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Tail Bolt Uses

1. Tail bolts are mainly used in the metallurgy, coking, and steel industries for track laying, fastening joints between rails.

2. The models and material types of tail bolts include

Φ14×70, Φ16×75, Φ18×90, Φ20×90, Φ22×135, Φ24×135, Φ24×145, Φ24×170, etc. They are generally hot-pressed and formed by friction press, with a thread length of 50mm, and there are also cold-headed types, mostly used for connecting rail joints.

Materials include Q235, 45# steel, and insulated tail bolts, etc.

Meaning of Fish Tail Bolt Grades

According to relevant standards, bolt performance grades are divided into more than ten levels, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and undergo heat treatment (quenching and tempering), commonly referred to as high-strength bolts, while the others are commonly referred to as ordinary bolts. The bolt performance grade number consists of two digits, representing the nominal tensile strength and the yield ratio of the bolt material. For example:

For a bolt of performance grade 4.6, its meaning is:

1. The bolt material has a nominal tensile strength of 400 MPa;

2. The yield-to-tensile ratio of the bolt material is 0.6;

3. The nominal yield strength of the bolt material is 400 × 0.6 = 240 MPa.

For a high-strength bolt of performance grade 10.9, after heat treatment, the material can reach:

1. The bolt material has a nominal tensile strength of 1000 MPa;

2. The yield-to-tensile ratio of the bolt material is 0.9;

3. The nominal yield strength of the bolt material is 1000 × 0.9 = 900 MPa.

The meaning of bolt performance grades is an internationally recognized standard. Bolts with the same performance grade have the same performance regardless of material or origin. In design, only the performance grade needs to be selected.

The strength grades 8.8 and 10.9 refer to the bolt's shear stress levels of 8.8 GPa and 10.9 GPa, respectively.

For grade 8.8, the nominal tensile strength is 800 N/mm², and the nominal yield strength is 640 N/mm².

Generally, bolts use the "X.Y" format to indicate strength:

X * 100 = tensile strength of the bolt,

X * 100 * (Y / 10) = yield strength of the bolt

(Because according to the marking regulations: yield strength / tensile strength = Y / 10).

Fish Bolts (professionally known as rail joint bolts) are critical fasteners used to connect rail sections in railways and industrial mining tracks.

Their core functions and features are as follows:

· Core Function: When used together with fish plates (joint bars), they tightly fasten two rail ends together to ensure track smoothness. Since the rail joint is the weakest point of the track, the tightening condition of fish bolts directly affects train operation safety.

· Structural Features: The head is not a standard hexagon, but a specially designed countersunk oval neck. Just below the head is an elliptical neck that fits into the elliptical hole of the fish plate, effectively preventing rotation when tightening the nut.

· Common Models:

  · Diameter: Typically Φ16, Φ20, Φ22, Φ24 mm

  · Length: Ranges from 70 mm to 170 mm, depending on the rail model

  · Materials: Q235 (ordinary), 45# steel (higher strength), 40Cr/42CrMo (high strength)

· Strength Grades:

  · Grade 4.8 (ordinary)

  · Grade 8.8 (high strength, marked with a raised ridge on the head)

  · Grade 10.9 (high strength, with a flat truncated cone top)