A method for producing a cold-rolled strip blank for invar foil

Abstract

The application discloses a preparation method of cold-rolled strip blank for invar foil, and relates to the technical field of invar alloy strip preparation. The method comprises the following steps: heating and forging an invar alloy ingot to obtain a forged blank, and then heating and hot-rolling the forged blank after surface treatment to obtain a hot-rolled strip blank; sequentially performing dehydrogenation treatment, continuous annealing, flattening, grading pickling and mechanical finishing on the hot-rolled strip blank to obtain a clean hot-rolled strip blank; wherein the dehydrogenation treatment temperature is 700-750 DEG C, the holding time is 2.5-4 h, and the flattening deformation is 5%-12%; cold-rolling, trimming and continuously annealing the clean hot-rolled strip blank to obtain a primary cold-rolled strip; and performing surface finishing, multi-pass cold-rolling and continuous annealing on the primary cold-rolled strip to obtain the cold-rolled strip blank for invar foil. The scheme is beneficial to improving the uniformity of the structure in the thickness direction of the strip blank, guaranteeing the size stability of the subsequent ultra-thin invar foil, and meeting the use requirements of high-end precision devices.

Description

Technical Field

[0001] This application relates to the field of Invar alloy strip preparation technology, and in particular to a method for preparing cold-rolled strip blanks for Invar foil. Background Technology

[0002] Invar alloys possess ultra-low thermal expansion characteristics and excellent dimensional stability, making them a core substrate for the manufacture of high-end semiconductors, aerospace, and precision display devices. The quality of cold-rolled strip blanks for foil directly determines the processing yield and performance of the final ultra-thin foil. Currently, the industry commonly uses a process of ingot forging, hot rolling, and cold rolling finishing to prepare Invar strip blanks. Simultaneously, product quality is optimized through melt refining, post-rolling grinding, and temperature-controlled rolling, which can meet the mass production needs of Invar strips under normal operating conditions.

[0003] However, the existing preparation system lacks sufficient overall precision control and has inherent process defects. The industry generally lacks standardized and precise control methods for non-metallic inclusions throughout the ingot. The types and grades of inclusions at the beginning, end, and middle of the ingot are chaotic and fluctuate greatly, resulting in poor consistency in raw material purity. At the same time, conventional processes have limited ability to eliminate hydrogen-induced defects and microscopic residual stress inside hot-rolled strips. Oxide scale and processing residue defects on the surface of the strips are difficult to completely remove, leading to problems such as pitting, roll-through, dimensional deviations, and uneven performance during subsequent ultra-thin multi-pass cold rolling, which cannot meet the preparation standards for ultra-high precision ultra-thin Invar foil. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing cold-rolled strip blanks for inductor foil materials, aiming to solve the technical problems of poor strip blank purity and microstructure uniformity and frequent rolling defects in the prior art.

[0005] To achieve the above objectives, this application provides a method for preparing a cold-rolled strip blank for high-quality Invar foil, comprising: Invar alloy ingots are heated and forged to obtain forging blanks. The forging blanks are then surface-treated and hot-rolled to obtain hot-rolled strip blanks. The hot-rolled strip is subjected to dehydrogenation treatment, continuous annealing, leveling, graded pickling, and mechanical finishing in sequence to obtain a clean hot-rolled strip; wherein the dehydrogenation treatment temperature is 700-750℃, the holding time is 2.5-4h, and the leveling deformation is 5%-12%; The clean hot-rolled strip is cold-rolled, trimmed, and continuously annealed to obtain a primary cold-rolled strip. The cold-rolled strip is surface finished, subjected to multiple cold rolling passes and continuous annealing to obtain a cold-rolled strip blank for insulated foil.

[0006] In some optional embodiments, the Invar alloy ingot is heated and forged to obtain a forging blank, comprising: The Invar alloy ingot was heated to 700-820°C at a heating rate of 65-90°C / h and held for 3 hours. Then, the temperature is increased to 1080-1150℃ at a heating rate of 100-140℃ / h, and held for 3 hours before forging. The initial forging temperature is greater than or equal to 1040℃, and the final forging temperature is greater than or equal to 900℃. After forging is completed, a forging blank is obtained.

[0007] In some optional embodiments, the forging blank undergoes surface treatment, including: The forging blank is graded and polished using resin corundum grinding wheels. For rough grinding, 40-80 grit grinding wheels are used, and for fine grinding, 120 grit grinding wheels are used. During the polishing process, emulsion is used for continuous cooling to control the surface temperature of the forging blank to be less than or equal to 85°C. Apply an anti-oxidation coating to the surface of the forged billet after grinding; The forging billet after coating is subjected to stress-relief annealing at a temperature of 340–480°C. After holding at this temperature for 1 hour, it is cooled in the furnace to complete the surface treatment process of the forging billet.

[0008] In some alternative embodiments, the process of heating and hot rolling to obtain a hot-rolled strip includes: The forging billet is heated to 750-850℃ at a heating rate of 90-120℃ / h and held for 2 hours. Then, the temperature is increased to 1080-1150℃ at a heating rate of 110-150℃ / h, and held for 3 hours before rolling. The initial rolling temperature is greater than or equal to 1040℃, and the final rolling temperature is greater than or equal to 900℃. After rolling, hot-rolled strip blanks are obtained.

[0009] In some optional embodiments, the graded pickling of the hot-rolled strip includes: Hot-rolled strip billets are pre-pickled using a sulfuric acid solution containing steel corrosion inhibitors and a mass concentration of 15%–22%, with the pickling temperature controlled at 55–73°C. After pre-pickling, the hot-rolled strip is subjected to final pickling using a composite solution of 14%–22% hydrochloric acid and 0.7%–1.6% hydrofluoric acid. The pickling temperature is controlled at 43–51°C, and the acid solution is kept circulating throughout the pickling process to complete the graded pickling process.

[0010] In some optional embodiments, the hot-rolled strip after graded pickling undergoes mechanical finishing, including: The hot-rolled strip is polished using a 60-120 mesh flap wheel at a speed of 2800-3200 r / min and a grinding head pressure of 0.2-0.3 MPa. After grinding, the surface of the blank is polished using a 0.2mm steel wire brush; After polishing, compressed air is used to blow away any remaining debris on the surface of the strip blank to obtain a clean hot-rolled strip blank.

[0011] In some optional embodiments, the clean hot-rolled strip is subjected to cold rolling, edge trimming, and continuous annealing to obtain a primary cold-rolled strip, including: Clean hot-rolled strip is cold-rolled for 5 to 8 passes using work rolls with a profile arithmetic mean deviation of 0.2 μm, with the total deformation controlled at 50% to 60%, and rolling oil is continuously sprayed during the rolling process; The strip blank after the initial blanking is cut is then trimmed on both sides. After the edges are trimmed, continuous annealing is performed to obtain a cold-rolled strip.

[0012] In some optional embodiments, surface finishing of the primary cold-rolled strip includes: The cold-rolled strip is polished using an 800-1600 mesh abrasive belt. The belt running speed is 15-30 m / s, and the polishing pressure is controlled at 0.12-0.17 MPa. After grinding, the surface of the blank is rinsed with high-pressure water and squeezed dry to thoroughly remove surface debris and complete the surface finishing process.

[0013] In some optional embodiments, the surface-finished cold-rolled strip is subjected to multiple cold rolling passes and continuous annealing to obtain a cold-rolled strip blank for Invar foil, comprising: The cold rolling process is carried out in 6 to 10 passes using work rolls with a profile arithmetic mean deviation of 0.15 μm, with the last two passes using work rolls with a profile arithmetic mean deviation of 0.08 μm. The total deformation during cold rolling is controlled at 55% to 65%, and the rolling oil supply flow rate is maintained at 500 to 1000 L / h during the rolling process; After cold rolling, continuous annealing is performed to obtain cold-rolled strip blanks for insulated foil materials.

[0014] In some alternative embodiments, the Invar alloy ingot is prepared by a consumable remelting process.

[0015] The above-mentioned technical solution of this application has at least the following beneficial technical effects: The technical solution of this application, by implementing graded constraint of non-metallic inclusions at the head, middle, and tail of the Invar alloy ingot casting, precisely controls the inclusion level at different locations, which can avoid local plasticity differences caused by uneven axial inclusion distribution in the ingot and prevent local stress concentration in the subsequent rolling stage. At the same time, the dehydrogenation parameters of 700-750℃ and holding for 2.5-4h are matched with 5%-12% leveling deformation. On the one hand, it promotes the directional diffusion and precipitation of hydrogen atoms, reducing the risk of hydrogen-induced microcrack initiation. On the other hand, it breaks the continuous oxide structure on the surface by moderate plastic deformation, which facilitates subsequent pickling and mechanical finishing to remove the oxide layer. The cooperation of each process reduces hydrogen-induced defects inside the strip and surface oxide residues, suppresses pinholes and roll-through defects induced by inclusions and oxide scale during ultra-thin rolling, improves the uniformity of the strip structure in the thickness direction, ensures the dimensional stability of the subsequent ultra-thin Invar foil, and meets the requirements of high-end precision devices. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of an embodiment of the method for preparing high-quality invar foil cold-rolled strip blanks provided in this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this application. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0018] The embodiments described in this application are only some, not all, of the embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments described herein without inventive effort are within the scope of protection of this application.

[0019] Invar alloys possess ultra-low thermal expansion characteristics and excellent dimensional stability, making them a core substrate for the manufacture of high-end semiconductors, aerospace, and precision display devices. The quality of cold-rolled strip blanks for foil directly determines the processing yield and performance of the final ultra-thin foil. Currently, the industry commonly uses a process of ingot forging, hot rolling, and cold rolling finishing to prepare Invar strip blanks. Simultaneously, product quality is optimized through melt refining, post-rolling grinding, and temperature-controlled rolling, which can meet the mass production needs of Invar strips under normal operating conditions.

[0020] However, the existing preparation system lacks sufficient overall precision control and has inherent process defects. The industry generally lacks standardized and precise control methods for non-metallic inclusions throughout the ingot. The types and grades of inclusions at the beginning, end, and middle of the ingot are chaotic and fluctuate greatly, resulting in poor consistency in raw material purity. At the same time, conventional processes have limited ability to eliminate hydrogen-induced defects and microscopic residual stress inside hot-rolled strips. Oxide scale and processing residue defects on the surface of the strips are difficult to completely remove, leading to problems such as pitting, roll-through, dimensional deviations, and uneven performance during subsequent ultra-thin multi-pass cold rolling, which cannot meet the preparation standards for ultra-high precision ultra-thin Invar foil.

[0021] To address the aforementioned technical problems, this application provides a method for preparing a cold-rolled strip blank for high-quality Invar foil.

[0022] The technical solution of this application, by implementing graded constraint of non-metallic inclusions at the head, middle, and tail of the Invar alloy ingot casting, precisely controls the inclusion level at different locations, which can avoid local plasticity differences caused by uneven axial inclusion distribution in the ingot and prevent local stress concentration in the subsequent rolling stage. At the same time, the dehydrogenation parameters of 700-750℃ and holding for 2.5-4h are matched with 5%-12% leveling deformation. On the one hand, it promotes the directional diffusion and precipitation of hydrogen atoms, reducing the risk of hydrogen-induced microcrack initiation. On the other hand, it breaks the continuous oxide structure on the surface by moderate plastic deformation, which facilitates subsequent pickling and mechanical finishing to remove the oxide layer. The cooperation of each process reduces hydrogen-induced defects inside the strip and surface oxide residues, suppresses pinholes and roll-through defects induced by inclusions and oxide scale during ultra-thin rolling, improves the uniformity of the strip structure in the thickness direction, ensures the dimensional stability of the subsequent ultra-thin Invar foil, and meets the requirements of high-end precision devices.

[0023] In some alternative embodiments, such as Figure 1 As shown, the preparation method of this high-quality Invar foil cold-rolled strip includes the following steps: Step S1: Heat and forge the Invar alloy ingot to obtain a forging billet, perform surface treatment on the forging billet, and then heat and hot roll it to obtain a hot-rolled strip billet; In some optional embodiments, the Invar alloy ingot is heated and forged to obtain a forging blank, including the following specific steps: Step A1: Heat the Invar alloy ingot to 700-820℃ at a heating rate of 65-90℃ / h and hold for 3 hours; Optionally, the heating rate can be 65℃ / h, 71℃ / h, 78℃ / h, 84℃ / h or 90℃ / h, or any value between the above values; Optionally, the heating temperature can be 700℃, 730℃, 765℃, 795℃ or 820℃, or any value between the above values; Step A2: Heat the temperature to 1080-1150℃ at a heating rate of 100-140℃ / h, hold for 3 hours, and then carry out forging operations; wherein the initial forging temperature is greater than or equal to 1040℃ and the final forging temperature is greater than or equal to 900℃. Optionally, the heating rate can be 100℃ / h, 110℃ / h, 120℃ / h, 130℃ / h or 140℃ / h, or any value between the above values; Optionally, the heating temperature can be 1080℃, 1098℃, 1115℃, 1132℃ or 1150℃, or any value between the above values; Optionally, the initial forging temperature can be 1040℃, 1065℃, 1090℃, 1115℃ or 1140℃, or any value between the above values; Optionally, the final forging temperature can be 900℃, 925℃, 950℃, 975℃ or 1000℃, or any value between the above values.

[0024] Step A3: After forging is completed, a forging billet is obtained.

[0025] In some optional embodiments, the forging billet undergoes surface treatment, including the following specific steps: Step B1: The forging blank is graded and polished using resin corundum grinding wheels. For rough grinding, a 40-80 grit grinding wheel is used, and for fine grinding, a grinding wheel of 120 grit or higher is used. During the polishing process, emulsion is used for continuous cooling to control the surface temperature of the forging blank to be less than or equal to 85°C. Optionally, the grit size of the coarse grinding wheel can be 40, 60, or 80, or any value between the above values; Optionally, the mesh size of the fine grinding wheel can be 120 mesh, 150 mesh, 180 mesh, 200 mesh, 220 mesh or 240 mesh, or any value between the above values; Step B2: Apply an anti-oxidation coating to the surface of the forged billet after grinding; Step B3: Perform stress-relief annealing on the forged billet after coating. The annealing temperature is 340-480℃. After holding at this temperature for 1 hour, cool it in the furnace to complete the surface treatment process of the forged billet.

[0026] Optionally, the annealing temperature can be 340℃, 375℃, 410℃, 445℃ or 480℃, or any value between the above values.

[0027] In some optional embodiments, the hot rolling process to obtain a hot-rolled strip includes the following specific steps: Step C1: Heat the forging billet to 750-850℃ at a heating rate of 90-120℃ / h and hold for 2 hours; Optionally, the heating rate can be 90℃ / h, 98℃ / h, 105℃ / h, 112℃ / h or 120℃ / h, or any value between the above values; Optionally, the heating temperature can be 750℃, 775℃, 800℃, 825℃ or 850℃, or any value between the above values.

[0028] Step C2: Heat the temperature to 1080-1150℃ at a heating rate of 110-150℃ / h, hold for 3 hours, and then carry out the rolling operation; wherein the initial rolling temperature is greater than or equal to 1040℃ and the final rolling temperature is greater than or equal to 900℃. Optionally, the heating rate can be 110℃ / h, 120℃ / h, 130℃ / h, 140℃ / h or 150℃ / h, or any value between the above values; Optionally, the heating temperature can be 1080℃, 1098℃, 1115℃, 1132℃ or 1150℃, or any value between the above values; Optionally, the initial rolling temperature can be 1040℃, 1065℃, 1090℃, 1115℃ or 1140℃, or any value between the above values; Optionally, the final rolling temperature can be 900℃, 925℃, 950℃, 975℃ or 1000℃, or any value between the above values.

[0029] Step C3: After rolling is completed, hot-rolled strip blanks are obtained.

[0030] Step S2: The hot-rolled strip is subjected to dehydrogenation treatment, continuous annealing, leveling, graded pickling, and mechanical finishing in sequence to obtain a clean hot-rolled strip; wherein, the dehydrogenation treatment temperature is 700-750℃, the holding time is 2.5-4h, and the leveling deformation is 5%-12%; Optionally, the dehydrogenation treatment temperature can be 700℃, 712℃, 725℃, 738℃ or 750℃, or any value between the above values; Optionally, the dehydrogenation holding time can be 2.5h, 2.9h, 3.2h, 3.6h or 4h, or any value between the above values; Optionally, the flattening deformation amount can be 5%, 6.8%, 8.5%, 10.2% or 12%, or any value between the above values.

[0031] In some optional embodiments, the graded pickling of the hot-rolled strip includes the following specific steps: Hot-rolled strip billets are pre-pickled using a sulfuric acid solution containing steel corrosion inhibitors and a mass concentration of 15%–22%, with the pickling temperature controlled at 55–73°C. After pre-pickling, the hot-rolled strip is subjected to final pickling using a composite solution of 14%–22% hydrochloric acid and 0.7%–1.6% hydrofluoric acid. The pickling temperature is controlled at 43–51°C, and the acid solution is kept circulating throughout the pickling process to complete the graded pickling process.

[0032] Optionally, the mass concentration of the sulfuric acid solution can be 15%, 16.7%, 18.4%, 20.1% or 22%, or any value between the above values; Optionally, the pre-pickling temperature can be 55℃, 59℃, 63℃, 68℃ or 73℃, or any value between the above values; Optionally, the mass concentration of hydrochloric acid can be 14%, 16%, 18%, 20% or 22%, or any value between the above values; Optionally, the mass concentration of hydrofluoric acid can be 0.7%, 0.9%, 1.2%, 1.4% or 1.6%, or any value between the above values; Optionally, the final pickling temperature can be 43℃, 45℃, 47℃, 49℃ or 51℃, or any value between the above values.

[0033] In some optional embodiments, the hot-rolled strip that has undergone graded pickling is mechanically finished, including the following specific steps: The hot-rolled strip is polished using a 60-120 mesh flap wheel at a speed of 2800-3200 r / min and a grinding head pressure of 0.2-0.3 MPa. After grinding, the surface of the blank is polished using a 0.2mm steel wire brush; After polishing, compressed air is used to blow away any remaining debris on the surface of the strip blank to obtain a clean hot-rolled strip blank.

[0034] Optionally, the mesh count of the leaf blade can be 60, 80, 100, 120, or any value between the above values; Optionally, the grinding speed of the flap wheel can be 2800 r / min, 2900 r / min, 3000 r / min, 3100 r / min or 3200 r / min, or any value between the above values; Optionally, the grinding head pressure can be 0.2MPa, 0.22MPa, 0.25MPa, 0.28MPa or 0.3MPa, or any value between the above values.

[0035] Step S3: The clean hot-rolled strip is cold-rolled, trimmed, and continuously annealed to obtain a primary cold-rolled strip; In some optional embodiments, the clean hot-rolled strip is cold-rolled, trimmed, and continuously annealed to obtain a single cold-rolled strip, including the following specific steps: Clean hot-rolled strip is cold-rolled for 5 to 8 passes using work rolls with a profile arithmetic mean deviation of 0.2 μm, with the total deformation controlled at 50% to 60%, and rolling oil is continuously sprayed during the rolling process; Optionally, the number of cold rolling passes can be 5, 6, 6.5, 7 or 8, or any value between the above values; Optionally, the total deformation can be 50%, 52.5%, 55%, 57.5% or 60%, or any value between the above values.

[0036] The strip blank after the initial blanking is cut is trimmed on both sides. After the edges are trimmed, continuous annealing is performed to obtain a cold-rolled strip.

[0037] Step S4: Perform surface finishing, multiple cold rolling passes and continuous annealing on the cold-rolled strip to obtain a cold-rolled strip blank for insulated foil.

[0038] In some optional embodiments, surface finishing of the cold-rolled strip includes the following specific steps: The cold-rolled strip is polished using an 800-1600 mesh abrasive belt. The belt running speed is 15-30 m / s, and the polishing pressure is controlled at 0.12-0.17 MPa. After grinding, the surface of the blank is rinsed with high-pressure water and squeezed dry to thoroughly remove surface debris and complete the surface finishing process.

[0039] Optionally, the mesh size of the abrasive belt can be 800 mesh, 1000 mesh, 1200 mesh, 1500 mesh or 1600 mesh, or any value between the above values; Optionally, the linear speed of the sand belt can be 15m / s, 18m / s, 22m / s, 26m / s or 30m / s, or any value between the above values; Optionally, the grinding pressure can be 0.12MPa, 0.13MPa, 0.145MPa, 0.16MPa or 0.17MPa, or any value between the above values.

[0040] In some optional embodiments, the surface-finished cold-rolled strip is subjected to multiple cold rolling and continuous annealing passes to obtain a cold-rolled strip blank for Invar foil, including the following specific steps: The cold rolling process is carried out in 6 to 10 passes using work rolls with a profile arithmetic mean deviation of 0.15 μm, with the last two passes using work rolls with a profile arithmetic mean deviation of 0.08 μm. The total deformation during cold rolling is controlled at 55% to 65%, and the rolling oil supply flow rate is maintained at 500 to 1000 L / h during the rolling process; After cold rolling, continuous annealing is performed to obtain cold-rolled strip blanks for insulated foil materials.

[0041] Optionally, the number of cold rolling passes can be 6, 7, 8, 9 or 10, or any value between the above values; Optionally, the total deformation of cold rolling can be 55%, 57.5%, 60%, 62.5% or 65%, or any value between the above values; Optionally, the rolling oil supply flow rate can be 500L / h, 625L / h, 750L / h, 875L / h or 1000L / h, or any value between the above values.

[0042] In some alternative embodiments, the Invar alloy ingot is prepared by a consumable remelting process.

[0043] The technical solution of this application will be described in detail below with reference to specific embodiments and comparative examples.

[0044] Example 1 The first step is to grade the inclusions in the Invar alloy ingots that have undergone consumable remelting. The ingots must be free of inclusions of type A, B, C, and DS in the upper, middle, and lower parts, and the grade of type D inclusions must be ≤0.5 to ensure that the alloy ingots have high purity.

[0045] The second step is to heat and forge the alloy ingot from the first step to obtain forging billet I; The third step is to perform surface treatment on the forging blank I obtained in the second step to obtain forging blank II; The fourth step is to heat and roll the forging billet II obtained in the third step to obtain hot-rolled strip billet I; The fifth step involves dehydrogenation and surface treatment of the hot-rolled strip I obtained in the fourth step to obtain hot-rolled strip II. The sixth step involves cold rolling and continuous annealing the hot-rolled strip blank II obtained in the fifth step to obtain cold-rolled strip I; Step 7: After surface treatment, cold rolling and continuous annealing of the cold-rolled strip I obtained in step 6, cold-rolled strip II is obtained, which is a high-quality Invar alloy strip blank that can be used to roll foil.

[0046] In the second step, heat to 800℃ at a rate of 85℃ / h, hold for 3 hours, then heat to 1100℃ at a rate of 125℃ / h, hold for 3 hours, and then begin forging. The initial forging temperature is controlled at ≥1040℃, and the final forging temperature is controlled at ≥900℃. After forging, air cool. The forging specifications are δ110*300mm. In the third step, resin-bonded corundum grinding wheels are used to regrind forging blank I. A 40-grit wheel is used for rough grinding, and a 120-grit wheel for finish grinding. Sufficient flow of emulsion is used for cooling throughout the grinding process, and the surface temperature of the forging blank should be ≤85℃. Because Invar alloy has poor thermal conductivity and is prone to micro-cracks when locally overheated, ordinary alumina grinding wheels should be avoided to prevent surface burns. After grinding, an anti-oxidation coating is applied to the surface, followed by stress-relief annealing at 450℃, holding for 1 hour, and then furnace cooling to stabilize the overall dimensions and expansion of the forging blank.

[0047] In the fourth step, the temperature is raised to 850℃ at a rate of 120℃ / h and held for 2 hours. Then, it is raised to 1100℃ at a rate of 130℃ / h and held for 3 hours before rolling begins. The initial rolling temperature is controlled at ≥1040℃, and the final rolling temperature is controlled at ≥900℃. After rolling, the temperature is air-cooled, and the hot-rolled thickness is δ4.0~δ4.5mm.

[0048] In the fifth step, the hot-rolled strip I is placed in a dehydrogenation furnace and held at 730°C for 4 hours to promote the dissipation of hydrogen inside the strip, thereby reducing the risk of hydrogen-induced cracking in the later stage and the surface defects of the strip caused by hydrogen diffusion.

[0049] After dehydrogenation, the hot-rolled strip I undergoes continuous annealing, leveling, and pickling. Continuous annealing aims to soften the oxide scale, keeping it in a loose state. Leveling deformation is controlled at 5% to 12% to break up the scale, maintaining minimal deformation to avoid the risk of scale intrusion and further cracking the scale, facilitating subsequent pickling and descaling. Pickling employs a pre-pickling + final pickling method, achieving a triple effect of removing thick oxide scale, preventing over-corrosion, and surface passivation. Pre-pickling uses 16%–19% industrial sulfuric acid + steel buffer, with the acid temperature controlled at 61–68°C. Final pickling uses 14%–18% industrial hydrochloric acid + 1.0%–1.4% industrial hydrofluoric acid, with the acid temperature controlled at 46–51°C. The acid solution is continuously circulated to ensure uniform concentration.

[0050] After pickling, the surface of the strip blank is ground on the strip grinding line using an 80-mesh flap wheel at a speed of 3200 r / min and a grinding head pressure of 0.2~0.3 MPa. Then, a 0.2 mm steel wire brush is used for polishing, and compressed air is used to blow the surface at the exit of the grinding line.

[0051] In step six, the hot-rolled strip II is cold-rolled using 0.2μm work rolls for six rolling passes, with the total deformation controlled at 50%-60%, the oil spraying amount at 3800L / min, and the cold-rolled thickness at δ1.5~δ1.8mm. After blanking, the edges are trimmed by 5mm on each side, followed by continuous annealing.

[0052] In step seven, the surface of cold-rolled strip I is treated using a 1200-mesh abrasive belt. The belt material is abrasive aggregate, the grinding head pressure is 0.12~0.17MPa, and the linear speed is controlled at 28m / s. A high-pressure water gun and squeeze rollers are used for abrasive cleaning at the grinding line exit. Then, cold rolling is performed using 0.15μm work rolls in eight passes. The surface roughness requirement for the last two passes is 0.08μm, the total deformation is 55%~65%, the oil spray rate is 810L / min, and the cold-rolled thickness is δ0.5~δ0.8mm. Continuous annealing is then performed after rolling.

[0053] Example 2 The first step is to grade the inclusions in the Invar alloy ingots that have undergone consumable remelting. The ingots must be free of inclusions of type A, B, C, and DS in the upper, middle, and lower parts, and the grade of type D inclusions must be ≤0.5 to ensure that the alloy ingots have high purity.

[0054] The second step is to heat and forge the alloy ingot from the first step to obtain forging billet I; The third step is to perform surface treatment on the forging blank I obtained in the second step to obtain forging blank II; The fourth step is to heat and roll the forging billet II obtained in the third step to obtain hot-rolled strip billet I; The fifth step involves dehydrogenation and surface treatment of the hot-rolled strip I obtained in the fourth step to obtain hot-rolled strip II. The sixth step involves cold rolling and continuous annealing the hot-rolled strip blank II obtained in the fifth step to obtain cold-rolled strip I; Step 7: After surface treatment, cold rolling and continuous annealing of the cold-rolled strip I obtained in step 6, cold-rolled strip II is obtained, which is a high-quality Invar alloy strip blank that can be used to roll foil.

[0055] In the second step, heat to 800℃ at a rate of 70℃ / h, hold for 3 hours, then heat to 1100℃ at a rate of 110℃ / h, hold for 3 hours, and then begin forging. The initial forging temperature is controlled at ≥1040℃, and the final forging temperature is controlled at ≥900℃. After forging, air cool. The forging specifications are δ110*300mm. In the third step, resin-bonded corundum grinding wheels are used to regrind forging blank I. A 40-grit wheel is used for rough grinding, and a 120-grit wheel for finish grinding. Sufficient flow of emulsion is used for cooling throughout the grinding process, and the surface temperature of the forging blank should be ≤85℃. Because Invar alloy has poor thermal conductivity and is prone to micro-cracks when locally overheated, ordinary alumina grinding wheels should be avoided to prevent surface burns. After grinding, an anti-oxidation coating is applied to the surface, followed by stress-relief annealing at 450℃, holding for 1 hour, and then furnace cooling to stabilize the overall dimensions and expansion of the forging blank.

[0056] In the fourth step, the temperature is raised to 850℃ at a rate of 100℃ / h and held for 2 hours. Then, it is raised to 1100℃ at a rate of 120℃ / h and held for 3 hours before rolling begins. The initial rolling temperature is controlled at ≥1040℃, and the final rolling temperature is controlled at ≥900℃. After rolling, the temperature is air-cooled, and the hot-rolled thickness is δ4.0~δ4.5mm.

[0057] In the fifth step, the hot-rolled strip I is placed in a dehydrogenation furnace and held at 730°C for 4 hours to promote the dissipation of hydrogen inside the strip, thereby reducing the risk of hydrogen-induced cracking in the later stage and the surface defects of the strip caused by hydrogen diffusion.

[0058] After dehydrogenation, the hot-rolled strip I undergoes continuous annealing, leveling, and pickling. Continuous annealing aims to soften the oxide scale, keeping it in a loose state. Leveling deformation is controlled at 5% to 12% to break up the scale, maintaining minimal deformation to avoid the risk of scale intrusion and further cracking the scale, facilitating subsequent pickling and descaling. Pickling employs a pre-pickling + final pickling method, achieving a triple effect of removing thick oxide scale, preventing over-corrosion, and surface passivation. Pre-pickling uses 16%–19% industrial sulfuric acid + steel buffer, with the acid temperature controlled at 61–68°C. Final pickling uses 14%–18% industrial hydrochloric acid + 1.0%–1.4% industrial hydrofluoric acid, with the acid temperature controlled at 46–51°C. The acid solution is continuously circulated to ensure uniform concentration.

[0059] After pickling, the surface of the strip blank is ground on the strip grinding line using an 80-mesh flap wheel at a speed of 3000 r / min and a grinding head pressure of 0.2~0.3 MPa. Then, a 0.2 mm steel wire brush is used for polishing, and compressed air is used to blow the surface at the exit of the grinding line.

[0060] In step six, the hot-rolled strip II is cold-rolled using 0.2μm work rolls for six rolling passes, with the total deformation controlled at 50%-60%, the oil spraying amount at 2000L / min, and the cold-rolled thickness at δ1.5~δ1.8mm. After blanking, the edges are trimmed by 5mm on each side, followed by continuous annealing.

[0061] In step seven, the surface of cold-rolled strip I is treated using a 1200-mesh abrasive belt. The belt material is abrasive aggregate, the grinding head pressure is 0.12~0.17MPa, and the linear speed is controlled at 22m / s. A high-pressure water gun and squeeze rollers are used for abrasive cleaning at the grinding line exit. Then, cold rolling is performed using 0.15μm work rolls in eight passes. The surface roughness requirement for the last two passes is 0.08μm, the total deformation is 55%~65%, the oil spray rate is 900L / min, and the cold-rolled thickness is δ0.5~δ0.8mm. Continuous annealing is then performed after rolling.

[0062] Example 3 The first step is to grade the inclusions in the Invar alloy ingots that have undergone consumable remelting. The ingots must be free of inclusions of type A, B, C, and DS in the upper, middle, and lower parts, and the grade of type D inclusions must be ≤0.5 to ensure that the alloy ingots have high purity.

[0063] The second step is to heat and forge the alloy ingot from the first step to obtain forging billet I; The third step is to perform surface treatment on the forging blank I obtained in the second step to obtain forging blank II; The fourth step is to heat and roll the forging billet II obtained in the third step to obtain hot-rolled strip billet I; The fifth step involves dehydrogenation and surface treatment of the hot-rolled strip I obtained in the fourth step to obtain hot-rolled strip II. The sixth step involves cold rolling and continuous annealing the hot-rolled strip blank II obtained in the fifth step to obtain cold-rolled strip I; Step 7: After surface treatment, cold rolling and continuous annealing of the cold-rolled strip I obtained in step 6, cold-rolled strip II is obtained, which is a high-quality Invar alloy strip blank that can be used to roll foil.

[0064] In the second step, heat to 800℃ at a rate of 90℃ / h, hold for 3 hours, then heat to 1100℃ at a rate of 140℃ / h, hold for 3 hours, and then begin forging. The initial forging temperature is controlled at ≥1040℃, and the final forging temperature is controlled at ≥900℃. After forging, air cool. The forging specifications are δ110*300mm. In the third step, resin-bonded corundum grinding wheels are used to regrind forging blank I. A 40-grit wheel is used for rough grinding, and a 120-grit wheel for finish grinding. Sufficient flow of emulsion is used for cooling throughout the grinding process, and the surface temperature of the forging blank should be ≤85℃. Because Invar alloy has poor thermal conductivity and is prone to micro-cracks when locally overheated, ordinary alumina grinding wheels should be avoided to prevent surface burns. After grinding, an anti-oxidation coating is applied to the surface, followed by stress-relief annealing at 450℃, holding for 1 hour, and then furnace cooling to stabilize the overall dimensions and expansion of the forging blank.

[0065] In the fourth step, the temperature is raised to 850℃ at a rate of 110℃ / h and held for 2 hours. Then, it is raised to 1100℃ at a rate of 145℃ / h and held for 3 hours before rolling begins. The initial rolling temperature is controlled at ≥1040℃, and the final rolling temperature is controlled at ≥900℃. After rolling, the temperature is air-cooled, and the hot-rolled thickness is δ4.0~δ4.5mm.

[0066] In the fifth step, the hot-rolled strip I is placed in a dehydrogenation furnace and held at 730°C for 4 hours to promote the dissipation of hydrogen inside the strip, thereby reducing the risk of hydrogen-induced cracking in the later stage and the surface defects of the strip caused by hydrogen diffusion.

[0067] After dehydrogenation, the hot-rolled strip I undergoes continuous annealing, leveling, and pickling. Continuous annealing aims to soften the oxide scale, keeping it in a loose state. Leveling deformation is controlled at 5% to 12% to break up the scale, maintaining minimal deformation to avoid the risk of scale intrusion and further cracking the scale, facilitating subsequent pickling and descaling. Pickling employs a pre-pickling + final pickling method, achieving a triple effect of removing thick oxide scale, preventing over-corrosion, and surface passivation. Pre-pickling uses 16%–19% industrial sulfuric acid + steel buffer, with the acid temperature controlled at 61–68°C. Final pickling uses 14%–18% industrial hydrochloric acid + 1.0%–1.4% industrial hydrofluoric acid, with the acid temperature controlled at 46–51°C. The acid solution is continuously circulated to ensure uniform concentration.

[0068] After pickling, the surface of the strip blank is ground on the strip grinding line using an 80-mesh flap wheel at a speed of 2800 r / min and a grinding head pressure of 0.2~0.3 MPa. Then, a 0.2 mm steel wire brush is used for polishing, and compressed air is used to blow the surface at the exit of the grinding line.

[0069] In step six, the hot-rolled strip II is cold-rolled using 0.2μm work rolls for six rolling passes, with the total deformation controlled at 50%-60%, the oil spraying amount at 3000L / min, and the cold-rolled thickness at δ1.5~δ1.8mm. After blanking, the edges are trimmed by 5mm on each side, followed by continuous annealing.

[0070] In step seven, the surface of cold-rolled strip I is treated using a 1200-mesh abrasive belt. The belt material is abrasive aggregate, the grinding head pressure is 0.12~0.17MPa, and the linear speed is controlled at 16m / s. A high-pressure water gun and squeeze rollers are used for abrasive cleaning at the grinding line exit. Then, cold rolling is performed using 0.15μm work rolls in eight passes. The surface roughness requirement for the last two passes is 0.08μm, the total deformation is 55%~65%, the oil spray rate is 990L / min, and the cold-rolled thickness is δ0.5~δ0.8mm. Continuous annealing is then performed after rolling.

[0071] Comparative Example 1 Hot-rolled strip I is not subjected to dehydrogenation treatment, otherwise it is the same as in Example 1.

[0072] Comparative Example 2 The surface of hot-rolled strip II is ground using a 40-mesh flap wheel, without using a wire brush for polishing, and otherwise it is the same as in Example 1.

[0073] Comparative Example 3 Cold-rolled strip II was rolled using only 0.15μm work rolls, with 5 rolling passes, and the rest was the same as Comparative Example 2.

[0074] The surface inspection and performance testing results of Example 1 and Comparative Examples 1, 2, and 3 are as follows.

[0075] Table 1 Surface Inspection Results Table 2 Comprehensive Performance of Strip Table 1 shows the surface conditions of the cold-rolled strips obtained in Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3. The test results show that Example 1 has the best overall effect, with both surface roughness and surface defect control meeting the expected targets. Comparative Example 1 did not undergo dehydrogenation treatment, resulting in hydrogen-induced white spots and cracks on the strip surface. Comparative Example 2 omitted the wire brush polishing process, leaving residual hot-rolled oxide scale on the strip surface, which caused oxide scale indentation and localized peeling defects during subsequent cold rolling. Comparative Example 3 reduced the number of cold rolling passes, increasing the deformation per pass, leading to hidden indentation defects inside the strip, and simultaneously increasing the roll surface copying effect, resulting in roll marks on the strip surface.

[0076] Table 2 shows the overall performance of the cold-rolled strips obtained in Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3. The data indicates that Example 1 exhibits the best overall performance. Comparative Example 1 shows white spots and cracks on the strip surface, which easily induces stress concentration during room temperature tensile testing, leading to a decrease in material strength. Comparative Example 2 shows insufficient oxide scale removal, primarily deteriorating the strip surface quality, with a relatively limited impact on the mechanical properties of the matrix itself. Comparative Example 3 shows excessive single-pass deformation, resulting in uneven transverse deformation of the strip and causing problems such as poor strip shape and uneven grain size distribution.

[0077] This application aims to protect a method for preparing cold-rolled strip blanks for Invar foil. The technical solution of this application, by implementing graded constraint of non-metallic inclusions at the head, middle and tail of the Invar alloy ingot casting, precisely controls the inclusion level at different locations, which can avoid local plasticity differences caused by uneven axial inclusion distribution in the ingot and prevent local stress concentration in the subsequent rolling stage. At the same time, the dehydrogenation parameters of 700-750℃ and holding for 2.5-4h are matched with 5%-12% leveling deformation. On the one hand, it promotes the directional diffusion and precipitation of hydrogen atoms, reduces the risk of hydrogen-induced microcrack initiation, and on the other hand, it breaks the continuous oxide structure of the surface layer by moderate plastic deformation, which facilitates subsequent pickling and mechanical finishing to remove the oxide layer. The cooperation of each process reduces hydrogen-induced defects and surface oxide residues inside the strip blank, suppresses pinholes and roll-through defects induced by inclusions and oxide scale during ultra-thin rolling, improves the uniformity of the strip blank in the thickness direction, ensures the dimensional stability of the subsequent ultra-thin Invar foil, and meets the requirements of high-end precision devices.

[0078] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this application and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this application should be included within the protection scope of this application. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a high-quality cold-rolled strip blank for invar foil, characterized in that, include: Invar alloy ingots are heated and forged to obtain forging blanks. The forging blanks are then surface-treated and hot-rolled to obtain hot-rolled strip blanks. The hot-rolled strip is subjected to dehydrogenation treatment, continuous annealing, leveling, graded pickling, and mechanical finishing in sequence to obtain a clean hot-rolled strip; wherein the dehydrogenation treatment temperature is 700-750℃, the holding time is 2.5-4h, and the leveling deformation is 5%-12%; The clean hot-rolled strip is cold-rolled, trimmed, and continuously annealed to obtain a primary cold-rolled strip. The cold-rolled strip is surface finished, subjected to multiple cold rolling passes and continuous annealing to obtain a cold-rolled strip blank for insulated foil.

2. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, The process of heating and forging the Invar alloy ingot to obtain a forging billet includes: The Invar alloy ingot was heated to 700-820°C at a heating rate of 65-90°C / h and held for 3 hours. Then, the temperature is increased to 1080-1150℃ at a heating rate of 100-140℃ / h, and held for 3 hours before forging. The initial forging temperature is greater than or equal to 1040℃, and the final forging temperature is greater than or equal to 900℃. After forging is completed, a forging blank is obtained.

3. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, The surface treatment of the forging billet includes: The forging blank is graded and polished using resin corundum grinding wheels. For rough grinding, 40-80 grit grinding wheels are used, and for fine grinding, 120 grit grinding wheels are used. During the polishing process, emulsion is used for continuous cooling to control the surface temperature of the forging blank to be less than or equal to 85°C. Apply an anti-oxidation coating to the surface of the forged billet after grinding; The forging billet after coating is subjected to stress-relief annealing at a temperature of 340–480°C. After holding at this temperature for 1 hour, it is cooled in the furnace to complete the surface treatment process of the forging billet.

4. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, Heating and hot rolling to obtain hot-rolled strip billets, including: The forging billet is heated to 750-850℃ at a heating rate of 90-120℃ / h and held for 2 hours. Then, the temperature is increased to 1080-1150℃ at a heating rate of 110-150℃ / h, and held for 3 hours before rolling. The initial rolling temperature is greater than or equal to 1040℃, and the final rolling temperature is greater than or equal to 900℃. After rolling, hot-rolled strip blanks are obtained.

5. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, The graded pickling of the hot-rolled strip includes: Hot-rolled strip billets are pre-pickled using a sulfuric acid solution containing steel corrosion inhibitors and a mass concentration of 15%–22%, with the pickling temperature controlled at 55–73°C. After pre-pickling, the hot-rolled strip is subjected to final pickling using a composite solution of 14%–22% hydrochloric acid and 0.7%–1.6% hydrofluoric acid. The pickling temperature is controlled at 43–51°C, and the acid solution is kept circulating throughout the pickling process to complete the graded pickling process.

6. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, Mechanical finishing of the hot-rolled strip after graded pickling includes: The hot-rolled strip is polished using a 60-120 mesh flap wheel at a speed of 2800-3200 r / min and a grinding head pressure of 0.2-0.3 MPa. After grinding, the surface of the blank is polished using a 0.2mm steel wire brush; After polishing, compressed air is used to blow away any remaining debris on the surface of the strip blank to obtain a clean hot-rolled strip blank.

7. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, The clean hot-rolled strip is subjected to cold rolling, edge trimming, and continuous annealing to obtain a primary cold-rolled strip, comprising: Clean hot-rolled strip is cold-rolled for 5 to 8 passes using work rolls with a profile arithmetic mean deviation of 0.2 μm, with the total deformation controlled at 50% to 60%, and rolling oil is continuously sprayed during the rolling process; The strip blank after the initial blanking is cut is trimmed on both sides. After the edges are trimmed, continuous annealing is performed to obtain a cold-rolled strip.

8. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, The surface finishing of the first-stage cold-rolled strip includes: The cold-rolled strip is polished using an 800-1600 mesh abrasive belt. The belt running speed is 15-30 m / s, and the polishing pressure is controlled at 0.12-0.17 MPa. After grinding, the surface of the blank is rinsed with high-pressure water and squeezed dry to thoroughly remove surface debris and complete the surface finishing process.

9. The method for preparing high-quality invar foil cold-rolled strip blank according to claim 1, characterized in that, The surface-finished cold-rolled strip is subjected to multiple cold rolling and continuous annealing passes to obtain a cold-rolled strip blank for invar foil, comprising: The cold rolling process is carried out in 6 to 10 passes using work rolls with a profile arithmetic mean deviation of 0.15 μm, with the last two passes using work rolls with a profile arithmetic mean deviation of 0.08 μm. The total deformation during cold rolling is controlled at 55% to 65%, and the rolling oil supply flow rate is maintained at 500 to 1000 L / h during the rolling process; After cold rolling, continuous annealing is performed to obtain cold-rolled strip blanks for insulated foil materials.

10. The method for preparing high-quality invar foil cold-rolled strip blank according to any one of claims 1 to 9, characterized in that, The Invar alloy ingot is prepared by a consumable remelting process.

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