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Specifying stainless steel for spring applications

Introduction

European standards now cover both strip and wire products for springs. BS EN 10151:2002 applies to strip and replaces BS5770 part 4:1981, which is now withdrawn. BS EN ISO 6931-1:2020 applies to wire and replaces BS EN 10270-3:2001 which had previously replaced BS2056:1991, full details of the historical evolution of the standards can be found at the BSI website. Both standards use the European steel grade number system, most of which are also shown in BS EN 10088-1

BSEN 10151 stainless steel strip for springs

BS EN 10151 was published in 2002 and replaced BS5770 part 4 (1981), which is now withdrawn. It contains 10 grades, one ferritic, three martensitics, one precipitation hardening and five austenitic. With the exception of austenitic grade 1.4369 (X11CrNiMnN19-8-6), the grade compositions are covered by BS EN 10088-2. The composition of grade 1.4369 has been designed to keep the steel non-magnetic in all conditions. The BS EN 10151 has a more comprehensive scope than BS5770:4.

BS EN 10151 grade 1.4310 is the alternative to BS5770 grade 301S21, 1.4301 the alternative to 302S25 and 1.4401 the alternative to 316S16 in the austenitic types. Grades 1.4021 and 1.4028 are the BSEN 10151 alternatives to martensitic BS5770, 420S29 and 420S45 grades.

The other main difference between the standards is the way in which the ‘spring temper’ is specified. BS EN 10151 uses tensile strength ranges, rather than the Vickers hardness ‘conditions’ of BS5770:4. (TR230, TR280, TR330, TR380 etc depending on grade)

BSEN 10151 grades and delivery conditions

The compositions of all the grades are shown below.
Values are maxima, unless there is a range stated.

Steel name Number C Si Mn P S N Cr Mo Ni Others
X6Cr17 1.4016 0.08 1.00 1.00 0.040 0.015 16.0/18.0
X20Cr13 1.4021 0.16/0.25 1.00 1.50 0.040 0.015 12.0/14.0
X30Cr13 1.4028 0.26/0.35 1.00 1.50 0.040 0.015 12.0/14.0
X39Cr13 1.4031 0.36/0.42 1.00 1.00 0.040 0.015 12.5/14.5
X7CrNiAl17-7 1.4568 0.09 0.70 1.00 0.040 0.015 16.0/18.0 6.5/7.8 Al:0.70/1.50
X10CrNi18-8 1.4310 0.05/0.15 2.00 2.00 0.045 0.015 0.11 16.0/19.0 0.80 6.0/9.5
X5CrNi18-10 1.4301 0.07 1.00 2.00 0.045 0.015 0.11 17.5/19.5 8.0/10.5
X5CrNiMo17-12-2 1.4401 0.07 1.00 2.00 0.045 0.015 0.11 16.5/18.5 2.0/2.50 10.0/13.0
X11CrNiMnN19-8-6 1.4369 0.07/0.15 0.50/1.00 5.0/7.5 0.030 0.015 0.20/0.30 17.5/19.5 6.5/8.5
X12CrMnNiN17-7-5 1.4372 0.15 1.00 5.5/7.5 0.045 0.015 0.05/0.25 16.0/18.0 3.5/5.5

The specified tensile ranges and the ‘available’ tensile strength levels, by grade, are tabulated below.

Steel name Number +C700 +C850 +C1000 +C1150 +C1300 +C1500 +C1700 +C1900 Hardness
X6Cr17 1.4016 X X NA NA NA NA NA NA 200/300
X20Cr13 1.4021 X X NA NA NA NA NA NA
X30Cr13 1.4028 X X NA NA NA NA NA NA
X39Cr13 1.4031 X X NA NA NA NA NA NA
X7CrNiAl17-7 1.4568 NA NA X X X X X NA
X10CrNi18-8 1.4310 NA X X X X X X X 250/600
X5CrNi18-10 1.4301 X X X X X NA NA NA 220/450
X5CrNiMo17-12-2 1.4401 X X X X X NA NA NA 220/400
X11CrNiMnN19-8-6 1.4369 NA X X X X X NA NA 300/475
X12CrMnNiN17-7-5 1.4372 NA X X X X X NA NA 250/500

Available tensile strength levels in MPa (N/mm2) are:-

+C700 = 700/850: +C850 = 850/1000: +C1000 = 1000/1150: +C1150 = 1150/1300; +C1300 = 1300/1500: +C1500 = 1500/1700: +C1700 = 1700/1900: +C1900 = 1900/2200

NOTES
Martensitic grades 1.4021, 1.4028 and 1.4031 should also be available in the annealed condition.

Precipitation hardening grade 1.4568 should also be available in the solution annealed condition.

Total hardness Vickers ranges apply to ferritic and austenitic types only. Steels can be supplied to any HV aim value within the range.

The table below shows approximate equivalents of the TR designations in BS 5770

BS 5770 Designation Approximate Equivalent UTS Range (MPa) Nearest Equivalent Condition in EN 10151
TR 500 > 1550 +C1500
TR 380 > 1230 +C1300
TR 330 1050/1230 +C1000/+C1150
TR 280 910/1050 +C850/+C1000
TR 230 750/910 +C700/+C850

BS EN ISO 6931-1:2020 Stainless steels for springs: Part 1 : Wire

BS EN ISO 6931-1: 2020 has replaced BS EN 10270-3 which was published in 2001 which in turn had replaced BS2056 (1991), both of which are now withdrawn. It contains 8 grades, six austenitic, one duplex and one precipitation hardening. (The grade compositions are also covered by BS EN 10088-3)

The BS EN ISO 6931-1:2020 has more grades than BS EN 10270-3 :2001, but unlike the original standard BS 2056:1991, it still does not include the hardenable martensitic 420S45. There still is no austenitic with the enhanced nickel range of the 305S11, (11.0/13.0% Ni), which was for applications where low magnetic permeability in the cold drawn condition was required. BS EN ISO 6931-1:2020 grade numbers 4310…. and 4325… are the alternatives to BS2056 302S26 and 4401… the alternative to 316S33 and 316S42. Grade number 4568… in BS EN ISO 6931-1:2020 is a 17-7 PH precipitation hardening stainless steel.  The original standards should be consulted for grade comparisons.

BS EN ISO 6931-1:2020 grades and delivery conditions

The compositions of all the grades are shown below.
Values are maxima, unless there is a range stated.

Name Number C Si Mn P S Cr Mo Ni Others
Austenitic Steels
X10CrNi18-8 4310-301-00-I 0.05/0.15 2.00 2.00 0.045 0.015 16.0/19.0 0.80 6.0/9.50 N:0.10
X9CrNi18-9 4325-302-00-E 0.030/0.15 1.00 2.00 0.045 0.030 17.0/19.0 8.0/10.0 N:0.10
X5CrNiN19-9 4315-304-51-I 0.08 1.00 2.50 0.045 0.030 18.0/20.0 7.0/10.5 N:0.10/0.30, Nb:0.15
X5CrNi18-10 4301-304-00-I 0.07 1.00 2.00 0.045 0.015 17.5/19.5 8.0/10.5 N:0.10
X5CrNiMo17-12-2 4401-316-00-I 0.07 1.00 2.00 0.045 0.015 16.5/18.5 2.00/3.0 10.0/13.0 N:0.10
X1NiCrMoCu25-20-5 4539-089-04-I 0.020 0.75 2.00 0.035 0.015 19.0/22.0 4.0-5.0 23.5/26.0 N:0.15, Cu: 1.20/2.00
Austenitic-ferritic (duplex) steel
X2CrNiMoN22-5-3 4462-318-03-I 0.030 1.00 2.00 0.035 0.015 21.0/23.0 2.50/3.50 4.5/6.5 N:0.10/0.22
Precipitation hardening steel steel
X7CrNiAl17-7 4568-177-00-I 0.09 0.70 1.00 0.040 0.015 16.0/18.0 7.0/8.5 Al:0.70/1.50

The specified minimum tensile strength levels, by grade, in the drawn or heat treated (4568… only) conditions are tabulated below.

Steel number 4310-301-00-I 4310-301-00-I 4325-302-00-E, 4315-304-51-I 4301-304-00-I 4301-304-00-I 4401-316-00-I 4539-089-04-I 4462-318-03-I 4462-318-03-I 4568-177-00-I
Nominal diameter Drawn Normal Drawn High Drawn Drawn Normal Drawn High Drawn Drawn Drawn Normal Drawn High Heat Treated
Below 0.20 2200 2350 2150 2000 2150 1725 1600 2150 2370 1975
0.20-0.30 2150 2300 2050 1975 2050 1700 1550 2100 2370 1950
0.30-0.40 2100 2250 2050 1925 2050 1675 1550 2000 2370 1925
0.40-0.50 2050 2200 1950 1900 1950 1650 1500 2000 2370 1900
0.50-0.65 2000 2150 1900 1850 1950 1625 1450 1900 2370 1850
0.65-0.80 1950 2100 1850 1800 1850 1600 1450 1900 2230 1825
0.80-1.00 1900 2050 1850 1775 1850 1575 1400 1800 2140 1800
1.00-1.25 1850 2000 1750 1725 1750 1550 1350 1800 2090 1750
1.25-1.50 1800 1950 1700 1675 1750 1500 1350 1700 2090 1700
1.50-1.75 1750 1900 1650 1625 1650 1450 1300 1700 2000 1650
1.75-2.00 1700 1850 1650 1575 1650 1400 1300 1700 2000 1600
2.00-2.50 1650 1750 1550 1525 1550 1350 1300 1550 1900 1550
2.50-3.00 1600 1700 1450 1475 1550 1300 1300 1550 1860 1500
3.00-3.50 1550 1650 1450 1425 1450 1250 1300 1550 1850 1450
3.50-4.25 1500 1600 1450 1400 1450 1225 1250 1450 1750 1400
4.25-5.00 1450 1550 1350 1350 1350 1200 1250 1450 1700 1350
5.00-6.00 1400 1500 1350 1300 1150 1300 1250 1350 1300
6.00-7.00 1350 1450 1270 1250 1300 1125 1200 1350 1250
7.00-8.50 1300 1400 1130 1200 1300 1075 1150 1250
8.50-10.0 1250 1350 980 1175 1250 1050 1250

Note for each diameter range, the properties quoted apply to the minimum diameter, but not to the maximum diameter.

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