冷拔钢管不均主要体现为螺旋状壁不均、直线状壁厚不均及头尾部壁厚偏厚、偏薄等现象一、螺旋状冷拔钢管不均的成因是穿孔机轧制中心线不正、两轧辊的倾角不等或顶头前压下量太小等调整原因造成的壁厚不均，一般沿冷拔无缝钢管的全长呈螺旋状分布。主要措施是调整穿孔机轧制中心线，使两轧辊的倾角相等，按轧制表给定参数调整轧管机。
The uneven wall thickness of cold-drawn steel tube is mainly manifested in the uneven spiral wall, linear wall thickness and the thicker and thinner wall thickness at the head and tail. The uneven wall thickness is caused by the improper rolling center line of piercing mill, unequal inclination angle of two rollers or too small reduction in front of the top. Generally, the uneven wall thickness is spiral distribution along the full length of cold-drawn seamless steel tube. The main measures are to adjust the center line of the piercing mill so as to make the inclination of the two rolls equal and to adjust the mill according to the given parameters of the rolling table. 二、直线状壁厚不均的原因是芯棒预穿鞍座高度调整不合适，芯棒预穿时接触到某一面的毛管，致使毛管在接触面上温降过快，造成壁厚不均甚至拉凹缺陷。连轧轧辊间隙过小或过大。 轧管机中心线偏差。单、双机架压下量不均，会造成钢管单机架方向超薄(超厚)、双机架方向超厚(超薄)的直线型对称偏差。主要措施是调整好芯棒预穿鞍座的高度、保证芯棒与毛管对中。更换孔型及轧制规格时应测量轧辊间隙，使实际轧辊间隙与轧制表保持一致。用光学对中装置调整轧制中心线，年度大修时必须校正轧管机中心线。
2. The reason of non-uniform linear wall thickness is that the height adjustment of mandrel pre-piercing saddle is inappropriate. When mandrel is pre-piercing, it contacts the capillary on one side, which causes the temperature drop of capillary on the contact surface to be too fast, resulting in uneven wall thickness and even drawdown defects. The gap between rolls in continuous rolling is too small or too large. Center line deviation of pipe mill. The uneven reduction of single and double racks will result in the linear symmetry deviation of ultra-thin (ultra-thick) steel tube in the direction of single rack and ultra-thick (ultra-thin) steel tube in the direction of double racks. The main measures are to adjust the height of the mandrel pre-piercing saddle and ensure the mandrel and capillary alignment. Roll clearance should be measured when changing pass and rolling specification, so that the actual roll clearance is consistent with the rolling table. The center line of rolling mill must be adjusted by optical alignment device during annual overhaul.
Cold drawn steel tube
三头、尾部壁厚不均的原因是管坯前端切斜度、弯曲度过大、管坯定心孔不正易造成钢管头部壁厚不均。穿孔时延伸系数太大、轧辊转速太高、轧制不稳定。穿孔机抛钢不稳定易造成毛管尾部壁厚不均。措施是检查管坯质量，防止管坯前端切斜度、压下量大，更换孔型或检修均应校正定心孔。采用较低的穿孔速度，以确保轧制的稳定性和毛管壁厚的均匀度。当轧辊转速调整后，匹配的导盘也做相应调整。
The uneven wall thickness at the three ends and the tail end is due to the uneven wall thickness at the head of the tube due to the excessive tangential inclination of the front end of the billet, the excessive bending and the improper centering hole of the billet. When piercing, the elongation coefficient is too large, the speed of roll is too high, and the rolling is unstable. Instability of cast steel in piercing machine can easily cause uneven wall thickness at the tail of capillary. The measure is to check the quality of the billet, prevent the front end of the billet from cutting slope and large reduction, and correct the centering hole for changing the pass or overhauling. Lower piercing speed is adopted to ensure rolling stability and uniformity of capillary wall thickness. When the roll speed is adjusted, the matching guide is adjusted accordingly.