Steel for petroleum casing pipe, high-frequency electric resistance welding petroleum casing pipe and methods for manufacturing steel for petroleum casing pipe and high-frequency electric resistance welding petroleum casing pipe

Abstract

The invention discloses steel for a petroleum casing pipe and a 125ksi steel-class high-frequency electric resistance welding casing pipe. The steel comprises the following raw materials in percentage by mass: 0.15 to 0.3 percent of C, 0.1 to 0.5 percent of Si, 0.6 to 1.2 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.1 to 0.5 percent of Mo, 0.08 to 0.2 percent of V, 0.01 to 0.05 percent of Ti, 0.01 to 0.05 percent of Nb, and the balance of Fe and inevitable impurities, wherein the carbon equivalent of the steel is less than or equal to 0.55. The invention also discloses a method for manufacturing the steel for the petroleum casing pipe, a method for CO2 gas shield welding and a method for manufacturing a high-frequency electric resistance welding casing pipe.

Description

Technical field [0001] The invention relates to a steel for petroleum casing, in particular to a steel for petroleum casing and a manufacturing method thereof and CO 2 A gas shielded welding method, a 125ksi steel grade high frequency resistance welding petroleum casing made of the steel and a manufacturing method thereof. Background technique [0002] The API standard stipulates that petroleum casing is divided into two types: seamless pipe and welded casing. Compared with seamless pipes, welded casing has obvious characteristics such as high production efficiency, good dimensional accuracy, wide specification range, and low cost. Therefore, it is the first choice for manufacturers and oilfield users and has always been favored by the market. [0003] The traditional production process of high-frequency resistance welding petroleum casing is: according to the needs of casing performance, design suitable chemical composition, smelt and roll into hot-rolled coils, and make the coils...

AI Technical Summary

Problems solved by technology

[0006] In order to obtain the high strength and high toughness of 125ksi steel grade products, alloying elements need to be added, but the addition of alloying elements will make the carbon equivalent higher than 0.43, resulting in CO 2 The weld seam of gas shielded welding breaks during the pipe making process

[0007] JP07173541A and JP06017127A use post-welding tempering or normalizing heat treatment to produce ERW steel pipes for high-strength mechanical structures. The steel grades have high alloy content and high carbon equivalent, which will cause problems in the head-to-tail welding of coils during continuous production. And its toughness is low, not suitable for the production of 125ksi steel grade oil casing

[0008] CN101376946A provides a kind of 110ksi steel grade straight seam welded oil casing steel, but this straight seam welded oil casing has low strength and is not suitable for the production of 125ksi products

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