Medium-diameter 9ni low-temperature seamless steel pipe and production method

Abstract

The invention relates to a medium-caliber 9Ni low-temperature seamless steel tube and a production method. The seamless steel tube comprises, by mass, less than or equal to 0.06% of C, 0.13%-0.28% of Si, 0.40%-0.70% of Mn, less than or equal to 0.010% of P, less than or equal to 0.003% of S, 8.7%-9.30% of Ni, 0.03%-0.07% of Mo, 0.01%-0.040% of Al and the balanced Fe and inevitable impurities. The seamless steel tube is produced through an MPM retained mandrel tandem rolling process. The production method includes the steps of tube blank inspection, tube blank discharging, circular furnace heating, tapered roller puncher punching, borax blowing, tube rolling through an MPM retained mandrel tandem rolling machine, working of an extracting mill, reheating through a stepping furnace, high pressure water descaling, diameter determining, cooling through a cooling bed, saw cutting through a pipe saw mill, straightening, leakage flux flaw detection, manual inspection and coping, heat processing, straightening, coping processing on the inner surface and the outer surface of a steel tube, ultrasonic flaw detection, manual reinspection, cleaning, identifying, packaging and storage.

Description

technical field [0001] The invention relates to the field of seamless steel pipe production in the metallurgical industry, in particular to a medium-diameter 9Ni low-temperature seamless steel pipe produced by using the MPM limiting mandrel continuous rolling process. Background technique [0002] 9Ni low-temperature steel is widely used in the storage and transportation of liquefied natural gas due to its excellent mechanical properties and good low-temperature toughness. This grade of seamless steel pipe is used in a low temperature environment with a design temperature of -158~-162°C and a working pressure of 0.5~29N / mm 2 Under the pressure, its working state is high pressure and low temperature, its surface bears compressive stress in its working environment, and huge thermal stress is generated on the inner and outer surfaces. Therefore, the requirements for the performance of 9Ni are very high, and the steel grade of this grade is required to have both good mechanical...

AI Technical Summary

Problems solved by technology

At present, most of the medium-caliber 9Ni low-temperature steel pipes used are welded pipes, which are welded with plates. The production of 9Ni low-temperature steel pipes by welding technology requires very high welding technology, and the corresponding production costs are also high.

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