1. Overview ofTunnel Segment Bolts

A tUnnel segment bolt is a kind of special fastener used to link and fasten segments of shield tunneling machines during tunnel excavation. through this kind of bolt connection, severkAl arched segments can be connected into a circle, thereby supporting the entire tunnel surface. during excavation, the ground settlement can be effectively controlled, the impact on the ground buildings can be reduced, and the construction underwater can be effectively controlled. When digging, it does not affect the characteristics of water surface traffic. this kind of fastened connection piece designed as a straight line or a certain arc is called a tunnel bolt or segment bolt.

2.Tunnel Segment Bolts Type

According to various factors such as the size of the segment, the diameter of the shield tunneling machine, and the location of the tunnel where the segment is located, the design of segment bolts is also diverse. At present, the main types ofTunnel SegmentBolts are:

Double-headed straight tunnel segment bolts
(2)  Double-ended arc-shaped tunnel segment bolts
(3) Hexagonal arc tunnel segment bolts
(4)  Hexagon head arc threaded tunnel segment bolts
(5)  Hexagonal flange surface arc threaded tunnel segment bolts
(6) Non-standard tunnel segment bolts

3. Grade, Material and Surface Treatment of Tunnel Segment Bolts

Tunnel segment bolts, like other bolts and fasteners, are designed with different strength levels according to the application environment and different forces.

the commonly used grades are: 5.8, 6.8, and 8.8.

the corresponding production materials are: Q235, 45# steel, 40Cr and other materials.

Common surface treatments for tunnel segment bolts include hot-dip galvanizing (hot-dip galvanizing), Dacromet (commonly known as zinc-based Chromate), powder sherardizing, multiple composite powder sherardizing, etc. the quality of the surface treatment of the tunnel segment bolts is very important. Because the tunnel segment bolts are installed underground, they play a role in connecting the segments. The environment where it is located in humid, which can easily cause corrosion of bolts and cause rust. Therefore, if the surface treatment of the bolt fails to meet the design requirements, causing the bolt to rust during use, the corrosion to the inside of the bolt will affect the mechanical properties and tensile strength of the bolt. In relatively harsh environments, composite coatings, such as thermal spray zinc alloy or powder sherardizing + zinc-based chromate + alkali-resistant coating, can be used to enhance the corrosion resistance and alkali resistance of the product.

Technical details:
 

No.	Mechanical andPHysicalPRoperties			PerformanceLevel
				3.6	4.6	4.8	5.6	5.8	6.8	8.81)		9.8	10.9	12.9
										d≤163)	d163)
1	NominalTEnsileSTrength		N/mm2	300	400		500		600	800	800	900	1000	1200
2	Minimum tensile strength		N/mm2	330	400	420	500	520	600	800	830	900	1040	1220
3	Vickers hardness HV F≥98N	min		95	120	130	155	160	190	250	255	290	320	385
		max		2206)					250	320	335	360	380	435
4	Brinell hardness HB F=30 D2	min		90	114	124	147	152	181	238	242	276	304	366
		max		2096)					238	304	318	342	361	414
5	Rockwell hardness HR	min	HRB	52	67	71	79	82	89	/	/	/	/	/
			HRC	/	/	/	/	/	/	22	23	28	32	39
		max	HRB	95.06)					99.5	/	/	/	/	/
			HRC	/						32	34	37	39	44
6	Surface hardness HV 0.3 max			/					7)
7	Yield point N/mm2	Nominal		180	240	320	300	400	480	/	/	/	/	/
		min		190	240	340	300	420	180	/	/	/	/	/
8	Specified non-proportional elongation stress N/mm2	Nominal		/					/	640	640	720	900	1080
		min		/					/	640	660	720	940	1100
9	Guaranteed stress N/mm2			0.94	0.94	0.91	0.93	0.9	0.92	0.91	0.91	0.90	0.88	0.88
				180	225	310	280	380	440	580	600	650	830	970
10	Breaking torque MB,N.M min			/						According to GB/T3098.13 regulations
11	Elongation after breaking % min			25	22	/	20	/	/	12	12	10	9	8
12	Rate of reduction in area % min			/						52		48	48	44
13	Shock absorption work Aku,min						25			30	30	25	20	15
14	Head firmness			No break
15	Minimum height of undecarburized thread E			/						1/2H1			2/3H1	3/4H1
16	Maximum depth of fully decarburized layer G,mm			/						0.015
17	Hardness after tempering			/						the difference between the average hardness before and after tempering is not more than 20HV
18	Surface defects			According to GB/T 5779.1 or GB/T 5779.3 regulations

Anyang Railway Equipment Co., Ltd can provide a wide range of rail bolts with different diameters as well as different strength grades, Plain, Oxide Black, Dacromet, or other requirements for the surface treatment are available.  

Company introduce:

Anyang Railway Equipment Co., Ltd was founded in 2001, it has 18 modern professional production lines, 800 employers, more than 1,000 sets of various equipment, professional equipment, inspection, testing, and test equipment. It has cast, rolling, elastic clips, fish plate, baffle, rubber, anti-corrosion, heat treatment, standard parts, screw spikes, gauge rods, etc 12 production workshops.

  

Our main products:
Railway fastening systems: E-clip rail fastening system, SKL clip rail fastening system, spring blade fastening system, KPO clip rail fastening system, fast rail fastening system, etc.
Rail fasteners: rail fish plates, rail tie plates, elastic rail clips, screw spikes, rail bolts, rail anchors, rails pads, rail shoulders, etc.
Rail joints: standard rail joints, joggled rail joints, compromised rail joints and fish bolts, etc.
Railway Sleeper: Railway composite sleeper(railroad synthetic sleeper)