CN111455132A - Production method for downgrading grade A inclusions in titanium-containing steels - Google Patents

Abstract

The invention relates to a production method for reducing the grade of titanium-containing steel A-type inclusions, and belongs to the technical field of steel smelting. The invention provides a production method for reducing the grade of titanium-containing steel A-type inclusions, which comprises the following steps: feeding cored wires containing titanium dioxide powder into molten steel in 2-5 batches in the smelting process, wherein the wire feeding speed is 1-4 m/s, and the total amount of the fed titanium dioxide is controlled to be 40-120 ppm; the cored wire consists of a sheath and a core layer, wherein the core layer consists of titanium dioxide powder with the particle size of 5-300 nm. The application of the invention can solve the problem that sulfide inclusions exceed the standard in most of the steel enterprises at present, and meet the production requirements of steel grades with higher requirements on A-type inclusions, such as sulfur-containing alloy structural steel, sulfur-containing free-cutting steel and other steel grades.

Description

Production method for downgrading grade A inclusions in titanium-containing steels

technical field

The invention relates to a production method for reducing the grade of A-type inclusions in titanium-containing steel, and belongs to the technical field of iron and steel smelting.

Background technique

With the vigorous development of the iron and steel industry, the comprehensive performance requirements of steel are getting higher and higher, and the cleanliness requirements of molten steel are becoming more and more strict. However, non-metallic inclusions will inevitably be introduced in the smelting process, which will endanger the properties of the steel. For example, an appropriate amount of sulfide in steel can improve the electromagnetic properties and machinability of the steel, but if the content is too large, the hot workability and corrosion resistance of the steel will be reduced. Since the affinity of S element with Mn, Ni, Ti, Zr and other elements in molten steel is much greater than that of Fe, it is easy to generate sulfides such as MnS and NiS. MnS will reduce the pitting corrosion resistance and crevice corrosion resistance of the steel; too high sulfide inclusions in the steel will reduce the transverse elongation and section shrinkage rate of the steel; during the rolling process, excessive sulfide will lead to slab cracks. At present, most iron and steel enterprises are faced with the problem that sulfide-type inclusions (type-A inclusions) are easy to exceed the standard. Reducing the rating of type-A inclusions is especially important for the production of gear steel, heavy rail steel, sulfur-containing free-cutting steel and other steel grades. .

SUMMARY OF THE INVENTION

The object of the present invention is to provide a production method for reducing the grade of A-type inclusions in titanium-containing steel materials.

The invention provides a production method for reducing the rating of A-type inclusions in titanium-containing steel materials: during the smelting process, cored wires containing titanium dioxide powder are fed into molten steel in 2-5 batches, and the wire feeding speed is 1-4 m/s, The total amount of fed titanium dioxide is controlled to be 40-120 ppm; wherein, the cored wire is composed of two parts, an outer skin and a core layer, and the core layer is composed of titanium dioxide powder with a particle size of 5-300 nm.

Further, the production method satisfies at least one of the following:

During the smelting process, the cored wire containing titanium dioxide powder is fed into the molten steel in 2 to 3 batches;

The interval between each batch is 1～4min;

Preferably, the interval between each batch is 2-3 minutes;

The feeding speed is 2～3m/s;

Control the total amount of titanium dioxide fed to 60-100ppm;

The particle size range of the titanium dioxide powder is 5-100 nm;

The average particle size of the titanium dioxide powder is 30-200 nm;

Preferably, the average particle size of the titanium dioxide powder is 50-60 nm.

Further, the production method satisfies at least one of the following:

The outer skin is made of low carbon steel;

The thickness of the outer skin is 2-5mm;

Preferably, the thickness of the outer skin is 2-3 mm;

Most preferably, the thickness of the skin is 2mm.

Further, the cored wire is a round pipe with an outer diameter of 5-20 mm.

Preferably, the cored wire is a round pipe with an outer diameter of 10-12 mm.

Further, the cored wire is fed before the LF or RH exits the station.

Preferably, the cored wire is fed after the RH refining is completed and before going out of the station.

Further, the ladle is blown with argon gas at the bottom to ensure that the diameter of the exposed molten steel surface on the slag surface of the ladle is 10-50 cm, and the cored wire is fed into the ladle from the exposed molten steel surface.

Preferably, the diameter of the exposed molten steel surface of the ladle slag surface is 20-30 cm.

Further, the titanium-containing steel material is 20CrMnTi alloy structural steel, wherein the S content is 0.015%-0.030%, and the Ti content is 0.04%-0.10%.

Further, the 20CrMnTi alloy structural steel is gear steel.

Further, the titanium-containing steel material is 20MnTiB alloy structural steel, wherein the S content is 0.015%-0.030%, and the Ti content is 0.04%-0.10%.

In the present invention, the thickness of the outer skin is 2 to 5 mm. If the outer skin is too thin, it cannot pass through the wire feeder, and the steel is too soft to bite into the molten steel. Steel temperature control.

In the present invention, it is ensured that the diameter of the exposed molten steel surface of the ladle slag surface is 10-50 cm, and the cored wire can be fed, and the temperature drop will not be too large at the same time. If it is less than 10cm, it is not easy to align the cored wire with the hole to enter the molten steel. If it is greater than 50cm, the temperature drop will be large, and the molten steel will oxidize more, which is not conducive to the control of the purity of the molten steel.

The invention provides a production method for reducing the grade of A-type inclusions in titanium-containing steel. By feeding a cored wire containing titanium dioxide powder during the smelting process, it plays the role of promoting the dispersion and distribution of MnS and other inclusions in the steel, so as to ensure A-type inclusions. Inclusion rating ≤ 2.0. The application of the invention can solve the situation of exceeding the standard sulfide inclusions encountered by most iron and steel enterprises at present, and meet the production requirements of steel types with high requirements for A-type inclusions, such as sulfur-containing gear steel, sulfur-containing alloy structural steel and other steel types .

Detailed ways

The invention provides a production method for reducing the rating of A-type inclusions in titanium-containing steel materials: during the smelting process, cored wires containing titanium dioxide powder are fed into molten steel in 2-5 batches, and the wire feeding speed is 1-4 m/s, The total amount of fed titanium dioxide is controlled to be 40-120 ppm; wherein, the cored wire is composed of two parts, an outer skin and a core layer, and the core layer is composed of titanium dioxide powder with a particle size of 5-300 nm.

The present invention is accomplished based on the following findings of the inventor: for the inclusion of sulfides in titanium-containing steel, the present invention promotes an increase in the content of titanium dioxide by feeding a cored wire containing titanium dioxide powder into the molten steel, which in turn correlates with the titanium dioxide in the molten steel. The elements react to form finely dispersed titanium dioxide. Titanium oxide particles can provide the nucleation core at the solidification front of molten steel, as the attachment point for the precipitation of MnS and other inclusions during the solidification process, and then form finely dispersed MnS inclusions, thereby reducing the formation of large-particle MnS inclusions. Finally, the purpose of reducing the grade of A-type inclusions in steel is achieved. However, the inventors found in practical application that feeding the above-mentioned cored wire does not always effectively reduce the grade of A-type inclusions of the steel, the feeding method, wire feeding speed, feeding amount and titanium dioxide content of the cored wire The particle size of the powder has a significant impact on the impurity reduction effect.

Specifically, the total amount of titanium dioxide fed should be controlled within the range of 40-120 ppm. When the added amount is more than 120 ppm, titanium dioxide is easy to aggregate and grow to form inclusions with large particles, which does not help to reduce the grade of A-type inclusions. On the other hand, if the addition amount is less than 40 ppm, the obvious improvement effect cannot be exerted.

Secondly, the cored wire is fed into the molten steel in 2 to 5 batches during the smelting process. In order to save the operation time and simplify the production process, the inventor tried to feed the cored wire at one time, but the grade of A-type inclusions was still as high as 2.5, and a satisfactory improvement effect could not be obtained. The inventor analyzes that feeding all the cored wires at one time may cause the aggregation of nano-titanium dioxide in a local area, thereby forming large-particle inclusions, so it is preferable to feed in 2 to 5 batches. It is further preferred to add 2 to 3 batches, thereby avoiding the problem of tight production rhythm and making the production process smoother.

Again, the feeding speed is 1-4m/s. It has been verified by experiments that when the line feeding speed is greater than 4m/s, the grade of A-type inclusions of the obtained steel cannot be effectively improved. The analysis is also caused by the high concentration of titanium dioxide in the local area, which leads to the aggregation of large-particle inclusions. If the wire feeding speed is lower than 1m/s, the depth of the cored wire penetrating the molten steel is not enough. As a result, most of the titanium dioxide is adsorbed by the slag, which is difficult to provide enough attachment points for the precipitation of inclusions such as MnS.

Finally, the core layer consists of titanium dioxide powder with a particle size of 5-300 nm. The particle size of titanium dioxide powder is too large, which is not conducive to the control of inclusions, and is easy to aggregate into large-particle inclusion clusters. However, it is also necessary to comprehensively consider the cost of raw materials. If the particle size is too small, the finer titanium dioxide will be more expensive, which will greatly increase the production cost.

The solution of the present invention will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following examples are only used to illustrate the present invention, and should not be construed as limiting the scope of the present invention. If no specific technique or condition is indicated in the examples, the technique or condition described in the literature in the field or the product specification is used. The reagents or instruments used without the manufacturer's indication are conventional products that can be obtained from the market.

Embodiment 1 adopts the method of the present invention to produce 20CrMnTi gear steel

Preparation of titanium dioxide cored wire: including preparing the core layer of the cored wire and wrapping the core layer through the outer skin to form a round pipe. The core layer is composed of titanium dioxide powder (purity greater than 99%), the average particle diameter of the titanium dioxide powder is 50 nm, and the particle diameter ranges from 10 nm to 90 nm. The outer skin is made of low carbon cold rolled strip with a thickness of 2mm. The outer diameter of the entire cored wire is 10mm.

When producing 20CrMnTi gear steel, the S content in the steel is 0.020% and the Ti content is 0.060%. After the RH refining is completed and before leaving the station, the above-mentioned cored wire is fed to the molten steel. Before feeding, the ladle is blown with argon gas, so that the diameter of the exposed molten steel surface on the slag surface of the ladle is 20 cm. It is fed into the ladle at the same time, and the feeding speed is 3.0m/s. During the wire feeding process, the titanium dioxide cored wire was added in 2 times, each time adding 50ppm of titanium dioxide, and the interval time was 2min. After the wire feeding is completed, the Ti content in the steel is 0.055%, and the molten steel is sent to the continuous casting platform for continuous casting at 5 minutes.

The molten steel was treated by the above method and passed the GB/T 10561-2005 standard rating, and the final production of the bar A-type inclusions was rated as 1.5.

Embodiment 2 adopts the method of the present invention to produce 20CrMnTi gear steel

Preparation of titanium dioxide cored wire: including preparing the core layer of the cored wire and wrapping the core layer through the outer skin to form a round pipe. The core layer is composed of titanium dioxide powder (purity greater than 99%), the average particle diameter of the titanium dioxide powder is 60 nm, and the particle diameter ranges from 5 nm to 95 nm. The outer skin is made of low carbon cold rolled strip with a thickness of 2mm. The outer diameter of the entire cored wire is 15mm.

When producing 20CrMnTi gear steel, the S content in the steel is 0.030%, and the Ti content is 0.070%. After the RH refining is completed and before leaving the station, the above-mentioned cored wire is fed to the molten steel. Before feeding the wire, the ladle is blown with argon gas, so that the diameter of the exposed molten steel surface on the slag surface of the ladle is 30cm, and the cored wire is removed from the exposed molten steel surface. It is fed into the ladle at the same time, and the feeding speed is 1.0m/s. During the wire feeding process, the titanium dioxide cored wire was added in three times, each time adding titanium dioxide 40ppm, and the interval time was 2min. After the wire feeding is completed, the Ti content in the steel is 0.066%, and the molten steel is sent to the continuous casting platform for continuous casting at 3 minutes.

The molten steel was treated by the above method, and passed the GB/T 10561-2005 standard rating, and the final grade of steel A inclusions obtained was grade 2.0.

Embodiment 3 adopts the inventive method to produce 20MnTiB alloy structural steel

Preparation of titanium dioxide cored wire: including preparing the core layer of the cored wire and wrapping the core layer through the outer skin to form a round pipe. The core layer is composed of titanium dioxide powder (purity greater than 99%), the average particle diameter of the titanium dioxide powder is 55nm, and the particle diameter ranges from 15nm to 98nm. The outer skin is made of low carbon cold rolled strip with a thickness of 2mm. The outer diameter of the entire cored wire is 20mm.

When producing 20MnTiB alloy structural steel, the S content in the steel is 0.028%, and the Ti content is 0.08%. After the RH refining is completed and before leaving the station, the above-mentioned cored wire is fed to the molten steel. Before feeding the wire, the ladle is blown with argon gas, so that the diameter of the exposed molten steel surface on the slag surface of the ladle is 25cm, and the cored wire is removed from the exposed molten steel surface. It is fed into the ladle, and the feeding speed is 4.0m/s. During the wire feeding process, the nano-titanium dioxide cored wire was added in two times, and 60 ppm of titanium dioxide was added each time, and the interval time was 3 minutes. After the wire feeding is completed, the Ti content in the steel is 0.076%, and the molten steel is sent to the continuous casting platform for continuous casting at 4 minutes.

The molten steel was treated by the above method, and passed the GB/T 10561-2005 standard rating, and the final grade of steel A inclusions obtained was grade 1.5.

Comparative Example 1 Production of 20CrMnTi gear steel without adding titanium dioxide cored wire

When producing 20CrMnTi gear steel, the S content in the steel is 0.020%, and the Ti content is 0.070%. Titanium dioxide cored wire is not added before RH leaves the station, and the Ti content in the steel is 0.069%. The molten steel is directly sent to the continuous casting platform for continuous casting.

The final product produced by the above method is graded according to the GB/T 10561-2005 standard, and the A-type inclusions are graded as 2.5.

Comparative Example 2 Production of 20MnTiB alloy structural steel without adding titanium dioxide cored wire

When producing 20MnTiB alloy structural steel, the S content in the steel is 0.028%, and the Ti content is 0.060%. No titanium dioxide cored wire was added before RH left the station, and the Ti content in the steel was 0.059%, and the molten steel was sent to the continuous casting platform for continuous casting.

The final product produced by the above method is rated by GB/T 10561-2005 standard, and the A-type inclusions are rated as 3.0.

Comparative Example 3 Effect of Titanium Dioxide Addition on the Rating of Class A Inclusions

When producing 20MnTiB alloy structural steel, the S content in the steel is 0.027%, and the Ti content is 0.08%. After the RH refining is completed and before leaving the station, the above-mentioned cored wire is fed to the molten steel. Before feeding the wire, the ladle is blown with argon gas, so that the diameter of the exposed molten steel surface on the slag surface of the ladle is 25cm, and the cored wire is removed from the exposed molten steel surface. It is fed into the ladle, and the feeding speed is 4.0m/s. In the wire feeding process, the nano-titanium dioxide cored wire is added in two times, each time adding titanium dioxide 180ppm, and the interval time is 3min. After the wire feeding is completed, the Ti content in the steel is 0.076%, and the molten steel is sent to the continuous casting platform for continuous casting at 4 minutes.

The molten steel was treated by the above method and passed the GB/T 10561-2005 standard rating. The final grade of the steel A-type inclusions was 2.5, and the large-particle D-type inclusions appeared in the steel, which was rated as 2.5.

Comparative Example 4 Influence of Feeding Method on the Rating of Class A Inclusions

Preparation of titanium dioxide cored wire: including preparing the core layer of the cored wire and wrapping the core layer through the outer skin to form a round pipe. The core layer is composed of titanium dioxide powder (purity greater than 99%), the average particle diameter of the titanium dioxide powder is 50 nm, and the particle diameter ranges from 10 nm to 90 nm. The outer skin is made of low carbon cold rolled strip with a thickness of 2mm. The outer diameter of the entire cored wire is 10mm.

When producing 20CrMnTi gear steel, the S content in the steel is 0.020% and the Ti content is 0.060%. After the RH refining is completed and before leaving the station, the above-mentioned cored wire is fed to the molten steel. Before feeding, the ladle is blown with argon gas, so that the diameter of the exposed molten steel surface on the slag surface of the ladle is 20 cm. It is fed into the ladle at the same time, and the feeding speed is 3.0m/s. During the wire feeding process, the titanium dioxide cored wire was added once, and 120ppm of titanium dioxide was added. After the wire feeding was completed, the Ti content in the steel was 0.062%, and the molten steel was sent to the continuous casting platform for continuous casting at 5 minutes.

The molten steel was treated by the above method and passed the GB/T 10561-2005 standard rating, and the final production of the bar A-type inclusions was rated as 2.5.

Comparative Example 5 Influence of Line Feeding Speed on the Rating of Class A Inclusions

Preparation of titanium dioxide cored wire: including preparing the core layer of the cored wire and wrapping the core layer through the outer skin to form a round pipe. The core layer is composed of titanium dioxide powder (purity greater than 99%), the average particle diameter of the titanium dioxide powder is 60 nm, and the particle diameter ranges from 5 nm to 95 nm. The outer skin is made of low carbon cold rolled strip with a thickness of 2mm. The outer diameter of the entire cored wire is 15mm.

When producing 20CrMnTi gear steel, the S content in the steel is 0.030%, and the Ti content is 0.065%. After the RH refining is completed and before leaving the station, the above-mentioned cored wire is fed to the molten steel. Before feeding the wire, the ladle is blown with argon gas, so that the diameter of the exposed molten steel surface on the slag surface of the ladle is 30cm, and the cored wire is removed from the exposed molten steel surface. It is fed into the ladle at the same time, and the feeding speed is 6.0m/s. During the wire feeding process, the titanium dioxide cored wire is added in 2 times, each time adding titanium dioxide 60ppm, and the interval time is 1min. After the wire feeding is completed, the Ti content in the steel is 0.061%, and the molten steel is sent to the continuous casting platform for continuous casting at 3 minutes.

The molten steel was treated by the above method, and passed the GB/T 10561-2005 standard rating, and the final grade of steel A inclusions obtained was 2.5.

Comparative Example 6 Effect of TiO2 Powder Particle Size on the Rating of Class A Inclusions

Preparation of titanium dioxide cored wire: including preparing the core layer of the cored wire and wrapping the core layer through the outer skin to form a round pipe. The core layer is composed of titanium dioxide powder (purity greater than 99%), the average particle diameter of the titanium dioxide powder is 180nm, and the particle diameter ranges from 120nm to 350nm. The outer skin is made of low carbon cold rolled strip with a thickness of 2mm. The outer diameter of the entire cored wire is 20mm.

When producing 20CrMnTi gear steel, the S content in the steel is 0.028% and the Ti content is 0.065%. The above-mentioned cored wire is fed to the molten steel after the RH refining is completed and before going out of the station. Before feeding, the ladle was blown with argon at the bottom, so that the diameter of the exposed molten steel surface on the slag surface of the ladle was 25cm, and the cored wire was fed into the ladle from the exposed molten steel surface, and the feeding speed was 4.0m/s. During the wire feeding process, the titanium dioxide cored wire was added in two times, each time adding titanium dioxide 60ppm, and the interval time was 3min. After the wire feeding is completed, the Ti content in the steel is 0.060%, and the molten steel is sent to the continuous casting platform for continuous casting at 4 minutes.

The molten steel was treated by the above method, and the final steel produced passed the GB/T 10561-2005 standard rating, and the A-type inclusions were rated as 3.0.

It should be noted that the specific features, structures, materials or characteristics described in this specification may be combined in a suitable manner in any one or more embodiments. Furthermore, those skilled in the art may combine and combine the different embodiments described in this specification and the features of the different embodiments without contradicting each other.

Claims (10)

1. The production method for reducing the grade of the A-type inclusions of the titanium-containing steel is characterized by comprising the following steps of: feeding cored wires containing titanium dioxide powder into molten steel in 2-5 batches in the smelting process, wherein the wire feeding speed is 1-4 m/s, and the total amount of the fed titanium dioxide is controlled to be 40-120 ppm; the cored wire consists of a sheath and a core layer, wherein the core layer consists of titanium dioxide powder with the particle size of 5-300 nm.

2. The method of claim 1, wherein: at least one of the following is satisfied:

feeding cored wires containing titanium dioxide powder into molten steel in 2-3 batches in the smelting process;

the interval between each batch is 1-4 min;

preferably, the interval between each batch is 2-3 min;

the wire feeding speed is 2-3 m/s;

controlling the total amount of titanium dioxide fed to be 60-100 ppm;

the particle size range of the titanium dioxide powder is 5-100 nm;

the average particle size of the titanium dioxide powder is 30-200 nm;

preferably, the average particle size of the titanium dioxide powder is 50 to 60 nm.

3. The method of claim 1, wherein: at least one of the following is satisfied:

the outer skin is made of low-carbon steel;

the thickness of the outer skin is 2-5 mm;

preferably, the thickness of the outer skin is 2-3 mm;

most preferably, the thickness of the skin is 2 mm.

4. The production method as set forth in any one of claims 1 to 3, characterized in that: the core-spun yarn is a circular tube yarn with the outer diameter of 5-20 mm; preferably, the cored wire is a circular tube wire with the outer diameter of 10-12 mm.

5. The production method of claim 1, wherein the core-spun yarn is fed before the exit of L F or RH, preferably after the RH refining is finished and before the exit.

6. The production method as set forth in claim 1 or 5, characterized in that: bottom blowing argon gas to the steel ladle to ensure that the diameter of the slag surface of the steel ladle exposed to the liquid level is 10-50 cm, and feeding the cored wire into the steel ladle from the exposed liquid level; preferably, the diameter of the bare molten steel surface of the slag surface of the steel ladle is 20-30 cm.

7. The method of claim 1, wherein: the titanium-containing steel material contains 0.04-0.20% of Ti.

8. The method of claim 7, wherein: the titanium-containing steel material is 20CrMnTi alloy structural steel, wherein the S content is 0.015-0.030%, and the Ti content is 0.04-0.10%.

9. The method of claim 8, wherein: the 20CrMnTi alloy structural steel is gear steel.

10. The method of claim 7, wherein: the titanium-containing steel material is 20MnTiB alloy structural steel, wherein the S content is 0.015-0.030%, and the Ti content is 0.04-0.10%.