Steel used for Cr micro-alloyed oil casings and preparation method of steel

An oil casing and micro-alloying technology, applied in the field of oil casing steel, can solve the problems of low yield strength of seamless steel pipes, reduced plasticity and toughness of steel, and sensitivity to coarsening and tempering brittleness of steel grains. Good comprehensive mechanical properties, increased corrosion resistance, high strength margin

Active Publication Date: 2018-03-20
SHANDONG IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the yield strength of seamless steel pipes prepared by this method is not high
When no other strengthening elements are added, the yield strength of the pipes in this application only reaches 380MPa. Higher strength pipes need to be strengthened by adding other elements, and the introduction of other alloying elements will not only increase the cost, And it will lead to fluctuations in product performance. For example, the yield strength of the pipe is 360-45

Method used

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  • Steel used for Cr micro-alloyed oil casings and preparation method of steel
  • Steel used for Cr micro-alloyed oil casings and preparation method of steel
  • Steel used for Cr micro-alloyed oil casings and preparation method of steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1-3

[0025] The manufacturing method of the Cr microalloyed oil casing steel of the present invention comprises the following steps:

[0026] (1) In the electric furnace smelting process, in order to effectively reduce the content of inclusions in the steel, each furnace of steel contains 75% of molten iron + 25% of scrap steel, and the control endpoint C≥0.10% and P≤0.010% during tapping, and the residual elements meet the requirements. The whole process of electric furnace smelting creates foamy slag, uniform decarburization, and reduces gas absorption. The tapping temperature is controlled at 1620°C, and the ladle alloying is carried out at the same time as the lower limit.

[0027] 2) In the refining process outside the LF furnace, the ton of steel slag material is ≥12Kg, and the aluminum wire is fed before taking a sample, and the length of the addition is ≥4m / t. Fine-tune the composition of the ladle according to the composition results of the primary sample. Before LF tapp...

Embodiment 1

[0033]The microstructure of the steel product that embodiment 1 makes please refer to appendix figure 1 .

[0034] Table 2 Gas content in steel

[0035]

[0036]

[0037] Samples were taken from the steels of the examples, and their mechanical properties, tempered hardness, non-metallic inclusions and grain size were tested. Normalizing at 900±15°C for mechanical property heat treatment, please refer to the table below for specific properties.

[0038] Table 3 mechanical properties

[0039]

Rel / Mpa

Pm / Mpa

A / ％

wxya

standard requirement

≥380

≥520

≥24

230-260

Example 1

491 / 481

616 / 608

24 / 24

241 / 244 / 238

Example 2

522 / 500

683 / 662

25 / 24

245 / 250 / 252

Example 3

547 / 541

700 / 711

24 / 25

251 / 246 / 255

[0040] Table 4 Non-metallic inclusions in steel

[0041]

[0042] Table 5 Austenite grain size of steel products (no coarser than grade 6 required by the standard) and low temp...

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PUM

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Abstract

The invention discloses steel used for Cr micro-alloyed oil castings. The steel used for the Cr micro-alloyed oil castings comprises, by mass, 0.25-0.30% of C, 0.25-0.40% of Si, 1.45-1.55% of Mn, 0.020-0.055% of Alt, not larger than 0.015% of Sn, 0.40-0.50% of Cr, not larger than 0.015% of P, not larger than 0.008% of S and the balance the iron element and inevitable impurity elements. The invention further discloses a preparation method of the steel mentioned above. The steel used for the oil castings has the beneficial effects that good comprehensive mechanical performance is achieved and the strength surplus amount is high, and can be suitable for deeper wells; and according to the steel and the method, by adding a certain amount of Cr, for example, 0.40-0.50% of Cr, the requirement forthe steel pipe strength is met and corrosion resistance of the steel is increased to a certain degree.

Description

technical field [0001] The invention relates to the field of steel for oil casing, in particular to a low-carbon steel for oil casing which is micro-alloyed with a small amount of Cr and has good comprehensive mechanical properties. Background technique [0002] Petroleum casing is used in deep wells and complex formation conditions that require stringent casing performance. Therefore, it is required to have good comprehensive performance, that is, high tensile and connection strength, excellent anti-collapse performance, that is, sealing performance, so higher quality requirements are put forward for the tube blank steel used for oil casing. [0003] The Chinese patent application with the application number CN201210007350.1 discloses a high-expansion oil casing steel, which includes C 0.03-0.25%, SI 0.3-2.5%, Mn 0.5-4.0%, Cr 0 -0.5%, S≤0.02, P≤0.02, the balance is iron, and one or more of Nb, Ti and V can be selectively added for strengthening. The metallographic phase o...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/06C22C38/38C21D8/10C21C5/52C21C7/10C21C7/064
CPCC21C5/52C21C7/064C21C7/10C21D8/105C21D2211/005C21D2211/009C22C38/008C22C38/02C22C38/04C22C38/06C22C38/38Y02P10/20
Inventor 李金浩张佩孙相忠任琪时振明欧阳峥荣郑桂云张海霞
Owner SHANDONG IRON & STEEL CO LTD
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