Three-level threaded steel is now commonly referred to as HRB400 steel bar, and now there are three-level seismic threaded steel, that is, HRB400E steel bar, a kind of hot-rolled ribbed steel bar, in construction, three-level threaded steel is the past name. Three-grade threaded steel is currently divided into two grades, one is HRB400, the other is HRB400E. Fine-grained hot-rolled steel bar, its brand ah, hot-rolled ribbed steel bar abbreviated in English with the first letter of "thin", such as: HRBF335, HRBF400, HRBF500. The applicable brand of aseismic structures with higher requirements is to add E after the existing brand. Its main use is widely used in civil engineering such as houses, bridges, roads, especially railways.
For the understanding of the bending properties of the third-grade threaded steel, according to the requirements of the demand side, the threaded steel can carry out the reverse bending performance test. The bending center diameter of the reverse bending test correspondingly increases a diameter of the threaded steel compared with the bending test. First, the forward bending is 45 degrees, then the reverse bending is 23 degrees, and then the reverse bending is 23 degrees. After the reverse bending test, the surface of the bending part of the threaded steel can not produce cracks. The surface quality of threaded steel does not allow cracks, scarring and folding. The surface of the threaded steel is allowed to have bumps, but not more than the height of the transverse ribs. The depth of other defects on the surface of the threaded steel should not be greater than the allowable deviation of the size of the location.
Finally, look at the mechanical properties of three-stage threaded steel, in which the yield point refers to the physical yield strength. During the tensile process, the load does not increase or begin to decrease, and the specimen can continue to deform at a constant time. The maximum or minimum load divided by the stress of the original cross-sectional area is the yield point, the upper yield point and the lower yield point of the specimen, respectively. Tensile strength refers to the ultimate strength. When a specimen is tensioned, the maximum load it bears before breaking is divided by the stress of the original cross-sectional area. It is called tensile strength. It represents the maximum ability of the threaded steel to resist damage under the action of tension. The elongation is the elongation. The percentage of the length of the gauge to the original gauge is called the elongation after the specimen is broken.
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