Fireproof door color steel plate and preparation process thereof
By using low-temperature annealing, degreasing and chromium-free passivation pretreatment in the hot-dip galvanizing and color coating process of color steel fireproof door panels, the problem of reduced adhesion of color steel fireproof door panels at high temperatures is solved, and the coating adhesion and fire resistance performance are improved.
Patent Information
- Application Number
- CN202510115862.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-24
- Publication Date
- 2025-06-24
AI Technical Summary
The adhesion performance of existing color steel fireproof door panels has decreased at high temperatures, resulting in the fall of the coating and substrate, which cannot achieve the expected fireproof performance. At the same time, there is a lack of research on the adhesion of color steel plates of fireproof doors.
The low-temperature annealing process is used for hot-dip galvanizing, combining degreasing and chromium-free passivation pretreatment processes to control the baking and coating baking temperature after passivation. The 2/2 coating structure is adopted to ensure the film thickness and viscosity control of the primer and topcoat and improve the adhesion of the coating.
It effectively improves the coating adhesion performance of the color steel plate of the fire door, ensures that it maintains good fire resistance under high temperature conditions, and improves processing and impact resistance.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of metal material manufacturing, and particularly relates to a color steel plate for fire doors and a preparation process thereof. Background Art
[0002] Color steel fire doors usually adopt color steel sandwich panels. Taking cold-rolled plates, hot-dip galvanized plates, hot-dip aluminum-zinc plates, etc. as substrates, after coating with a colored coating, a colored coated steel plate is formed. Then, using this colored coated steel plate as the facing material and fireproof materials such as rock wool as the core material, a super-light building board is formed by compounding. The color steel fire door panel has the characteristics of light self-weight, heat preservation and heat insulation, high strength, bending and compression resistance, bright color, etc., and has good application prospects.
[0003] However, from the current application situation, there are still many problems with color steel fire door panels: 1) Color steel plates for fire doors usually use ordinary hot-dip galvanized plate TDC51D+Z as the substrate, and such a substrate does not have good fireproof performance and often cannot meet the requirements of national standard GB 12955-2008 for fire resistance; 2) When processing color steel plates for fire doors, in addition to the strength performance of the panel, higher requirements are also placed on the mechanical properties such as bending at the edges and joints. For ordinary color steel sandwich panels, their adhesion performance drops sharply at high temperatures, resulting in the peeling off of the color coating and the substrate, causing the refractory failure of the internal sandwich layer and unable to achieve the expected fireproof performance; and there is no research on the production process of color coated steel plates without using fireproof coatings; 3) At present, there are relevant studies on the adhesive performance between color steel plates for fire doors and their sandwich panels, but it does not involve the improvement of the adhesion of the color steel plates for fire doors themselves, and the production process difficulties need to be solved urgently.
[0004] The color steel plate for fire doors not only needs to ensure the required strength and excellent processing performance, but also needs to have good adhesion performance to ensure its fireproof property. Summary of the Invention
[0005] The main purpose of the invention is to provide a color steel plate for fire doors and a preparation method thereof in view of the problems and deficiencies existing in the prior art, which can effectively improve the adhesion performance of the fireproof paint coating while meeting the strength and excellent processing performance required for the production of door panels, so as to ensure its fireproof property.
[0006] To achieve the above purpose, the technical solution adopted by the invention is as follows:
[0007] A manufacturing method of a color steel plate for fire doors includes steps of steelmaking - hot rolling - cold rolling - hot dip galvanizing - color coating - coiling. Among them, the color coating includes steps of cleaning, passivation pretreatment, baking after passivation, primary coating, baking, finish coating, baking. The key control steps are as follows:
[0008] 1) In the hot dip galvanizing process, a low-temperature annealing process is adopted, and the strip annealing temperature is 735 - 750 °C;
[0009] 2) Color coating process;
[0010] In the cleaning step, according to the production speed of the unit, the free alkali concentration in the degreasing cleaning process is regulated.
[0011] In the baking step after passivation, the baking temperature after passivation is regulated according to the unit speed and plate thickness.
[0012] In the primer coating and finish coating steps, a 2 / 2 coating structure is adopted. The primer is coated in the primer coating section, and the topcoat is coated in the finish coating section. The film thickness of the primer and topcoat is controlled; the coating viscosity is controlled, and the speeds of the coating roller and the strip roller are regulated according to the production speed of the unit.
[0013] In the baking step, one-stage baking is adopted, and the baking temperatures of the primer and topcoat are regulated according to the unit speed and plate thickness; the outlet plate temperature PMT is controlled at 237 - 246 °C.
[0014] In the above solution, the chemical composition and its mass percentage of the steel used for the door panel obtained by the steelmaking step are as follows: C ≤ 0.05%, Si ≤ 0.03%, Mn 0.1 - 0.3%, Cr 0.015 - 0.035%, Ni 0.01 - 0.03%, Cu 0.03 - 0.08%, P ≤ 0.020%, S ≤ 0.020%, Als 0.015 - 0.060%, N ≤ 0.005%, and the rest are Fe and inevitable impurities.
[0015] In the above solution, the hot rolling heating temperature is controlled within 1250 °C, the finish rolling temperature is controlled at ≥ 870 °C, and the coiling temperature CT is controlled at 600 - 640 °C.
[0016] In the above solution, the cold rolling controls the finished product thickness to be 0.8 - 1.2 mm; the cold rolling reduction rate ≥ 70%.
[0017] In the above solution, the metallographic structure of the steel used for the door panel obtained before hot-dip galvanizing is: ferrite + a small amount of cementite, the grain size is grade 9, the yield strength value of the steel plate is 260 - 320 MPa, the tensile strength value is 350 - 400 MPa, and the elongation after fracture is greater than 32%.
[0018] In the above solution, the weight of the coating obtained by hot-dip galvanizing is 50 - 75 g / m on both sides 2 , and the 180° cold bending test of the zinc coating meets the following requirements: when the bending diameter = 0, no zinc coating peeling is allowed within 5 mm from the edge of the specimen, zinc coating cracks that do not expose the steel base are allowed, but there are no peeling traces.
[0019] Furthermore, in the annealing section of the hot-dip galvanizing process, low-temperature annealing is adopted, with the annealing temperature controlled at 735 - 750 °C; the temperature of the strip entering the zinc pot is controlled at 460 - 480 °C, and the total elongation of the skin pass mill and tension leveling machine is controlled at 0.8 - 1.2%.
[0020] In the above solution, in the cleaning step of the color coating process, the free alkali concentration of the degreasing cleaning process is controlled according to the production speed of the unit, specifically including: when the unit speed is above 70 m / min, the free alkali is controlled at 4 - 5 points (10 ml), and when the unit speed is below 70 m / min, it is controlled at 3 - 4 points (10 ml).
[0021] In the above solution, in the passivation pretreatment step, a chromium-free passivation process is adopted, with the conductivity of 10 - 14 ms / cm and the temperature of 40 - 55 °C.
[0022] In the above solution, in the post-passivation baking step of the color coating process, the post-passivation baking temperature is controlled according to Equation I:
[0023] T = (0.54 * d * v + 163.12) + a (I);
[0024] In the formula, T is the hot air baking temperature, °C; d is the strip thickness (excluding the galvanized layer thickness), mm; v is the unit speed, m / min; a is the error, with a value of -3 to 3 °C, and it is slightly adjusted according to the calculation result and the actual situation of the unit.
[0025] In the above solution, in the primer coating and finish coating steps of the color coating process, a 2 / 2 coating structure is adopted. The primer is coated in the primer coating section, and the topcoat is coated in the finish coating section. Both sides are epoxy resin primer + fireproof polyester topcoat. The film thickness of the primer and topcoat is controlled, and the total film thickness is 19 - 27 um, where the primer thickness is 5 - 9 um and the topcoat is 13 - 17 um.
[0026] In the above solution, in the coating step of the color coating process, after the coating is diluted with a thinner, the coating viscosity is controlled. The primer viscosity is 10 - 11 s (25 °C, Zahn #4 cup), and the topcoat viscosity is 17 - 19 s (25 °C, Zahn #4 cup); and according to the different production speeds of the unit, the speeds of the coating roll and the strip feeding roll are controlled; among them, the roll speed of the coating roll is 1.0 - 1.4 times the unit speed, and the roll speed of the strip feeding roll is 0.6 - 0.8 times the unit speed; the roll pressure of the strip feeding roll is 1700 - 1800 kg, and the roll pressure of the coating roll is 200 - 300 kg, and it is adjusted according to the actual situation of the unit.
[0027] In the above solution, in the coating baking of the color coating process, one-stage baking is adopted, and the baking temperatures of the primer and topcoat are controlled according to Equation II and Equation III respectively, and the PMT (plate temperature) is controlled at 237 - 246 °C:
[0028] T (primer) = (1.63 * d * v + 215) + b (II);
[0029] T (topcoat) = (1.78 * d * v + 209) + b (III);
[0030] Wherein, T is the baking furnace temperature, °C; d is the strip thickness, mm; v is the unit speed, m / min; b is the error, with a value range of -10 to 10, °C, and it is slightly adjusted according to the calculation results and the actual situation of the unit.
[0031] Furthermore, the speed of the color coating unit is selected from 60 to 80 m / min.
[0032] The fireproof door color steel plate prepared according to the above scheme includes the steel for the door panel and the galvanized layer and fireproof coating provided on both sides thereof. The thickness of the steel for the door panel is 0.8 to 1.2 mm, the yield strength value of the steel plate is 260 to 320 MPa, the tensile strength value is 350 to 400 MPa, and the elongation after fracture is greater than 32%; the coating structure is 2 / 2, with epoxy resin back paint + fireproof polyester topcoat on both sides. Both the front and back sides meet the requirements: reverse impact ≥ 9 J, and there are no cracks on the surface when observed under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0033] The principle of the present invention is as follows:
[0034] 1) Chemical composition design:
[0035] C; Carbon is a good solid solution strengthening element; it can improve the strength of the steel plate, make the steel plate easier to maintain its shape during the processing, not easy to deform, and can be shaped by heat treatment and cold working, improving the flexibility of processing. A certain content of C element helps to improve the high-temperature resistance of the steel plate. During a fire, it can keep the door panel steel in a stable structure for a certain period of time and delay the spread of the fire. However, too high a C content will reduce the toughness and welding performance of the steel, having an adverse impact on processing and fire prevention. Therefore, in the present invention, C ≤ 0.05%.
[0036] Si; Silicon is a relatively strong solid solution strengthening element. Adding a certain amount of silicon can significantly improve the strength, hardness and elastic limit of the steel, and also improve the oxidation resistance of the steel at high temperatures. However, a relatively high silicon content in the steel matrix will have an adverse impact on hot-dip galvanizing. As the silicon content in the steel matrix increases, the content of SiO2 generated by the oxidation of silicon also increases, which will affect the effect of the subsequent pickling process. If there is still residual SiO2 on the surface of the steel plate after pickling, the ζ phase of the iron-zinc alloy layer in the coating will thicken violently after galvanizing, forming a gray coating, resulting in poor adhesion of the coating. Therefore, in order to balance the advantages and disadvantages of silicon element, its content must be controlled within a suitable range. In the present invention, the Si content ≤ 0.03%.
[0037] Mn; The addition of Mn can strengthen ferrite and increase the strength of the substrate of the color-coated plate. However, the addition of Mn will lower the phase transformation temperature of the steel, and in case of a fire, it will cause a sharp drop in its strength and hardness, thus affecting the fire resistance of the door panel. Therefore, the content of Mn in the present invention is controlled to be 0.10 - 0.30%.
[0038] Cr; When Cr is added to steel, solid solution strengthening will occur, thereby increasing the yield and tensile strength of the steel. At the same time, Cr can form stable oxides in hot-dip galvanized steel sheets, and these oxides will play a protective role at high temperatures, improving the high-temperature stability of the steel. However, the increase of Cr will increase the production cost. Therefore, the content of Cr in the present invention is controlled to be 0.015 - 0.035%.
[0039] Ni; Ni can increase the strength of the steel without reducing its plasticity, and improve the toughness of the steel at high and low temperatures. Ni itself has certain corrosion resistance and good corrosion resistance to some reducing acids. The content of Ni in the present invention is controlled to be 0.01 - 0.03%.
[0040] Cu; Cu is an element that expands the austenite phase region, can increase the strength and impact toughness of the steel, and can also improve the high-temperature oxidation resistance of the steel. However, when the copper content exceeds 0.5%, the plasticity will be significantly reduced. Therefore, the content of Cu in the present invention is controlled to be 0.03 - 0.08%.
[0041] P; Phosphorus will form hard and brittle phosphide phases in the steel, and the existence of these phases will reduce the toughness and ductility of the steel, thus causing embrittlement of the steel and making the door panel more likely to break when subjected to impact or bending. Therefore, the content of P in the present invention is controlled to be ≤0.020%.
[0042] S; S is a harmful impurity element in steel, and the smaller the content of S, the better the corrosion resistance. The content of S in the present invention is controlled to be ≤0.020%.
[0043] Als; Als mainly plays a role in refining the grains in the steel, thereby increasing the yield strength of the steel. However, with the increase of Als, the number of inclusions in the steel increases, and the size of the inclusions will also become larger, which will lead to poor coating adhesion, corrosion resistance and stamping process performance of the color-coated plate. The content of Als in the present invention is controlled to be 0.015 - 0.06%.
[0044] In addition to containing the above chemical components, the balance is Fe and unavoidable inclusions.
[0045] 2) Process improvement:
[0046] Through the improvement of the steel composition design and by adopting low-temperature annealing in the hot-dip galvanizing annealing process, the microstructure in the steel strip is regulated, recrystallization is promoted and very fine grains are formed, which helps to increase the final strength of the steel strip.
[0047] In the color coating process, in order to ensure good adhesion between the coating and the hot-dip galvanized substrate, a "degreasing cleaning - chromium-free passivation" pretreatment process is adopted to control the free alkalinity in the cleaning section, thereby ensuring the surface smoothness of the substrate to the greatest extent; at the same time, the baking temperature of the chromium-free passivation is controlled to ensure that the coated passivation film layer is continuous, uniform, and dense. The coating structure is 2 / 2, with epoxy resin primer + fireproof polyester topcoat on both sides. According to the characteristic of high viscosity of the fireproof coating, after dilution with a diluent, the coating viscosity is controlled. According to the different production speeds of the unit, the speeds of the coating roller and the strip roller are controlled, and at the same time, according to the unit speed and plate thickness, the open temperatures of the primer and the topcoat are controlled, which can effectively ensure the adhesion performance, impact resistance (no cracks after impact), and corrosion resistance of the obtained coating, etc.
[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0049] (1) The fireproof door color steel plate of the present invention adopts a 2 / 2 structure, with the primer coated in the primary coating section and the topcoat coated in the finishing coating section. Both sides are epoxy resin primer + fireproof polyester topcoat, having excellent processing performance and coating adhesion performance.
[0050] (2) The metallographic structure of the steel plate substrate of the fireproof door color steel plate of the present invention is ferrite + cementite, the yield strength is controlled at 260 - 320 MPa, the tensile strength is 350 - 400 MPa, the elongation rate is greater than 32%, and the change value (AI) of the yield strength between the hot-dip galvanized substrate and the color plate is ≤ 5 Mpa, which can ensure that the color plate has good anti-aging performance.
[0051] (3) The thickness of the fireproof door color steel plate of the present invention is 0.8 - 1.2 mm, and both the front and back sides meet the requirements: reverse impact ≥ 9 J, 90° bending is qualified, and there are no cracks on the surface when observed under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0052] (4) The present invention proposes a relational formula among parameters such as the passivation baking temperature, the coating baking temperature, the plate thickness, and the unit running speed, which provides guidance for production. Through this relational formula, the adhesion performance of the color coating product can be ensured, and efficient and stable production can be achieved. Description of the Drawings
[0053] Figure 1 It is the metallographic structure diagram of the product obtained in an embodiment of the present invention. Detailed Embodiments
[0054] Below, the applicant will further elaborate on the present invention in combination with specific embodiments, so that those skilled in the art can understand the present invention more clearly. However, the following content should not be construed as a limitation on the scope of protection requested by the claims of the present invention.
[0055] In the following embodiments, the production method of the fireproof door color-coated steel plate includes the steps of steelmaking - hot rolling - cold rolling - hot-dip galvanizing - color coating - coiling, and specifically includes the following steps:
[0056] 1) According to the chemical composition shown in Table 1, molten iron is used for steelmaking → continuous casting → hot rolling to produce a hot-rolled steel coil with a thickness of 2.0 - 6.0 mm; among them, the hot-rolling heating temperature is controlled within 1250 °C, the finish rolling temperature is controlled at ≥870 °C, and the coiling temperature CT is controlled at 600 - 640 °C;
[0057] 2) After pickling, cold rolling is carried out, and the target thickness is 0.8 - 1.2 mm; the cold rolling reduction rate is ≥70%;
[0058] 3) The hot-dip galvanizing annealing temperature is 735 - 750 °C, the strip inlet zinc pot temperature is controlled at 460 - 480 °C, the coating weight is 75 / 75 g / m 2 , the skin pass elongation is 0.8 - 1.2%, and the surface roughness is controlled at 1.1 - 1.4 μm.
[0059] 4) Color coating process:
[0060] 4-1) According to the different production speeds of the unit, the free alkali concentration in the degreasing and cleaning process is controlled: when the unit speed is above 70 m / min, the free alkali is controlled at 4.5 ± 0.5 points (10 ml), and when the speed is below 70 m / min, it is controlled at 3.5 ± 0.5 points (10 ml);
[0061] 4-2) Chromium-free passivation pretreatment is adopted for passivation pretreatment, and the main components of the passivation solution used include titanium, phosphate and polymer (Chemetall, X4802 / 2RFU) with a conductivity of 10 - 14 ms / cm and a temperature of 40 - 55 °C;
[0062] According to the different production speeds of the unit, the baking temperature after passivation is controlled according to the following formula:
[0063] T = (0.54 * d * v + 163.12) + a;
[0064] In the formula: T is the hot air baking temperature, unit °C; d is the strip thickness, unit mm; v is the unit speed, unit m / min, a is the error, unit °C, and the value is -3 - 3, and it is slightly adjusted according to the calculation result and the actual situation of the unit;
[0065] 4-3) In the primer coating and finish coating steps, a 2 / 2 coating structure is adopted. The primer is coated in the primer coating section, and the topcoat is coated in the finish coating section. The film thicknesses of the primer and the topcoat are controlled. The primer coating thickness is 7 ± 2 μm, and the finish coating thickness is 15 ± 2 μm. Control the paint viscosity. After the paint is diluted with a thinner, control the paint viscosity. The primer viscosity is 10 - 11 s (25 °C, Zahn #4 cup), and the topcoat viscosity is 17 - 19 s (25 °C, Zahn #4 cup).
[0066] 4-5) According to different production speeds of the unit, control the speeds of the coating roller and the strip feeding roller. The speed of the coating roller is 1.0 - 1.4 times the speed of the unit, and the speed of the strip feeding roller is 0.6 - 0.8 times the speed of the unit. The roll pressure of the strip feeding roller is 1700 - 1800 kg, and the roll pressure of the coating roller is 200 - 300 kg.
[0067] 4-6) According to different production speeds of the unit, control the baking temperature of the primer coating and finish coating, the outlet plate temperature, etc.: The PMT is controlled at 237 - 246 °C.
[0068] T (primer coating) = (1.63 * d * v + 215) + b;
[0069] T (finish coating) = (1.78 * d * v + 209) + b;
[0070] Where: T is the baking furnace temperature, in °C; d is the strip thickness, in mm; v is the unit speed, in m / min, and b is the error, with a value range of -10 to 10, and it is slightly adjusted according to the calculation results and the actual situation of the unit.
[0071] Table 1 Chemical compositions of the steel substrates described in Examples 1 - 5 and Comparative Examples 1 - 2
[0072]
[0073] Example 1
[0074] A color steel plate for fire doors, referring to the above preparation method, the key control conditions are specifically as follows:
[0075] The cold-rolled plate thickness is 0.8 mm, the hot-dip galvanizing annealing temperature is 740 °C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2; The process speed of the color coating line is 80 m / min; the free alkali in the cleaning section is 4.8 points (10 mL), and the passivation baking temperature is controlled at 195°C; the viscosity of the primer coating is 10 seconds (25°C, Zahn #4 cup), the roller speed of the primer (primer) coating roller is 95 m / min, the roller speed of the strip feeding roller is 50 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; the viscosity of the topcoat (topcoat) coating is 18 seconds (25°C, Zahn #4 cup), the roller speed of the topcoat coating roller is 95 m / min, the roller speed of the strip feeding roller is 65 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 200 kg; the primer baking temperature is controlled at 325°C, and the topcoat baking temperature is controlled at 330°C.
[0076] After testing, the yield strength RP of the obtained color-coated steel plate 0.2 is 264 MPa, the tensile strength is 368 MPa, the elongation is 42.8%, the reverse impact work is 12 J, and there are no cracks on the surface observed under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0077] Example 2
[0078] A fireproof door color-coated steel plate, the preparation method of which is substantially the same as that of Example 1, except that the key control conditions are as follows:
[0079] The cold-rolled plate thickness is 0.9 mm, the hot-dip galvanizing annealing temperature is 735°C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2 ; The process speed of the color coating line is 80 m / min; the free alkali in the cleaning section is 4.3 points (10 mL), and the passivation baking temperature is controlled at 200°C; the viscosity of the primer coating is 10 seconds (25°C, Zahn #4 cup), the roller speed of the primer coating roller is 95 m / min, the roller speed of the strip feeding roller is 50 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; the viscosity of the topcoat coating is 18 seconds (25°C, Zahn #4 cup), the roller speed of the topcoat coating roller is 90 m / min, the roller speed of the strip feeding roller is 60 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 200 kg; the primer baking temperature is controlled at 330°C, and the topcoat baking temperature is controlled at 340°C.
[0080] After testing, the yield strength RP of the obtained color-coated steel plate 0.2 is 295 MPa, the tensile strength is 378 MPa, the elongation is 39.6%, the reverse impact work is 11 J, and there are no cracks on the surface observed under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0081] Example 3
[0082] A color-coated steel plate for fire doors, the preparation method of which is substantially the same as that of Example 1, except that the key control conditions are as follows:
[0083] The cold-rolled plate thickness is 0.9 mm, the hot-dip galvanizing annealing temperature is 738 °C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2 ; The process speed of the color coating unit is 60 m / min; The free alkali in the cleaning section is 3.5 points (10 mL), and the passivation baking temperature is controlled at 190 °C; The viscosity of the primer coating is 10 seconds (25 °C, Zahn #4 cup), the roller speed of the primer coating roller is 75 m / min, the roller speed of the strip feeding roller is 50 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; The viscosity of the finish coating is 18 seconds (25 °C, Zahn #4 cup), the roller speed of the finish coating roller is 75 m / min, the roller speed of the strip feeding roller is 65 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 200 kg; The primer baking temperature is controlled at 310 °C, and the finish paint baking temperature is controlled at 315 °C.
[0084] After testing, the yield strength RP of the obtained color-coated steel plate 0.2 is 288 MPa, the tensile strength is 364 MPa, the elongation is 40.8%, the reverse impact work is 10 J, and there are no cracks on the surface observed under a 10-fold magnifying glass after reverse impact; After the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0085] Example 4
[0086] A color-coated steel plate for fire doors, the preparation method of which is substantially the same as that of Example 1, except that the key control conditions are as follows:
[0087] The cold-rolled plate thickness is 1.0 mm, the hot-dip galvanizing annealing temperature is 740 °C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2 ; The process speed of the color coating unit is 60 m / min; The free alkali in the cleaning section is 3.3 points (10 mL), and the passivation baking temperature is controlled at 195 °C; The viscosity of the primer coating is 10.5 seconds (25 °C, Zahn #4 cup), the roller speed of the primer coating roller is 70 m / min, the roller speed of the strip feeding roller is 50 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; The viscosity of the finish coating is 18 seconds (25 °C, Zahn #4 cup), the roller speed of the finish coating roller is 70 m / min, the roller speed of the strip feeding roller is 60 m / min, the pressure of the strip feeding roller is 1700 kg, and the pressure of the coating roller is 250 kg; The primer baking temperature is controlled at 320 °C, and the finish paint baking temperature is controlled at 325 °C.
[0088] After testing, the yield strength RP of the obtained color-coated steel plate 0.2The yield strength is 306 MPa, the tensile strength is 380 MPa, the elongation is 37.2%, the reverse impact work is 10 J, and there are no cracks on the surface observed under a 10x magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0089] Example 5
[0090] A color steel plate for fire doors, referring to the above preparation method, the key control conditions are specifically as follows:
[0091] The cold-rolled plate thickness is 1.2 mm, the hot-dip galvanizing annealing temperature is 745 °C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2 ; the process speed of the color coating unit is 60 m / min; the free alkali in the cleaning section is 3.6 points (10 mL), and the passivation baking temperature is adjusted to 202 °C; the viscosity of the primer coating is 10 seconds (25 °C, Zahn #4 cup), the roller speed of the primer coating roller is 92 m / min, the roller speed of the strip feeding roller is 50 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; the viscosity of the finish coating is 20 seconds (25 °C, Zahn #4 cup), the roller speed of the finish coating roller is 70 m / min, the roller speed of the strip feeding roller is 65 m / min, the pressure of the strip feeding roller is 1700 kg, and the pressure of the coating roller is 300 kg; the primer baking temperature is adjusted to 335 °C, and the finish paint baking temperature is adjusted to 340 °C.
[0092] After testing, the yield strength RP of the obtained color steel plate 0.2 is 272 MPa, the tensile strength is 370 MPa, the elongation is 41.5%, the reverse impact work is 11 J, and there are no cracks on the surface observed under a 10x magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and the surface is intact without defects such as rust and bubbles.
[0093] Comparative Example 1
[0094] A color steel plate for fire doors, the preparation method of which is substantially the same as that of Example 1, except that
[0095] The cold-rolled plate thickness is 0.9 mm, the hot-dip galvanizing annealing temperature is 755 °C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2; The process speed of the color coating line is 60 m / min; the free alkali in the cleaning section is 4.5 points (10 mL), and the passivation baking temperature is 180 °C; the viscosity of the primer coating is 10 seconds (25 °C, Zahn #4 cup), the roller speed of the primer coating roller is 85 m / min, the roller speed of the strip feeding roller is 50 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; the viscosity of the topcoat is 18 seconds (25 °C, Zahn #4 cup), the roller speed of the topcoat coating roller is 85 m / min, the roller speed of the strip feeding roller is 65 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 200 kg; the baking temperature of the primer is 290 °C, and the baking temperature of the topcoat is 315 °C.
[0096] After testing, the yield strength RP of the obtained color-coated steel plate 0.2 is 218 MPa, the tensile strength is 306 MPa, the elongation is 42%, the reverse impact work is 6 J, and obvious cracks are observed on the surface under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and rust defects occur on the surface.
[0097] Comparative Example 2
[0098] A color-coated steel plate for fire doors, referring to the above preparation method, the key control conditions are as follows:
[0099] The cold-rolled plate thickness is 1.0 mm, the hot-dip galvanizing annealing temperature is 710 °C, and the hot-dip galvanizing coating weight is 75 / 75 g / m 2 ; The process speed of the color coating line is 60 m / min; the free alkali in the cleaning section is 3.8 points (10 mL), and the passivation baking temperature is 190 °C; the viscosity of the primer coating is 10.5 seconds (25 °C, Zahn #4 cup), the roller speed of the primer coating roller is 60 m / min, the roller speed of the strip feeding roller is 40 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; the viscosity of the topcoat is 18 seconds (25 °C, Zahn #4 cup), the roller speed of the topcoat coating roller is 60 m / min, the roller speed of the strip feeding roller is 40 m / min, the pressure of the strip feeding roller is 1700 kg, and the pressure of the coating roller is 250 kg; the baking temperature of the primer is 330 °C, and the baking temperature of the topcoat is 345 °C.
[0100] After testing, the yield strength RP of the obtained color-coated steel plate 0.2 is 338 MPa, the tensile strength is 420 MPa, the elongation is 37.9%, the reverse impact work is 6 J, and obvious cracks are observed on the surface under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and rust defects occur on the surface.
[0101] Comparative Example 3
[0102] A color-coated steel plate for fire doors, referring to the above preparation method, the key control conditions are as follows:
[0103] The cold-rolled sheet thickness is 0.9 mm, the hot-dip galvanizing annealing temperature is 742 °C, and the hot-dip galvanized coating weight is 75 / 75 g / m 2 ; the process speed of the color coating line is 80 m / min; the free alkali in the cleaning section is 4.8 points (10 mL), and the passivation baking temperature is 210 °C; the viscosity of the primer coating is 10.5 seconds (25 °C, Zahn #4 cup), the roller speed of the primer coating roller is 60 m / min, the roller speed of the strip feeding roller is 40 m / min, the pressure of the strip feeding roller is 1800 kg, and the pressure of the coating roller is 150 kg; the viscosity of the topcoat is 18 seconds (25 °C, Zahn #4 cup), the roller speed of the topcoat coating roller is 60 m / min, the roller speed of the strip feeding roller is 40 m / min, the pressure of the strip feeding roller is 1700 kg, and the pressure of the coating roller is 250 kg; the primer baking temperature is 345 °C, and the topcoat baking temperature is 349 °C.
[0104] After testing, the yield strength RP0.2 of the obtained color-coated steel plate is 266 MPa, the tensile strength is 328 MPa, the elongation is 40.9%, the reverse impact work is 3 J, and obvious cracks are observed on the surface under a 10-fold magnifying glass after reverse impact; after the reverse impact test, the specimen is placed in a salt spray test chamber for 72 h, and obvious rust defects occur on the surface.
[0105] The present invention is not limited to the above embodiments. For those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also considered within the protection scope of the present invention. The content not described in detail in this specification belongs to the prior art well known to those of ordinary skill in the art.
Claims
1. A process for preparing a color steel plate for a fire door, characterized in that: It includes steelmaking, hot rolling, cold rolling, hot-dip galvanizing, color coating, and coiling processes. Color coating includes cleaning, passivation pretreatment, post-passivation baking, initial coating, baking, fine coating, and baking steps. The key control steps are as follows: 1) Low temperature annealing process is adopted in the hot-dip galvanizing process, and the strip annealing temperature is 735-750℃; 2) Color coating process; In the cleaning step, the free alkali concentration of the degreasing and cleaning process is regulated according to the production speed of the unit; In the post-passivation baking step, the post-passivation baking temperature is regulated according to the unit speed and the plate thickness; In the initial coating and fine coating steps, a 2 / 2 coating structure is used, with primer applied in the initial coating section and topcoat applied in the fine coating section, and the film thickness of the primer and topcoat is controlled; the viscosity of the coating is controlled, and the speed of the coating roller and the belt roller is adjusted according to the production speed of the unit; In the baking step, the baking temperature of the primer and topcoat is regulated according to the unit speed and the plate thickness; The outlet plate temperature is controlled at 237-246℃.
2. The preparation process according to claim 1, characterized in that: The steelmaking step controls the chemical composition of the door panel steel obtained and the mass percentages thereof are as follows: C≤0.05%, Si≤0.03%, Mn 0.1-0.3%, Cr 0.015-0.035%, Ni 0.01-0.03%, Cu 0.03-0.08%, P≤0.020%, S≤0.020%, Als 0.015-0.060%, N≤0.005%, and the rest are Fe and unavoidable impurities.
3. The preparation process according to claim 1, characterized in that: The cold rolling controls the finished product thickness to be 0.8-1.2 mm; the cold rolling reduction ratio is ≥70%.
4. The preparation process according to claim 1, characterized in that: The annealing section of the hot-dip galvanizing process adopts low-temperature annealing, and the annealing temperature is controlled at 735-750° C.; the temperature of the strip entering the zinc pot is controlled at 460-480° C., and the skin-clearing elongation is controlled at 0.8-1.2%.
5. The preparation process according to claim 1, characterized in that: In the cleaning step of the color coating process, the free alkali concentration of the degreasing and cleaning process is controlled according to the unit production speed, specifically: when the unit speed is above 70m / min, the free alkali is controlled at 4-5 points, and when the unit speed is lower than 70m / min, it is controlled at 3-4 points.
6. The preparation process according to claim 1, characterized in that: In the cleaning step of the color coating process, in the post-passivation baking step of the color coating process, the post-passivation baking temperature is controlled according to Formula I: T = (0.54*d*v+163.12)+a(I); Wherein, T is the hot air baking temperature, ℃; d is the strip thickness, mm; v is the unit speed, m / min; a is the error, which ranges from -3 to 3℃.
7. The preparation process according to claim 1, characterized in that: In the initial coating and fine coating steps adopted in the color coating process, primer is applied in the initial coating section and topcoat is applied in the fine coating section. Both sides are coated with epoxy resin primer + fire-retardant polyester topcoat. The film thickness of the primer and topcoat is controlled. The total film thickness is 19-27um, of which the primer thickness is 5-9um and the topcoat thickness is 13-17um.
8. The preparation process according to claim 1, characterized in that: In the coating step of the color coating process, after the paint is diluted by a diluent, the viscosity of the paint is controlled, 10 to 11 seconds for the primer and 17 to 19 seconds for the topcoat; and the speeds of the coating roller and the strip roller are controlled according to the different production speeds of the unit; wherein the roller speed of the coating roller is 1.0 to 1.4 times the unit speed, and the roller speed of the strip roller is 0.6 to 0.8 times the unit speed; the roller pressure of the strip roller is 1700 to 1800 kg, and the roller pressure of the coating roller is 200 to 300 kg.
9. The preparation process according to claim 1, characterized in that: In the coating baking process, one-stage baking is adopted, and the baking temperatures of the primer and topcoat are controlled according to Formula II and Formula III respectively, and the PMT is controlled at 237-246°C: T(primer) = (1.63*d*v+215)+b(II); T(topcoat) = (1.78*d*v+209)+b(III); Wherein, T is the baking furnace temperature, ℃; d is the strip thickness, mm; v is the unit speed, m / min; b is the error, ranging from -10 to 10, ℃, and is slightly adjusted based on the calculation results and the actual situation of the unit.
10. The color-coated steel plate for fire-proof doors prepared by the preparation process according to any one of claims 1 to 9.