What is the basic production process of hot-rolled seamless pipe?
The production process of hot-rolled seamless pipe mainly includes steps such as billet heating, perforation, rolling, sizing, cooling, straightening, flaw detection, cutting and inspection. The billet is first heated to about 1200°C, then pierced into a hollow rough tube by a perforator, and then rolled into the required size by a continuous rolling mill. The sizing process ensures that the outer diameter and wall thickness of the steel pipe meet the standard requirements, while straightening is used to eliminate the bending deformation caused by the rolling process. Finally, the steel pipe needs to undergo non-destructive testing (such as ultrasonic flaw detection) and mechanical property testing to ensure product quality.
What are the common methods of perforation process?
The perforation process of hot-rolled seamless pipe mainly includes two methods: oblique rolling perforation and pressure perforation. Oblique rolling perforation (such as Mannesmann perforator) is suitable for small and medium-sized diameter steel pipes, with the advantages of high production efficiency and low cost; pressure perforation is suitable for large diameter thick-walled pipes, but the equipment investment is large. The choice of perforation process directly affects the wall thickness uniformity and internal quality of the steel pipe, so it needs to be optimized according to product specifications and production requirements. In addition, modern perforation technology has also introduced improved methods such as tapered roller perforation and mushroom perforation to improve production efficiency and yield rate.
Why do hot-rolled seamless pipes need to be sized and straightened?
The sizing process is to ensure that the outer diameter and wall thickness of the steel pipe meet the standard requirements, and a tension reducer or sizing machine is usually used for finishing. Straightening is to eliminate the bending deformation of the steel pipe during rolling and cooling, so that it meets the specified straightness requirements. These two processes are crucial to the dimensional accuracy and performance of the steel pipe, especially for mechanical structure pipes with high precision requirements. If the sizing or straightening is not in place, it may cause difficulties in installing the steel pipe or reduce the bearing capacity.
What are the heat treatment processes for hot-rolled seamless pipes?
Common heat treatment processes for hot-rolled seamless pipes include normalizing, tempering, quenching + tempering (quenching and tempering treatment), etc. Normalizing can refine the grains and improve the uniformity and mechanical properties of the steel pipe; tempering is used to eliminate residual stress and improve toughness; quenching and tempering (quenching + high temperature tempering) can significantly improve the strength and fatigue resistance of the steel pipe. For example, oil casing is usually quenched and tempered to meet the requirements of high strength and toughness. The selection of heat treatment process needs to be optimized according to the material and use environment of the steel pipe.
How to detect the quality of hot-rolled seamless pipes?
The quality inspection of hot-rolled seamless pipes includes chemical composition analysis, mechanical property testing (such as tensile testing, impact testing), non-destructive testing (such as ultrasonic flaw detection, eddy current flaw detection) and water pressure testing. Chemical composition analysis ensures that the material meets the standard requirements, and mechanical property testing verifies the strength, plasticity and toughness of the steel pipe. Non-destructive testing is used to find surface and internal defects (such as cracks, inclusions), while water pressure testing simulates actual working pressure to test the pressure bearing capacity of the steel pipe. These testing methods jointly ensure the safety and reliability of the steel pipe.
