Seamless pipes with a diameter of 177.8mm to 426.0mm are manufactured using the Mannesmann plug mill process at medium diameter seamless pipe mill, JFE Steel Chita Works. The process flow of rolling is shown in Figure 1. The heating furnace heats round billets (pipe materials) that have a diameter of 175mm to 350mm to about 1250 degrees centigrade. The piercer is a two-roll mill with barrel-type rolls and pierces a hole in billets by pressing a plug against the center of them. The elongator is a same type of mill as the piercer and enlarges the diameter of the base pipes pierced at the piercer. The plug mill is a two-roll mill and reduces the thickness. The base pipes pass through plug mill two times with a 90-degree rotation and the thickness is reduced to the approximately final dimension. The reeler uniformizes the thickness and eliminates the inner streak. Temperature of the base pipes after the reeler is low. Therefore, the reheating furnace is used to heat up the base pipes to rolling temperature for sizing mill rolling. The sizing mill is a two-roll and eight-stand mill and conditions the diameter.
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