Defining of end crops of pipes produced at pipe rolling plant with continuous PQF, FQM mills

The theoretical study of the formation of the end crops during rolling at a tube rolling plant with continuous mills was made. It is found that the majority of available formulas are adapted to calculate the end crops for rough pipe rolling at a tube rolling plant with two roll continuous mills having a retained or floating mandrel. It is determined that the main technological factors affecting the formation of end crops during the hot process stage are the hydrothinning system of continuous mill, the coefficient of elongation of the hot process stage, the ratio of the outside diameter to the wall thickness of the rolling product (D / S), tonnage, the usage of different caliber systems of the PQF mill. The analysis of the wall thickness measurements at the extractor mill showed that the pipe hydrothinning system adjusts the wall thickness across the body of the rolling product, but the absolute value of the wall thickness variation on the rear end is considerably higher than the wall thickness variation on the front one. Based on the data analysis the power dependence of the end crops on the dimensionless coefficient including the coef¬ficient of drawing, the outer diameters of the pipes after continuous, calibrating and reduction-recliner mills were obtained. With this dependence it is possible to regulate the amount of the end crops by using 190 mm and 290 mm caliber of the PQF mill. The formula obtained has a good agreement with practice and follows recommendations given in literature.