CN115717222A - Production method of steel for V-N alloying A350LF6 flange - Google Patents
Production method of steel for V-N alloying A350LF6 flange Download PDFInfo
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- CN115717222A CN115717222A CN202211438257.6A CN202211438257A CN115717222A CN 115717222 A CN115717222 A CN 115717222A CN 202211438257 A CN202211438257 A CN 202211438257A CN 115717222 A CN115717222 A CN 115717222A
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Abstract
The invention discloses a production method of a V-N alloying A350LF6 flange steel, which comprises the following chemical components in percentage by mass: c:0.15 to 0.17%, si:0.15 to 0.25%, mn:1.20 to 1.30%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, als:0.035 to 0.050%, ca:0.0015 to 0.0030%, V:0.080 to 0.090%, N: 110-150 ppm, the balance being Fe and inevitable impurities; the preparation process comprises the following steps: the method comprises the steps of molten iron pretreatment, converter top and bottom combined blowing smelting, LF refining, RH refining, casting by a casting machine and slab stacking and slow cooling. The invention adopts VN alloying, fully exerts VN precipitation strengthening effect, refines crystal grains, ensures good low-temperature toughness of the product, has lower alloy cost and can be well popularized and applied.
Description
Technical Field
The invention relates to the field of metallurgical materials, in particular to a production method of steel for a V-N alloying A350LF6 flange.
Background
The flange is one of the main materials selected when the industrial pipeline in the petrochemical device is adopted, and is often used at the connecting part of the pipeline, a valve, equipment and the like. With the increase of the number of petrochemical industry projects, part of equipment and pipelines in many devices are stored or transported to operate under high-pressure and low-temperature working conditions, the materials of the equipment and the pipelines are tested under low-temperature working conditions for a long time, and the materials are required to have good low-temperature toughness in order to ensure the safety and reliability of equipment and process pipeline systems, so that high requirements are put forward on the performance indexes of raw materials.
A350LF6 is a steel grade in ASTM A350/A350M standard, is required to have good low-temperature performance, and plays an important role in connecting pipeline systems and equipment in petrochemical industry in high-pressure and low-temperature operation. A350LF6 has high requirements on low-temperature toughness, in order to ensure the low-temperature toughness, multiple alloy elements need to be added, so that the alloy cost is high, A350LF6 provided in the analysis of the net cracks on the surface of the A350LF6 continuous casting billet in the document A350LF6 is alloyed by V, cu, so that the alloy cost is high, and meanwhile, cu elements are easily enriched at austenite crystal boundaries at high temperature, so that the net cracks along the crystal are generated on the surface of the continuous casting billet.
Disclosure of Invention
The invention aims to provide a method for producing steel for a V-N alloyed A350LF6 flange, VN alloying is adopted, VN precipitation strengthening effect is fully exerted, crystal grains are refined, good low-temperature toughness of products is guaranteed, meanwhile, the alloy cost is low, and the method can be well popularized and applied.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention relates to a production method of a V-N alloying A350LF6 flange steel, which comprises the following chemical components in percentage by mass: c:0.15 to 0.17%, si:0.15 to 0.25%, mn:1.20 to 1.30%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, als:0.035 to 0.050%, ca:0.0015 to 0.0030%, V:0.080 to 0.090%, N: 110-150 ppm, the balance being Fe and inevitable impurities;
the preparation process comprises the following steps: the method comprises the following steps of molten iron pretreatment, converter top and bottom combined blowing smelting, LF refining, RH refining, casting by a casting machine, and slab stacking and slow cooling;
the molten iron pretreatment process comprises the following steps: adopting KR method molten iron pretreatment, wherein the slag-off rate after molten iron desulphurization is more than or equal to 98 percent, the sulfur content of the molten iron entering a converter is less than or equal to 0.002 percent, and the temperature of the molten iron is more than or equal to 1280 ℃;
the converter top-bottom combined blowing smelting process comprises the following steps: when smelting in a converter, adopting self-produced low-sulfur waste steel, adding active lime and dolomite for slagging and dephosphorizing, wherein the P content of the steel is less than or equal to 0.007 percent, the end point carbon of the converter is required to be hit at one time, the C content is less than or equal to 0.11 percent, the steel tapping temperature is more than or equal to 1620 ℃, adding high-quality ferrosilicon and ferromanganese in the steel tapping process, adding aluminum for deoxidation after steel tapping, and adopting automatic slag removal detection;
an LF refining process: adding a proper amount of slagging agent in the refining process to carry out slagging and desulfurization to form white slag, controlling the alkalinity to be more than 4.0, controlling the S content after desulfurization to be less than or equal to 0.001%, and adding VN alloy to a target value;
an RH refining process: the RH vacuum treatment time is more than or equal to 15min, the circulation argon flow is regulated in the RH vacuum treatment process, the pure degassing time is more than or equal to 5min, calcium treatment is carried out after the vacuum treatment, the gas flow is regulated to ensure that the molten steel is in a soft blowing state, the soft blowing time is not less than 10min, and the inclusions are fully denatured and float;
the casting process of the casting machine comprises the following steps: the whole process is protected to pour when the slab is continuously cast, the superheat degree is controlled to be 15-30 ℃, the stable drawing speed is kept, the drawing speed is 1.0-1.2m/min, and the technologies such as dynamic light pressing are adopted to reduce the center segregation of the continuous casting slab;
slab stacking slow cooling process: and (4) after the plate blank is sized, inserting the plate blank into a blank warehouse, stacking and slowly cooling the plate blank to room temperature, wherein the slow cooling time is more than 48h.
Further, the chemical components of the flange steel are calculated according to mass percent as follows: c:0.16%, si:0.22%, mn:1.25%, P:0.008%, S:0.0008%, als:0.045%, ca:0.0025%, V:0.085%, N:120ppm, the balance being Fe and inevitable impurities.
Further, the chemical components of the flange steel are calculated according to mass percent as follows: c:0.163%, si:0.21%, mn:1.22%, P:0.006%, S:0.0005%, als:0.042%, ca:0.0023%, V:0.086%, N:142ppm, and the balance of Fe and inevitable impurities.
Further, the chemical components of the flange steel are calculated according to mass percent as follows: c:0.156%, si:0.18%, mn:1.26%, P:0.008%, S:0.0011%, als:0.040%, ca:0.0020%, V:0.086%, N:135ppm, the balance Fe and inevitable impurities.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention adopts VN alloying, fully exerts VN precipitation strengthening effect, refines crystal grains, ensures good low-temperature toughness of products, has low production cost and can be well popularized and applied. The material is mainly used for connecting flange parts such as pipelines, pipe fittings and the like in the field of petrochemical industry.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Examples 1 to 3 are the process steps adopted in the method for producing the steel for the V-N alloying A350LF6 flange.
The process parameters of each example are shown in table 1; the chemical compositions of the cast slabs are shown in Table 2, and the properties of the cast slabs after forging heat treatment are shown in Table 3.
TABLE 1 Process parameters
TABLE 2 casting blank chemical composition (wt%)
| Examples | C | Si | Mn | P | S | Als | V | Ca | N/ppm |
| 1 | 0.160 | 0.22 | 1.25 | 0.008 | 0.0008 | 0.045 | 0.085 | 0.0025 | 120 |
| 2 | 0.163 | 0.21 | 1.22 | 0.006 | 0.0005 | 0.042 | 0.086 | 0.0023 | 142 |
| 3 | 0.156 | 0.18 | 1.26 | 0.008 | 0.0011 | 0.040 | 0.086 | 0.0020 | 135 |
TABLE 3 properties of the cast blanks after forging Heat treatment
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (4)
1. A production method of steel for a V-N alloying A350LF6 flange is characterized by comprising the following steps: the flange steel comprises the following chemical components in percentage by mass: c:0.15 to 0.17%, si:0.15 to 0.25%, mn:1.20 to 1.30%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, als:0.035 to 0.050% by weight, ca:0.0015 to 0.0030%, V:0.080 to 0.090%, N: 110-150 ppm, the balance being Fe and inevitable impurities;
the preparation process comprises the following steps: the method comprises the following steps of molten iron pretreatment, converter top and bottom combined blowing smelting, LF refining, RH refining, casting by a casting machine, and slab stacking and slow cooling;
the molten iron pretreatment process comprises the following steps: adopting KR method molten iron pretreatment, wherein the slagging rate after molten iron desulfurization is more than or equal to 98 percent, the sulfur content of the molten iron entering a converter is less than or equal to 0.002 percent, and the temperature of the molten iron is more than or equal to 1280 ℃;
the converter top-bottom combined blowing smelting process comprises the following steps: when smelting in a converter, adopting self-produced low-sulfur waste steel, adding active lime and dolomite for slagging and dephosphorizing, wherein the P content of the steel is less than or equal to 0.007 percent, the end point carbon of the converter is required to be hit at one time, the C content is less than or equal to 0.11 percent, the steel tapping temperature is more than or equal to 1620 ℃, adding high-quality ferrosilicon and ferromanganese in the steel tapping process, adding aluminum for deoxidation after steel tapping, and adopting automatic slag removal detection;
an LF refining process: adding a proper amount of slagging agent in the refining process to carry out slagging and desulfurization to form white slag, controlling the alkalinity to be more than 4.0, controlling the S content after desulfurization to be less than or equal to 0.001%, and adding VN alloy to a target value;
RH refining process: the RH vacuum treatment time is more than or equal to 15min, the circulation argon flow is adjusted in the RH vacuum treatment process, the pure degassing time is more than or equal to 5min, calcium treatment is carried out after the vacuum treatment, the gas flow is adjusted to enable the molten steel to be in a soft blowing state, the soft blowing time is not less than 10min, and inclusions are fully denatured and float;
the casting process of the casting machine comprises the following steps: the whole process is protected to pour when the slab is continuously cast, the superheat degree is controlled to be 15-30 ℃, the stable drawing speed is kept, the drawing speed is 1.0-1.2m/min, and the technologies such as dynamic light pressing are adopted to reduce the center segregation of the continuous casting slab;
slab stacking slow cooling process: and (4) after the plate blank is sized, inserting the plate blank into a blank warehouse, stacking and slowly cooling the plate blank to room temperature, wherein the slow cooling time is more than 48h.
2. The method for producing a steel for a V-N alloyed a350LF6 flange according to claim 1, characterized in that: the flange steel comprises the following chemical components in percentage by mass: c:0.16%, si:0.22%, mn:1.25%, P:0.008%, S:0.0008%, als:0.045%, ca:0.0025%, V:0.085%, N:120ppm, and the balance of Fe and inevitable impurities.
3. The method for producing a steel for a V-N alloyed a350LF6 flange according to claim 1, characterized in that: the flange steel comprises the following chemical components in percentage by mass: c:0.163%, si:0.21%, mn:1.22%, P:0.006%, S:0.0005%, als:0.042%, ca:0.0023%, V:0.086%, N:142ppm, and the balance of Fe and inevitable impurities.
4. The method for producing a steel for a V-N alloyed a350LF6 flange according to claim 1, characterized in that: the flange steel comprises the following chemical components in percentage by mass: c:0.156%, si:0.18%, mn:1.26%, P:0.008%, S:0.0011%, als:0.040%, ca:0.0020%, V:0.086%, N:135ppm, the balance Fe and inevitable impurities.
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| WO2022160526A1 (en) * | 2021-02-01 | 2022-08-04 | 南京钢铁股份有限公司 | Weather-resistant bridge steel and smelting method therefor |
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