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.

　　對于三級螺紋鋼的彎曲性能的了解，根據需方要求，螺紋鋼可以進行反向彎曲性能試驗，反向彎曲試驗的彎心直徑比彎曲試驗相應增加一個螺紋鋼直徑，先正向彎曲45度，后反向彎曲23度，后反向彎曲23度，經反向彎曲試驗后，螺紋鋼受彎曲部位表面不得產生裂紋。螺紋鋼的表面質量，不允許有裂紋、結疤和折疊。螺紋鋼的表面允許有凸塊，但是不得超過橫肋的高度，螺紋鋼表面上其他缺陷的深度不得大于所在部位尺寸的允許偏差。

　　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.

　　后看看三級螺紋鋼的力學性能，其中屈服點指的就是物理屈服強度，試樣在拉伸的過程中，負荷不增加或者開始降低，試樣仍然能夠繼續的變形時恒定，大或小負荷除以原橫截面積所得的應力，分別為試樣的屈服點、上屈服點和下屈服點。抗拉強度指的是強度極限，試樣拉伸時，在拉斷前所承受的大負荷除以原橫截面積所得的應力，稱為抗拉強度，它表示螺紋鋼在拉力的作用下，抵抗破壞的大能力。伸長率也就是延伸率，試樣拉斷后，其標距部分所增加的長度與原標距長度的百分比，稱為伸長率。

　　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.

　　以上就是三級螺紋鋼的相關知識了解，后期將有更加的知識系統，希望行業內外人士多多的關注我們網站。

　　Above is the knowledge of three-level threaded steel. Later, there will be a more comprehensive knowledge system. I hope that people inside and outside the industry will pay more attention to our website.