| 摘要 |
PURPOSE:To eliminate the occurrence of the accident of the bend and breakage, etc. of a mandrel by upsetting with detecting the upsetting pressure and by stopping the pressure by the mandrel while the ascent of the detection pressure is stopped in case of producing a steel pipe from a bloom by Ehrhardt piercing method. CONSTITUTION:A heated bloom 1 is inputted into the container 2 having circular section and a upsetting plate 3 is placed thereon in case of producing a steel pipe by Ehrhardt method with the square billet of a bloom, etc. The bloom 1 is upsetted with pressure by the mandrel 5 fitted to the cross head 4 of a piercing machine via this upsetting plate 3. The upsetting is performed with detecting this upsetting pressure by pressure detector 7, the valve 8 for feeding pressure water 9 is closed while the ascent of the detecting pressure is virtually stopped, the feed of the pressure water 9 to a cylinder 6 is stopped and the band and breakage of the mandrel due to over-pressure are prevented.
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