There are two kinds of factors affecting the quality of steel pipe: steel quality and rolling process.
The factors of rolling process are discussed here. The main influencing factors are: temperature, process adjustment, tool quality, process cooling and lubrication, removal and control of sundries on the surface of rolled piece, etc.
Temperature is the most important factor affecting the quality of steel pipe. First of all, the uniformity of heating temperature directly affects the wall thickness uniformity and inner surface quality of the perforated tube, and then affects the wall thickness quality of the product. Secondly, the temperature and uniformity (especially the finishing rolling temperature) of the steel tube during rolling are related to the mechanical properties, outer diameter and other dimensional accuracy and surface quality of the products delivered in the hot rolling state, especially when the billet or tube billet is overheated or even burnt, it will cause waste products. Therefore, in the production process of hot-rolled seamless pipe, it is necessary to heat and control the deformation temperature strictly according to the process requirements.
(2) Process adjustment
Process adjustment and working quality mainly affect the geometric and appearance quality of steel pipe.
For example, the adjustment of piercer and tube mill affects the accuracy of product wall thickness, and the adjustment of sizing machine is related to the accuracy and straightness of product outer diameter. Moreover, the process adjustment also affects the normal rolling process.
(3) Tool quality
Whether the tool quality is good or not, stability or not, is directly related to the realization of the effective control of the dimensional accuracy, surface quality and tool consumption of the product; the quality status of the mandrel surface treatment (chrome plating), on the one hand, affects the inner surface of the steel pipe, on the other hand, affects the mandrel consumption and production cost.
(4) Process cooling and lubrication
The cooling quality of piercing plug and roll not only affects its service life, but also affects the internal and external surface quality control of finished products. The cooling and lubricating quality of the mandrel firstly affects the inner surface quality, wall thickness accuracy and mandrel consumption of the steel pipe, and also affects the load during rolling.
(5) Removal and control of sundries on the surface of rolled piece
This refers to the timely and effective removal of the oxide scale on the inner and outer surfaces of the wool pipe and the waste pipe before rolling deformation and the control of reoxidation. The quality of inner and outer surface can be improved effectively by blowing nitrogen and spraying borax on the inner hole of capillary, descaling with high pressure water at the entrance of rolling pipe and constant (reducing) diameter.
In a word, there are many factors affecting the quality of steel pipe, and they are often the comprehensive effect of various factors. Therefore, it is necessary to effectively control the above main influencing factors. Only in this way can the quality of steel pipe be controlled and the hot-rolled seamless steel pipe with high dimensional accuracy, good performance and excellent quality can be produced.