300-series stainless steel thin strip and continuous casting preparation method thereof

Abstract

The invention belongs to the technical field of steel continuous casting, and particularly relates to a 300-series stainless steel thin strip and a continuous casting preparation method thereof. The stainless steel thin strip comprises the following components in percentage by mass: 0.01-0.05% of C; 0.30% to 0.60% of Si; 16.0% to 18.5% of Cr; 0.8 to 1.6 percent of Mn; 6.0 to 12.0 percent of Ni; 0.01 to 0.05 percent of N; 0.2%-3.5% of Cu; the steel comprises the following components in percentage by weight: less than or equal to 0.005% of S, less than or equal to 0.020% of P, less than or equal to 50ppm of B, less than or equal to 100ppm of Ce and the balance of The preparation method comprises the following steps: smelting, casting, hot rolling, water cooling, coiling to obtain a hot-rolled thin strip, and carrying out heat preservation and water quenching on the hot-rolled thin strip to obtain a finished product 300 series stainless steel thin strip. By adopting the optimized crystallization roller, the high-quality thin strip with the tensile strength of 900-1110 MPa, the yield strength of 670-780 MPa, the percentage elongation after fracture of 45%-65%, no cracks and wrinkles on the surface and the thickness of about 0.6 mm is obtained. The composition is reasonable in design, the preparation process is simple and controllable, and the obtained product is excellent in performance and convenient for industrial application.

Description

Technical Field

[0001] The present technology belongs to the field of steel continuous casting technology, and in particular relates to a 300 series stainless steel thin strip and a continuous casting preparation method thereof. Background Art

[0002] 300 series stainless steel is a very common type of stainless steel. The high nickel and chromium content makes 300 series stainless steel have a fully austenitic structure and excellent corrosion resistance. However, the high price is also one of the disadvantages of 300 series stainless steel. The high cost limits the application of 300 series stainless steel to a certain extent. The production of 300 series stainless steel by thin strip continuous casting can greatly shorten the production process of stainless steel and reduce costs. At the same time, the rapid solidification also makes the stainless steel thin strip products have finer grains and improves the processing performance of the product. Companies in Japan, South Korea and other countries have conducted research on thin strip continuous casting of 304 stainless steel and have achieved certain results. However, there are few successful long-term industrial production cases [Ge S, IsacM, Guthrie RI L. Progress of strip casting technology for steel; historical developments[J]. ISIJ international, 2012, 52(12): 2109-2122.]. The industrial production technology of thin strip continuous casting of 300 series stainless steel still needs to be further improved.

[0003] As a near-net-shape continuous casting technology, the thin strip continuous casting process produces thinner strips. Thinner strips mean less rolling cost. Lowering the roll gap width can produce thinner strips, further exerting its advantages. At the same time, thinner strips require better surface quality, higher drawing speed and higher cooling intensity. The surface temperature of the copper roll will rise rapidly after contacting the molten steel [Liu L, Liao B, Guo J, et al. 3D numerical simulation on thermal flow coupling field of stainless steel during twin-roll casting [J]. Journal of materials engineering and performance, 2014, 23: 39-48.]. If the heat is not dissipated in time, the surface quality of the thin strip will be affected. Summary of the invention

[0004] The present invention aims at the deficiencies of the existing 300 series stainless steel thin strip and its continuous casting preparation, and obtains a product with extremely high strength and excellent elongation by optimizing the composition, casting process and hot rolling process.

[0005] The present invention discloses a 300 series stainless steel thin strip; the composition of the stainless steel thin strip is as follows by mass percentage: C 0.01-0.05%; Si 0.30-0.60%; Cr 16.0-18.5%; Mn 0.8-1.6%; Ni 6.0-12.0%; N 0.01-0.05%; Cu 0.2-3.5%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The balance is iron and other inevitable impurities.

[0006] Preferably, the present invention provides a 300 series stainless steel strip; the composition of the stainless steel strip is as follows by mass percentage: C 0.015-0.025%; Si 0.36-0.48%; Cr 17.5-18.5%; Mn 1.0-1.2%; Ni 7.8-8.5%; N0.04-0.05%; Cu 0.2-0.4%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The remainder is iron and other inevitable impurities.

[0007] As a further preferred embodiment, the present invention provides a 300 series stainless steel strip; the composition of the stainless steel strip is as follows by mass percentage: C 0.02-0.023%; Si 0.39-0.45%; Cr 17.7-18.2%; Mn 1.05-1.1%; Ni 8.0-8.03%; N 0.045-0.05%; Cu 0.24-0.35%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The remainder is iron and other inevitable impurities.

[0008] As a further preferred embodiment, the present invention provides a 300 series stainless steel strip; the composition of the stainless steel strip is as follows by mass percentage: C 0.02%; Si 0.43%; Cr 18.0%; Mn 1.1%; Ni 8.0%; N 0.05%; Cu 0.35%; S≤0.005%, P ≤0.020%, B≤50ppm, Ce≤100ppm. The balance is iron and other unavoidable impurities, etc.; or The composition of the stainless steel strip is as follows by mass percentage: C 0.021%; Si 0.42%; Cr 18.2%; Mn 1.05%; Ni 8.02%; N 0.046%; Cu 0.36%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The remainder is iron and other unavoidable impurities, etc.; or The composition of the stainless steel strip is as follows by mass percentage: C 0.02%; Si 0.41%; Cr 18.2%; Mn 1.06%; Ni 8.03%; N 0.048%; Cu 0.31%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The remainder is iron and other inevitable impurities.

[0009] The microstructure of the 300 series stainless steel thin strip of the present invention is an austenite structure.

[0010] The 300 series stainless steel thin strip obtained by the process of the present invention has a room temperature ultimate tensile strength of 900-1110 MPa, an optimized tensile strength of 1085-1110 MPa, a yield strength of 670-780 MPa, preferably 700-780 MPa, an elongation after fracture of 45%-65%, preferably 55%-65%, and has good surface quality.

[0011] In the composition design of the 300 series stainless steel strip described in the present invention: C: The carbon element will combine with the Cr element in stainless steel to reduce corrosion resistance, but C also helps to increase the strength of the steel, so the carbon content is controlled at a low level.

[0012] Si: Silicon and Cr work together to improve the corrosion resistance of stainless steel, but silicon will increase the grain coarsening tendency of steel and increase brittleness, so it is controlled at a low level.

[0013] Cr: Chromium can passivate stainless steel and greatly improve its corrosion resistance. It is an important alloying element in 300 series stainless steel.

[0014] Mn: Manganese is an austenite stabilizing element and plays a synergistic role with nickel.

[0015] Ni: Nickel is an austenite stabilizing element that can improve the corrosion resistance of stainless steel and is an important alloying element in 300 series stainless steel.

[0016] N: Nitrogen is a strong austenite stabilizing element, similar to nickel, but a higher nitrogen content can easily affect product quality, so it is important to control the nitrogen level. Cu: Copper can improve the corrosion resistance of stainless steel and increase the ductility of stainless steel.

[0017] B: Trace boron can promote interfacial heat transfer and is beneficial to the solidification of thin strips Ce: Trace cerium can help refine the solidification structure, form heterogeneous nucleation sites, refine the grains, and further improve the performance of the thin strip.

[0018] The present invention provides a continuous casting preparation method for 300 series stainless steel thin strip, and the specific process flow is as follows: (1) Melting: According to the chemical composition of C 0.01~0.05%; Si 0.30~0.60%; Cr 16.0~18.5%; Mn 0.8~1.6%; Ni6.0~12.0%; N 0.01~0.05%; Cu 0.2~3.5%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The balance is iron and other inevitable impurities, etc., and vacuum melting is carried out to obtain molten steel for casting; (2) Casting: Use twin-roller thin strip continuous casting to cast the molten steel, the casting temperature is 1490~1540℃, and nitrogen protection is used during casting; the molten steel is poured between the copper twin rollers and solidified to obtain a stainless steel cast strip with a thickness of 1.0~1.9mm and good surface quality. Among them, the crystallization roller speed is selected to be 70~100m / min. The twin roller cooling rate is 1000-2000℃ / s; (3) Hot rolling: After the cast strip is delivered, it is hot rolled for 1-2 passes, water quenched after rolling, and then coiled. The rolling temperature is controlled at 850-1050°C, preferably 900-1000°C, and the reduction rate is ≤50%, so as to obtain a thin strip with a thickness of 0.5-1.3 mm. (5) Insulation: The obtained cold-rolled thin strip is kept at 500-900°C, preferably 650-800°C, for 30-120 min, preferably 60-60 min to eliminate stress, and water quenched to obtain a finished 300 series stainless steel thin strip.

[0019] In order to further improve the quality of the product, the present invention adopts a cavity-type water channel for the first time, replacing the traditional cooling water channel, greatly increasing the cooling water flux, thereby greatly improving the cooling strength of the crystallization roller, which is beneficial to improving the quality of the thin strip, and ribs are provided to meet the requirements of the casting and rolling force of the double rollers on the roller strength. The larger cavity makes it difficult for the cooling water to flow quickly, so the present invention sets a propeller in the cavity to stir and push the water flow. The propeller is mechanically driven by an internal gear. As the rotation speed of the crystallization roller increases, the rotation speed of the propeller is also faster, and there is no need to consider the problems encountered by the motor-driven propeller at high temperatures.

[0020] The invention discloses a continuous casting preparation method for 300 series stainless steel thin strips. The raw materials include electrolytic chromium, ferromanganese, ferroboron, pure cerium, high-purity nickel, industrial pure iron, ferrochromium nitride and electrolytic copper.

[0021] Preferably, the continuous casting machine in step 2 is a twin vertical roller thin strip continuous casting machine.

[0022] Preferably, the copper roller is made of red copper or other copper alloys.

[0023] Preferably, the surface of the copper roller is electroplated with Cr, and the thickness of the Cr plating layer is 0.06-0.12 mm.

[0024] In particular, the crystallization roller used in the casting process is a crystallization roller with enhanced cooling strength.

[0025] Furthermore, the crystallization roller with enhanced cooling strength uses cavities through which water can flow instead of traditional cooling water channels. The number of cavities is 4 to 12, which are evenly distributed. The thickness of the cavity accounts for 40% to 60% of the thickness of the crystallization roller sleeve. The roller surface is supported by ribs, and the thickness of the ribs is 10% to 20% of the cavity width.

[0026] Furthermore, a propeller is arranged in each cavity of the crystallization roller for enhancing the cooling strength to stir and push the water flow, and the diameter of the propeller is 50% to 90% of the minimum thickness in the three-dimensional space of the cavity.

[0027] Furthermore, the propeller in the crystallization roller for enhancing the cooling strength is driven by an internal gear. The propeller is connected to the internal gear through a shaft, and the shaft is fixed to the roller side. The shaft rotates around the roller axis as the roller rotates. The gear ring is fixed, thereby driving the internal gear to rotate.

[0028] As a further preferred embodiment, the crystallization roller 24 is composed of a rotating shaft 1, a main water channel 2, a rotating shaft water channel rib 3, a rotating shaft partition 4, a rotating shaft water ditch 5, a roller sleeve inner ring 6, a cooling water chamber 7, a roller sleeve roller surface 8, a propeller 9, a propeller rotating shaft connection 10, a plug 11, a propeller bearing 12, an internal gear 13, a gear rack 14, a gear rack keyway 15, a rotating shaft keyway 16, a gear ring 17, a roller sleeve rib 18, a distribution water channel 19, and a gear ring fixing hole 20; wherein the main water channel 2 is arranged in the rotating shaft 1 in a concentric circle with the rotating shaft 1, and the main water channel 2 runs through the rotating shaft 1 and has a symmetrical structure; The rotating shaft water channel rib plate 3 is connected to the rotating shaft partition 4; generally speaking, the rotating shaft 1, the rotating shaft water channel rib plate 3, and the rotating shaft partition 4 are a whole; when used in industry, they can be formed into a whole by welding, casting, etc.; The shaft water channel 5 is located between the water distribution channel (19) and the cooling water chamber (7); The roller sleeve inner ring 6 is arranged on the side of the cylindrical shaft partition 4.

[0029] A single cooling water chamber 7 is formed by the space enclosed by the roller sleeve inner ring 6, the inner wall of the corresponding roller sleeve roller surface 8, and two roller sleeve ribs 18. In industrial applications, in order to ensure the uniformity of cooling water and prevent the situation where the cooling uniformity and cooling effect deteriorate due to the slowing down or stopping of one or several propellers 9, N small holes can be evenly opened on the roller sleeve ribs 18; the N is greater than or equal to 6.

[0030] A propeller 9 is arranged at the center of each chamber.

[0031] The propeller 9 is connected to one end of the propeller shaft 10. The other end of the propeller shaft 10 passes through the propeller bearing 12 and is connected to the internal gear 13; among the number of propeller bearings 12, half are arranged on the side C, and the side C and the roller surface 8 of the roller sleeve constitute the convex part on the shaft 1; the propeller bearings 12 arranged on the side C are embedded in the plug 11. The other part of the propeller bearings 12 are fixed on the gear frame support 14; The bottom of the gear rack support 14 is disposed in the gear rack keyway 15 ; the gear rack keyway 15 is connected to the shaft keyway 16 by keying.

[0032] The ring gear 17 meshes with the internal gear 13; 17 is fixed from the outside. 17 does not move with the shaft or does not move at the same frequency as the shaft, thereby driving 13.

[0033] In the 2K-H (NGW) type planetary transmission system composed of the ring gear 17, the internal gear 13, and the gear carrier 14, the ring gear 17 is the fixed internal gear b, the internal gear 13 is the planetary gear g, and the gear carrier 14 is the planetary carrier H. Assuming that there is a sun gear a, when the speed of the internal gear is 0, that is, n b =0, there is

[0034] Where: ——The transmission ratio of the internal gear ring b is fixed, the sun gear a is active, and the planet carrier H is driven; —— The transmission ratio is that the planet carrier H is fixed, the sun gear a is active, and the internal gear ring b is driven; ——Number of teeth on the inner ring gear b ——Number of teeth on sun gear a In this system, the speed of the planetary gear g relative to the planetary carrier H is

[0035] Where: ——Speed ​​of the planetary gear g relative to the planetary carrier H ——Speed ​​of planetary gear g; ——Speed ​​of planet carrier H ——The transmission ratio of the planet carrier H being fixed, the planet gear g being active, and the sun gear a being driven; ——Speed ​​of sun gear a again:

[0036]

[0037] Combining equations (1) to (4), we have:

[0038] Among them, the number of teeth of the inner ring gear b Greater than the number of teeth on the planetary gear g , that is, the speed of the planetary gear g is greater than the speed of the planetary carrier H. Therefore, in this design, as the crystallization roller rotates, the internal gear 13 will rotate at high speed, driving the propeller to push the water flow.

[0039] 1) The 300 series stainless steel strip prepared by the thin strip continuous casting process of the present invention takes advantage of the characteristics of the thin strip continuous casting process, and obtains 300 series stainless steel strip with excellent performance with a shorter process and lower cost. Rapid solidification and the addition of B and Ce in the composition design work together to refine the solidification structure. The copper element can improve the corrosion resistance and antibacterial properties of the product. Rapid solidification overcomes the disadvantage of the copper element being very easy to segregate, and obtains good comprehensive performance.

[0040] 2) The process flow of the present invention is short and the thickness of the cast strip is thin. In order to ensure the cooling strength, a crystallization roller with enhanced cooling strength is designed. The crystallization roller uses multiple cooling water chambers instead of cooling water channels, which greatly increases the cooling water flow rate. Ribs are set to improve the structural strength of the crystallization roller to meet the high casting and rolling force requirements of thin strip continuous casting. A propeller is set in each chamber to improve the cooling water flow problem in the larger cooling water chamber. The propeller is connected to the gear through a shaft, and the propeller is driven to rotate through the internal gear mechanical transmission. The propeller speed can be increased as the crystallization roller speed increases, and there will be no problem of electrical equipment failure due to high temperature.

[0041] 3) The present invention only has the steps of hot rolling and heat preservation. Hot rolling welds the defects of the cast strip, and quenching prevents grain coarsening. The low temperature heat preservation eliminates stress, shortens the process flow on the basis of reducing the thickness of the thin strip, and further reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of a crystallization roller for enhancing cooling strength according to the present invention; Figure 2 It is a schematic diagram of the structure of the crystallization roller shaft; Figure 3 for Figure 1 Middle AA section view; Figure 4 for Figure 1 Middle BB section view; Figure 5 for Figure 3 Middle CC section view; Figure 6 It is a schematic diagram of the structure of the gear rack and the internal gear set; Figure 7 It is a schematic diagram of the process flow of the vertical twin-roller thin strip continuous casting unit of the present invention.

[0043] In the figure: 1: rotating shaft; 2: main water channel; 3: rotating shaft water channel rib; 4: rotating shaft partition; 5: rotating shaft water groove, 6: roller sleeve inner ring; 7: cooling water chamber; 8: roller sleeve roller surface; 9: propeller; 10: propeller rotating shaft; 11: plug; 12: propeller bearing; 13: internal gear; 14: gear rack; 15: gear rack keyway; 16: rotating shaft keyway; 17: gear ring; 18: roller sleeve rib; 19: distribution water channel; 20: gear ring fixing hole; 21: induction furnace; 22: tundish; 23: distributor; 24: crystallization roller; 25: cooling device; 26: swing guide plate; 27: pinch roller; 28: nitrogen protection area; 29: online heating area; 30: rolling roller; 31: cooling device; 32: conveyor roller; 33: flying shear. DETAILED DESCRIPTION

[0044] The technical route of the present invention is described in detail in conjunction with the drawings in the embodiments of the present invention. The following embodiments are only some embodiments of the inventor's team. Other embodiments obtained based on the embodiments of the present invention by those skilled in the art without making any creative work all belong to the protection scope of the present invention.

[0045] For the present invention Next, with the help of Figure 4 The process flow diagram of the vertical twin-roller thin strip continuous casting unit shown in the figure introduces the process flow of the present invention The induction melting furnace 18 is used for melting in a protective atmosphere, and electrolytic chromium, ferromanganese, ferroboron, pure cerium, high-purity nickel, industrial pure iron, ferrochrome nitride, electrolytic copper are selected according to the chemical composition of C 0.01-0.05%; Si 0.30-0.60%; Cr 16.0-18.5%; Mn 0.8-1.6%; Ni 6.0-12.0%; N 0.01-0.04%; Cu 0.2-3.5%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm. The balance is iron and other inevitable impurities, etc., and vacuum melting is performed to obtain molten steel for casting.

[0046] After smelting, the molten steel is cast at a casting temperature of 1490-1540°C, poured into the tundish shown in 19, and then flows into the distributor shown in 20, and then flows into the roll gap, the molten steel solidifies, and a stainless steel cast strip with a thickness of 1.0-1.9 mm is obtained, and the surface quality is good. Among them, the crystallization roll speed is selected to be 70-100 m / min.

[0047] Figure 4In the figure, the crystallization roller shown in 4 is the crystallization roller with enhanced cooling strength as described above. The crystallization roller uses a cooling water chamber to replace the traditional cooling water channel, and a propeller is provided to assist in pushing the water flow, which greatly increases the cooling water flow rate and is conducive to improving the cooling strength. Its structure is as follows Figure 1 As shown: exist Figure 1 In the figure, 1 is the shaft, 2 is the main water channel, 3 is the shaft water channel rib plate, which is connected to the shaft partition shown in 4. 1, 3, and 4 are integrally formed during casting and processed. 5 is the shaft water ditch, 6 is the inner ring of the roller sleeve, and Figure 2 The 18 roller sleeve ribs and the roller sleeve surface 8 shown in the figure constitute the crystallization roller sleeve as a whole. The crystallization roller sleeve is integrally cast and processed, and is connected to the shaft body by freezing. 7 is a cooling water chamber. 9 is a propeller, which is connected to the propeller shaft 10 through a key, and 10 is connected to the internal gear 13 through a key. 10 is supported by the propeller bearing 12, and 12 is supported by the plug 11 and the gear rack 14 respectively. 15 is the gear rack keyway, 16 is the shaft keyway, 14 is connected to the shaft through a key and moves with the shaft. 17 gear ring is meshed with 13, 17 is fixed by the outside, and does not move with the shaft, thereby driving 13.

[0048] exist Figure 2 In the crystallization roller shaft structure diagram shown in FIG. 1 , the entire crystallization roller shaft is cast and processed. The shaft water channel ribs shown in FIG. 3 connect the shaft and the shaft partition to form a whole. The cooling water is distributed to the cooling water chamber through the main water channel through the hollow ribs. The side walls of the shaft partition and the shaft water channel are connected to the roller sleeve.

[0049] The flow of cooling water is Figure 3 The AA section view shown is further explained: exist Figure 3 In the figure, 18 roller sleeve ribs divide 6 cavities, which are evenly distributed. The thickness of the cavities accounts for 40% to 60% of the thickness of the crystallization roller sleeve. The propeller is arranged in the center of each chamber. As shown in the 10 propeller shaft in the figure, a propeller is used to rotate and stir the water in the middle of each chamber. The diameter of the propeller is 50% to 90% of the thickness of the cavity. The 18 roller sleeve ribs improve the structural strength of the crystallization roller and adapt to the larger casting and rolling force. The thickness of the ribs is 10% to 20% of the cavity width. 2 is the main water channel in the center of the shaft, which is divided into multiple distribution water channels shown in 19 by the main water channel ribs shown in 3. The cooling water flows into the cooling water chamber shown in 7 through the shaft groove shown in 5 to connect the water flow.

[0050] With the help of Figure 4 The BB cross-sectional view further illustrates the structure of the roller sleeve and the rotating shaft. like Figure 4As shown, 8 roller sleeve roller surfaces, 18 roller sleeve ribs, and 6 roller sleeve inner rings form a whole, which are obtained by casting and processing. The roller sleeve is installed on the rotating shaft by freezing, as shown in the connection between 4 and 6 in the figure.

[0051] With the help of Figure 5 The CC cross-sectional view shown further illustrates the cooling water chamber structure: exist Figure 5 In the figure, the 18 roller sleeve ribs divide the 6 roller sleeve inner ring into a cooling water chamber as shown in the figure, and the water flows through the 7 cooling water chamber to achieve water cooling of the roller surface. The left side of the figure is the hole opened for installing the propeller.

[0052] With the help of Figure 6 Explain the structure of the gear and its movement: Figure 6 The gear assembly diagram of the side of the crystallization roller is shown in Figure 14. The gear rack is keyed to the crystallization roller shaft, so that it rotates synchronously with the rotation of the crystallization roller, and then the propeller shaft rotates with the crystallization roller shaft. The gear rack ring gear 17 is welded to the fixing hole of the gear ring 20, and is fixed to the outside through the fixing hole of the gear ring 20. It does not rotate with the crystallization roller and is meshed with the internal gear. The internal gear rotates under the joint action of the fixed gear ring and the rotating gear rack, forming a structure similar to a planetary gear. The internal gear drives the propeller to rotate and assists in pushing the water flow.

[0053] exist Figure 7 In the figure, 24 is a crystallization roller, 17 is a fixed gear ring, and 20 is a gear ring fixing hole, which is externally fixed. After the molten steel quickly solidifies to form a cast strip, the cast strip is guided to the clamping roller 27 by a swinging guide plate 26. During this period, a cooling device 25 is used to spray water to accelerate cooling to avoid strip breakage. A nitrogen atmosphere is used for protection in the dotted box shown in 28 to avoid oxidation. It is then sent to the nitrogen protection area shown in the dotted box 29 for online heating until the temperature rises to 850~1050℃, and 1~2 passes of hot rolling are carried out at the roller shown in 30, with a reduction rate of ≤50%, to obtain a hot-rolled thin strip with a thickness of 0.5~1.3mm, which is then sent out by the conveying roller 32, and cooled by spraying water using the cooling device 31, and finally sheared and coiled.

[0054] After the hot rolled strip is coiled, the steel coil is kept at 500-900°C for 30-120 min in a nitrogen atmosphere to eliminate stress and water quench to obtain a finished 300 series stainless steel thin strip.

[0055] In addition, mold casting was used to simulate the conventional casting method to obtain comparative examples 1 to 4, and the process was as follows: (1) Melting: Electrolytic chromium, ferromanganese, high-purity nickel, industrial pure iron, ferrochromium nitride, electrolytic copper and other raw materials are selected according to the above composition and vacuum melted to obtain molten steel for casting.

[0056] (2) Mold casting: Pour molten steel into a mold under nitrogen atmosphere to solidify, keep it at 1200℃ for 360min, and then cut it into ingots. (3) Rolling: The ingot is cut into steel plates of suitable thickness and then rolled. The ingot is kept at 850-1050°C and then hot rolled to obtain a rolled plate. The rolled plate is then water-cooled, coiled, and heat-treated to obtain a 300 series stainless steel plate produced by simulating the traditional process, as shown in Comparative Examples 1-4.

[0057] The following are Examples 1 to 6 of the present invention and Comparative Examples 1-4. It can be seen that the thin strip continuous casting preparation method of 300 series stainless steel described in the present invention can obtain a stainless steel strip with excellent mechanical properties. The mechanical properties of the 300 series stainless steel strip with traditional composition prepared according to the process of the present invention are significantly better than those of the 300 series stainless steel strip prepared by the traditional process. The 300 series stainless steel strip with traditional composition obtained by the process of the present invention can obtain an ultimate tensile strength of 1086MPa and a maximum elongation of 58%. After adding B and Ce, the maximum elongation increases to 62%, and the ultimate tensile strength can also reach 1105MPa; in the embodiment where the crystallization roller with enhanced cooling strength is not used, the surface quality of the cast strip is slightly poor, and the mechanical properties are also worse than those of other embodiments.

[0058]

[0059]

Claims

1. A 300 series stainless steel thin strip, characterized in that: The composition of the stainless steel strip is as follows by mass percentage: C 0.01~0.05%; Si 0.30~0.60%; Cr 16.0~18.5%; Mn 0.8~1.6%; Ni 6.0~12.0%; N 0.01~0.05%; Cu 0.2~3.5%; S ≤0.005%, P ≤0.020%, B≤50ppm, Ce≤100ppm, and the balance is iron and other inevitable impurities.

2. A 300 series stainless steel thin strip according to claim 1, characterized in that: The composition of the stainless steel strip is as follows by mass percentage: C 0.015~0.025%; Si 0.36~0.48%; Cr 17.5~18.5%; Mn 1.0~1.2%; Ni7.8~8.5%; N 0.04~0.05%; Cu 0.2~0.4%; S ≤0.005%, P ≤0.020%, B≤50ppm, Ce≤100ppm, and the balance is iron and other inevitable impurities.

3. A 300 series stainless steel thin strip according to claim 2, characterized in that: The composition of the stainless steel strip is as follows by mass percentage: C 0.02~0.023%; Si 0.39~0.45%; Cr 17.7~18.2%; Mn 1.05~1.1%; Ni8.0~8.03%; N 0.045~0.05%; Cu 0.24~0.35%; S ≤0.005%, P ≤0.020%, B≤50ppm, Ce≤100ppm, and the balance is iron and other inevitable impurities.

4. A 300 series stainless steel thin strip according to claim 3, characterized in that: The composition of the stainless steel strip is as follows by mass percentage: C 0.02%; Si 0.43%; Cr 18.0%; Mn 1.1%; Ni 8.0%; N 0.05%; Cu0.35%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm, and the balance is iron and other inevitable impurities; or The composition of the stainless steel strip is as follows by mass percentage: C 0.021%; Si 0.42%; Cr 18.2%; Mn 1.05%; Ni 8.02%; N 0.046%; Cu 0.36%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm, and the balance is iron and other inevitable impurities; or The composition of the stainless steel strip is as follows by mass percentage: C 0.02%; Si 0.41%; Cr 18.2%; Mn 1.06%; Ni 8.03%; N 0.048%; Cu 0.31%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm, and the remainder is iron and other inevitable impurities.

5. A continuous casting method for preparing 300 series stainless steel thin strip, characterized in that: The steps include: (1) Melting: vacuum melting is performed on raw materials with the chemical composition of C 0.01~0.05%; Si 0.30~0.60%; Cr 16.0~18.5%; Mn 0.8~1.6%; Ni 6.0~12.0%; N 0.01~0.05%; Cu 0.2~3.5%; S ≤0.005%, P ≤0.020%, B ≤50ppm, Ce ≤100ppm, the balance being iron and other inevitable impurities to obtain molten steel for casting; (2) Casting: Use twin-roller thin strip continuous casting to cast the molten steel, the casting temperature is 1490~1540℃, and nitrogen protection is used during casting; the molten steel is poured between the copper twin rollers and solidified to obtain a stainless steel casting strip with a thickness of 1.0~1.9mm; the crystallization roller speed is 70~100m / min. The twin-roller cooling rate is 1000-2000℃ / s; (3) Hot rolling: After the cast strip is delivered, it is hot rolled for 1 to 2 passes, water quenched after rolling, and then coiled. The rolling temperature is controlled at 850 to 1050 ° C, and the reduction rate is ≤ 50%, to obtain a thin strip with a thickness of 0.5 to 1.3 mm; (5) Insulation: The obtained cold-rolled thin strip is kept at 500-900°C for 30-120 min to eliminate stress, and water quenched to obtain a finished 300 series stainless steel thin strip.

6. The continuous casting method for preparing 300 series stainless steel thin strip according to claim 5, characterized in that: The crystallization roller (24) is composed of a rotating shaft (1), a main water channel (2), a rotating shaft water channel rib (3), a rotating shaft partition (4), a rotating shaft water ditch (5), a roller sleeve inner ring (6), a cooling water chamber (7), a roller sleeve roller surface (8), a propeller (9), a propeller rotating shaft connection (10), a plug (11), a propeller bearing (12), an internal gear (13), a gear rack (14), a gear rack keyway (15), a rotating shaft keyway (16), a gear ring (17), a roller sleeve rib (18), a distribution water channel (19), and a gear ring fixing hole (20); wherein the main water channel (2) is arranged inside the rotating shaft (1) in a concentric circle with the rotating shaft (1), and the main water channel (2) passes through the rotating shaft (1) and is symmetrical in structure; The rotating shaft water channel rib plate (3) is connected to the rotating shaft partition (4); the rotating shaft (1), the rotating shaft water channel rib plate (3) and the rotating shaft partition (4) are an integral whole; The shaft water channel (5) is located between the water distribution channel (19) and the cooling water chamber (7); The roller sleeve inner ring (6) is arranged on the side of the cylindrical shaft partition (4); A single cooling water chamber (7) is formed by a space enclosed by a roller sleeve inner ring (6), an inner wall of a corresponding roller sleeve roller surface (8), and two roller sleeve ribs (18); A propeller (9) is arranged at the center of each chamber; The propeller (9) is connected to one end of the propeller shaft (10); the other end of the propeller shaft (10) passes through the propeller bearing (12) and is connected to the internal gear (13); half of the propeller bearings (12) are arranged on the side surface C, and the side surface C and the roller surface (8) of the roller sleeve constitute a raised portion on the shaft (1); the propeller bearings (12) arranged on the side surface C are embedded in the plug (11); and the other part of the propeller bearings (12) are fixed on the gear frame support (14); The bottom of the gear rack support (14) is arranged in the gear rack keyway (15); the gear rack keyway 15 is connected to the rotating shaft keyway 16 by keying; The ring gear (17) meshes with the internal gear (13); 17 is fixed from the outside.

7. The continuous casting method for preparing 300 series stainless steel thin strip according to claim 6, characterized in that: N small holes can be evenly formed on the roller sleeve rib 18; the N is greater than or equal to 6.

8. The continuous casting method for preparing 300 series stainless steel thin strip according to claim 5, characterized in that: The continuous casting machine in step 2 is a double vertical roller thin strip continuous casting machine; The copper roller is made of copper or other copper alloys; The surface of the copper roller is electroplated with Cr, and the thickness of the Cr coating is 0.06~0.12mm.

9. The continuous casting method for preparing 300 series stainless steel thin strip according to claim 6, characterized in that: The number of cooling water chambers (7) is 4 to 12, which are evenly distributed, and the cavity thickness accounts for 40% to 60% of the thickness of the crystallization roller sleeve. The roller surface is supported by ribs, and the thickness of the ribs is 10% to 20% of the cavity width; A propeller is arranged in each cavity to stir and push the water flow, and the diameter of the propeller is 50% to 90% of the minimum thickness in the three-dimensional space of the cavity.

10. A continuous casting method for preparing 300 series stainless steel thin strip according to any one of claims 5 to 9, characterized in that: The microstructure of the obtained 300 series stainless steel strip is austenite. The obtained 300 series stainless steel thin strip has an ultimate tensile strength of 900-1110 MPa at room temperature, an optimized tensile strength of 1085-1110 MPa, a yield strength of 670-780 MPa, preferably 700-780 MPa, an elongation after fracture of 45%-65%, preferably 55%-65%, and no cracks or wrinkles on the surface.

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