AISI 316 Hex Bars

AISI 316 hexagonal bright bar is a cold drawn stainless hexagon in the molybdenum grade, machined into nuts and fittings for chloride service.

15 to 52 mm Austenitic stainless steel Made to order

HEXAGONAL BRIGHT BARS

AISI 316 hexagonal bright bar

AISI 316 hexagonal bright bar is a cold drawn stainless steel hexagon, 15 to 52 mm across flats, drawn from annealed and pickled hot rolled bar to a bright surface and a close size. The grade is austenitic and carries 2 to 3 percent molybdenum beside its chromium and nickel. Molybdenum slows pitting, the local attack that chloride ions start on the passive film, so the grade is specified for hexagons that work in seawater, brine, chlorinated water and many process liquors. AISI 304 in the same hexagon holds no molybdenum and is the usual choice for fresh water, food and mild chemicals. Where a machined part is welded into an assembly and not annealed afterwards, the lower carbon AISI 316L is taken instead.

The bar is drawn from solution annealed stock, so the grade cannot be hardened by heat treatment and gains strength only from the drawing pass. ASTM A276 sets 515 MPa tensile strength and 205 MPa yield strength as the annealed minima, and cold drawing raises both. The straight, hard drawn surface feeds well through bar-fed lathes, although 316 work hardens under the tool and asks for sharp edges, a firm feed and lower speeds than carbon steel. It welds without preheat, but carbon held up to 0.08 percent can form chromium carbides at the grain boundaries between about 450 and 850 C, which weakens corrosion resistance near a weld. Hexagons in this grade are machined into nuts and bolt heads, hydraulic and instrument fittings, valve stems and dosing pump parts.

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 16.0 to 18.0, nickel 10.0 to 14.0, molybdenum 2.0 to 3.0 and nitrogen 0.1 maximum.

SPECIFICATION

AISI 316 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 316 (316, SS 316, SUS 316, 1.4401)
Family: Austenitic stainless steel
Supply: Made to order in this grade; every published size of the form

Composition of AISI 316

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	16.0	18.0
Nickel	Ni	10.0	14.0
Molybdenum	Mo	2.0	3.0
Nitrogen	N		0.1

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

Equivalents of AISI 316

Standard	Designation
UNS	S31600
EN number	1.4401 (X5CrNiMo17-12-2)
JIS	SUS 316

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 316 runs from 22.6 at the specified minimum chromium, molybdenum and nitrogen to 29.5 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 316 hexagonal bright bar

An enquiry for this grade in this form states the grade and the governing standard, AISI 316 to ASTM A276 or 1.4401 to EN 10088-3, the condition as cold drawn, the size across flats with its tolerance class to EN 10278, h11 as drawn or k12 for peeled bar, the cut length, the quantity, the certificate type to EN 10204, and any test called for, such as ultrasonic testing or PMI. Laxcon Steels draws the bar to order.