Austenitic Stainless Steel

The most common grades of stainless steel the austenitic grades account for the greates proportion of steel production (Type 304 accounts for more than 50% of total world production).

The addition of nickel gives the Austenitic grades their higher corrosion resistance compared to the maretenistic and ferritic grades.

Various others elements are added to produce further improved corrosion resistance. Type 316 - marine grade stainless steel contains up to 3% Molybdenum.

The addition of up to 3% Nitrogen can be added to certain specialist steels to increase their strength. The strength of such alloys makes them suitable for niche applications such as power generator retaining rings, high-strength bolts and superconducting magnet housings.

Chemical Composition of Austenitic Stainless Steel

AISI grade	C max.	Si max.	Mn max.	Cr	Ni	Mo	Ti	Nb	Al	V
301	0.15	1.00	2.00	16-18	6-8
302	0.15	1.00	2.00	17-19	8-10
304	0.08	1.00	2.00	17.5-20	8-10.5
310	0.25	1.50	2.00	24-26	19-22
316	0.08	1.00	2.00	16-18	10-14	2.0-3.0
321	0.08	1.00	2.00	17-19	9-12		5 x %C min.
347	0.08	1.00	2.00	17-19	9-13			10 x %C min.
E 1250	0.1	0.5	6.0	15.0	10.0					0.25
20/25-Nb	0.05	1.0	1.0	20.0	25.0			0.7
A 286	0.05	1.0	1.0	15.0	26.0	1.2	~1.9	~0.18	~0.25
254SMO	0.02	0.8	1.0	18.5-20.5	17.5-18.5	6-6.5	~1.9	~0.18	~0.25
AL-6XN	0.03	1.0	2.0	20-22	23.5-25.5	6-7

Type 301

Stainless Steel Type 301

Under Development

Type 302

Stainless Steel Type 302

Under Development

Type 304

Stainless Steel Type 304

Generally regarded as 18/8 stainless steel due to nominal Chrome (18%) and Nickel Content (8%), this grade is associated with typical applications where environment corrosion is not a key factor. This alloy has good welding characteristics and machining properties. The lower the carbon content the more resistant material is to carbide precipitation at higher temperature. Typical applications include internal architectural, heat exchanger and food processing.

Type 316

Stainless Steel Type 316 "Marine Grade"

Often referred as marine grade, 316 austenitic stainless steel materials with their inclusion of Molybdenum (Mo) offer excellent corrosion resistance. Superior to 304 in corrosion resistance this grade also offers a high resistance to pitting and crevice corrosion, in chloride environments. This alloy offers excellent welding characteristics and good forming properties. Low carbon grades "316L" and stabilized grades "316Ti" are very good for welding, whilst 316H and 316Ti with higher carbon content are good at higher strength elevated temperature application. Apart from marine, petrochemical, power generation and external architectural applications, 316 is regularly used in process control.

Type 321

Stainless Steel Type 321/321H

This alloy is a stabilized grade of in essence 304 with the addition of Titanium (Ti) at 5 x Carbon content minimum. It prevents carbide precipitation during welding and improves elevated temperature properties. Excellent resistance to oxidation and good creep strength. Corrosion resistance good. "H" grade is same alloy with a higher carbon range of 0.040% to 0.080%. Typical applications include refinery equipment, automotive exhaust headers, welded pressure vessels and generally applications with higher temperature service.

Type 347

Stainless Steel Type 347

347/347H stainless steel is similar to 321 albeit this stabilised grade by the addition of Columbium and Tantalum. This offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range 427-816 Degrees C. This grade is advantageous for high temperature service because of its good mechanical properties with higher creep and stress rupture. This alloy is often used in high heat applications in power generation and petrochemical environment.

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