A carburizer of Mn3C-coated carbonaceous material and its preparation method

Abstract

The present invention discloses a carburizer with Mn3C-coated carbonaceous materials and a preparation method thereof, belonging to the field of metallurgical technology. First, the carbonaceous material is crushed into particles, then uniformly mixed in a mixer, and pressure-sintered into the required shape under the protection of inert gas, and taken out after cooling; the Mn3C powder is heated to melt it under vacuum conditions, and the Mn3C melt and the sintered carbonaceous material are placed in the same mold and cooled to room temperature to form a carburizer with Mn3C-coated carbonaceous materials. The carburizer prepared by the present invention has a specific gravity greater than 2.2 g / cm 3 , and the carburizer can penetrate deep into the molten steel, greatly improving and stabilizing the carbon element recovery rate, which is beneficial to accurately hitting the target carbon content during the smelting process. When the carburizer enters the deep part of the molten steel, the outer layer of Mn3C leaves the carbonaceous material earlier, rapidly increasing the temperature of the molten steel; the present invention adopts a pressure-sintering process without adding a binder, with high strength and low water absorption, and does not generate ash and carburizer dust during the addition process, which is more environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgy technology, and more specifically relates to a high-density, environmentally friendly, and process-temperature-reducing Mn3C-coated carbon material recarburizer and a preparation method thereof. Background Art

[0002] During the steelmaking process, the carbon content in the molten steel often fails to reach the target value due to carbon burnout. Steel mills currently mainly use recarburizers to increase the carbon content in the molten steel. The main problems of conventional recarburizers are as follows: (1) The bulk density is too low. For example, the bulk density of commonly used pitch coke is about 0.6g / cm 3 The specific gravity of coke powder recarburizer is 0.88-1.08g / cm 3 , and the specific gravity of molten steel is about 7.8g / cm 3 , resulting in low carbonization efficiency of conventional recarburizers and unstable carbonization amount, making it difficult to accurately hit the target carbon value, resulting in a decrease in the stability of the quality of finished steel products. (2) The temperature drop is aggravated. The molten iron entering the furnace needs to be purified in a converter first (for vanadium, titanium, etc. processes). The purification process itself will consume 20%-30% of the carbon content in the molten iron, and at the same time, the heat-generating elements Si and Mn are completely oxidized. The subsequent addition of conventional recarburizers will inevitably aggravate the temperature drop and cause insufficient heat source. (3) For the method of using carbon powder cored wire for carbonization, it requires special wire feeding equipment and large investment. (4) For mixed recarburizers bonded into blocks with binders, the binders affect the quality of molten steel.

[0003] Chinese invention patent CN1288256C discloses a "manganese-carbon alloy recarburizer," which is made of metal alloy powder (ferromanganese powder or a mixture of ferromanganese powder and iron powder), a carbon material, and a binder. The recarburizer increases its specific gravity and enhances the recarburization effect by increasing the proportion of manganese and iron elements. The Mn in the recarburizer also plays a role in preventing temperature drop. The recarburizer contains a silica sol binder, which reduces the purity of the molten steel and affects the quality of subsequent products. In addition, the C content in the recarburizer is 20%-47%, and the Mn content is 35.01-55%. Although the specific gravity of the recarburizer is increased, the recarburization efficiency is significantly reduced. Chinese invention patent CN103160643A discloses a recarburizer containing carbon and silicon carbide (SiC), with the SiC content ranging from 3 to 30 parts by weight per 100 parts by weight of carbon. This recarburizer overcomes the drawbacks of existing recarburizers used in semi-steel converter smelting, which suffer from large dosages, poor temperature-raising effects, and slow slagging. However, the preparation process inevitably involves the use of multiple binders. Therefore, there is an urgent need for a high-quality recarburizer that can accurately target carbon values, is environmentally friendly (without the addition of binders), and can compensate for process temperatures. Summary of the Invention

[0004] Aiming at the problems existing in the background art, the purpose of the present invention is to provide a carburizer containing Mn3C with high specific gravity, no binder addition, capable of compensating for the temperature drop during the process, and its preparation method, which is applicable to the smelting of steel grades containing Mn.

[0005] The purpose of the present invention is achieved in the following way:

[0006] The present invention provides a carburizer with Mn3C wrapped around carbonaceous materials. The carburizer is composed of carbonaceous materials and Mn3C powder, and the mass ratio of the carbonaceous materials to the Mn3C powder is 3:1 to 2:1.

[0007] Based on the above technical solution, further, the carbonaceous materials are one or a mixture of two or more of coking carbon, petroleum coke, graphite, and carbon powder.

[0008] Based on the above technical solution, further, the specific gravity of the carburizer is greater than 2.2 g / cm 3 , the compressive strength is 50 - 80 MPa, and the moisture content within 30 days is less than 0.6%.

[0009] On the other hand, the present invention provides a preparation method of the above carburizer with Mn3C wrapped around carbonaceous materials, which mainly includes the following steps:

[0010] (1) Crush the carbonaceous materials into particles, and then mix them evenly in a mixer.

[0011] (2) Under the protection of inert gas, subject the mixed carbonaceous materials to pressure sintering into the required shape, and take them out after cooling.

[0012] (3) Heat the Mn3C powder under vacuum conditions to make it melt.

[0013] (4) Place the Mn3C melt obtained in step (3) and the carbonaceous materials sintered in step (2) in the same mold, and cool to room temperature to form a carburizer with Mn3C wrapped around carbonaceous materials.

[0014] Based on the above technical solution, further, in step (1), the particle size of the crushed carbonaceous material particles ≤ 10 mm.

[0015] Based on the above technical solution, further, in step (1), the mixing time of the carbonaceous material particles is 5 - 30 min, and the rotation speed of the mixer is controlled at 900 - 1100 r / min.

[0016] Based on the above technical solution, further, in step (2), the inert gas is one or a mixture of two or more of nitrogen, argon, and helium; the shape includes spherical, oval, cube-shaped, and cuboid-shaped.

[0017] Based on the above technical solution, further, the specific process of pressure sintering in step (2) is to heat the mixed material to 260°C - 360°C under the protection of inert gas, keep it warm for 10 - 20 min and then apply pressure, and the pressure is controlled at 10 - 20 KN.

[0018] Based on the above technical solution, further, the vacuum degree in step (3) is 1 - 10 Pa.

[0019] Based on the above technical solution, further, the melting temperature in step (3) is 1550 - 1700°C.

[0020] The present invention also provides an application of the above carburizer in the smelting of manganese-containing steel.

[0021] The beneficial effects of the present invention compared with the prior art are as follows:

[0022] (1) The specific gravity of the carburizer prepared by the present invention is greater than 2.2 g / cm 3 , and the carburizer can penetrate deep into the molten steel, greatly improving and stabilizing the carbon element recovery rate, which is conducive to accurately hitting the target carbon content during the smelting process.

[0023] (2) The carburizer prepared by the present invention in the form of Mn3C-coated carbonaceous material is more conducive to exerting the role of Mn element as a heating element. When the carburizer enters the molten steel, the outer layer of Mn3C leaves the carbonaceous material earlier, rapidly increasing the temperature of the molten steel; when the proportion of Mn3C powder in the carburizer is greater than 55%, it can be used to compensate the temperature of semi-steel after purification (vanadium and titanium extraction).

[0024] (3) The carburizer prepared by the present invention adopts a pressure sintering process, without adding binders, has high strength, low water absorption, and does not produce ash and carburizer flying during the addition process, so it is more environmentally friendly. Specific embodiments

[0025] The present invention will be described in detail below with reference to the embodiments. However, the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only part of the embodiments of the present invention. For those skilled in the art, without creative efforts, obtaining other similar embodiments will fall within the protection scope of the present invention.

[0026] Example 1

[0027] This example provides a preparation method of a carburizer with high specific gravity containing Mn3C, without adding binders, and capable of compensating for the temperature drop during the process. Calculated in 100 weight units, the carburizer ratio is: 32 parts of Mn3C powder, 17 parts of coking carbon, 17 parts of petroleum coke, 17 parts of graphite, and 17 parts of carbon powder; it includes the following steps:

[0028] 1) Crush coking carbon, petroleum coke, graphite, and carbon powder into particles with a particle size of 8 - 10 mm respectively, then mix them in a mixer for 6 min, and the rotation speed of the mixer is 900 r / min;

[0029] 2) Place the mixed carbon material in a pressure sintering furnace, introduce argon, slowly heat it to 260 °C, pressurize it after holding for 11 min, control the sintering pressure to be 20 KN, form it into a block, and take it out after cooling with the furnace;

[0030] 3) Heat the Mn3C powder to 1600 °C to melt it under a vacuum of 2 Pa;

[0031] 4) Place the high-temperature molten Mn3C and the sintered mixed block material in the same mold and cool it to room temperature to form a solid with Mn3C wrapping the carbon material.

[0032] Detect the indicators of the recarburizer. The specific gravity of the prepared recarburizer is 2.3 g / cm 3 , the compressive strength is 55 MPa, and the moisture content within 30 days is 0.4%.

[0033] Use the prepared recarburizer for vanadium-titanium hot metal (C is 4.2%, Si is 0.05% - 0.10%, Mn is 0.1% - 0.3%, V is 0.2% - 0.4%). The test station is to add it when tapping vanadium-titanium semi-steel from the converter. The statistical results of 20 heats show that the average carburizing rate of the recarburizer of the present invention is 98.62%, and the fluctuation range of the carburizing rate is 1.08%; after adding the recarburizer, the temperature is increased by 9.6 °C.

[0034] Example 2

[0035] This example provides a preparation method of a recarburizer with Mn3C-wrapped carbon material that has high specific gravity, no binder addition, and can supplement the temperature drop during the process. Calculated by 100 parts by weight, the recarburizer ratio is: 25 parts of Mn3C powder, 25 parts of petroleum coke, 25 parts of coking carbon, and 25 parts of graphite; it includes the following steps:

[0036] 1) Crush coking carbon, petroleum coke, and graphite into particles with a particle size of 6 - 8 mm respectively, then mix them in a mixer for 10 min, and the rotation speed of the mixer is 1100 r / min;

[0037] 2) Place the mixed carbon material in a pressure sintering furnace, introduce argon, slowly heat it to 360 °C, pressurize it after holding for 15 min, control the sintering pressure to be 14 KN, form it into a strip, and take it out after cooling with the furnace;

[0038] 3) Heat the Mn3C powder to 1650 °C to melt it under a vacuum of 1 Pa;

[0039] 4) Place the high-temperature Mn3C melt and the sintered mixed bulk material in the same mold and cool to room temperature to form a solid with Mn3C wrapping the carbon material.

[0040] Detect the indicators of the recarburizer. The specific gravity of the prepared recarburizer is 2.6 g / cm 3 , the compressive strength is 78 MPa, and the moisture content within 30 days is 0.5%.

[0041] Use the prepared recarburizer in medium manganese steel (C is 0.1%, Si is 0.23%, Mn is 5.0%, S ≤ 0.002%, P ≤ 0.007%). The test station is the refining furnace station. The statistical results of 20 furnace charges show that the average carburizing rate of the recarburizer of the present invention is 98.12%, and the fluctuation range of the carburizing rate is 1.22%; after adding the recarburizer, the temperature increases by 5.3 °C.

[0042] Example 3

[0043] This example provides a preparation method of a recarburizer of Mn3C-wrapped carbon material with high specific gravity, no binder added, and capable of compensating for the temperature drop during the process. Calculated in 100 parts by weight unit, the recarburizer ratio is: 30 parts of Mn3C powder, 35 parts of coking carbon, and 35 parts of graphite; the method includes the following steps:

[0044] 1) Crush the coking carbon and graphite into particles with a particle size of 1-6 mm respectively, and then mix them in a mixer for 8 min. The rotation speed of the mixer is 1000 r / min;

[0045] 2) Place the mixed carbon material after mixing in a pressure sintering furnace, introduce argon, slowly heat up to 300 °C, keep it warm for 13 min and then apply pressure, control the sintering pressure to be 12 KN, make it into a spherical shape, and take it out after cooling with the furnace;

[0046] 3) Heat up the Mn3C powder to 1620 °C to melt it under a vacuum of 2 Pa;

[0047] 4) Place the high-temperature Mn3C melt and the sintered mixed bulk material in the same mold and cool to room temperature to form a solid with Mn3C wrapping the carbon material.

[0048] Detect the indicators of the recarburizer. The specific gravity of the prepared recarburizer is 2.7 g / cm 3 , the compressive strength is 60 MPa, and the moisture content within 30 days is 0.3%.

[0049] The prepared recarburizer is used in medium manganese TRIP steel (C is 0.19%, Mn is 7.66%, P is 0.0045%, S is 0.0072%). The test station is the converter station. The statistical results of 20 heats show that the average carburizing rate of the recarburizer of the present invention is 97.82%, and the fluctuation range of the carburizing rate is 1.25%. After adding the recarburizer, the temperature is increased by 4.8 °C.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carburizer with Mn3C-coated carbonaceous material, characterized in that, The carburizer described above is composed of carbonaceous materials and Mn3C powder, and the mass ratio of the carbonaceous materials to the Mn3C powder is 3:1 to 2:1; The carbonaceous materials described above are one or a mixture of two or more of coking carbon, petroleum coke, and graphite; The specific gravity of the recarburizer is greater than 2.2 g / cm 3 , the compressive strength is 50 - 80 MPa, and the moisture content is less than 0.6% within 30 days; The preparation method of the carburizer with Mn3C coating the carbonaceous materials includes the following steps: (1) Crush the carbonaceous materials into particles, and then mix them evenly in a mixer; (2) Under the protection of inert gas, sinter the mixed carbonaceous materials under pressure into the required shape, and take them out after cooling; (3) Heat up the Mn3C powder under vacuum conditions to make it melt; (4) Place the Mn3C melt obtained in step (3) and the carbonaceous materials sintered in step (2) in the same mold, and cool to room temperature to form a carburizer with Mn3C coating the carbonaceous materials; The specific process of pressure sintering in step (2) is to heat up the mixed materials to 260°C - 360°C under the protection of inert gas, keep the temperature for 10 - 20 min and then apply pressure, and the pressure is controlled at 10 - 20 KN.

2. The recarburizer according to claim 1, wherein The particle size of the crushed carbonaceous material particles in step (1) is ≤10 mm.

3. The recarburizer according to claim 1, characterized in that, The mixing time of the carbonaceous material particles in step (1) is 5 - 30 min, and the rotation speed of the mixer is controlled at 900 - 1100 r / min.

4. The recarburizer according to claim 1, characterized in that, The inert gas in step (2) is one or a mixture of two or more of nitrogen, argon, and helium; the shapes include spherical, oval, cube-shaped, and cuboid-shaped.

5. The recarburizer according to claim 1, characterized in that, The vacuum degree in step (3) is 1 - 10 Pa; the melting temperature is 1550 - 1700°C.

6. Application of the carburizer according to any one of claims 1 - 5 in the smelting of manganese-containing steel.