无缝方矩管的力学性能是保证无缝方矩管使用性能（机械性能）的重要指标，它取决于钢管的化学成分和热处理制度。所以根据不同的使用要求，从抗拉强度、屈服点、伸长率这几方面来具体的介绍下大口径螺旋钢管的力学性能。

55世纪The mechanical property of seamless rectangular tube is an important index to ensure the service performance (mechanical property) of seamless rectangular tube, which depends on the chemical composition and heat treatment system of steel tube. Therefore, according to different application requirements, the mechanical properties of large-diameter spiral steel pipe are introduced from the aspects of tensile strength, yield point and elongation.

无缝方矩管的力学性能是保证无缝方矩管使用性能（机械性能）的重要指标，它取决于钢管的化学成分和热处理制度。所以根据不同的使用要求，从抗拉强度、屈服点、伸长率这几方面来具体的介绍下大口径螺旋钢管的力学性能。

The mechanical property of seamless rectangular tube is an important index to ensure the service performance (mechanical property) of seamless rectangular tube, which depends on the chemical composition and heat treatment system of steel tube. Therefore, according to different application requirements, the mechanical properties of large-diameter spiral steel pipe are introduced from the aspects of tensile strength, yield point and elongation.

1抗拉强度试样在拉伸过程中，在拉断时所承受的力（Fb），出以试样原横截面积（So）所得的应力（σ），称为抗拉强度（σb），单位为N/mm2（MPa）。它表示金属材料在拉力作用下抵抗破坏的能力。

55世纪1. The stress (FB) borne by the tensile strength sample during breaking in the tensile process is the stress obtained from the original cross-sectional area (so) of the sample（ σ）， Called tensile strength（ σ b) , in N / mm2 (MPA). It represents the ability of metal materials to resist failure under tension.

2屈服点具有屈服现象的金属材料，试样在拉伸过程中力不增加（保持恒定）仍能继续伸长时的应力，称屈服点。若力发生下降时，则应区分上、下屈服点。屈服点的单位为N/mm2（MPa）。

2 yield point the stress of the metal material with yield phenomenon when the specimen can continue to elongate without increasing (keeping constant) the stress during the tensile process, which is called the yield point. If the stress decreases, the upper and lower yield points shall be distinguished. The unit of yield point is n / mm2 (MPA).

55世纪3断后伸长率在拉伸试验中，试样拉断后其标距所增加的长度与原标距长度的百分比，称为伸长率。以σ表示，单位为%。

3 elongation after fracture in the tensile test, the percentage of the length increased by the gauge length of the sample after breaking to the original gauge length is called elongation. with σ Expressed in%.

今年上半年q345b方管市场价格将会出现“慢涨快跌”的一种运行状态，“慢涨”的原因是由于成本的推动，这种成本推动体现在钢厂因原料市场价格的上涨，生产成本上升，促使钢厂出厂价格的上调；再有，钢材贸易商的采购成本提高，后期投放市场的采购价格普遍增，但考虑到下游终端用户的承受能力，现货市场上的价格不会一下子大幅上涨，而表现为缓慢稳步而上。而“快跌”则是受宏观政策面、钢材金融属性以及人为的炒作等原因，一旦钢价出现震荡回落的情况，这些不利因素的叠加效应集中显现，导致市场价格的快速下跌。

In the first half of this year, Q345B Fangguan's market price will be in a running state of "slow rise and fast fall". The reason for the "slow rise" is due to the promotion of cost, which is reflected in the increase of production cost of steel mills due to the rise of raw material Market price; In addition, the purchase cost of steel traders has increased, and the purchase price put on the market in the later stage has generally increased. However, considering the affordability of downstream end users, the price in the spot market will not rise sharply at once, but will rise slowly and steadily. The "rapid decline" is due to macro policy, steel financial attributes and artificial speculation. Once the steel price fluctuates and falls, the superposition effect of these adverse factors will appear, resulting in the rapid decline of market price.