A method for preparing a frame substrate for OLED

Abstract

The present invention relates to a method for preparing a Frame substrate for OLED, and the preparation process adopted is medium frequency furnace melting, LF refining, VD refining, pouring, surface treatment, hot rolling, solution treatment, leveling, flaw detection, water cutting, aging treatment, flattening, inspection, and finished product packaging. The present invention is subjected to a heat treatment system of solution treatment, leveling, aging treatment, and flattening, combined with the support and pressure provided by pressure-bearing tooling and pressure-applying tooling; it is convenient for industrial production and ensures that the straightness of the Frame substrate is ≤1.0mm and the expansion coefficient is ≤1.4×10 ‑6 / ℃.

Description

Technical Field

[0001] The invention belongs to the technical field of Invar alloy plates and relates to a method for preparing a Frame substrate for OLED. Background Art

[0002] Frames used in the OLED field have high requirements for alloy expansion coefficient and flatness. In the early stage, this product was mainly imported from abroad, which was far from conducive to the development of the domestic display industry in terms of cost and cycle. Currently, frames are usually cut from Invar alloy sheets. According to the provisions of YB / T 5241 "Low Expansion Iron-Nickel, Iron-Nickel-Cobalt Alloys", when the temperature range is between 20 and 100°C, the expansion coefficient of Invar alloy (Invar, 4J36) should be ≤1.5×10 -6 / ℃, it has an extremely low expansion coefficient.

[0003] The weight of a single frame is about 200Kg, and the corresponding weight of the Invar alloy sheet is about 500Kg. At present, the 1T medium frequency induction furnace, 5T medium frequency induction furnace, 3T vacuum induction furnace and other equipment commonly used in China to produce Invar alloy, the alloy ingot is sawed at the head and tail, the intermediate billet is sawed at the round head and the finished product is cut, not only the product yield rate is low, but also the production efficiency is low, and the processing cost and processing cycle are high. In addition, the conventional heat treatment process is used to treat the Invar alloy frame, and the obtained frame has a flatness of ≥1.5mm and an expansion coefficient of ≥1.5×10 -6 / ℃ (20~100℃) cannot meet the usage requirements of OLED. Summary of the invention

[0004] The problem solved by the present invention is to provide a method for preparing a frame substrate for OLED, which can obtain a flatness of ≤1.0mm and an expansion coefficient of ≤1.4×10 -6 / ℃ (20~100℃) Invar alloy Frame substrate has good product consistency and can realize domestic substitution of Frame.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A method for preparing a frame substrate for OLED, comprising the following operations:

[0007] 1) Prepare ingredients according to the chemical composition of Invar alloy;

[0008] The raw materials are added into the medium frequency induction furnace for smelting, and heated by a current of 500-900A. When molten steel is seen, lime is added for slag making. After the materials are completely melted, the temperature is raised to 1510-1530℃, and then the crucible is dumped and the slag is removed.

[0009] After slagging, 1-1.5% lime and 0.5-0.75% fluorite of the mass of molten steel are added to re-slag, and the temperature is raised to 1550-1570℃ with a current of 800-1200A. SiCa powder and Al powder are mixed for deoxidation during the heating process. After the slag is whitened, samples are taken for component analysis;

[0010] After the composition reaches the target value, the temperature is raised to 1610-1630℃ and then taken out of the furnace;

[0011] 2) The molten steel is transferred to the LF furnace for refining for 5 to 10 minutes, and deoxidized with SiCa powder / block and Al powder. After the slag is white, samples are taken for component analysis. If the components are insufficient, they are supplemented according to the component requirements;

[0012] The target value of LF furnace refining is S≤0.008%. When the composition reaches the target value, the temperature is raised to 1650-1670℃ before being discharged from the furnace.

[0013] 3) The molten steel is transferred to the VD furnace for refining, and the vacuum degree is maintained at ≤67Pa for more than 10 minutes, and the argon gas flow rate is controlled to keep the steel liquid surface from being exposed;

[0014] After the VD furnace is broken, soft argon is blown for ≥5 minutes. The bag is taken out of the furnace after the temperature reaches 1510-1530℃.

[0015] 4) After the ladle is hoisted from the VD furnace to the pouring position, pouring shall begin after at least 10 minutes of sedation, and the pouring system temperature shall be ≥80°C;

[0016] After the pouring is completed, a heat-generating agent is added to the mold; the plate is cooled and the mold is cooled to prepare an Invar alloy ingot;

[0017] 5) After the mold is cooled, the riser is sawn, and then the Invar alloy ingot is ground using a slab grinding machine to remove the oxide scale on the surface of the Invar alloy ingot, and a heat-resistant coating is applied;

[0018] 6) When the furnace temperature is ≤400°C, the Invar alloy ingot is loaded into the furnace, the temperature is raised to 840-860°C at 40-60°C / h and kept at this temperature for 2-4h, and then the temperature is raised to 1150-1180°C at 60-80°C / h. After keeping the temperature for 2-3h, the Invar alloy ingot is taken out of the furnace and hot rolled;

[0019] Rolling passes ≥ 10, total rolling deformation ≥ 80%; temperature control during rolling process, starting rolling temperature ≥ 900℃, final rolling temperature ≥ 800℃;

[0020] 7) After hot rolling, solution treatment is performed: when the furnace temperature is ≤400°C, the hot-rolled plates are loaded into the furnace, and the plates in each stack of hot-rolled plates are separated by an interval of 50 to 80 mm;

[0021] Heat up to 830-870℃ at 80-120℃ / h and keep warm for 1.5-2.5h. Cool with water after leaving the furnace until the hot rolled plate returns to red temperature ≤100℃;

[0022] After solution treatment, the plate is leveled and ultrasonically inspected according to AA grade flaw detection standards;

[0023] According to the frame size requirements, water jet cutting is performed on the plates that have passed the ultrasonic flaw detection;

[0024] Perform aging treatment on the cut Frame plates: When the furnace temperature is ≤300℃, install the Frame into the furnace, lay a pressure-bearing tooling at the bottom of each stack of Frame plates, and set a pressure tooling on the top;

[0025] Raise the temperature to 530-580℃ at 60-80℃ / h and keep it at that temperature for 6-8h, cool the furnace to below 200℃ and then air cool the furnace to obtain the Frame substrate;

[0026] 8) Check the flatness, expansion coefficient and inclusion content of the frame substrate, and package it after passing the test.

[0027] When melting in a medium frequency induction furnace:

[0028] The medium frequency induction furnace is a 20T medium frequency induction furnace for preparing Invar alloy ingots weighing more than 5T;

[0029] The smelting raw materials include pure iron, Fe-Ni return materials, electrolytic nickel plates, metallic manganese and crystalline silicon; wherein the electrolytic nickel plates need to be baked at 800-900° C. for 4 hours;

[0030] The amount of SiCa powder used is 0.15-0.30% of the mass of the molten steel, and the amount of Al powder used is 0.15-0.25% of the mass of the molten steel;

[0031] After the component analysis, the Mn and Si contents are supplemented according to the component test results;

[0032] Before the steel is taken out of the furnace, 0.1 to 0.15% of NiMg alloy by mass of the molten steel is added to the ladle.

[0033] During the LF furnace refining, the refining temperature is 1610-1650° C.; the amount of SiCa powder / block used is 0.15-0.25% of the mass of the molten steel, and the amount of Al powder used is 0.15-0.25% of the mass of the molten steel.

[0034] During the pouring, the pouring speed of the Invar alloy ingot body is 1.8-2.0 T / min, and the shrinkage feeding speed of the riser is 0.28-0.32 T / min;

[0035] In terms of mass percentage, the exothermic agent comprises 60-70% aluminum powder and 30-40% sodium nitrate; the amount of the exothermic agent is 0.2-0.6% of the mass of the molten steel;

[0036] Plate cooling ≥5h, mold cooling ≥12h.

[0037] The prepared Invar alloy ingot is a flat ingot weighing more than 5 tons;

[0038] In terms of mass percentage, the chemical composition of the Invar alloy ingot is controlled as follows: C≤0.015%, Mn≤0.30%, Si≤0.15%, P≤0.01%, S≤0.008%, Al≤0.10%, Mg≤0.02%, Ti≤0.10%, Ni=35.5~37.0%, O≤0.0015%, N≤0.0030%, H≤0.0001%, and the balance is Fe and unavoidable impurities.

[0039] In terms of mass percentage, the heat-resistant coating comprises 5-20% silicon dioxide, 35-65% aluminum oxide, 1-5% iron oxide, 1-10% titanium oxide and 20-30% distilled water.

[0040] Before hot rolling, the Invar alloy ingot is washed with high-pressure water to remove scale, and the water pressure is ≥20MPa;

[0041] During hot rolling, the first 4 to 5 passes are for transverse widening rolling, with the reduction controlled at 10 to 15%; the subsequent passes are for longitudinal rolling by rotation, with the reduction controlled at 20 to 30%.

[0042] During the solution treatment, 4 to 8 hot-rolled plates are placed in each stack, and the hot-rolled plates are separated by refractory bricks; the temperature is raised to 840 to 860°C at 80 to 120°C / h and kept warm for 1.5 to 2.5 hours. After the heat preservation is completed, the hot-rolled plates are hoisted and immersed in water for cooling. The cooling time is controlled based on the hot-rolled plate's red-return temperature ≤ 100°C;

[0043] The leveling is performed by using a leveling machine, and the leveling is performed so that the plate has no fluctuations when viewed visually;

[0044] During the aging treatment, the pressure-bearing tooling is a cast iron frame larger than the frame, and 4 to 8 frame plates are placed in sequence on the pressure-bearing tooling; the pressurizing tooling is a cast iron frame.

[0045] During the water jet cutting, the cutting size of the outer frame of the Frame is 1710×1115mm, and the cutting size of the inner frame is 1438×857mm; the dimensional tolerance is +3.0mm for the outer frame and -3.0mm for the inner frame;

[0046] The cast iron frames used as pressure-bearing fixtures and pressure-applying fixtures have the same dimensions, with an outer frame size of 80×(1750~1770)×(1150~1180)mm and an inner frame size of 80×1420×800mm.

[0047] During the inspection, the inspection platform size is 2000mm×2500mm; the mechanics, HRB, grain size and inclusion properties of the frame substrate are inspected at the same time;

[0048] If the flatness of the frame substrate does not meet the requirements, use a flattening machine to flatten it, or return it to the furnace for re-aging treatment; the pressure of the flattening machine is ≥500T;

[0049] The qualified frame substrate conditions are: flatness ≤ 1.0mm, expansion coefficient ≤ 1.4×10 -6 / ℃ (20~100℃), tensile strength is 400~500MPa, yield strength is 230~350MPa, HBW is 100~147, grain size is finer than grade 6, inclusions A+C=0, B+D≤1.5, DS≤1.0.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The preparation method of the Frame substrate for OLED provided by the present invention realizes the precise control of alloy composition through the processes of medium frequency furnace melting, LF furnace refining, VD furnace refining and pouring, and can obtain alloy ingots with excellent uniformity; the blanks after grinding and coating with heat-resistant coating can obtain plates with excellent surface through the optimized hot rolling process; the heat treatment ensures that the Frame substrate meets the requirements of flatness and expansion coefficient, and the heat treatment system of the present invention through solid solution treatment, leveling, aging treatment and flattening, combined with the support and pressure provided by the pressure-bearing tooling and the pressure-applying tooling, is convenient for industrial production and ensures that the flatness of the Frame substrate is ≤1.0mm and the expansion coefficient is ≤1.4×10 -6 / ℃.

[0052] The preparation method of the Frame substrate for OLED provided by the present invention has the advantages of large output, low cost and good product consistency by using a 20T medium frequency induction furnace, an LF refining furnace and a VD refining furnace to produce a large alloy ingot; however, the casting and cooling process of the large alloy ingot is a difficulty in obtaining high-quality alloy ingots. The present invention obtains an alloy ingot with a small number and a low variety of inclusions by controlling the casting speed and combining the cooling process of disk cooling and mold cooling; further, the rolling of the large alloy ingot is a difficulty in obtaining a hot-rolled plate with fine grains, uniform performance and good surface quality. The present invention controls the rolling temperature and the rolling passes to ensure the quality of the hot-rolled plate, thereby laying a foundation for the quality of the Frame substrate.

[0053] The preparation method of the Frame substrate for OLED provided by the present invention has high production efficiency on the basis of ensuring the quality of the Frame substrate: a 6.5T flat ingot is obtained by melting and pouring in a 20T medium-frequency induction furnace, and 27 Frames can be produced at one time, which greatly improves the production efficiency; and during the solution treatment and aging treatment, multiple sheets of the plate are stacked for treatment, and multiple stacks can be treated at one time, which can ensure the quality and improve the production efficiency.

[0054] The preparation method of the OLED frame substrate provided by the present invention has a uniform structure of the final product, a flatness of ≤1.0mm and an expansion coefficient of ≤1.4×10 -6 / ℃ (20~100℃), grain size is finer than level 6, inclusions A+C=0, B+D≤1.5, DS≤1.0, which can meet the requirements of OLED frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is the metallographic structure diagram of the product prepared in Example 1;

[0056] Figure 2 This is the metallographic structure diagram of the product prepared in Comparative Example 1;

[0057] Figure 3 This is the metallographic structure diagram of the product prepared in Comparative Example 2;

[0058] Figure 4 This is the metallographic structure diagram of the product prepared in Comparative Example 3;

[0059] Figure 5 This is a surface image of the hot-rolled plate prepared in Example 1;

[0060] Figure 6 This is a surface image of the hot-rolled plate prepared in Comparative Example 2;

[0061] Figure 7 This is a schematic diagram of a stack of Frame plates during aging treatment of the present invention;

[0062] Figure 8 This is a schematic diagram of the Frame substrate prepared by the present invention. DETAILED DESCRIPTION

[0063] The present invention is further described in detail below in conjunction with the embodiments, which are intended to explain the present invention rather than to limit it.

[0064] The present invention provides a method for preparing a Frame substrate for OLED, wherein the process route is: medium frequency furnace smelting → LF refining → VD refining → casting → surface treatment → hot rolling → solution treatment → leveling → flaw detection → water cutting → aging treatment → flattening → inspection → finished product packaging, wherein ensuring the flatness and expansion coefficient of the Frame substrate is a difficult point in the preparation.

[0065] The method for preparing the Frame substrate for OLED of the present invention comprises the following operations:

[0066] 1) Prepare ingredients according to the chemical composition of Invar alloy;

[0067] The raw materials are added into the medium frequency induction furnace for smelting, and heated by a current of 500-900A. When molten steel is seen, lime is added for slag making. After the materials are completely melted, the temperature is raised to 1510-1530℃, and then the crucible is dumped and the slag is removed.

[0068] After slagging, 1-1.5% lime and 0.5-0.75% fluorite of the mass of molten steel are added to re-slag, and the temperature is raised to 1550-1570℃ with a current of 800-1200A. SiCa powder and Al powder are mixed for deoxidation during the heating process. After the slag is whitened, samples are taken for component analysis;

[0069] After the composition reaches the target value, the temperature is raised to 1610-1630℃ and then taken out of the furnace;

[0070] 2) The molten steel is transferred to the LF furnace for refining for 5 to 10 minutes, and deoxidized with SiCa powder / block and Al powder. After the slag is white, samples are taken for component analysis. If the components are insufficient, they are supplemented according to the component requirements;

[0071] The target value of LF furnace refining is S≤0.008%. When the composition reaches the target value, the temperature is raised to 1650-1670℃ before being discharged from the furnace.

[0072] 3) The molten steel is transferred to the VD furnace for refining, and the vacuum degree is maintained at ≤67Pa for more than 10 minutes, and the argon gas flow rate is controlled to keep the steel liquid surface from being exposed;

[0073] After the VD furnace is broken, soft argon is blown for ≥5 minutes. The bag is taken out of the furnace after the temperature reaches 1510-1530℃.

[0074] 4) After the ladle is hoisted from the VD furnace to the pouring position, pouring shall begin after at least 10 minutes of sedation, and the pouring system temperature shall be ≥80°C;

[0075] After the pouring is completed, a heat-generating agent is added to the mold; the plate is cooled and the mold is cooled to prepare an Invar alloy ingot;

[0076] Specifically, in terms of mass percentage, the exothermic agent comprises 60-70% aluminum powder and 30-40% sodium nitrate; the amount of the exothermic agent is 0.2-0.6% of the mass of the molten steel;

[0077] 5) After the mold is cooled, the riser is sawn, and then the Invar alloy ingot is ground using a slab grinding machine to remove the oxide scale on the surface of the Invar alloy ingot, and a heat-resistant coating is applied;

[0078] Specifically, in terms of mass percentage, the heat-resistant coating comprises 5-20% silicon dioxide, 35-65% aluminum oxide, 1-5% iron oxide, 1-10% titanium oxide and 20-30% distilled water.

[0079] 6) When the furnace temperature is ≤400°C, the Invar alloy ingot is loaded into the furnace, the temperature is raised to 840-860°C at 40-60°C / h and kept at this temperature for 2-4h, and then the temperature is raised to 1150-1180°C at 60-80°C / h. After keeping the temperature for 2-3h, the Invar alloy ingot is taken out of the furnace and hot rolled;

[0080] Rolling passes ≥ 10, total rolling deformation ≥ 80%; temperature control during rolling process, starting rolling temperature ≥ 900℃, final rolling temperature ≥ 800℃;

[0081] 7) After hot rolling, solution treatment is performed: when the furnace temperature is ≤400°C, the hot-rolled plates are loaded into the furnace, and the plates in each stack of hot-rolled plates are separated by an interval of 50 to 80 mm;

[0082] Heat up to 830-870℃ at 80-120℃ / h and keep warm for 1.5-2.5h. Cool with water after leaving the furnace until the hot rolled plate returns to red temperature ≤100℃;

[0083] After solution treatment, the plate is leveled and ultrasonically inspected according to AA grade flaw detection standards;

[0084] According to the frame size requirements, water jet cutting is performed on the plates that have passed the ultrasonic flaw detection;

[0085] Perform aging treatment on the cut Frame plates: When the furnace temperature is ≤300℃, install the Frame into the furnace, lay a pressure-bearing tooling at the bottom of each stack of Frame plates, and set a pressure tooling on the top;

[0086] Raise the temperature to 530-580℃ at 60-80℃ / h and keep it at that temperature for 6-8h, cool the furnace to below 200℃ and then air cool the furnace to obtain the Frame substrate;

[0087] 8) Check the flatness, expansion coefficient and inclusion content of the frame substrate, and package it after passing the test.

[0088] The following is a detailed description of each step.

[0089] 1. Medium frequency induction furnace smelting:

[0090] The medium frequency induction furnace is a 20T medium frequency induction furnace for preparing Invar alloy ingots weighing more than 5T;

[0091] The smelting raw materials include pure iron, Fe-Ni return materials, electrolytic nickel plates, metallic manganese and crystalline silicon; wherein the electrolytic nickel plates need to be baked at 800-900° C. for 4 hours;

[0092] The amount of SiCa powder used is 0.15-0.30% of the mass of the molten steel, and the amount of Al powder used is 0.15-0.25% of the mass of the molten steel; further, the amount of SiCa powder and Al powder used is 0.15-0.20%;

[0093] After the component analysis, the Mn and Si contents are supplemented according to the component test results;

[0094] Before the steel is discharged from the furnace, 0.1 to 0.15% of the mass of the molten steel is added to the ladle with NiMg alloy (timing of adding the NiMg alloy: adding it to the ladle before the steel is discharged).

[0095] 2. LF furnace refining:

[0096] The molten steel enters the LF furnace for refining for 5 to 10 minutes, and the refining temperature is 1610 to 1650°C; SiCa blocks, SiCa powder, and Al powder are used for deoxidation, and the amount of SiCa powder / block is 0.15 to 0.25% of the mass of the molten steel, and the amount of Al powder is 0.15 to 0.25% of the mass of the molten steel; after the slag is whitened, sampling and analysis are performed, the slag system and chemical composition are adjusted, and additional materials are added when necessary;

[0097] The target value of LF furnace is S≤0.008%, temperature 1650~1670℃

[0098] 3. VD furnace refining:

[0099] After the molten steel enters the VD furnace, the vacuum degree is maintained at ≤67Pa for more than 10 minutes, and the argon flow rate is controlled in accordance with the principle that the molten steel surface is not exposed; during this period, the temperature of the molten steel decreases from 1610-1650℃ to about 1550℃ when it is discharged from the furnace;

[0100] After VD breaks through the air, soft blowing (continue to blow Ar) time ≥ 5min, and the bag is hung after the temperature reaches 1530±5℃.

[0101] 4. Pouring

[0102] The pouring system temperature is required to be ≥80℃. After the VD ladle is moved to the pouring position, the pouring begins after 10 minutes of sedation. During pouring, the pouring speed of the Invar alloy ingot is 1.8-2.0T / min, and the shrinkage feeding speed of the riser is 0.28-0.32T / min.

[0103] Add heat-generating agent after pouring; plate cooling ≥5h, mold cooling ≥12h.

[0104] 5. Surface treatment: After sawing the riser, use the slab grinder to grind the alloy ingot, remove the oxide scale on the surface of the alloy ingot, and then apply high-temperature paint.

[0105] 6. Hot rolling: Before hot rolling, use high-pressure water to wash the Invar alloy ingot to remove scale, and the water pressure should be ≥20MPa;

[0106] The furnace is charged at ≤400℃, and the temperature is increased to 850±10℃ at 40~60℃ / h and kept at this temperature for 2~4h. Then the temperature is increased to 1150~1180℃ at 60~80℃ / h and kept at this temperature for 2~3h before being taken out of the furnace; the starting rolling temperature is ≥900℃, and the final rolling temperature is ≥800℃; the temperature is controlled during the rolling process to obtain fine and uniform grains.

[0107] The number of rolling passes is ≥10, and the total rolling deformation is ≥80%. During hot rolling, the first 4 to 5 passes are for transverse widening rolling, and the reduction is controlled at 10 to 15%. The subsequent passes are rotated for longitudinal rolling, and the reduction is controlled at 20 to 30%.

[0108] 7. Solution treatment, leveling, flaw detection, water cutting, aging treatment, flattening: the solution + aging heat treatment process is used to make the expansion coefficient of the frame ≤1.4×10 -6 / ℃(20~100℃); Use bottom pad and upper pressure block to ensure the straightness of the Frame is ≤1.0mm;

[0109] Solution treatment: hot-rolled plates are loaded into the furnace at ≤400℃, with the thickness of each stack of plates being 50-80mm (separated by refractory bricks), and the temperature is raised to 850±10℃ at 80-120℃ / h and kept at this temperature for 1.5-2.5h, and then put into water (the time is controlled according to the red-return temperature ≤100℃), and the red-return temperature of the hot-rolled plates is ≤100℃ (after being put into water, the hot-rolled plates are hoisted up, and the surface temperature of the hot-rolled plates will rise to some extent);

[0110] Leveling: Generally, any leveling equipment that can be used to level 35mm plates can be used. The main purpose is to visually see that there is no obvious ups and downs. Specifically, the solid solution plate is leveled by an eleven-roller leveling machine.

[0111] Flaw detection and water cutting: Ultrasonic flaw detection is carried out according to AA-level flaw detection standards, and water cutting is carried out according to the frame size after flaw detection;

[0112] Aging treatment: a cast iron frame slightly larger than the frame is laid on the bottom of the heat treatment furnace, and then 4 to 8 frames are placed on the cast iron frame in sequence, and finally another cast iron frame is pressed on the top of the frame;

[0113] Specifically, during water jet cutting, the cutting size of the outer frame is 1710×1115mm, and the cutting size of the inner frame is 1438×857mm; the dimensional tolerance is +3.0mm for the outer frame and -3.0mm for the inner frame;

[0114] The cast iron frames used as pressure-bearing fixtures and pressure-applying fixtures have the same size, with an outer frame larger than the frame and an inner frame smaller than the finished product frame; for example, the outer frame size of the cast iron frame is 80×(1750~1770)×(1150~1180)mm, and the inner frame size is 80×1420×800mm.

[0115] The dimensional tolerance of water jet cutting is +3.0mm for the outer frame and -3.0mm for the inner frame.

[0116] 8. Flattening, inspection, and packaging: Inspect the straightness of the Frame on the inspection platform;

[0117] The inspection platform size is 2000mm×2500mm;

[0118] When the straightness does not meet the requirements, use a flattening machine to flatten it; if the straightness is not enough and the deformation is large, it needs to be returned to the furnace for aging treatment again;

[0119] At the same time, the material's expansion coefficient, mechanics, HRB, grain size, inclusions and other properties are tested; they are packaged after they pass the test.

[0120] Specific examples and comparative examples are given below.

[0121] Example 1

[0122] Alloy ingot preparation: Invar alloy was produced by medium frequency furnace melting → LF refining → VD refining → casting method, and a 6.5T flat ingot with a size of 240*1330*2200mm was obtained;

[0123] The composition of the Invar alloy ingot is: C 0.013%, Mn 0.25%, Si 0.10%, P 0.0088%, S < 0.001%, Al 0.050%, Ti 0.048%, Mg < 0.01%, Ni 35.99%, O 9.5ppm, N 16.5ppm, H 0.03ppm, and the balance is Fe;

[0124] The alloy ingot casting process is as follows: the ingot body casting speed is 1.96 T / min, and the riser shrinkage feeding speed is 0.29 T / min.

[0125] Frame preparation: The alloy ingot is ground after demoulding to remove the surface oxide scale;

[0126] After that, heat-resistant coating is applied and hot-rolled, and the finished product specifications are δ33*1810*L(mm);

[0127] Hot rolling: charge the furnace at room temperature, heat up to 850℃ at 40℃ / h and keep it for 3h, then heat up to 1150℃ at 80℃ / h and keep it for 2h before rolling. Descaling pressure is 20MPa, initial rolling temperature is 1050℃, widening rolling is carried out in the first four passes, the width is controlled at 1810mm, the reduction rate is controlled at 12%, and the subsequent passes are a total of seven passes, longitudinal rolling is carried out, the reduction rate is controlled at 21%, and the final rolling temperature is 850℃.

[0128] Solution treatment of hot-rolled plates: Load the furnace at room temperature, stack 6 hot-rolled plates, with a spacing of 80mm between each plate, heat up to 850℃ at 100℃ / h, keep warm for 2h, then take out of the furnace and put into water, the red-return temperature is 85℃.

[0129] Leveling, flaw detection, water cutting and aging treatment: The Invar alloy solid solution plate is leveled by an eleven-roller leveling machine and then water cut to obtain the Invar alloy frame;

[0130] Aging heat treatment process: room temperature furnace loading, 7 sheets per stack (such as Figure 7 As shown), there are 4 stacks in total, and the temperature is raised to 550℃ at 80℃ / h, kept at this temperature for 7h, and the furnace is cooled to 180℃ after power off and then cooled to room temperature.

[0131] Straightness test: The straightness of 25 frames is less than 1.0mm, and the straightness of 3 frames (all on the top) reaches 1.1mm. The straightness reaches 1.0mm after slight flattening with a 400T flattening machine.

[0132] The prepared Frame substrate is as follows Figure 8 As shown, its performance is: expansion coefficient 1.2×10 -6 / ℃ (20~100℃), tensile strength 498MPa, yield strength 310MPa, elongation 40.5%, HBW135, grain size 9.5, inclusions A+C=0, B0.5, D0.5, DS0.

[0133] Comparative Example 1:

[0134] Alloy ingot preparation: Invar alloy was produced by medium frequency furnace melting → LF refining → VD refining → casting method, and a 6.5T flat ingot with a size of 240*1330*2200mm was obtained;

[0135] The composition of the Invar alloy is: C 0.009%, Mn 0.23%, Si 0.08%, P 0.0068%, S < 0.001%, Al 0.030%, Ti 0.058%, Mg < 0.01%, Ni 35.79%, O 13ppm, N 20ppm, H 0.07ppm, and the balance is Fe;

[0136] The alloy ingot casting process is as follows: the ingot body casting speed is 1.85 T / min, and the riser shrinkage feeding speed is 0.28 T / min.

[0137] Frame preparation: After demoulding, the alloy ingot is ground to remove the surface oxide scale; then it is coated with heat-resistant paint and hot-rolled. The finished product specifications are δ33*1810*L(mm).

[0138] Hot rolling: charge the furnace at room temperature, heat up to 850℃ at 50℃ / h and keep it for 3h, then heat up to 1150℃ at 80℃ / h and keep it for 2h before rolling. Descaling pressure is 21MPa, initial rolling temperature is 980℃, widening rolling is carried out in the first four passes, the width is controlled at 1810mm, the reduction rate is controlled at 10%, and the subsequent passes are a total of seven passes, longitudinal rolling is carried out, the reduction rate is controlled at 22%, and the final rolling temperature is 830℃.

[0139] Solution treatment of hot-rolled plates: Load the furnace at room temperature, stack 6 hot-rolled plates, with a spacing of 60mm between each plate, heat up to 850℃ at 100℃ / h, keep warm for 2.5h, then take out of the furnace and put into water, the red-return temperature is 85℃.

[0140] Leveling, flaw detection, water cutting and aging treatment: The Invar alloy solid solution plate is leveled by an eleven-roller leveling machine and then water cut to obtain the Invar alloy frame;

[0141] Aging heat treatment process: load the furnace at room temperature, 9 sheets per stack, 4 stacks in total, heat up to 850℃ at 70℃ / h, keep warm for 8h, turn off the power and cool the furnace to 180℃ before taking it out of the furnace and cooling to room temperature.

[0142] Straightness detection: The straightness of 30 frames was less than 1.0mm, and the straightness of the remaining 6 frames reached 1.1-1.3mm. It took 18 hours to flatten the straightness of the 4 frames to 1.0mm using a 400T flattening machine.

[0143] Frame performance: Expansion coefficient 1.7×10 -6 / ℃ (20~100℃), tensile strength 488MPa, yield strength 308MPa, elongation 39.5%, HBW145, grain size 7.5, inclusions A+C=0, B1.0, D0.5, DS0.

[0144] Comparative Example 2:

[0145] Alloy ingot preparation: Invar alloy was produced by medium frequency furnace melting → LF refining → VD refining → casting method, and a 6.5T flat ingot with a size of 240*1330*2200mm was obtained;

[0146] The composition of the Invar alloy is: C 0.015%, Mn 0.21%, Si 0.08%, P 0.0087%, S < 0.001%, Al 0.010%, Ti 0.018%, Mg < 0.01%, Ni 36.05%, O 15ppm, N 28ppm, H 0.10ppm, and the balance is Fe; the alloy ingot casting process is: ingot body casting speed 1.84T / min, riser feeding speed 0.30T / min.

[0147] Frame preparation: The alloy ingot is polished after demoulding to remove the surface oxide scale; the finished product specification is δ33*1810*L(mm);

[0148] Hot rolling: charge the furnace at room temperature, heat up to 850℃ at 50℃ / h and keep it for 4h, then heat up to 1200℃ at 80℃ / h and keep it for 2h before rolling out of the furnace, descaling pressure is 20MPa, initial rolling temperature is 1000℃, widening rolling is carried out in the first three passes, the width is controlled at 1810mm, the reduction rate is controlled at 16%, and the subsequent passes are a total of seven passes, longitudinal rolling is carried out, the reduction rate is controlled at 20%, and the final rolling temperature is 830℃.

[0149] The hot-rolled plate surface cracked, and the sample was only used for subsequent solution treatment and aging treatment, without frame cutting.

[0150] Sample performance: Expansion coefficient 1.4×10 -6 / ℃ (20~100℃), tensile strength 476MPa, yield strength 288MPa, elongation 38.5%, HBW138, grain size 5.5, inclusions A+C=0, B0.5, D1.0, DS0.

[0151] Comparative Example 3:

[0152] Alloy ingot preparation: Invar alloy was produced by medium frequency furnace melting → LF refining → VD refining → casting method, and a 6.5T flat ingot with a size of 240*1330*2200mm was obtained;

[0153] The composition of the Invar alloy is: C 0.011%, Mn 0.28%, Si 0.15%, P 0.0098%, S <0.001%, Al 0.040%, Ti 0.048%, Mg <0.01%, Ni 35.90%, O 12ppm, N 25ppm, H0.11ppm, and the balance is Fe; the alloy ingot casting process is: ingot body casting speed 1.74T / min, riser feeding speed 0.28T / min.

[0154] Frame preparation: The alloy ingot is polished after demoulding to remove the surface oxide scale; the finished product specification is δ33*1810*L(mm);

[0155] Hot rolling: charge the furnace at room temperature, heat up to 850℃ at 60℃ / h and keep it for 2h, then heat up to 1150℃ at 80℃ / h and keep it for 3h before rolling. Descaling pressure is 20MPa, initial rolling temperature is 990℃, widening rolling is carried out in the first five passes, the width is controlled at 1810mm, the reduction rate is controlled at 11%, and the subsequent passes are a total of seven passes, longitudinal rolling is carried out, the reduction rate is controlled at 21%, and the final rolling temperature is 850℃.

[0156] Solution treatment of hot-rolled plates: Load the furnace at room temperature, stack 6 hot-rolled plates, with a spacing of 70mm between each plate, heat up to 840℃ at 80℃ / h, keep warm for 2h, then take out of the furnace and put into water, the red-return temperature is 95℃.

[0157] Leveling, flaw detection, water cutting and aging treatment: The Invar alloy solid solution plate is leveled by an eleven-roller leveling machine and then water cut to obtain the Invar alloy frame;

[0158] Aging heat treatment process: load the furnace at room temperature, 8 sheets per stack, 4 stacks in total, heat up to 550℃ at 60℃ / h, keep warm for 8h, turn off the power and cool the furnace to 150℃ before taking it out of the furnace and cooling to room temperature.

[0159] Straightness detection: The straightness of 30 frames was ≤1.0mm, and the straightness of the remaining 2 frames reached 1.2-1.3mm. It took 8 hours to flatten the 2 frames to 1.0mm using a 400T flattening machine.

[0160] Frame performance: Expansion coefficient 1.3×10 -6 / ℃ (20~100℃), tensile strength 485MPa, yield strength 298MPa, elongation 41.5%, HBW141, grain size 7.0, inclusions A+C=0, B1.0, D1.0, DS0.5.

[0161] The main production parameters of the implementation case and the comparative case are shown in Table 1.

[0162] Table 1 Comparison of preparation process between the embodiment and the comparative example

[0163]

[0164] It can be seen from Table 1 that the frame loading capacity in Comparative Example 1 does not meet the requirement of 4 to 8 sheets / stack, and the aging temperature is higher than that in Example 1; the hot rolling heating temperature in Comparative Example 2 is higher than that in Example 1; and the ingot casting speed in Comparative Example 3 is lower than that in Example 1.

[0165] The performance comparison of the prepared products is shown in Table 2. Figure 1 , Figure 2 , Figure 3 , Figure 4 shown.

[0166] Table 2 Comparison of the performance of the substrates prepared in the embodiment and the comparative example

[0167]

[0168] Combining Table 1 and Table 2, it can be seen that in Comparative Example 1, due to the large amount of Frame loaded in the furnace and the high aging temperature, the expansion coefficient of the finished product is higher than the requirement, and the flatness is unqualified accounting for 16.67%, which requires time and effort to level it; in Comparative Example 2, due to the high hot rolling temperature, the hot rolled plate has cracks, and the grain size tends to grow.

[0169] The inclusions are shown in Table 3.

[0170] Table 3 Comparison of substrate inclusions prepared in the embodiment and the comparative example

[0171]

[0172] In Comparative Example 3, the casting speed of the ingot body is slow, resulting in a large amount of inclusions and failing to meet the requirement of B+D≤1.5.

[0173] In summary, the inclusion content and grain size grade of the embodiment are optimal, and the straightness of the Frame produced according to the embodiment can meet the customer's requirements; the straightness of the comparative example 1 is 16.67% and cannot meet the customer's requirements, and needs to be repaired, but it is time-consuming and labor-intensive, and the production efficiency is not as good as the embodiment; the comparative example 2 has cracks during rolling due to improper hot working process (such as Figure 5 , Figure 6 Comparative Example 3 has a slower ingot casting speed and more inclusions (such as Figure 1-Figure 4 From the comparison of the metallographic structure diagram shown, it can be seen that the grain size of comparative example 3 is not fine enough).

[0174] The preparation method of the OLED frame substrate provided by the present invention has a uniform structure of the final product, a flatness of ≤1.0mm and an expansion coefficient of ≤1.4×10 -6 / ℃ (20-100℃), grain size finer than level 6, inclusions A+C=0, B+D≤1.5, DS≤1.0, can meet the use of OLED frame. The present invention not only ensures the quality of the frame substrate, but also has good production efficiency.

[0175] The above embodiments are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions and substitutions made by those skilled in the art based on the technical features of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a frame substrate for OLED, characterized in that: The following operations are included: 1) Prepare ingredients according to the chemical composition of Invar alloy; The raw materials are added into the medium frequency induction furnace for smelting, and heated by a current of 500~900A. When molten steel is seen, lime is added for slag making. After the materials are completely melted, the temperature is raised to 1510~1530℃, and then the crucible is dumped and the slag is removed. After slagging, 1~1.5% lime and 0.5~0.75% fluorite of the mass of molten steel are added to re-slag, and the temperature is raised to 1550~1570℃ with a current of 800~1200A. SiCa powder and Al powder are mixed for deoxidation during the heating process. After the slag is whitened, samples are taken for component analysis; After the composition reaches the target value, the temperature is raised to 1610~1630℃ and then taken out of the furnace; 2) The molten steel is transferred to the LF furnace for refining for 5-10 minutes, and deoxidized with SiCa powder or SiCa block and Al powder. After the slag is whitened, samples are taken for component analysis. If the components are insufficient, they are supplemented according to the component requirements; The target value of LF furnace refining is S≤0.008%. When the composition reaches the target value, the temperature is raised to 1650~1670℃ before being discharged from the furnace. 3) The molten steel is transferred to the VD furnace for refining, and the vacuum degree is maintained at ≤67Pa for more than 10 minutes. The argon gas flow rate is controlled to keep the steel liquid surface from being exposed; After the VD furnace is broken, soft argon is blown for ≥5 minutes. The bag is taken out of the furnace after the temperature reaches 1510~1530℃. 4) After the ladle is hoisted from the VD furnace to the pouring position, pouring shall begin after at least 10 minutes of sedation, and the pouring system temperature shall be ≥80°C; During pouring, the pouring speed of the Invar alloy ingot is 1.8~2.0T / min, and the shrinkage feeding speed of the riser is 0.28~0.32T / min; After pouring, a heat-generating agent is added to the mold; in terms of mass percentage, the heat-generating agent comprises 60-70% aluminum powder and 30-40% sodium nitrate; the amount of the heat-generating agent is 0.2-0.6% of the mass of the molten steel; Plate cooling ≥5h, mold cooling ≥12h, to prepare Invar alloy ingot; 5) After the mold is cooled, the riser is sawn, and then the Invar alloy ingot is ground using a slab grinding machine to remove the oxide scale on the surface of the Invar alloy ingot, and a heat-resistant coating is applied; 6) When the furnace temperature is ≤400℃, the Invar alloy ingot is loaded into the furnace, heated to 840~860℃ at 40~60℃ / h and kept at this temperature for 2~4h, then heated to 1150~1180℃ at 60~80℃ / h, kept at this temperature for 2~3h, and then the Invar alloy ingot is taken out of the furnace for hot rolling; Rolling passes ≥ 10, total rolling deformation ≥ 80%; temperature control during rolling process, starting rolling temperature ≥ 900℃, final rolling temperature ≥ 800℃; 7) After hot rolling, solution treatment is performed: when the furnace temperature is ≤400℃, the hot-rolled plates are loaded into the furnace, and the plates in each stack of hot-rolled plates are separated. Each stack has 4 to 8 hot-rolled plates, and the hot-rolled plates are separated by refractory bricks with a spacing of 50 to 80 mm; Heat up to 830~870℃ at 80~120℃ / h and keep warm for 1.5~2.5h. Cool with water after leaving the furnace until the hot rolled plate returns to red temperature ≤100℃; After solution treatment, the plate is leveled and ultrasonically inspected according to AA grade flaw detection standards; According to the frame size requirements, water cutting is performed on the plates that have passed the ultrasonic flaw detection; Perform aging treatment on the cut Frame plates: put the Frame into the furnace when the furnace temperature is ≤300℃, lay a pressure-bearing tooling at the bottom of each stack of Frame plates, place 4 to 8 Frame plates on the pressure-bearing tooling in sequence, and set a pressure tooling on the top; Heat up to 530~580℃ at 60~80℃ / h and keep warm for 6~8h, cool down to below 200℃ and air cool out of the furnace; Get the Frame substrate; 8) Check the flatness, expansion coefficient and inclusion content of the frame substrate, and package it after passing the test.

2. The method for preparing a Frame substrate for OLED according to claim 1, characterized in that: When melting in a medium frequency induction furnace: The medium frequency induction furnace is a 20T medium frequency induction furnace for preparing Invar alloy ingots weighing more than 5T; The smelting raw materials include pure iron, Fe-Ni return materials, electrolytic nickel plates, metallic manganese and crystalline silicon; wherein the electrolytic nickel plates need to be baked at 800-900° C. for 4 hours; The amount of SiCa powder used is 0.15~0.30% of the mass of molten steel, and the amount of Al powder used is 0.15~0.25% of the mass of molten steel; After the component analysis, the Mn and Si contents are supplemented according to the component test results; Before the steel is taken out of the furnace, 0.1~0.15% of NiMg alloy by mass of the molten steel is added to the ladle.

3. The method for preparing a Frame substrate for OLED according to claim 1, wherein: During LF furnace refining, the refining temperature is 1610~1650℃; the amount of SiCa powder or SiCa block is 0.15~0.25% of the mass of molten steel, and the amount of Al powder is 0.15~0.25% of the mass of molten steel.

4. The method for preparing a Frame substrate for OLED according to claim 1, 2 or 3, characterized in that: The prepared Invar alloy ingot is a flat ingot weighing more than 5 tons; In terms of mass percentage, the chemical composition of the Invar alloy ingot is controlled as follows: C≤0.015%, Mn≤0.30%, Si≤0.15%, P≤0.01%, S≤0.008%, Al≤0.10%, Mg≤0.02%, Ti≤0.10%, Ni=35.5~37.0%, O≤0.0015%, N≤0.0030%, H≤0.0001%, and the balance is Fe and unavoidable impurities.

5. The method for preparing a Frame substrate for OLED according to claim 1, wherein: In terms of mass percentage, the heat-resistant coating comprises 5-20% silicon dioxide, 35-65% aluminum oxide, 1-5% iron oxide, 1-10% titanium oxide and 20-30% distilled water.

6. The method for preparing a Frame substrate for OLED according to claim 1, wherein: Before hot rolling, the Invar alloy ingot is washed with high-pressure water to remove scale, and the water pressure is ≥20MPa; During hot rolling, the first 4 to 5 passes are for transverse widening rolling, and the reduction is controlled at 10 to 15%; the subsequent passes are rotated for longitudinal rolling, and the reduction is controlled at 20 to 30%.

7. The method for preparing a Frame substrate for OLED according to claim 1, wherein: During the solution treatment, the temperature is raised to 840~860℃ at 80~120℃ / h and kept at this temperature for 1.5~2.5h. After the heat preservation is completed, the hot-rolled plate is hoisted and immersed in water for cooling. The cooling time is controlled based on the hot-rolled plate's red-return temperature ≤100℃; The leveling is performed by using a leveling machine, and the leveling is performed so that the plate has no fluctuations when viewed visually; During the aging treatment, the pressure-bearing fixture is a cast iron frame whose size is larger than the frame; and the pressurizing fixture is a cast iron frame.

8. The method for preparing a Frame substrate for OLED according to claim 1 or 7, characterized in that: When cutting with water jet, the cutting size of the outer frame is 1710×1115mm, and the cutting size of the inner frame is 1438×857mm; the dimensional tolerance is +3.0mm for the outer frame and -3.0mm for the inner frame; The cast iron frames used as pressure-bearing fixtures and pressure-applying fixtures have the same dimensions, with outer frame dimensions of 80×1750~1770×1150~1180mm and inner frame dimensions of 80×1420×800mm.

9. The method for preparing a frame substrate for OLED according to claim 1, characterized in that: During the inspection, the inspection platform size is 2000mm×2500mm; the mechanical, HBW, grain size and inclusion properties of the frame substrate are inspected at the same time; If the flatness of the frame substrate does not meet the requirements, use a flattening machine to flatten it, or return it to the furnace for re-aging treatment; the pressure of the flattening machine is ≥500T; The qualified frame substrate conditions are: flatness ≤ 1.0mm, expansion coefficient of 20~100℃ ≤ 1.4×10 -6 / ℃, tensile strength is 400~500MPa, yield strength is 230~350MPa, HBW is 100~147, grain size is finer than level 6, inclusions A+C=0, B+D≤1.5, DS≤1.0.

Images