CN111270137A - A kind of anti-acid corrosion pipeline steel X52MS hot-rolled coil and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of ferrous metallurgy, and relates to an acid corrosion resistant pipeline steel X52MS hot-rolled coil which comprises the following components in percentage by weight: 0.03-0.10% of C, 0.45-0.80% of Mn, 0.10-0.30% of Si, 0.010-0.050% of Al, 0.25-0.40% of Cr, 0.015-0.035% of Ti, less than or equal to 0.012% of P, less than or equal to 0.0050% of S, less than or equal to 0.0060% of N, less than or equal to 0.0040% of O, 0.030-0.065% of Nb, 0.015-0.045% of V, and the balance of Fe and inevitable impurities. The invention also discloses a preparation method of the X52MS hot-rolled coil, which greatly improves the production efficiency of the pipeline steel, reduces the energy consumption and the production cost, prolongs the service life and is beneficial to meeting the requirements of social development.

Description

A kind of anti-acid corrosion pipeline steel X52MS hot-rolled coil and preparation method thereof

technical field

The invention belongs to the technical field of iron and steel metallurgy, and relates to an acid corrosion-resistant pipeline steel X52MS hot-rolled coil and a preparation method thereof.

Background technique

Acid corrosion-resistant pipeline steel is mainly used to manufacture pipelines for transporting sour natural gas, and it is the most difficult type of oil and gas steel to produce. The steel has very strict requirements on composition design, smelting technology, rolling technology and metallurgical equipment level. Therefore, the production of acid-resistant pipeline steel represents the highest level of pipeline steel production in a country and a steel plant. Due to the high service risk and difficult production of acid-resistant pipeline steel, only a few steel companies in the world, such as European Steel Pipe, Dillingen, Japan Nippon Steel and JFE, can produce batches and stably. Industrial trial production and mass production of corroded pipeline steel. In addition, the current acid corrosion-resistant X52MS pipeline steel has shortcomings such as high preparation cost and complex process in the manufacturing process. There is an urgent need to optimize the development of new acid-resistant X52MS pipeline steel, improve the quality of pipeline steel, and optimize the preparation method of pipeline steel.

Therefore, those skilled in the art are devoted to developing an acid corrosion-resistant X52MS pipeline steel and a preparation method thereof.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that in the preparation process of X52MS pipeline steel, the purity of molten steel and the internal quality of the casting billet are low, and the design of pipeline steel alloy composition is unreasonable, and harmful elements sulfur, phosphorus and The gas content is high, and the content of non-metallic inclusions in the steel cannot be controlled.

The object of the present invention can be realized through the following technical solutions:

The invention provides an acid corrosion-resistant pipeline steel X52MS hot-rolled coil, comprising the following components by weight percentage: C 0.03-0.10%, Mn 0.45-0.80%, Si 0.10-0.30%, Al 0.010-0.050%, Cr 0.25-0.40%, Ti 0.015-0.035%, P≤0.012%, S≤0.0050%, N≤0.0060%, O≤0.0040%, Nb 0.030-0.065%, V 0.015-0.045%, the balance is Fe and unavoidable Inclusions.

Another aspect of the present invention provides a method for preparing an acid-corrosion-resistant pipeline steel X52MS hot-rolled coil. . Heating system: ensure that the slab discharge temperature is greater than or equal to 1180°C; the finish rolling outlet temperature target is 820°C; the coiling temperature target is 550°C.

Further, it includes the following process flow: molten iron pretreatment→converter smelting→out-of-furnace refining→continuous casting→(2300 hot rolling) heating→rough rolling, finishing rolling→controlled cooling→coiling.

Further, in the molten iron pretreatment, S≤0.005% in the furnace.

Further, in the converter smelting process, the Als of the ladle is controlled at 0.005-0.015%; the ladle N is required to be less than or equal to 30ppm.

Further, in the out-of-furnace refining process, the amount of increased N is less than or equal to 10 ppm.

Further, in the continuous casting process, the nozzle is controlled to absorb N, and the increase of N is controlled to be less than or equal to 5ppm; the high basicity slag is used, and the middle bag is controlled at a superheat degree of less than or equal to 25°C.

Beneficial effects of the present invention:

An acid corrosion-resistant pipeline steel X52MS hot-rolled coil is designed with low carbon, extremely low phosphorus, ultra-low sulfur and micro-alloying in the composition design, and cooperates with pure steel technology and controlled rolling and controlled cooling process, mechanical properties and The indicators of anti-HIC and SSCC corrosion meet the requirements. The use of acid-resistant pipeline steel X52MS to manufacture pipelines that transport sour natural gas can greatly improve the service life of the pipeline, reduce the loss of steel caused by corrosion, and bring huge social and economic benefits.

Detailed ways

In view of the following technical problems in the prior art: the present invention improves the purity of molten steel and the internal quality of the casting billet, because the acid corrosion-resistant pipeline steel is the steel with the highest performance requirements and the greatest difficulty in production among the steels for oil and natural gas. The control requirements for the cleanliness of molten steel and the central segregation of continuous casting billets are extremely high, and the control of sulfur content is close to the limit control. Therefore, the development of acid corrosion-resistant pipeline steel has very strict requirements on the production process, especially the steelmaking process.

The alloy design of acid corrosion resistant pipeline steel X52MS should take low carbon, extremely low phosphorus, ultra low sulfur and micro-alloying as the main design ideas in the chemical composition design of acid corrosion resistant pipeline steel, and cooperate with pure steel technology and controlled rolling and controlled cooling. Process; The key point of production control is to minimize the content of harmful elements sulfur, phosphorus and gas in the steel, and the second is to reduce the content of non-metallic inclusions in the steel, especially the MnS inclusions that are very harmful to the HIC resistance of the steel. The inclusions are denatured, so that the sulfides are distributed in small mass, and the tissue is uniformly refined and dense.

In order to obtain excellent H2S corrosion resistance of acid-resistant pipeline steel X52MS, it is necessary to require molten steel to have good purity and reasonable micro-alloying design, and at the same time reduce the segregation and inclusions of molten steel during solidification.

The present invention: alloy composition core requirements: the following components by weight: C 0.03-0.10%, Mn 0.45-0.80%, Si 0.10-0.30%, Al 0.010-0.050%, Cr 0.25-0.40%, Ti0.015 -0.035%, P≤0.012%, S≤0.0050%, N≤0.0060%, O≤0.0040%, Nb0.030-0.065%, V 0.015-0.045%, the balance is Fe and inevitable inclusions.

Among them, low carbon, very low phosphorus, ultra low sulfur and micro-alloying are the main design ideas, C: carbon is a stable austenite element, with the increase of carbon content, the anti-HIC sensitivity of pipeline steel increases, carbon content and carbon The increase in the equivalent weight will make the steel form the martensite structure which is most sensitive to hydrogen-induced bubbling during hot rolling. Therefore, reducing the carbon content and carbon equivalent can improve the HIC resistance of pipeline steel. Mn: Adding an appropriate amount of manganese to pipeline steel can improve the hardenability of steel and make up for the decrease in strength caused by low carbon. Manganese combines with sulfur to form MnS, which reduces the brittle transition temperature of the steel, while the segregation of manganese and phosphorus will cause the formation of HIC-sensitive band structures, so increasing the manganese content will lead to more band structures, thus making pipeline steel resistant to HIC increased sensitivity. Nb, V: The addition of microalloying elements such as niobium, vanadium and titanium to pipeline steel can effectively prevent the growth of austenite grains, refine the grains, and enhance the HIC resistance of pipeline steel.

The use of low carbon, very low phosphorus, ultra low sulfur and microalloyed designs can reduce segregation in the steel and improve the weldability of the steel. Low O and low S control can reduce inclusions in steel and improve toughness and plasticity.

The specific scheme of acid corrosion resistant pipeline steel X52MS is as follows:

After the refining treatment, calcification is carried out, the soft blowing time is appropriately increased, and the inclusions in the molten steel are strictly controlled; the whole process is protected by pouring. Heating system: ensure that the slab discharge temperature is greater than or equal to 1180°C; the finish rolling outlet temperature target is 820°C; the coiling temperature target is 550°C.

Example 1:

An acid corrosion resistant pipeline steel X52MS hot-rolled coil, comprising the following components by weight: C0.033%, Mn0.74%, Si 0.15%, Al 0.031%, Cr 0.32%, Ti 0.015%, P 0.008% , S 0.0008%, N0.0050%, O 0.0019%, Nb 0.044%, V 0.016%, the balance is Fe and inevitable inclusions.

A method for preparing an acid-corrosion-resistant pipeline steel X52MS hot-rolled coil, comprising the following process procedures: molten iron pretreatment→converter smelting→out-furnace refining→continuous casting→(2300 hot rolling) heating→rough rolling, finishing rolling→controlled cooling → Coiling → Finished Product Inspection → Delivery.

1. Steelmaking

1. Raw material process

The pretreatment S is 0.002% in the furnace, and the slag is scraped off; the refined scrap steel is used.

2. Ladle process

The red tank is required to receive steel; ensure the permeability and self-pouring of the ladle; the ladle is clean without residual steel and residue; the use of the ladle should consider feeding calcium.

3. Converter process

The converter pulls carbon at one time to avoid spot blowing; low carbon and low phosphorus ferromanganese, ferrosilicon, ferromolybdenum, and high chromium alloying are used for tapping; Als is 0.012%; the ladle N is required to be 23ppm, the slag is blocked and the steel is tapped, and the amount of slag entering the ladle is strictly controlled.

4. Refining process

It is required to maintain a slight positive pressure during the LF treatment process, strictly control the increase of N in LF, and the amount of N increase is required to be 5ppm; LF uses active lime and fluorite to make reducing slag with good fluidity, strictly controls the intensity of argon blowing, and tries to avoid the exposure of molten steel; After RH treatment, calcium treatment is carried out, the soft blowing time is increased, and the inclusions in molten steel are strictly controlled; gas samples are taken before and after refining for N and O content analysis.

5. Continuous casting process

Protective pouring was carried out throughout the process, and gas samples were taken to analyze N and O. Before pouring, use argon to purge the tundish. During the pouring process, no molten steel is exposed. Strictly control the intake of N at the nozzle, and control the increase of N to 3ppm. The slag in the tundish with high alkalinity is used to remove inclusions in the steel. The process is put into the function of soft pressing; the steel casting process maintains a constant pulling speed;

2. Hot rolling

1. Slab and heating area

The slab temperature was 1185°C. Control the furnace atmosphere of the heating furnace, reduce the formation of cast iron oxide scale, and ensure the uniform heating temperature.

2. Blank rolling, finishing rolling and coiling area

Do a good job in the load distribution of the finishing rolling model to ensure rolling stability; the finishing rolling outlet temperature target is 820 °C; the coiling temperature target is 550 °C. The cooling mode is a continuous cooling method in the front part of the cooling mode. Ensure precise control of final rolling and coiling temperature.

In order to ensure the anti-HIC and SSC corrosion performance requirements of the acid corrosion-resistant pipeline steel X52MS during use, the anti-HIC and anti-SSC performance tests were carried out. The HIC test solution is tested with A and B solutions respectively. The test standard is NACETM0284-2011. The test results are shown in the table:

The anti-SSC test adopts the NACE TM0177-1996 standard to carry out the A solution test. According to ASTM G39, the four-point bending sample is used. The test time is 720 hours. MPa, magnify 10 times in a low-power microscope to test the tensile surface of the sample, and the test results are shown in the table.

Example 2:

An acid corrosion-resistant pipeline steel X52MS hot-rolled coil comprises the following components by weight: C0.10%, Mn0.80%, Si 0.30%, Al 0.050%, Cr 0.32%, Ti 0.035%, P 0.005% , S 0.0010%, N0.0040%, O 0.0029%, Nb 0.065%, V 0.045%, the balance is Fe and inevitable inclusions.

The process procedure is the same as that of Example 1. In this example, the pretreatment S in the raw material process is 0.001%,

In the converter process, the Als of the ladle is 0.010%; the N of the ladle is required to be 25ppm, the slag is blocked for tapping, and the amount of slag entering the ladle is strictly controlled.

4. Refining process

It is required to maintain a slight positive pressure in the LF treatment process, strictly control the increase of N in LF, and the amount of N increase is required to be 6ppm; LF uses active lime and fluorite to make reducing slag with good fluidity, strictly controls the intensity of argon blowing, and tries to avoid bare molten steel; exposure; After RH treatment, calcium treatment is carried out, the soft blowing time is increased, and the inclusions in molten steel are strictly controlled; gas samples are taken before and after refining for N and O content analysis.

5. Continuous casting process

Protective pouring was carried out throughout the process, and gas samples were taken to analyze N and O. Before pouring, use argon to purge the tundish. During the pouring process, no molten steel is exposed. Strictly control the intake of N at the nozzle, and control the increase of N to 4ppm. The slag in the tundish with high alkalinity is used to remove the inclusions in the steel. The process is put into the soft pressing function; the steel casting process maintains a constant pulling speed; the superheat degree of the middle bag is 25℃.

2. Hot rolling

1. Slab and heating area

The slab temperature was 1190°C. Control the furnace atmosphere of the heating furnace, reduce the formation of cast iron oxide scale, and ensure the uniform heating temperature.

2. Blank rolling, finishing rolling and coiling area

Do a good job in the load distribution of the finishing rolling model to ensure rolling stability; the finishing rolling outlet temperature target is 820 °C; the coiling temperature target is 550 °C. The cooling mode is a continuous cooling method in the front part of the cooling mode. Ensure precise control of final rolling and coiling temperature.

Example 3

An acid corrosion-resistant pipeline steel X52MS hot-rolled coil comprises the following components by weight: C0.08%, Mn0.60%, Si 0.20%, Al 0.030%, Cr 0.28%, Ti 0.030%, P 0.002% , S 0.0030%, N0.0030%, O 0.0019%, Nb 0.045%, V 0.025%, the balance is Fe and inevitable inclusions.

The process procedure is the same as that of Example 1. In this example, the pretreatment S in the raw material process is 0.002%,

In the converter process, the Als of the ladle is 0.010%; the N of the ladle is required to be 28ppm, the slag is blocked for tapping, and the amount of slag entering the ladle is strictly controlled.

4. Refining process

It is required to maintain a slight positive pressure in the LF treatment process, strictly control the increase of N in LF, and the amount of N increase is required to be 8ppm; LF uses active lime and fluorite to make reducing slag with good fluidity, strictly controls the intensity of argon blowing, and tries to avoid the exposure of molten steel; After RH treatment, calcium treatment is carried out, the soft blowing time is increased, and the inclusions in molten steel are strictly controlled; gas samples are taken before and after refining for N and O content analysis.

5. Continuous casting process

Protective pouring was carried out throughout the process, and gas samples were taken to analyze N and O. Before pouring, use argon to purge the tundish. During the pouring process, no molten steel is exposed. Strictly control the intake of N at the nozzle, and control the increase of N to 2ppm. The slag in the tundish with high alkalinity is used to remove the inclusions in the steel. The process is put into the function of soft pressing; the steel casting process maintains a constant pulling speed; the superheat degree of the middle bag is 18 ℃.

2. Hot rolling

1. Slab and heating area

The slab temperature was 1195°C. Control the furnace atmosphere of the heating furnace, reduce the formation of cast iron oxide scale, and ensure the uniform heating temperature.

2. Blank rolling, finishing rolling and coiling area

Do a good job in the load distribution of the finishing rolling model to ensure rolling stability; the finishing rolling outlet temperature target is 820 °C; the coiling temperature target is 550 °C. The cooling mode is a continuous cooling method in the front part of the cooling mode. Ensure precise control of final rolling and coiling temperature.

The acid corrosion-resistant pipeline steel X52MS produced by this process has various mechanical properties that meet the requirements and has excellent corrosion resistance to HIC and SSCC. The product is widely used and has good economic benefits.

The above-disclosed preferred embodiments of the present invention are provided only to help illustrate the present invention. The preferred embodiments do not exhaust all the details, nor do they limit the invention to only the described embodiments. Obviously, many modifications and variations are possible in light of the content of this specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is to be limited only by the claims and their full scope and equivalents.

Claims (7)

1. An acid corrosion resistant pipeline steel X52MS hot rolled coil is characterized by comprising the following components in percentage by weight: 0.03-0.10% of C, 0.45-0.80% of Mn, 0.10-0.30% of Si, 0.010-0.050% of Al, 0.25-0.40% of Cr, 0.015-0.035% of Tis, less than or equal to 0.012% of P, less than or equal to 0.0050% of S, less than or equal to 0.0060% of N, less than or equal to 0.0040% of O, 0.030-0.065% of Nb, 0.015-0.045% of V, and the balance of Fe and inevitable impurities.

2. A preparation method of an acid corrosion resistant pipeline steel X52MS hot-rolled coil is characterized by comprising the steps of carrying out calcification after refining treatment, properly increasing soft blowing time and strictly controlling inclusions in molten steel; the whole process adopts protective pouring. A heating system: ensuring that the tapping temperature of the plate blank is more than or equal to 1180 ℃; a finish rolling outlet temperature target of 820 ℃; the coiling temperature target is 550 ℃.

3. The method for preparing the acid corrosion resistant pipeline steel X52MS hot-rolled sheet according to claim 2, comprising the following steps: molten iron pretreatment → converter smelting → external refining → continuous casting → (2300 hot rolling) heating → rough rolling, finish rolling → controlled cooling → coiling.

4. The method for preparing the acid corrosion resistant pipeline steel X52MS hot rolled coil according to claim 3, wherein S in the molten iron pretreatment is less than or equal to 0.005%.

5. The method for preparing the acid corrosion resistant pipeline steel X52MS hot rolled coil according to claim 3, wherein in the converter smelting process, the content of steel ladle Als is controlled to be 0.005-0.015%; the N content of the steel ladle is required to be less than or equal to 30 ppm.

6. The method for preparing the acid corrosion resistant pipeline steel X52MS hot-rolled sheet according to claim 3, wherein in the external refining process, the N increase is less than or equal to 10 ppm.

7. The method for preparing the acid corrosion resistant pipeline steel X52MS hot-rolled coil according to claim 3, wherein in the continuous casting process, the water mouth is controlled to absorb N, and the increase of N is controlled to be less than or equal to 5 ppm; high-alkalinity tundish slag is adopted, and the tundish is controlled according to the superheat degree of less than or equal to 25 ℃.