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  4. ISO 3506-2 Specification

ISO 3506-2 Hex Nuts, High Nuts

ISO 3506-2 Scope

ISO 3506-2 specification concludes the mechanical and physical properties of nuts, with coarse pitch thread and fine pitch thread, made of corrosion-resistant stainless steels, when tested at the ambient temperature range of 10 °C to 35 °C. iso 3506-2 specifies property classes in relation to austenitic, martensitic, ferritic and duplex (austenitic-ferritic) steel grades for nuts. ISO 3506-2 Specification is applicable to nuts with coarse pitch thread M5 to M39, and fine pitch thread M8×1 to M39×3 with diameter/pitch combinations in accordance with ISO 261 and ISO 262.

Designation of ISO 3506-2

Stainless Steel Grades
A1 to A5 & A8 for Austenitic
C1, C3 & C4 for Martensitic
F1 for Ferritic
D2, D4, D6 & D8 for duplex (austenitic-ferritic)
added by a digit which specifies the range of chemical compositions within this stainless steel group

Property Classes
45 for 450 Mpa Tensile Min
50 for 500 Mpa Tensile Min
60 for 600 Mpa Tensile Min
70 for 700 Mpa Tensile Min
80 for 800 Mpa Tensile Min
100 for 100 Mpa Tensile Min
110 for 110 Mpa Tensile Min

Related Specifications of ISO 3506-2 Bolting

A193 A320 A1082 EN 10269 F2281 3506-1 ISO 3506-3 ISO 3506-5 DIN 267

Common Designations for cold heading

Type Of Steel/Alloy Grade Steel Number Steel Designation UNS Trade Name
Resulfurized austenitic A1 1.4305 X8CrNiS18-9 S30300 303
A1 1.4570 X6CrNiCuS18-9-2 - 303Cu
General purpose austenitic A2L 1.4307 X2CrNi18-9 S30403 304L
A2L 1.4306 X2CrNi19-11 S30403 304L
A2L 1.4311 X2CrNiN18-9 S30453 304LN
A2 1.4301 X5CrNi18-10 S30400 304
A2 1.4567 X3CrNiCu18-9-4 S30430 304Cu
A2 1.4560 X3CrNiCu19-9-2 - 304Cu
A2 1.4303 X4CrNi18-12 S30500 305
A3 1.455 X6CrNiNb18-10 S34700 347
A3 1.4541 X6CrNiTi18-10 S32100 321
- 1.4615 X3CrMnNiCu15-8-5-3 - 201Cu
- 1.4310 X10CrNi18-8 S30100 301
Molybdenum containing austenitic A4 1.4401 X5CrNiMo17-12-2 S31600 316
A4L 1.4404 X2CrNiMo17-12-2 S31603 316L
A4L 1.4406 X2CrNiMoN17-11-2 S31653 316LN
A4L 1.4432 X2CrNiMo17-12-3 S31603 316L
A4L 1.4435 X2CrNiMo18-14-3 S31603 316L
A4 1.4436 X3CrNiMo17-13-3 S31600 316
A4 1.4578 X3CrNiCuMo17-11-3-2 - -
A5 1.4571 X6CrNiMoTi17-12-2 S31635 316Ti
High molybdenum super-austenitic A8 1.4478 X2NiCrMoN25-21-7 N08367 AL-6XN
A8 1.4529 X1NiCrMoCuN25-20-7 N08926 926
A8 1.4547 X1CrNiMoCuN20-18-7 S31254 F44
Highly alloyed austenitic for special purposes S 1.4986 X7CrNiMoBNb16-16 - -
- 1.4539 X1NiCrMoCu25-20-5 N08904 904L
- 1.4841 X15CrNiSi25-21 S31400 314
- 1.4828 X15CrNiSi20-12 - 309
- 1.4845 X8CrNi25-21 S31008 310S
High manganese super-austenitic - 1.4020 X13CrMnNiN18-13-2 S24100 XM28
- 1.4378 X6CrMnNiN18-13-3 S24000 XM29
General purpose martensitic C1 1.4006 X12Cr13 S41000 410
C1 1.4000 X6Cr13 S41008 410S
C1, CH0 1.4021 X20Cr13 S42000 420
C1, CH1 1.4028 X30Cr13 S42000 420
C1 1.4034 X46Cr13 S42000 420
- 1.4003 X2CrNi12 S41003 410L
High Chromium Martensitic - 1.4542 X5CrNiCuNb16-4 S17400 17-4PH
- 1.4418 X4CrNiMo16-5-1 - SS2387
- 1.4122 X39CrMo17-1 - -
Resulfurised martensitic C4 1.4005 X12CrS13 S41600 416
C4 1.4029 X29CrS13 S42020 420F
Ferritic F1 1.4016 X6Cr17 S43000 430
F1 1.4511 X3CrNb17 - 430Nb
F1 1.4113 X6CrMo17-1 S43400 434
F1 1.4526 X6CrMoNb17-1 S43600 436
F1 1.4509 X2CrTiNb18 S43940 441
F1 1.4521 X2CrMoTi18-2 S44400 444
Resulfurised ferritic - 1.4004 X7CrS17 S43020 430F
- 1.4104 X14CrMoS17 S43020 430F
Duplex D2 1.4482 X2CrMnNiMoN21-5-3 S32001 2001
D2 1.4362 X2CrNiN23-4 S32304 2304
D4 1.4162 X2CrMnNiN21-5-1 S32101 2101
D4 1.4062 X2CrNiN22-2 S32202 2202
D6 1.4462 X2CrNiMoN22-5-3 S31803, S32205 31803, 2205
D6 1.4481 X2CrNiMoN25-7-3 S31260 SUS329J4L
D8 1.4410 X2CrNiMoN25-7-4 S32750 2507
D8 1.4501 X2CrNiMoCuWN25-7-4 S32760 Zeron 100
D8 1.4507 X2CrNiMoCuN25-6-3 S32520 Ferralium

ISO 3506-2 Property class combination of nuts to bolts, screws and studs

Property class of bolts, screws and studs Minimum property class of the mating nuts
Regular and high nuts (style 1 and style 2) Thin nuts (style 0)
45 45 22
50 50 25
60 60 30
70 70 35
80 80 40
100 100 50
110 110 55

ISO 3506-2 Chemical composition

Stainless steel grade Chemical composition a (cast analysis, mass fraction in %) b Other elements and notes
C Si Mn P S Cr Mo Ni Cu N
Austenitic A1 0,12 1,00 6,5 20 0,15 to 0,35 16,0 to 19,0 0,70 5,0 to 10,0 1,75 to 2,25 - c,d,e
A2 0,10 1,00 2,00 50 30 15,0 to 20,0 - f 8,0 to 19,0 4,0 - g,h
A3 0,08 1,00 2,00 45 30 17,0 to 19,0 - f 9,0 to 12,0 1,00 - 5C ≤ Ti ≤ 0,80 and/or 10C ≤ Nb ≤ 1,00
A4 0,08 1,00 2,00 45 30 16,0 to 18,5 2,00 to 3,00 10,0 to 15,0 4,0 - h,i
A5 0,08 1,00 2,00 45 30 16,0 to 18,5 2,00 to 3,00 10,5 to 14,0 1,00 - 5C ≤ Ti ≤ 0,80 and/or 10C ≤ Nb ≤ 1,00 i
A8 30 1,00 2,00 40 30 19,0 to 22,0 6,0 to 7,0 17,5 to 26,0 1,50 - -
Martensitic C1 0,09 to 0,15 1,00 1,00 50 30 11,5 to 14,0 - 1,00 - - i
C3 0,17 to 0,25 1,00 1,00 40 30 16,0 to 18,0 - 1,50 to 2,50 - - -
C4 0,08 to 0,15 1,00 1,50 60 0,15 to 0,35 12,0 to 14,0 0,60 1,00 - - c,i
Ferritic F1 0,08 1,00 1,00 40 30 15,0 to 18,0 - f 1,00 - - j
Duplex D2 40 1,00 6,0 40 30 19,0 to 24,0 0,10 to 1,00 1,50 to 5,5 3,00 0,05 to 0,20 Cr+3,3Mo + 16N ≤ 24,0 k
D4 40 1,00 6,0 40 30 21,0 to 25,0 0,10 to 2,00 1,00 to 5,5 3,00 0,05 to 0,30 24,0 < Cr+3,3Mo + 16N k
D6 30 1,00 2,00 40 15 21,0 to 23,0 2,50 to 3,5 4,5 to 6,5 - 0,08 to 0,35 -
D8 30 1,00 2,00 35 15 24,0 to 26,0 3,00 to 4,5 6,0 to 8,0 2,50 0,20 to 0,35 W ≤ 1,00
  • a According to material standards, values are maximum unless otherwise indicated and the number of digits shown is in accordance with usual rules; see e.g. EN 10088 (all parts).
  • b In case of dispute, product analysis applies.
  • c Selenium can be used to replace sulphur; however, restrictions may apply to its use.
  • d If the nickel content is below 8,0 %, the minimum manganese content shall be 5,0 %.
  • e There is no minimum limit to the copper content provided that the nickel content is greater than 8,0 %.
  • f Molybdenum may be present at the discretion of the manufacturer. However, if for some applications limiting of the molybdenum content is essential, this shall be stated at the time of ordering by the purchaser.
  • g If the chromium content is below 17,0 %, the minimum nickel content should be 12,0 %.
  • h For austenitic stainless steels having a maximum carbon content of 0,030 %, nitrogen may be present but shall not exceed 0,22 %.
  • i At the discretion of the manufacturer the carbon content may be higher as necessary in order to obtain the specified mechanical properties for larger diameters, but shall not exceed 0,12 % for austenitic steels.
  • j Titanium and/or niobium may be included to improve corrosion resistance.
  • k This formula is used solely for the purpose of classifying duplex steels in accordance with this document (it is not intended to be used as a selection criterion for corrosion resistance)

ISO 3506-2 Mechanical properties

Mechanical properties (Austenitic and Duplex Steel)

Stainless steel grade Regular nuts and high nuts (style 1 and style 2) Thin nuts (style 0)
Property class designation and symbol Stress under proof load a Sp MPa Property class designation and symbol Stress under proof load b Sp MPa
Austenitic A1 A2 A3 50 500 25 250
70 700 35 350
80 800 40 400
A4 A5 50 500 25 250
70 700 35 350
80 800 40 400
100 1000 50 500
A8 70 700 35 350
80 800 40 400
100 1000 50 500
Duplex D2 D4 D6 D8 70 700 35 350
80 800 40 400
100 1000 50 500
  • a Proof load values for regular and high nuts (full loadability) are specified for coarse pitch thread and fine pitch thread.
  • b Proof load values for thin nuts (reduced loadability) are specified for coarse pitch thread and fine pitch thread.

Mechanical properties (Martensitic and Ferritic Steel)

Stainless steel grade Regular nuts and high nuts (style 1 and style 2) Thin nuts (style 0) All nuts
Property class designation and symbol Stress under proof load a Sp Property class designation and symbol Stress under proof load b Sp Hardness min. to max.
MPa MPa HV HRC HBW
Martensitic C1 50 500 25 250 155 to 220 - 147 to 209
70 700 35 350 220 to 330 20 to 34 209 to 314
110 c 1100 055 c 550 350 to 440 36 to 45 -
C3 80 800 40 400 240 to 340 21 to 35 228 to 323
C4 50 500 25 250 155 to 220 - 147 to 209
70 700 35 350 220 to 330 20 to 34 209 to 314
Ferritic F1d 45 450 22 225 135 to 220 - 128 to 209
60 600 30 300 180 to 285 - 171 to 271
  • a Proof load values for regular and high nuts (full loadability) are specified for coarse pitch thread and fine pitch thread.
  • b Proof load values for thin nuts (reduced loadability) are specified for coarse pitch thread and fine pitch thread.
  • c Hardened and tempered at a minimum tempering temperature of 275 °C.
  • d Only for nominal thread diameters D ≤ 24 mm.

Proof load values for regular and high nuts with coarse pitch thread (full loadability)

Thread D×P Nominal stress area As,nom Proof load, Fpf a N
Austenitic and duplex steels Martensitic steels Ferritic steels
50b 70 80 100 50 70 80 110 45 60
M5 14,2 7100 9930 11350 14190 7100 9930 11350 15610 6390 8510
M6 20,1 10070 14090 16100 20130 10070 14090 16100 22140 9060 12080
M7 28,9 14430 20210 23090 28860 14430 20210 23090 31750 12990 17320
M8 36,6 18310 25630 29290 36610 18310 25630 29290 40270 16480 21970
M10 58,0 29000 40600 46400 57990 29000 40600 46400 63790 26100 34800
M12 84,3 42140 58990 67420 84270 42140 58990 67420 92700 37920 50560
M14 115 57720 80810 92360 115500 57720 80810 92360 127000 51950 69270
M16 157 78340 109700 125400 156700 78340 109700 125400 172400 70510 94010
M18 192 96240 134800 154000 192500 96240 134800 154000 211800 86620 115500
M20 245 122400 171400 195900 244800 122400 171400 195900 269300 110200 146900
M22 303 151700 212400 242800 303400 151700 212400 242800 333800 136600 182100
M24 353 176300 246800 282100 352600 176300 246800 282100 387800 158700 211600
M27 459 229800 321600 367600 459500 229800 321600 367600 505400 - -
M30 561 280300 392500 448500 560600 280300 392500 448500 616700 - -
M33 694 346800 485500 554900 693600 346800 485500 554900 763000 - -
M36 817 408400 571800 653400 816800 408400 571800 653400 898400 - -
M39 976 487900 683100 780700 975800 487900 683100 780700 1073400 - -
  • a Proof load values have been calculated from the exact figures of As,nom as specified in ISO 3506-1 and rounded to the next upper 10 N up to 100 000 N,and to the next 100 N above.
  • b Property class 50 refers to the austenitic grades A1 to A5 only

Proof load values for regular and high nuts with fine pitch thread (full loadability)

Thread D×P Nominal stress area As,nom Minimum ultimate tensile load, Fmf a N
Austenitic and duplex steels Martensitic steels Ferritic steels
50b 70 80 100 50 70 80 110 45 60
M8×1 39,2 19590 27420 31340 39170 19590 27420 31340 43090 17630 23510
M10×1,25 61,2 30600 42840 48960 61200 30600 42840 48960 67320 27540 36720
M10×1 64,5 32250 45150 51600 64500 32250 45150 51600 70950 29030 38700
M12×1,5 88,1 44070 61690 70510 88130 44070 61690 70510 96940 39660 52880
M12×1,25 92,1 46040 64460 73660 92080 46040 64460 73660 101300 41440 55250
M14×1,5 125 62280 87190 99640 124600 62280 87190 99640 137100 56050 74730
M16×1,5 167 83630 117100 133800 167300 83630 117100 133800 184000 75270 100400
M18×1,5 216 108200 151400 173000 216300 108200 151400 173000 237900 97310 129800
M20×2 258 129000 180600 206400 258000 129000 180600 206400 283800 116100 154800
M20×1,5 272 135800 190100 217300 271600 135800 190100 217300 298700 122200 163000
M22×1,5 333 166600 233200 266500 333100 166600 233200 266500 366400 149900 199900
M24×2 384 192300 269100 307600 384500 192300 269100 307600 422900 173000 230700
M27×2 496 247900 347100 396600 495800 247900 347100 396600 545400 - -
M30×2 621 310700 434900 497000 621300 310700 434900 497000 683400 - -
M33×2 761 380400 532600 608700 760800 380400 532600 608700 836900 - -
M36×3 865 432500 605500 692000 865000 432500 605500 692000 951500 - -
M39×3 1030 514200 719900 822800 1028400 514200 719900 822800 1131300 - -
  • a Proof load values have been calculated from the exact figures of As,nom as specified in ISO 3506-1 and rounded to the next upper 10 N up to 100 000 N and to the next 100 N above.
  • b Property class 50 refers to the austenitic grades A1 to A5 only

Proof load values for thin nuts with coarse pitch thread (reduced loadability)

Thread D×P Nominal stress area As,nom Proof load, Fpf a N
Austenitic and duplex steels Martensitic steels Ferritic steels
025 b 35 40 50 25 35 40 55 22 30
M5 14,2 3550 4970 5680 7100 3550 4970 5680 7810 3200 4260
M6 20,1 5040 7050 8050 10070 5040 7050 8050 11070 4530 6040
M7 28,9 7220 10110 11550 14430 7220 10110 11550 15880 6500 8660
M8 36,6 9160 12820 14650 18310 9160 12820 14650 20140 8240 10990
M10 58,0 14500 20300 23200 29000 14500 20300 23200 31900 13050 17400
M12 84,3 21070 29500 33710 42140 21070 29500 33710 46350 18960 25280
M14 115 28860 40410 46180 57720 28860 40410 46180 63500 25980 34640
M16 157 39170 54840 62670 78340 39170 54840 62670 86170 35260 47010
M18 192 48120 67370 76990 96240 48120 67370 76990 105900 43310 57750
M20 245 61200 85680 97920 122400 61200 85680 97920 134700 55080 73440
M22 303 75850 106200 121400 151700 75850 106200 121400 166900 68270 91020
M24 353 88130 123400 141100 176300 88130 123400 141100 193900 79320 105800
M27 459 114900 160800 183800 229800 114900 160800 183800 252700 - -
M30 561 140200 196300 224300 280300 140200 196300 224300 308400 - -
M33 694 173400 242800 277500 346800 173400 242800 277500 381500 - -
M36 817 204200 285900 326700 408400 204200 285900 326700 449200 - -
M39 976 244000 341600 390400 487900 244000 341600 390400 536700 - -
  • a Proof load values have been calculated from the exact figures of As,nom as specified in ISO 3506-1 and rounded to the next upper 10 N up to 100 000 Nand to the next 100 N above.
  • b Property class 025 refers to the austenitic grades A1 to A5 only

Proof load values for thin nuts with fine pitch thread (reduced loadability)

Thread D×P Nominal stress area As,nom Proof load, Fpf a N
Austenitic and duplex steels Martensitic steels Ferritic steels
025b 35 40 50 25 35 40 55 22 30
M8×1 39,2 9800 13710 15670 19590 9800 13710 15670 21550 8820 11760
M10×1,25 61,2 15300 21420 24480 30600 15300 21420 24480 33660 13770 18360
M10×1 64,5 16130 22580 25800 32250 16130 22580 25800 35480 14520 19350
M12×1,5 88,1 22040 30850 35260 44070 22040 30850 35260 48470 19830 26440
M12×1,25 92,1 23020 32230 36830 46040 23020 32230 36830 50640 20720 27630
M14×1,5 125 31140 43600 49820 62280 31140 43600 49820 68510 28030 37370
M16×1,5 167 41820 58540 66900 83630 41820 58540 66900 91990 37640 50180
M18×1,5 216 54060 75690 86500 108200 54060 75690 86500 119000 48660 64880
M20×2 258 64500 90300 103200 129000 64500 90300 103200 141900 58050 77400
M20×1,5 272 67880 95030 108700 135800 67880 95030 108700 149400 61090 81460
M22×1,5 333 83270 116600 133300 166600 83270 116600 133300 183200 74940 99920
M24×2 384 96110 134600 153800 192300 96110 134600 153800 211500 86500 115400
M27×2 496 124000 173600 198300 247900 124000 173600 198300 272700 - -
M30×2 621 155400 217500 248500 310700 155400 217500 248500 341700 - -
M33×2 761 190200 266300 304400 380400 190200 266300 304400 418500 - -
M36×3 865 216300 302800 346000 432500 216300 302800 346000 475800 - -
M39×3 1030 257100 360000 411400 514200 257100 360000 411400 565700 - -
  • a Proof load values have been calculated from the exact figures of As,nom as specified in ISO 3506-1 and rounded to the next upper 10 N up to 100 000 Nand to the next 100 N above.
  • b Property class 025 refers to the austenitic grades A1 to A5 only.

ISO 3506-2 Nut Nominal Dimensions

Thread D Width across flats S Minimum height of hexagon nuts
Regular nut (style 1) High nut (style 2)
m min m min/D m min m min/D
M5 8 4,40 0,88 4,80 0,96
M6 10 4,90 0,82 5,40 0,90
M7 11 6,14 0,88 6,84 0,98
M8 13 6,44 0,81 7,14 0,90
M10 16 8,04 0,80 8,94 0,89
M12 18 10,37 0,86 11,57 0,96
M14 21 12,10 0,86 13,40 0,96
M16 24 14,10 0,88 15,70 0,98
M18 27 15,10 0,84 16,90 0,94
M20 30 16,90 0,85 19,00 0,95
M22 34 18,10 0,82 20,50 0,93
M24 36 20,20 0,84 22,60 0,94
M27 41 22,50 0,83 25,40 0,94
M30 46 24,30 0,81 27,30 0,91
M33 50 27,40 0,83 30,90 0,94
M36 55 29,40 0,82 33,10 0,92
M39 60 31,80 0,82 35,90 0,92

ISO 3506-2 Property Class Marking

Property class marking (Regular and High nuts)

Property Class Marking
ISO 3506-2 Class 45 TB 45
ISO 3506-2 Class 50 TB 50
ISO 3506-2 Class 60 TB 60
ISO 3506-2 Class 70 TB 70
ISO 3506-2 Class 80 TB 80
ISO 3506-2 Class 100 TB 100
ISO 3506-2 Class 110 TB 110

Property class marking (Thin nuts)

Property Class Marking
ISO 3506-2 Class 45 TB 022
ISO 3506-2 Class 50 TB 025
ISO 3506-2 Class 60 TB 030
ISO 3506-2 Class 70 TB 035
ISO 3506-2 Class 80 TB 040
ISO 3506-2 Class 100 TB 050
ISO 3506-2 Class 110 TB 055

ISO 3506-2 Heat Treatment

Regular and high nuts of grades and property classes C1-70, C3-80 and C4-70, and thin nuts of grades and property classes C1-035, C3-040 and C4-035 shall be quenched and tempered.
Regular and high nuts of grade and property class C1-110 and thin nuts of grade and property class C1- 055 shall be quenched and tempered, with a minimum tempering temperature of 275 °C.

ISO 3506-2 Bolting Surface Treatment Specifications