What is Stainless Steel?

In metallurgy, stainless steel, also known as inox steel or inox, is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel (it stainsless, but it is not stain-proof). It is also called corrosion-resistant steel or CRES when the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment to which the material will be subjected in its lifetime. Common uses of stainless steel are cutlery and watch cases and bands.

Stainless steel differs from carbon steel by the amount of chromium present. Carbon steel rusts when exposed to air and moisture. This iron oxide film (the rust) is active and accelerates corrosion by forming more iron oxide. Stainless steel have sufficient amounts of chromium present so that a passive film of chromium oxide forms which prevents further surface corrosion and blocks corrosion from spreading into the metal’s internal structure.

Many types of stainless steel have been developed to resist different corrosion environments and working conditions ensuring that factories are safe, structures last longer and our food is hygienic. Stainless steel is even used for in systems to clean up the exhaust gases from cars and power stations.

Stainless steel is also recyclable: when scrapped, it can be re-melted to make something new.

Effect of Chromium:

Stainless steel are chromium containing steel alloys. The minimum chromium content of the standardised stainless steels is 10.5%. Chromium makes the steel ‘stainless’ this means improved corrosion resistance, as can be seen in the chart. The better corrosion resistance is due to a chromium oxide film that is formed on the steel surface. This extremely thin layer, under the right conditions, is also self-repairing.Besides chromium, typical alloying elements are molybdenum, nickel and nitrogen. Nickel is mostly alloyed to improve the formability and ductility of stainless steel. Alloying these elements brings out different crystal structures to enable different properties in machining, forming, welding etc.

The four major types of stainless steel tube are:

Austenitic Stainless Steel is the most widely used type of stainless steel. It has a nickel content of at least of 7%, which makes the steel structure fully austenitic and gives it ductility, a large scale of service temperature, non-magnetic properties and good weldability. The range of applications of austenitic stainless steel includes housewares, containers, industrial piping and vessels, architectural facades and constructional structures.

Ferritic Stainless Steel pipe has properties similar to mild steel but with the better corrosion resistance. The most common of these steels are 12% and 17% chromium containing steels, with 12% used mostly in structural applications and 17% in housewares, boilers, washing machines and indoor architecture.

Type 430	The basic ferritic grade, with a little less corrosion resistance than Type 304. This type combines high resistance to such corrosives as nitric acid, sulfur gases, and many organic and food acids.
Type 405	Has lower chromium and added aluminum to prevent hardening when cooled from high temperatures. Typical applications include heat exchangers.
Type 409	Contains the lowest chromium content of all stainless steels and is also the least expensive. Originally designed for muffler stock and also used for exterior parts in non-critical corrosive environments.
Type 434	Has molybdenum added for improved corrosion resistance. Typical applications include automotive trim and fasteners.
Type 436	Type 436 has columbium added for corrosion and heat resistance. Typical applications include deep-drawn parts.
Type 442	Has increased chromium to improve scaling resistance. Typical applications include furnace and heater parts.
Type 446	Contains even more chromium added to further improve corrosion and scaling resistance at high temperatures. Especially good for oxidation resistance in sulfuric atmospheres.

Austenitic-Ferritic Duplex Stainless Steel has a ferritic and austenitic lattice structure – hence common name: duplex stainless steel. This steel has some nickel content for a partially austenitic lattice structure. The duplex structure delivers both strength and ductility. Duplex steels are mostly used in petrochemical, paper, pulp and shipbuilding industries.

China GB	ISO Unified Digital Code	ASTM / ASME	UNS code	EN Code	Company Commercial Grade
022Cr23Ni4MoCuN	S23043	S32304	S32304	1.4362	SAF2304 (Sandvik)
022Cr22Ni5Mo3N	S22253	S31803	S31803	1.4462	–
022Cr23Ni5Mo3N	S22053	S32205	S32205	1.4462	SAF2205 (Sandvik)
022Cr25Ni7Mo4N	S25073	S32750	S32750	1.4410	SAF2507(Sandvik)
022Cr25Ni7Mo3WCuN	S22583	S31260	S31260	–	–
03Cr25Ni6Mo3Cu2N	S25554	S32550	S32550	1.4507	UR52+
022Cr25Ni7Mo4WCuN	S27603	S32760	S32760	1.4501	Zeron100
00Cr27Ni7Mo5N	–	S32707	S32707	–	SAF2707(Sandvik)

Martensitic Stainless Steel contains mostly 11 to 13% chromium and is both strong and hard with moderate corrosion resistance. This steel is mostly used in turbine blades and in knives.

Type 410	Basic martensitic grade, containing the lowest alloy content of the three basic stainless steels (304, 430, and 410). Low cost, general purpose, heat treatable stainless steel. Used widely where corrosion is not severe (air, water, some chemicals, and food acids. Typical applications include highly stressed parts needing the combination of strength and corrosion resistance such as fasteners.
Type 410S	Contains lower carbon than Type 410, offers improved weldability but lower hardenability. Type 410S is a general purpose corrosion and heat resisting chromium steel recommended for corrosion resisting applications.
Type 414	Has nickel added (2%) for improved corrosion resistance. Typical applications include springs and cutlery.
Type 416	Contains added phosphorus and sulfur for improved machinability. Typical applications include screw machine parts.
Type 420	Contains increased carbon to improve mechanical properties. Typical applications include surgical instruments.
Type 431	Contains increased chromium for greater corrosion resistance and good mechanical properties. Typical applications include high strength parts such as valves and pumps.
Type 440	Further increases chromium and carbon to improve toughness and corrosion resistance. Typical applications include instruments.

Precipitation-Hardening –   These alloys generally contain Cr and less than 8% Ni, with other elements in small amounts. As the name implies, they are hardenable by heat treatment.

Duplex –   This is a stainless steel alloy group, or family, with two distinct microstructure phases — ferrite and austenite. The Duplex alloys have greater resistance to chloride stress corrosion cracking and higher strength than the other austenitic or ferritic grades.

Cast –   The cast stainless steels, in general, are similar to the equivalent wrought alloys. Most of the cast alloys are direct derivatives of one of the wrought grades, as C-8 is the cast equivalent of wrought type 304. The C preceding a designation means that the alloy is primarily used for resistance to liquid corrosion. An H designation indicates high temperature applications.

Austenitic Stainless Steel

Corrosion Resistance Stainless Steel

ASME	AISI UNS	EN	JIS	Cmax	Cr	Ni	Mo	Cu	Others
TP 304	S30400	1.4301	SUS 304	0.080	18.0	8.0
TP 304 L	S30403	1.4307	SUS 304L	0.035	18.0	8.0
TP 304H	S30403	1.4948	SUS 304H	0.04-0.1	18.0	8.0
TP 321	S32100	1.4541	SUS 321	0.080	17.0	9.0			5(C+N)<Ti< 0.7
TP 321H	S32100	1.4878	SUS 321	0.04-0.1	17.0	9.0			4(C+N)<Ti< 0.7
TP 347	S3470	1.4550	SUS 347	0.080	17.0	9.0			10×C<Nb<1
TP 347H	S34709		SUS 347	0.04-0.1	17.0	9.0			8×C<Nb<1.10
TP 316	S31600	1.4401	SUS 316	0.060	16.0	10.0	2.0
TP 316L	S31603	1.4404	SUS 316L	0.030	16.0	10.0	2.0
TP 316H	S31609		SUS 316H	0.04-0.1	16.0	10.0	2.0
TP 316 Ti	S31635	1.4571	SUS 316Ti	0.030	16.0	10.0	2.0		N0.015(C+N)<Ti< 0.7
TP 317	S31700	1.4438	SUS 317L	0.080	18.0	11.0	3.0
TP 317L	31703	1.4438	SUS 317L	0.030	18.0	11.0	3.0
TP 309S	S30908	1.4833	SUS 309S	0.80	22.0	12.0
TP 310	S31000	1.4841	SUS 310	0.080	24.0	19.0
TP 310S	S31008	1.4845	SUS 310S	0.10	24.0	19.0
TP 310H	S31009	1.4845	SUS 310H	0.080	24.0	19.0
TP 904L	N08904	1.4539	SUS 904L	0.020	19.0>	23.0	4.0	1.0-2.0

High Temperature Stainless Steel/Heat Resistant Stainless Steel

TP 304H	S30403	1.4948	SUS 304H	0.04-0.1	18.0	8.0
TP 321H	S32100	1.4878	SUS 321	0.04-0.1	17.0	9.0	4(C+N)<Ti< 0.7
TP 347H	S34709		SUS 347	0.04-0.1	17.0	9.0	8×C<Nb<1.10
TP 309S	S30908	1.4833	SUS 310S	0.080	22.0	12.0
TP 310S	S31008	1.4845	SUS 310S	0.080	24.0	19.0
TP 310H	S31009	1.4845	SUS 310H	0.080	24.0	19.0

*All figures in weight percentage. In case of order, the limits of the order specification will apply.

Duplex Stainless Steel Austenitic Ferritic

Designation	UNS	EN	JIS	Cmax	Cr	Ni	Mo	Cu	Others
2101	S32101	1.4162	DP2	0.040	21.0	1.35	0.10	0.10	N 0.20
2205	S32205	1.4462	DP2	0.030	22.0	4.50	3.0		N 0.14
S31803	S31803	1.4462	DP2	0.030	21.0	4.50	2.5		N 0.08
2304	S32304	1.4362	DP2	0.030	21.5	3.0	<0.05-0.6	0.60	N 0.2
2507	S32750	1.4410	DP2	0.030	24.0	6.0>	3.0	0.50	N 0.32
	S32760	1.4501	DP2	0.030	24.0	6.0	3.0	0.50	N 0.20

*All figures in weight percentage. In case of order, the limits of the order specification will apply.

Name	ASTM	UNS	EN	DIN	SS	BS	C	Cr	Ni	Mo	Other
301	S30100	0.1	1.4310	1.4310	2331	301S21	0.04	17	7	–	–
302	S30200	0.07	1.4319	1.4319	2332	302S31	0.06	17	8	-–	–
303	S30300	0.06	1.4305	1.4305	2346	303S31	0.09	17.5	8.1	–	S
304	S30400	0.04	1.4301	1.4301	2333	304S31	0.06	18.2	8.1	–	–
304L	S30403	0.02	1.4306	1.4306	2352	304S11	0.06	18.2	8.2	–	–
304LN	S30453	0.02	1.4311	1.4311	2371	304S61	0.14	18.2	8.5	–	–
304N	S30451	0.04	1.6907	1.6907	–	304S71	0.14	18.5	8.5	–	–
305	S30500	0.02	1.4303	1.4303	–	305S19	0.02	18	11.5	–	–
308L	S30883	0.02	1.4316	1.4316	–	308S92	0.05	20	11	-–	–

316	S31600	0.04	1.4401	1.4401	2347	316S31	0.04	16.8	10.7	2	–
316	S31600	0.04	1.4436	1.4436	2343	316S33	0.06	17	11	2.8	–
316L	S31603	0.02	1.4404	1.4404	2348	316S11	0.06	16.2	10.2	2	–
316L	S31603	0.02	1.4432	1.4432	2353	316S13	0.06	16.2	10.2	2.8	–
316LN	S31653	0.02	1.4406	1.4406	–	316S61	0.14	16.2	10.2	2	–
316Ti	S31635	0.04	1.4571	1.4571	2350	320S31	0.01	17	11	2	Ti
317L	S31703	0.02	1.4438	1.4438	2367	317S12	0.08	18.3	11.5	3	–
317LM	S31725	0.02	1.4439	1.4439	–	–	0.08	19.3	13.7	4.3	–
317LMN	S31726	0.02	1.4439	1.4439	–	–	0.14	19.3	13.7	4.3	–

321	S32100	0.04	1.4541	1.4541	2337	321S31	0.01	17.3	9.2	–	Ti
347	S34700	0.04	1.455	–	2338	347S31	0.04	17.3	9.1	–	Cb

20	N08020	N08020	2.4660	–	–	–	0.01	0.06	20	33	2
904L	N08904	0.01	1.4539	1.4539	2562	904S13	0.06	20	25	4.5	Cu
254 SMo	S31254	S31254	1.4547	–	2378	–	0.01	0.2	20	18	6.1
654 SMo	S32654	S32654	1.4652	–	–	–	0.01	0.5	24	22	7.3

LDX 2101	S32101	S32101	1.4162	–	–	–	0.03	0.22	21.5	1.5	0.3
2304	2304	S32304	1.4362	1.4362	2327	–	0.02	0.1	23	4.8	0.3
2205	S32205/S31803	0.02	1.4462	1.4462	2377	318S13	0.17	22	5.5	3	–
2507	2507	S32750	1.441	–	2328	–	0.02	0.27	25	7	4
329	S32900	0.02	1.446	1.446	2324	2209,	0.06	25	5	1.5	–

405	S40500	0.06	1.4002	1.4002	–	–	–	11.5	–	–	Al
409	S40900		1.4512	1.4512			–	10.5	–	–	–
410	S41000	0.12	1.4006	1.4006	2302	410S21	–	11.5	–	–	–
410S	S41008	0.06	1.4	1.4	2301	403S17	–	12	–	–	–
416	S41600	0.12	1.4005	1.4005	2380	416S21	–	12	–	–	S
430	S43000	0.04	1.4016	1.4016	2320	430S17	–	16	–	–	–
434	S43400	0.06	1.4113				–	17	–	1	–
439	S43035	0.07	1.451				–	17.0	–	–	Ti

630	S17400	0.04	1.4542	1.4542	–	–	–	15.3	4.8	–	Cu,
631	S17700	0.05	1.4568	1.4568	2388	–	–	16.3	7	–	Al
304H	S30409	0.05	1.4948	1.4948	2333	304S51	0.06	18.2	8.1	–	–
321H	S32109	0.05	1.4878	1.4878	2337	321S51	0.01	17.3	9.2	–	Ti
309S	S30908	0.06	1.4833	1.4833	–	309S16	0.08	22.2	12.2	–	–
310S	S31008	0.05	1.4845	1.4845	2361	310S16	0.06	25.2	19.2	–	–

153 MA	S30415	0.05	–	2372	–	253	0.15	18.5	9.5	–	1.4818
253 MA	S30815	0.09	–	2368	–	253	0.17	21	11	–	1.4835
353 MA	S35315	0.05	–	–	–	353	0.16	25	35	–	1.4854

Chemical Composition

Grade	C (Max)	Mn (Max)	P (Max)	S (Max)	Si (Max)	Cr	Ni	Mo	Azoto (Max)	Cu/Outro
301	0.15	2.00	0.045	0.030	1.00	16.00 – 18.00	6.00 – 8.00	–	0.10	–
304	0.08	2.00	0.045	0.030	0.75	18.00 – 20.00	8.00- 10.50	–	0.10	–
304L	0.030	2.00	0.045	0.030	0.75	18.00 – 20.00	8.00- 12.00	–	0.10	–
310S	0.08	2.00	0.045	0.030	1.50	24.00- 26.00	19.00 – 22.00	–	–	–
316	0.08	2.00	0.045	0.030	0.75	16.00 – 18.00	10.00 – 14.00	2.00 – 3.00	0.10	–
316L	0.030	2.00	0.045	0.030	0.75	16.00 – 18.00	10.00 – 14.00	2.00 – 3.00	0.10	–
317	0.08	2.00	0.045	0.030	0.75	18.00 – 20.00	11.00 – 14.00	3.00 – 4.00	0.10	–
317L	0.030	2.00	0.045	0.030	0.75	18.00 – 20.00	11.00 – 15.00	3.00 – 4.00	0.10	–
321	0.08	2.00	0.045	0.030	0.75	17.00 – 19.00	9.00 – 12.00	–	0.10	Ti5 ( C + N ) Min or 0.70 max
347	0.08	2.00	0.045	0.030	0.75	17.00 – 19.00	9.00 – 13.00	–	–	Cb= 10x ( C Min ) or 1.00 Max
409	0.08	1.00	0.040	0.010	1.00	10.50 – 11.75	0.50	–	–	Ti= 6x (C+ N ) Min or 0.70 Max
409M	0.03	0.81.2	0.030	0.030	0.40.75	11.00- 12.00	1.5 max.	–	–	Ti= 6x (C) Min or 0.70 Max
410S	0.08	1.00	0.040	0.030	1.00	11.50- 13.50	0.60	–	–	–
410	0.15	1.00	0.040	0.030	1.00	11.50- 13.50	0.75	–	–	–
420	0.35	0.50	0.035	0.015	0.50	12.00 – 13.00	0.20.3	–	–	–
430	0.12	1.00	0.040	0.030	1.00	16.00 – 18.00	0.75	–	–	–
JSL AUS	0.08	7.08.0	0.070	0.030	0.75	15.50 – 16.50	4.25 – 4.75	–	–	0.9 – 1.10
JS- 203	0.08	9.2510.25	0.070	0.030	0.75	14.25 – 15.25	2.25 – 2.75	–	–	1.60- 2.0
301M	0.10	4.55.5	0.060	0.030	0.75	14.50 – 15.50	6.0 – 7.0	–	–	1.70- 1.90

Details Chemical Composition(GB,JIS,ASTM/ASME/AISI,DIN,EN)
Details Chemical Composition(GB,JIS,ASTM/ASME/AISI,DIN)

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What is Stainless Steel?

Effect of Chromium:

Austenitic Stainless Steel

High Temperature Stainless Steel/Heat Resistant Stainless Steel

Duplex Stainless Steel Austenitic Ferritic

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