Width control and edge crack-free rolling method for 410S stainless steel continuous casting slab

Abstract

The invention belongs to the technical field of stainless steel, and particularly relates to a 410S stainless steel continuous casting slab width control and edge crack-free rolling method. The width control and edge crack-free rolling method for the 410S stainless steel continuous casting sheet billet comprises the following steps: S1, smelting; s2, continuous casting; and S3, hot rolling. According to the rolling method, it can be guaranteed that the error between the width of the finally-manufactured 410S stainless steel plate blank and the target width is kept within the range of + / -5 mm, and the manufactured steel coil does not have the problems of edge cracking and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of stainless steel, and particularly relates to a 410S stainless steel continuous casting slab width control and edge crack-free rolling method. BACKGROUND

[0002] 410S belongs to ferritic stainless steel. When the 410S is continuously cast, about 1% liquid shrinkage occurs from liquid metal to liquidus temperature, and 3-4% solidification shrinkage occurs from liquidus to solidus, and about 7-8% shrinkage occurs from solid state to room temperature. However, because there is almost no phase transition during the solidification of the ferritic stainless steel, there is no phase transition shrinkage caused by the phase transition from high-temperature ferrite delta to austenite gamma, and the total shrinkage of the casting blank is small. In addition, compared with austenitic stainless steel, the high-temperature thermal strength of the ferritic stainless steel is low, and after the mold is discharged, the blank is expanded due to the influence of the static pressure of the molten steel, the width is greater than the mold width, and the width is unevenly controlled due to the influence of multiple factors such as the composition of the molten steel, the intensity of the secondary cooling water, the casting temperature, the continuous casting speed and the like, and the width control stability is a problem in the industry.

[0003] Although 410S belongs to ferritic stainless steel, there are two-phase structures (austenite + ferrite) at high temperatures, and when hot rolling, cracks are easily generated at the phase boundary due to the incoordination of the two-phase deformation, the thermal plasticity of the steel is reduced, and edge cracks are easily generated during rolling. The document "Control of the Width Size of Ferritic Stainless Steel Continuous Casting Slab" and the like have studied the width of the 410S stainless steel casting blank, but only the qualitative influence direction is given. The document "Research on the Width Control of 410S Stainless Steel Continuous Casting Blank" only gives the quantitative relationship of the influence of a single factor, and the speed control range is 0.95-1.0 m / min, the speed range is narrow, which seriously affects the actual production capacity and the control difficulty is high, in addition, the relevance of each influencing factor is not reflected in the research, however, the actual slab width is the result of the joint action of multiple factors. The document "Analysis of Edge Crack Reasons of SUS410S Stainless Steel and Process Research" only gives the qualitative analysis of the reasons for the edge cracks, and can only reduce the occurrence of the edge cracks, but cannot realize the edge crack-free control.

[0004] Therefore, it is urgent to develop a rolling method which can realize the width control of the stainless steel continuous casting slab and make the prepared slab edge crack-free. SUMMARY

[0005] The present application aims to provide a 410S stainless steel continuous casting slab width control and edge crack-free rolling method. The rolling method of the present application can ensure that the width error of the finally prepared 410S stainless steel slab and the target width is kept within the range of ±5 mm, and the prepared slab will not have problems such as edge cracks.

[0006] In order to achieve the above object, the present application adopts the following technical scheme: a rolling method for 410S stainless steel continuous casting slab width control and edge crack-free, comprising the following steps: S1, smelting; S2, continuous casting; S3, hot rolling; The weight percentage of each element in the smelting raw material is: C: 0.01-0.05%, Si: 0.2-0.6%, Mn: 0.1-0.5%, Ni: ≤0.30%, Cr: 11.5-13.5%, Mo: ≤0.3%, Cu: ≤0.3%, Al: ≤0.1%, N: 0.01-0.05%, V: ≤0.2%, P: <0.04%, S: <0.0020%, and the balance contains Fe and unavoidable impurities; The austenite phase ratio empirical value PA at 1100℃ is 55-67; The austenite phase ratio empirical value PA=420xC-11.5xSi+7xMn+23xNi-11.5xCr-12xMo+9xCu-52xAl-23xV+470xN+189.

[0007] The present application can effectively improve the accuracy of PA value by precisely controlling the content ratio of each element of austenite phase, so that the empirical value PA is maintained in the range of 55-67, which provides the necessary basis for realizing slab width control and edge crack-free rolling. Because if the PA value fluctuates too much, it will affect the two-phase ratio change of the microstructure transformation during continuous casting. If the PA value is too small, the higher the ferrite ratio, the more the solidification structure shows the characteristics of ferrite, the lower the high temperature strength, the greater the influence of the molten steel static pressure, the greater the change of the slab width, which is difficult to control. Although the PA value is larger, the solidification structure has less ferrite and the high temperature strength is improved, and the slab width is easier to control, but the present inventors have confirmed through a large number of practices that the ferrite content in the hot rolling process should be controlled to be at least 33% (the upper limit of the PA value is 67), and the finish rolling temperature is above 960℃, which can ensure that the hot rolling does not crack. When the PA value is greater than 67, the two-phase ratio is unbalanced during hot working, cracks appear at the phase boundary, and finally the edge of the product cracks.

[0008] If the austenite phase ratio empirical value PA of the raw material component system in the present application can be maintained in the range of 55-67 at 1100℃, it indicates that the PA value of the raw material component system at other temperatures can also be maintained in the corresponding range.

[0009] As one embodiment of the present invention, the smelting in step S1 includes the following steps: according to the composition of the smelting raw materials, blast furnace iron and ferrochrome raw materials are mixed into an AOD furnace for rough decarburization and chromium preservation smelting, then fed into a VOD furnace for deep decarburization and degassing, and finally refined and finely adjusted to the required composition in an LF furnace to obtain molten steel, while heating and holding the molten steel at the same time.

[0010] In one embodiment of the present invention, the continuous casting in step S2 is: the molten steel obtained in step S1 is used to prepare slabs through a continuous casting machine.

[0011] The production process of the continuous casting machine described in this invention includes: continuously pouring high-temperature molten steel into one or a group of water-cooled copper crystallizers, the molten steel gradually solidifies into a billet shell along the periphery of the crystallizer, and after the molten steel level rises to a certain height and the billet shell solidifies to a certain thickness, the straightening machine pulls out the billet, and the billet is cooled by water spraying in the secondary cooling zone to completely solidify the casting billet, and then cut into fixed lengths by the cutting device according to the requirements of steel rolling.

[0012] In one embodiment of the present invention, the crystallizer parameters in the continuous casting machine are set as follows: top opening width = target width - 20, taper 6.5 ± 1.0.

[0013] As one embodiment of the present invention, the width of the slab is controlled during the continuous casting process described in step S2; Predicted slab width = target width - 74 × v + (3.6 - W) × PA + 0.5 × (T - 1525) + 46.7 × Q^2 - 332.8 × Q + 338; Where, v: continuous casting speed, Q: total secondary cooling water volume in continuous casting, W: specific water volume in continuous casting process, W=Q / nominal steel throughput per minute G (G=v×1.6×0.22×7.9), 0.22 is billet thickness (unit: meter), T: tundish temperature in continuous casting process, PA: empirical value of austenite phase proportion at 1100℃.

[0014] This formula innovatively reflects the influence of parameters such as PA value and specific water content in the continuous casting process on slab width. When the specific water content (W) in the continuous casting process is large, it indicates a high cooling intensity, a thick solidified slab shell, and strong resistance to the static pressure of molten steel, thus reducing the influence of PA value on slab width. Conversely, when the specific water content is small, i.e., the cooling intensity is low, the solidified slab shell is relatively thin, and the resistance to the static pressure of molten steel is relatively weak, increasing the influence of PA value on slab width. Furthermore, based on this formula, various process parameters can be adjusted in real time, achieving stable control of slab width.

[0015] In one embodiment of the present invention, the continuous casting speed is 1.0-1.4 m / min.

[0016] In one embodiment of the present invention, the total volume of secondary cooling water in the continuous casting process is 2.2-4.2 m³. 3 / min.

[0017] In one embodiment of the present invention, the specific water content of the continuous casting process is 0.80-1.10 L / kg.

[0018] In one embodiment of the present invention, the tundish temperature during the continuous casting process is 1525-1555℃. By controlling the tundish temperature to 1525-1555℃ during continuous casting, the present invention effectively ensures that the final steel coil has good quality. When the tundish temperature is below 1525℃, the molten steel may not be able to be cast and will solidify prematurely; when the tundish temperature is above 1555℃, it will cause a series of production problems, such as the appearance of abnormally developed columnar crystals in the billet structure, resulting in poor quality, and increasing the risk of cracks and leaks.

[0019] In one embodiment of the present invention, the hot rolling in step S3 includes processes such as billet heating, rough rolling, and finish rolling. These processes are all conventional methods in the art.

[0020] In one embodiment of the present invention, the billet heating in step S3 adopts a four-stage heating method: the first stage preheating temperature is 550~750℃ and the time is 50-80min; the second stage heating temperature is 1020~1100℃ and the heating time is 40~60min; the third stage heating temperature is 1150~1230℃ and the heating time is 35~55min; the fourth stage homogenization temperature is 1140~1220℃ and the homogenization time is 40~60min.

[0021] As one embodiment of the present invention, the formula for calculating the total time of the four-stage heating is t = (0.8~1.3)h, where h is the thickness of the steel billet in mm and t is in min.

[0022] In one embodiment of the present invention, the final rolling temperature of the finishing rolling in step S3 is 960°C or higher. The final rolling temperature mentioned in this invention refers to the temperature of the hot-rolled strip when it leaves the last finishing mill, which directly affects the metallographic structure, grain size and mechanical properties of the material.

[0023] In one embodiment of the present invention, the width of the 410S stainless steel continuous casting slab obtained is within ±5mm of the target slab width.

[0024] Compared with the prior art, the present invention has the following beneficial effects: In this invention, by controlling the empirical value PA of the austenite phase ratio in the molten steel to be 55-67 during the rolling process, and by adjusting the parameters during the continuous casting process, the error between the width of the final 410S stainless steel slab and the target width is kept within ±5mm, and the steel coils produced will not have problems such as edge cracking. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the steel coil obtained by rolling in a specific embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the steel coil obtained by rolling in Comparative Example 2 in a specific embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the steel coil obtained by rolling in Comparative Example 3 in a specific embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0030] Examples 1-8 and Comparative Examples 1-6 The weight percentages of each element and PA values ​​of the smelting raw materials in Examples 1-8 and Comparative Examples 1-6 are shown in Table 1, and the condition parameters during the rolling process are shown in Table 2.

[0031] The methods for controlling the width of 410S stainless steel continuously cast slabs and rolling them without edge cracks in Examples 1-8 include the following steps: S1. Smelting: According to the composition of 410S stainless steel, blast furnace iron and ferrochrome raw materials are mixed into AOD furnace for rough decarburization and chromium preservation smelting, then put into VOD furnace for deep decarburization and degassing, and finally refined and finely adjusted to the required composition in LF furnace to obtain molten steel. At the same time, the molten steel is heated and held at the temperature. The weight percentages of each element in the 410S stainless steel are as follows: C: 0.01~0.05%, Si: 0.2~0.6%, Mn: 0.1~0.5%, Ni: ≤0.30%, Cr: 11.5~13.5%, Mo: ≤0.3%, Cu: ≤0.3%, Al: ≤0.1%, N: 0.01~0.05%, V: ≤0.2%, P: <0.04%, S: <0.0020% and the balance includes Fe and unavoidable impurities; The empirical value of the austenite phase proportion at 1100℃ is PA = 420×C - 11.5×Si + 7×Mn + 23×Ni - 11.5×Cr - 12×Mo + 9×Cu - 52×Al - 23×V + 470×N + 189. S2, Continuous casting: The molten steel obtained in step S1 is used to prepare slabs through a continuous casting machine. The production process of the continuous casting machine includes: continuously pouring high-temperature molten steel into one or a group of water-cooled copper crystallizers. The molten steel gradually solidifies into a slab shell along the periphery of the crystallizer. After the molten steel level rises to a certain height and the slab shell solidifies to a certain thickness, the straightening machine pulls out the slab and cools it with water in the secondary cooling zone to completely solidify the slab. The cutting device then cuts it into fixed lengths according to the requirements of steel rolling. The crystallizer parameters in the continuous casting machine are set as follows: top opening width = target width - 20, taper 6.5 ± 1.0; In step S2, the width of the slab is controlled during the continuous casting process. Predicted slab width = target width - 74 × v + (3.6 - W) × PA + 0.5 × (T - 1525) + 46.7 × Q^2 - 332.8 × Q + 338; Where, v: continuous casting speed, Q: total secondary cooling water volume in continuous casting, W: specific water volume in continuous casting process, W=Q / nominal steel throughput per minute G (G=v×1.6×0.22×7.9), 0.22 is billet thickness (unit: meter), T: tundish temperature in continuous casting process, PA: empirical value of the proportion of each element in the austenite phase at 1100℃; The continuous casting speed is 1.0-1.4 m / min; The total secondary cooling water volume for continuous casting is 2.2-4.2 m³. 3 / min; The specific water content of the continuous casting process is 0.80-1.10 L / kg; The tundish temperature during the continuous casting process is 1525-1555℃; S3. Hot rolling: This includes processes such as billet heating, rough rolling, and finish rolling. The billet heating process employs a four-stage heating method. The first stage, preheating, has a temperature of 550-750℃ and a duration of 50-80 minutes. The second stage, heating, has a temperature of 1020-1100℃ and a duration of 40-60 minutes. The third stage, heating, has a temperature of 1150-1230℃ and a duration of 35-55 minutes. The fourth stage, homogenization, has a temperature of 1140-1220℃ and a duration of 40-60 minutes. The total heating time for the four stages is calculated using the formula t = (0.8-1.3)h, where h is the billet thickness in mm and t is in minutes. The final rolling temperature of the finishing mill is above 960℃.

[0032] The rolling method for the comparative examples is the same as in the embodiment. The specific component weight percentages and parameters during the rolling process are shown in Tables 1-2. The weight percentages of each element and PA values ​​in comparative examples 3-6 are the same as in example 8.

[0033] Table 1. Weight percentage and PA value of each element in the examples and comparative examples.

[0034] Table 2. Continuous casting and rolling process parameters and steel edge quality for each group.

[0035] As can be seen from the experimental data in Tables 1 and 2, the embodiments of the present invention, by controlling the PA value within the range of 55-67 during the rolling process, and simultaneously controlling the parameters of the continuous casting process within the range of the present invention and satisfying the predicted width formula, can effectively control the error between the slab width and the target width to be within ±5mm. Furthermore, by controlling the final rolling temperature within the specified range during the rolling process, the final steel coil does not exhibit edge cracking issues.

[0036] In Comparative Example 1, the PA value of the billet composition is less than 55, indicating a high proportion of ferrite at high temperatures. The billet exhibits more ferrite properties, resulting in low high-temperature strength. It is more significantly affected by the hydrostatic pressure of the molten steel after exiting the crystallizer, leading to a severe over-width of the actual slab and consequently, non-compliant width of the hot-rolled coil. In Comparative Example 2, the PA value of the billet composition is 69.4, meaning that the austenite phase proportion exceeds 67% at high temperatures, while the corresponding ferrite proportion is less than 33%. Ferrite, as a soft phase, bears more deformation force, and its low content leads to uncoordinated deformation between the two phases, resulting in cracks at the phase boundaries and moderate layer cracking at the product edges (see [reference]). Figure 2 Furthermore, the final rolled steel coil was too narrow, failing to meet the actual width requirements. In Comparative Example 3, the final rolling temperature was 920℃, which was unsuitable, resulting in severe edge cracking of the final rolled steel coil (see...). Figure 3In Comparative Example 4, the continuous casting speed was too high at 1.45 m / min, and the secondary cooling water ratio was 0.77 L / kg, resulting in a severely oversized steel coil. In Comparative Example 5, the total secondary cooling water volume during continuous casting increased, resulting in a secondary cooling water ratio of 1.16 L / kg, leading to a significantly narrower steel coil that failed to meet requirements. In Comparative Example 6, the tundish temperature during continuous casting was too high, reaching 1570℃, resulting in an oversized final steel coil.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A rolling method for controlling the width of 410S stainless steel continuously cast slabs and preventing edge cracks, characterized in that, Includes the following steps: S1, Smelting; S2, continuous casting; S3, hot-rolled; The weight percentage of each element in the smelting raw material is as follows: C: 0.01~0.05%, Si: 0.2~0.6%, Mn: 0.1~0.5%, Ni: ≤0.30%, Cr: 11.5~13.5%, Mo: ≤0.3%, Cu: ≤0.3%, Al: ≤0.1%, N: 0.01~0.05%, V: ≤0.2%, P: <0.04%, S: <0.0020%, and the balance includes Fe and unavoidable impurities; The empirical value for the proportion of austenite phase at 1100℃ is PA, which is 55-67. The empirical value of the austenite phase ratio PA=420×C-11.5×Si+7×Mn+23×Ni-11.5×Cr-12×Mo+9×Cu-52×Al-23×V+470×N+189.

2. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 1, characterized in that, The smelting process described in step S1 includes the following steps: according to the composition of the smelting raw materials, blast furnace molten iron and ferrochrome molten raw materials are mixed into an AOD furnace for rough decarburization and chromium preservation smelting, then fed into a VOD furnace for deep decarburization and degassing, and finally refined and finely adjusted to the required composition in an LF furnace to obtain molten steel, while the molten steel is heated and kept at a constant temperature.

3. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 1, characterized in that... The continuous casting in step S2 is: the molten steel obtained in step S1 is used to prepare slabs through a continuous casting machine.

4. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 3, characterized in that, In step S2, the width of the slab is controlled during the continuous casting process. Predicted slab width = target width - 74 × v + (3.6 - W) × PA + 0.5 × (T - 1525) + 46.7 × Q^2 - 332.8 × Q + 338; Where, v: continuous casting speed, Q: total secondary cooling water volume in continuous casting, W: specific water volume in continuous casting process, W=Q / nominal per minute steel throughput G, T: tundish temperature in continuous casting process, PA: empirical value of austenite phase proportion at 1100℃.

5. The rolling method for controlling the width of 410S stainless steel continuously cast slabs and preventing edge cracks as described in claim 4, characterized in that, The continuous casting speed is 1.0-1.4 m / min; The total secondary cooling water volume for continuous casting is 2.2-4.2 m³. 3 / min; The specific water content of the continuous casting process is 0.80-1.10 L / kg; The tundish temperature during the continuous casting process is 1525-1555℃.

6. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 1, characterized in that, The hot rolling process described in step S3 includes billet heating, rough rolling, and finish rolling.

7. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 6, characterized in that, The billet heating adopts a four-stage heating method. The first stage preheating temperature is 550~750℃ and the time is 50~80min; the second stage heating temperature is 1020~1100℃ and the heating time is 40~60min; the third stage heating temperature is 1150~1230℃ and the heating time is 35~55min; the fourth stage homogenization temperature is 1140~1220℃ and the homogenization time is 40~60min.

8. The rolling method for controlling the width of 410S stainless steel continuously cast slabs and preventing edge cracks as described in claim 7, characterized in that, The formula for calculating the total heating time in the four stages is t = (0.8~1.3)h, where h is the thickness of the steel billet.

9. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 6, characterized in that, The finishing rolling temperature is above 960℃.

10. The rolling method for controlling the width and preventing edge cracks of 410S stainless steel continuously cast slabs as described in claim 1, characterized in that, The width of the 410S stainless steel continuous casting slab obtained is within ±5mm of the target slab width.

Images