Steel for quenched and tempered coiled tubing, hot rolled steel strip, steel tube and manufacturing methods of hot rolled steel strip and steel tube

Abstract

The invention discloses steel for a quenched and tempered coiled tubing. The steel comprises the following chemical elements including, by mass percent, 0.15%-0.35% of C, 0.08%-0.30% of Si, 0.50%-1.80% of Mn, not larger than 0.015% of P, not larger than 0.005% of S, 0.40%-0.80% of Cr, 0.01%-0.05% of Nb, 0.01%-0.03% of Ti, 0.05%-0.38% of Mo, 0.0003%-0.0015% of B, 0.001%-0.004% of Ca, 0.01%-0.05% of Al and larger than 0 and not larger than 0.006% of N. In addition, the invention further discloses a hot rolled steel strip prepared from the steel for the quenched and tempered coiled tubing and a manufacturing method of an oil casing. In addition, the invention further discloses a steel tube prepared from the hot rolled steel strip. By means of the steel for the quenched and tempered coiled tubing, the alloy cost is effectively controlled, and the prepared hot rolled steel strip is low in strength and has good plasticity, toughness and machining performance. The steel tube prepared from the low-strength hot rolled steel strip has ultrahigh strength, the structure property is uniform, and good fatigue life and corrosion resistance are achieved.

Description

technical field [0001] The invention relates to a metal material and a manufacturing method thereof, in particular to a steel grade, a steel strip, a steel pipe and a manufacturing method thereof. Background technique [0002] Quenched and tempered coiled tubing (Coiled tubing, referred to as CT) is relative to conventional threaded tubing. It is called coiled tubing, coiled tubing, serpentine tubing or coiled tubing. The advantages of coiled tubing in oilfield operations are very prominent, and it has been developed rapidly in the past ten years. It is widely used in oil and gas field workover, drilling, completion, logging and other operations, and is known as the "universal operating machine". [0003] With the development of oil and gas operations and the advancement of drilling and completion technologies, deep wells, high-pressure wells, and horizontal wells have gradually increased. At present, there are vertical wells with a depth of more than 7000m and horizontal w...

AI Technical Summary

Problems solved by technology

The effect of conventional alloying and controlled rolling and controlled cooling processes is also quite limited. If more alloys are added, the cost will increase significantly, and the low-temperature coiling process will cause severe performance fluctuations in the steel strip.

In addition, even if the ultra-high-strength hot-rolled steel strip is obtained, it will have a greater test on the capabilities of the pipe-making equipment, and there will be certain risks

Therefore, the development of ultra-high strength coiled tubing is still relatively difficult

In addition, the current conventional coiled tubing generally only undergoes simple stress relief annealing after the pipe is made. There is a big difference between the structure of the weld and the pipe body, and the welded part has a large residual stress and is more susceptible to corrosion. Failures often occur here

With the improvement of the strength grade of coiled tubing, the fatigue life of the weld seam tends to decrease relative to the pipe body, which has also become a bottleneck for the further improvement of the strength of conventional coiled tubing

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