Low-alloy steel used for oil well pipe with carbon dioxide corrosion resistance and manufacturing method thereof

Abstract

The invention relates to a low-alloy steel used for an oil well pipe, and the low-alloy steel comprises the following chemical components in percentage by weight: 0.20-0.40% of C, 0.10-1.0% of Si, 0.50-2.0% of Mn, 0.5-1.5% of Cr, 0.02-0.2% of V, 0.01-0.10% of Al, 0.005-0.03% of N, 0.02-0.2% of Nb, less than or equal to 0.015% of P, less than or equal to 0.005% of S and the balance of Fe and inevitable impurities, wherein the total content of the impurity elements is less than 0.05wt. The invention also relates to a manufacturing method of the low-alloy steel. The manufacturing method comprises the following steps: performing steel making at the initial tapping temperature of 1600-1700 DEG C; performing continuous casting at the initial temperature of 1530-1570 DEG C, wherein in order to reduce the centre cracks and drawhole occurrence rates of a casting blank, the pulling rate of the continuous casting is controlled to be below 2.3m/min, and banding segregation is controlled to be within the level of 2.5; beginning performing perforation rolling at the temperature of 1180-1220 while performing hot rolling on the continuous casting blank; performing final stretch reducing until the temperature is 890-910 DEG C; and after hot rolling, air-cooling a steel tube to room temperature, thus obtaining the low-alloy steel used for the oil well pipe, wherein the low-alloy steel is provided with ferrite and pearlitic structures and has carbon dioxide and chloride ion corrosion resistance.

Description

technical field [0001] The invention relates to a low alloy steel, in particular to a carbon dioxide and chloride ion corrosion-resistant low alloy steel for oil well pipes with a ferrite + pearlite structure and a manufacturing method. Background technique [0002] Pipe CO 2 Corrosion is a major safety issue that must be faced in the development of oil and gas fields. Various alloy oil casings with carbon dioxide corrosion resistance must be used to ensure the safety of mining and development. For higher CO 2 Partial pressure, high chloride ion content, low PH value, high pressure in the well and fluid scouring form a strong corrosive environment, the use of excellent anti-CO 2 Super 13Cr martensitic stainless steel with corrosion performance is the most effective way to ensure safe and efficient production in oil fields. However, for most low-abundance and low-permeability oil fields with short production life in my country, the cost of using stainless steel oil casing ...

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Problems solved by technology

However, most of these documents involve medium-high alloy super 13Cr and duplex stainless steel, and the high-temperature quenching + tempering process must be used in the manufacturing process.

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