ISO 898-1 Hex Head Bolt Grade 8.8 Specification:

Due to the globalization of fasteners production, it’s important to understand the raw materials specifications. The ISO 898-1:2013, describes the raw materials for screws in steel. When analyzing different solutions, one of the key factors should be that steel quality. This difference will change the price levels, and can generate important issues on the final application. Bellow, we present the screw property class, the raw material used for each property and some characteristics.

ISO 898-1:2013 grade 8.8 Chemical Composition：

Property class	Material and heat treatment	Chemical composition limit (cast analysis, %)a					Tempering temperature ⁰CMin.
		C		P	S	Bb
		min.	max.	max.	max.	max.
8.8	Carbon steel with additives (e.g. Boron or Mn or Cr) quenched and tempered	0,15e	0,40	0,025	0,025	0,003	425
	Carbon steel quenched and tempered	0,25	0,55	0,025	0,025
	Alloy steel quenched and temperedg	0,20	0,55	0,025	0,025

ISO 898-1:2013 Grade 8.8 Mechanical Properties

Mechanical or physical property		Tensile strength, Rm, MPa		Stress at 0,2 % non-proportional elongation, Rp0,2, MPa		Stress under proof load, Spf, MPa	Proof strength ratioSp,nom/ReL,min	Percentage elongation after fracture for machined test pieces, A, %	Percentage reduction of area after fracture for machined test pieces, Z, %	Height of non-decarburized thread zone, E, mm	Depth of complete decarburization in the thread, G, mm	Reduction of hardness after retempering, HV	Impact strength, KVij, J
		nom.c	min.	nom.c	min.	nom.		min.	min.	min.	max.	max.	min.
8.8	d≤ 16 mma	800	800	640	640	580	0,91	12	52	1/2 H1	0,015	20	27
	d> 16 mmb		830	640	660	600	0,91				0,016	21	27

ISO 898-1:2013 grade 8.8 Recommended Hardness

Mechanical or physical property		Vickers hardness,HV F ≥98 N		Brinell hardness, HBW F = 30 D2		Rockwell hardness, HRC		Surface hardness, HV 0,3
		min.	max.	min.	max.	min.	max.	max.
8.8	D ≤ 16 mma	250	320	245	316	22	32	–
	D > 16 mmb	255	335	250	331	23	34	–

High Strength Hex Head Bolt Application: