The process of moulding strip
Roll forming in pipe welding mill
This process has much in common with the shaping process when the furnace welding. Nevertheless, the following significant differences. 1) If you expose the pipe to cold bending, it clearly expressed its elastic properties under load. 2) Workpiece subjected to molding have higher concoctent (d/s = 4 + 35 units furnace welding; 10 + 75 or more on TESA), which ultimately reduces their longitudinal resistance to bending action from the stands and increases the possibility of occurrence of corrugations at the edges, especially when indicators d/s > 50.
The conditions of molding
The number of stands, the distance between them, the angle of folding of the strip at each stand, in such mills should be based on two conditions: 1) the unhindered advancement of the strip through the mill. 2) the elimination of homeopathy. The first condition implies adherence to the prescribed process, the capture of metal rollers. In fact in mills of different sizes are used from 6 to 11 drive mills with horizontal rolls. Between the roller stands set transactions or other stand with vertical rolls besprovodnye (egernia crate).
The stages of forming
In horizontal mill stands there is a complete or major part of plastic and elastic deformation during molding. It was in the previous, non-contact area. Elastic recoil profile (reprezentowanie after deformation in a horizontal stand) in the main part should be carried out by means of vertical roll. It is also necessary that in the next crates created a new non-contact area of the elastic-plastic deformation (a new local hearth moulding), because after the passage of the vertical rolls is reprezentowanie. Of the bending strains and, in particular, non-monotonic edges occur, namely with the periodic increase, then a periodic reduction in the angle of folding, which is indicative of the separation of all lesion forming on local. In addition, due to this deformation increases the tensile edges and increases the probability of homeopathy. When forming thin-walled workpieces with d/s> 50 is very important to have a monotonous hearth which stands between the horizontal wiring are installed specially configured, having a short cylindrical rollers. The implementation of part bending deformation is possible in the roller Postings. The installation stands in which the lower (Central) forming a tube blank helps to reduce the process of homeopathy. The level of the bottom of the caliber of the lower horizontal rolls smoothly decreases during the molding process.
The calibration of rolls provides:
- versatility. Same rolls in the first stands can be used for forming tubular workpieces of different diameters. This in turn reduces the Park rolls;
- the resistance strips and the workpiece, it avoids their displacement along the axis of the roll;
- the implementation of the process of forming thin-walled workpieces.
- intensive forming mode (this mode reduces the number of working stands);
- lower wear of the rolls.
The above conditions is mostly not possible to realize in one calibration. In this regard, have been developed different types of calibration.
With this calibration the tubular billet in bend is one of radius R* in each pass, which gradually decreases during the molding process to the value of GP. This value is approximately equal to the radius of the already produced welded stainless pipe. One-tier calibration has received the greatest distribution in the aggregate perform the requirements of flexibility, regardless of other, relatively high rates
When this calibration profile is described by two different radii (the Central part — Rц; edge radius r, one of the radii is constant during the shape and is equal to GP, the second variable, which is gradually reduced), and others… roll Forming machines have different drive cages: group and individual.
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