Mechanical and Physical Properties of Screws

No.	Mechanical or physical property	nom.c min.	Property class
No.	Mechanical or physical property	nom.c min.	4.6	4.8	5.6	5.8	6.8	8.8 d = 16mm	8.8 d > 16mm	9.8	10.9	12.9
1	Tensile strength, Rm, MPa, [N/mm2]	nom.c min.	400 400	400 420	500 500	500 520	600 600	800 800	800 830	900 900	1000 1040	1200 1220
2	Lower yield strength, ReLd, MPa, [N/mm2]	nom.c min.	240 240	–	300 300	–	–	–	–	–	–	–
3	Stress at 0.2% non-proportional elongation, Rp0.2, MPa, [N/mm2]	nom.c min.	–	–	–	–	–	640 640	640 660	720 720	900 940	1080 1100
4	Stress at 0.0048 d non-proportional elongation for full-size fasteners, Rpf, MPa, [N/mm2]	nom.c min.	–	320 340	–	400 420	480 480	–	–	–	–	–
5	Stress under proof load, Sp, MPa, [N/mm2] Proof strength ratio: Sp,nom / ReL min Sp,nom / Rp0.2 min Sp,nom / Rpf min	nom.	225 0.94	310 0.91	280 0.93	380 0.90	440 0.92	580 0.91	600 0.91	650 0.90	830 0.88	970 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	52	48	48	44
8	Elongation after fracture for full-size fasteners, At see also ISO 898-1 Annex C	min.	–	–	0.24	–	0.22	0.20	–	–	–	–
9	Head soundness	–	no fracture
10	Vickers hardness, HV (F = 98 N)	min. max.	120 220g	130 220g	155 220g	160 220g	190 250	250 320	255 335	290 360	320 380	385 435
11	Brinell hardness, HBW (F = 30 D²)	min. max.	114 209g	124 209g	147 209g	152 209g	181 238	238 304	242 318	276 342	304 361	366 414
12	Rockwell hardness, HRB Rockwell hardness, HRC	min. max. min. max.	67 95,0g – –	71 95,0g – –	79 95,0g 22 32	82 95,0g 23 34	89 99,5 28 37	– – 32 39	– – – 44	– – – –	– – – –	– – – –
13	Surface hardness, HV 0,3	max.	–	–	–	–	–	h	h	h	h,i	h,j
14	Height of non-decarburized thread zone, E, mm Depth of complete decarburization in the thread, G, mm	min. max.	– –	– –	– 0,015	– 0,015	– 0,015	½ H₁ 0,015	½ H₁ 0,015	½ H₁ 0,015	? H₁ 0,015	¾ H₁ 0,015
15	Reduction of hardness after retempering, HV	max.	–	–	–	–	–	20	20	20	20	20
16	Breaking torque, M_B, Nm	min.	in accordance with ISO 898-7
17	Impact strength KV k,l, J	min.	–	–	27	–	27	27	27	27	27	m
18	Surface integrity in accordance with	ISO 6157-1ⁿ					ISO 6157-3

a Values do not apply for structural bolting.
b For structural bolting d = 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 F.006.
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.
l Applies to d = 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.