Rare-earth-containing ultrahigh strength collapse-resistant petroleum casing and production method thereof

Abstract

A rare-earth-containing ultrahigh strength collapse-resistant petroleum casing and a production method thereof belong to the technical fields of ferrous metal smelting and metal press working. The petroleum casing comprises the following raw materials by weight percent: 90% of blast furnace molten iron and 10% of high quality steel scrap. The casing blank comprises the following chemical components by weight percent: 0.18-0.35% of C, 0.10-0.35% of Si, 0.55-1.10% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, 0.60-1.10% of Cr, 0.15-0.50% of Mo, 0.01-0.03% of Al, 0.0005-0.0100% of RE ( RE is the mixed rare earth metals of Ce and La and the weight percents of Ce and La are 67% and 33% respectively), less than 0.10% of Cu, less than 0.10% of Ni and the balance of Fe and trace elements. The process flow of the production method is as follows: pretreating molten iron, smelting in a top-bottom blowing converter, refining in a ladle furnace (LF), performing VD vacuum treatment, performing continuous casting of round billets, performing flame cutting, heating the casing blanks, boring, performing continuous rolling, performing sizing and diameter reducing, cooling, performing saw cutting, performing heat treatment, straightening, performing flaw inspection and lathing screw threads. The mechanical properties of the petroleum casing are as follows: the strength is no less than 140000PSI, the residual stress is no more than 80MPa, the impact power is no less than 80J and the grain size is no less than the grade 8. The product is characterized in that the residual stress is low, the content of harmful elements is low, the impact toughness is high, the grains are small, and the product resists extrusion and is difficult to damage.

Description

1. Technical field: [0001] The invention belongs to the field of ferrous metal smelting and metal pressure processing, and relates to a rare-earth-containing ultra-high-strength anti-collapse petroleum casing and a production method thereof. 2. Background technology: [0002] For oil wells under high formation pressure conditions such as rock-salt layers, mudstone layers, and gypsum rock layers, failure accidents of casing collapse often occur, which brings huge economic losses ranging from millions to tens of millions to oilfield production. To meet the stringent requirements of such special geological working conditions for oil casing, the Chinese invention patent "Ultra-high-strength collapse-resistant oil casing with special connection structure and its production method" (patent application number: 01118711.5) discloses a solution The technical solution of the problem, but it has the following problems and shortcomings: [0003] 1. Harmful element Cu (weight% < 0.20...

AI Technical Summary

Problems solved by technology

[0002] For oil wells under high formation pressure conditions such as rock-salt layers, mudstone layers, and gypsum rock layers, failure accidents of casing collapse often occur, which brings huge economic losses ranging from millions to tens of millions to oilfield production. To meet the stringent requirements of such special geological working conditions for oil casing, the Chinese invention patent "Ultra-high-strength collapse-resistant oil casing with special connection structure and its production method" (patent application number: 01118711.5) discloses a solution The technical solution of the problem, but it has the following problems and shortcomings:

[0003] 1. Harmful element Cu (weight% < 0.20%), this is a defect that cannot be overcome by using scrap steel as raw material for smelting in an electric furnace production process, because scrap steel inevitably contains harmful element Cu, and cannot be removed in the steelmaking process;

[0004] 2. High residual stress (≤160MPa), which will reduce the collapse resistance and reduce the safety of use during the use of oil casing;

[0005] 3. Low impact toughness (≥33J), which increases the risk of brittle fracture of the casing during use;

[0006] 4. Coarse grains (≥6 grades) make the strength and toughness of the casing prominent. When the strength is high, the impact toughness is low

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