What are key points of manufacturing thin-walled seamless steel tube for gas cylinder ?
The seamless steel tube used for gas cylinder is mainly thin-walled tube. The gas cylinder, using the seamless steel tube as the base material, is widely used for gas storage, industrial energy storage device, in fire fighting, hospital, oilfield and other fields. The gas cylinder is a pressure vessel, which has strict requirements on the quality and geometric size of the internal and external surface of the base material. Visible cracks, scars, folds, pinholes, slag, inclusions, and cracks, etc. on seamless steel tube are unacceptable. The base material must have stable geometry and chemical composition, good solidification structure, on which there must be no defects such as white spot, shrinkage cavity, stratification, crack, bubble, inclusion, flip, subcutaneous bubble, etc.
Because of the difficulty of deformation and the high quality requirement on inner and outer surface in the process of hot rolling, it must use the highest steel grade and the most difficult technique. Among them, 35CrMo, 37Mn, and 34CrMo4 steel tube are low carbon, low alloy austenitic steel with excellent comprehensive mechanical properties and higher rolling process requirements.
The traditional production process of gas cylinders is mainly made of billet. Billet first is heated and then punched and drawn to make gas cylinder. However, the yield of gas cylinders using this method is low, in order to solve this problem, people recently developed the technology of thin-walled seamless tube in manufacturing high-pressure gas cylinder tube, with the help of the key technology of bottom closing of gas cylinder made of seamless tube. It is convenient for the application of the key technology, which makes the manufacture of gas cylinder tube change from using steel billet through punching and drawing to using thin-walled seamless steel tube, and it has become the development trend.
Steel tube for High-pressure gas cylinder has many applications in our life. As a kind of innovation, it breaks the shackle of traditional manufacturing of gas cylinder and has its own unique advantages.
The internal and external surface quality of seamless steel tube for high-pressure gas cylinder is very good, and its whole wall thickness is quite uniform. Because of its light weight, high productivity, material rate and low cost, it is welcomed by the majority of users.
In order to improve the overall transport capacity of seamless steel tube for high-pressure gas cylinder, people put forward strict requirements on the steel tube rolling process. If you want to improve the quality of high-pressure gas cylinder, the key is to reduce the ratio of volume to weight. Therefore, we need to improve the ratio of diameter to wall thickness as much as possible on the premise of ensuring the excellent quality of the steel tube used to manufacture gas cylinders.
At the same time, the ratio of diameter to wall thickness is required to reach about 40. However, as far as the rolling technology of high-pressure gas cylinders is concerned, it is very difficult to improve the ratio of diameter to wall thickness, and wall thickness process technology. This is mainly because the wall is thin, the deformation of continuous rolling mill unit is large, the overall coefficient of elongation between 4.0 and 5.0. In addition, it is difficult for us to control the accuracy of wall thickness, because under normal circumstances, temperature fluctuation, adjustment, rack spring and other factors of steel tube will affect its wall thickness.
Seamless steel tube manufactured by Baotou Steel ( a state-owned company of steel products ) in Inner Mongolia provide high quality base material for the manufacturing of tube-made gas cylinder. It has the advantages of good internal and external surface quality, uniform wall thickness, light weight, high productivity and finished product rate, low cost and so on, regarded as one of the hero products in China. As a leading manufacturer of steel products, Baotou Steel have exported seamless steel pipe, coating pipe, casing and tubing pipe, steel rails and so on throughout the world. API, ISO, TUV, ABS, CCS, etc certificated qualification and extreme standard keep Baotou Steel very competitive in current market.