An economical seamless steel pipe high piercing life plug and its manufacturing method

Abstract

An economical seamless steel pipe plug with high perforation life and its manufacturing method. The chemical composition of the plug is as follows: C: 0.15-0.25%; Si: 0.20-0.50%; Mn: 0.60-1.60%; Cr: 0.50- 1.00%; Ni: 2.80-3.20%; Mo: 0.20-0.40%; the rest are Fe and other unavoidable impurities. An oxide film grows on the surface of the plug, the thickness of the oxide film is 80-200 μm, and Ni-rich metal particles are dispersed in the oxide film. The oxide film and the substrate are interlaced in canine teeth, and the density of the canine teeth is higher than that of traditional plugs, which fully demonstrates the strong bonding force between the oxide film and the substrate. Therefore, the oxide film is not easy to fall off during the plug piercing process, greatly improving the life of the plug piercing.

Description

technical field [0001] The invention relates to an economical seamless steel pipe plug with high perforation life and a manufacturing method thereof. Background technique [0002] The plug is one of the important tools with large consumption in the production of seamless steel pipes. Its main function is to form a closed cavity with the perforated roller and the guide plate to realize the transformation from the solid tube blank to the hollow capillary tube. [0003] The plug bears great axial, tangential and radial forces and friction during the piercing process, and bears the high temperature caused by the tube blank and frictional heat (the temperature near the surface of the nose plug can reach about 1100-1200 ° C, and the piercing The temperature near the surface of the cone section plug is higher than the austenitization temperature), so it is very easy to damage the surface and fail during the piercing process. The main failure mode of the plug is the loss of meat in...

AI Technical Summary

Problems solved by technology

[0004] Chinese patent CN1112165A discloses a perforated plug material for steel pipes containing V. This patent refines the grains by adding V, forms carbides, and improves the high-temperature strength of the material. However, adding V will increase the cost, and although adding V will increase the strength, but at the same time It will also reduce the toughness and thus be detrimental to the heat and cold fatigue resistance of the plug matrix

In addition, although microalloying elements such as V and Nb can increase the strength, it is also easy to form different strength, plasticity and toughness in different places due to different temperature rises or cooling rates during the use of the plug, resulting in poor performance in various parts of the matrix. Uniformity, reducing the deformation coordination of materials everywhere in the matrix, which is detrimental to the ability of the matrix to resist deformation and cracking

Moreover, the Cr content is high, which reduces the bonding force between the oxide film and the substrate, and reduces the perforation life of the plug.

[0005] Chinese patent CN1243170A discloses an iron-based rare-earth alloy steel pipe perforation plug material. This patent improves the anti-cold and heat fatigue life of the material by adding rare earth Re, but adding Re will greatly increase the cost

Moreover, the Ni content is less than 2.8%, which will reduce the bonding strength of the oxide film itself and reduce the life of the plug piercing

[0006] Chinese patent CN1788101A discloses a high Mo-high W steel pipe piercing plug material, which is mainly used in the piercing process of materials with high deformation resistance during hot working, and high Cr alloy steel represented by 13% Cr stainless steel and Ni base Used in alloy piercing process, Mo and W can improve high temperature strength, but too high content will reduce the toughness of the material, which is not good for cold and heat fatigue resistance, and also increases the cost

[0007] In the prior art, the high service life of the plug is not realized at low cost. Some plug materials are designed with incorrect Si, Cr, and Ni contents and cannot obtain an oxide film with good bonding force. Some plug materials are added with microalloying such as V Elements, it is easy to cause different plasticity and toughness due to different temperatures during the use of the plug, resulting in incoordination of deformation and easy cracking, which are not good for the high life of the plug.

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