production mainly through the following processes; tube – cutting – heating – perforation – rolling pipe – set (minus) diameter – straightening – cut the first tail – testing – packaging – storage. According to different ways of rolling, seamless steel tube rolling mills can be divided into automatic tube rolling unit, continuous tube rolling unit (MPM two-roll continuous tube rolling unit, PQF three-roll continuous rolling tube unit), assel roll unit, the periodic tube rolling unit, the new rolling mill to MPM pipe rolling unit, PQF three roller pipe mill units are mostly.
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Tube perforation is the most important deformation process in the production of seamless hot rolled steel tube. Its task is to pierce the solid tube into a hollow capillary tube. According to the structure of the piercer and the deformation characteristics of the piercing process, while the piercing is the most widely used. The shape of the piercing piercer roll roller, bacteria (cone) and disc three, roller piercing mill roll used in small mills, and large unit perforated machine with bacteria roll. Disc punch machine less application. Regardless of roll shape, in order to ensure the billet billet and perforation process to achieve perforation cone (roll entrance cone), mill cone (roll exit cone) and the roll rolling strip (inlet cone and outlet cone between the excessive part )composition.
Punch roller roll roller is mostly used in the combination of the structure, the two use direct interference combination or keyed interference combination. In this way, when the roller scrapped, the roller shaft can continue to reuse, in order to reduce the cost of the tool. Small piercing machine roller material selection of 45 or 40Cr, quenched and tempered. Large piercing machine roller 42CrMo, quenching and tempering. Roll material At present, the manufacturers choose more miscellaneous, and some manufacturers choose forged 45,55 quality carbon structural steel. Some manufacturers choose 50Mn, 65Mn, 70Mn, 70Mn2Mo, 60CrMnMo other alloy steel or forged steel; hardness range requirements are inconsistent, and some require HB180-220, and some require HB220-260. In order to increase the biting nature, large perforated roll generally processed in the inlet cone depth of 0.8 ~ 1.2mm mesh pattern.
Comprehensive domestic and foreign manufacturers of material selection and use of the situation, the author believes that: the choice of piercing machine roll casting 50Mn, 60CrMnMo medium carbon steel is more appropriate, first, has good strength and wear resistance, the second is suitable for rolling material steel pipe. Hardness control in the HB200-240 more reasonable.