AISI 304 Square Bars

AISI 304 square bright bar is a cold drawn austenitic bar with four true sides and a bright surface, used for machined parts and fittings.

12.7 to 55 mm Austenitic stainless steel Made to order

SQUARE BRIGHT BARS

AISI 304 square bright bar

AISI 304 square bright bar is a cold drawn stainless square section in the general purpose austenitic grade, the chromium and nickel steel long known as 18/8. Each drawn size, from 12.7 to 55 mm across the side, is made from the hot rolled black square beside it and pulled through a die that brings all four faces to size and leaves a bright, smooth surface. The grade carries no deliberate molybdenum, so it suits fresh water, food and mild chemicals rather than salt. AISI 316 is the step up, its molybdenum slowing the pitting that chloride ions start in seawater and brine. AISI 304L holds less carbon, which helps a heavily welded assembly. AISI 303 machines faster but corrodes more readily.

The black square is solution annealed before it is drawn, so the drawn bar starts from a soft, carbide free structure and then picks up strength in the die. Annealed 304 is non-magnetic and takes no hardening from heat treatment; ASTM A276 puts its minima at 515 MPa tensile and 205 MPa yield, and the drawing pass lifts the bar above both. The steel work hardens under the tool, so milling and turning ask for sharp edges, a firm feed and lower speeds than carbon steel. It welds without preheat. Square bar in this grade becomes machined blocks and spacers, balustrade and architectural fittings, frames and brackets for food and dairy plant, and square headed fasteners.

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 square bright bar supply conditions

Size range: 12.7 mm - 55 mm (1/2" - 2")
Length: Up to 6 metres
Tolerance: h11, k12, k13, ASTM A484
Grit Polish: As per customer’s request
Heat treatment: Solution annealing
Bars End Finish: Deburred Ends, 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 10059: Hot rolled square 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 side (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

Side (mm)	kg per metre	Metres per tonne
12.7	1.27	784.8
15	1.78	562.6
15.88	1.99	502.0
19	2.85	350.6
19.05	2.87	348.8
20	3.16	316.5
22	3.82	261.5
22.22	3.90	256.4
25	4.94	202.5
25.4	5.10	196.2
26	5.34	187.3
27	5.76	173.6
28	6.19	161.5
28.58	6.45	155.0
30	7.11	140.6
31.75	7.96	125.6
32	8.09	123.6
34	9.13	109.5
35	9.68	103.3
36	10.24	97.7
38	11.41	87.7
38.1	11.47	87.2
40	12.64	79.1
41	13.28	75.3
44	15.29	65.4
45	16.00	62.5
47	17.45	57.3
48	18.20	54.9
50	19.75	50.6
50.8	20.39	49.1
55	23.90	41.8

Density 7.90 g/cm³, plain section (side squared x 0.007900).

Ordering AISI 304 square bright bar

An enquiry for this grade in this form states the grade and its governing standard, AISI 304 to EN 10088-3 or ASTM A276, the condition as drawn, peeled or ground, the side size with its tolerance class, h11 to EN 10278 or k12 and k13 where the bar is peeled or turned, the cut length, the quantity, the certificate type to EN 10204, and any test called for, such as PMI. Laxcon Steels draws the bar to order.