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

Abstract

A 9Ni low temperature seamless steel pipe with large aperture and a production method thereof. The seamless steel pipe comprises the components of no more than 0.10 wt.% of C, 0.20-0.32 wt.% of Si, 0.60-0.90 wt.% of Mn, no more than 0.010 wt.% of P, no more than 0.003 wt.% of S, 9.00-9.50 wt.% of Ni, 0.06-0.09 wt.% of Mo, 0.030-0.060 wt.% of Al and the balance of Fe and unavoidable impurities. The seamless steel pipe is produced by a Pilger period rolling process, which includes pipe blanking, punching on pipe blank, annular furnace heating, punching by Mannesmann puncher, pipe rolling by a Pilger rolling mill, Pilger head cutting, heating in a stepping furnace, sizing by a sizing machine, heat treatment, straightening, inside and outside surface treatment, artificial inspection, ultrasonic eddy automatic current combination flaw detection, artificial recheck, cleaning, identifying, packaging and warehousing.

Description

technical field [0001] The invention relates to the technical field of production of seamless steel pipes in the metallurgical industry, in particular to the production of large-diameter 9Ni low-temperature seamless steel pipes by using a pilger 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 prope...

AI Technical Summary

Problems solved by technology

At present, most of the large-diameter 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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