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Steel structure with high-strength large hexagonal bolt connection pair testing items
2024-04-26
The full name of steel structure bolts is called steel structure with high-strength large hexagonal head bolt connection pair, which belongs to high-strength bolts. At present, the current national standard is GB/T1228~1231-2006. Steel structure bolts are mainly used in the construction of industrial and civil buildings, railway bridges, highway bridges, pipeline bridges, tower mast structures, boiler frames, boiler steel structures, long-span industrial plants, high-rise civil buildings, various towers, light steel structures, lifting machinery and other steel structure connection buildings. The application scenario has high quality requirements for high-strength bolts and long service life, and the quality acceptance of this kind of bolt connection pair is relatively strict. So what are the test items for bolted connections of steel structures?
1. The factory inspection is carried out in batches.
Bolts of the same performance level, material, heat number, thread specification, length (when the bolt length is less than or equal to 100GB/T 1231-202× mm, the length difference is less than or equal to 15 mm; when the bolt length is greater than 100mm, the length difference is less than or equal to 20 mm, it can be regarded as the same length), machining, heat treatment process, surface treatment type of bolts are the same batch; the same performance grade, material, heat number, thread specification, machining, heat treatment process, The nuts of the surface treatment type are in the same batch, and the gaskets of the same performance grade, material, heat number, specification type, machining, heat treatment process and surface treatment type are the same batch. The bolt connection pair composed of bolts, nuts and washers of the same batch is the bolt connection pair of the same batch. The maximum number of bolting pairs in the same batch is 3000 sets.
2. Determination of torque coefficient.
The inspection of the torque coefficient of the bolted connection pair is selected in batches of 8 sets, and the ambient temperature and humidity should be recorded at the same time when this test is carried out. The equipment, instruments and bolted pairs used in the test should be placed in the environment for at least 2 hours. The torque coefficient test of the bolted joint pair is carried out on the axial force gauge, and each set of bolted joint pair can only be tested once and should not be reused. When assembling the connecting pair, the side of the washer under the nut with an outer chamfer should be facing the nut bearing surface. During the test, the tightening torque is the torque applied to the nut, and the bolt pretension should be within the range specified in the standard. During the test, the bolt and washer should not rotate, otherwise the test will be invalid.
3. Bolt wedge load test.
A 10° wedge pad is placed under the bolt head, and the bolt is screwed on a special pull tool with internal threads (at least 6 buckles) on the tensile testing machine, and the length of the unscrewed thread should be greater than or equal to 1d, and then the tensile test The type, size and hardness of the 10° wedge pad should comply with the provisions of GB/T3098.1.
4. Nut guarantee load test.
Screw the nut into the threaded mandrel. The speed of movement of the chuck should not exceed 3 mm/min during the test. A guaranteed load specified in the standard is applied to the nut for 15 s, and the nut should not trip or break. When the load is removed, the nut should be unscrewed out by hand or loosened with the help of a wrench (but not over).1/2 buckle) and then unscrew it out by hand. In the test, if the threaded mandrel is damaged, the test is invalidated.
5. Nut and washer hardness test.
The test was carried out on the nut bearing surface (washer surface) at any 4 points, and the average of the last 3 points was taken. The test method shall comply with the provisions of GB/T 230.1 or GB/T 4340.1. During acceptance, if there is any dispute, the Vickers hardness (HV30) test shall be arbitrated.
6. Appearance, size
The inspection and sampling scheme of the size, appearance and surface defects of bolts, nuts and washers shall comply with the provisions of GB/T1228.
7. Summary
When using the steel structure with high-strength bolts for important purposes, we must understand the testing items specified in the standard, only through strict inspection and acceptance, in order to ensure its quality and safety, in order to know how to maintain, in order to improve the service life, and to ensure the quality and safety of the project, the above simply elaborates on the testing items and basic testing methods of the steel structure with high-strength large hexagonal head bolt connection pairs for important purposes, to give you a reference.