CN111411198A - Method for increasing nitrogen of nitrogen-containing steel for wind power flange by utilizing RH vacuum degassing system - Google Patents
Method for increasing nitrogen of nitrogen-containing steel for wind power flange by utilizing RH vacuum degassing system Download PDFInfo
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- CN111411198A CN111411198A CN202010431183.8A CN202010431183A CN111411198A CN 111411198 A CN111411198 A CN 111411198A CN 202010431183 A CN202010431183 A CN 202010431183A CN 111411198 A CN111411198 A CN 111411198A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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Abstract
The invention discloses a method for increasing nitrogen in nitrogen-containing steel for a wind power flange by using an RH vacuum degassing system, and belongs to the technical field of metallurgy. In order to solve the problems of low nitrogen increasing efficiency, inaccurate nitrogen content control and poor dehydrogenation effect of the existing nitrogen increasing method, the invention provides a method for increasing nitrogen of nitrogen-containing steel for a wind power flange by using an RH vacuum degassing system, wherein an argon-nitrogen pipeline of the RH vacuum degassing system is switched, nitrogen is used as lifting gas, the stable and rapid nitrogen increase is realized by increasing nitrogen at an RH vacuum level and directly leading nitrogen to the bottom after the vacuum is broken, and the nitrogen content is accurately controlled by supplementing nitrogen through nitrogen soft blowing; argon is used for soft blowing to ensure the effect of dehydrogenation gas, and the hydrogen content is controlled to be less than or equal to 1.0 ppm. According to the invention, the switching between nitrogen and argon is flexibly adjusted, the total vacuum and soft blowing time is controlled within 45 minutes, the smooth production can be ensured, the nitrogen content of the nitrogen-containing steel for the wind power flange is controlled within an internal control range, and the stable control of the performance of steel material products is ensured.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for increasing nitrogen of nitrogen-containing steel for a wind power flange by using an RH vacuum degassing system.
Background
Generally, nitrogen is a harmful element, which increases the risk of aging embrittlement of steel materials. However, for nitrogen-containing steel materials such as wind power flange steel, V, Nb alloy is added into the steel, and stable nitrides VN and NbN can be formed when nitrogen is added, and the nitrides are dispersed in grain boundaries to generate precipitation strengthening effect, so that crystal grains are refined, and the toughness of the steel is improved. Therefore, the N content of the steel for the wind power flange is 70-110ppm, and the effect of improving the toughness of the finished flange part can be achieved.
The nitrogen content in steel is controlled, nitrogen is increased by adding chromium nitride or manganese nitride, the nitrogen increasing method has the advantages of controllable nitrogen content range and simple operation, and has the following defects: firstly, more impurities exist in the nitriding alloy, which influences the purity of molten steel; secondly, in the process of feeding the alloy wires, molten steel is easy to boil and contacts with air to form secondary oxidation, so that the unqualified risk of B-type and D-type inclusions is increased; thirdly, when the wire feeder breaks down suddenly, the production rhythm is influenced, and the risk of breaking the casting times is easily caused; fourthly, after the nitralloy is added, the nitrogen content change in the soft blowing process is uncontrollable, and the risk is brought to the component stability control; fifthly, the alloy cost is high, the recovery rate is low, and the production and manufacturing cost is increased.
The invention patent application with the patent publication number of CN105154628A, namely RH dehydrogenation and nitrogen increasing process of nitrogen-containing steel, mentions that nitrogen is blown in the whole RH dehydrogenation process, and the nitrogen increasing effect can be ensured and the H content can be ensured to be below 2.0ppm by controlling the nitrogen circulation flow and the pressure. The method has the fastest nitrogen increasing speed of 2-3ppm, needs 28 minutes only in total vacuum time, is slow in nitrogen increasing speed, controls the hydrogen content within 1.3-1.8 ppm, and can only meet the requirements of common steel grades. The wind power flange continuous casting round billet has larger specification and higher requirement on internal control of hydrogen content, and the hydrogen content needs to be less than or equal to 1.0ppm, so the soft blowing time needs to be controlled to be more than 20 minutes in order to improve the purity of molten steel. In order to ensure that the production rhythm is smooth, the total vacuum time of the nitrogen increasing process must be controlled within 20 minutes, and the stable and accurate nitrogen increasing can not be realized according to the existing nitrogen increasing method. Therefore, the whole-course nitrogen-blowing nitrogen-increasing method cannot meet the actual production requirement of the wind power flange, and a practical and effective novel nitrogen-increasing mode needs to be developed.
Disclosure of Invention
The invention provides a method for increasing nitrogen of nitrogen-containing steel for a wind power flange by using an RH vacuum degassing system, aiming at solving the problems of low nitrogen increasing efficiency, inaccurate nitrogen content control and poor dehydrogenation effect of the existing nitrogen increasing method in the refining process of the nitrogen-containing steel for the wind power flange.
The technical scheme of the invention is as follows:
a method for increasing nitrogen of nitrogen-containing steel for a wind power flange by utilizing an RH vacuum degassing system comprises the following steps:
step one, a ladle reaches an RH vacuum position, argon with a certain circulation flow is used as lifting gas, a vacuum pump is started, vacuumizing is performed, a certain vacuum degree is kept for at least 10min, then a low-pressure nitrogen pipeline is adopted, argon is switched into nitrogen, the nitrogen is kept for 5min under a certain nitrogen pressure and circulation flow until the air is broken, sampling and hydrogen determination are performed after the air is broken, and argon is adopted for soft blowing in the process of inspecting the broken air sample;
step two, performing secondary nitrogen content regulation and control according to the nitrogen content result of the blank breaking sampling in the step one, switching argon in the high-pressure pipeline into nitrogen, increasing nitrogen by adopting direct nitrogen at the bottom, sampling after nitrogen increase is finished, and simultaneously switching the nitrogen into argon for soft blowing; soft blowing for at least 10min after the nitrogen content of the sampling result reaches the standard;
and step three, if the nitrogen content of the sample after the nitrogen increase is finished is still lower than the target value, switching the argon gas into the nitrogen gas again for soft blowing nitrogen increase, and switching the argon gas into the nitrogen gas for soft blowing for at least 10min after the nitrogen increase is finished.
Further, the flow rate of the argon gas ring in the first step is 1800-2000N L/min.
Further, in the first step, the vacuum degree is 67 MPa.
Further, in the first step, the nitrogen pressure is 0.6-0.8 kg, and the nitrogen circulation flow is 1800-2000N L/min.
Further, the pressure of the direct nitrogen at the bottom of the high-pressure pipeline in the second step is 16-20 kg.
Further, the nitrogen increasing speed of the bottom direct nitrogen in the second step is 12-18 ppm/min.
Further, the flow rate of nitrogen for soft nitrogen increase in the third step is 100-300N L/min.
And further, in the third step, the nitrogen increasing speed of the soft blowing nitrogen increasing is 2-5 ppm/min.
Further, the argon flow rate of the argon soft blowing in the first step, the second step and the third step is 80-120N L/min.
The invention has the beneficial effects that:
according to the method for increasing nitrogen in the nitrogen-containing steel for the wind power flange, provided by the invention, the argon-nitrogen pipeline switching of the RH vacuum degassing system is utilized, the nitrogen is increased through the RH vacuum position, the nitrogen is directly communicated from the bottom after the air is broken, the stable and rapid nitrogen increase is realized, the nitrogen increase efficiency is improved, and the nitrogen content is accurately controlled through the nitrogen soft blowing supplement nitrogen increase; and nitrogen is increased, argon is used for soft blowing to ensure the effect of dehydrogenation gas, and the content of hydrogen is controlled to be less than or equal to 1.0 ppm.
According to the nitrogen increasing method, the nitrogen content is regulated and controlled, the effect of dehydrogenation gas is ensured, meanwhile, the total vacuum and soft blowing time is controlled within 45 minutes by flexibly adjusting the switching of nitrogen and argon, the smooth production can be ensured, the nitrogen content of the nitrogen-containing steel for the wind power flange is controlled within an internal control range, and the stable control of the performance of steel material products is ensured.
The nitrogen increasing method provided by the invention saves the risk of secondary pollution of molten steel caused by adding a nitrided alloy wire, improves the purity of the molten steel, improves the production efficiency and the quality of the molten steel, reduces the production cost and realizes cost reduction and efficiency improvement.
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Example 1
The embodiment provides a method for increasing nitrogen by using an RH vacuum degassing system when producing steel S355N L (Q355NE) for wind power flanges, which comprises the following steps:
the nitrogen content of the steel ladle leaving the L F position was 59ppm, and the target nitrogen content was 90 ppm.
Step one, a steel ladle reaches an RH vacuum position, argon with the circulation flow of 2000N L/min is used as lifting gas, a vacuum pump is started, the steel ladle is vacuumized to 67MPa and kept for 10min, a low-pressure nitrogen pipeline is adopted, the argon is switched into nitrogen, the steel ladle is kept for 5min under the nitrogen pressure of 0.8kg and the nitrogen circulation flow of 2000N L/min until the steel ladle is broken, the total vacuum time is 15min, sampling and hydrogen determination are carried out after the steel ladle is broken, and the content of hydrogen is measured to be 0.85ppm, wherein in the process of inspecting the broken hollow sample, the argon is adopted to carry out soft blowing at the flow of 120N L/min;
when nitrogen is adopted as lifting gas at a vacuum position, a larger amount of nitrogen removal can be caused while the nitrogen content is increased, the nitrogen removal is generally 20-30 ppm, so that the nitrogen content after the air is broken is lower, and the secondary regulation and control of the nitrogen content can be rapidly carried out by adopting a mode of directly leading nitrogen from the bottom.
Step two, breaking the air, sampling and switching the argon in the high-pressure pipeline into nitrogen with the nitrogen content of 60ppm, increasing the nitrogen by adopting the bottom direct nitrogen, controlling the pressure of the bottom direct nitrogen of the high-pressure pipeline to be 20kg, directly introducing the nitrogen into the furnace for 2min, sampling after nitrogen increase is finished, and simultaneously switching the nitrogen into the argon to perform soft blowing at the flow rate of 120N L/min;
and step three, after the nitrogen in the step two is directly communicated, the content of the sampled nitrogen is 86ppm, the nitrogen increasing speed is 13ppm/min, the sum of the argon soft blowing time in the step one and the argon soft blowing time in the step two is 5min, at the moment, the argon is switched to the nitrogen for soft blowing and nitrogen increasing, the nitrogen flow for soft blowing and nitrogen increasing is 300N L/min, the nitrogen in the furnace is soft blown for 3min, the nitrogen increasing speed is about 3ppm/min, after the nitrogen increasing is finished, the argon is switched to be soft blown at the flow of 120N L/min so as to improve the purity of molten steel, the nitrogen bubbles are ensured to fully float upwards, the argon is soft blown to a continuous casting upper stage for 12min, and the sampled nitrogen.
Example 2
The embodiment provides a method for increasing nitrogen by using an RH vacuum degassing system when producing steel S355N L (Q355NE) for wind power flanges, which comprises the following steps:
the nitrogen content of the ladle leaving the L F position was 54ppm and the target nitrogen content was 90 ppm.
Step one, a steel ladle reaches an RH vacuum position, argon with the circulation flow of 1800N L/min is used as lifting gas, a vacuum pump is started, the steel ladle is vacuumized to 67MPa and kept for 12min, a low-pressure nitrogen pipeline is adopted, the argon is switched into nitrogen, the steel ladle is kept for 5min to be broken under the nitrogen pressure of 0.6kg and the nitrogen circulation flow of 1800N L/min, the total vacuum time is 17min, sampling and hydrogen determination are carried out after breaking, and the hydrogen content is measured to be 0.78ppm, wherein in the process of inspecting broken samples, the argon is adopted to carry out soft blowing at the flow of 80N L/min;
step two, breaking the air, sampling, changing the nitrogen content into 59ppm, switching argon in a high-pressure pipeline into nitrogen, increasing the nitrogen by adopting the bottom direct nitrogen, ensuring the pressure of the bottom direct nitrogen of the high-pressure pipeline to be 16kg, directly introducing the nitrogen into the furnace for 2min, sampling after nitrogen increase is finished, and simultaneously switching the nitrogen into the argon to perform soft blowing at the flow rate of 80N L/min;
and step three, after the nitrogen in the step two is directly communicated, the content of the sampled nitrogen is 87ppm, the nitrogen increasing speed is 14ppm/min, the sum of the soft blowing time of the argon in the step one and the step two is 6min, at the moment, the argon is switched to the nitrogen again for soft blowing for nitrogen increasing, the nitrogen flow rate of the soft blowing nitrogen increasing is 100N L/min, the nitrogen in the furnace is soft blown for 2min, the nitrogen increasing speed is 2ppm/min, after the nitrogen increasing is finished, the argon is switched to be soft blown at the flow rate of 80N L/min so as to improve the purity of the molten steel, the nitrogen bubbles are ensured to fully float, the argon is soft blown to a continuous casting upper stage for 12min, and the content of the sampled nitrogen.
Example 3
The embodiment provides a method for increasing nitrogen by using an RH vacuum degassing system when producing steel S355N L (Q355NE) for wind power flanges, which comprises the following steps:
the nitrogen content of the steel ladle leaving the L F position was 60ppm, and the target nitrogen content was 90 ppm.
Step one, a ladle reaches an RH vacuum position, argon with the circulation flow of 1900N L/min is used as lifting gas, a vacuum pump is started, the ladle is vacuumized to 67MPa and kept for 10min, a low-pressure nitrogen pipeline is adopted, the argon is switched into nitrogen, the ladle is kept for 5min under the nitrogen pressure of 0.7kg and the circulation flow of 1900N L/min until the ladle is broken, the total vacuum time is 15min, sampling and hydrogen determination are carried out after the ladle is broken, and the content of hydrogen is measured to be 0.80ppm, wherein in the process of inspecting the broken sample, the argon is adopted to carry out soft blowing at the flow of 100N L/min;
step two, breaking the air, sampling and switching the content of nitrogen to 64ppm, adding nitrogen into the argon in the high-pressure pipeline by adopting the bottom direct nitrogen, enabling the pressure of the bottom direct nitrogen in the high-pressure pipeline to be 18kg, enabling the nitrogen to be directly introduced into the furnace for 3min, sampling after nitrogen addition is finished, and simultaneously switching the nitrogen to the argon to perform soft blowing at the flow rate of 100N L/min;
and step three, after the nitrogen in the step two is directly introduced, the content of the sampled nitrogen is 92ppm, the nitrogen increasing speed is about 14ppm/min, the sum of the argon soft blowing time in the step one and the argon soft blowing time in the step two is 5min, and because the nitrogen content reaches over a target value of 90ppm, after the argon soft blowing is directly adopted for 15min, the nitrogen content is 95ppm through sampling inspection, and the ladle is hung to a continuous casting station for casting.
Claims (9)
1. A method for increasing nitrogen of nitrogen-containing steel for a wind power flange by utilizing an RH vacuum degassing system is characterized by comprising the following steps:
step one, a ladle reaches an RH vacuum position, argon with a certain circulation flow is used as lifting gas, a vacuum pump is started, vacuumizing is performed, a certain vacuum degree is kept for at least 10min, then a low-pressure nitrogen pipeline is adopted, argon is switched into nitrogen, the nitrogen is kept for 5min under a certain nitrogen pressure and circulation flow until the air is broken, sampling and hydrogen determination are performed after the air is broken, and argon is adopted for soft blowing in the process of inspecting the broken air sample;
step two, performing secondary nitrogen content regulation and control according to the nitrogen content result of the blank breaking sampling in the step one, switching argon in the high-pressure pipeline into nitrogen, increasing nitrogen by adopting direct nitrogen at the bottom, sampling after nitrogen increase is finished, and simultaneously switching the nitrogen into argon for soft blowing; soft blowing for at least 10min after the nitrogen content of the sampling result reaches the standard;
and step three, if the nitrogen content of the sample after the nitrogen increase is finished is still lower than the target value, switching the argon gas into the nitrogen gas again for soft blowing nitrogen increase, and switching the argon gas into the nitrogen gas for soft blowing for at least 10min after the nitrogen increase is finished.
2. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 1, wherein the argon gas circulation rate in the step one is 1800-2000N L/min.
3. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 2, wherein the vacuum degree in the step one is 67 MPa.
4. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 3, wherein the nitrogen pressure in the step one is 0.6-0.8 kg, and the nitrogen circulation rate is 1800-2000N L/min.
5. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 4, wherein the pressure of the nitrogen directly introduced to the bottom of the high-pressure pipeline in the second step is 16-20 kg.
6. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 5, wherein the nitrogen increasing speed of the bottom direct nitrogen in the second step is 12-18 ppm/min.
7. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 6, wherein nitrogen flow rate of the soft blowing nitrogen increase in the third step is 100-300N L/min.
8. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 7, wherein the nitrogen increasing speed of the soft blowing nitrogen increase in the third step is 2-5 ppm/min.
9. The method for increasing nitrogen of the nitrogen-containing steel for the wind power flange by using the RH vacuum degassing system according to claim 8, wherein the argon flow for soft blowing of argon in the first step, the second step and the third step is 80-120N L/min.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112553411A (en) * | 2020-12-04 | 2021-03-26 | 山东钢铁集团日照有限公司 | Method for trace accurate nitrogen increase of cold-rolled deep-drawing steel through RH vacuum decarburization |
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| CN102433503A (en) * | 2011-12-16 | 2012-05-02 | 江阴同庆机械制造有限公司 | Wind power flange alloy steel and preparation technology of parts thereof |
| CN104726646A (en) * | 2015-04-03 | 2015-06-24 | 攀钢集团成都钢钒有限公司 | Method for controlling nitrogen content in high temperature alloy steel P91 |
| CN104962698A (en) * | 2015-07-07 | 2015-10-07 | 新余钢铁集团有限公司 | Accurate control method for nitrogen content of oriented electrical steel |
| CN106591541A (en) * | 2016-12-23 | 2017-04-26 | 江苏沙钢集团淮钢特钢股份有限公司 | Dehydrating nitrogen increasing control method in RH vacuum treatment process |
| JP2018131651A (en) * | 2017-02-15 | 2018-08-23 | 新日鐵住金株式会社 | Method for melting high-nitrogen low-oxygen steel |
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- 2020-05-20 CN CN202010431183.8A patent/CN111411198A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102433503A (en) * | 2011-12-16 | 2012-05-02 | 江阴同庆机械制造有限公司 | Wind power flange alloy steel and preparation technology of parts thereof |
| CN104726646A (en) * | 2015-04-03 | 2015-06-24 | 攀钢集团成都钢钒有限公司 | Method for controlling nitrogen content in high temperature alloy steel P91 |
| CN104962698A (en) * | 2015-07-07 | 2015-10-07 | 新余钢铁集团有限公司 | Accurate control method for nitrogen content of oriented electrical steel |
| CN106591541A (en) * | 2016-12-23 | 2017-04-26 | 江苏沙钢集团淮钢特钢股份有限公司 | Dehydrating nitrogen increasing control method in RH vacuum treatment process |
| JP2018131651A (en) * | 2017-02-15 | 2018-08-23 | 新日鐵住金株式会社 | Method for melting high-nitrogen low-oxygen steel |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112553411A (en) * | 2020-12-04 | 2021-03-26 | 山东钢铁集团日照有限公司 | Method for trace accurate nitrogen increase of cold-rolled deep-drawing steel through RH vacuum decarburization |
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Application publication date: 20200714 |