Bu lông cường độ cao 8.8

What is high strength bolt 8.8

High strength bolts 8.8 or Grade 8.8 bolts are bolts with the following mechanical properties:

The value 8.8 is the value that represents the strength level of the bolt. A bolt with strength level 8.8 means that the first number multiplied by 100 gives us the minimum strength limit value (MPa), the second number divided by 10 gives us the ratio between the yield limit and the strength limit (Mpa).

Thus, high strength bolt 8.8 is a high strength bolt with a minimum tensile strength of 8×100 = 800Mpa, yield strength is 800 x (8 / 10) = 640 Mpa.

Technical specifications of grade 8.8 bolts:

– Size:

Diameter: From M5 to M72

Thread pitch: 01 – 06mm

Common length: From 10mm – 300mm

– Manufacturing material: Carbon steel

– Durability level: 8.8

– Surface: black oxide, electroplating, hot-dip galvanized, Dacromet plating, Geomet plating, black dyeing, etc.

– Origin: Vietnam, Korea, Taiwan….

Production standards for grade 8.8 bolts:

High strength bolts 8.8 are manufactured according to the following standards: DIN (Germany), JIS (Japan), ISO (International Standards), ASTM/ANSI (USA), BS (UK), GB (China), GOST (Russia) and TCVN (Vietnam).

In the Vietnamese market, we commonly use high strength bolts 8.8 according to German DIN standards. 

Here Tho An would like to introduce to customers the production standards of the two most popular types of bolts: 

Bolts grade 8.8 according to DIN 933 standard (full thread):

d	M4	M5	M6	M8	M10	M12	M14	M16	M18	M20	M22
P	0.7	0.8	1	1.25	1.5	1.75	2	2	2.5	2.5	2.5
k	2.8	3.5	4	5.3	6.4	7.5	8.8	10	11.5	12.5	14
s	7	8	10	13	17	19	22	24	27	30	32
d	M24	M27	M30	M33	M36	M39	M42	M45	M48	M52	M56
P	3	3	3.5	3.5	4	4	4.5	4.5	5	5	5.5
k	15	17	18.7	21	22.5	25	26	28	30	33	35
s	36	41	46	50	55	60	65	70	75	80	85

High strength bolt 8.8 full thread

Bolts grade 8.8 according to DIN 931 standard (half thread):

d	M4	M5	M6	M8	M10	M12	M14	M16	M18	M20	M22
P	0.7	0.8	1	1.25	1.5	1.75	2	2	2.5	2.5	2.5
k	2.8	3.5	4	5.3	6.4	7.5	8.8	10	11.5	12.5	14
s	7	8	10	13	17	19	22	24	27	30	32
b1, L≤125	14	–	18	22	26	30	34	38	42	46	50
b2, 125<L≤200	–	22	24	28	32	36	40	44	48	52	56
b3, L>200	–	–	–	–	–	–	–	57	61	65	69
d	M24	M27	M30	M33	M36	M39	M42	M45	M48	M52	M56
P	3	3	3.5	3.5	4	4	4.5	4.5	5	5	5.5
k	15	17	18.7	21	22.5	25	26	28	30	33	35
s	36	41	46	50	55	60	65	70	75	80	85
b1, L≤125	54	60	66	72	78	84	90	96	102	–	–
b2, 125<L≤200	60	66	72	78	84	90	96	102	108	116	124
b3, L>200	73	79	85	91	97	103	109	115	121	129	137

Materials for manufacturing 8.8 Bolts:

The materials used to produce 8.8 bolts are also different from the materials used to produce regular bolts and often require the material to have higher strength and hardness, or have certain elements such as Cr, Ma, etc. in the material composition. The following are symbols of some materials commonly used to produce high-strength bolts: 30X, 35X, 40X, 30Cr, 35Cr, Scr420, Scr430.

Applications of Grade 8.8 Bolts: