Steelmaking production method for producing 600MPa-grade rare earth welding wire steel by adopting vacuum process

Abstract

The invention discloses a steelmaking production method for producing 600MPa-grade rare earth welding wire steel by adopting a vacuum process, which is characterized by comprising the steps of molten iron desulfurization, converter smelting, external refining, vacuum treatment and continuous casting machine, in the production process, rare earth alloy is added at an RH vacuum treatment station, and the rare earth alloy is not added in other process flows; the rare earth welding wire steel comprises the following chemical components in percentage by mass: 0.05 to 0.065 percent of C, 0.80 to 0.89 percent of S i, 1.40 to 1.49 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.0015 to 0.005 percent of Ce, less than or equal to 0.0050 percent of N, less than or equal to 0.0002 percent of H and the balance of Fe and impurities. The method is used for 600MPa-grade rare earth gas shield welding wire steel steelmaking production, and the stability of the rare earth gas shield welding wire steel steelmaking production process is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a steelmaking production method for producing 600 MPa grade rare earth welding wire steel by using a vacuum process. Background Art

[0002] Gas shielded alloy welding wire steel belongs to copper-plated low alloy steel gas shielded welding wire and is mainly used for gas shielded welding. CO2 or argon-rich gas is used as the shielding gas for welding. Gas shielded welding is an arc welding method that uses an external gas as the arc medium and protects the arc and the welding area. Gas shielded solid welding is a high-quality, efficient, and energy-saving welding method, which has been increasingly widely used in the manufacturing industries such as heavy machinery, construction machinery, ships, boilers, and vehicles in China. In recent years, the development speed of gas shielded welding in China has been relatively fast, the consumption of gas shielded welding wire has been increasing, and the market demand for welding wire rod for processing gas shielded welding wire has been rapidly increasing. 600 MPa grade gas shielded welding wire is a commonly used gas shielded welding wire variety abroad. The chemical composition is controlled according to the requirements of the American Welding Society standard AWS A5.18. This welding wire has good arc stability and high weld performance during welding and is widely used abroad. Summary of the Invention

[0003] The purpose of the present invention is to provide a steelmaking production method for producing 600 MPa grade rare earth welding wire steel by using a vacuum process, which is used for the steelmaking production of 600 MPa grade rare earth gas shielded welding wire steel and improves the process stability of the steelmaking production of rare earth gas shielded welding wire steel.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A steelmaking production method for producing 600 MPa grade rare earth welding wire steel by using a vacuum process according to the present invention includes: hot metal desulfurization - converter smelting - secondary refining - vacuum treatment - continuous caster. In the production process, the rare earth alloy is added at the RH vacuum treatment station, and no rare earth alloy is added in other process flows; wherein:

[0006] The hot metal desulfurization controls the stirring head speed at 90 - 120 revolutions per minute, the desulfurizer addition amount at 5.5 - 6.5 Kg / t, the stirring time is greater than 10 min, and the sulfur content after hot metal desulfurization is controlled to less than 0.005%;

[0007] The converter smelting end controls the carbon content at 0.03% ≤ C ≤ 0.05%, and the end temperature is controlled at T ≥ 1620°C;

[0008] In the LF process, aluminum-containing slag-making agent is used to replace calcium carbide and silicon carbide for deoxidation, and ferrosilicon powder is added to assist deoxidation. It is required that the refining white slag time T ≥ 8 min, the refining off-position carbon is controlled between 0.05% - 0.06%, and the LF supply temperature for RH is T ≥ 1600°C;

[0009] During the RH vacuum treatment process, the vacuum treatment time T ≥ 20 min, and stepped vacuum degree control is adopted. After the RH is in place, the first-stage treatment starts. Rare earth alloy is added, and the added amount is calculated based on 40% of the total amount. After adding, the vacuum degree is 8 - 10 KPa, and the circulating gas flow rate is 140 - 180 Nm 3 / h, the circulation time T = 10 min. After the heat treatment time node, it is added using the vacuum feeding system. Rare earth alloy is added again, and the added amount is calculated based on 60% of the total added amount. After adding the rare earth alloy, the second-stage treatment starts, with a vacuum degree of 0.3 KPa and a circulating gas flow rate of 120 - 140 Nm 3 / h, the circulation time T ≥ 10 min. After the time node, a vacuum-breaking negative pressure soft blowing operation is carried out; the soft blowing argon gas flow rate is 20 NL / min, the soft blowing time T ≥ 10 min. After the soft blowing ends, continuous casting is carried out for pouring;

[0010] During the continuous casting process, oxygen burning operation is prohibited for the tundish to ensure self-opening. The tundish uses a tundish covering agent, and the whole process from the tundish to the mold is protected to reduce the secondary oxidation of the molten steel. The immersion nozzle insertion depth is 70 - 90 mm, and the molten steel passing amount through the mold ≤ 5000 tons.

[0011] Furthermore, the addition amount of the desulfurizer is 6 Kg / t.

[0012] Furthermore, the chemical composition of the rare earth welding wire steel by mass percentage is: C 0.05 - 0.065%, Si 0.80 - 0.89%, Mn 1.40 - 1.49%, P ≤ 0.020%, S ≤ 0.015%, Ce 0.0015 - 0.005%, N ≤ 0.0050%, H ≤ 0.0002%, and the rest is Fe and impurities.

[0013] Furthermore, during the converter smelting process, supplementary blowing operation is prohibited. The converter bottom blowing adopts full-process argon blowing. From the start of oxygen supply to 8 min of oxygen supply, the argon blowing amount is 0.05 - 0.08 Nm 3 / min·t, from 8 min of oxygen supply to tapping, the argon blowing amount is 0.08 - 0.10 Nm 3 / min·t.

[0014] Furthermore, during tapping, SiMn alloy deoxidation alloying operation is adopted, and lime is added to the top slag, with the lime addition amount of 3.0 - 3.5 kg / t.

[0015] Furthermore, compared with the production method without vacuum process, the rare earth recovery rate is increased by more than 20.0%.

[0016] Furthermore, when the rare earth addition amount is 50 ppm, the rare earth recovery rate of this method in production is 70.75%, which is increased by 27.0% compared with the rare earth recovery rate of 43.75% of the method without vacuum process.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0018] When producing rare earth shielded welding wire steel by the method of the present invention, the rare earth content in the steel is stable and the continuous casting process runs smoothly. Compared with the production of rare earth shielded welding wire steel by the KR-LD-LF-CC (without vacuum treatment) process, the rare earth recovery rate in the production of rare earth shielded welding wire steel by the method of the present invention is increased and the rare earth recovery rate is stable. Specific embodiments

[0019] In order to more clearly understand the above aspects, features and advantages of the present invention, the present invention will be further described in detail below in conjunction with specific embodiments.

[0020] The KR-LD-LF-RH-CC (vacuum treatment) process route is adopted to produce rare earth shielded welding wire steel.

[0021] For hot metal desulfurization, control the stirring head speed at 90 - 120 r / min, the desulfurizer at about 6 Kg / t, the stirring time greater than 10 min, and control the sulfur content after hot metal desulfurization to below 0.005%.

[0022] At the end of converter smelting, control the carbon content at 0.03% ≤ C ≤ 0.05%, the end point temperature at T ≥ 1620 °C. During the converter smelting process, the make-up blowing operation is prohibited. The bottom blowing of the converter adopts argon blowing throughout the process. From the start of oxygen supply to 8 min of oxygen supply, the argon blowing volume is 0.05 - 0.08 Nm 3 / min·t, and from 8 min of oxygen supply to tapping, the argon blowing volume is 0.08 - 0.10 Nm 3 / min·t. For tapping, adopt the deoxidation alloying operation with SiMn alloy, add lime top slag, and the lime addition amount is 3.0 - 3.5 kg / t.

[0023] In the LF process, replace calcium carbide and silicon carbide for deoxidation with an aluminum-containing slag former, and add ferrosilicon powder to assist in deoxidation. It is required that the refining white slag time T ≥ 8 min, and the off-position carbon during refining is controlled between 0.05% - 0.06%. The temperature supplied by LF to RH is T ≥ 1600 °C.

[0024] During the RH vacuum treatment process, the vacuum treatment time T ≥ 20 min, and adopt stepped vacuum degree control. After RH is in place, start the first-stage heat treatment, add a rare earth alloy with a Ce content of 30%, the addition amount is 6.8 kg, and after adding, the vacuum degree is 8 - 10 KPa, and the circulating gas flow rate is 140 - 180 Nm 3 / h, the circulation time T = 10 min. After the heat treatment time node, use the vacuum feeding system to add, and add the rare earth alloy with a Ce content of 30% again, the addition amount is 10.2 kg. After adding the rare earth alloy, start the second-stage heat treatment, the vacuum degree is 0.3 KPa, and the circulating gas flow rate is 120 - 140 Nm3 / h, the cycle time T ≥ 10 min, and a vacuum-breaking negative pressure soft blowing operation is carried out after the time node. The soft blowing argon gas flow rate is 20 NL / min, and the soft blowing time T ≥ 10 min to ensure the soft blowing effect. After the soft blowing is completed, continuous casting is carried out for pouring.

[0025] During the continuous casting process, oxygen burning operation is prohibited for the tundish to ensure self-opening. The tundish covering agent is used in the tundish, high-quality refractory materials and three major continuous casting parts (nozzle, seat brick, stopper rod) are used. Protective casting is carried out during the continuous casting process to avoid secondary oxidation of the molten steel, and the tundish superheat during the continuous casting process is controlled at 35°C ± 5°C. The immersion nozzle insertion depth is 70 - 90 mm, and the molten steel passing amount in the mold ≤ 5000 tons.

[0026] The composition of the rare earth gas shielded welding wire steel produced by the inventive method is shown in Table 1.

[0027] Table 1 Composition of rare earth gas shielded welding wire steel

[0028]

[0029] When the rare earth gas shielded welding wire steel is produced by the inventive method, the rare earth content in the steel is stable and the continuous casting process proceeds smoothly. Compared with the production of rare earth gas shielded welding wire steel by the KR-LD-LF-CC (without vacuum treatment) process, the rare earth recovery rate in the rare earth gas shielded welding wire steel produced by the inventive method is increased, and the rare earth recovery rate is stable. The comparison effect is shown in Table 2.

[0030] Table 2 Comparison of production data

[0031]

[0032] It can be clearly seen from the comparison of production data that when the rare earth addition amount is 50 ppm, the rare earth recovery rate of the rare earth gas shielded welding wire steel produced by the inventive method is 70.75%, compared with 43.75% of the comparative method, the rare earth recovery rate is increased by 27.0%, and the effect of the inventive method is obvious.

[0033] The properties of the rare earth gas shielded welding wire steel wire rod are shown in Table 3.

[0034] Table 3 Mechanical properties of wire rod

[0035]

[0036]

[0037] The mechanical properties of the rare earth gas shielded welding wire steel wire rod produced by the inventive method fully meet the requirements.

[0038] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the spirit of the present invention's design, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A steelmaking production method for producing 600MPa grade rare earth welding wire steel using a vacuum process, characterized in that: include: In the production process of hot metal desulfurization - converter smelting - refining outside the furnace - vacuum treatment - continuous casting machine, the rare earth alloy is added at the RH vacuum treatment station, and no rare earth alloy is added in other process flows; among which: The speed of the stirring head is controlled at 90-120 rpm for hot metal desulfurization, the amount of desulfurizer added is 5.5-6.5 kg / t, the stirring time is greater than 10 minutes, and the sulfur content of the hot metal after desulfurization is controlled to be below 0.005%; The end point of converter smelting is controlled at carbon content 0.03%≤C≤0.05%, and the end point temperature is controlled at T≥1620℃; In the LF process, aluminum-containing slag-making agent is used to replace calcium carbide and silicon carbide deoxidation, and ferrosilicon powder is added to assist deoxidation. The refining time of white slag is required to be T≥8min, the refining off-site carbon is controlled between 0.05%-0.06%, and the LF supply RH temperature is T≥1600℃; During the RH vacuum treatment process, the vacuum treatment time T≥20min, and the step-by-step vacuum control is adopted; after the RH is in place, the first stage of treatment begins, and the rare earth alloy is added. The amount added is calculated based on 40% of the total amount. After adding, the vacuum degree is 8-10KPa, and the circulating gas flow rate is 140-180Nm 3 / h, cycle time T = 10min, after the heat treatment time node, use the vacuum feeding system to add, add rare earth alloy again, the amount added is calculated as 60% of the total amount added, after adding rare earth alloy, start the second stage of treatment, vacuum degree 0.3KPa, circulation gas flow rate 120-140Nm 3 / h, cycle time T≥10min, after the time node, vacuum breaking negative pressure soft blowing operation is adopted; soft blowing argon flow rate is 20NL / min, soft blowing time T≥10min, after the soft blowing is completed, continuous casting is carried out for pouring; In the continuous casting process, oxygen burning operation is prohibited in the ladle to ensure self-opening. A covering agent is used in the tundish. The entire process from the tundish to the crystallizer is protected to reduce the secondary oxidation of the molten steel. The insertion depth of the invasive nozzle is 70 to 90 mm, and the amount of steel passing through the crystallizer is ≤5,000 tons.

2. The steelmaking production method for producing 600MPa grade rare earth welding wire steel using vacuum process according to claim 1, characterized in that: The amount of desulfurizer added is 6Kg / t.

3. The steelmaking production method for producing 600MPa grade rare earth welding wire steel using vacuum process according to claim 1, characterized in that: The chemical composition of the rare earth welding wire steel by mass percentage is: C0.05-0.065%, Si 0.80-0.89%, Mn 1.40-1.49%, P≤0.020%, S≤0.015%, Ce0.0015-0.005%, N≤0.0050%, H≤0.0002%, and the rest is Fe and impurities.

4. The steelmaking production method for producing 600MPa grade rare earth welding wire steel using vacuum process according to claim 1, characterized in that: The converter smelting process requires that supplementary blowing is prohibited. The converter bottom blowing adopts argon blowing throughout the whole process. The argon blowing amount is 0.05-0.08Nm from the start of oxygen supply to 8 minutes of oxygen supply. 3 / min·t, oxygen supply for 8min until carbon pulling, argon blowing volume 0.08-0.10Nm 3 / min·t.

5. The steelmaking production method for producing 600MPa grade rare earth welding wire steel using vacuum process according to claim 1, characterized in that: The steelmaking process adopts SiMn alloy deoxidation and alloying operation, and lime is added to the top slag. The amount of lime added is 3.0-3.5kg / t.

6. The steelmaking production method for producing 600MPa grade rare earth welding wire steel using vacuum process according to claim 1, characterized in that: Compared with the production method without vacuum process, the rare earth recovery rate is increased by more than 20.0%.

7. The steelmaking production method for producing 600MPa grade rare earth welding wire steel using vacuum process according to claim 1, characterized in that: When the rare earth addition amount is 50 ppm, the rare earth yield of the method is 70.75%, which is 27.0% higher than the rare earth yield of 43.75% of the non-vacuum process method.

Images