TPT January 2021

AR T I C L E

Dalian Field

In order to produce small specifications, without decreasing the rigidity of the shaft, the machine adopts four-floating-stand technology. In the production of 100x100mm of steel pipe the wall thickness can also reach 10mm. The fourth generation CFS is also adjusted automatically and involved non-changing of the roll, with size changed in 10-20 minutes. Figure 4 shows CNC-CFS- IV 40x40mm-100x100mm pipe mill with wall thickness 1 to 4mm and built in 2018 years. Two- floating-stand technology not only maintains the high rigidity of the shafts, but also has the benefit of quick roll change. Figure 5 shows another automatic square-square pipe mill, CNC-CFS- IV 40x40mm-100x100mm pipe mill, wall thickness 4 to 12mm, built in 2020. The two-floating-stand technology not only can maintains the high rigidity of the shaft, but also has the function of quick roll change. Comparing figure 4 with 5, the sizes respectively are 100 x100x4mm and 200x200x12mm. The size difference is 100mm and thickness difference is 8mm, which seems to be not much different, but the structure size of the equipment is a particularly large difference. The effect of plate thickness on forming force is square of the ratio of 12mm divide by 4mm, which equals to 9 times. In addition, such as the ratio of side length divide by plate thickness, the ratio of angular radius divide by wall thickness,

the ratio of yield strength of materials, and so on, all have different effects on the force of the equipment, A summary of more than 20 years of CFS forming machine design and practical experience has been used to get the following empirical data (material steel grade up to S355, if more than this, below data will changes): B min≥(8-10) t max, B max≤(50-100) t min, maximum/minimum specifications ≤2.5-3, maximum/minimum wall thickness ≤(3-4), side length ratio of square pipe ≤(3-4); B (min) and B (max) are the minimum and maximum bottom length of the product, t (min) and t (max) are the minimum and maximum wall thickness of the product. The above data is for non-roll-change square-square pipe mills, but roll-change square-square pipe mills are not subject to this condition. Conclusion As mentioned in my previous paper, square and rectangular pipes under the square-square process will have lighter weight per meter compared with the round-square process, but have nothing to do with the ratio of the width of the steel strip between them. Strip width of round-square is wider than that of square- square and same length of strip will produce pipes longer than square-square made pipes. After offset with each other the other factor is incensement of pipe wall thickness. The significance of the square-square pipe mill is to shorten the time of changing specifications, to improve the stress distribution of products, and to produce high steel square and rectangular pipes – not for the saving of materials.

Figure 4

Figure 5

Dalian Field – China fd@fdmachinery.com www.fdmachinery.com

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JANUARY 2021