 0.133 in. Written as a nominal figure instead, the same number can be delivered below itself, and the design pressure no longer holds.

A213 tube sizes stop where they do for a reason: above 127 mm OD the item is a header or a large pipe, and a boiler tube that size is not a tube any more. The scope allows other diameters if every other requirement is met, but once the item reaches 168.3 mm it is an ASTM A335 high temperature pipe, and it is quoted from that document.

 

P22 vs T22: One Heat, Two Acceptance Routes

P22 vs T22 is not a metallurgical question. Pipe and tube versions of the same grade carry the same UNS number, so the ladle analysis that satisfies one satisfies the other.

Table 3 - Paired grades and their shared UNS number. Check the UNS column before arguing about chemistry.

Grade pair	UNS	Nominal composition	Common duty
P5 / T5	K41545	5Cr-0.5Mo	Refinery furnace, sulfidation
P9 / T9	S50400	9Cr-1Mo	High-temperature oxidation
P11 / T11	K11597	1.25Cr-0.5Mo	Superheater, steam header
P22 / T22	K21590	2.25Cr-1Mo	Main steam, hydroprocessing
P91 / T91	K91560	9Cr-1Mo-V-Nb	Supercritical boiler, main steam
P92 / T92	K92460	9Cr-2W-0.5Mo-V-Nb	Ultra-supercritical boiler

ASTM A335 P22 and ASTM A213 T22 are the same analysis, and so are ASTM A335 P91 and ASTM A213 T91, at 585 MPa tensile and 415 MPa yield on both sides. Pages that claim a small difference in carbon, manganese or silicon between a pair are describing a table that does not exist.

ASTM A213 hardness is where the agreement ends. A335 caps its low-alloy grades at 89 HRB; A213 caps T11 and T22 at 163 HBW, which is roughly 84 HRB, and T91 at 250 HBW, the same ceiling A335 writes as 25 HRC. Run a 2.25Cr-1Mo heat at 88 HRB and you are inside one ceiling, above the other, at about 176 HBW. The same heat ships on an A335 certificate and is rejected on an A213 one, and no re-test fixes it, because the remedy is a re-temper.

 

Test Differences

Most comparisons print the same sentence about testing, and most of them print it wrong. Flattening is not an A213 privilege; the A335 flattening test is written into that document, and so is a bend test.

Table 4 - Mechanical and pressure tests. Only the flaring row is one-sided.

Test	ASTM A335	ASTM A213	What it catches
Tension	Per lot	Per lot	Strength and elongation below the grade floor
Hardness	Or bend test	Required	A tempering run that stopped early
Flattening	Required	Required	Laminations and wall eccentricity
Flaring	Not required	Required	Whether the tube survives expansion into a tubesheet
Bend	Alternative to hardness	Not required	Ductility of the pipe body
Hydrostatic or electric	Each length	Each tube	Through-wall defects and leaks

The A213 flaring test is the one that matters commercially, because expanding a tube end into a tubeplate is the first thing that happens on site. A pipe that never saw a flaring test can be perfectly sound and still split at the expander, and no amount of ultrasonic examination predicts it.

The bend test runs the other way: A335 lets it stand in for the hardness check, so an A335 certificate with no hardness value on it still conforms.

 

ASTM A335 and A213 Alloy Pipe factory

Send the drawing line, and we will tell you which document it belongs to

If the line already names one of the two, quote it as written and we will confirm the wall basis and test set against it. If it names both, we will say which one governs before pricing.

Standard and grade, P or T along with the number

Size: NPS and schedule, or OD and wall in mm

Nominal, minimum or average wall

Straight length, or U-bend radius and leg

Design code and metal temperature

Quantity, destination port and certificate level

Send the line for review

 

FAQ

A213 vs A335: which one belongs on my drawing?

Name the document that matches what the item does. A part that sheds heat inside a boiler or a shell goes under the tube document; a run that carries steam between equipment goes under the pipe document. Writing both numbers on one line is what stalls a bid.

 

Can a P22 pipe stand in for a T22 tube if the wall is heavy enough?

Only with written approval from the design engineer. The tube document demands an expansion test the pipe document never performs, so that property cannot be evidenced from a pipe certificate. Quote the substitution as a deviation, never as an equivalent.

 

Is A213 ever welded?

No. The title itself says seamless. Welded tube for comparable duty sits in A249 or A688, and welded alloy pipe in A691. If a mill offers a welded item against an A213 line, the offer is against a different document.

 

Does SA213 differ from A213?

The technical content is the same document adopted by ASME. What changes is what the code does with it: allowable stress curves, external pressure rules and joint efficiency. Buyers comparing an ASTM quote with an SA quote are usually comparing documentation, not steel.

 

Why are per-tonne quotes for T22 and P22 so far apart?

Because the two lines are priced on different thicknesses. Tube is quoted against a guaranteed floor plus an expansion test on every lot; pipe is quoted against a schedule figure. Convert both to kilograms at the same design thickness before comparing money.