AISI 304 Round Bars

AISI 304 hot rolled round bar is general purpose 18/8 stainless bar, 16 to 125 mm diameter, used for shafts, fittings and machined parts.

16 to 125 mm Austenitic stainless steel Made to order

HOT ROLLED ROUND BARS

AISI 304 hot rolled round bar

AISI 304 hot rolled round bar is round bar rolled in the general purpose austenitic stainless steel, the 18/8 combination of chromium and nickel with no deliberate molybdenum. The chromium forms the thin passive oxide film that keeps the surface from rusting in air, water and most food and dairy service, and the nickel holds the austenitic structure, which leaves the bar non-magnetic in the annealed condition and tough at low temperature. It is used instead of 316 where the service carries no chlorides, since the molybdenum 316 adds is paid for only against pitting in salt or brine. It is used instead of 304L where the section is machined rather than welded, the higher carbon of 304 giving a little more strength. Laxcon Steels rolls the bar to order.

The bar is supplied solution annealed, heated and cooled fast so the carbides return into solution and the structure is left soft and corrosion resistant, and it ships black as rolled, spot ground or fully ground. ASTM A276 sets the annealed minima at 515 MPa tensile strength and 205 MPa yield strength. It cannot be hardened by heat treatment and takes strength only from cold work, which also makes it work harden under the tool, so machining calls for sharp edges and a steady feed. It welds readily, though slow cooling through about 450 to 850 C sensitises the weld zone, meaning chromium carbides form at the grain boundaries and leave them open to attack; a solution anneal afterwards reverses that. Typical uses are pump and valve shafts, machined flanges and couplings, dairy and food plant parts, and forging stock.

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 18.0 to 20.0, nickel 8.0 to 10.5 and nitrogen 0.1 maximum.

SPECIFICATION

AISI 304 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 304 (304, SS 304, SUS 304, 1.4301)
Family: Austenitic stainless steel
Supply: Made to order in this grade; every published size of the form

Composition of AISI 304

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	18.0	20.0
Nickel	Ni	8.0	10.5
Nitrogen	N		0.1

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

Equivalents of AISI 304

Standard	Designation
UNS	S30400
EN number	1.4301 (X5CrNi18-10)
JIS	SUS 304

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 304 runs from 18.0 at the specified minimum chromium, molybdenum and nitrogen to 21.6 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 304 hot rolled round bar

An enquiry for this bar is complete when it states the grade and governing standard (AISI 304 to ASTM A276 or EN 10088-3), the condition and finish (black as rolled, spot ground or fully ground), the diameter with its tolerance class to ASTM A484 or EN 10060, the cut length within the 8 metre maximum, the quantity, the certificate type to EN 10204, and any test to be reported, such as the ultrasonic examination or PMI confirmation of grade.