Preparation method for controlling cracks of alloy steel produced by CSP

Abstract

The invention discloses a preparation method for controlling cracks of alloy steel produced on a CSP production line, and belongs to the technical field of steelmaking continuous casting. The alloy steel is poured through a CSP funnel type crystallizer, the casting speed ranges from 4.0 m / mi < n > to 5.0 m / mi < n >, and the alloy steel comprises, by mass, 0.06%-0.10% of T , 0.2%-0.4% of Si, 0.5%-1.8% of Mn, smaller than or equal to 0.8% of Cr, smaller than or equal to 0.5% of N , smaller than or equal to 0.7% of Cu, smaller than or equal to 0.06% of Nb, smaller than or equal to 0.2% of V and smaller than or equal to 0.1% of Mo. Molten steel components can relate to two or more combinations of the alloy elements, and the mass fraction of the alloy is larger than or equal to 1.6%. And casting powder matched with alloy components and casting speed is adopted. By adopting suitable casting powder and crystallizer parameter control, the quality defects such as edge cracks and longitudinal cracks of the casting blank are effectively avoided, the continuous casting process is ensured to be smooth, and the casting blank with good quality is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking and continuous casting, and in particular relates to a preparation method for controlling cracks in alloy steel produced by CSP. Background Art

[0002] The casting speed of the CSP continuous casting and rolling production line can reach 4.0-5.0 m / min. It has the characteristics of high efficiency and low cost. It can produce carbon structural steel, low alloy structural steel, alloy high-strength steel and other steels. As alloy elements such as Ti, Cu, Ni, Cr are added to the molten steel, the compounds formed by them in combination with elements such as C and N precipitate from the grain boundaries, greatly increasing their crack sensitivity. In addition, due to the special structure of the CSP funnel-shaped crystallizer, high casting speeds are prone to slag rolling and poor slag removal, and the production of alloy steel is prone to edge cracks or longitudinal cracks. By using protective slag and crystallizer parameter control suitable for the composition of alloy steel, the CSP production line can produce alloy steel products with qualified surface quality, taking into account both efficiency and quality requirements.

[0003] Chinese patent application with publication number CN 114012050 A discloses a CSP thin slab titanium steel special continuous casting mold protection slag and its preparation method. The titanium content in the steel is 0.02-0.06wt%, which is less than the maximum titanium content of 0.1% in the present invention. It has higher crack sensitivity and is more difficult to control.

[0004] A Chinese patent application with publication number CN 108823492 A discloses a method for producing high-alloy high-strength peritectic steel using a CSP thin plate continuous casting machine, wherein the titanium content in the steel is 0.015-0.03wt%. The maximum titanium content of the present invention reaches 0.1%, and no crack-sensitive element Cu is added. The maximum Cu content added in the present invention reaches 0.7%, and steel with high crack sensitivity such as atmospheric corrosion resistance can be produced.

[0005] Chinese patent application with publication number CN 107186186 A discloses a method for casting atmospheric corrosion resistant steel by a CSP continuous casting machine. The Ba element is not added to the protective slag composition, so the melting temperature of the slag is relatively high, and the fluidity of the slag is poorer than that of the present invention. In addition, the superheat of the molten steel in the invention is only 10°C to 20°C, which is not as high as that of the present invention. The superheat is too low, which is difficult to control and is not conducive to the removal of inclusions. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing alloy steel with controlled cracks produced by CSP, so as to produce alloy steel products with qualified surface quality.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention discloses a method for preparing a controlled crack of alloy steel produced by CSP, wherein the chemical composition of the alloy steel is, by mass percentage, Ti: 0.06%-0.10%, Si: 0.2%-0.4%, Mn: 0.5%-1.8%, Cr: ≤0.8%, Ni: ≤0.5%, Cu: ≤0.7%, Nb: ≤0.06%, V: ≤0.2%, Mo: ≤0.1%, and the rest is Fe and unavoidable impurities;

[0009] During the production process, the composition of the molten steel may involve two or more combinations of the above alloying elements, with the alloy mass fraction ≥ 1.6%; the superheat range of the molten steel is controlled between 15°C and 35°C;

[0010] In the CSP production line, a mold slag matching the alloy composition and casting speed is used. The chemical composition of the mold slag is calculated by mass percentage as follows: SiO 2 :28%-32%, CaO: 28%-35%, Al 2 O 3 : 4%-6%, MgO: 1%-1.5%, Ba 2 O 3 :0.9%-1.2%,Fe 2 O 3 :0.4%-0.6%, MnO: 2.5%-3.0%, Na 2 O: 7.5%-9.5%, K 2 O: 0.18%-0.26%, F: 7.5%-9.0%, C: 7.5%-9.5%, the balance is unavoidable impurities;

[0011] The alloy steel is cast in a CSP funnel-shaped crystallizer with a casting speed range of 4.0-5.0 m / min; the water flow rate on the wide side of the crystallizer is 5700-6300 L / min, the water flow rate on the narrow side is 200-240 L / min, the taper on the left and right sides of the crystallizer is 0.15%-1.0%, and the heat flow ratio range is 60%-80%.

[0012] Furthermore, the protective slag has the following characteristics: density: 0.65 g / ml-0.80 g / ml, melting point: 1045°C-1123°C, viscosity: 1.35 Poise-1.7 Poise, and binary slag basicity: 1.01-1.25.

[0013] Furthermore, by controlling the water flow on the narrow and wide sides of the crystallizer and adjusting the taper on the left and right sides of the crystallizer, the heat flow ratio between the narrow and wide sides is controlled within the range of 60%-80%, thereby achieving the purpose of controlling longitudinal cracks and edge cracks.

[0014] Furthermore, the chemical composition of the mold slag is calculated by mass percentage as follows: SiO 2:30.9%, CaO: 31.6%, Al 2 O 3 :4.90%, MgO: 1.25%, Ba 2 O 3 :1.02%,Fe 2 O 3 :0.47%, MnO: 2.86%, Na 2 O: 8.69%, K 2 O: 0.23%, F: 8.25%, C: 8.43%, and the remainder are inevitable impurities.

[0015] Furthermore, the chemical composition of the mold slag is calculated by mass percentage as follows: SiO 2 :30.2%, CaO: 32.4%, Al 2 O 3 :4.25%, MgO: 1.33%, Ba 2 O 3 :1.11%,Fe 2 O 3 :0.58%, MnO: 2.91%, Na 2 O: 8.98%, K 2 O: 0.25%, F: 7.80%, C: 9.02%, and the remainder are inevitable impurities.

[0016] Furthermore, the chemical composition of the mold slag is calculated by mass percentage as follows: SiO 2 :28.7%, CaO: 33.8%, Al 2 O 3 :4.67%, MgO: 1.54%, Ba 2 O 3 :1.20%,Fe 2 O 3 :0.42%, MnO: 2.63%, Na 2 O: 9.46%, K 2 O: 0.26%, F: 8.64%, C: 7.68%, and the remainder are inevitable impurities.

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

[0018] The CSP thin slab alloy steel continuous casting crystallizer protective slag provided by the present invention has the characteristics of moderate basicity, low melting point and high viscosity, which is conducive to the adsorption of inclusions in molten steel and prevents slag rolling; the low melting point is conducive to the vitrification of molten slag, and it is not easy to form slag strips or bridges, thereby improving the lubrication of the slab surface; the high viscosity increases the thickness of the slag film, the slag film is more uniform, the thermal resistance is stable, and the heat transfer efficiency of the protective slag is reduced, thereby slowing down the cooling intensity. At the same time, by adjusting the water flow rate of the crystallizer and the taper on the left and right sides, the heat flow ratio is controlled within a reasonable range, thereby reducing the crack incidence rate. CSP casting alloy steel can still run smoothly at a casting speed of 4 to 5 m / min. DETAILED DESCRIPTION

[0019] The present invention will be further described in conjunction with specific embodiments.

[0020] Example:

[0021] (1) The chemical composition of the alloy steel in each embodiment is shown in Table 1.

[0022] Table 1: Chemical composition of each example product (Wt%)

[0023]

[0024] The protective slag composition and casting machine parameters used in the alloy steel of each embodiment are as follows.

[0025] (2) The composition and performance parameters of the protective slag are shown in Table 2.

[0026] Table 2: Composition and performance parameters of protective slag in various examples

[0027]

[0028] (3) Casting machine process control parameters are shown in Table 3.

[0029] Table 3: Casting machine process parameters of various embodiments

[0030]

[0031] Each embodiment adopts the protective slag composition ratio and casting machine process control parameters provided by the present invention, and while ensuring the smooth production of the casting machine, an alloy steel product with no longitudinal cracks or edge cracks and good surface quality is obtained.

[0032] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing controlled cracks in alloy steel produced by CSP, characterized in that: The chemical composition of the alloy steel in terms of mass percentage is: Ti: 0.06%-0.10%, Si: 0.2%-0.4%, Mn: 0.5%-1.8%, Cr: ≤0.8%, Ni: ≤0.5%, Cu: ≤0.7%, Nb: ≤0.06%, V: ≤0.2%, Mo: ≤0.1%, and the rest is Fe and unavoidable impurities; During the production process, the composition of the molten steel involves two or more combinations of the above alloying elements, with the alloy mass fraction ≥ 1.6%; the superheat range of the molten steel is controlled between 15℃-35℃; The CSP production line uses a protective slag that matches the alloy composition and casting speed. The chemical composition of the protective slag is calculated by mass percentage: SiO2: 28%-32%, CaO: 28%-35%, Al2O3: 4%-6%, MgO: 1%-1.5%, Ba2O3: 0.9%-1.2%, Fe2O3: 0.4%-0.6%, MnO: 2.5%-3.0%, Na2O: 7.5%-9.5%, K2O: 0.18%-0.26%, F: 7.5%-9.0%, C: 7.5%-9.5%, and the balance is unavoidable impurities; The alloy steel is cast in a CSP funnel-shaped crystallizer with a casting speed range of 4.0-5.0 m / min; the water flow rate on the wide side of the crystallizer is 5700-6300 L / min, the water flow rate on the narrow side is 200-240 L / min, the taper on the left and right sides of the crystallizer is 0.15%-1.0%, and the heat flow ratio range is 60%-80%.

2. The method for controlling cracks in alloy steel produced by CSP according to claim 1, characterized in that: The protective slag has the following characteristics: density: 0.65 g / ml-0.80 g / ml, melting point: 1045° C.-1123° C., viscosity: 1.35 Poise-1.7 Poise, and binary slag basicity: 1.01-1.

25.

3. The method for controlling cracks in alloy steel produced by CSP according to claim 1, characterized in that: By controlling the water flow on the narrow and wide sides of the crystallizer and adjusting the taper on the left and right sides of the crystallizer, the heat flow ratio between the narrow and wide sides is controlled within the range of 60%-80%, thereby achieving the purpose of controlling longitudinal cracks and edge cracks.

4. The method for controlling cracks in alloy steel produced by CSP according to claim 1, characterized in that: The chemical composition of the protective slag is calculated by mass percentage as follows: SiO2: 30.9%, CaO: 31.6%, Al2O3: 4.90%, MgO: 1.25%, Ba2O3: 1.02%, Fe2O3: 0.47%, MnO: 2.86%, Na2O: 8.69%, K2O: 0.23%, F: 8.25%, C: 8.43%, and the remainder is unavoidable impurities.

5. The method for controlling cracks in alloy steel produced by CSP according to claim 1, characterized in that: The chemical composition of the protective slag is calculated by mass percentage: SiO2: 30.2%, CaO: 32.4%, Al2O3: 4.25%, MgO: 1.33%, Ba2O3: 1.11%, Fe2O3: 0.58%, MnO: 2.91%, Na2O: 8.98%, K2O: 0.25%, F: 7.80%, C: 9.02%, and the remainder is unavoidable impurities.

6. The method for controlling cracks in alloy steel produced by CSP according to claim 1, characterized in that: The chemical composition of the protective slag is calculated by mass percentage as follows: SiO2: 28.7%, CaO: 33.8%, Al2O3: 4.67%, MgO: 1.54%, Ba2O3: 1.20%, Fe2O3: 0.42%, MnO: 2.63%, Na2O: 9.46%, K2O: 0.26%, F: 8.64%, C: 7.68%, and the remainder is unavoidable impurities.

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