Smelting method for low-carbon low-silicon high-titanium special welding

Abstract

The invention provides a smelting method for low-carbon low-silicon high-titanium special welding. The smelting method comprises the steps of molten iron desulfurization, converter smelting, converter end point component and temperature control and aluminum ingot adding according to the end point oxygen content. Feeding the LF refining furnace into a station, supplying power for a minutes, and adding high-alkalinity refining synthetic slag; b, starting to deoxidize by using calcium carbide after minutes, and carrying out end-point oxygen determination operation; tapping, feeding a low-aluminum low-nitrogen ferrotitanium core-spun yarn, and finally adding ferroboron to start soft blowing operation; and after soft blowing is finished, steel is hoisted for pouring, an integral tank is used for production, and protective casting is well performed in the whole casting process. According to the method, the titanium content can be stably controlled between 0.11% and 0.15%; the silicon content is controlled to be 0.03%, and the carbon content is stably controlled to be 0.07%-0.10%, so that the welding wire is smooth in drawing and good in welding performance; the total oxygen content is controlled within 10 ppm, the castability of the welding wire steel is improved, and the problems that the production process of the steelmaking procedure is unstable, and water gaps of a tundish and a large ladle are blocked and nodulated are successfully solved.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a smelting method for low-carbon, low-silicon and high-titanium special welding. Background Art

[0002] In recent years, welding wire has been widely used in manufacturing industries such as vehicle manufacturing, shipbuilding, and engineering machinery. The demand for welding materials that adapt to automated welding is increasing. In any welding project, the influence of different element contents on welding performance is very important. By controlling the content of different elements, the best welding performance can be achieved, avoiding quality problems in welded joints caused by unreasonable element content in welding materials. Therefore, improving the various properties of welding steel has become a top priority.

[0003] The biggest feature of welding steel is that it must ensure both drawing performance and weld quality and mechanical properties, so there are strict requirements on the chemical composition and metallurgical quality of steel. Carbon is a key element that affects welding performance. Although increasing the carbon content can increase the strength of steel, the welding performance and plasticity will deteriorate. Therefore, the mass fraction of carbon is required to be less than 0.1%. Silicon is often used as a deoxidizer in welding, but when the content reaches a certain level, it will have a negative impact on welding performance. Too much silicon will increase the brittleness of the welded joint, resulting in defects such as easy cracking and easy breakage of the joint.

[0004] Although low-carbon, low-silicon, high-titanium welding wire ensures the welding performance of steel, it brings great difficulties to smelting. This is because the oxygen content in the molten steel will be relatively high due to low carbon and low silicon. If the deoxidation does not meet the standard, oxide inclusions will be generated, which are very easy to form nodules and cause nozzle blockage. After titanium addition, silicon will return, resulting in excessive silicon content. Therefore, solving the problems of nozzle blockage and composition control during the smelting process is a technical problem in the metallurgical field. Summary of the invention

[0005] The present invention provides a smelting method for low-carbon, low-silicon and high-titanium special welding, which successfully solves the problems of unstable production process of steelmaking process and blockage and nodule formation of water inlets of middle and large ladle, and controls the silicon content below 0.03%, ensures the stability of titanium content in molten steel, improves the stability of B, and refines the weld structure.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a smelting method of low-carbon, low-silicon and high-titanium special welding, which comprises the following steps in sequence:

[0007] (1) Pretreatment of molten iron for desulfurization;

[0008] (2) Converter smelting, control the final tapping composition and tapping temperature of the converter, perform deoxidation and alloying during tapping, add 18-20 kg / t low carbon ferromanganese after 1 / 3 of the tapping, then add 1.3-1.80 kg / t aluminum ingots according to the final oxygen content, and finally add slag making material for slag washing;

[0009] (3) LF refining: After the LF refining furnace enters the station and supplies power, high-basicity refining slag is added for slagging within a minute. The basicity of the final slag is required to be controlled between 4 and 6. After b minutes, calcium carbide deoxidation is started to ensure that the color of the refined slag sample is white slag; oxygen is determined at the end of LF refining, and the oxygen content is controlled within 10ppm, and the oxygen determination temperature is greater than 1620℃; after the temperature and composition are qualified, 5.9-6.5m / t low-aluminum and low-nitrogen titanium iron cored wire is fed at a speed of 3-3.5m / s to the wire feeding position, and finally ferroboron is added;

[0010] (4) After the LF titanium wire is fed, the molten steel is soft-blown. The appropriate argon gas is adjusted to make the molten steel surface creep slightly without exposing the molten steel surface. The argon gas pressure is controlled at 0.2-0.4MPa to ensure the soft-blowing effect. The soft-blowing time is ≥10min.

[0011] (5) After the soft blowing is completed, the steel is hoisted to cast 180mm×240mm square billets. The casting process is protected and cast in an integral tank. The impact zone should not have the phenomenon of rice husk turning. The final titanium content is stably controlled between 0.11% and 0.15%.

[0012] Preferably, the desulfurization pretreatment of molten iron in step (1) adopts KR stirring method, the molten iron composition requirement S≤0.010%, and the slag removal operation ensures that the slag is clean without obvious slag blocks.

[0013] Preferably, in step 2), the target composition requirements for steel tapping at the converter end point are P≤0.012%, S≤0.015%, and the steel tapping temperature is ≥1600°C. The order and weight of deoxidation and alloying during steel tapping are as follows: after 1 / 3 of the steel is tapped, 2000-2100kg of low-carbon ferromanganese and 340kg of nickel alloy are first added, and then aluminum ingots are added according to the end point oxygen content: if the end point oxygen content is within 500ppm, 140kg of aluminum ingots are added; if the end point oxygen content is 500-700ppm, 160kg of aluminum ingots are added; if the end point oxygen content is 700-900ppm, 180kg of aluminum ingots are added; finally, 500kg of lime and 50kg of fluorite are added for slag washing to ensure the slag melting effect. Slag is strictly prohibited during the steel tapping process, and the argon gas is turned off after the converter furnace after the steel tapping is completed.

[0014] Preferably, in step (3), the LF refining furnace is supplied with power for 3 minutes and 550-650 kg of high basicity refined slag is added for slagging, and the basicity of the final refined slag is controlled between 4 and 6. After 5 minutes, calcium carbide deoxidation is started, and the first deoxidation amount is controlled to be 80-100 kg according to the Al content after the furnace. After the first power supply, the slag is dipped and the slag color is observed. If the slag sample is yellow-white or white slag, the second deoxidation amount is controlled to be 20-40 kg; medium carbon ferromanganese is added according to the composition to fine-tune the alloy; in the middle and late stages, calcium carbide deoxidation is used again, and the deoxidation amount is controlled to be 10-20 kg to ensure that the color of the steel-out slag is white slag; oxygen is determined at the end point of LF refining, and the oxygen content is controlled to be within 20 ppm, the oxygen determination temperature is greater than 1620°C, and the steel-out temperature is 1630-1640°C. After the temperature and composition are qualified, 650-700 m of low-aluminum, low-nitrogen titanium-iron cored wire is fed to the wire feeding position at a speed of 3-3.5 m / s, and finally ferroboron is added.

[0015] Preferably, after the soft blowing in step (5) is completed, the steel is hung to cast a 180mm×240mm square billet, and protective casting is carried out throughout the casting process. The temperature of the tundish is controlled at 1560-1565°C, the pulling speed is controlled at 1.10m / min, the cross-section of the billet is 180mm×240mm, and the final titanium content is stably controlled between 0.11% and 0.15%, with an average of 0.13%.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are:

[0017] (1) The silicon content of the finished product is stably controlled below 0.03%, which meets the standard composition of this type of welding wire; the carbon content is stably controlled at 0.07%-0.10%, which makes the welding wire drawing smooth and the welding performance good.

[0018] (2) The smelting process of the present invention can stably control the titanium content between 0.11% and 0.15%, with an average of 0.13%, ensuring that the recovery rate of titanium in the molten steel is stable at 95%, improving the stability of B, and refining the weld structure.

[0019] (3) The production process is simple to operate, which helps to improve the castability of welding wire steel and successfully solves the problems of unstable production process and blockage and nodule formation in the water outlet of the middle and large ladle in the steelmaking process. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] This embodiment takes the smelting of HQ23-1 steel as an example to elaborate on a smelting method for low-carbon, low-silicon and high-titanium special welding: the chemical composition of HQ23-1 steel is as follows: 0.07%≤C≤0.10%, Si≤0.03%, 1.60%≤Mn≤1.90%, P≤0.014%, S≤0.005%, 0.32%≤Ni≤0.43%, Cr≤0.05%, Cu≤0.05%, Mo≤0.03%, 0.0040%≤B≤0.0060%, Ca≤0.0015%, 0.09%≤Ti≤0.15%, Al≤0.020%.

[0022] Example 1: The specific steps are as follows

[0023] (1) The blast furnace molten iron was desulfurized by the KR stirring method. The sulfur content of the molten iron after desulfurization was 0.0085%. Then, the slag removal operation was carried out and the slag removal was ensured to be clean.

[0024] (2) Converter smelting, the final tapping composition of the converter requires C 0.037%, Si 0.001%, Mn 0.082%, P0.0074%, S 0.0041%, and the tapping temperature is 1631°C; after 1 / 3 of the tapping, 2050kg of low-carbon ferromanganese is added first, the oxygen content at the end of the tapping is 542ppm, 160kg of aluminum ingots are added, and finally 500kg of lime + 50kg of fluorite are added for slag washing. No slag is discharged during the tapping process, and the argon gas is turned off after the converter furnace after the tapping is completed;

[0025] (3) LF refining: LF refining furnace enters the station and supplies power for 3 minutes before adding 600kg of high-basicity refined slag for slagging. The final slag basicity of refining is 5.6. After 5 minutes, 100kg of calcium carbide deoxidation is started. After the first power supply, the slag is dipped and the slag color is observed. The slag sample is white slag. The second time, 20kg of calcium carbide deoxidation is used; medium-carbon ferromanganese is added according to the composition for alloy fine-tuning; in the later stage, 10-20kg of calcium carbide deoxidation is used again, and the color of the steel-out slag is white slag; the oxygen content at the end of LF refining is 6.5ppm, and the steel-out temperature is 1635℃; from steel-out to the wire feeding position, 700m of low-aluminum, low-nitrogen titanium-iron cored wire is fed at a speed of 3-3.5m / s, and finally ferroboron is added;

[0026] (4) After the LF titanium wire is fed, the molten steel is soft-blown. The appropriate argon gas is adjusted to make the molten steel surface creep slightly without exposing the molten steel surface. The argon gas pressure is controlled at 0.25 / 0.26MPa to ensure the soft-blowing effect. The soft-blowing time is 18min.

[0027] (5) After the soft blowing is completed, the steel is hoisted to cast 180 mm × 240 mm square billets. The casting process is protected and cast in an integral tank. There is no husk turning phenomenon in the impact zone, and the final titanium content is stably controlled at 0.126%. The chemical composition of the finished product is: C 0.081%, Si 0.024%, Mn 1.65%, P0.009%, S 0.0016%, Ni 0.361%, Cr0.021%, Cu 0.016%, Al 0.0076%, B0.0045%, Ti 0.126%, and the balance is slag.

[0028] Example 2: The specific steps are as follows

[0029] (1) The blast furnace hot metal was desulfurized by the KR stirring method. The sulfur content of the hot metal after desulfurization was 0.009%. Then, the slag was removed and the removal was ensured to be clean.

[0030] (2) Converter smelting, the final tapping composition of the converter requires C 0.041%, Si 0.001%, Mn 0.104%, P0.0088%, S 0.0036%, and the tapping temperature is 1631°C; after 1 / 3 of the tapping, 2090kg of low-carbon ferromanganese is added first, the oxygen content at the end of the tapping is 520ppm, 160kg of aluminum ingots are added, and finally 500kg of lime + 50kg of fluorite are added for slag washing. No slag is discharged during the tapping process, and the argon gas is turned off after the converter furnace after the tapping is completed;

[0031] (3) LF refining: LF refining furnace enters the station and supplies power for 3 minutes before adding 600kg of high-basicity refined slag for slagging. The basicity of the final slag is 5.8. After 5 minutes, 100kg of calcium carbide deoxidation is used. After the first power supply, the slag is dipped and the slag color is observed. The slag sample is white slag. The second time, 20kg of calcium carbide deoxidation is used; medium-carbon ferromanganese is added according to the composition for alloy fine-tuning; in the later stage, 10-20kg of calcium carbide deoxidation is used again, and the color of the steel-out slag is white slag; the oxygen content at the end of LF refining is 7.6ppm, and the steel-out temperature is 1637℃; 680m of low-aluminum, low-nitrogen titanium-iron cored wire is fed at a speed of 3-3.5m / s from the steel-out to the wire feeding position, and finally ferroboron is added;

[0032] (4) After the LF titanium wire is fed, the molten steel is soft-blown. The appropriate argon gas is adjusted to make the molten steel surface creep slightly without exposing the molten steel surface. The argon gas pressure is controlled at 0.24 / 0.25MPa to ensure the soft-blowing effect. The soft-blowing time is 19min.

[0033] (5) After the soft blowing is completed, the steel is hoisted to cast a 180 mm × 240 mm square billet. The casting process is protected and cast in an integral tank. There is no rice husk turning phenomenon in the impact zone. The final titanium content is stably controlled at 0.134%. The chemical composition of the finished product is: C 0.078%, Si 0.025%, Mn 1.675%, P0.0076%, S 0.0011%, Ni 0.368%, Cr0.0187%, Cu 0.0155%, Al 0.0081%, B0.0048%, Ti 0.134%, and the balance is slag.

[0034] Embodiment 3: The specific steps are as follows:

[0035] (1) The blast furnace hot metal was desulfurized by the KR stirring method. The sulfur content of the hot metal after desulfurization was 0.0084%. Then, the slag was removed cleanly.

[0036] (2) Converter smelting, the final tapping composition of the converter requires C 0.046%, Si 0.001%, Mn 0.09%, P0.0071%, S 0.0038%, and the tapping temperature is 1635°C; after 1 / 3 of the tapping, 2060kg of low-carbon ferromanganese is added first, the oxygen content at the end of the tapping is 554ppm, 150kg of aluminum ingots are added, and finally 500kg of lime + 50kg of fluorite are added for slag washing. No slag is discharged during the tapping process, and the argon gas is turned off after the converter furnace after the tapping is completed;

[0037] (3) LF refining: LF refining furnace enters the station and supplies power for 3 minutes before adding 600kg of high-basicity refined slag for slagging. The basicity of the final slag is 5.4. After 5 minutes, 80kg of calcium carbide deoxidation is started. After the first power supply, the slag is dipped and the slag color is observed. The slag sample is white slag. The second time, 40kg of calcium carbide deoxidation is used; medium-carbon ferromanganese is added according to the composition for alloy fine-tuning; in the later stage, 10-20kg of calcium carbide deoxidation is used again, and the color of the steel-out slag is white slag; the oxygen content at the end of LF refining is 7.8ppm, and the steel-out temperature is 1636℃; 660m of low-aluminum, low-nitrogen ferrotitanium cored wire is fed at a speed of 3-3.5m / s from steel-out to the wire feeding position, and finally ferroboron is added;

[0038] (4) After the LF titanium wire is fed, the molten steel is soft-blown. The appropriate argon gas is adjusted to make the molten steel surface creep slightly without exposing the molten steel surface. The argon gas pressure is controlled at 0.26 / 0.25MPa to ensure the soft-blowing effect. The soft-blowing time is 16 minutes.

[0039] (5) After the soft blowing is completed, the steel is hoisted to cast a 180 mm × 240 mm square billet. The casting process is protected and cast in an integral tank. There is no husk turning phenomenon in the impact zone, and the final titanium content is stably controlled at 0.137%. The chemical composition of the finished product is: C 0.077%, Si 0.026%, Mn 1.666%, P0.0081%, S 0.0017%, Ni 0.357%, Cr0.021%, Cu 0.0165%, Al 0.0097%, B0.0050%, Ti 0.137%, and the balance is slag.

[0040] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A smelting method for low-carbon, low-silicon and high-titanium special welding, characterized in that: The steps are as follows: (1) Pretreatment of molten iron for desulfurization; (2) Converter smelting, control the final tapping composition and tapping temperature of the converter, perform deoxidation and alloying during tapping, add 18-20 kg / t low carbon ferromanganese after 1 / 3 of the tapping, then add 1.3-1.80 kg / t aluminum ingots according to the final oxygen content, and finally add slag making material for slag washing; (3) LF refining: After the LF refining furnace enters the station and supplies power, high-basicity refining slag is added for slagging within a minute. The basicity of the final slag is required to be controlled between 4 and 6. After b minutes, calcium carbide deoxidation is started to ensure that the color of the refined slag sample is white slag; oxygen is determined at the end of LF refining, and the oxygen content is controlled within 10ppm, and the oxygen determination temperature is greater than 1620℃; after the temperature and composition are qualified, 5.9-6.5m / t low-aluminum and low-nitrogen titanium iron cored wire is fed at a speed of 3-3.5m / s to the wire feeding position, and finally ferroboron is added; (4) After the LF titanium wire is fed, the molten steel is soft-blown. The appropriate argon gas is adjusted to make the molten steel surface creep slightly without exposing the molten steel surface. The argon gas pressure is controlled at 0.2-0.4MPa to ensure the soft-blowing effect. The soft-blowing time is ≥10min. (5) After the soft blowing is completed, the steel is hoisted to cast 180mm×240mm square billets. The casting process is protected and cast in an integral tank. The impact zone should not have the phenomenon of rice husk turning. The final titanium content is stably controlled between 0.11% and 0.15%.

2. The smelting method of a low-carbon, low-silicon, high-titanium special welding according to claim 1 is characterized in that: The step (1) uses the KR stirring method to pre-treat the molten iron for desulfurization. The molten iron composition requirement is S≤0.010%. The slag removal operation ensures that the slag is clean and there is no obvious slag block.

3. The smelting method of a low-carbon, low-silicon, high-titanium special welding according to claim 1, characterized in that: Step 2) The target composition requirements of the converter final steel tapping are P≤0.012%, S≤0.015%, and the steel tapping temperature is ≥1600°C. The order and weight of deoxidation and alloying during steel tapping are as follows: after 1 / 3 of the steel is tapped, 2000-2100kg of low-carbon ferromanganese and 340kg of nickel alloy are first added, and then aluminum ingots are added according to the final oxygen content: when the final oxygen content is within 500ppm, 140kg of aluminum ingots are added, when the final oxygen content is 500-700ppm, 160kg of aluminum ingots are added, and when the final oxygen content is 700-900ppm, 180kg of aluminum ingots are added; finally, 500kg of lime and 50kg of fluorite are added for slag washing to ensure the slag melting effect. Slag is strictly prohibited during the steel tapping process, and argon gas is turned off after the converter furnace after the steel tapping is completed.

4. The smelting method of a low-carbon, low-silicon, high-titanium special welding according to claim 1, characterized in that: Step (3) The LF refining furnace is supplied with power for 3 minutes and 550-650kg of high basicity refined slag is added for slagging. The basicity of the final refined slag is controlled between 4 and 6. Calcium carbide deoxidation is started 5 minutes later. The first deoxidation amount is controlled at 80-100kg according to the Al content after the furnace. After the first power supply, the slag is dipped and the slag color is observed. If the slag sample is yellow-white or white slag, the second deoxidation amount is controlled at 20-40kg; medium carbon ferromanganese is added according to the composition to fine-tune the alloy; calcium carbide deoxidation is used again in the middle and late stages, and the deoxidation amount is controlled at 10-20kg to ensure that the color of the steel-out slag is white slag; LF refining end point oxygen is determined, the oxygen content is controlled to be within 20ppm, the oxygen determination temperature is greater than 1620℃, and the steel-out temperature is 1630-1640℃. After the temperature and composition are qualified, 650-700m of low-aluminum, low-nitrogen titanium-iron cored wire is fed to the wire feeding position at a speed of 3-3.5m / s, and finally ferroboron is added.

5. The smelting method of a low-carbon, low-silicon, high-titanium special welding according to claim 1, characterized in that: After the soft blowing in step (5) is completed, the steel is hoisted to cast a 180mm×240mm square billet. The casting process is protected throughout the casting process. The temperature of the tundish is controlled at 1560-1565°C, the pulling speed is controlled at 1.10m / min, and the final titanium content is stably controlled between 0.11% and 0.15%, with an average of 0.13%.