冷拔无缝钢管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）。 冷拔无缝钢管上屈服点（σsu）：试样发生屈服而力首次下降前的最大应力； 下屈服点（σsl）：当不计初始瞬时效应时，屈服阶段中的最小应力。

Cold-drawn seamless steel tube is a metal material with yielding phenomenon. The stress of the specimen which can continue to elongate without increasing force (keeping constant) in the process of tension is called yield point. If the force decreases, the upper and lower yield points should be distinguished. The yield point is N/mm2 (MPa). Yield point (_su) on cold-drawn seamless steel tube: maximum stress before the first drop in force occurs when the specimen yields; and lower yield point (_sl): minimum stress in the yield stage when the initial instantaneous stress is not taken into account.

冷拔无缝钢管屈服点的计算公式为：

The formula for calculating the yield point of cold-drawn seamless steel tube is as follows:

式中：Fs--试样拉伸过程中屈服力（恒定），N（牛顿）So--试样原始横截面积，mm2。

In the formula: Fs - the yield force (constant) during the tensile process of the specimen, N (Newton) So - the original cross-sectional area of the specimen, mm2.

冷拔无缝钢管断后伸长率（σ）

Elongation of cold-drawn seamless steel tube after fracture (_)

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%。计算公式为：

In the tensile test, the percentage of the length of the standard distance increased by the specimen after breaking to that of the original standard distance is called elongation. In_, the unit is. The calculation formula is as follows:

式中：L1--试样拉断后的标距长度，mm； L0--试样原始标距长度，mm。

In the formula: L1 - the length of standard distance after specimen breaking, mm; L0 - the original length of standard distance of specimen, mm.

冷拔无缝钢管断面收缩率（ψ）

Section shrinkage of cold-drawn seamless steel tube (_)

在拉伸试验中，试样拉断后其缩径处横截面积的最大缩减量与原始横截面积的百分比，称为断面收缩率。以ψ表示，单位为%。

In tensile test, the percentage of the maximum reduction of cross-sectional area at the shrinkage of specimen after breaking to the original cross-sectional area is called the cross-sectional shrinkage rate. In_, the unit is.

式中：S0--试样原始横截面积，mm2； S1--试样拉断后缩径处的最少横截面积，mm2。

Formula: S0 - the original cross-sectional area of the specimen, mm2; S1 - the minimum cross-sectional area at the shrinkage point of the specimen after breaking, mm2.