AISI 304 Hex Bars

AISI 304 hexagonal bright bar is cold drawn austenitic stainless steel used for machined fasteners, valve parts and pipe fittings.

15 to 52 mm Austenitic stainless steel Made to order

HEXAGONAL BRIGHT BARS

AISI 304 hexagonal bright bar

AISI 304 hexagonal bright bar is an austenitic stainless steel bar drawn cold to a hexagon section, supplied from 15 to 52 mm across flats, which is 5/8 to 2 inch. Chromium and nickel give the grade its corrosion resistance in water, steam, food acids and ordinary outdoor air. The hexagon is chosen where a finished part must be held by a spanner, or turned from a blank that already carries its flats. Against 304L the carbon limit is higher, so the bar is a little stronger but less settled after welding. Against 316 there is no deliberate molybdenum, so it resists chloride pitting less well in salt water and de-icing salts. Against free machining 303 it cuts more slowly, and welds and resists corrosion better.

The bar is drawn from hot rolled material that has been annealed and pickled, so the drawn surface is work hardened and carries more strength than the annealed minima of 515 MPa tensile and 205 MPa yield in ASTM A276. Cold work also leaves the bar faintly magnetic, although 304 is non-magnetic once fully annealed. Heat treatment cannot harden it, and a solution anneal, meaning a reheat and a quick cool, only softens it again and restores corrosion resistance. The grade work hardens under a dull tool, so machining wants sharp tooling, a firm feed and coolant. It welds by the common arc processes, usually with a 308L filler. Typical parts are nuts and bolt blanks, valve and pump fittings, dairy and food plant fittings, and instrument spacers and standoffs. Laxcon Steels draws the bar to order.

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 hexagonal bright bar supply conditions

Size range: 15 mm - 52 mm (5/8" - 2")
Length: Up to 6 metres
Tolerances: h11, k12, k13, ASTM A484
Grit Polish: As per customer’s request
Heat Treatment: Solution annealing
Bars End Finish: Chamfered ends, 30°, 45°, 60°, and Plain Ends without Burrs or Sharp Edges
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 10278: Dimensions and tolerances of bright steel products: the h and k tolerance classes for drawn, turned, peeled and ground bars.
EN 10061: Hot rolled hexagon 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.
ISO 286-1 and 286-2: The ISO code system for tolerances on linear sizes: the IT grades and the fundamental deviations behind h7, h9, h11, k12, k13, j6, f7 and f8.
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.

Tolerance by size, ISO 286

Nominal across flats (mm)	h11	k12	k13
over 10 to 18	0 / -0.110	0 / +0.180	0 / +0.270
over 18 to 30	0 / -0.130	0 / +0.210	0 / +0.330
over 30 to 50	0 / -0.160	0 / +0.250	0 / +0.390
over 50 to 80	0 / -0.190	0 / +0.300	0 / +0.460

Deviations in millimetres from the nominal size, ISO 286-1 and ISO 286-2. An h class permits no plus material and the full grade below nominal; the k12 and k13 classes of EN 10278, used for peeled and turned bars, permit the full grade above nominal and none below.

Weight per metre

Across flats (mm)	kg per metre	Metres per tonne
15	1.54	649.6
15.88	1.73	579.6
16	1.75	570.9
18	2.22	451.1
19	2.47	404.9
19.05	2.48	402.7
20	2.74	365.4
21	3.02	331.4
22	3.31	302.0
22.22	3.38	296.0
24	3.94	253.7
25	4.28	233.8
25.4	4.41	226.5
26	4.63	216.2
27	4.99	200.5
28	5.36	186.4
28.58	5.59	178.9
30	6.16	162.4
31.75	6.90	145.0
32	7.01	142.7
34	7.91	126.4
34.92	8.34	119.9
36	8.87	112.8
38	9.88	101.2
38.1	9.93	100.7
40	10.95	91.3
45	13.86	72.2
50	17.11	58.5
50.8	17.66	56.6
52	18.50	54.1

Density 7.90 g/cm³, plain section (across flats squared x 0.006842).

Ordering AISI 304 hexagonal bright bar

An enquiry for this grade in this form states the grade and the standard it is ordered to, such as AISI 304 to EN 10088-3 or ASTM A276, the cold drawn condition, the size across flats with its tolerance class, h11 to EN 10278 or k12 and k13 for peeled and turned bar, the cut length, the quantity, the inspection document wanted under EN 10204, and any further test such as ultrasonic examination or positive material identification.