AISI 321 Round Bars

AISI 321 hot rolled round bar is a titanium-stabilised austenitic bar for welded parts that run hot, such as furnace and exhaust components.

16 to 125 mm Austenitic stainless steel Made to order

HOT ROLLED ROUND BARS

AISI 321 hot rolled round bar

AISI 321 hot rolled round bar is an austenitic stainless bar rolled from a chromium nickel grade to which titanium is added. Titanium has a stronger pull on carbon than chromium does, so the carbon is tied up as titanium carbide and the chromium stays dissolved in the metal where it does the corrosion work. Without that addition, an AISI 304 bar held between about 425 and 870 degrees Celsius, by welding or by service, loses chromium to carbides at the grain boundaries and is then attacked along them, a change known as sensitisation. AISI 304L answers the same problem by keeping carbon low, but it is limited at temperature; 321 keeps the ordinary carbon limit and neutralises it, so the bar can be welded and then worked hot for years. AISI 347 does the same job with niobium.

The bar is supplied solution annealed, and because the carbon is already tied to titanium the anneal has less to undo than in 304. Annealed 321 is non-magnetic, does not harden by heat treatment and strengthens only by cold work, with ASTM A276 minima of 515 MPa tensile and 205 MPa yield. It turns much as 304 does, with a firm feed and sharp edges, though the titanium carbides are abrasive and shorten tool life. Welding takes no preheat, and the filler is usually the niobium-stabilised type, because titanium does not carry across the arc. Round bar in this grade is machined into furnace and heat exchanger parts, expansion joint and bellows hardware, refinery flanges and fittings, and aircraft exhaust components.

Composition limits in weight percent are carbon 0.08 maximum, manganese 2.0 maximum, sulphur 0.03 maximum, phosphorus 0.045 maximum, silicon 0.75 maximum, chromium 17.0 to 19.0, nickel 9.0 to 12.0, nitrogen 0.1 maximum and titanium 0.7 maximum.

SPECIFICATION

AISI 321 hot rolled round bar supply conditions

Size range: 16 mm - 125 mm (5/8" - 5")
Length: Up to 8 metres
Tolerances: ASTM A484, EN10060
Heat treatment: Solution annealing
Grade: AISI 321 (321, SUS 321, 1.4541, S32100)
Family: Austenitic stainless steel
Supply: Made to order in this grade; every published size of the form

Composition of AISI 321

Element	Symbol	Minimum %	Maximum %
Carbon	C		0.08
Manganese	Mn		2.0
Sulphur	S		0.03
Phosphorus	P		0.045
Silicon	Si		0.75
Chromium	Cr	17.0	19.0
Nickel	Ni	9.0	12.0
Nitrogen	N		0.1
Titanium	Ti		0.7

Composition, weight percent, balance iron. From the Laxcon Steels grade reference.

Equivalents of AISI 321

Standard	Designation
UNS	S32100
EN number	1.4541 (X6CrNiTi18-10)
JIS	SUS 321

Equivalence means nearest counterpart, not identity: each standards body sets its own composition window, so the limits of the standard named on the order govern.

Pitting resistance

The pitting resistance equivalent number of AISI 321 runs from 17.0 at the specified minimum chromium, molybdenum and nitrogen to 20.6 at the maxima, computed as PREN = Cr + 3.3Mo + 16N (International Molybdenum Association). It ranks resistance to chloride pitting against other austenitic and duplex grades and nothing else: it does not predict crevice corrosion, stress corrosion cracking or service life. The pitting resistance reference carries the full table.

Governing standards

EN 10088-3: Stainless steels: technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products for general purposes. Composition, heat treatment condition and mechanical properties per grade.
EN 10060: Hot rolled round steel bars for general purposes: dimensions and tolerances on shape and dimensions.
ASTM A276/A276M: Stainless steel bars and shapes: composition, condition, mechanical properties and finish designations for hot-finished and cold-finished bar.
ASTM A484/A484M: General requirements for stainless steel bars, billets and forgings: permissible variations in dimensions, straightness, weight and length, and the test and marking requirements every bar order inherits.
ASTM A479/A479M: Stainless steel bars and shapes for use in boilers and other pressure vessels: the bar specification a pressure-part drawing calls for.
ASTM A314: Stainless steel billets and bars for forging.
NACE MR0175 / ISO 15156: Materials for use in H2S-containing environments in oil and gas production: the sour-service limits on hardness and condition.
EN 10204: Metallic products, types of inspection documents: the 2.2 test report and the 3.1 and 3.2 inspection certificates a purchase order can call for.

Weight per metre

Diameter (mm)	kg per metre	Metres per tonne
16	1.59	629.5
17	1.79	557.6
18	2.01	497.4
19	2.24	446.4
20	2.48	402.9
21	2.74	365.4
22	3.00	333.0
23.2	3.34	299.4
24	3.57	279.8
25	3.88	257.9
26	4.19	238.4
27	4.52	221.1
28	4.86	205.6
30	5.58	179.1
32	6.35	157.4
34	7.17	139.4
36	8.04	124.4
37	8.49	117.7
38	8.96	111.6
40	9.93	100.7
42	10.95	91.4
45	12.57	79.6
47	13.71	73.0
48	14.30	69.9
50	15.51	64.5
53	17.43	57.4
56	19.46	51.4
57.5	20.52	48.7
60	22.34	44.8
63	24.63	40.6
66	27.03	37.0
67.5	28.27	35.4
70	30.40	32.9
73.5	33.52	29.8
75	34.90	28.7
77.5	37.27	26.8
80	39.71	25.2
83	42.75	23.4
85	44.83	22.3
88	48.05	20.8
90	50.26	19.9
93	53.67	18.6
95	56.00	17.9
98	59.59	16.8
100	62.05	16.1
105	68.41	14.6
106	69.72	14.3
110	75.08	13.3
115	82.06	12.2
120	89.35	11.2
125	96.95	10.3

Density 7.90 g/cm³, diameter squared x 0.006205. Sizes are the published range at the nominal diameters shown.

Ordering AISI 321 hot rolled round bar

An enquiry for this grade in this form states the grade and the governing standard, for example AISI 321 to ASTM A479 or EN 10088-3, the condition as rolled, spot ground or fully ground, the diameter with the tolerance to ASTM A484 or EN 10060, the cut length, the quantity, the test certificate type to EN 10204, and any test called for, such as ultrasonic testing or PMI confirmation of the grade. Laxcon Steels rolls the bar to order.