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In steel constructions such as bridge spans the high strength fasteners are in a wide use.

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High strength metalware (a set of a bolt, a nut and two flat washers) made of high-quality steel are used to make tight and solid connection of several elements with high bearing capacity and workability.

 

High strength metalware is fabricated in accordance with the Russian standard (GOST 22353-77 …GOST 22356-77).

 

High bolt tension eliminates the possibility for the nut to unscrew during the maintenance of the construction. In steel constructions such as bridge spans the high strength fasteners are in a wide use. High strength metalware substituted the riveted connections used previously. They make so called friction-type joints. These joints provide the transmission of stresses only by forces of friction on the contact surfaces of the adjacent elements. The capacity of the friction-type joint is considered broken if under external loads the relative transference of adjacent elements appears. The bearing capacity of one bolt in the friction-type joint on one bolted connection of the adjacent elements is proportional to the tightening tension and to the slip coefficient on the contact surfaces.

The bearing capacity of one bolted connection with the fixed bolt tension may be changed by proper treatment of the contact surfaces. The wire brushing treatment provides the slip coefficient 0,3...0,4; flame cleaning — 0,4...0,5; shot or sand blasting treatment — 0,5...0,6; covering with glue containing compounds — 0,7...0,8. So the bearing capacity of one bolted connection for the high strength bolts with the diameter of 22 mm by normative tightening tension of 22, 4 tons will be 3...8 tons.

High strength metalware is fabricated in accordance with the Russian standard (GOST 22353-77 …GOST 22356-77). High strength bolts and nuts M22 are mostly used in bridge construction.

Bolts M24 are also produced here; if required the fasteners of other sizes may be produced. The fasteners produced by the Kurganstalmost JSC may be applied in any climatic zone; the lowest temperature of operation is –65 C (type**). High strength bolts and nuts are made of alloy constructional steel 40X "select", Russian Standard (GOST 454371) with the contracted content of the carbon. This guarantees stable mechanical characteristics of the fasteners after the hardening. The ultimate strength is not lower than 110 kg/mm (1100 MPa), the tensile stress for the bolts M22 — not lower than 33, 3 tons.

The bolts are produced from calibrated round bars cut at the required size; the head is formed by hot pressing; the shank is threaded. The nuts are fabricated from hexagons on the semi-automatic machines. The washers are cut from carbon steel strips on the punching machines. The hardening of the fasteners is performed on the automatic line, which secures stable conditions and high quality of technological process. The ready-made fasteners are tested for all geometrical dimensions and thread quality. The mechanical tests such as tensile test, resilience test, determination of turning coefficient and hardness are conducted. All tested parameters shall conform to the technical specifications.

Suitable fasteners are preserved, packed in the transport containers, which protect them from the environmental influence during the storage and transportation. All fasteners are marked and provided with the quality certificate. Before usage the fasteners shall be unpreserved. They are installed and tightened with the usual air power wrenches. In order to provide the best capacity of the bolted connection all contact surfaces shall be properly prepared and the fasteners shall be tightened to the required fixed tension.

The bolts shall be tightened with the properly calibrated wrenches which secure the required torque and the strictly definite bolt tension. Wrenches may be of various designs. Wrenches produced by the Kurganstalmost JSC are simple for handling, especially for field maintenance.

During the maintenance the wrenches shall be periodically calibrated by means of testing tools.

High strength metalware substituted the riveted connections used previously.

High strength bolts and nuts are made of alloy constructional steel 40X "select", Russian Standard (GOST 454371) with the contracted content of the carbon.

All fasteners are marked and provided with the quality certificate. Before used the fasteners shall be unpreserved.
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Russia, Kurgan, 640023 JSC "Kurganstalmost"
ph: (3522) 47-80-58, 47-81-49
fax: (3533) 47-81-17, 47-80-78
E-mail: market@kurganstalmost.ru
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