Study of the influence of the mode of rotation of pipe in the cold rolling process on the microstructure, mechanical properties and accuracy

Abstract

Goal. Obtaining experimental results on the influence of the turning mode during cold rolling on the microstructure, mechanical properties and accuracy of the geometry of the pipes to improve their quality. Method. Experiments were carried out on equipment used in production and having appropriate inspections. We used a grinding machine, a device for electrolytic etching, a MIM 7 microscope, and a press for stretching samples. The accuracy of the geometric dimensions was determined using tube micrometers. Rolling route 25×2.5 mm → 16×1.5 mm. Steel 08Х18Н10Т. The results. Two rotation modes were performed: mode 1 – feed 2, 3, 4, 5 mm in front of the straight one, and the rotation before the reverse movement of the cage; mode 2 – feed 2, 3, 4, 5 mm in front of the straight, and turn in front of the straight and reverse movement of the cage.For mode 2, in comparison with mode 1, the grain size near the inner surface of the pipes is visually smaller than near the outer surface.The strength limit, yield strength and relative elongation for modes 1 and 2 were found to be close in value.With regard to the accuracy of the geometry of the pipes, it was determined that in mode 2 compared to mode 1: – the transverse thickness of the pipes decreases by 1.4–1.6 times; – the ovality of the pipes is reduced by 1–2 times (feeds from 2 to 5 mm); – the spread of the diameter along the length of the pipe decreased almost twice. Scientific novelty. For the first time, new experimental industrial data on the influence of the rotation mode on the microstructure were obtained. It is shown that the grain size near the inner surface of the pipes is smaller than near the outer surface.For the first time, obtained experimental industrial data on the effect of the tube rotation mode on the values of strength limit, yield strength and ultimate elongation showed that the rotation mode did not affect their change.Additional experimental dependences on the influence of the pipe rotation mode on the transverse variation, ovality and spread of the outer diameter of the pipes during cold rolling of the pipes were obtained - the reduction of the transverse variation was 1.4–1.6 times, ovality 1–2 times, and the diameter variation was almost 2 times. Practical significance. The obtained results are needed in the development of technologies for the production of pipes with increased quality requirements (microstructure, heterogeneity, ovality, diameter dispersion).