Measuring method of straightness of seamless steel pipe

SMLS pipe, longitudinally welded steel pipes (LSAW pipe), forged steel pipes, precision dense steel pipes, high-precision precision steel pipes, and other steel pipes will cause the steel pipe body to bend to varying degrees in the longitudinal direction (that is, the length direction) during the production process. However, the degree of bending of some steel pipe products is visible to the naked eye, and the steel pipe is not a qualified product. As long as it is a regular manufacturer, such products are absolutely not allowed to leave the factory, and some require special equipment to measure straightness.

For the straightness of steel pipes, the requirements are not high in general fluid transportation pipelines. This kind of pipe mainly requires the concentricity of the nozzles to facilitate the welding of the pipeline. However, if steel pipes are used in processing machinery and equipment, especially rubber rollers, middle shafts, etc., they have higher requirements for straightness or curvature, and this is also a very important index for them. Because it involves a processing problem, the amount of processing directly affects the size of the production cost. If it cannot be processed, the steel pipe will be a waste product. Therefore, manufacturers like the production of roller body equipment pay special attention to the straightness of the steel pipe when they buy seamless steel pipes or straight seam steel pipes.

For seamless steel pipes, straight seam steel pipes, and forged steel pipes, the straightness is best to be forged steel pipes. Because the outer diameter is produced by the processing equipment bit by bit, the straightness is generally not a problem. Secondly, seamless steel pipes have a three-roll straightening process in the production process of this steel pipe. The pipes with high straightness requirements use a computer-controlled multi-function integrated hydraulic straightening machine imported from South Korea, which can basically meet the straightness requirements of customers. The worst is the straight steel pipe. Although the basic process also has this process, it is made of steel plate or coil. If the internal stress of the steel cannot be released well, it will also cause the deformation of the steel pipe after processing. .

Generally speaking, there are two kinds of calculation of straightness or curvature:

1. Partial curvature of seamless steel pipe or straight seam steel pipe: Use a one-meter ruler to measure the maximum bend of the steel pipe and measure the chord height (mm), which is the value of local curvature, and its unit is mm/m, means such as 2.5mm/m. This method is also suitable for tube end curvature.

2.The total bending degree of the steel tube: use a thin rope to pull tight from both ends of the tube, measure the maximum chord height (mm) at the bend of the steel tube, and then convert it into a percentage of the length (in meters), which is the length of the steel tube The full-length curvature of the direction. For example: the length of the steel pipe is 10m, and the measured maximum chord height is 30mm, the total length of the pipe is: 0.03+10m*100%=0.3%.