CN104109805A - Steel strip for oil casing and production method of steel strip for oil casing - Google Patents

Abstract

The invention relates to a steel strip for oil casing and a production method of the steel strip for oil casing and belongs to the field of alloy steel. The technical problem to be solved by the invention is to provide hot rolled steel for oil casing and a production method of the hot rolled steel for oil casing. The steel strip for oil casing disclosed by the invention comprises the following chemical components in percentage by weight: 0.15%-0.20% of C, 0.10%-0.20% of Si, 0.95%-1.20% of Mn, less than or equal to 0.025% of P, less than or equal to 0.015% of S, 0.05%-0.010% of V, 0.008%-0.020% of Ti and the balance of iron and inevitable impurities. Furthermore, the invention also discloses a production method of the steel strip for oil casing. The steel strip for oil casing prepared by the invention has the characteristics that the yield ratio is less than 0.08, and the elongation is equal to or greater than 37%; and excellent weldability and formability are achieved.

Description

Steel strip for oil casing and production method thereof

technical field

The invention relates to a steel strip for petroleum casing and a production method thereof, belonging to the field of alloy steel.

Background technique

Oil casing is an important pipeline material in the process of oil and natural gas exploitation. Oil casing has always been made of seamless steel pipes. However, with the development of microalloying technology and controlled rolling and controlled cooling technology, hot continuous rolling strip steel can obtain excellent Comprehensive performance, after welding and forming, it can completely replace seamless steel pipes, and has the advantages of high dimensional accuracy, uniform wall thickness, strong extrusion resistance, no cracking after perforation, and low price. It is gradually replacing seamless steel pipes.

J55 straight seam welded oil casing steel strip is required to meet the corresponding strength requirements, but also requires good welding performance, formability and impact toughness. The yield ratio is an important index to measure its formability. The yield ratio is low, indicating that Its formability is good. Domestic iron and steel manufacturers such as Baosteel, Anshan Iron and Steel, Benxi Iron and Steel, and Meishan Iron and Steel are all producing J55 steel strips for longitudinal seam welding of oil casings, but generally use Nb microalloying, which has a relatively high yield strength.

In the Chinese patent application with the application number 200310104862.0, Nb microalloying is used in the oil casing, but the coiling temperature is 430°C-470°C. Such harsh rolling process conditions are difficult to achieve on a general hot continuous rolling mill. It is not conducive to large-scale industrial promotion.

The patent application with the publication number CN101200791B discloses a low-cost oil casing steel and its production method. %, P≤0.020%, S≤0.009%, Nb: 0.020%-0.030%, Ti: 0.010%-0.020%, and the rest are Fe and unavoidable impurities. In CN100560711C disclosed high-strength toughness J55 oil casing steel strip and its manufacturing method, its chemical composition is C: 0.15%～0.20%, Si: 0.15%～0.30%, Mn: 1.00%～1.45%, P≤0.020%, S≤0.010%, Nb: 0.020%-0.040%, Ti: 0.015%-0.040%. These two patents use Nb and Ti composite microalloying, and the Nb content is high, not only the production cost is high, but also the yield strength ratio is high.

The petroleum casing of Chinese patent CN01126611.2 adopts V-Ni-B microalloying, the V content is 0.07%-0.13%, the Ni content is 0.05-0.25%, the alloy elements are many, and the production cost is high.

In the low-alloy steel used in the manufacture of J55-grade welded petroleum casing with publication number CN1924061A, its chemical composition is C: 0.16% to 0.21%, Si: 0.10% to 0.35%, Mn: 1.00% to 1.30%, P≤0.020% , S ≤ 0.012%, V: 0.020% ~ 0.070%, Als: 0.008% ~ 0.060%, the rest is Fe and inevitable impurities; but its yield ratio and elongation are not ideal.

Therefore, it is particularly important to find a hot-rolled steel for oil casing with low yield ratio and high elongation.

Contents of the invention

The technical problem to be solved by the present invention is to provide a hot-rolled steel for oil casing and a production method thereof.

The steel strip for petroleum casing of the present invention has the following chemical components by weight percentage: C: 0.15% to 0.20%, Si: 0.10% to 0.20%, Mn: 0.95% to 1.20%, P≤0.025%, S≤0.015% , V: 0.05% to 0.010%, Ti: 0.008% to 0.020%, and the rest are Fe and unavoidable impurities.

Further, as a preferred solution, the chemical composition of the steel strip for petroleum casing of the present invention is composed by weight percentage: C: 0.15% to 0.20%, Si: 0.12% to 0.20%, Mn: 0.98% to 1.15%, P≤ 0.020%, S≤0.009%, V: 0.07%-0.09%, Ti: 0.012%-0.017%, and the rest are Fe and unavoidable impurities.

Further, the present invention also discloses the production method of the steel strip for oil casing pipes of the present invention, including the steps of smelting, molten iron pretreatment, LF furnace refining, continuous casting, heating, rolling and coiling; rolling includes rough rolling and finishing Rolling; other steps except the heating and rolling steps can adopt the existing method, the heating temperature is 1180～1230 ℃, the rough rolling temperature is 1180～1230 ℃, the finish rolling entrance temperature is 980～1030 ℃, the final rolling The temperature range is 810-880°C.

Further, as a preferred solution, the deformation of each pass of the rough rolling is ≥ 20%, and the thickness of the intermediate billet is more than 4 times the thickness of the finished product; the deformation of the penultimate pass of the finish rolling is more than 20%, and the penultimate pass The deformation of the first pass is above 17%, and the deformation of the last pass is above 10%.

As a more preferred solution, the deformation of each pass of the rough rolling is 20-40%, and the thickness of the intermediate billet is 4-6 times the thickness of the finished product; the deformation of the last third pass of the finish rolling is 20-30%, and the last The deformation amount of the second pass is 17-20%, and the deformation amount of the last pass is 10-15%.

Further, as a preferred solution, after the finish rolling, it is cooled to 580-650° C. at a cooling rate of 50-100° C./s, and then coiled.

Beneficial effects of the present invention:

1. The steel strip for oil casing of the present invention meets the mechanical performance requirements of J55 oil casing;

2. The yield ratio of the steel strip for petroleum casing of the present invention is lower than 0.08;

3. The elongation rate of the steel strip for petroleum casing of the present invention is ≥37%;

4. The steel strip for petroleum casing of the present invention has good welding performance and forming performance;

5. The preparation method of the steel strip for petroleum casing of the present invention has the advantages of simple production process, strong adaptability, and can be produced in general hot continuous rolling production.

Detailed ways

The steel strip for petroleum casing of the present invention has the following chemical components by weight percentage: C: 0.15% to 0.20%, Si: 0.10% to 0.20%, Mn: 0.95% to 1.20%, P≤0.025%, S≤0.015% , V: 0.05% to 0.010%, Ti: 0.008% to 0.020%, and the rest are Fe and unavoidable impurities.

Among them, C is the main strengthening element, but if the C content is too high, the plasticity, toughness and welding performance of the steel will be reduced, and if the C content is too low, the machinability of the steel strip for oil casing will be affected, so the C content is controlled at 0.15% ~0.20%. The main function of Mn is solid solution strengthening. When the upper limit of C content is limited, the Mn content should be increased appropriately. The Mn/Si ratio will affect the machinability of the steel strip for oil casing. Generally, the Mn/Si ratio is required to be not less than 3.5; therefore, the Mn content is controlled at 0.95% to 1.20%, and the Si content is controlled at 0.10% to 0.20%. The main function of V in steel is precipitation strengthening. Adding a small amount of Ti in steel can improve the structure of welding heat-affected zone and improve the toughness of welded joints.

Further, as a preferred solution, the chemical composition of the above-mentioned steel strip for oil casing is composed by weight percentage: C: 0.15% to 0.20%, Si: 0.12% to 0.20%, Mn: 0.98% to 1.15%, P≤0.020% , S≤0.009%, V: 0.07% to 0.09%, Ti: 0.012% to 0.017%, and the rest are Fe and unavoidable impurities.

Further, the present invention also discloses the production method of the steel strip for oil casing pipes of the present invention, including the steps of smelting, hot metal pretreatment, LF furnace refining, continuous casting, heating, rolling and coiling, and the specific process is: hot metal desulfurization→converter Smelting compound blowing → deoxidation, alloying and high alkalinity refined slag desulfurization → small platform behind the furnace to feed Al wire → LF furnace Ti microalloying, alloy composition fine-tuning and V microalloying → feeding calcium wire → continuous casting → plate Billet heating→high pressure water descaling→rough rolling→finish rolling→laminar cooling→coiling→packing and storage.

Further, the heating temperature of the slab is controlled at 1180-1230°C, which not only ensures sufficient solid solution of V, but also prevents abnormal growth of austenite grains.

During rough rolling, keep the temperature at 1180-1230°C. According to the thickness of the finished product, select the appropriate rough-rolling pass. As an optimal solution, 200-250mm thick continuous casting slabs are generally rolled in 5 or 7 passes. The pass deformation must be ≥ 20% to ensure austenite recrystallization and refine austenite grains. The thickness of the intermediate billet must be more than 4 times the thickness of the finished product to ensure the total deformation of the finish rolling.

The finish rolling entrance temperature is controlled at 980-1030°C, the deformation of the penultimate pass of finish rolling is more than 20%, the deformation of the penultimate pass is more than 17%, and the deformation of the last pass is more than 10%. The temperature range is 810-880°C. The above-mentioned process can ensure the deformation amount in the non-recrystallized area, increase the deformation zone, increase the core of phase deformation nuclei, and refine the ferrite grains.

Further, as a more preferred solution, the deformation of each pass of the rough rolling is 20-40%, and the thickness of the intermediate billet is 4-6 times the thickness of the finished product; the deformation of the penultimate pass of the finish rolling is 20-30% , the deformation amount of the penultimate pass is 17-20%, and the deformation amount of the last pass is 10-15%.

The laminar flow cooling after finishing rolling adopts the front-stage cooling method, cooling to the pearlite transformation zone of 580-650°C at a cooling rate of 50-100°C/s, and performing coiling and centralized stacking cooling.

The specific implementation of the present invention will be further described below in conjunction with the examples, and the present invention is not limited to the scope of the examples.

Embodiment 1 Adopting the method of the present invention to prepare hot-rolled steel for oil casing

The specific process is: hot metal desulfurization→converter smelting compound blowing→deoxidation, alloying and desulfurization of high-alkalinity refining slag→replenishing Al wire on the small platform behind the furnace→Ti microalloying in LF furnace, fine-tuning of alloy composition and V microalloying→ Calcium feeding line→continuous casting→slab heating→high pressure water descaling→rough rolling→finish rolling→laminar cooling→coiling; among them, the components of the hot continuous rolling steel strip for pipes are shown in Table 1, and the process parameters of each step are shown in Table 2 and Table 3, see Table 4 for mechanical properties.

Table 1

Example C Si mn P S V Ti 1 0.17 0.17 1.15 0.017 0.004 0.07 0.012

Table 2

table 3

Table 4

Embodiment 2-10

Adopt the method in the embodiment 1 to produce the steel strip for oil casing, the components are shown in Table 5, and the process parameters of each step are shown in Table 6 and Table 7,

The mechanical properties are shown in Table 8.

table 5

Example C Si mn P S V Ti 2 0.18 0.18 0.98 0.015 0.008 0.07 0.015 3 0.19 0.12 1.06 0.017 0.003 0.08 0.014 4 0.16 0.17 1.15 0.012 0.009 0.07 0.017 5 0.15 0.19 1.08 0.020 0.004 0.08 0.014 6 0.20 0.18 1.12 0.014 0.005 0.09 0.017 7 0.19 0.16 1.16 0.017 0.006 0.07 0.012 8 0.18 0.17 1.03 0.015 0.008 0.08 0.016 9 0.19 0.19 1.10 0.016 0.005 0.07 0.015

Continued Table 5

10 0.18 0.20 1.15 0.015 0.008 0.08 0.014

Table 6

Table 7

Table 8

Continued Table 8

3 433 582 40.0 0.74 combine 4 444 616 38.5 0.72 combine 5 457 609 42.0 0.75 combine 6 435 593 41.5 0.73 combine 7 429 591 43.5 0.73 combine 8 449 605 37.0 0.74 combine 9 457 619 40.5 0.74 combine 10 432 608 37.5 0.71 combine

Comparative example 1

The steel strip for petroleum casing was produced using the chemical composition in Example 1, but the hot rolling process was changed. The hot rolling parameters are shown in Table 9 and the mechanical properties are shown in Table 10.

Table 9

Table 10

As can be seen from Table 10, its yield ratio is significantly higher than that of Example 1.

Claims (6)

1. Steel belt for oil casing, characterized in that its chemical composition is composed of: C: 0.15% to 0.20%, Si: 0.10% to 0.20%, Mn: 0.95% to 1.20%, P≤0.025%, S≤0.015%, V: 0.05%-0.010%, Ti: 0.008%-0.020%, and the rest are Fe and unavoidable impurities. 2. The steel strip for oil casing according to claim 1, characterized in that its chemical composition is composed of: C: 0.15% to 0.20%, Si: 0.12% to 0.20%, Mn: 0.98% to 1.15% %, P≤0.020%, S≤0.009%, V: 0.07%-0.09%, Ti: 0.012%-0.017%, and the rest are Fe and unavoidable impurities. 3. The preparation method of the steel strip for oil casing according to claim 1 or 2, comprising a heating step and rolling before rolling, and rolling includes rough rolling and finish rolling, characterized in that: the heating temperature is 1180 ～1230℃, the rough rolling temperature is 1180～1230℃, the finish rolling entrance temperature is 980～1030℃, and the finish rolling temperature is 810～880℃. 4. The method for preparing steel strip for oil casing according to claim 3, characterized in that: the deformation of each pass of the rough rolling is ≥ 20%, the thickness of the intermediate billet is more than 4 times the thickness of the finished product; The deformation of the three passes is above 20%, the deformation of the penultimate pass is above 17%, and the deformation of the last pass is above 10%. 5. The method for preparing a steel strip for oil casing according to claim 4, characterized in that: the deformation of each pass of the rough rolling is 20-40%, and the thickness of the intermediate billet is 4-6 times the thickness of the finished product; The deformation amount of the third last pass is 20-30%, the deformation amount of the penultimate pass is 17-20%, and the deformation amount of the last pass is 10-15%. 6. The method for preparing a steel strip for oil casing according to any one of claims 3 to 5, further comprising a coiling step after rolling, characterized in that: after finish rolling, the steel strip is cooled at 50 to 100°C/s Speed cooling to 580 ~ 650 ℃, and then coiling.