Limiting mandrel for mandrel pipe mill and manufacturing method thereof

Abstract

The invention discloses a limiting mandrel for a mandrel pipe mill, and the limiting mandrel comprises a milling operating section and a tail section in threaded connection with the milling operating section. The milling operating section comprises a cylindrical substrate, an overlay welding layer fixedly bonded on the outer wall surface of the cylindrical substrate, and a chromium plated layer positioned on the surface of the overlay welding layer, wherein the cylindrical substrate is made of low alloy steel; the overlay welding layer comprises the following components by weight percent: 0.30-0.45% of C, 0.7-1.2% of Si, less than or equal to 0.60% of Mn, 4.5-5.5% of Cr, 0.8-1.2% of V, 1.0-1.75% of Mo, less than or equal to 0.25% of Ni, less than or equal to 0.03% of P, less than or equal to 0.03% of S, and the balance of Fe. The manufacturing method of the limiting mandrel comprises the following steps: fabricating the cylindrical substrate; and carrying out overlay welding, carrying out hot straightening, carrying out rough machining, carrying out finish machining, polishing, carrying out chromium plating, dehydrogenating, and carrying out thread phosphorizing. The limiting mandrel provided by the invention has the advantages of light weight, high strength, long service life and low production cost, is convenient to repair and regenerate, and is suitable for being generalized and used in the metallurgical industry.

Description

technical field [0001] The invention relates to a rolling tool used in a continuous rolling mill for seamless steel pipes, in particular to a stop mandrel used in a continuous rolling mill; the invention also relates to a manufacturing method for the stop mandrel, which belongs to the metallurgical Industry rolling tool manufacturing technology field. Background technique [0002] The stop mandrel is an important rolling tool used in the continuous rolling mill for the production of seamless steel pipes. During the rolling process, the mandrel not only needs to withstand large rolling force and friction, but also needs to withstand frequent cold and heat shocks. Therefore, the mandrel material must not only have sufficient strength and toughness, but also need strong cold resistance. For thermal fatigue performance, the expensive H13 steel is usually used as the mandrel material at home and abroad. [0003] During the seamless steel pipe rolling process, due to the self-we...

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Problems solved by technology

[0003] During the seamless steel pipe rolling process, due to the self-weight of the mandrel, the mandrel tends to move downward during the entire rolling process, which leads to uneven wall thickness of the rolled steel pipe, which affects the quality of the finished steel pipe. Due to the self-weight of the mandrel, the wear of the roll is uneven, especially for the large-scale stop mandrel, because of its large weight, the impact on the unevenness of the steel pipe wall thickness rolling, the structure inside the rolling mill, and the life of the roll is more obvious.

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