Steel pipe is a kind of steel with hollow section, whose length is much larger than diameter or circumference. Steel pipes are widely used in transportation pipelines, engineering structures, thermal equipment, petrochemical industry, machinery manufacturing, geological drilling, high-pressure equipment and so on. The quality of steel pipe is very important. 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 impurities on the surface of rolled parts, etc.
Temperature is the most important factor affecting the quality of steel pipe. Firstly, the uniformity of billet heating temperature directly affects the uniformity of wall thickness and inner surface quality of perforated capillaries, and then affects the wall thickness quality of products. Secondly, the temperature and uniformity (especially the final rolling temperature) of steel pipe during rolling are related to the mechanical properties, dimension accuracy and surface quality of products delivered in hot rolling state, especially when the billet or billet is overheated or even burnt, it will cause waste products. Therefore, in the production process of hot-rolled seamless pipe, heating and controlling the deformation temperature strictly according to the process requirements are the first work to be done.
(2) Process adjustment
Process adjustment and working quality mainly affect the geometry and appearance quality of steel pipe. For example, the adjustment of piercing mill and pipe rolling mill affects the accuracy of product wall thickness, and the adjustment of sizing mill 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 quality of the tool is good or not is directly related to the effective control of product size accuracy, surface quality and tool consumption. The quality status of mandrel surface treatment (chromium plating) affects the inner surface of steel pipe and the mandrel consumption and production cost.
(4) Process cooling and lubrication
The cooling quality of piercing plug and roll not only affects their service life, but also affects the quality control of the inner and outer surface of the product. The cooling and lubrication quality of mandrel first affect the inner surface quality, wall thickness accuracy and mandrel consumption of steel pipe, and also affect the rolling load.
(5) Clearance and Control of Surface Miscellaneous Matter on Rolled Parts
This refers to the timely and effective removal of iron oxide scales on the inner and outer surfaces of capillaries and barren tubes and the control of re-oxidation before rolling deformation. High-pressure water descaling at the entrance of rolling pipe and fixed diameter can effectively improve and improve the quality of inner and outer surface of capillary hole treated by nitrogen blowing and borax spraying.
In a word, there are many factors affecting the quality of steel pipe, and they are often a combination of various factors. Therefore, it is necessary to effectively control the above main factors. Only in this way can we control the quality of steel pipe and produce hot-rolled seamless steel pipe with high dimensional accuracy, good performance and quality.