Production method of 70KG-grade welding wire steel wire rod based on rare earth microalloying

Abstract

The invention discloses a production method of a 70KG-grade welding wire steel wire rod based on rare earth microalloying, and belongs to the technical field of metal material processing. The method comprises the following steps: step 1, burdening: preparing molten iron, scrap steel and an alloy material according to target component requirements; 2, smelting in a converter; thirdly, LF refining is carried out, the refining temperature is controlled to be 1580-1620 DEG C, the refining time is 30-40 minutes, and therefore it is guaranteed that components of molten steel are uniform, and inclusions fully float upwards; fourthly, continuous casting is conducted; 5, rolling is conducted, specifically, the casting blank is heated to 1100-1150 DEG C, and rolling is conducted after heat preservation is conducted for a period of time; the rolling process is divided into a rough rolling stage, an intermediate rolling stage and a finish rolling stage, the finish rolling temperature is controlled to be 850-900 DEG C, and finally, the rolled wire rod is cooled, so that the wire rod obtains a proper microscopic structure. Through reasonable component design and process control, the strength, toughness, welding performance and crack resistance of the welding wire steel wire rod are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to a production method of a 70KG-grade welding wire steel wire rod based on rare earth microalloying. Background Art

[0002] With the rapid development of modern industry, especially the widespread application of steel structures in construction, bridges, and machinery manufacturing, the performance requirements for welding materials are becoming increasingly higher. As an important welding material, 70kg-grade welding steel wire rod must possess excellent strength, toughness, welding process performance, and crack resistance.

[0003] Currently, traditional 70kg-grade welding steel wire rod production methods have limitations in composition design and process control. Composition-wise, they primarily rely on conventional alloying elements such as manganese, silicon, and titanium for strengthening and toughening. However, these methods are limited in controlling inclusions and strengthening grain boundaries, leaving the overall performance of the steel in need of further improvement. While the converter process offers advantages such as high production efficiency and low cost, there is still room for improvement in controlling molten steel purity and uniform distribution of alloying elements.

[0004] Due to their unique physical and chemical properties, rare earth elements (REs) can purify molten steel, modify inclusions, and refine grain size in steel. Applying RE microalloying technology to the production of 70kg-grade welding steel wire rods promises to address issues inherent in traditional production methods and improve the overall performance of the steel. However, a mature process system for the specific application of RE microalloying in the production of this grade of welding steel wire rod, including the dosage and timing of RE addition, and its coordination with other alloying elements, has yet to be established. Summary of the Invention

[0005] The purpose of the present invention is to provide a production method of 70KG grade welding wire steel wire rod based on rare earth microalloying, which improves the strength, toughness, welding performance and crack resistance of the welding wire steel wire rod through reasonable composition design and process control.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for producing a 70KG-grade welding wire steel wire rod based on rare earth microalloying, comprising the following steps:

[0008] Step 1: Ingredients

[0009] According to the target composition requirements, molten iron, scrap steel, and alloy material are prepared; the chemical composition of the welding steel wire rod is as follows by mass percentage: C: 0.05%-0.12%, Si: 0.15%-0.35%, Mn: 1.20%-1.60%, P≤0.025%, S≤0.015%, RE: 0.010%-0.030%, Ti: 0.015%-0.035%, and the balance is Fe and unavoidable impurities;

[0010] Step 2: Converter smelting

[0011] The prepared molten iron and scrap steel are added to the converter for smelting. The oxygen blowing intensity and blowing time are controlled to ensure that the carbon, silicon, manganese and other elements in the molten steel reach the initial target range. In the later stage of blowing, appropriate amounts of lime and dolomite slag-forming materials are added to adjust the slag composition and improve the dephosphorization and desulfurization effects.

[0012] Step 3: LF Refining

[0013] The molten steel after converter smelting is poured into the LF refining furnace for heating, deoxidation, desulfurization and alloying. First, aluminum particles are added for deoxidation to reduce the oxygen content in the molten steel to an appropriate range. Then, ferromanganese and ferrosilicon alloy materials are added to adjust the manganese and silicon contents in the molten steel. Then, rare earth alloys are added during the refining process. The amount of rare earth alloy added is calculated and determined based on the weight of the molten steel and the target RE content. The addition time is mid-refining. The rare earth alloy is stirred evenly to fully dissolve and diffuse the rare earth elements, thereby purifying the molten steel and deteriorating inclusions. At the same time, the refining temperature is controlled at 1580-1620°C and the refining time is 30-40 minutes to ensure uniform composition of the molten steel and sufficient floating of inclusions.

[0014] Step 4: Continuous Casting

[0015] The refined molten steel is poured into the crystallizer through the tundish for continuous casting to form a billet. The cooling intensity of the crystallizer, the billet drawing speed, and the water spraying system in the secondary cooling zone are controlled to ensure that the billet has a good solidification structure and avoid cracks and shrinkage defects. The cross-sectional dimensions of the billet are determined according to the subsequent rolling process.

[0016] Step 5: Rolling

[0017] The ingot is heated to 1100-1150℃, kept warm for a period of time and then rolled; the rolling process is divided into rough rolling, intermediate rolling and finishing rolling stages, and the ingot is rolled into wire rod of target size through reasonable hole design and rolling speed control; during the rolling process, the final rolling temperature is controlled at 850-900℃ to ensure that the wire rod has good mechanical properties and structural uniformity; finally, the rolled wire rod is cooled, and the Stelmor controlled cooling process is adopted to control the cooling rate and cooling temperature so that the wire rod obtains a suitable microstructure.

[0018] Furthermore, the cross-sectional dimensions of the ingot are 150 mm×150 mm.

[0019] Furthermore, the structure of the wire rod is ferrite + pearlite structure.

[0020] Further, converter smelting: molten iron and scrap steel are added to the converter, and the oxygen blowing intensity is 3.5m 3 / (t·min), blowing time 15 minutes; in the later stage of blowing, 8kg / t steel of lime and 5kg / t steel of dolomite are added to control the slag basicity R=3.0, and the dephosphorization rate reaches more than 90%.

[0021] Further, LF refining: After the molten steel is poured into the LF refining furnace, 0.5kg / t of aluminum particles are added for deoxidation, and then 15kg / t of ferromanganese and 8kg / t of ferrosilicon are added to adjust the composition. In the middle of refining, 0.2kg / t of rare earth alloy is added. The refining temperature is controlled at 1600℃ and the refining time is 35 minutes, so that the RE content in the molten steel reaches 0.020% and the composition is uniform.

[0022] Furthermore, continuous casting: using a crystallizer with a cross-sectional size of 150mm×150mm and a crystallizer cooling water volume of 150m 3 / h, the billet drawing speed is 1.5m / min, the water spraying pressure in the secondary cooling zone is 0.3MPa, and the billet with good surface quality is obtained.

[0023] Further, rolling: the ingot is heated to 1120°C, kept warm for 2 hours, the rough rolling temperature is 1100°C, the final rolling temperature is 880°C, the Stelmor controlled cooling process is adopted, the cooling rate is 10°C / s, and after cooling to 500°C, it is coiled to obtain 70KG grade welding wire steel wire rod.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] 1. The addition of rare earth elements can purify molten steel, reduce harmful impurities such as sulfur and oxygen, and improve the purity of the steel. At the same time, rare earth elements react with inclusions in the steel, changing the shape and distribution of the inclusions from coarse, brittle inclusions to fine, spherical or spindle-shaped inclusions, thereby improving the toughness and crack resistance of the steel.

[0026] 2. Reasonable composition design and process control make the welding wire steel wire rod have a good balance of strength and toughness. Through the synergistic effect of rare earth microalloying and other alloying elements, the grains are refined, the grain boundaries are strengthened, and the mechanical properties of the steel are improved.

[0027] 3. The use of converter technology combined with LF refining and advanced processes such as continuous casting and rolling has high production efficiency and low cost, making it suitable for large-scale industrial production. At the same time, strict process control ensures uniform composition and dense structure of molten steel, improving the quality stability of wire rod. DETAILED DESCRIPTION

[0028] Example 1

[0029] Ingredients: Prepare, by mass percentage, molten iron (C: 4.0%, Si: 1.2%, Mn: 0.5%, P: 0.015%, S: 0.010%), scrap steel (C: 0.2%, Si: 0.3%, Mn: 0.8%, P: 0.020%, S: 0.012%), and alloying materials including ferromanganese, ferrosilicon, rare earth alloy (RE content 99%), and ferrotitanium. Target chemical composition: C: 0.08%, Si: 0.25%, Mn: 1.40%, P ≤ 0.025%, S ≤ 0.015%, RE: 0.020%, Ti: 0.025%, with the balance being Fe and unavoidable impurities.

[0030] Converter smelting: molten iron and scrap steel are added to the converter, and the oxygen blowing intensity is 3.5m 3 / (t·min), blowing time 15 minutes. In the later stage of blowing, 8kg / t of steel and 5kg / t of dolomite are added to control the slag basicity R=3.0, the dephosphorization rate reaches above 90%, and the final carbon content is 0.08%, phosphorus content 0.020%, and sulfur content 0.012%.

[0031] LF refining: After the molten steel is poured into the LF refining furnace, 0.5kg / t of aluminum particles are added for deoxidation, and then 15kg / t of ferromanganese and 8kg / t of ferrosilicon are added to adjust the composition. In the middle of refining, 0.2kg / t of rare earth alloy is added. The refining temperature is controlled at 1600℃ and the refining time is 35 minutes to make the RE content in the molten steel reach 0.020% and the composition is uniform.

[0032] Continuous casting: Use a crystallizer with a cross-section size of 150mm×150mm and a crystallizer cooling water volume of 150m 3 / h, the casting speed is 1.5m / min, the water spraying pressure in the secondary cooling zone is 0.3MPa, and the casting billet with good surface quality is obtained.

[0033] Rolling: The ingot is heated to 1120℃ and kept warm for 2 hours. The rough rolling temperature is 1100℃ and the final rolling temperature is 880℃. The Stelmor controlled cooling process is adopted with a cooling rate of 10℃ / s. After cooling to 500℃, the ingot is coiled to obtain 70KG grade welding wire steel wire rod.

[0034] Comparative Example 1

[0035] Compared with Example 1, Comparative Example 1 does not add rare earth alloy, and other process parameters and component designs are basically the same.

[0036] Comparative Example 2

[0037] Compared with Example 1, Comparative Example 2 uses niobium alloy (Nb content 50%) instead of rare earth alloy, and the addition amount is 0.030% (calculated as Nb). Other process parameters and composition designs are basically the same.

[0038] Comparative Example 3

[0039] Compared with Example 1, in the LF refining process of Comparative Example 3, the refining temperature is controlled at 1560° C., the refining time is 25 minutes, and other process parameters and component designs are basically the same.

[0040] Performance Testing

[0041] The performance of the welding steel wire rods produced in Example 1 and Comparative Examples 1-3 was tested, and the results are shown in the following table:

[0042]

[0043] The data in the table show that the welding steel wire rod produced in Example 1 outperforms Comparative Examples 1-3 in mechanical properties such as tensile strength, yield strength, and impact toughness, and has the lowest weld crack rate, demonstrating that rare earth microalloying and reasonable process parameters can significantly improve the overall performance of welding steel wire rod. Comparative Example 1, which does not add rare earths, suffers from poor inclusion morphology and distribution in the steel, leading to decreased mechanical and weldability. Comparative Example 2, which uses a niobium alloy instead of rare earths, while exhibiting some strengthening effects, is less effective than rare earths in terms of inclusion deterioration and purifying molten steel. In Comparative Example 3, insufficient refining temperature and time result in inadequate dissolution and diffusion of the rare earth elements, resulting in incomplete inclusion flotation, thus affecting the steel's performance.

[0044] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying, characterized in that: The steps include: Step 1: Ingredients According to the target composition requirements, molten iron, scrap steel, and alloy material are prepared; the chemical composition of the welding steel wire rod is as follows by mass percentage: C: 0.05%-0.12%, Si: 0.15%-0.35%, Mn: 1.20%-1.60%, P≤0.025%, S≤0.015%, RE: 0.010%-0.030%, Ti: 0.015%-0.035%, and the balance is Fe and unavoidable impurities; Step 2: Converter smelting The prepared molten iron and scrap steel are added to the converter for smelting. The oxygen blowing intensity and blowing time are controlled to ensure that the carbon, silicon and manganese elements in the molten steel reach the initial target range. In the later stage of blowing, appropriate amounts of lime and dolomite slag-forming materials are added to adjust the slag composition and improve the dephosphorization and desulfurization effects. Step 3: LF Refining The molten steel after converter smelting is poured into the LF refining furnace for heating, deoxidation, desulfurization and alloying. First, aluminum particles are added for deoxidation to reduce the oxygen content in the molten steel to an appropriate range. Then, ferromanganese and ferrosilicon alloy materials are added to adjust the manganese and silicon contents in the molten steel. Then, rare earth alloys are added during the refining process. The amount of rare earth alloy added is calculated and determined based on the weight of the molten steel and the target RE content. The addition time is mid-refining. The rare earth alloy is stirred evenly to fully dissolve and diffuse the rare earth elements, thereby purifying the molten steel and deteriorating inclusions. At the same time, the refining temperature is controlled at 1580-1620°C and the refining time is 30-40 minutes to ensure uniform composition of the molten steel and sufficient floating of inclusions. Step 4: Continuous Casting The refined molten steel is poured into the crystallizer through the tundish for continuous casting to form a billet. The cooling intensity of the crystallizer, the billet drawing speed, and the water spraying system in the secondary cooling zone are controlled to ensure that the billet has a good solidification structure and avoid cracks and shrinkage defects. The cross-sectional dimensions of the billet are determined according to the subsequent rolling process. Step 5: Rolling The ingot is heated to 1100-1150℃ and kept warm for a period of time before rolling. The rolling process is divided into rough rolling, intermediate rolling and finishing rolling stages. Through reasonable pass design and rolling speed control, the ingot is rolled into wire rod of target size. During the rolling process, the final rolling temperature is controlled at 850-900℃ to ensure that the wire rod has good mechanical properties and structural uniformity; finally, the rolled wire rod is cooled, and the Stelmor controlled cooling process is adopted to control the cooling rate and cooling temperature so that the wire rod obtains a suitable microstructure.

2. The method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying according to claim 1, characterized in that: The cross-sectional dimensions of the ingot are 150 mm × 150 mm.

3. The method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying according to claim 1, characterized in that: The structure of the wire rod is ferrite+pearlite structure.

4. The method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying according to claim 1, characterized in that: Converter smelting: molten iron and scrap steel are added to the converter, and the oxygen blowing intensity is 3.5m 3 / (t·min), blowing time 15 minutes; in the later stage of blowing, 8kg / t steel of lime and 5kg / t steel of dolomite are added to control the slag basicity R=3.0, and the dephosphorization rate reaches more than 90%.

5. The method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying according to claim 1, characterized in that: LF refining: After the molten steel is poured into the LF refining furnace, 0.5kg / t of aluminum particles are added for deoxidation, and then 15kg / t of ferromanganese and 8kg / t of ferrosilicon are added to adjust the composition. In the middle of refining, 0.2kg / t of rare earth alloy is added. The refining temperature is controlled at 1600℃ and the refining time is 35 minutes to make the RE content in the molten steel reach 0.020% and the composition is uniform.

6. The method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying according to claim 1, characterized in that: Continuous casting: Use a crystallizer with a cross-section size of 150mm×150mm and a crystallizer cooling water volume of 150m 3 / h, the billet drawing speed is 1.5m / min, the water spraying pressure in the secondary cooling zone is 0.3MPa, and the billet with good surface quality is obtained.

7. The method for producing 70KG grade welding wire steel wire rod based on rare earth microalloying according to claim 1, characterized in that: Rolling: The ingot is heated to 1120℃ and kept warm for 2 hours. The rough rolling temperature is 1100℃ and the final rolling temperature is 880℃. The Stelmor controlled cooling process is adopted with a cooling rate of 10℃ / s. After cooling to 500℃, the ingot is coiled to obtain 70KG grade welding wire steel wire rod.

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