WO2019029225A1

WO2019029225A1 - Steel for thick-walled large-diameter high-grade steel pipeline having improved low-temperature toughness, and preparation method therefor

Info

Publication number: WO2019029225A1
Application number: PCT/CN2018/088151
Authority: WO
Inventors: 翟冬雨; 姜金星; 杜海军; 员强鹏; 殷杰; 张媛钰
Original assignee: 南京钢铁股份有限公司
Priority date: 2017-08-07
Filing date: 2018-05-24
Publication date: 2019-02-14
Also published as: RU2728366C1; CN107502836B; CN107502836A

Abstract

Steel for a thick-walled large-diameter high-grade steel pipeline having improved low-temperature toughness, and a preparation method therefor. The pipeline steel comprises the following components (in weight percent): 0.038 to 0.058％ of C, 0.17 to 0.27％ of Si, 1.65 to 1.75％ of Mn, less than or equal to 0.01％ of P, less than or equal to 0.003％ of S, 0.015 to 0.05％ of Al, 0.045 to 0.055％ of Nb, 0.006 to 0.02％ of Ti, 0.11 to 0.16％ of Cr, 0.15 to 0.20％ of Mo, 0.10 to 0.16％ of Cu, 0.25 to 0.30％ of Ni, 0.0005 to 0.0040％ of Ca, and the balance of Fe and inevitable impurities. The preparation method therefor comprises using a 320 mm thick section casting blank, and performing blank material heating, rolling, and laminar cooling to ensure different deformation storage energy and grain boundary mobility, to effectively refine the structural grain size, and to obtain uniform bainite and needle ferrite, ensuring the stability of the structure and performance, meeting the performance requirements on steel for a wide and thick high-grade steel pipeline.

Description

Thick-walled large-diameter high-grade steel pipeline steel for improving low-temperature toughness and manufacturing method thereof

Technical field

The invention belongs to the field of iron and steel metallurgy and relates to a production process for improving the low temperature drop hammer of a large diameter pipeline steel, in particular to a thick wall large diameter high steel grade pipeline steel which improves low temperature toughness and a manufacturing method thereof.

Background technique

Thick-walled large-diameter pipeline steel for oil transportation (φ1422×30.8mm thick-walled large-diameter pipeline steel) belongs to high-end products of pipeline steel, requiring large diameters and meeting the requirements for low-temperature service. At present, the existing domestic technology cannot be improved. The barrier of low temperature toughness of this variety. In the prior art, the manufacturing method of the thick-walled large-diameter high-grade steel pipeline steel cannot form the fine bainite and the true ferrite structure, and the band structure of the core cannot be effectively eliminated and the uniformity of strength and toughness is achieved. The fine grain structure meets the requirements of low temperature toughness of the product.

Summary of the invention

The technical problem to be solved by the invention is how to ensure the formation of a fine and uniform bainite and acicular ferrite structure in the core of the rolled piece, to ensure the strength and toughness requirements, and to meet the requirements of the product for the ultra-low temperature drop hammer.

The technical solution of the present invention to solve the above technical problems is:

A thick-walled large-diameter high-grade steel pipeline steel with improved low-temperature toughness, the weight percentage components of which are: C: 0.038-0.058%, Si: 0.17-0.27%, Mn: 1.65-1.75%, P≤0.01%, S≤ 0.003%, Al: 0.015 to 0.05%, Nb: 0.045 to 0.055%, Ti: 0.006 to 0.02%, Cr: 0.11 to 0.16%, Mo: 0.15 to 0.20%, Cu: 0.10 to 0.16%, and Ni: 0.25 to 0.30 %, Ca: 0.0005 to 0.0040%, the balance being Fe and unavoidable impurities. The low-carbon, low-phosphorus and low-sulfur design of the composition is more conducive to the core structure of the slab, which effectively reduces the brittleness of the product. The composition design of Nb, Cr, Mo, Cu and Ni is beneficial to improve the product during the rolling process. The precipitation strength is beneficial to refine the grain of the structure and improve the toughness of the product.

The foregoing method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel for improving low-temperature toughness includes the following steps:

(1) The weight percentage component of the thick-walled large-diameter high-grade steel pipeline steel of low temperature toughness is the aforementioned component;

(2) Using a slab with a thickness of 320mm, the heating temperature of the slab is 1150～1170°C, the heating time is 10.3～13min/cm in thickness of the slab, and the soaking time is 45～90min; the surface and core temperature of the slab are ensured. Uniform, through the low temperature heating system, effectively control the size of the original grain size, providing a guarantee for strengthening the microstructure;

(3) Dephosphorization of 2 passes, including 1 pass of rough rolling and 1 dephosphorization of 2nd pass of finishing rolling; optimization of dephosphorization pass, in order to ensure rolling temperature and surface quality, design 2 times of phosphorus removal, rough rolling Phosphorus 1 and fine dephosphorization in the second pass of the finishing pass not only ensure the surface quality but also reduce unnecessary temperature loss, ensuring the pass reduction rate;

(4) Increasing the reduction ratio of the rough rolling pass, the reduction ratio of the rough rolling pass is more than 25%, and the thickness of the warm blank is 3.5 to 4.0 times the thickness of the steel plate;

(5) using low-temperature rolling, the second-stage rolling temperature is set at 810-830 ° C, and the final rolling temperature is 800-830 ° C;

(6) Adopting the odd-pass rolling process; it can effectively reduce the cooling time;

(7) Set Ar ₃ temperature point to 725.73 degrees, use low inlet water temperature, inlet water temperature 750 ~ 770 ° C; because the core temperature is greater than the surface temperature, the low inlet water temperature ensures that the core temperature of the rolled piece is greater than the Ar3 temperature point, the core structure More uniform, better strength and toughness;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups are cooled according to the maximum flow rate, the flow rate is 300-350 m ³ /h, and the last 8 groups are cooled by a small flow, the flow rate is 200-300 m ³ /h, and the red return temperature is 330-420 ° C; The laminar cooling system improves the grain size of the tissue and reduces the number of Maao islands, which is more conducive to the formation of bainite and acicular ferrite.

Through repeated trials, the invention finally adopts a low-temperature heating system, a low-intake water, and a low-return red rolling process, thereby effectively reducing the grain size of the tissue, obtaining a dense bainite and acicular ferrite structure in the core, and passing the strong cold. Eliminate the unfavorable factors of the band structure, effectively improve the strengthening effect of the precipitation elements, improve the mechanical properties of the product, and meet the requirements of low temperature toughness of the product; thus, the present invention adopts a low carbon design to increase the toughness of the product, and the alloy adopts Nb. , Ti, Cr, Mo, Cu design, increase the precipitation strength during rolling, the heating temperature of the billet adopts low temperature heating system, reduce the dephosphorization pass times, increase the pass reduction rate, odd pass rolling, low water input, low Reddening effectively reduces the grain size of the rolled product and refines the structure. The cooling system effectively eliminates the band structure and ensures the formation of fine and uniform bainite and acicular ferrite structure in the core of the rolled product. The requirements of strength and toughness meet the requirements of the product for ultra-low temperature drop hammer. The invention successfully solves the manufacturing difficulty of the low-temperature drop hammer of the wide and thick pipeline steel, improves the mechanical properties of the steel after rolling, satisfies the requirements of the customer, and greatly improves the economic benefit.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing the metallographic structure of a first embodiment of the present invention.

Figure 2 is a metallographic structure diagram of Embodiment 2 of the present invention.

Figure 3 is a metallographic structure diagram of Embodiment 3 of the present invention.

Detailed ways

Example 1

The embodiment is a method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel with improved low-temperature toughness, comprising the following steps:

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.039%, Si: 0.19%, Mn: 1.68%, P: 0.006%, S: 0.002%, and Al: 0.025% Nb: 0.051%, Ti: 0.0016%, Cr: 0.15%, Mo: 0.19%, Cu: 0.12%, Ni: 0.27%, Ca: 0.0015%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1155 ° C, the heating time is 10.3 min/cm in the thickness of the slab, and the soaking time is 56 min;

(3) Two-stage phosphorus removal, including one pass for rough rolling and one for phosphorus removal in the second pass of finishing rolling;

(5) using low temperature rolling, the second stage rolling temperature is set at 815 ° C, and the final rolling temperature is 810 ° C;

(6) adopting the odd pass rolling process;

(7) Setting the Ar ₃ temperature point to 725.73 degrees, using a low inlet water temperature, and entering the water temperature of 770 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate of 300m ³ / h after 8 groups with a small flow cooling, flow 200m ³ / h, red return temperature 350 ° C.

Example 2

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.043%, Si: 0.217%, Mn: 1.66%, P: 0.006%, S: 0.001%, and Al: 0.020% Nb: 0.052%, Ti: 0.009%, Cr: 0.13%, Mo: 0.17%, Cu: 0.15%, Ni: 0.26%, Ca: 0.001%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1167 ° C, the heating time is 11 min / cm in thickness of the slab, and the soaking time is 58 min;

(5) using low temperature rolling, the second stage rolling temperature is set at 811 ° C, and the final rolling temperature is 810 ° C;

(6) adopting the odd pass rolling process;

(7) setting the Ar ₃ temperature point to 725.73 degrees, using a low inlet water temperature, and entering the water temperature of 760 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate is 320m ³ /h, the last 8 groups use a small flow, the flow rate is 250m ³ /h cooling, the red return temperature is 365 °C.

Example 3

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.044%, Si: 0.218%, Mn: 1.67%, P: 0.007%, S: 0.002%, and Al: 0.036% Nb: 0.054%, Ti: 0.011%, Cr: 0.12%, Mo: 0.17%, Cu: 0.13%, Ni: 0.28%, Ca: 0.0020%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1158 ° C, the heating time is 12 min / cm in thickness of the slab, and the soaking time is 57 min;

(5) using low temperature rolling, the second stage rolling temperature is set at 813 ° C, and the final rolling temperature is 801 ° C;

(6) adopting the odd pass rolling process;

(7) Setting the Ar ₃ temperature point to 725.73 degrees, using a low inlet water temperature and a water inlet temperature of 761 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate of 340m ³ / h after 8 groups using a small flow, flow 280m ³ / h cooling, red return temperature 365 ° C.

Example 4

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.053%, Si: 0.21%, Mn: 1.70%, P: 0.006%, S: 0.001%, and Al: 0.035% , Nb: 0.047%, Ti: 0.02%, Cr: 0.15%, Mo: 0.17%, Cu: 0.13%, Ni: 0.30%, Ca: 0.00240%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1150 ° C, the heating time is 13 min / cm in thickness of the slab, and the soaking time is 55 min;

(5) using low temperature rolling, the second stage rolling temperature is set at 822 ° C, and the final rolling temperature is 813 ° C;

(6) adopting the odd pass rolling process;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate of 350m ³ / h after 8 groups using a small flow, flow 300m ³ / h cooling, 200 ~ 300m ³ / h red return temperature 410 ° C.

The metallographic structure of Figures 1, 2 and 3 was obtained by using the above Examples 1-3. It can be seen from the figure that the core structure is uniform and fine, and there is no granular or island distribution in the tissue, mainly bainite and acicular ferrite. The body structure is dominant, the acicular ferrite has the characteristics of bainite, and is similar in morphology to the carbon-free bainite in low carbon steel. The type of structure is mainly soft phase ferrite, which improves the toughness and improves the impact. Resilience is beneficial.

Table 2 Mechanical properties of various embodiments of the invention

It can be seen from Table 2 that the mechanical properties of Examples 1, 2, 3 and 4 all meet the requirements of X80 in API 5L standard and the requirements of CNPC Sino-Russian East Line customers, with significant economic benefits, and the ultra-low temperature drop hammer shear area is greater than 85%. The production method of the invention is simple and easy, and the comprehensive performance of the material is improved.

Other than the above-described embodiments, the present invention may have other embodiments. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

A thick-walled large-diameter high-grade steel pipeline steel with improved low-temperature toughness, characterized in that the weight percentage components are: C: 0.038-0.058%, Si: 0.17-0.27%, Mn: 1.65-1.75%, P≤0.01 %, S≤0.003%, Al: 0.015 to 0.05%, Nb: 0.045 to 0.055%, Ti: 0.006 to 0.02%, Cr: 0.11 to 0.16%, Mo: 0.15 to 0.20%, Cu: 0.10 to 0.16%, Ni : 0.25 to 0.30%, Ca: 0.0005 to 0.0040%, the balance being Fe and unavoidable impurities.
The method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel with improved low-temperature toughness according to claim 1, comprising the steps of:

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.038-0.058%, Si: 0.17-0.27%, Mn: 1.65-1.75%, P≤0.01%, S≤0.003 %, Al: 0.015 to 0.05%, Nb: 0.045 to 0.055%, Ti: 0.006 to 0.02%, Cr: 0.11 to 0.16%, Mo: 0.15 to 0.20%, Cu: 0.10 to 0.16%, and Ni: 0.25 to 0.30% Ca: 0.0005 to 0.0040%, the balance being Fe and unavoidable impurities;

(2) using a slab having a thickness of 320 mm, the heating temperature of the slab is 1150 to 1170 ° C, and the heating time is 10.3 to 13 min/cm in the thickness of the slab, and the soaking time is 45 min to 90 min;

(3) Two-stage phosphorus removal, including one pass for rough rolling and one for phosphorus removal in the second pass of finishing rolling;

(4) Increasing the reduction ratio of the rough rolling pass, the reduction ratio of the rough rolling pass is more than 25%, and the thickness of the warm blank is 3.5 to 4.0 times the thickness of the steel plate;

(5) using low-temperature rolling, the second-stage rolling temperature is set at 810-830 ° C, and the final rolling temperature is 800-830 ° C;

(6) adopting the odd pass rolling process;

(7) Setting the Ar 3 temperature point to 725.73 degrees, using a low inlet water temperature, and entering the water temperature of 750 to 770 ° C;

(8) Laminar cooling a total of 12 groups of water, the first 4 groups are cooled according to the maximum flow rate, the flow rate is 300-350 m 3 /h, and the last 8 groups are cooled by a small flow, the flow rate is 200-300 m 3 /h, and the red-back temperature is 330-420 °C.
The method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel for improving low-temperature toughness according to claim 2, comprising the steps of:

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.048%, Si: 0.19%, Mn: 1.68%, P: 0.008%, S: 0.002%, and Al: 0.025% Nb: 0.05%, Ti: 0.006%, Cr: 0.13%, Mo: 0.19%, Cu: 0.13%, Ni: 0.28%, Ca: 0.0015%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1155 ° C, the heating time is 10.3 min/cm in the thickness of the slab, and the soaking time is 55 min;

(3) Two-stage phosphorus removal, including one pass for rough rolling and one for phosphorus removal in the second pass of finishing rolling;

(4) Increasing the reduction ratio of the rough rolling pass, the reduction ratio of the rough rolling pass is more than 25%, and the thickness of the warm blank is 3.5 to 4.0 times the thickness of the steel plate;

(5) using low temperature rolling, the second stage rolling temperature is set at 815 ° C, and the final rolling temperature is 810 ° C;

(6) adopting the odd pass rolling process;

(7) Setting the Ar 3 temperature point to 725.73 degrees, using a low inlet water temperature, and entering the water temperature of 770 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate of 300m 3 / h after 8 groups with a small flow cooling, flow 200m 3 / h, red return temperature 350 ° C.
The method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel for improving low-temperature toughness according to claim 2, comprising the steps of:

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.043%, Si: 0.217%, Mn: 1.66%, P: 0.006%, S: 0.001%, and Al: 0.020% , Nb: 0.052%, Ti: 0.009%, Cr: 0.11%, Mo: 0.16%, Cu: 0.15%, Ni: 0.26%, Ca: 0.001%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1167 ° C, the heating time is 11 min / cm in thickness of the slab, and the soaking time is 51 min;

(3) Two-stage phosphorus removal, including one pass for rough rolling and one for phosphorus removal in the second pass of finishing rolling;

(4) Increasing the reduction ratio of the rough rolling pass, the reduction ratio of the rough rolling pass is more than 25%, and the thickness of the warm blank is 3.5 to 4.0 times the thickness of the steel plate;

(5) using low temperature rolling, the second stage rolling temperature is set at 811 ° C, and the final rolling temperature is 810 ° C;

(6) adopting the odd pass rolling process;

(7) setting the Ar 3 temperature point to 725.73 degrees, using a low inlet water temperature, and entering the water temperature of 760 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow, flow rate 320m 3 /h, the latter 8 groups use a small flow, flow 250m 3 / h cooling, red return temperature 365 ° C.
The method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel for improving low-temperature toughness according to claim 2, comprising the steps of:

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.044%, Si: 0.218%, Mn: 1.67%, P: 0.007%, S: 0.002%, and Al: 0.036% Nb: 0.054%, Ti: 0.011%, Cr: 0.12%, Mo: 0.17%, Cu: 0.16%, Ni: 0.28%, Ca: 0.0020%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1158 ° C, the heating time is 12 min/cm in the thickness of the slab, and the soaking time is 48 min;

(3) Two-stage phosphorus removal, including one pass for rough rolling and one for phosphorus removal in the second pass of finishing rolling;

(4) Increasing the reduction ratio of the rough rolling pass, the reduction ratio of the rough rolling pass is more than 25%, and the thickness of the warm blank is 3.5 to 4.0 times the thickness of the steel plate;

(5) using low temperature rolling, the second stage rolling temperature is set at 813 ° C, and the final rolling temperature is 801 ° C;

(6) adopting the odd pass rolling process;

(7) Setting the Ar 3 temperature point to 725.73 degrees, using a low inlet water temperature and a water inlet temperature of 761 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate of 340m 3 / h after 8 groups using a small flow, flow 280m 3 / h cooling, red return temperature 365 ° C.
The method for manufacturing a thick-walled large-diameter high-grade steel pipeline steel for improving low-temperature toughness according to claim 2, comprising the steps of:

(1) The weight percentage components of the low-temperature tough thick-walled large-diameter high-grade steel pipeline steel are: C: 0.051%, Si: 0.21%, Mn: 1.70%, P: 0.006%, S: 0.001%, and Al: 0.035% , Nb: 0.046%, Ti: 0.012%, Cr: 0.13%, Mo: 0.19%, Cu: 0.15%, Ni: 0.29%, Ca: 0.00240%, balance Fe and unavoidable impurities;

(2) using a slab with a thickness of 320 mm, the heating temperature of the slab is 1150 ° C, the heating time is 13 min/cm in the thickness of the slab, and the soaking time is 49 min;

(3) Two-stage phosphorus removal, including one pass for rough rolling and one for phosphorus removal in the second pass of finishing rolling;

(4) Increasing the reduction ratio of the rough rolling pass, the reduction ratio of the rough rolling pass is more than 25%, and the thickness of the warm blank is 3.5 to 4.0 times the thickness of the steel plate;

(5) using low temperature rolling, the second stage rolling temperature is set at 822 ° C, and the final rolling temperature is 813 ° C;

(6) adopting the odd pass rolling process;

(7) setting the Ar 3 temperature point to 725.73 degrees, using a low inlet water temperature, and entering the water temperature of 760 ° C;

(8) Laminar flow cooling a total of 12 groups of water, the first 4 groups according to the maximum flow rate, the flow rate of 350m 3 / h after 8 groups using a small flow, flow 300m 3 / h cooling, 200 ~ 300m 3 / h red return temperature 410 ° C.