Disadvantages of high frequency electric resistance welding pipe(erw steel pipe) forming roller is following below:
1. Weakening crude molding deformation is the root of the pipe defects. Since the one-sided pursuit of the common roll to reduce the number of roll and roll changing times, thus reducing the horizontal row roll forming roll stand (breakdown stand), so that the original level by the amount of deformation of the deformation roll stand, more transferred to the discharge roller section and precision molding machine. Row roller segment consists of many efflux roll and some of the inner roller composed mainly efflux roll by applying pressure to the outer surface of the steel strip to deform the inner surface of the roll so that deformation of the inner strip.
2. The crude molding deformation is not sufficient, increase the precision molding machine, a number of mill. In the high-frequency welded pipe production, the effects of the deformed state edge of the strip on the welding quality greatly. The best steel tube curvature of the opening edge portion of the pipe and finished very close, and this deformation required to complete the rough shaping stage. The row roll forming technology since the horizontal roll stand reduction in crude forming stage is difficult to do, had to be deformed into the discharge roller segment and fine machine, but in the row roll segment, due to the structure of the device is also very difficult to guarantee, the result is the roundness of welded pipe difference after.
3. Pipe intrinsic product quality. Since the outer and inner roll cage roll steel strip uneven deformation, so that the degree of partial pipe material hardening increases, the residual stress is large and unevenly distributed. Although the dimensions of products can meet the requirements, but the relative performance of the material steel base material has changed greatly, pipe internal toughness, extensibility, resistance to stress corrosion and so has been compromised, which is used in cold regions casing great influence of high grade steel pipeline corrosion and requires media.
4. The lack of thrust, unstable welding speed. In ERW molding process, totally dependent on the drive roller thrust provided by the steel strip to overcome the deformation resistance and stable welding speed. Since the horizontal rack reduced, so that the deformation of the thrust to overcome, particularly in areas large strip thickness, high strength material, the phenomenon is prone to insufficient thrust of the strip forming velocity fluctuations. In order to compensate for the lack of thrust, stable welding speed is also required to increase the number of precision molding machine.
5. Equipment poor rigidity, and high strength thick-walled pipe production difficult. Early compared with the current row roll forming machine is used in many interior rollers, but after the increase in the number of rollers also have some problems.
