The seamless pipe is made of a steel ingot or a solid tube blank through perforation into a capillary tube, and then hot rolled, cold rolled or cold drawn. The seamless pipe has a hollow cross-section and is widely used as a pipeline for conveying fluids, such as octg pipes for conveying oil, natural gas, gas, water, and pipes for certain solid materials. It occupies an important position in my country's steel pipe industry. So what should be paid attention to when producing seamless pipes?
1) Pay attention to whether the thickness of the embryonic tube wall is uniform. If it is found that the wall thickness of the embryonic tube is uneven, the surface polishing treatment must be done. In addition, pay attention to whether the inside and outside of the embryonic tube are smooth and whether there are any unevenness and defects. Once the unevenness or defects are found, they must be dealt with in time.
2) Re-examination of the embryonic tube. The main task of the re-inspection is to ensure that there are no cracks and defects on the outside of the capillary, check these problems existing in the capillary and make corresponding troubleshooting measures, and the phenomenon of pitting and folding in the capillary must be removed.
3) Requirements for tools. Generally, the tools used in cold drawing have relatively high requirements on surface finish. Only when the surface finish of the tool is high, can the finish of the steel pipe drawn from cold drawing be high; in addition, the dimensional accuracy and hardness requirements of the mold are also relatively high. Therefore, it is also very important for us to choose a good abrasive tool in the production, and the phenomenon that the abrasive tool sticks to steel must not appear.
4) Annealing. Annealing is a very important process in the production of all seamless pipes. The quality of annealing affects both the performance of the steel pipe and the removal of scale on the surface of the steel pipe.
5) Pickling. Seamless pipes are prone to form "black slag" mainly composed of fe2o3 and fe3o4 during sulfuric acid pickling, and black spots on the surface are easy to form in subsequent production. Fe2o3 and fe3o4 are easily soluble in hydrochloric acid. To prevent the formation of black spots, add 5-10g/l nacl to the acid pool.
6) Lubrication. Use resin as lubricant as much as possible. This kind of lubrication is obviously different from phosphating plus lubrication (saponification). The drawn seamless pipe presents the true color of the iron matrix, which not only has the beautiful appearance and luster of cold-rolled pipes but also has high smoothness. The industrial control of seamless pipe production includes mold design, pickling, lubrication, annealing and other condition control. At the same time, work should be done on the quality inspection and repair of rough hot-rolled pipes.
The production process of seamless tubes can be divided into two types: cold drawing and hot rolling. The hot rolled seamless tubes are delivered in the hot rolled state or the heat treatment state, and the cold drawn seamless tubing is delivered in the heat treatment state. Due to the small width-to-thickness ratio of the steel plate, the precision requirements for the size of the hot-rolled steel pipe are relatively low, and the plate shape problem is not easy to occur.