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.

　　对于三级螺纹钢的弯曲性能的了解，根据需方要求，螺纹钢可以进行反向弯曲性能试验，反向弯曲试验的弯心直径比弯曲试验相应增加一个螺纹钢直径，先正向弯曲45度，后反向弯曲23度，后反向弯曲23度，经反向弯曲试验后，螺纹钢受弯曲部位表面不得产生裂纹。螺纹钢的表面质量，不允许有裂纹、结疤和折叠。螺纹钢的表面允许有凸块，但是不得超过横肋的高度，螺纹钢表面上其他缺陷的深度不得大于所在部位尺寸的允许偏差。

　　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.

　　后看看三级螺纹钢的力学性能，其中屈服点指的就是物理屈服强度，试样在拉伸的过程中，负荷不增加或者开始降低，试样仍然能够继续的变形时恒定，大或小负荷除以原横截面积所得的应力，分别为试样的屈服点、上屈服点和下屈服点。抗拉强度指的是强度极限，试样拉伸时，在拉断前所承受的大负荷除以原横截面积所得的应力，称为抗拉强度，它表示螺纹钢在拉力的作用下，抵抗破坏的大能力。伸长率也就是延伸率，试样拉断后，其标距部分所增加的长度与原标距长度的百分比，称为伸长率。

　　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.

　　以上就是三级螺纹钢的相关知识了解，后期将有更加的知识系统，希望行业内外人士多多的关注我们网站。

　　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.