ISO 898-1 Specification

This part of ISO 898 specifies mechanical and physical properties of bolts, screws and studs made of carbon steel and alloy steel when tested at an ambient temperature range of 10 °C to 35 °C. Fasteners — the term used when bolts, screws and studs are considered all together — that conform to the requirements of this part of ISO 898 are evaluated at that ambient temperature range. They might not retain the specified mechanical and physical properties at elevated temperatures (see Annex B) and/or lower temperatures.

ISO 898-1 Chemical Composition

Property class Material and heat treatment Chemical composition limits
(cast analysis, %) a		 Tempering temperature
·c
nin.
c p
max.		 s
max.		 a •
max.
min. max.
4.6 c, d Carbon steel or carbon steelwith additives - 055 0.050 0,060 Not specified -
4.8 d
5.6 c 013 055 0.050 0,060
5.8 d - 055 0.050 0,060
6.8 d 015 055 0.050 0,060
8.8 f Carbon steel with additives (e.g. Boron or Mn or Cr) quenched and tempered 015. 040 0.025 0,025 0,003 425
or
Carbon steel quenched and tempered		 025 055 0.025 0,025
or
Anoy steelquenched and tempered 9		 020 055 0.025 0,025
9.8 f Carbon steel with additives (e.g. Boron or Mn or Cr) quenched and tempered 015. 040 0,025 0,025 0,003 425
or
Carbon steel quenched and tempered		 025 055 0.025 0,025
or
Alloy steelquenched and tempered 9		 020 055 0.025 0,025
10.9 f Carbon steel with additives (e.g. Boron or Mn or Cr) quenched and tempered 0,20 . 055 0,025 0,025 0,003 425
or
Carbon steel quenched and tempered		 025 055 0.025 0,025
or
Alloy steel quenched and tempered 9		 020 055 0,025 0,025
12..9 f.h.i Alloy steel quenched and tempered 9 030 050 0.025 0,025 0,003 425
12..9 f.h.i Carbon steel with additives (e.g. Boron or Mn or Cr or Molybdenum)quenched and tempered 028 050 0.025 0,025 0,003 380
Note:
a. In case of dispute, the product analysis applies.
b. Boron content can reach 0,005 %, provided that non-effective boron is controlled by addition of titanium and/or aluminium.
c. For cold forged fasteners of property classes 4.6 and 5.6, heat treatment of the wire used for cold forging or of the cold forged fastener itself may be necessary to achieve required ductility.
d. Free cutting steel is allowed for these property classes with the following maximum sulphur, phosphorus and lead contents: sulphur 0,34 %; phosphorus 0,11 %; lead 0,35 %.
e. In case of plain carbon boron steel with a carbon content below 0,25 % (cast analysis), the minimum manganese content shall be 0,6 % for property class 8.8 and 0,7 % for 9.8 and 10.9.
f. For the materials of these property classes, there shall be a sufficient hardenability to ensure a structure consisting of approximately 90 % martensite in the core of the threaded sections for the fasteners in the “as-hardened” condition before tempering.
g. This alloy steel shall contain at least one of the following elements in the minimum quantity given: chromium 0,30 %, nickel 0,30 %, molybdenum 0,20 %, vanadium 0,10 %. Where elements are specified in combinations of two, three or four and have alloy contents less than those given above, the limit value to be applied for steel class determination is 70 % of the sum of the individual limit values shown above for the two, three or four elements concerned.
h. A metallographically detectable white phosphorus enriched layer is not permitted for property class 12.9/12.9. It shall be detected by a suitable test method.
i. Caution is advised when the use of property class 12.9/12.9 is considered. The capability of the fastener manufacturer, the service conditions and the wrenching methods should be considered. Environments may cause stress corrosion cracking of fasteners as processed as well as those coated.

ISO 898-1 Mechanical Requirements

No. Mechanical or physical property Property class
4.6 4.8 5.6 5.8 6.8 8.8 9.8
d ≤ 16 mm 		10.9 12.9/ 12.9
d≤
16
mm 		d >
16
mm
1 Tensile strength, Rm, MPa nom.c 400 500 600 900 900 HXll 1200
min.   420 500 520 600 800 830 900 100 1220
2 Lower yield strength, ReL d, MPa nom.c 240 - 300 - - - - - - -
min. 240 - 300 - - - - - - -
3 Stress at 0,2 % non· proportional elongation,
Rp0.2' MPa		 nom.c - - - - - 640 640 720 900 1080
min. - - - - - 640 660 720 940 1100
4 Stress at 0,0048 d non-proportional elongation for full-size fasteners, Rpf, MPa nom.c - 320 - 400 480 - - - - -
min. - 340e - 420e 48e - - - - -
5 Stress under proof load, Sp,f,MPa  nom.c 225 310 280 380 440 580 600 650 830 970
Proof strength ratio Sp,nom/ReL min or Sp,nom/Rp0,2 min or Sp,nom/Rpf min min. 094 091 0.93 090 0.92 0.91 0.91 0.90 0.88 0.88
6 Percentage elongation after fracture for machined test pieces, A, % min. 22 - 20 - - 12 12 10 9 8
7 Percentage reduction of area after fracture for machined test pieces, Z, % min. - 52 48 48 44
8 Elongation after fracture for full-size fasteners, Af (see also Annex C) min. - 0.24 - 0.22 0.20 - - - - -
9 Head soundness No fracture
10 Vickers hardness, HV F W 98 N min. 120 130 155 160 190 250 255 290 320 385
max. 220 g 250 320 335 360 380 435
11 Brinell hardness, HBW F = 30 D2 min. 114 124 147 152 181 238 242 276 304 366
max. 209 g 238 304 318 342 361 414

12		 Rockwell hardness, HRB min. 67 71 79 82 89 —
max. 95,0 g 99,5 —
Rockwell hardness, HRC min. - 22 23 28 32 39
max. - 32 34 37 39 44
13 Surface hardness, HV 0,3 max. — h h, i h, j
14 Height of non-decarburized thread zone, E, mm min. — 1/2 H1 2 /3 H1 3 /4H1
Depth of complete decarburization in the thread, G, mm max. — 0,015
15 Reduction of hardness after retempering, HV max. — 20
16 Breaking torque, MB, Nm min. — in accordance with ISO 898-7
17 Impact strength, KV k, l, J min. — 27 — 27 27 27 27 m
18 Surface integrity in accordance with ISO 6157-1 n ISO 6157-3
Note:
a. Values do not apply for structural bolting.
b. For structural bolting d W M12.
c. Nominal values are specified only for the purpose of the designation system for property classes. See Clause 5.
d. In cases where the lower yield strength ReL cannot be determined, it is permissible to measure the stress at 0,2 % non-proportional elongation Rp0,2.
e. For the property classes 4.8, 5.8 and 6.8 the values for Rpf min are under investigation. The present values are given for calculation of the proof stress ratio only. They are not test values.
f. Proof loads are specified in Tables 5 and 7.
g. Hardness determined at the end of a fastener shall be 250 HV, 238 HB or 99,5 HRB maximum.
h. Surface hardness shall not be more than 30 Vickers points above the measured core hardness of the fastener when determination of both surface hardness and core hardness are carried out with HV 0,3.
i. Any increase in hardness at the surface which indicates that the surface hardness exceeds 390 HV is not acceptable.
j. Any increase in hardness at the surface which indicates that the surface hardness exceeds 435 HV is not acceptable.
k. Values are determined at a test temperature of −20 °C, see 9.14.
l.Applies to d W 16 mm.
m. Value for KV is under investigation.
n. Instead of ISO 6157-1, ISO 6157-3 may apply by agreement between the manufacturer and the purchaser.