A process for forming mirror-finish stainless steel sheets by bending without indentation.

Abstract

The application discloses a mirror surface stainless steel plate non-indentation bending forming machining process and belongs to the technical field of mirror surface stainless steel bending forming. The mirror surface stainless steel plate non-indentation bending forming machining process adopts a forming die made by an original process, and the mirror surface stainless steel plate non-indentation bending forming machining process steps are as follows: placing a plate on the top of a lower die body 30, pressing and forming the plate by an upper die body, allowing the lower die body 30 to rotate at intervals relative to a limiting area 20 under pressure, bending the mirror surface stainless steel plate into a design angle, and resetting the lower die body 30 to an initial state by a tension spring 40 after the bending is completed. The mirror surface stainless steel forming can be completed for tens of thousands of times, and the plate forming precision can be ensured after tens of thousands of times.

Description

Technical Field

[0001] This invention relates to the technical field of bending and forming mirror stainless steel, and in particular to a process for bending and forming mirror stainless steel sheets without indentation and the processing technology of the mold used in the forming process. Background Technology

[0002] Traditional bending dies typically employ a lower die and an upper die, with the lower die using a specific shape to bend sheet metal. However, the existing bending structure can cause indentations on the sheet metal surface, making it unsuitable for certain sheet metals with specific surface requirements, such as mirror-finish stainless steel bending parts, which must be indentation-free. A combined, indentation-free rotating flip-plate die, publication number CN217889144U, is described. It includes a die body comprising a lower die body and two flip plates symmetrically arranged on the top of the lower die body. A connecting assembly is provided between the lower die body and the flip plates. This connecting assembly includes a tension spring fixedly installed inside the lower die body and a pull rod connected to the flip plates. The tension spring includes a spring portion located at the lower end of the lower die body and connecting portions at both ends of the spring portion. The two ends of the tension spring are respectively connected and fixed to the pull rod. This invention employs a lower mold body with two symmetrical arc grooves, paired with left and right flaps, and then fixed by connecting components. During the process of the upper mold pressing the workpiece into the lower mold body, the workpiece contacts the flap plane, and the flaps rotate within the lower mold body, preventing relative sliding between the workpiece and the flaps, thus eliminating indentations and scratches on the workpiece surface caused by compression. However, the flaps in this technology are prone to significant wear after thousands of forming cycles. Once severe wear occurs, the flaps cannot achieve the designed angle during sheet forming, making it impossible to guarantee the accurate forming angle even after tens of thousands of forming cycles. Therefore, a bending die and sheet processing technology capable of completing tens of thousands of forming cycles while ensuring sheet forming accuracy are needed. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art, and therefore a process for bending and forming mirror-finish stainless steel sheets without indentation is proposed.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A process for forming mirror stainless steel sheet by bending without indentation includes a lower die base, a limiting area is provided on the top of the lower die base, two lower die bodies are symmetrically arranged in the limiting area and rotate relative to the limiting area, and tension springs are installed at the bottom of the two lower die bodies. The bottom of the tension springs is fixed to the lower die base by locking bolts.

[0006] The processing steps of the lower mold body are as follows: The lower mold body, made from raw materials, undergoes nitriding followed by oxidation treatment. A deposition solution is prepared by mixing tetraethoxysilane, 25%–28% ammonia, pure water, and anhydrous ethanol in a ratio of 1:(4–5):(7–8):(3–4). The heat-treated lower mold body is placed in 25–35 times the volume of the deposition solution and ultrasonically reacted at 45–60 Hz for 2–4 hours. Then, 0.02–0.08 times the volume of nano-yttrium oxide is added to the tetraethoxysilane solution, and ultrasonically reacted at 45–60 Hz for 2–4 hours. The mold body is then removed and treated with 250m... Wash twice with pure water, then twice with 180 mL of 95% ethanol, and dry at 85-95°C for 4-6 hours. Then place it in a reactor, evacuate to a pressure of 3.5-4.5 MPa, and introduce 0.05-0.12 times the amount of gaseous titanium tetrachloride in tetraethoxysilane. Raise the reactor temperature to 330-350°C, evacuate again to a pressure of 3.5-4.5 MPa, and then introduce mixed reducing gas until the pressure reaches 75-95 MPa. Finally, set the temperature of the lower mold to 800-1200°C and deposit for 5-8 hours.

[0007] Based on the above embodiments, the following improvements are made: the mixed reducing gas includes one or more of hydrogen and silane in addition to methane.

[0008] Based on the above embodiments, the following improvements are made: the components and their mass percentages of the lower mold base 10 are as follows: 0.17~0.52 parts of C, 0.17~0.31 parts of Si, 5.44~8.15 parts of Mn, 7.13~11.58 parts of Cr, 4.15~6.55 parts of Ni, ≤0.02 parts of P, ≤0.02 parts of S, 0.021~0.038 parts of Nb, 0.012~0.017 parts of Y, 0.07~0.23 parts of Ti, 0.08~0.14 parts of B, with the balance being Fe and impurities;

[0009] Where: Ti = 0.21(Nb + Y) + 0.34(C + S);

[0010] Where: Si = 0.21B + 0.015(Ni + Cr).

[0011] Based on the above embodiments, the following improvements are made: the components and their mass percentages of the lower mold base are as follows: 0.19~0.50 parts of C, 0.21~0.28 parts of Si, 5.87~7.65 parts of Mn, 8.15~9.54 parts of Cr, 4.65~6.15 parts of Ni, 0.891~2.030 parts of Mo, ≤0.02 parts of P, ≤0.02 parts of S, 0.025~0.037 parts of Nb, 0.014~0.016 parts of Y, 0.09~0.20 parts of Ti, with the balance being Fe and impurities.

[0012] Based on the above embodiments, the following improvements are made: the components of the lower mold base further include 0.013 to 0.023 parts of alloy steel modifier, which includes 32 to 45 parts of Al2O3, 26 to 31 parts of Al, 16 to 28 parts of CaF2, 5 to 15 parts of MgO, and 2 to 5 parts of LaNi5.

[0013] Based on the above embodiments, the following improvements are made, and the processing steps of the lower mold base are as follows:

[0014] (1) Smelting

[0015] Using the above-mentioned raw materials for smelting, 0.013 to 0.023 parts of alloy steel modifier are added during steel tapping. The alloy steel modifier includes 32 to 45 parts of Al2O3, 26 to 31 parts of Al, 16 to 28 parts of CaF2, 5 to 15 parts of MgO and 2 to 5 parts of LaNi5 to obtain the forging blank of the lower die holder 10 material.

[0016] (2) Stress-relieving annealing treatment of forgings and forgings

[0017] The forging blank is heated to 1250~1450℃ for forging, and the final forging temperature is 950~970℃ to obtain the forging. The obtained forging is annealed in an annealing furnace at a temperature of 680~750℃ for 4~5 hours. It is then cooled to 200~300℃ in the annealing furnace, held for 0.6~1.2 hours, and then air-cooled to room temperature.

[0018] (3) Preliminary machining and heat treatment of forgings

[0019] The forging is machined into the primary shape of the mold on a machine tool, with a 1.5 mm allowance on each side. The machined mold is first heated to 530~550℃ and held for 3~4 h, then heated to 750~800℃ and held for 1~2 h, then heated to 940~960℃ and held for 30~45 min, then quenched, oil quenched, cooled and then subjected to deep cryogenic treatment at -220℃ to -230℃ for 1~2 h, then restored to room temperature in air, and then tempered once at 130~140℃. After cooling to room temperature, it is placed for 1~1.5 h and then tempered a second time at 150~170℃.

[0020] (4) Deep machining and machining center processing of the lower mold base

[0021] Remove the oxide layer from the surface of the mold after processing, and assemble it onto a grinding machine for grinding. Leave a margin of 0.7~1mm on each side. After letting it sit for at least 1 day, grind the other sides, except for the curved surface, to the required size. Place the workpiece obtained from deep processing into a machining center and use a milling cutter to mill the curved surface of the mold, removing a margin of 0.7~1mm.

[0022] Based on the above embodiments, the following improvements are made: the lower mold body includes an integrally formed guide body and a limiting body, the guide body and the limiting area are rolled together, and the limiting body overlaps the top of the lower mold base in its natural state.

[0023] Based on the above embodiments, the following improvements are made: the side of the lower mold base is provided with a slot for installing the tension spring, and the bottom side is provided with an installation groove. An installation plate is fixedly installed inside the installation groove by bolts, and a pin for installing the bottom end of the tension spring is provided on the installation plate.

[0024] Compared with existing technologies, the present invention has the following beneficial effects: By adopting the above-mentioned scheme: through the rational quantification of Si, Si melts into the alloy matrix, exerting a solid solution strengthening effect; B is used to form hard metal compounds with Ni and / or Cr, resulting in a dispersed distribution in the alloy, thus playing a dispersion strengthening role and improving the hardness and wear resistance of the cemented carbide. Due to the addition of Cr, it can enhance the solid solution strengthening effect and passivation ability of Ni, and can also form hard intermetallic compound phases with B and Si, playing a dispersion strengthening role and improving wear resistance. The addition of B and Si results in a wider overall solid-liquid phase temperature range for the upper mold steel, exhibiting excellent fluidity and wettability, leading to better processing performance of the upper mold steel; salts with low density, low viscosity, and good fluidity will form on the surface of the molten steel and float to the surface, protecting the alloy from oxidation and preventing the formation of porosity.

[0025] A reasonable amount of Ti (0.21(Nb+Y)+0.34(C+S)) during TiC formation allows Nb and Y to refine the primary TiC dendrites, increase the dendrite spacing, and increase the amount of elongated eutectic titanium carbide, resulting in ultrafine-grained TiC. The ultrafine-grained TiC, purified at the Nb and Y interface, increases interfacial wettability, allowing it to disperse uniformly in the alloy matrix with high density. When microcracks and residual stresses are generated around the ultrafine-grained TiC, it can pin the cracks, dissipating fracture energy and thus improving the toughness of the alloy material and the machinability of forgings. Ti precipitates in steel, such as TiN, TiC, and Ti(C, N), can prevent austenite grain growth during heating and forging, while inhibiting the recovery and recrystallization of deformed austenite grains. Furthermore, the deformation bands and unrecovered substructure boundaries in austenite can further promote ferrite grain refinement, thus refining the microstructure and grain size, thereby improving the strength and impact toughness of the steel. Ti has a stronger affinity for S than Mn. As Ti content increases, the amount of Ti4C2S2 compounds in the steel gradually increases and replaces MnS inclusions. In other words, the addition of Ti removes S from MnS, forming a more stable Ti4C2S2 compound, which reduces MnS precipitation. The formation of elongated MnS inclusions in the steel is reduced due to the formation of Ti4C2S2. Spherical Ti4C2S2 compounds have high hardness and do not deform during high-temperature forging, thus improving the impact toughness of the steel.

[0026] Ti, Y, and Al will also form a binary or ternary eutectic liquid phase at a relatively low temperature during the cooling process of molten steel. The appearance of the liquid phase is conducive to the flow of grains in the initial formation of molten steel, thereby promoting the densification of grain distribution.

[0027] By adding the above components during tapping, the top ladle slag can be deoxidized and modified, improving the desulfurization rate of the molten steel. Diffusion deoxidation is achieved by adding calcium carbide and aluminum particles, promoting rapid melting and uniform deoxidation of the top slag. Three-phase alloys with good thermal stability, such as Mg2NiLa, Mg2Ni, and MgNi2, are readily obtained. Given the extremely reactive chemical properties of Ti, which readily reacts with O and N in the molten steel, Ti microalloying is chosen before tapping to stabilize the Ti yield.

[0028] After nitriding and oxidation treatment of 42CrMo (the raw material for the lower mold body), the nitrided layer surface contains iron(III) oxide and possesses a certain degree of magnetism. A silicon solution is prepared using tetraethoxysilane, 25%–28% ammonia, pure water, and anhydrous ethanol in a specific ratio. Under ultrasonic reaction, the silicon solution is deposited in two stages. First, silicon dioxide is coated onto the outer surface of the iron(III) oxide through stable Si-O-Fe chemical bonds, forming an initial deposition layer. Then, yttrium oxide is introduced into the silicon solution, and due to the presence of stable Si-OY chemical bonds, a final deposition layer is formed, resulting in a porous silicon dioxide layer with yttrium doping on the nitrided layer surface. Finally, the porous silicon dioxide layer with yttrium doping is deposited in gaseous tetrachloroethylene. In a titanium dioxide atmosphere, titanium tetrachloride enters the porous silica and undergoes cross-linking, hydrolysis, and condensation reactions with its amino groups to form a titanium dioxide cross-linked network. Finally, it is reduced at high temperature in a methane-containing reducing atmosphere to form titanium carbide. Due to the doping of yttrium in the silica layer, during the formation of titanium carbide, yttrium can make the primary titanium carbide dendrites smaller, increase the dendrite spacing, and increase the number of slender eutectic titanium carbide to obtain ultrafine-grained titanium carbide. The ultrafine-grained titanium carbide has increased interfacial wettability at the yttrium-purified interface, allowing it to be uniformly dispersed in the silica layer and have a high density. When microcracks and residual stress are generated around the ultrafine-grained titanium carbide, it can pin the cracks and consume fracture energy, thereby improving the toughness of the coating material.

[0029] In a further technical solution described above, the mixed reducing gas includes one or more of hydrogen and silane in addition to methane. The addition of silane enables silicon carbide to be distributed within the titanium carbide crystals and achieves high density, while also resulting in binary and / or ternary eutectic phases. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of the lower mold base of the present invention;

[0031] Figure 2 This is a schematic diagram of the internal structure of the lower mold base of the present invention. Figure 1 ;

[0032] Figure 3 This is a schematic diagram of the internal structure of the lower mold base of the present invention. Figure 2 . Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] Example 1: A processing technology for bending mirror stainless steel sheet without indentation, including a lower mold base 10, a limiting area 20 on the top of the lower mold base 10, two lower mold bodies 30 symmetrically arranged at the limiting area 20 and rotatably arranged relative to the limiting area 20, a tension spring 40 installed at the bottom of the two lower mold bodies 30, the bottom of the tension spring 40 being fixed to the lower mold base 10 by locking bolts, the lower mold body 30 including an integrally formed guide body 31 and a limiting body 32, the guide body 31 being rotatably arranged with the limiting area 20, the limiting body 32 being naturally overlapped with the top of the lower mold base 10, the side of the lower mold base 10 having a slot for installing the tension spring 40, and the bottom side having an installation groove 11, an installation plate 12 being fixedly installed inside the installation groove 11 by bolts, and a pin 13 for installing the bottom end of the tension spring 40 being arranged on the installation plate 12.

[0036] When in use, the sheet metal is placed on top of the lower mold body 30, and the upper mold body presses the sheet metal down to form it. The lower mold body 30 will be indirectly pressed and rotate relative to the limiting area 20, bending the mirror stainless steel sheet metal. After bending is completed, the tension spring 40 will reset the lower mold body 30 to its initial state.

[0037] The processing steps of the lower mold body 30 are as follows: The steel of the lower mold body 30 (using 42CrMo as raw material) is subjected to nitriding followed by oxidation treatment. A deposition solution is prepared by mixing tetraethoxysilane, 28% ammonia, pure water, and anhydrous ethanol in a ratio of 1:4:7:3. The heat-treated lower mold body 30 is placed in 25-35 times its volume of the deposition solution and ultrasonically reacted at 45-60 Hz for 2-4 hours. Then, 0.03 times its volume of nano-yttrium oxide is added to the tetraethoxysilane solution, and ultrasonically reacted at 45-60 Hz for 2-4 hours. The mold body is then removed and rinsed with 250 mL of pure water. The material was washed twice with 180 mL of 95% ethanol and dried at 85-95°C for 4-6 hours. Then, it was placed in a reactor and evacuated to a pressure of 3.5-4.5 MPa. 0.05-0.12 times the amount of gaseous titanium tetrachloride tetraethoxysilane was introduced, and the reactor temperature was raised to 345°C. The evacuation was repeated to a pressure of 3.5-4.5 MPa, and then a mixed reducing gas was introduced until the pressure reached 75-95 MPa. Finally, the temperature of the lower mold 30 was set at 1150°C, and deposition was carried out for 5-8 hours to obtain the Ti-xY wear-resistant alloy layer.

[0038] Example 2: Based on the above example, the following improvements were made: The lower mold body 30 steel (using 42CrMo as raw material) was subjected to nitriding and then oxidation treatment. A deposition solution was prepared by mixing tetraethoxysilane, 25%~28% ammonia water, pure water, and anhydrous ethanol in a ratio of 1:5:8:4. The heat-treated lower mold body 30 was placed in 25~35 times the volume of the deposition solution and ultrasonically reacted at 45~60Hz for 2~4 hours. Then, 0.05 times the volume of nano-yttrium oxide was added to the tetraethoxysilane and ultrasonically reacted at 45~60Hz for 2~4 hours. The mold body was then removed and subjected to 250m... The material was washed twice with pure water and twice with 180 mL of 95% ethanol. It was then dried at 85-95°C for 4-6 hours. Subsequently, it was placed in a reactor, and a vacuum was drawn to a pressure of 3.5-4.5 MPa. 0.05-0.12 times the amount of gaseous titanium tetrachloride tetraethoxysilane was introduced, and the reactor temperature was raised to 340°C. The vacuum was drawn again to a pressure of 3.5-4.5 MPa, and then a mixed reducing gas was introduced until the pressure reached 75-95 MPa. Finally, the temperature of the lower mold 30 was set at about 1000°C, and deposition was carried out for 7 hours to obtain the Ti-xY wear-resistant alloy layer.

[0039] Example 3: Based on the above examples, the following improvements were made: The lower mold body 30 steel (using 42CrMo as raw material) was subjected to nitriding followed by oxidation treatment. A deposition solution was prepared by mixing tetraethoxysilane, 25%~28% ammonia, pure water, and anhydrous ethanol in a ratio of 1:4:8:3. The heat-treated lower mold body 30 was placed in 25~35 times its volume of the deposition solution and ultrasonically reacted at 45~60Hz for 2~4 hours. Then, 0.04 times its volume of nano-yttrium oxide was added to the tetraethoxysilane solution, and ultrasonically reacted at 45~60Hz for 2~4 hours. The mixture was then removed and subjected to 250m... The material was washed twice with pure water and twice with 180 mL of 95% ethanol. It was then dried at 85-95°C for 4-6 hours. Subsequently, it was placed in a reactor, and a vacuum was drawn to a pressure of 3.5-4.5 MPa. 0.05-0.12 times the amount of gaseous titanium tetrachloride tetraethoxysilane was introduced, and the reactor temperature was raised to 350°C. The vacuum was drawn again to a pressure of 3.5-4.5 MPa, and then a mixed reducing gas was introduced until the pressure reached 75-95 MPa. Finally, the temperature of the lower mold 30 was set at about 950°C, and deposition was carried out for 7 hours to obtain the Ti-xY wear-resistant alloy layer.

[0040] Comparative Example 1: Only nitriding followed by oxidation treatment.

[0041] Comparative Example 2: The lower mold body 30, made of 42CrMo steel, was subjected to nitriding followed by oxidation treatment. A deposition solution was prepared by mixing tetraethoxysilane, 25%–28% ammonia, pure water, and anhydrous ethanol in a ratio of 1:4–5:7–8:3–4. The heat-treated lower mold body 30 was placed in 25–35 times its volume of the deposition solution and ultrasonically reacted at 45–60 Hz for 2–4 hours. After removal, it was rinsed twice with 250 mL of pure water and twice with 180 mL of 95% ethanol. Dry at 95°C for 4-6 hours, then place in a reactor, evacuate to a pressure of 3.5-4.5 MPa, introduce 0.05-0.12 times the amount of gaseous titanium tetrachloride in tetraethoxysilane, raise the reactor temperature to 330-350°C, evacuate again to a pressure of 3.5-4.5 MPa, then introduce mixed reducing gas until the pressure reaches 75-95 MPa, then maintain the temperature of the lower mold base 10, lower mold body 20 and upper mold body 60 at 800-1200°C for 7 hours of deposition.

[0042] Comparative Example 3: The lower mold base 10, lower mold body 20, and upper mold body 60, made from 42CrMo, were subjected to nitriding followed by oxidation treatment. A deposition solution was prepared by mixing tetraethoxysilane, 25%–28% ammonia, pure water, and anhydrous ethanol in a ratio of 1:4–5:7–8:3–4. The heat-treated lower mold base 10, lower mold body 20, and upper mold body 60 were placed in 25–35 times the volume of the deposition solution and ultrasonically reacted at 45–60 Hz for 2–4 hours. The mixture is subjected to ultrasonic treatment at 5-60 Hz for 2-4 hours. After removal, it is washed twice with 250 mL of pure water and twice with 180 mL of 95% ethanol. It is then dried at 85-95°C for 4-6 hours. Subsequently, it is placed in a reactor and a vacuum is drawn to achieve a pressure of 3.5-4.5 MPa. Then, a mixed reducing gas is introduced until the pressure reaches 75-95 MPa. Titanium wire is introduced and the temperature is increased to about 2000°C. Finally, the lower mold is deposited at a temperature of 800-1200°C for 6 hours.

[0043] The following are the performance analysis results of the density and wear resistance of the Ti-xY wear-resistant alloy layers of Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention:

[0044]

[0045] The molds produced using the same process in the three embodiments described above have hardnesses of HRC59, HRC61, and HRC58, respectively, and no cracks were found after magnetic particle testing. The molds remained usable after 24,300, 24,500, and 23,900 cycles of processing, respectively.

[0046] Example 4: The components and their mass percentages of the lower mold base 10 are as follows: 0.17 parts C, 0.186 parts Si, 5.44 parts Mn, 7.13 parts Cr, 4.15 parts Ni, ≤0.02 parts P, ≤0.02 parts S, 0.021 parts Nb, 0.012 parts Y, 0.072 parts Ti, 0.08 parts B, with the balance being Fe and impurities;

[0047] Where: Ti = 0.21 * (Nb + Y) + 0.34 * (C + S) = 0.21 * (0.021 + 0.012) + 0.34 * (0.17 + 0.02) = 0.072;

[0048] Where: Si=0.21*B+0.015*(Ni+Cr)=0.21*0.08+0.015*(4.15+7.13)=0.186.

[0049] Example 5: The components and mass percentages of the lower mold base 10 are as follows: 0.19 parts C, 0.22 parts Si, 5.87 parts Mn, 8.15 parts Cr, 5.15 parts Ni, ≤0.02 parts P, ≤0.02 parts S, 0.028 parts Nb, 0.016 parts Y, 0.081 parts Ti, 0.08 parts B, with the balance being Fe and impurities;

[0050] Where: Ti = 0.21 * (Nb + Y) + 0.34 * (C + S) = 0.21 * (0.028 + 0.016) + 0.34 * (0.19 + 0.02) = 0.081;

[0051] Where: Si=0.21*B+0.015*(Ni+Cr)=0.21*0.08+0.015*(5.15+8.15)=0.22.

[0052] Example 6: The components and their mass percentages of the lower mold base 10 are as follows: 0.32 parts C, 0.265 parts Si, 7.65 parts Mn, 9.54 parts Cr, 6.15 parts Ni, ≤0.02 parts P, ≤0.02 parts S, 0.037 parts Nb, 0.016 parts Y, 0.127 parts Ti, 0.14 parts B, with the balance being Fe and impurities;

[0053] Where: Ti = 0.21 * (Nb + Y) + 0.34 * (C + S) = 0.21 * (0.037 + 0.016) + 0.34 * (0.32 + 0.02) = 0.127;

[0054] Where: Si = 0.21 * B + 0.015 * (Ni + Cr) = 0.21 * 0.14 + 0.015 * (6.15 + 9.54) = 0.265.

[0055] The molds produced using the same process in the three embodiments described above have hardnesses of HRC58, HRC60, and HRC57, respectively, and no cracks were found after magnetic particle testing. The molds remained usable after 23,320, 23,540, and 23,170 cycles of processing.

[0056] In the above embodiments, the following improvements were made: the alloy steel modifier includes 45 parts of Al2O3, 26 parts of Al, 16 parts of CaF2, 10 parts of MgO, and 3 parts of LaNi5.

[0057] In the above embodiments, the following improvements were made: the alloy steel modifier includes 32 parts of Al2O3, 31 parts of Al, 19 parts of CaF2, 13 parts of MgO, and 5 parts of LaNi5.

[0058] By adding the above components during tapping, the top ladle slag can be deoxidized and modified, improving the desulfurization rate of the molten steel. Diffusion deoxidation is achieved by adding calcium carbide and aluminum particles, promoting rapid melting and uniform deoxidation of the top slag. Three-phase alloys with good thermal stability, such as Mg2NiLa, Mg2Ni, and MgNi2, are readily obtained. Given the extremely reactive chemical properties of Ti, which readily reacts with O and N in the molten steel, Ti microalloying is chosen before tapping to stabilize the Ti yield.

[0059] Example 7: The machining steps of the lower mold base 10 are as follows:

[0060] (1) Smelting

[0061] Using the above-mentioned materials for smelting, 0.013 to 0.023 parts of alloy steel modifier are added during steel tapping. The alloy steel modifier includes 32 to 45 parts of Al2O3, 26 to 31 parts of Al, 16 to 28 parts of CaF2, 5 to 15 parts of MgO and 2 to 5 parts of LaNi5 to obtain the forging blank of the lower die holder 10 material.

[0062] (2) Stress-relieving annealing treatment of forgings and forgings

[0063] The forging blank is heated to 1250~1450℃ for forging, and the final forging temperature is 950~970℃ to obtain the forging. The obtained forging is annealed in an annealing furnace at a temperature of 680~750℃ for 4~5 hours. It is then cooled to 200~300℃ in the annealing furnace, held for 0.6~1.2 hours, and then air-cooled to room temperature.

[0064] (3) Preliminary machining and heat treatment of forgings

[0065] The forging is machined into the primary shape of the mold on a machine tool, with a 1.5 mm allowance on each side. The machined mold is first heated to 530~550℃ and held for 3~4 h, then heated to 750~800℃ and held for 1~2 h, then heated to 940~960℃ and held for 30~45 min, then quenched, oil quenched, cooled and then subjected to deep cryogenic treatment at -220℃ to -230℃ for 1~2 h, then restored to room temperature in air, and then tempered once at 130~140℃. After cooling to room temperature, it is placed for 1~1.5 h and then tempered a second time at 150~170℃.

[0066] (4) Deep machining and machining center processing of the lower mold base 10

[0067] Remove the oxide layer from the surface of the mold after processing, and assemble it onto a grinding machine for grinding. Leave a margin of 0.7~1mm on each side. After letting it sit for at least 1 day, grind the other sides, except for the curved surface, to the required size. Place the workpiece obtained from deep processing into a machining center and use a milling cutter to mill the curved surface of the mold, removing a margin of 0.7~1mm.

[0068] A process for forming mirror stainless steel sheet without indentation by bending is provided. The forming mold made using the above-described process is as follows: The sheet is placed on the top of the lower mold body 30, and the upper mold body presses the sheet down to form it. The lower mold body 30 will be indirectly pressed and rotate relative to the limiting area 20, bending the mirror stainless steel sheet to the designed angle. After bending is completed, the tension spring 40 will return the lower mold body 30 to its initial state.

[0069] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The substitutions may be replacements of some structures, devices, or method steps, or they may be complete technical solutions. Equivalent substitutions or modifications made to the technical solutions and inventive concepts of the present invention should all be covered within the scope of protection of the present invention.

Claims

1. A processing technology for a mirror stainless steel plate non-marking bending forming mold, including a forming mold, the forming mold including a lower mold base (10), a limiting area (20) is provided on the top of the lower mold base (10), two lower mold bodies (30) are symmetrically arranged at the limiting area (20) and rotate relative to the limiting area (20), and tension springs (40) are installed at the bottom of the two lower mold bodies (30), and the bottom of the tension springs (40) is fixed to the lower mold base (10) by locking bolts; Its features are, The components and their mass percentages of the lower mold base (10) are as follows: 0.17~0.52 parts of C, 0.17~0.31 parts of Si, 5.44~8.15 parts of Mn, 7.13~11.58 parts of Cr, 4.15~6.55 parts of Ni, ≤0.02 parts of P, ≤0.02 parts of S, 0.021~0.038 parts of Nb, 0.012~0.017 parts of Y, 0.07~0.23 parts of Ti, 0.08~0.14 parts of B, with the balance being Fe and impurities; Where: Ti = 0.21(Nb+Y) + 0.34(C+S); Where: Si = 0.21B + 0.015(Ni + Cr); The processing steps of the lower mold body (30) are as follows: the steel of the lower mold body (30) is subjected to nitriding and oxidation treatment. A deposition solution is prepared by mixing tetraethoxysilane, ammonia water with a mass fraction of 25% to 28%, pure water, and anhydrous ethanol in a ratio of 1:(4 to 5):(7 to 8):(3 to 4). The heat-treated lower mold body (30) is placed in 25 to 35 times the amount of deposition solution and ultrasonically reacted at 45 to 60 Hz for 2 to 4 hours. Then, 0.02 to 0.08 times the amount of nano-yttrium oxide is added to the tetraethoxysilane and ultrasonically reacted at 45 to 60 Hz for 2 to 4 hours. The mold body is then removed and treated with 2... Wash twice with 50 mL of pure water, then twice with 180 mL of 95% ethanol, and dry at 85-95°C for 4-6 hours. Then place it in a reactor, evacuate to a pressure of 3.5-4.5 MPa, and introduce 0.05-0.12 times the amount of gaseous titanium tetrachloride in tetraethoxysilane. Raise the reactor temperature to 330-350°C, evacuate again to a pressure of 3.5-4.5 MPa, and then introduce mixed reducing gas until the pressure reaches 75-95 MPa. Then, set the temperature of the lower mold (30) to 800-1200°C and deposit for 5-8 hours.

2. The processing technology of a non-marking bending forming mold for mirror stainless steel sheet according to claim 1, characterized in that, The components of the lower mold base (10) also include 0.013 to 0.023 parts of alloy steel modifier, which includes 32 to 45 parts of Al2O3, 26 to 31 parts of Al, 16 to 28 parts of CaF2, 5 to 15 parts of MgO and 2 to 5 parts of LaNi5.

3. The processing technology of a non-marking bending forming mold for mirror stainless steel sheet according to claim 2, characterized in that, The machining steps of the lower mold base (10) are as follows: (1) Smelting Using the material smelting method of claim 2, 0.013 to 0.023 parts of alloy steel modifier are added during steel tapping to obtain a forging blank of the lower die base (10) material; (2) Stress-relieving annealing treatment of forgings and forgings The forging blank is heated to 1250~1450℃ for forging, and the final forging temperature is 950~970℃ to obtain the forging. The obtained forging is annealed in an annealing furnace at a temperature of 680~750℃ for 4~5 hours. It is then cooled to 200~300℃ in the annealing furnace, held for 0.6~1.2 hours, and then air-cooled to room temperature. (3) Preliminary machining and heat treatment of forgings The forging is machined into the primary shape of the mold on a machine tool, with a 1.5 mm allowance on each side. The machined mold is first heated to 530~550℃ and held for 3~4 h, then heated to 750~800℃ and held for 1~2 h, then heated to 940~960℃ and held for 30~45 min, then quenched, cooled and then subjected to deep cryogenic treatment at -220℃ to -230℃ for 1~2 h, then restored to room temperature in air, and then tempered once at 130~140℃. After cooling to room temperature, it is placed for 1~1.5 h and then tempered a second time at 150~170℃. (4) Deep machining and machining center processing of the lower mold base (10) Remove the oxide layer from the surface of the mold after heat treatment, and assemble it onto a grinding machine for grinding. Leave a margin of 0.7~1mm on each side. After letting it sit for at least 1 day, grind the other sides, except for the curved surface, to the required size. Place the workpiece obtained from deep processing into a machining center and use a milling cutter to mill the curved surface of the mold, removing a margin of 0.7~1mm.

4. The processing technology of a non-marking bending forming mold for mirror stainless steel sheet according to claim 1, characterized in that, The lower mold body (30) includes an integrally formed guide body (31) and a limiting body (32). The guide body (31) and the limiting area (20) are rotatably arranged, and the limiting body (32) is naturally attached to the top of the lower mold base (10).

5. The processing technology of a non-marking bending forming mold for mirror stainless steel sheet according to claim 1, characterized in that, The lower mold base (10) has a slot for installing a tension spring (40) on its side and an installation groove (11) on its bottom side. An installation plate (12) is fixedly installed inside the installation groove (11) by bolts. A pin (13) for installing the bottom end of the tension spring (40) is provided on the installation plate (12).

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