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Duplex stainless steels. Analogues of Russian and foreign steels Testing at elevated temperature

1.4301 is the standard for austenitic stainless steel grades due to its good corrosion resistance, ease of shaping and fabrication, combined with its aesthetic appearance in polished, ground and ground conditions.

Standard	EN 10028-7 - Steel flat products for pressure purposes. Part 7: Stainless Steels EN 10088-1 - Stainless steels. Part 1: List of stainless steels EN 10088-2 - Stainless steels. Part 2: Specification for the delivery of general purpose stainless steel sheets and strips 10088-3 - Stainless steels. Part 3. Specification for the supply of semi-finished products, rods, wire rod, drawn wire, profiles and products with improved surface finish of stainless steels for general purposes; EN 10088-4 - Stainless steel - Part 4: Technical delivery conditions for plate and/or strip of stainless steels for building purposes EN 10088-5 - Stainless steels. Part 5. Technical delivery conditions for bars, wire rod, drawn wire, profiles and products with improved surface finishes of stainless steels for building EN 10151 - Stainless steel strips for springs - Technical delivery conditions EN 10216-5 - Seamless steel pipes for pressure purposes. Technical terms of delivery. Part 5. Stainless steel pipes EN 10217-7 - Welded steel pipes for pressure purposes. Technical terms of delivery. Part 7. Stainless steel pipes EN 10222-5 - Steel forgings for pressure vessels. Part 5: Martensitic, austenitic and austenitic-ferritic stainless steels EN 10250-4 - Steel blanks for general use. Part 4. Stainless steels EN 10263-5 - Steel bars, strips and wires for cold heading and cold extrusion. Part 5. General terms of delivery for stainless steel EN 10264-4 - Steel wire and wire products. Part 4: Stainless steel wire EN 10269 - Steels and nickel alloys for high and/or low temperature fasteners EN 10270-3 - Specification for steel wire for mechanical springs. Part 3. Stainless Steel Wire EN 10272 - Stainless steel rods for pressure applications EN 10296-2 - Welded steel round pipes for mechanical and general technical purposes. Technical terms of delivery. Part 2. Stainless steels EN 10297-2 - Seamless round steel tubes for engineering and general technical purposes. Technical terms of delivery. Part 2. Stainless steels EN 10312 - Stainless steel welded pipes for the supply of aqueous liquids, including potable water. Technical terms of delivery
rental	Pipe, rod, rod, wire rod, profile
Other names	International (UNS)	S30400
	Commercial	Acidur 4567

Since 1.4301 is not resistant to intergranular corrosion when welded, 1.4307 should be mentioned if welding of large sections is required and no solution annealing treatment after welding can be performed. Surface condition plays an important role in corrosion resistance. These steels, with polished surfaces, have a much higher corrosion resistance compared to rougher surfaces on the same material.

Chemical composition in % steel X5CrNi18-10

The specific value of S is determined depending on the required properties:
- for machining S 0.15 - 0.30
- for weldability S 0.008 - 0.030
- for polishing S< 0,015

Mechanical properties of X5CrNi18-10 material

EN 10028-7, EN 10088-2, EN 10088-4, EN 10312
Assortment	Thickness, mm, max	Yield strength, R 0,2 , MPa, min	Yield strength, R 1,0 , MPa, min	m , MPa	Orelative elongation, %, min (longitudinal and transverse specimens) with thickness
Assortment	Thickness, mm, max	Yield strength, R 0,2 , MPa, min	Yield strength, R 1,0 , MPa, min	m , MPa	< 3 мм	≥ 3mm
Cold rolled strip	8	230	260	540 - 750	45	45
hot rolled sheet	13,5	210	250	520 - 720	45	45
Hot-rolled strip	75	210	250	520 - 720	45	45

EN 10250-4, EN 10272 (thickness ≤400)
Thickness, mm	Yield strength, R 0,2 , MPa, min	Yield strength, R 1,0 , MPa, min	m , MPa	Relative elongation, %, (transverse specimens), min	Impact energy work KV 2 , J, min
					Longitudinal samples	Cross samples
≤250		225	500 - 700	35	100	60

Processing for solid solution:
- temperature 1000 - 1100 °C
- cooling: water or air

Heat treatment:
+A - softening annealing
+AT - solid solution treatment

Surface quality:
+C - cold deformation
+LC - smoothing rolling
+PE - after stripping

EN 10264-4
Diameter (d), mm	Tensile strength, MPa, min (NT)
d ≤ 0.20	2050
0,20 < d ≤ 0,30	2000
0,30 < d ≤ 0,40	1950
0,40 < d ≤ 0,50	1900
0,50 < d ≤ 0,65	1850
0,65 < d ≤ 0,80	1800
0,80 < d ≤ 1,00	1750
1,00 < d ≤ 1,25	1700
1,25 < d ≤ 1,50	1650
1,50 < d ≤ 1,75	1600
1,75 < d ≤ 2,00	1550
2,00 < d ≤ 2,50	1500
2,50 < d ≤ 3,00	1450

EN 10270-3
Diameter (d), mm	Tensile strength, MPa, max
Diameter (d), mm	NS	HS
d ≤ 0.20	2000	2150
0,20 < d ≤ 0,30	1975	2050
0,30 < d ≤ 0,40	1925	2050
0,40 < d ≤ 0,50	1900	1950
0,50 < d ≤ 0,65	1850	1950
0,65 < d ≤ 0,80	1800	1850
0,80 < d ≤ 1,00	1775	1850
1,00 < d ≤ 1,25	1725	1750
1,25 < d ≤ 1,50	1675	1750
1,50 < d ≤ 1,75	1625	1650
1,75 < d ≤ 2,00	1575	1650
2,00 < d ≤ 2,50	1525	1550
2,50 < d ≤ 3,00	1475	1550
3,00 < d ≤ 3,50	1425	1450
3,50 < d ≤ 4,25	1400	1450
4,25 < d ≤ 5,00	1350	1350
5,00 < d ≤ 6,00	1300	1350
6,00 < d ≤ 7,00	1250	1300
7,00 < d ≤ 8,50	1200	1300
8,50 < d ≤ 10,00	1175	1250

EN 10088-3(1C, 1E, 1D, 1X, 1G and 2D), EN 10088-5(1C, 1E, 1D, 1X, 1G and 2D)
Thickness, mm	Hardness HBW, max	Yield strength, R 0,2 , MPa, min	Yield strength, R 1,0 , MPa, min	Tensile strength R m , MPa
					Longitudinal samples	Cross samples
≤160	215	190	225	500 - 700	45	-
>160≤ 250 (EN 10088-3, EN 10088-5) >160 ≤400 (EN 10272)	215	190	225	500 - 700	-	35

Hot deformation: temperature 1200 - 900°C, air cooling
Solid solution treatment: temperature 1000 - 1100 °C, cooling in water, in air

EN 10088-3(2H, 2B, 2G and 2P), EN 10088-5(2H, 2B, 2G and 2P)
Thickness, mm (t)	Yield strength, R 0,2 , MPa, min	Tensile strength R m , MPa	Relative elongation, %, min		Impact work KV 2 , J, min
Thickness, mm (t)	Yield strength, R 0,2 , MPa, min	Tensile strength R m , MPa	Longitudinal samples	Cross samples	Longitudinal samples	Cross samples
≤ 10	400	600 - 950	25	-	-	-
10 < t ≤ 16	400	600 - 950	25	-	-	-
16 < t ≤ 40	190	600 - 850	30	-	100	-
40 < t ≤ 63	190	580 - 850	30	-	100	-
63 < t ≤ 160	190	500 - 700	45	-	100	-
160 < t ≤ 250	190	500 - 700	-	35	-	60

Tensile strength of wire diameter ≥ 0.05 mm under 2H conditions

EN 10088-3
Tensile strength, MPa
+C500	+C600	+C700	+C800	+C900	+C1000	+C1100	+C1200	+C1400	+C1600	+C1800
500-700	600-800	700-900	800-1000	900-1100	1000-1250	1100-1350	1200-1450	1400-1700	1600-1900	1800-2100

Mechanical properties at room temperature of annealed wire in the 2D state

EN 10088-3(2D)
Thickness, mm (t)	Tensile strength R m , MPa	Relative elongation, %, min
Thickness, mm (t)	Tensile strength R m , MPa	Relative elongation, %, min
0,05< t ≤0,10	1100	20
0,10< t ≤0,20	1050	20
0,20< t ≤0,50	1000	30
0,50< t ≤1,00	950	30
1,00< t ≤3,00	900	30
3,00< t ≤5,00	850	35
5,00< t ≤16,00	800	35

Mechanical properties for bars at room temperature of steels in the hardened (2H) state

Heat treatment before subsequent deformation
- Treatment for solid solution: 1020 - 1100 °C
- Hardening in water, in air or in a gas environment (cooling must be fast enough)
Hot forming before post-processing
- temperature 1100 - 850 °C
- cooling in air or in a gaseous medium

Tests at elevated temperature

Temperature, °C	EN 10269(+AT)		EN 10088-3, EN 10088-5, EN 10216-5, EN 10272
Temperature, °C	Yield strength, min, R p0.2 , MPa		Yield strength, min, R p0.2 , MPa	Yield strength, min, R p0.2 , MPa	Tensile strength, min, Rm, MPa (EN 10272)
50	177	480	180 (EN 10216-5)	218 (EN 10216-5)	-
100	155	450	155	190	450
150	140	420	140	170	420
200	127	400	127	155	400
250	118	390;	118	145	390
300	110	380	110	135	380
350	104	380	104	129	380
400	98	380	98	125	380
450	95	375	95	122	370
500	92	260	92	120	360
550	90	335	90	120	330
600	-	300	-	-	-

Temperature, °C	EN 10088-2, EN 10088-4, EN 10028-7, EN 10217-7, EN 10222-5, EN 10312
Temperature, °C	Yield strength, min, R p0.2 , MPa	Yield strength, min., R p1.0 , min, MPa
50	190 (EN 10028-7), 180 (EN 10217-7)	228 (EN 10028-7), 218 (EN 10217-7)
100	157	191
150	142	172
200	127	157
250	118	145
300	110	135
350	104	129
400	98	125
450	95	122
500	92	120
550	90	120

Physical properties

Steel density (weight) X5CrNi18-10- 7.9 g / cm 3

Technological properties

Weldability
According to ISO/TR 20172	Group 8.1

The closest equivalents (analogues) of steel X5CrNi18-10

Corrosion resistance

Due to the moderate carbon content of 1.4301, this grade of stainless steel is susceptible to sensitization. The formation of chromium carbides and the associated chromium regions that form around these precipitates makes this class of steel susceptible to intergranular corrosion. Although there is no danger of intergranular corrosion in the (solution annealed) condition, intergranular corrosion may occur after welding or high temperature processing. 1.4301 resists corrosion in most environments at low chloride and salt concentrations. 1.4301 is not recommended for applications where it comes into contact with sea water and is not recommended for use in swimming pools.

Welding

1.4301 can be welded with or without filler. If filler is required, Novonit 4316 (AISI 308L) is recommended. The maximum temperature range is 200°C. No heat treatment is required after welding.

Forging

1.4301 is usually heated between 1150°C and 1180°C to allow forging at temperatures between 1180°C and 950°C. Forging is followed by air cooling or water quenching when there is no danger of distortion.

Treatment

The following cutting parameters are suggested as a guide when machining the NIRO-CUT 4301 using carbide cutting tools.

Steel is an alloy of iron and carbon.

Depending on the percentage of carbon " FROM"In such an alloy, steels have different properties and characteristics. By adding various chemical elements to the alloy during smelting (called "alloying elements"), steels with a wide variety of properties can be obtained. Steels with similar characteristics were collected in groups.

In order for the steel to be called stainless, the chromium content in the composition of such steel must be more than 10.5% and the carbon content is low (no more than 1.2%). The presence of chromium gives steel corrosion resistance - hence the name "stainless". In addition to chromium as an "obligatory stainless component", stainless steel may also contain alloying elements: nickel (Ni), molybdenum (Mo), Titanium (Ti), Niobium (Nb), Sulfur (S), Phosphorus (P) and other elements, the combination of which determines the properties of the steel.

The main grades of stainless steels for fasteners

Historically, the development and smelting of new stainless steels and alloys are closely associated with advanced technological industries: aircraft and rocket science. The leading states in the world in these branches of engineering were the USSR and the USA, they were in a state of "cold war" for a long time, and each went its own way. Germany was and is the technological leader in Europe in the 20th century. Each of them developed his own classification of stainless steels: in the USA - the system AISI, in Germany - DIN, in the USSR - GOST.

For a very long time, there was no question of any cooperation between these three leaders - hence the large number of today's standards for stainless steels, and their very difficult, and sometimes absent, interchangeability.

The United States and Germany are somehow simpler: after all, between these countries for decades there has been mutual trade in technical means and technologies, which inevitably led to mutual adaptation, and in the field of stainless steel standards too. The most difficult countries are the countries of the former USSR, where standards developed in isolation from the rest of the world, and today, many grades of imported stainless steels simply do not have analogues - or vice versa: there are no imported analogues of Soviet stainless steels.

This whole situation is extremely slowing down and hindering the development of domestic engineering, which is already on its knees.

As a result, we have the following world standards for stainless steels:

DIN- Deutsche Industrie Norm
EN- Euronorm standard EN 10027
DIN EN- German edition of the European Standard
ASTM- American Society for Testing and Materials
AISI- American Iron and Steel Institute
AFNOR- Association Francaise de Normalization
GOST- State standard

There are no mass or serial manufacturers of stainless fasteners in Ukraine, so we all have to study and adapt to foreign classification and marking of stainless steels and fasteners.

In recent years, Russian standards for stainless fasteners have been approved, adopting the terminology and markings from European standards (for example, GOST R ISO 3506-2-2009). In Ukraine, most likely, no changes and innovations are expected in the near future...

And yet, the most used stainless steels for the production of fasteners have approximate analogues in various classification systems - the main ones are given in the following table of correspondences of stainless steel grades for fasteners:

Stainless steel standards				Content of alloying elements, %
*	DIN	AISI	GOST	C	Mn	Si	Cr	Ni	Mo	Ti
C1	1.4021	420	20X13	0,20	1,5	1,0	12-14
F1	1.4016	430	12X17	0,08	1,0	1,0	16-18
A1	1.4305	303	12X18H10E	0,12	6,5	1,0	16-19	5-10	0,7
A2	1.4301	304	12X18H10	0,07	2,0	0,75	18-19	8-10
	1.4948	304H	08X18H10	0,08	2,0	0,75	18-20	8-10,5
	1.4306	304L	03Х18Н11	0,03	2,0	1,0	18-20	10-12
A3	1.4541	321	08X18H10T	0,08	2,0	1,0	17-19	9-12		5xC-0.7
A4	1.4401	316	03Х17Н14М2	0,08	2,0	1,0	16-18	10-14	2-2,5
	1.4435	316S	03Х17Н14М3	0,08	2,0	1,0	16-18	12-14	2,5-3
	1.4404	316L	03Х17Н14М3	0,03	2,0	1,0	17-19	10-14	2-3
A5	1.4571	316ti	08X17H13M2T	0,08	2,0	0,75	16-18	11-12,5	2-3	5хС-0.8

In turn, depending on the composition and properties, stainless steels are divided into several subgroups, indicated in the first column:

* - designations of subgroups of stainless steels:

A1, A2, A3, A4, A5- Austenitic stainless steels - in general, non-magnetic or slightly magnetic steels with the main constituents of 15-20% chromium and 5-15% nickel, which increases corrosion resistance. They are well exposed to cold working, heat treatment and welding. Indicated by the initial letter " A". It is the austenitic group of stainless steels that is most widely used in industry and in the manufacture of fasteners.
C1- Martensitic stainless steels are significantly harder than austetitic steels and can be magnetic. They are hardened by quenching and tempering, like simple carbon steels, and are used mainly in the manufacture of cutlery, cutting tools and general engineering. More susceptible to corrosion. Indicated by the initial letter " FROM"
F1- Ferritic stainless steels are much softer than martensitic due to their low carbon content. They also have magnetic properties. Indicated by the initial letter " F"

Austenitic stainless steels of subgroups A2, A4 and others

Marking system for austenitic stainless steels with the letter " BUT"Developed in Germany for simplified marking of fasteners. Let's take a closer look at austenitic steels by subgroups:

Subgroup A1

steel subgroup A1 are characterized by a high sulfur content and, therefore, are most susceptible to corrosion. Become A1 have high hardness and wear resistance.

They are used in the manufacture of spring washers, pins, some types of cotter pins, as well as for parts of movable joints.

Subgroup A2

The most common subgroup of stainless steels in the manufacture of fasteners A2. These are non-toxic, non-magnetic, non-hardenable, corrosion-resistant steels. They are easy to weld and do not become brittle. Initially, the steels of this subgroup are non-magnetic, but can exhibit magnetic properties as a result of cold machining - forging, upsetting. They have good resistance to corrosion in the atmosphere and in pure water.

Fasteners and steel products A2 not recommended for use in acids and chlorinated environments (e.g. swimming pools and salt water).

Steel fasteners A2 keeps working capacity up to temperatures - 200˚C.

In the German classification DIN, A2

DIN 1.4301 ( American counterpart AISI 304, Soviet closest analogue 12X18H10),
DIN 1.4948 ( American counterpart AISI 304H, Soviet closest analogue 08X18H10),
DIN 1.4306 ( American counterpart AISI 304L, Soviet closest analogue 03Х18Н11).

Therefore, if you see a marking on a bolt, screw or nut A2, then it is most likely that this fastener is made from one of these three steels. It is usually difficult to determine more precisely due to the fact that the manufacturer indicates only the marking A2.

All three steels included in the subgroup A2 do not contain titanium ( Ti) - this is due to the fact that from steels A2, mainly produce products by stamping, and the addition of titanium to stainless steel significantly reduces the ductility of such steel, and, therefore, such steel with titanium is very difficult to stamp.

Noteworthy are the numbers 18 and 10 in the Soviet designation 12X18H10 steel analog DIN 1.4301. On imported stainless utensils, the designation 18/10 is often found - this is nothing more than an abbreviated designation of stainless steel with a percentage of chromium 18% and nickel 10% - i.e. DIN 1.4301.

Become A2 often used for the manufacture of utensils and elements of food equipment - therefore the popular name of such steels is closely related to the scope of steels A2- "food stainless steel". There is some semantic confusion here. The name "food stainless steel" is associated with the scope, and not with the properties of steel A2, and this is not quite the right name, since it is titanium itself that has antibacterial properties - and only stainless steel containing titanium in its composition can rightfully be called "food".

Subgroup stainless steel fasteners A2 may have some magnetic properties in strong magnetic fields. On their own became subgroups A2 are non-magnetic, some magnetism appears in bolts, screws, washers and nuts as a result of stresses arising from cold deformation - stamping.

The manufacturing plant, both utensils and fasteners, can use the above stainless steels additionally alloyed in very small quantities with some other elements, such as Molybdenum, to give their products special consumer properties. This can only be found out with the help of spectral analysis in the laboratory - the manufacturer himself can consider the composition of the steel a "trade secret" and indicates, for example, only A2.

Subgroup A3

steel subgroup A3 have similar properties to steels A2, but additionally alloyed with titanium, niobium or tantalum. This increases the corrosion resistance of steels at high temperatures and imparts spring properties.

Used in the manufacture of parts with high rigidity and spring properties (washers, rings, etc.)

Subgroup A4

The second most common subgroup of stainless steels for fasteners is the subgroup A4. Become A4 their properties are also similar to A2 steels, but additionally alloyed with the addition of 2-3% Molybdenum. Molybdenum gives steels A4 significantly higher corrosion resistance in aggressive environments and in acids.

Fasteners and rigging products made of steel A4 well resist the effects of chlorine-containing environments and salt water, and therefore are recommended for use in shipbuilding.

Steel fasteners A4 keeps working capacity up to temperatures - 60˚C.

In the German classification DIN, based on the table, such steel A4 can match one of three stainless steels:

DIN 1.4401 ( American counterpart AISI 316, Soviet closest analogue 03X17H14M2)
DIN 1.4404 ( American counterpart AISI 316L, Soviet closest analogue 03Х17Н14М3)
DIN 1.4435 ( American counterpart AISI 316S, Soviet closest analogue 03Х17Н14М3)

Since the subgroup A4 has increased corrosion resistance not only in the atmosphere or water, but also in aggressive environments - therefore the popular name of steel A4"acid-resistant" or also called "molybdenum" because of the content of Molybdenum in the composition of steel.

Stainless steel subgroups A4 practically do not have magnetic properties.

Resistance to external conditions of various environments on stainless fasteners is given in the article " "

Subgroup A5

Subgroup steel A5 has properties similar to those of steels A4 and with steels A3, since it is also additionally alloyed with titanium, niobium or tantalum, but with a different percentage of alloying additives. These features give the steel A5 increased resistance to high temperatures.

Steel A5 as well as A3, has spring properties and is used for the manufacture of various fasteners with high rigidity and spring properties. At the same time, the performance of steel fasteners A5 stored at high temperatures and in aggressive environments.

The applicability of stainless steels for the manufacture of fasteners

Here is a brief table of the most common types of fasteners and the corresponding types of stainless steels:

*Fastener name*	*Steel subgroup*	*DIN*	*AISI*
	A2, A4
	A2, A4	1.4301, 1.4306, 1.4948, 1.4401, 1.4404, 1.4435	304, 304H, 304L, 316, 316L, 316S
	A2, A4	1.4301, 1.4306, 1.4948, 1.4401, 1.4404, 1.4435	304, 304H, 304L, 316, 316L, 316S
,		1.4122, 1.4310	440A, 301
		1.4122, 1.4310	440A, 301
		1.4122, 1.4310	440A, 301
	A2, A4	1.4301, 1.4306, 1.4948, 1.4401, 1.4404, 1.4435	304, 304H, 304L, 316, 316L, 316S
	A2, A4	1.4301, 1.4306, 1.4948, 1.4401, 1.4404, 1.4435	304, 304H, 304L, 316, 316L, 316S
	A1, A5	1.4305, 1.4570, 1.4845	303, 316Ti, 310S
		1.4122, 1.4310	440A, 301
	A1, A2	1.4301, 1.4306, 1.4948	303, 304, 304H, 304L

Also, the above types of fasteners can be made by manufacturers from stainless steel grades other than those listed in the table with minor additional "secret" alloying additives to impart specific steel properties. For example, retaining rings can be made from such a "special" stainless steel of the subgroup A2, which is a trade secret of the manufacturer.

The most common stainless steels

Below is a more complete table of the most common types of stainless steels and their correspondence to various standard classifications.

Chemical composition according to EN	DIN	AISI	ASTM	AFNOR
Stainless chromium-nickel steels (Cr + Ni)
X 5 CrNi 18 10	1.4301	304	S30400	Z 6 CN 18 09
X 5 CrNi 18 12	1.4303	305		Z 8 CN 18 12
X 10 CrNi S 18 9	1.4305	303	S 30300	Z 10 CNF 18 09
X 2 CrNi 19 11	1.4306	304L	S30403	Z 3 CN 18 10
X 12 CrNi 17 7	1.4310	301	S 30100	Z 11 CN 18 08
X 2 CrNiN 18 10	1.4311	304LN	S30453	Z 3 CN 18 10 Az
X 1 CrNi 25 21	1.4335	310L		Z 1 CN 25 20
X 1 CrNiSi 18 15	1.4361		S 30600	Z 1 CNS 17 15
X6 CrNiTi 18 10	1.4541	321	S32100	Z 6 CNT 18 10
X6 CrNiNb 18 10	1.4550	347(H)	S34700	Z 6 CNNb 18 10
*Stainless chromium nickel molybdenum steels (Cr + Ni + Mo)*
X 5 CrNiMo 17 12 2	1.4401	316	S31600	Z 7 CND 17 11 02
X 2 CrNiMo 17 13 2	1.4404	316L	S31603	Z 3 CND 18 12 2
X 2 CrNiMoN 17 12 2	1.4406	316LN	S31653	Z 3 CND 17 11 Az
X 2 CrNiMoN 17 13 3	1.4429	316LN(Mo+)	(S31653)	Z 3 CND 17 1 2 Az
X 2 CrNiMo 18 14 3	1.4435	316L(Mo+)	S31609	Z 3 CND 18 14 03
X 5 CrNiMo 17 13 3	1.4436	316(Mo)		Z 6 CND 18 12 03
X 2 CrNiMo 18 16 4	1.4438	317L	S31703	Z 3 CND 19 15 04
X 2 CrNiMoN 17 13 5	1.4439	317LN	S31726	Z 3 CND 18 14 05 Az
X 5 CrNiMo 17 13	1.4449	(317)		Z 6 CND 17 12 04
X 1 CrNiMoN 25 25 2	1.4465		N08310/S31050	Z 2 CND 25 25 Az
X 1 CrNiMoN 25 22 2	1.4466		S31050	Z 2 CND 25 22 Az
X 4 NiCrMoCuNb 20 18 2	1.4505			Z 5 NCDUNb 20 18
X 5 NiCrMoCuTi 20 18	1.4506			Z 5 NCDUT 20 18
X 5 NiCrMoCuN 25 20 6	1.4529		S31254 (±)
X 1 NiCrMoCu 25 20 5	1.4539	904L	N 08904	Z 2 NCDU 25 20
X 1 NiCrMoCu 31 27 4	1,4563		N 08028	Z 1 NCDU 31 27 03
X 6 CrNiMoTi 17 12 2	1.4571	316ti	S31635	Z 6 CNDT 17 12
X 3 CrNiMoTi 25 25	1.4577			Z5 CNDT 25 24
X 6 CrNiMoNb 17 12 2	1.4580	316Cb/Nb	C31640	Z 6 CNDNb 17 12
X 10 CrNiMoNb 18 12	1.4582	318		Z 6 CNDNb 17 13
Duplex stainless steels (DUPLEX)
X 2 CrNiN 23 4	1.4362		S32304/S39230	Z 3CN 23 04 Az
X 2 CrNiMoN 25 7 4	1.4410		S31260/S39226	Z 3 CND 25 07 Az
X 3 CrNiMoN 27 5 2	1.4460	329	S32900	Z 5 CND 27 05 Az
X 2 CrNiMoN 22 5 3	1.4462	(329 LN)/F 51	S31803/S39209	Z 3 CND 22 05 Az
X 2 CrNiMoCuWN 25 7 4	1.4501	F55	S32760
X 2 CrNiMoCuN 25 6 3	1.4507		S32550/S32750	Z 3 CNDU 25 07 Az
X 2 CrNiMnMoNbN 25 18 5 4	1.4565		S24565
Stainless steels high temperature (600°C - 1200°C)
X 10 CrAl 7	1.4713			Z 8 CA 7
X 10 CrSiAl 13	1.4724			Z 13 C 13
X 10CrAI 18	1.4742	442	S44200	Z 12 CAS 18
X 18 CrN 28	1.4749	446	S44600	Z 18 C 25
X 10 CrAlSi 24	1.4762			Z 12 CAS 25
X 20 CrNiSi 25 4	1.4821	327		Z 20 CNS 25 04
X 15 CrNiSi 20 12	1.4828	302B/309	S 30215/30900	Z 17 CNS 20 12
X 6 CrNi 22 13	1.4833	309(S)	S30908	Z 15 CN 24 13
X 15 CrNiSi 25 20	1.4841	310/314	S 31000/31400	Z 15 CNS 25 20
X 12 CrNi 25 21	1.4845	310(S)	S31008	Z 8 CN 25 20
X 12 NiCrSi 35 16	1.4864	330	N 08330	Z 20 NCS 33 16
X 10 NiCrAlTi 32 20	1.4876		N 08800	Z 10 NC 32 21
X 12 CrNiTi 18 9	1.4878	321H	S32109	Z 6 CNT 18 12
X 8 CrNiSiN 21 11	1.4893		S30815
X 6 CrNiMo 17 13	1.4919	316H	S31609	Z 6 CND 17 12
X 6 CrNi 18 11	1.4948	304H	S30409	Z 6 CN 18 11
X 5 NiCrAlTi 31 20	1.4958		N 08810	Z 10 NC 32 21
X 8 NiCrAlTi 31 21	1.4959		N 08811
Tool stainless steels (Cr)
X 6 Cr 13	1.4000	410S	S41008	Z 8 C 12
X 6 CrAl 13	1.4002	405	S40500	Z 8 CA 12
X 12 CrS 13	1.4005	416	S41600	Z 13 CF 13
X 12 Cr 13	1.4006	410	S41000	Z 10 C 13
X 6 Cr 17	1.4016	430	S43000	Z 8 C 17
X 20 Cr 13	1.4021	420	S42000	Z 20 C 13
X 15 Cr 13	1.4024	420S	J91201	Z 15 C 13
X 30 Cr 13	1.4028	420	J91153	Z 33 C 13
X 46 Cr 13	1.4034	(420)		Z 44 C 14
X 19 CrNi 17 2	1.4057	431	S43100	Z 15 CN 16 02
X 14 CrMoS 17	1.4104	430F	S43020	Z 13 CF 17
X 90 CrMoV 18	1.4112	440B	S44003	Z 90 CDV 18
X 39 CrMo 17 1	1.4122	440A		Z 38 CD 16 01
X 105 Cr Mo 17	1.4125	440C	S 44004/S 44025	Z 100 CD 17
X 5 CrTi 17	1.4510	430ti	S 43036/S 43900	Z 4 CT 17
X 5 CrNiCuNb 16 4	1.4542	630	S17400	Z 7 CNU 17 04
X 5 CrNiCuNb 16 4	1.4548	630	S17400	Z 7 CNU 17 04
X 7 CrNiAl 17 7	1.4568	631	S17700	Z 9 CNA 1 7 07

Designations of chemical elements in the table:
Fe - Iron
C - Carbon
Mn - Manganese
Si - Silicon
Cr - Chrome
Ni - Nickel
Mo - Molybdenum
Ti - Titanium

The most detailed review of AISI304 stainless steel

Stainless steel AISI 304 (EN 1.4301)

European designation (1)
X5CrNi18-10
1.4301

American designation (2) AISI 304
Domestic analogues
08X18H10, 12X18H9

(1) According to NF EN 10088-2
(2) According to ASTM A 240

Brand differentiation 304

During the production of steel, the following special properties can be set, which predetermine its use or further processing:
- Improved weldability
— Deep drawing, Rotary drawing —
Stretch molding - Increased strength,
Work hardening - Heat resistance C, Ti (carbon, titanium) —
Mechanical restoration

Typically, steel manufacturers divide the brand into three main classes (grades) according to their ability to draw:
AISI 304 Main variety
AISI 304 DDQ Normal and deep drawing Deep drawing grade
AISI 304 DDS Extra deep drawing Extra deep drawing grade

Chemical composition (% by mass)

standard	brand	C	Si	Mn	P	S	Cr	Ni
EN 10088-2	1.4301	<0,070	<1,0	<2,0	<0,045	<0,015	17,00 — 19,50	8,00 — 10,50
ASTM A240	304	<0,080	<0,75	<2,0	<0,045	<0,030	18,00 — 20,00	8,00 — 10,50

Main characteristics

Key Features 304:
– good overall corrosion resistance
- good plasticity
- excellent weldability
- good polishability
– good drawability for DDQ and DDS grades

304L is an austenitic stainless steel with good cold formability, corrosion resistance, strength and good mechanical properties. It has a lower carbon content than 304, which improves its resistance to intergranular corrosion in welds and slow cooling zones.

Typical Application

- Household items
– Sinks
– Frames for steel structures in the construction industry
– Kitchen utensils and catering equipment
– Dairy equipment, brewing
- welded structures
— Vessels and land tankers for food, beverages and certain chemicals.

Applied standards and approvals

AMS 5513 ASTM
A 240 ASTM A
666

Physical properties

Density	d	—	4°C	7,93
Melting temperature		°C		1450
Specific heat	c	J/kg.K	20°C	500
thermal expansion	k	W/m.K	20C	15
Average coefficient of thermal expansion	a	10″.K"	0-100°C 0-200°C	17.5 18
Electrical resistivity	R	Omm2/m	20°C	0.80
Magnetic permeability	M	at 0.8 kA/m DC or V/H AC	20°C M M discharge air,	Feb 01
Elastic modulus	E	MPa x 10	20°C	200
Transverse compression ratio:

Corrosion resistance

304 steels have good resistance to general corrosive environments, but are not recommended where there is a risk of intergranular corrosion. They are well suited for operation in fresh water and urban and rural environments. In all cases, regular cleaning of external surfaces is necessary to maintain their original condition. 304 grades have good resistance to various acids:
— phosphoric acid in all concentrations at ambient temperature,
- nitric acid up to 65%, between 20 and 50°C?
- formic and lactic acid at room temperature,
— acetic acid between 20 and 50°C.

Acid environments

Atmospheric influences

Comparison of Grade 304 with other metals in various environments (Corrosion rate calculated at 10 years of exposure).

Stainless steel weldingAISI304

Weldability is very good, easy to weld.

There is no need for heat treatment after welding.

However, where there is a risk of ICC, annealing should be performed at 1050-1100°C.

18-9 L - low carbon grade or 18-10 T - stabilized grade is preferred in this case.

Welds must be mechanically or chemically descaled and then passivated.

heat treatment

Annealing
The annealing temperature range of 1050°C ± 25°C is followed by rapid cooling in air or water. The best corrosion resistance is obtained when annealed at 1070°C and cooled quickly. After annealing, etching and passivation are necessary.

Vacation
For 304L - 450-600 °C. within one hour with little risk of sensitization. For 304 - a lower tempering temperature of 400°C maximum should be used.

Forging interval
Initial temperature: 1150 - 1260°C.
Final temperature: 900 - 925°C.
Any hot working must be followed by annealing.
Note: Stainless steel requires twice the time for the same thickness of carbon steel to heat uniformly.

Etching
Mixture of Nitric acid and hydrofluoric/hydrofluoric acid (10% HNO3
+ 2% HF) at room temperature or 60°C. Sulfuric acid mixture
(10% H2SO4 + 0.5% HNO3) at 60°C. Descaling paste in the zone
Passivation
20-25% HNO3 solution at 20°C. Passivating pastes for the welding zone.

Universal stainless steel AISI 304 and AISI 304L.

The AISI304 grade is the most versatile and most widely used of all stainless steel grades. Its chemical composition, mechanical properties, weldability and corrosion/oxidation resistance provide the best choice in most cases at a relatively low cost. This steel also has excellent low temperature properties.

Application area
Corrosion resistant, austenitic, weldable, non-stabilized steel. It is suitable for the manufacture of chemical reactors, including pressure vessels. It is suitable for oxidizing media, for strong inorganic acids only at low concentrations and in the low temperature range. It is suitable for weak organic acids in case of medium temperatures and in cases of contact with air. It is used in the production of spare parts and equipment in the food, chemical and fermentation industries (at temperatures up to 300 C). It is possible to use AISI 304 steel for environments where hygienic purity of the product is required - the food industry and elements of cooling and freezing devices (except for brine).
The steel is characterized by very good polishing properties and particularly good ductility and deep drawability. It is suitable for wire water, steam, food acids. This steel is most often used in the dairy industry, brewing, cosmetics, but also in the chemical and pharmaceutical industries.

The development of the food industry has led to the fact that 304 and 316Ti materials have now been almost completely replaced by 304L and 316L materials.

Compliance with European steel standards

304 1.4301 X2CrNi18-10
304L 1.4306 X2CrNi19-11
304L 1.4307 X2CrNiTi18-10

316L 1.4404 X2CrNiMo17-12-2
316L 1.4435 X2CrNiMo18-14-3
316L 1.4571 X6CrNiMoTi17-12-2

Steel A2 (AISI 304 = 1.4301 = 08X18H10)– non-toxic, non-magnetic, non-hardenable, corrosion-resistant steel. It is easy to weld and does not become brittle. May exhibit magnetic properties as a result of machining (washers and some types of screws). This is the most common group of stainless steels. The closest analogues are 08X18H10 GOST 5632, AISI 304 and AISI 304L (with a reduced carbon content).

Stainless steel for the food industry

There are many grades of stainless steels used as structural materials for food processing equipment. Their choice depends on the corrosive properties of the manufactured product or chemicals in contact with this material. The most widely used steel grades are austenitic stainless steels (AISI 304, AISI 316 and AISI 316L according to the classification of the American International Standards Institute, AISI) with good mechanical and technological properties and having an attractive appearance.
AISI 304 (according to DIN no. 1.4301) is the cheapest steel widely used in the food and beverage industry due to its good corrosion resistance in various environments, as well as ease of formation and welding.
AISI 316 (according to DIN no. 1.4401) characterized by the addition of molybdenum (2-3 g/100 g), which increases the corrosion resistance.
AISI 316L (according to DIN no. 1.4404) is a low carbon steel (maximum carbon content 0.03 g/100 g) compared to AISI 316 which has a maximum carbon content of 0.08 g/100 g. for the manufacture of pipelines and containers.

All stainless steels in the presence of chlorine are susceptible to corrosion - pitting, cracking or fatigue, which is clearly localized and the extent of which depends on the influence of the chemical composition of the environment, pH value, temperature, methods of steel production, its tensile strength, oxygen concentration and quality of surface treatment.
Other materials have been developed for use in harsh environments, such as Incoloy 825 (a high-temperature nickel-chromium alloy), titanium steel and duplex steel, but they are much more expensive.

Duplex stainless steels are becoming more and more common. They are made by all major stainless steel manufacturers - and for a number of reasons:

High strength to reduce product weight
High corrosion resistance, especially to stress corrosion cracking

Every 2-3 years, conferences dedicated to duplex steels are held, at which dozens of in-depth technical articles are presented. There is an active promotion of this type of steel on the market. New grades of these steels are constantly appearing.

But despite all this interest, the share of duplex steels in the world market is, according to the most optimistic estimates, from 1 to 3%. The purpose of this article is to explain in simple terms the features of this type of steel. Both advantages and disadvantages will be described. duplex stainless steel products.

General information about duplex stainless steels

The idea of creating duplex stainless steels arose in the 1920s, and the first melt was made in 1930 in Avesta, Sweden. Nevertheless, a noticeable increase in the share of use of duplex steels occurs only in the last 30 years. This is mainly explained by the improvement of steel production technology, especially the processes for controlling the nitrogen content in steel.

Traditional austenitic steels such as AISI 304 (similar to DIN 1.4301 and 08X18H10) and ferritic steels such as AISI 430 (similar to DIN 1.4016 and 12X17) are fairly easy to manufacture and machine. As their names suggest, they are predominantly composed of a single phase: austenite or ferrite. Although these types have a wide range of applications, both of these types have their technical disadvantages:

Austenitic - low strength (conditional yield strength 0.2% in the state after austenization 200 MPa), low resistance to stress corrosion cracking

Ferritic ones have low strength (slightly higher than austenitic ones: the conditional yield strength of 0.2% is 250 MPa), poor weldability at large thicknesses, low-temperature brittleness

In addition, the high content of nickel in austenitic steels leads to their rise in price, which is undesirable for most end users.

The main idea of duplex steels is to select such a chemical composition, which will form approximately the same amount of ferrite and austenite. This phase composition provides the following advantages:

1) High strength - the range of the conditional yield strength of 0.2% for modern duplex steel grades is 400-450 MPa. This allows you to reduce the cross section of the elements, and hence their mass.

This advantage is especially important in the following areas:

Pressure vessels and tanks
Building structures such as bridges

2) Good weldability of large thicknesses - not as easy as austenitic, but much better than ferritic.

3) Good impact strength - much better than ferritic steels, especially at low temperatures: usually up to minus 50 degrees Celsius, in some cases up to minus 80 degrees Celsius.

4) Resistance to corrosion cracking (SCC) - traditional austenitic steels are especially prone to this type of corrosion. This advantage is especially important in the manufacture of structures such as:

Hot water tanks
Brewing tanks
Concentrating plants
Pool frames

How is the austenite/ferrite equilibrium achieved?

To understand how duplex steel is obtained, you can first compare the composition of two well-known steels: austenitic - AISI 304 (similar to DIN 1.4301 and 08X18H10) and ferritic - AISI 430 (similar to DIN 1.4016 and 12X17).

Structure	brand	EN designation
ferritic			16,0-18,0
Austenitic			17,5-19,5	8,0-10,5

The main elements of stainless steels can be divided into ferritizing and austenizing. Each of the elements contributes to the formation of a particular structure.

Ferritizing elements are Cr (chromium), Si (silicon), Mo (molybdenum), W (tungsten), Ti (titanium), Nb (niobium)

The austenizing elements are C (carbon), Ni (nickel), Mn (manganese), N (nitrogen), Cu (copper)

AISI 430 steel is dominated by ferritizing elements, so its structure is ferritic. AISI 304 steel has an austenitic structure, mainly due to the content of about 8% nickel. To obtain a duplex structure with a content of each phase of about 50%, a balance of austenizing and ferritizing elements is necessary. This is the reason why the nickel content of duplex steels is generally lower than that of austenitic steels.

The following is a typical composition of duplex stainless steel:

brand	EN/UNS number		Approximate content

LDX 2101	1.4162/ S32101	low alloyed
	1.4062/S32202	low alloyed
	1.4482/ S32001	low alloyed
	1.4362/ S32304	low alloyed
	1.4462/ S31803/ S32205	Standard
	1.4410/ S32750	Super
Zeron 100	1.4501/ S32760	Super
Ferrinox255/ Uranus 2507 Cu	1.4507/ S32520/ S32550	Super

Some of the newly developed grades use a combination of nitrogen and manganese to significantly reduce nickel content. This has a positive effect on price stability.

At present, the technology for the production of duplex steels is still developing. Therefore, each manufacturer promotes its own brand. By all accounts, there are too many duplex steel grades now. But apparently, we will observe such a situation until "winners" are revealed among them.

Corrosion resistance of duplex steels

Due to the variety of duplex steels, when determining corrosion resistance, they are usually listed together with austenitic and ferritic steel grades. A single measure of corrosion resistance does not yet exist. However, it is convenient to use the Pitting Corrosion Resistance Numerical Equivalent (PREN) to classify steel grades.

PREN = %Cr + 3.3 x %Mo + 16 x %N

Below is a table of the corrosion resistance of duplex steels compared to austenitic and ferritic grades.

brand	EN/UNS number		Indicative PREN
	1.4016/ S43000	ferritic
	1.4301/ S30400	Austenitic
	1.4509/ S43932	ferritic
	1.4482/ S32001	Duplex
	1.4401/ S31600	Austenitic
	1.4521/ S44400	ferritic
316L 2.5Mo		Austenitic
2101 LDX	1.4162/ S32101	Duplex
	1.4362/ S32304	Duplex
	1.4062/S32202	Duplex
	1.4539/ N08904	Austenitic
	1.4462/ S31803/ S32205	Duplex
Zeron 100	1.4501/ S32760	Duplex
Ferrinox 255/ Uranus 2507 Cu	1.4507/ S32520/ S32550	Duplex
	1.4410/ S32750	Duplex
	1.4547/ S31254	Austenitic

It should be noted that this table can only serve as a guide when choosing a material. It is always necessary to consider how suitable a certain steel is for service in a particular corrosive environment.

Corrosion cracking (SCC - Stress Corrosion Cracking)

SCC is one of the types of corrosion that occurs in the presence of a certain set of external factors:

Tensile stress
corrosive environment
Sufficiently high temperature This is usually 50 degrees Celsius, but in some cases, such as in swimming pools, it can occur at temperatures around 25 degrees Celsius.

Unfortunately, conventional austenitic steels such as AISI 304 (similar to DIN 1.4301 and 08X18H10) and AISI 316 (similar to 10X17H13M2) are the most susceptible to SCC. The following materials have much higher CR resistance:

Ferritic stainless steels
Duplex stainless steels
Austenitic stainless steels with high nickel content

The SCC resistance allows the use of duplex steels in many high temperature processes, in particular:

In water heaters
In brewing tanks
In desalination plants

Stainless steel pool frames are known for their tendency to SCC. The use in their manufacture of conventional austenitic stainless steels, such as AISI 304 (similar to 08X18H10) and AISI 316 (similar to 10X17H13M2) is prohibited. Austenitic steels with a high nickel content, such as grades with 6% Mo, are best suited for this purpose. However, in some cases, duplex steels such as AISI 2205 (DIN 1.4462) and super duplex steels can be considered as alternatives.

Factors hindering the spread of duplex steels

An attractive combination of high strength, wide range of corrosion resistance, medium weldability should, in theory, carry great potential to increase the market share of duplex stainless steels. However, it is necessary to understand what are the shortcomings of duplex stainless steels and why they are likely to remain in the status of "niche players".

Such an advantage as high strength instantly turns into flaw, as soon as it comes to manufacturability of material forming and machining. High strength also means lower plastic deformation than austenitic steels. Therefore, duplex steels are practically unsuitable for the production of products that require high ductility. And even when the ability to plastic deformation is at an acceptable level, it still requires more effort to give the necessary shape to the material, such as when bending pipes. There is one exception to the rule regarding poor machinability: grade LDX 2101 (EN 1.4162) from Outokumpu.

The smelting process for duplex stainless steels is much more complex than for austenitic and ferritic steels. If the production technology, in particular heat treatment, is violated, in addition to austenite and ferrite, a number of undesirable phases can form in duplex steels. The two most significant phases are depicted in the diagram below.

Click on the image to enlarge.

Both phases lead to brittleness, i.e. loss of impact strength.

The formation of the sigma phase (more than 1000º C) most often occurs when the cooling rate is insufficient during the manufacturing or welding process. The more alloying elements in the steel, the higher the probability of the formation of a sigma phase. Therefore, super duplex steels are most susceptible to this problem.

The 475-degree brittleness results from the formation of a phase called α' (alpha prime). Although the most dangerous temperature is 475 degrees Celsius, it can also form at lower temperatures, up to 300º C. This imposes restrictions on the maximum operating temperature of duplex steels. This limitation further narrows the range of possible applications.

On the other hand, there is a limitation on the minimum operating temperature of duplex steels, for which it is higher than that of austenitic. Unlike austenitic steels, duplex steels undergo a brittle-ductile transition during impact tests. The standard test temperature for steels used in offshore oil and gas structures is minus 46º C. Duplex steels are generally not used at temperatures below minus 80 degrees Celsius.

A brief overview of the properties of duplex steels

Twice the design strength of austenitic and ferritic stainless steels
A wide range of corrosion resistance values, allowing you to choose a brand for a specific task
Good impact strength down to minus 80º C, limiting the use in cryogenic environments.
Exceptional resistance to stress corrosion cracking
Good weldability of large cross sections
Greater difficulty in machining and stamping than austenitic steels
The maximum operating temperature is limited to 300 degrees Celsius

Material taken from the website of the British Stainless Steel Association www.bssa.org.uk

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