A refining method for improving the RH dehydrogenation rate of heavy rail steel

Abstract

The application provides a refining method for improving RH dehydrogenation rate of heavy rail steel, which comprises the following steps: step one, drying alloy and auxiliary materials used in the RH refining process; step two, when the ladle reaches the RH station, temperature measurement and sampling are performed, and the composition is analyzed; step three, after the RH insertion tube enters the molten steel, normal treatment operation is started, and vacuum treatment is performed; step four, after the vacuum treatment is completed, alloying is performed according to the composition of the molten steel, and after the alloying, argon bottom blowing is performed on the molten steel; step five, after the RH treatment is completed, soft argon blowing and stirring are performed on the molten steel, and after the soft argon blowing is completed, the heavy rail steel is prepared. The application can greatly improve the dehydrogenation effect of the molten steel, improve the uniformity of the steel, and reduce the quality defects of the steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgical refining, in particular, especially relates to a refining method for improving RH dehydrogenation rate of heavy rail steel. BACKGROUND

[0002] RH refining is a kind of liquid steel vacuum treatment technology, which has a series of advantages such as short treatment cycle, large production capacity, good refining effect and easy operation, and has been widely used in steel production. RH refining technology has the characteristics of multifunctionalization, in addition to the function of degassing, it also has the functions of vacuum decarburization, desulfurization, composition fine adjustment and molten steel heat compensation.

[0003] The solubility of hydrogen in solid steel is very small. During the solidification and cooling process of molten steel, it will be precipitated together with CO, N2 and other gases to form subcutaneous bubbles, center porosity and shrinkage holes, etc., resulting in defects such as cracking, white spots and layered fracture of steel, which will reduce the mechanical properties of steel, and reduce the strength limit, section shrinkage rate, elongation and impact toughness of steel, which is extremely harmful to steel.

[0004] At present, in the production of heavy rail steel, RH vacuum refining is generally used for dehydrogenation treatment, but under the existing system, the dehydrogenation rate is only 75%-82%, and the hydrogen content is still high [H] > 1 ppm, which leads to the decline of heavy rail steel quality.

[0005] CN200910082517.9: A RH vacuum treatment process for dehydrogenation of molten steel, belongs to the technical field of steelmaking. The process is: the alloy and raw and auxiliary materials used for RH furnace are baked; the alloy composition is adjusted to the internal control range before the molten steel enters the RH furnace, to minimize the composition adjustment during the RH vacuum treatment; the RH vacuum chamber is baked before the vacuum treatment of molten steel, to ensure that the temperature of the refractory material in the vacuum chamber is 1100-1200℃; to ensure that the oxygen activity of molten steel to RH furnace is ≤8ppm; to control the flow of argon at 8-12NL / (min·t); to control the time from the start of vacuum treatment to deep vacuum at 2.5-4min, and to maintain the high vacuum degree in the vacuum chamber at 10-100Pa; to control the RH vacuum treatment time at 15-30min, including the deep vacuum treatment time control at 8-15min; to add dry heat preservative to the exposed molten steel surface at the end of RH vacuum treatment, to prevent the molten steel from absorbing gas. The advantages are: the hydrogen content in the steel is removed to below 1.1ppm, and the RH dehydrogenation rate can reach 81%-86%. This patent reduces the entry of hydrogen element into the molten steel by measures such as vacuum chamber baking and adding dry heat preservative to the exposed molten steel surface, which is complex in operation, and the vacuum treatment time is long, which has obvious limitations.

[0006] CN202011093417.9: The application discloses a RH furnace dehydrogenation method and device, relates to the technical field of RH refining, and specifically comprises the following steps: step 1): initial condition; step 2): baking; step 3): vacuumizing treatment; step 4): vacuum heating; step 5): vacuum dehydrogenation treatment; step 6): vacuum decarburization treatment; step 7): measurement; and step 8): vacuum breaking. The dehydrogenation method is simple in process flow, convenient to operate and low in cost, the molten steel can be heated simultaneously in the RH vacuum treatment, the deaeration temperature of the molten steel is ensured, and the dehydrogenation efficiency is improved. In the dehydrogenation device, the riser pipe and the downcomer pipe are both provided with a conical structure with a large opening at the bottom and a small opening at the top, so that the scouring of the molten steel on the inner wall of the vacuum chamber is reduced, the dehydrogenation effect of the device is effectively improved, the riser pipe and the downcomer pipe have good corrosion resistance and high-temperature resistance, and have a long service life. The patent heats the molten steel in the RH vacuum treatment, improves the dehydrogenation efficiency, and is relatively high in cost.

[0007] CN201811483230.2: An RH furnace refining hydrogen-oxygen control process, the process steps are: measuring the temperature of the molten steel, sampling and measuring the N and C content; vacuumizing operation, using high-pressure nitrogen and oxygen mixture or argon and oxygen as lifting gas; the vacuum degree is kept at 3-4.5kPa, and refining slag is added; then enter the decarburization process; add chromium iron for chromium alloying before vacuum circulating degassing refining; measure the temperature and oxygen of the molten steel; add low-carbon ferrosilicon for deoxidation operation and alloying adjustment; dehydrogenation and setting treatment; break the vacuum, and perform bottom argon blowing soft stirring on the ladle. The patent is a normal dehydrogenation process in the vacuum refining process, and the dehydrogenation rate has certain limitations.

[0008] CN201611206242.1: The application discloses a dehydrogenation and nitrogen-increasing control method in an RH vacuum treatment process, which comprises the following steps: after the alloy component of molten steel is adjusted to a target value in LF refining, the nitrogen content is increased to 150-250ppm by means of bottom blowing N2 or feeding silicon nitride wire; the ladle is moved to an RH station for vacuum degassing, N2 is used as lifting gas, and the vacuum degree of the vacuum chamber is kept below 100pa; after 10-20min under the condition that the vacuum degree is below 100pa, part of vacuum pumps are closed, the vacuum chamber is filled with N2, the vacuum degree of the vacuum chamber is stably controlled to be between 10-30kpa, and the N2 flow is increased, so that the nitrogen content in the molten steel is increased to 400-600ppm. According to the method, the nitrogen content of the molten steel is increased in the early stage of vacuum treatment, the nitrogen content in the molten steel can be effectively reserved when the molten steel is treated in the RH vacuum, and the time and difficulty of subsequent molten steel nitrogen-increasing are reduced. The patent increases the nitrogen content of the molten steel in the early stage of vacuum treatment, the nitrogen-increasing process is relatively complicated and difficult to control, and the treatment effect is unstable.

[0009] Based on the above analysis, in order to enhance the RH dehydrogenation effect, it is necessary to put forward a refining method for improving the RH dehydrogenation rate of heavy rail steel to solve the existing problems. SUMMARY

[0010] According to the above technical problems, a refining method for improving the RH dehydrogenation rate of heavy rail steel is provided. The present application mainly enhances the circulation of molten steel in the ladle by bottom argon blowing in the second half of the ladle, increases the circulation flow, successfully solves the problem of high hydrogen content in the steel and difficult to remove, can reduce the hydrogen content in the steel to below 0.9ppm, the RH dehydrogenation rate can reach more than 85%, and the quality of heavy rail steel is greatly improved.

[0011] The technical means adopted by the present application are as follows:

[0012] A refining method for improving the RH dehydrogenation rate of heavy rail steel, comprising the following steps:

[0013] Step one, dry the alloy and auxiliary materials used in the RH refining process;

[0014] Step two, the ladle reaches the RH station, temperature sampling and composition analysis are carried out;

[0015] Step three, after the RH insertion tube enters the molten steel, normal treatment operation is started, and vacuum treatment is carried out;

[0016] Step four, after the vacuum treatment is finished, alloying is carried out according to the composition of the molten steel, and after alloying, argon is blown from the bottom of the ladle;

[0017] Step five, after the RH treatment is finished, the molten steel is stirred by soft argon blowing, and after the soft blowing is finished, the heavy rail steel is prepared.

[0018] Further, in the step one, the drying is realized by roasting.

[0019] Further, in the step three, the vacuum degree is controlled below 3mbar, and the lifting gas flow is controlled at 1200-1400NL / min.

[0020] Further, in the step three, the vacuum treatment time is controlled at 12-16min.

[0021] Further, in the step four, the ladle is provided with a gas blowing hole, and the argon is blown into the ladle through the gas blowing hole.

[0022] Further, in the step four, the argon is blown into the ladle at a flow rate of 80NL-120 / min.

[0023] Further, the position of the gas blowing hole and the center of the RH immersion tube are arranged on the same longitudinal axis.

[0024] Further, in the step five, the soft blowing time is 5-10 min, and the soft blowing gas flow is controlled at 50-80 NL / min.

[0025] Compared with the prior art, the application has the following advantages:

[0026] 1. The refining method for improving RH dehydrogenation rate of heavy rail steel provided by the application can improve the RH dehydrogenation rate and the steel cleanliness. After the application is implemented in a certain factory, obvious economic benefits are created. The application can be popularized and applied in the same industry in China.

[0027] 2. The refining method for improving RH dehydrogenation rate of heavy rail steel provided by the application successfully solves the problems of high hydrogen content in the steel and difficult removal of hydrogen by means of bottom argon blowing in the ladle in the second half of the process, improving the circulation of the molten steel in the ladle and the circulation flow, and reducing the hydrogen content in the steel to below 0.9 ppm, so that the RH dehydrogenation rate can reach above 85%, and the quality of the heavy rail steel is greatly improved.

[0028] 3. The refining method for improving RH dehydrogenation rate of heavy rail steel provided by the application can greatly improve the dehydrogenation effect of the molten steel, improve the uniformity of the steel, and reduce the quality defects of the steel after application.

[0029] Based on the above reasons, the application can be widely popularized in the field of steel metallurgical refining and the like. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0031] Figure 1 The figure is a flowchart of the method of the application. DETAILED DESCRIPTION

[0032] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict. The application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0033] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The description of the at least one example embodiment is actually only illustrative, but not intended to limit the present application and its application or use in any way. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0034] It should be noted that the terms used herein are only intended to describe specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a reference to the presence of a feature, step, operation, device, component and / or combinations thereof.

[0035] Unless specifically stated otherwise, the relative arrangement of components and steps, numerical expressions, and numerical values set forth in the various examples herein are not limiting of the scope of the application. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and not of limitation. The detailed description is divided into sections to facilitate better understanding. The scope of the application is not intended to be limited to the examples described herein, but is intended to extend to any alternatives, modifications, equivalents and / or combinations falling within the scope of the application. Any specific values recited herein are meant to be illustrative only and not limiting. Other examples of the exemplary embodiments can have different values. It is noted that like numbers and letters refer to like elements throughout.

[0036] As shown in Figure 1 The present application provides a refining method for improving the RH dehydrogenation rate of heavy rail steel, comprising the following steps:

[0037] (1) The alloy and auxiliary materials used in the RH refining process are roasted to ensure their dryness;

[0038] (2) The ladle reaches the RH station, and temperature measurement and sampling are performed;

[0039] (3) After the RH insertion tube enters the steel liquid, normal treatment operation is started, vacuum treatment is performed, and the vacuum degree is controlled below 3 mbar, and the lifting gas flow is controlled at 1200-1400 NL / min;

[0040] (4) The ladle bottom is provided with a blowing hole, and the position of the blowing hole is located on the same longitudinal axis as the center of the RH immersion tube;

[0041] (5) Alloying according to the composition of the molten steel, and then starting bottom argon blowing;

[0042] (6) The argon is blown into the ladle from the ladle bottom blowing hole at a flow rate of 80 NL / min to 120 / min;

[0043] (7) The vacuum treatment time is controlled to be 12 min to 16 min;

[0044] (8) After the RH treatment is completed, the molten steel is subjected to soft argon blowing stirring, the soft blowing time is 5 min to 10 min, and the soft blowing gas flow rate is controlled to be 50 NL / min to 80 NL / min; after the soft blowing is completed, the heavy rail steel is prepared.

[0045] The advantages of the present application are that the molten steel circulation in the ladle is enhanced by the ladle bottom argon blowing in the second half, the circulation flow rate is improved, the problem of high hydrogen content in the steel and difficult removal is successfully solved, the hydrogen content in the steel can be reduced to below 0.9 ppm, the RH dehydrogenation rate can reach above 85%, and the quality of the heavy rail steel is greatly improved.

[0046] The present application can improve the RH refining dehydrogenation rate and improve the steel cleanliness. After the implementation of the present application in a certain factory, obvious economic benefits are created. The present application can be popularized and applied in the same industry in China.

[0047] After the application of the present application, the dehydrogenation effect of the molten steel can be greatly improved, the steel uniformity can be improved, and the steel quality defects can be reduced. After the implementation of the present application in a certain factory, obvious economic benefits are created, and it is expected to create more than 6.5 million yuan per year.

[0048] Example 1

[0049] For a 120 t ladle, the process steps for producing heavy rail steel are as follows:

[0050] (1) The ladle reaches the RH station, temperature sampling and composition analysis are performed;

[0051] (2) After the insertion tube enters the molten steel, the RH starts normal treatment operation;

[0052] (3) After alloying, bottom blowing is performed at a bottom blowing flow rate of 80 NL / min, and the vacuum treatment time is 16 min;

[0053] (4) After the RH treatment is completed, the molten steel is subjected to soft argon blowing stirring, the soft blowing time is 5 min, and the soft blowing gas flow rate is controlled to be 50 NL / min; after the soft blowing is completed, the heavy rail steel is prepared.

[0054] By this way, the dehydrogenation rate reaches 86.5%, the H content is controlled below 0.9ppm, the quantity of inclusions in the steel is obviously reduced, and the quality of the steel is improved.

[0055] Example 2

[0056] For the 150t ladle, the process steps for producing heavy rail steel are as follows:

[0057] (1) The ladle reaches the RH station, temperature sampling is conducted, and the composition is analyzed;

[0058] (2) After the insertion tube enters the molten steel, the RH starts normal treatment operation;

[0059] (3) After alloying, bottom blowing is conducted at a bottom blowing flow rate of 120NL / min, and vacuum treatment is conducted for 14min;

[0060] (4) After the RH treatment is completed, soft argon blowing is conducted for stirring the molten steel, the soft blowing time is 5min, and the soft blowing gas flow rate is controlled at 80NL / min; after the soft blowing is completed, the heavy rail steel is prepared.

[0061] By this way, the dehydrogenation rate reaches 87.2%, the H content is controlled below 0.9ppm, the quantity of inclusions in the steel is obviously reduced, and the quality of the steel is improved.

[0062] Example 2

[0063] For the 120t ladle, the process steps for producing heavy rail steel are as follows:

[0064] (1) The ladle reaches the RH station, temperature sampling is conducted, and the composition is analyzed;

[0065] (2) After the insertion tube enters the molten steel, the RH starts normal treatment operation;

[0066] (3) After alloying, bottom blowing is conducted at a bottom blowing flow rate of 100NL / min, and vacuum treatment is conducted for 14min;

[0067] (4) After the RH treatment is completed, soft argon blowing is conducted for stirring the molten steel, the soft blowing time is 5min, and the soft blowing gas flow rate is controlled at 80NL / min; after the soft blowing is completed, the heavy rail steel is prepared.

[0068] By this way, the dehydrogenation rate reaches 87.7%, the H content is controlled below 0.9ppm, the quantity of inclusions in the steel is obviously reduced, and the quality of the steel is improved.

[0069] 5Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and are not limited to

[0070] The above-mentioned embodiments are merely used for describing the present application, and not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, the skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features thereof can be replaced by other technical features that are equivalent thereto, without departing from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A refining method for improving the RH dehydrogenation rate of heavy rail steel, characterized in that: The steps include: Step 1: Drying the alloy and auxiliary materials used in the RH refining process; Step 2: When the ladle arrives at the RH station, temperature measurement and sampling are carried out to analyze the composition; Step 3: After the RH insertion tube enters the molten steel, normal processing operation begins and vacuum treatment is performed; Step 4: After the vacuum treatment is completed, alloying is performed according to the composition of the molten steel, and argon is blown into the bottom of the molten steel after alloying; Step 5: After the RH treatment is completed, the molten steel is soft-blown with argon gas for stirring. After the soft blowing is completed, heavy rail steel is prepared; In the fourth step, a blowing hole is provided at the bottom of the ladle, and argon gas is blown into the ladle through the blowing hole; the argon gas is blown into the ladle at a flow rate of 80-120 NL / min; The positions of the blowing holes and the center of the RH immersion riser are arranged on the same longitudinal axis.

2. The refining method for improving the RH dehydrogenation rate of heavy rail steel according to claim 1, characterized in that: In the step 1, drying is achieved by baking.

3. The refining method for improving the RH dehydrogenation rate of heavy rail steel according to claim 1, characterized in that: In step 3, the vacuum degree is controlled below 3 mbar, and the lifting gas flow rate is controlled at 1200-1400 NL / min.

4. The refining method for improving the RH dehydrogenation rate of heavy rail steel according to claim 1 or 3, characterized in that: In the step 3, the vacuum treatment time is controlled at 12-16 minutes.

5. The refining method for improving the RH dehydrogenation rate of heavy rail steel according to claim 1, characterized in that: In the step 5, the soft blowing time is 5-10 minutes, and the soft blowing gas flow rate is controlled at 50-80 NL / min.

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