Thermal expansion steel pipe means that the density is relatively low, but a strong contraction of the steel pipe, (seamless steel pipe) can be referred to as thermal expansion. Expanded by cross rolling method or methods of pipe diameters drawing a blank pipe finishing processes. In a short period of time for the steel thickening to produce non-standard and special types of seamless pipe, and low cost, high production efficiency, the development trend of international rolling fields today.
Thermal expansion steel pipe production process: hollow base material without continuous rolling mandrel. In ensuring the quality of the premise of the mother pipe welding, pipe tension reducing the overall process is the pipe heated to 950 degrees celsius, and then stretch reducing mill (tension reducing Machine has 24 times) rolled into a variety of outside diameter and wall thickness of the finished pipe produced using this process with the ordinary thermal expansion of high-frequency welded steel pipes are essentially different, heated by the furnace microstructure and mechanical properties of the weld and the parent can reach exactly the same in addition, through a multi-passes stretch reducing mill makes steel rolling and automatic control of dimensional accuracy (especially the tube wall thickness and roundness accuracy) than similar seamless. Developed countries produced fluid pipe, boiler tube seamless pipe has been widely adopted technology. Two-step thermal expansion pipe used to promote the expansion of the machine set-type cone mold expanding technology, digital intermediate frequency induction heating technology, hydraulic technology in one machine, with its reasonable process, lower energy consumption, lower capital investment, good product quality, a wide range of raw materials and product specifications applicability, flexible variable low-input production batch adaptability replace the traditional steel industry pul dial expanding technology.
Thermal expansion process can be divided into five stages:
1 Preliminary stage of a full circle. Segments open until all segments are exposed to the pipe wall, then the step length range steel tube radius of each point are almost identical, steel preliminary full circle.
2 Nominal inside diameter stage. From the starting position preceding segments reduced velocity, until it reaches the desired position, this position is within the required quality of the finished pipe circumferential position.
3 Bombs complex compensation stage. Segments start at the position of the second stage further low speed, until reaching the required position, this position is within the elastic recovery process design requirements circumferential position of the front pipe.
4 Packing stable stage. Segments in the complex before the pipe bomb circumferential position for some time remain intact, which is a stable phase packing equipment and expanding process requirements.
5 Unloading regression phase. Segments circumferential position retracted from the bombs began to rapidly resume before the pipe, until the arrival of the initial expanding position, which is expanding the minimum technological requirements segments shrink