Hot-rolled enameling steel with enameling strengthening property and manufacturing method thereof

Abstract

The invention discloses a hot-rolled steel for enameling with enameling strengthening property, which contains, in addition to Fe and inevitable impurities, the following chemical elements in the following mass percentages: C: 0.03-0.07%, Si≤0.05%, Mn: 1.5-2.5%, Al: 0.01-0.05%, Cr: 0.25-0.65%, Cu: 0.02-0.20%, Ti: 0.01-0.08%, V: 0.01-0.10%, and Mo: 0.01-0.10%. Correspondingly, the present invention also discloses a method for manufacturing the hot-rolled steel for enameling, which comprises the following steps: (1) smelting and casting; (2) heating; (3) hot rolling: controlling the rough rolling temperature to be greater than 850°C, the finishing rolling start temperature to be 900-1050°C, and the finishing rolling final temperature to be 840-900°C; (4) laminar cooling: controlling the cooling rate to be 10-35°C / s; (5) coiling. The hot-rolled steel for enameling of the present invention has lower strength and good formability in the hot-rolled state. After high-temperature enameling, its yield strength will not decrease but will increase, which can effectively improve the strength of the final enameled product.

Description

Technical Field

[0001] The present invention relates to a steel material and a manufacturing method thereof, and in particular to a hot-rolled steel plate for enamel and a manufacturing method thereof. Background Art

[0002] Hot-rolled enameled steel is a composite material made by applying enamel to the surface of pre-treated hot-rolled steel plates and sintering them at high temperatures. It combines the strength and toughness of hot-rolled steel plates with the corrosion resistance and easy cleaning properties of enamel.

[0003] Of course, not all steel plates are suitable for enameling purposes. The steel plate as the base material directly affects the quality of enameled steel products. Fish scale explosion is one of the most common and most terrible defects of enameled steel products.

[0004] The more mature theory currently holds that scale-friction defects are mainly caused by hydrogen, which mainly enters the steel plate during pickling (metal dissolves in acid to produce hydrogen) and enameling (water of crystallization contained in glaze grinding additives or water vapor in the furnace atmosphere reacts with metal to generate hydrogen); as the temperature drops, the solubility of hydrogen in steel decreases and reaches an oversaturated state, causing hydrogen to accumulate between the steel plate and the enamel layer in the form of gas, thereby forming a certain pressure. When the pressure increases to a certain critical value, it causes scale-friction defects.

[0005] Therefore, in addition to improving the enameling process, it is also necessary to improve the hydrogen storage performance of the steel plate itself; when the hydrogen storage capacity of the steel plate is strong, the diffusion of hydrogen in the steel plate is slow, and less hydrogen enters the steel plate under the same enameling process, and the steel plate has a strong ability to accommodate hydrogen after the enameling is completed, which will help prevent scale explosion of enameled products. The grain boundaries, dislocations, cavities, inclusions and precipitation phases in the steel are all good hydrogen storage traps. Therefore, for enameled steel, it is necessary to adjust the composition and production process of the steel according to different enameling uses to ensure that there are enough hydrogen storage traps in the steel to achieve good anti-scale explosion performance.

[0006] In addition, because the enamel sintering process usually needs to be completed at a high temperature of more than 820℃ for a period of time, the final strength of the enameled product depends on the strength of the enameled steel after high-temperature enameling. Under normal circumstances, the strength of the steel plate will decrease significantly after such high-temperature heat treatment. This is because the microstructure of the steel plate will experience a decrease in dislocation density, growth of ferrite grains, and coarsening of nano-precipitation phases during the high-temperature heat treatment process. These changes lead to the weakening of dislocation strengthening, fine grain strengthening, and precipitation strengthening. How to improve the strength of steel plates after high-temperature enameling has always been a key research topic in the field of enameled steel development, and it also has important practical application value.

[0007] In the prior art, the existing patented technologies for hot-rolled enameled steel mostly adopt the design of adding Ti element in composition, through which Ti element forms precipitation phases such as TiC and Ti(C, N) with C and N, and plays the role of hydrogen storage trap and precipitation strengthening.

[0008] For example, a Chinese patent document with publication number CN101812630A, publication date August 25, 2010, and titled “Hot-rolled high-strength enameled steel sheet for deep drawing and method for manufacturing the same”, publicly introduces a hot-rolled high-strength enameled steel sheet for deep drawing and a method for manufacturing the same, which uses the following components: C: 0.02-0.10%, Si≤0.10%, Mn: 0.05-1.00%, P≤0.05%, S: 0.005-0.035%, Al: 0.01-0.10%, N≤0.015%, Ti<0.10%, and the remainder is iron and unavoidable impurities.

[0009] For another example, a Chinese patent document with publication number CN103540845A, publication date January 29, 2014, and titled “Hot-rolled thin-plate enameled steel with yield strength of 330 MPa and manufacturing method”, also publicly introduces a hot-rolled thin-plate enameled steel, which has the following composition: C: 0.02-0.07%, Si≤0.05%, Mn: 0.10-0.50%, P≤0.020%, S≤0.010%, Ti: 0.04-0.10%, Al: 0.02-0.08%, N≤0.008%, and the rest is Fe and unavoidable inclusions, and Ti / C=1.0-1.5.

[0010] Another example is the Chinese patent document with publication number CN102181805A, publication date September 14, 2011, and titled “A thin slab continuous casting and rolling line for producing steel plates for water heater liner enamel and method”, which publicly introduces a thin slab continuous casting and rolling line for producing steel plates for water heater liner enamel and method, the components of which are carbon 0.03-0.10, manganese 0.15-0.40, silicon ≤0.06, sulfur 0.004-0.040, phosphorus ≤0.15, aluminum 0.03-0.05, nitrogen 0.002-0.008, titanium 0.02-0.10, and the rest are iron and unavoidable impurities.

[0011] However, it should be noted that the above-mentioned technical solutions all have a common disadvantage that the yield strength of the enameled steel obtained by them after high-temperature enameling is lower than the yield strength of the hot-rolled state.

[0012] Based on this, in view of the defects in the above-mentioned prior art, the present invention hopes to obtain a new hot-rolled enameled steel with enameling strengthening properties. The hot-rolled enameled steel has low strength and good forming properties in the hot-rolled state. After high-temperature enameling, its yield strength will not decrease but will increase, which can effectively improve the strength of the final enameled product. Summary of the invention

[0013] One of the purposes of the present invention is to provide a hot-rolled enameled steel with enameling strengthening properties. The hot-rolled enameled steel has low strength and good forming properties in the hot-rolled state. After high-temperature enameling, its yield strength can be increased instead of decreased through the mechanism of phase transformation strengthening, thereby improving the strength of the final enameled product and extending the service life of the enameled product.

[0014] The hot-rolled enameling steel can be used to prepare large-volume water heater inner tanks, water heater accessories, barbecue stoves and other products with high enameling temperatures and high yield strength performance requirements after enameling, and has very significant application value.

[0015] In order to achieve the above object, the present invention provides a hot-rolled enameling steel with enameling strengthening properties, which contains the following chemical elements in the following mass percentages in addition to Fe and inevitable impurities:

[0016] C: 0.03~0.07%, Si≤0.05%, Mn: 1.5~2.5%, Al: 0.01~0.05%, Cr: 0.25~0.65%, Cu: 0.02~0.20%, Ti: 0.01~0.08%, V: 0.01~0.10%, Mo: 0.01~0.10%.

[0017] Furthermore, in the hot-rolled enameled steel of the present invention, the mass percentage of each chemical element is:

[0018] C: 0.03~0.07%, Si≤0.05%, Mn: 1.5~2.5%, Al: 0.01~0.05%, Cr: 0.25~0.65%, Cu: 0.02~0.20%, Ti: 0.01~0.08%, V: 0.01~0.10%, Mo: 0.01~0.10%, the balance is Fe and other inevitable impurities.

[0019] In the hot-rolled enameled steel of the present invention, the design principles of each chemical element are as follows:

[0020] C: In the hot-rolled enameled steel of the present invention, the C element is an important strengthening element in the steel. It can be dissolved in ferrite or form pearlite structure under certain conditions, thereby strengthening the matrix structure and improving the yield strength of the steel plate. At the same time, the C element can also be combined with strong carbide-forming elements such as Ti and V to form a certain size and number of precipitation phases. These precipitation phases can improve the hydrogen storage performance of the steel plate, thereby playing the role of anti-scale explosion of the enamel. However, the C element in the steel should not be too high. When the C element content in the steel is too high, the proportion of solid-solubilized carbon or pearlite structure in the steel is too high, a large amount of CO and other gases will be generated during the enamel firing, resulting in poor bubble structure of the enamel layer, and then producing defects such as pinholes and bubbles, affecting the surface quality of the enamel. Therefore, in the hot-rolled enameled steel of the present invention, the mass percentage of the C element is limited to between 0.03 and 0.07%.

[0021] Si: In the hot-rolled enameled steel of the present invention, Si element exists in the steel as a residual element. When the Si element content in the steel is too high, the plasticity of the steel will deteriorate. In addition, especially when the one-enameling-one-firing enameling process is adopted, a high Si element content will also affect the adhesion between the steel plate and the enamel. Therefore, considering the adverse effect of Si element on the performance of steel, in the hot-rolled enameled steel of the present invention, the mass percentage of Si element is controlled to meet: Si≤0.05%.

[0022] Mn, Cr: In the hot-rolled enameled steel of the present invention, Mn and Cr are important elements to ensure that the steel obtains high strength after high-temperature enameling. The combination of these two elements can make the steel plate undergo bainite transformation at a lower cooling rate, thereby improving the strength of the matrix structure. Therefore, in the hot-rolled enameled steel of the present invention, the mass percentage of Mn element is limited to between 1.5 and 2.5%, and the mass percentage of Cr element is limited to between 0.25 and 0.65%.

[0023] Mo: In the hot-rolled enameled steel of the present invention, the Mo element can be dissolved in ferrite, austenite and carbide, playing a role of solid solution strengthening, and at the same time can improve the stability of carbides, reduce the coarsening phenomenon of carbide precipitation phase caused by high-temperature enameling, thereby improving the high-temperature stability of steel. In addition, adding an appropriate amount of Mo element to the steel also promotes the phase change of the steel plate under air cooling conditions after high-temperature enameling. Therefore, in the hot-rolled enameled steel of the present invention, the mass percentage of Mo element is limited to between 0.01 and 0.10%.

[0024] It should be noted that, in the hot-rolled enameling steel described in the present invention, the addition of the above-mentioned Mn, Mo and Cr elements can significantly improve the stability of supercooled austenite. When the steel plate is enameled at high temperature and air-cooled to room temperature, the combination of these three elements can make the steel plate undergo bainite phase transformation at a lower cooling rate, thereby obtaining high strength performance.

[0025] Al: In the hot-rolled enameled steel of the present invention, Al is a strong deoxidizing element, and Al is often required for deoxidation in medium and low carbon steels to ensure that the O content in the steel remains at a low value. Therefore, in the hot-rolled enameled steel of the present invention, the mass percentage of Al is limited to between 0.01 and 0.05%.

[0026] Cu: In the hot-rolled enameled steel of the present invention, adding a proper amount of Cu element to the steel is beneficial to surface deposition, improving the adhesion between the steel and the enamel, and further improving the anti-scale explosion performance of the steel. Therefore, in the hot-rolled enameled steel of the present invention, the mass percentage of Cu element is limited to between 0.02 and 0.20%.

[0027] Ti, V: In the hot-rolled enameled steel of the present invention, the composite addition of Ti and V elements is the main element that enables the steel to obtain good hydrogen storage performance. Under the appropriate controlled cooling process, they can form fine and dispersed TiC and VC precipitation phases. These precipitation phases can effectively improve the hydrogen storage performance of the steel plate as irreversible hydrogen storage traps, thereby playing the role of enamel anti-scale explosion. Therefore, considering the mechanical properties and cost factors of the steel comprehensively, in the hot-rolled enameled steel of the present invention, the mass percentage of the Ti element is limited to between 0.01 and 0.08%, and the mass percentage of the V element is limited to between 0.01 and 0.10%.

[0028] Furthermore, the hot-rolled enameled steel of the present invention further contains B: 0.0006-0.003%.

[0029] In the above technical solution of the present invention, in order to obtain a better implementation effect, it is also possible to preferably add an appropriate amount of B element to the hot-rolled enameled steel.

[0030] B: In the hot-rolled enameled steel of the present invention, the solubility of B in the steel is very low. It can mainly combine with the residual nitrogen in the steel and precipitate in the form of BN, which can serve as a hydrogen storage trap and play a role in the anti-scale explosion of the enamel. Therefore, in order to exert the beneficial effect of the B element, in the hot-rolled enameled steel of the present invention, the mass percentage of the B element is controlled between 0.0006 and 0.003%.

[0031] Furthermore, in the hot-rolled enameled steel described in the present invention, each chemical element also satisfies: (C-Ti / 4-V / 4.25)×(Mn+Cr)>0.05; wherein C, Ti, V, Cr and Mn respectively represent the numerical values ​​of the mass percentages of the corresponding elements.

[0032] The hot-rolled enameled steel of the present invention can control the mass percentage of a single chemical element while preferably controlling the elements C, Ti, V, Cr and Mn to satisfy the formula: (C-Ti / 4-V / 4.25)×(Mn+Cr)>0.05.

[0033] The inventors have found through experimental research that when the contents of C, Ti, V, Cr and Mn elements in the steel are controlled to satisfy the above relationship, the steel plate can obtain enameling strengthening properties, that is, the strength of the steel plate after high-temperature enameling will not decrease but increase.

[0034] This is because, when these elements in the steel satisfy this relationship, the remaining C element and the Mn and Cr elements in the steel can work together after the precipitation phases of Ti and V are formed, so that after the steel plate is sintered at high temperature and air-cooled, the microstructure is transformed from pearlite to bainite or martensite. Through this phase transformation strengthening effect, the steel plate obtains higher strength performance than the hot-rolled state, which is one of the key innovations in the composition design of the present invention.

[0035] Furthermore, in the hot-rolled enameled steel of the present invention, its microstructure is ferrite+pearlite.

[0036] Furthermore, in the hot-rolled enameled steel of the present invention, the grain size of ferrite is 8 to 10 levels.

[0037] Furthermore, in the hot-rolled enameled steel of the present invention, the thickness thereof is 1.5 to 3.5 mm.

[0038] Furthermore, in the hot-rolled enameled steel of the present invention, the yield strength in the hot-rolled state is 345-389 MPa, and after high-temperature enameling in the temperature range of 870-950° C., the yield strength is 402-439 MPa.

[0039] Correspondingly, another object of the present invention is to provide a method for manufacturing the above-mentioned hot-rolled enameled steel, which has a simple production process. The hot-rolled enameled steel prepared by the manufacturing method has lower strength and good formability in the hot-rolled state. After high-temperature enameling, its yield strength can be increased instead of decreased through the mechanism of phase transformation strengthening.

[0040] In order to achieve the above object, the present invention provides a method for manufacturing the hot-rolled enameled steel, which comprises the steps of:

[0041] (1) Smelting and casting;

[0042] (2) Heating;

[0043] (3) Hot rolling: control the rough rolling temperature to be greater than 850°C, the finishing rolling start temperature to be 900-1050°C, and the finishing rolling final temperature to be 840-900°C;

[0044] (4) Laminar cooling: control the cooling rate to 10-35°C / s;

[0045] (5) Coiling.

[0046] In the above technical solution of the present invention, in order to obtain a suitable hot-rolled structure so that the hot-rolled steel has lower strength and higher formability, the present invention strictly controls the hot rolling process parameters of step (3) and the laminar cooling parameters of step (4), and the performance of the hot-rolled enameled steel of the present invention can be ensured by controlling rolling and cooling.

[0047] In the hot rolling process of the above step (3), the present invention firstly rough-rolls the heated ingot into an intermediate billet, and then fine-rolls the intermediate billet, and finally fine-rolls the desired slab. The rough rolling temperature is controlled to be greater than 850°C, the fine rolling start temperature is controlled to be 900-1050°C, and the fine rolling final temperature is controlled to be 840-900°C.

[0048] Accordingly, in step (4) of the present invention, the steel plate is water-cooled to the coiling temperature at a cooling rate of 10 to 35°C / s, and then air-cooled to room temperature. The present invention adopts such a controlled rolling and controlled cooling process, which is conducive to obtaining fine ferrite and pearlite grain structures, so that the steel plate has good processing and forming properties.

[0049] The hot-rolled enameled steel produced by the above-mentioned manufacturing method can be further used for single-sided enameling or double-sided enameling to produce enameled products.

[0050] It should be noted that in the above step (1) of the present invention, the casting can be carried out by continuous casting or die casting, which can ensure that the internal composition of the ingot is uniform and the surface quality is good. In some other embodiments, the die casting method can also be adopted, and the die-cast ingot needs to be rolled into a billet by a primary rolling mill.

[0051] Furthermore, in the manufacturing method of the present invention, in step (2), the heating temperature is 1150-1260°C.

[0052] Furthermore, in the manufacturing method of the present invention, in step (5), the coiling temperature is controlled to be 550-680°C.

[0053] In the above technical scheme, the coiling temperature can be preferably controlled to be 550-680°C. When coiling in this temperature range, it is not only beneficial to refine the ferrite grains, but also beneficial to the homogenization of TiC and VC precipitation phases in the steel, so as to obtain hot-rolled enameled steel with excellent mechanical properties and anti-scale explosion properties.

[0054] Compared with the prior art, the method for manufacturing hot-rolled enameled steel of the present invention has the following advantages and beneficial effects:

[0055] The present invention not only reasonably designs the chemical composition, but also optimizes the controlled rolling and controlled cooling process of rapid cooling after rolling, thereby effectively preparing hot-rolled enameled steel with excellent performance in the hot-rolled state. The production process is simple, and the prepared hot-rolled enameled steel has low strength and good forming performance in the hot-rolled state. After high-temperature enameling, the hot-rolled enameled steel can increase its yield strength instead of decreasing through the mechanism of phase change strengthening, which can not only improve the strength of enameled products, but also extend the service life of enameled products.

[0056] The yield strength of the hot-rolled enameled steel in the hot-rolled state is 345-389 MPa. After high-temperature enameling in the temperature range of 870-950°C, its yield strength can be increased to 402-439 MPa. It can be used to prepare large-volume water heater inner tanks, water heater accessories, barbecue stoves and other products with high enameling temperatures and high yield strength performance requirements after enameling, and has very significant application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The effect of different enameling temperatures on the yield strength performance of the steels of Example 1 of the present invention and Comparative Example 1 after enameling is shown.

[0058] Figure 2 This is a metallographic structure photograph of the hot-rolled enameled steel in Example 1 in the hot-rolled state.

[0059] Figure 3 This is a metallographic structure photograph of the hot-rolled enameling steel of Example 1 after being enameled at 870°C and kept at this temperature for 10 minutes and then air-cooled. DETAILED DESCRIPTION

[0060] The hot-rolled enameled steel and the method for manufacturing the same according to the present invention will be further explained and illustrated below in conjunction with the accompanying drawings and specific embodiments of the specification. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0061] Examples 1-7 and Comparative Examples 1-2

[0062] The hot-rolled enameled steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2 were prepared by the following steps:

[0063] (1) Smelting and casting are carried out according to the chemical composition shown in Table 1 below: the smelted molten steel is subjected to vacuum degassing treatment and then continuously cast to obtain a continuously cast ingot.

[0064] (2) Heating: The obtained continuous casting billet is heated, and the heating temperature is controlled to be 1150-1260°C.

[0065] (3) Hot rolling: the rough rolling temperature is controlled to be greater than 850°C, the start rolling temperature of the finishing rolling is controlled to be 900-1050°C, and the final rolling temperature of the finishing rolling is controlled to be 840-900°C.

[0066] (4) Laminar cooling: laminar water cooling is performed, and the cooling rate is controlled at 10 to 35°C / s.

[0067] (5) Coiling: Control the coiling temperature to 550-680°C.

[0068] The hot-rolled enameled steels of Examples 1-7 described in the present invention are all prepared by the above steps, and their chemical compositions and related process parameters meet the control requirements of the design specifications of the present invention.

[0069] It should be noted that, unlike the hot-rolled enameled steel of the above-mentioned embodiments 1-7, although the comparative steel of comparative examples 1-2 also adopts the above-mentioned step (1)-step (5) process, its chemical element composition contains parameters that do not meet the design requirements of the present invention.

[0070] Table 1 lists the mass percentages of various chemical elements in the hot-rolled enameling steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2.

[0071] Table 1. (The balance is Fe and other unavoidable impurities)

[0072]

[0073] Note: M*=(C-Ti / 4-V / 4.25)×(Mn+Cr)>0.05; wherein C, Ti, V, Cr and Mn represent the mass percentage values ​​of the corresponding elements respectively.

[0074] Table 2 lists the specific process parameters of the hot-rolled enameled steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2 during the above manufacturing.

[0075] Table 2.

[0076]

[0077]

[0078] The hot-rolled enameled steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2 in the hot-rolled state were sampled respectively, and the properties of the hot-rolled steels of each Example and Comparative Example were tested. The obtained test results are listed in Table 3. The relevant performance test methods and means are as follows:

[0079] Tensile test: According to GB / T 228.1-2010 "Room Temperature Tensile Test Method for Metallic Materials", the test was carried out using a SCL233 room temperature tensile testing machine, with a tensile speed of 3 mm / min and a JIS5 tensile specimen, to obtain the yield strength, tensile strength and elongation A of the hot-rolled steel corresponding to Examples 1-7 and Comparative Examples 1-2. 50 .

[0080] Table 3.

[0081]

[0082] like Figure 3 As shown, in the present invention, the hot-rolled enameled steels of Examples 1-7 have low yield strength and good formability in the hot-rolled state, the yield strength is between 345-389 MPa, the tensile strength is between 558-625 MPa, and the elongation A is between 1.25-1.80 MPa and 1.35-2.60 MPa, respectively. 50 Between 28-32%.

[0083] The lower yield strength is conducive to the stamping and cold bending of the steel plate during user use. For example, in the process of processing the inner body of the water heater, the springback after cold bending can be avoided, which is conducive to welding. Compared with Examples 1-7, the yield strength of the comparative steel of Comparative Examples 1-2 is higher, which is not conducive to the user's use and processing.

[0084] In order to further demonstrate the performance of the hot-rolled enameled steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2 after enameling, it is necessary to perform enameling treatment on the steel plates of each Example and Comparative Example:

[0085] The steel plates of each embodiment and comparative example were treated with double-sided wet enameling by using Fluke EMP6515 high temperature glaze. The enameling process was controlled as follows: the enameling temperature was controlled to be 870-950°C, and the temperature was kept for 10 minutes, and then air-cooled to obtain the steel plates of embodiments 1-7 and comparative examples 1-2 after enameling.

[0086] It should be noted that, in this embodiment, Examples 1-7 and Comparative Examples 1-2 are all subjected to high-temperature calcination in the temperature range of 870-950° C. and kept warm for 10 minutes. In the present invention, the specific high-temperature calcination temperatures of the embodiments and comparative examples are listed in Table 4 below.

[0087] Table 4.

[0088]

[0089] After the high temperature enameling is completed, the hot-rolled enameled steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2 that have been treated with high temperature enameling are further observed, analyzed and tested for verification:

[0090] The steel plates of Examples 1-7 and Comparative Examples 1-2 were left to stand for 48 hours to observe whether scale explosion occurred on the surface; a drop hammer test was used to verify the adhesion between the steel plate and the enamel; a tensile test was used to determine the yield strength, tensile strength and elongation A of the steel plates of each Example and Comparative Example after enameling 50 ,The results of the experimental test are listed in Table 5.

[0091] Table 5 lists the mechanical properties and enameling properties of the hot-rolled enameled steels of Examples 1-7 and the comparative steels of Comparative Examples 1-2 after enameling.

[0092] Table 5.

[0093]

[0094]

[0095] It can be seen from Table 4 and combined with Tables 1-3 that the thickness of the hot-rolled enameled steel of Examples 1-7 can be in the range of 1.5-3.5 mm. After high-temperature enameling treatment in the temperature range of 870-950°C, the strength of the steel plates of Examples 1-7 does not decrease but increases. The yield strength increases to between 402 and 439 MPa, the tensile strength increases to between 610 and 660 MPa, and the elongation A 50 Between 18-22%.

[0096] After 48 hours, no scale explosion occurred on the enameled steel plates of Examples 1-7 finally obtained; after drop hammer test, the adhesion between the steel plate and the porcelain layer was excellent, which fully met the user's use requirements.

[0097] Accordingly, the performance of the comparative steel plate of Comparative Example 1-2 is significantly inferior to that of the hot-rolled enameled steel of Example 1-7. In Comparative Example 1-2, after high-temperature enameling treatment, the yield strength of the steel of Comparative Example 1-2 decreases significantly. The large decrease in the yield strength of the steel plate before and after enameling will lead to problems such as buckling and deformation of the steel plate, which is not conducive to the processing and use of users. At the same time, after double-sided enameling, Comparative Example 2 has scale-burst defects and cannot meet the anti-scale-burst performance requirements of double-sided enameling.

[0098] Figure 1 The effect of different enameling temperatures on the yield strength performance of the steels of Example 1 of the present invention and Comparative Example 1 after enameling is shown.

[0099] Depend on Figure 1It can be seen that as the enameling temperature increases, the yield strength of the steel in Example 1 shows an upward trend. When the enameling temperature is 930°C, the yield strength can reach 425MPa; while as the enameling temperature increases, the yield strength of the steel in Comparative Example 1 shows a downward trend. When the enameling temperature is 930°C, the yield strength of the steel in Comparative Example 1 is reduced to 289MPa.

[0100] Figure 2 This is a metallographic structure photograph of the hot-rolled enameled steel in Example 1 in the hot-rolled state.

[0101] Figure 3 This is a metallographic structure photograph of the hot-rolled enameling steel of Example 1 after being enameled at 870°C and kept at this temperature for 10 minutes and then air-cooled.

[0102] like Figure 2 and Figure 3 As shown, in the present invention, the microstructure of the hot-rolled enameled steel in Example 1 in the hot-rolled state is ferrite + pearlite, which is transformed into a bainite structure after high-temperature enameling.

[0103] It should be noted that the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0104] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A hot-rolled steel for enameling with enameling strengthening properties, characterized in that: The mass percentage of each chemical element is: C: 0.03-0.07%, Si≤0.05%, Mn: 1.5-2.5%, Al: 0.01-0.05%, Cr: 0.25-0.65%, Cu: 0.02-0.20%, Ti: 0.01-0.08%, V: 0.01-0.10%, Mo: 0.01-0.10%; the balance is Fe and other inevitable impurities; Each chemical element also satisfies: (C-Ti / 4-V / 4.25)×(Mn+Cr)>0.05; wherein C, Ti, V, Cr and Mn represent the numerical values ​​of the mass percentage of the corresponding elements respectively; Its hot-rolled yield strength is 345-389 MPa, and after high-temperature calcination in the temperature range of 870-950°C, the yield strength is 402-439 MPa.

2. The hot-rolled steel for enameling according to claim 1, characterized in that: It also contains B: 0.0006-0.003%.

3. The hot-rolled steel for enameling according to claim 1, characterized in that: Its microstructure is ferrite + pearlite.

4. The hot-rolled steel for enameling according to claim 3, characterized in that: The grain size of ferrite is 8 to 10 levels.

5. The hot-rolled steel for enameling according to claim 1, characterized in that: Its thickness is 1.5-3.5mm.

6. The method for producing hot-rolled steel for enameling according to any one of claims 1 to 5, characterized in that: Includes steps: (1) Smelting and casting; (2) Heating; (3) Hot rolling: control the rough rolling temperature to be greater than 850°C, the finishing rolling start temperature to be 900-1050°C, and the finishing rolling final temperature to be 840-900°C; (4) Laminar cooling: control the cooling rate to 10-35°C / s; (5) Coiling.

7. The manufacturing method according to claim 6, characterized in that: In step (2), the heating temperature is 1150-1260°C.

8. The manufacturing method according to claim 6, characterized in that: In the step (5), the coiling temperature is controlled to be 550-680°C.

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