Seamless steel pipes with smaller diameters can be called small-diameter seamless steel pipes. Small-diameter seamless steel pipes can be divided into seamless small-diameter steel pipes and straight seam (also known as welded) small-diameter steel pipes. Generally, seamless steel pipes with diameters between 4mm and 89mm are collectively referred to as small-diameter seamless steel pipes.
Large-diameter seamless steel pipes refer to seamless steel pipes with a diameter greater than 325mm. Large-diameter seamless steel pipes can be divided into hot-rolled large-diameter seamless steel pipes and hot-expanded diameter seamless steel pipes. Hot-expanded diameter seamless steel pipes are not limited to national standard sizes. Hot-expanded seamless steel pipes usually have a lower density but a larger shrinkage. Hot-expanded seamless steel pipes are expanded using finishing processes such as rolling and drawing, which can thicken the pipe wall in a shorter time, and can produce special types of seamless pipes at low cost and high efficiency.
Seamless pipes can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes and extruded pipes according to different production methods. Generally speaking, hot-rolled seamless pipes are usually produced by automatic pipe rolling machines, and their production process includes the following steps: inspect the solid blank, repair surface defects and cut the solid blank into the required length; determine the center of the perforated end face of the blank and send it into the heating furnace for heating; punch holes in the blank through the punching machine, and the blank continues to rotate and move forward during the punching process; under the action of rolling, a cavity is gradually formed inside the blank, so that the blank gradually becomes a hollow blank; send the hollow blank to the automatic pipe rolling machine for further rolling; send the hollow blank to the pipe coiling machine to coil the wall thickness of the hollow blank, and then send it to the sizing machine for sizing to meet the specification requirements. Continuous rolling process is an advanced method for producing hot-rolled seamless steel pipes. If you want to produce seamless pipes with smaller diameters and better quality, you should use cold rolling process, cold drawing process or a combination of cold drawing process.
