Numerical Study of the Process of Hot Helical Rolling of Hollow Billets with a Small-Diameter Bottom
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NUMERICAL STUDY OF THE PROCESS OF HOT HELICAL ROLLING OF HOLLOW BILLETS WITH A SMALL-DIAMETER BOTTOM V. V. Kulteshova,1 A. V. Ivanov,2 and I. V. Zavora3
UDC 621.771.2
The paper presents the results of numerical simulation and experimental studies of the process of helical rolling of billets having a small-diameter bottom. An improved technology for producing smalldiameter billets without the need for subsequent machining of the inner surface is proposed. Pilot-scale piercing and calibration of the billets was performed using an automated helical rolling line. Keywords: helical rolling, multi-pass cold stamping, machining, numerical simulation.
Currently, billets having a small-diameter bottom are manufactured by one of the following methods: multipass cold stamping of calibrated low-carbon steel by using a pressing equipment, machining of calibrated coldworked medium-carbon steel, or helical rolling of hot-rolled medium-carbon steel. The technological process of cold stamping is a multi-step process involving intermediate chemical and heat treatment operations. The disadvantages of this method include high labor intensity and high manufacturing cost of the parts due to a large number of pressing, thermal, chemical, transport, control, and other intermediate operations; high energy consumption; and extended floor space required for organizing the technological process. The machining process is realized by turning the outer surface, drilling, and boring the inner surface using semi-automatic and automatic metal lathes. The disadvantages of the machining method include a low metal utilization factor, as well as high cost of the starting material, tools and equipment. The helical rolling technology is implemented using an automated helical rolling line and includes the following operations: cutting rods into workpieces (billets), heating the latter in an induction installation, piercing the billets on a helical rolling mill, calibrating on an in-line mechanical press, cooling and control. A general view of the hollow billets having a small-diameter bottom is shown in Fig. 1 [1–5]. Due to the process automation, helical rolling is the most efficient method for manufacturing small-diameter billets (25 to 60 mm). The significant advantages of the technology include the following: ability to manufacture billets using medium- and high-carbon alloyed steels compared to cold stamping; high metal utilization factor; low labor intensity of the manufacturing process compared to machining. The main disadvantage of this technology is the need for machining the inner surface of the hollow billets, which requires special equipment and cutting tools. To solve this problem, a technology of helical rolling of billets having a small-diameter bottom was developed, which provided a minimum machining tolerance without the need for subsequent machining of the inner surface [6]. According to the existing technology, a piercing mandrel with a small lead-in section is located 1
Bauman Moscow State Technical University (BMSTU), Moscow, Russia
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