High-strength enamel steel plate with excellent hydrogen trapping performance and preparation method thereof

Abstract

The application discloses high-strength enamel steel plate with excellent hydrogen capturing performance and a preparation method thereof, and belongs to the technical field of steel metallurgy. The steel plate comprises the following chemical components in percentage by mass: C: 0.01-0.03%, Si: less than or equal to 0.01%, Mn: 1.60-1.80%, P: less than or equal to 0.010%, S: 0.06-0.08%, V: 0.05-0.08%, Ti: 0.08-0.12%, Alt: 0.015-0.055%, N: 0.0080-0.0100%, B: 0.0030-0.0050%, La+Mg: 0.0050-0.0080%, and the rest is Fe and other inevitable impurities. Molten iron and scrap steel are used as raw materials to smelt molten steel; and the molten steel is subjected to continuous casting, heating, hot rolling, laminar cooling, coiling and slow cooling treatment. The enamel steel prepared by the application has excellent anti-fish scale explosion performance before and after enamel firing.

Description

Technical Field

[0001] The present invention belongs to the field of iron and steel metallurgy, and specifically relates to a high-strength enameled steel plate with excellent hydrogen capture performance and a preparation method thereof. This product is widely used in various industries such as construction, chemical industry, metallurgy, and household appliances. Background Art

[0002] With the rapid development of my country's steel industry, enameled steel has received more and more attention. Hot-rolled enameled steel is a type of enameled steel and is widely used in chemical, household, light industry, construction, metallurgy and other industries. By applying a porcelain enamel coating on the surface of the enameled steel, the enameled products have the characteristics of high strength and easy forming. At the same time, they also have the characteristics of corrosion resistance, wear resistance, high temperature resistance and easy cleaning of the porcelain enamel coating.

[0003] Currently, existing enameled steel exhibits poor fish-scaling resistance. The presence of large amounts of freely diffusible hydrogen in steel is the primary cause of fish-scaling in enameled steel. During the high-temperature enameling process, a large amount of hydrogen penetrates the enameled steel. After enameling, this diffusible hydrogen diffuses to the interface between the steel and the enamel layer and accumulates. When the pressure generated by this hydrogen accumulation exceeds the bond strength between the steel and the enamel layer, fish-scaling defects occur, rendering the enameled product scrapped. Therefore, improving the fish-scaling resistance of enameled steel is urgent. Furthermore, enameled steel products suffer from low strength, poor surface quality, and poor weldability, necessitating improvements in their performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-strength enameled steel plate with excellent hydrogen capture performance and a preparation method thereof, which solves the problems of low strength of existing enameled steel products, poor anti-scale sensitivity after enameling, poor surface quality of enameled steel products, and poor welding performance, improves the forming performance of enameled steel products, reduces the thickness of enameled steel products, and produces enameled steel products with good adhesion performance.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A high-strength hot-rolled enameled steel plate with excellent hydrogen capture performance comprises the following chemical components in percentage by mass: C: 0.01-0.03%, Si≤0.01%, Mn: 1.60-1.80%, P≤0.010%, S: 0.06-0.08%, V: 0.05-0.08%, Ti: 0.08-0.12%, Alt: 0.015-0.055%. In addition, the steel further contains N: 0.0080-0.0100%, B: 0.0030-0.0050%, La+Mg: 0.0050-0.0080%, and the remainder is Fe and other inevitable impurities.

[0007] Furthermore, La:Mg=(2.0~3.0):1.

[0008] Further, the carbon equivalent (Pcm) < 0.16%, the calculation formula is as follows:

[0009]

[0010] The role of each chemical element in the present application is mainly based on the following principles:

[0011] C: In enamel steel, it exists in the form of cementite, interstitial solid solution and TiC, and is the most important strengthening element in steel. It is beneficial to improve the strength of enamel steel. Nano-sized TiC is beneficial to the fish scale explosion resistance and adhesion performance. Too high C is not conducive to the surface quality of enamel steel, and too low C is not conducive to the strength of enamel steel. In the present application, C is controlled at 0.01-0.03%.

[0012] Si: In enamel steel, it plays a role of deoxidization, but high Si content has an adverse effect on the surface quality of enamel steel after enameling. In order to ensure the enameling performance and surface quality, Si is controlled at ≤0.01%.

[0013] Mn: It is a commonly used solid solution strengthening element in steel. Appropriate amount of Mn can ensure the enameling performance and avoid the defect of missing coating caused by softening of the steel plate, and can also ensure the forming performance and welding performance of enamel steel. In order to ensure the strength of enamel steel, Mn is controlled at 1.60-1.80%.

[0014] P: P gathered and grew at the grain boundary will reduce the forming performance and toughness of enamel steel, and cause cold brittleness. Therefore, in the present application, P is controlled at ≤0.010%.

[0015] S: It is a harmful element in steel, and the lower the content is, the better. However, in the present application, S generates a large amount of Mn-S-O-B-N-La inclusions, as well as LaS, La2O2S and MgS inclusions in steel. These inclusions act as hydrogen traps to improve the fish scale explosion resistance and adhesion performance of enamel steel. Therefore, the content of S is controlled at 0.06-0.08%.

[0016] Ti: On the one hand, it combines with C to generate TiN, TiC and Ti(C, N), among which TiC and Ti(C, N) are beneficial to the strength of steel; on the other hand, TiC is an irreversible hydrogen trap in steel, which effectively improves the fish scale explosion resistance of enamel steel. In the present application, the content of Ti is controlled at 0.08-0.12%.

[0017] V: It is a micro-alloying element in steel, which plays a role of precipitation strengthening. V combines with C and N to generate VN and VC, which can improve the strength of enamel steel and act as hydrogen traps to improve the fish scale explosion resistance of enamel steel. In the present application, the content of V is controlled at 0.05-0.08%.

[0018] La+Mg: The main function is to modify inclusions and play the role of oxide metallurgy, forming spherical and point-shaped Mn-SOBN-La inclusions as well as LaS, La2O3, La2O2S, MgS and MgO inclusions, which inhibit the brittleness and white spots caused by hydrogen in the steel, reduce the diffusion coefficient of hydrogen, delay the enrichment of hydrogen in the plastic zone at the crack tip, and extend the incubation period and fracture time of crack propagation. The above inclusions act as hydrogen traps, improving the anti-scale and adhesion properties of enameled steel. Therefore, La+Mg is controlled at 0.0050-0.0080%, and La:Mg = (2.0-3.0):1.

[0019] N: A certain amount of N will combine with Ti, V, B, and C to form Ti(C, N), VN, BN, etc., which will play a role in precipitation strengthening and grain refinement in steel, thereby increasing the strength of the enameled steel sheet and also improving the fish scale resistance of the enameled steel. In the present invention, the N content is controlled within a range of 0.0080 to 0.010%.

[0020] B primarily combines with N to form BN particles. BN is highly stable and insoluble at high temperatures, providing a stable anti-fish-scaling effect. Furthermore, B segregates at austenite grain boundaries, inhibiting the precipitation of proeutectoid ferrite and allowing carbides to disperse and precipitate in the low-temperature range. In the present invention, the B content is controlled to be 0.0030-0.0050%.

[0021] Alt: Reacts with N to form AlN, which refines the grains and prevents grain growth during enameling. With specific process coordination, the strength of enameled steel plates can be increased instead of decreased at high temperatures.

[0022] Furthermore, the thickness of the high-strength enameled steel plate is 2.5 to 16.0 mm.

[0023] Furthermore, the yield strength of the high-strength enameled steel plate is ≥900MPa, the tensile strength is ≥950MPa, and the elongation after fracture is A 50 ≥35%, anti-scale sensitivity TH value ≥50min / mm 2 , TH value after two enamelings ≥ 35min / mm 2 , good adhesion performance. .

[0024] Furthermore, the enameling conditions are: temperature of 800-900° C., and time of 2.0-3.0 h.

[0025] The hot-rolled enameled steel provided by the present invention has uniform anti-fish-scale performance before and after enameling.

[0026] Furthermore, the microstructure of the high-strength enameled steel sheet is ferrite and bainite, with a large number of spherical Mn-SOBN-La inclusions, as well as LaS, La2O3, La2O2S and MgS inclusions distributed in the ferrite matrix. There are also a large number of VN, TiC, and BN precipitates with a size of less than 7.5 nm. These inclusions and precipitates can act as stable hydrogen traps, significantly improving the fishscale resistance of the hot-rolled enameled steel.

[0027] The present invention also provides a method for preparing the hot-rolled enameled steel, comprising the following steps:

[0028] (1) using molten iron and scrap steel as raw materials, without pre-treating the molten iron, and then directly smelting to obtain molten steel; wherein the smelting steps include converter smelting, LF ladle furnace refining, and RH vacuum treatment to obtain molten steel; the composition of the molten steel is as described above;

[0029] (2) Continuously casting the molten steel into continuous casting billets, heating, hot rolling, laminar cooling, coiling and slow cooling the continuous casting billets to obtain a new type of high-strength hot-rolled enameled steel coil.

[0030] Furthermore, in step (1), the mass ratio of molten iron to scrap steel is 15-16:2-5.

[0031] Furthermore, in step (1), the converter smelting adopts top and bottom combined blowing converter smelting, and the tapping temperature is ≥1650°C.

[0032] Furthermore, in step (1), the double-station treatment is adopted, including LF ladle furnace refining and RH vacuum treatment, and La+Mg is added after the refining is completed.

[0033] Furthermore, in step (1), aluminum is used for precipitation deoxidation in the early stage of LF ladle furnace refining, and aluminum and calcium carbide are used for diffusion deoxidation during the refining process.

[0034] Furthermore, in step (1), during the RH refining process, vacuum is evacuated and circulated to remove carbon and hydrogen from the steel, alloying the steel. After the RH refining is completed, La and Mg are added, and soft argon blowing is performed for ≥12 minutes to ensure that the chemical composition of the molten steel meets the composition requirements of the hot-rolled enameled steel. The flow rate of the soft argon blowing is 40-70 NL / min, which causes the slag to slightly creep and prevents the molten steel from being exposed.

[0035] Furthermore, in step (2), during the continuous casting process, the continuous casting casting speed is 1.0-1.3 m / min, and the superheat is controlled at 15-25°C.

[0036] Furthermore, in step (2), the thickness of the continuous casting billet is 210 to 250 mm.

[0037] Furthermore, in step (2), the slab heating temperature before hot rolling is controlled at 1250-1280°C for 90-120 minutes; the hot rolling includes rough rolling and finish rolling, the rough rolling start temperature is controlled at 1150-1180°C, and the finish rolling temperature range is 845-875°C.

[0038] Furthermore, in step (2), the thickness of the intermediate billet after rough rolling is 35 to 50 mm.

[0039] Furthermore, in step (2), the temperature of the cooling water for laminar cooling is ≤28°C.

[0040] Furthermore, in step (2), the coiling temperature is 550-580° C., and the thickness of the steel plate is 2.5-16.0 mm.

[0041] Furthermore, in step (2), the slow cooling is: the coiled steel plate enters a slow cooling pit for slow cooling treatment and can be moved after 44 to 56 hours.

[0042] It should be noted that achieving good hydrogen capture performance in enameled steel is not only a matter of composition design but also of production technology. Only through reasonable composition design combined with optimized production technology can the desired microstructure be achieved, effectively improving the fish scale resistance and adhesion properties of enameled steel.

[0043] The production process of enameled steel according to the present invention is described as follows:

[0044] 1. The limitation of tapping temperature during converter smelting and the limitation of soft blowing time after RH refining treatment can ensure the quality of enameled steel N,

[0045] Controlling the contents of O, H and inclusions at expected levels is beneficial to improving the anti-scale and adhesion properties of enameled steel.

[0046] 2. Limiting the casting rate and superheat during continuous casting can ensure that the surface of the continuous casting billet is free of defects.

[0047] 3. Limiting the heating temperature during hot rolling can ensure that all Ti, V and B precipitates in the enameled steel are dissolved, which is beneficial to increasing the TiC, VN and BN contents in the enameled steel.

[0048] 4. By setting reasonable starting rolling temperature, finishing rolling temperature and coiling temperature, the TiC grain size is made ≤7.5nm and exists in the form of interphase precipitation, which is beneficial to improving the anti-fish scale explosion performance of enameled steel.

[0049] 5. The purpose of limiting the laminar cooling water temperature is to ensure the stability of the coiling temperature and obtain the required structure.

[0050] 6. The slow cooling time is limited, which is to make the alloy elements in the steel fully analyze out, so as to ensure the uniformity of the enamel steel plate performance and the anti-scale burst performance.

[0051] The advantages and beneficial effects of the present application are:

[0052] By reasonable component design and optimized process control, a large number of spherical Mn-S-O-B-N-La inclusions, as well as LaS, La2O3, La2O2S and MgS inclusions are distributed in the ferrite matrix, and a large number of VN, TiC and BN precipitates with a size of less than 7.5 nm also exist. The above inclusions and precipitates can act as stable hydrogen traps to capture a large amount of diffusible hydrogen, thereby improving the anti-scale burst performance of the enamel steel. In addition, the Mn-S-O-B-N-La inclusions, as well as LaS, La2O3, La2O2S and MgS inclusions will not significantly grow during the enameling process (enameling temperature is 800-900℃), and their hydrogen trapping capacity will not be significantly reduced, so the enamel steel still has excellent anti-scale burst performance after two times of enameling.

[0053] The enamel steel prepared by the present application has high strength, good surface quality, welding performance, anti-thinning capacity and forming performance, as well as good adhesion performance, and good anti-scale burst sensitivity after enameling.

[0054] In addition, the steel plate prepared by the present application can be used to make pressure vessels (such as electric water heater liner steel, etc.), and for pressure vessels (such as electric water heater liner steel, etc.), the steel plate still has high yield strength after two times of high temperature enameling at 800-900℃, thereby ensuring the fatigue performance and pressure requirements of the enamel liner. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings needed to be used in the specific embodiments or prior art description.

[0056] Figure 1 The microstructure diagram (500x) of the enamel steel plate prepared in Example 1 of the present application;

[0057] Figure 2 The inclusion morphology (D1.0) of the enamel steel plate prepared in Example 1 of the present application;

[0058] Figure 3 The scanning electron microscope photo (1000x) of the enamel steel plate prepared in Example 1 of the present application

[0059] Figure 4 The metallographic structure diagram (500x) of the steel plate prepared in Comparative Example 1. DETAILED DESCRIPTION

[0060] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0061] Example

[0062] A high-strength enameled steel plate with excellent hydrogen capture performance comprises the following chemical compositions by mass percentage: C: 0.01-0.03%, Si≤0.01%, Mn: 1.60-1.80%, P≤0.010%, S: 0.06-0.08%, V: 0.05-0.08%, Ti: 0.08-0.12%, Alt: 0.015-0.055%, and further comprising N: 0.0080-0.0100%, B: 0.0030-0.0050%, La+Mg: 0.0050-0.0080% (La:Mg=(2.0-3.0):1), with the remainder being Fe and other unavoidable impurities; Pcm c <0.16%.

[0063] The method for preparing the high-strength enameled steel plate with excellent hydrogen capture performance comprises the following specific steps:

[0064] (1) Using molten iron and scrap steel as raw materials without molten iron pretreatment; the mass ratio of molten iron to scrap steel is 15-16:2-5;

[0065] (2) Smelting: adopt top and bottom double-blown converter smelting, tapping temperature ≥1650℃;

[0066] (3) Dual-station treatment: First, LF ladle furnace refining is carried out. Aluminum is used for precipitation deoxidation in the early stage of refining. Aluminum and calcium carbide are used for diffusion deoxidation during the refining process. Then RH refining treatment is carried out. Vacuuming and circulation treatment are carried out to remove C and H in the steel. La and Mg are added at the end of refining. Soft blowing of argon is carried out for ≥12 minutes. The flow rate of soft blowing argon is 40-70NL / min.

[0067] (4) Continuous casting: The continuous casting billet speed is 1.0-1.3 m / min, the superheat is controlled at 15-25 °C, and the thickness of the continuous casting billet is 210-250 mm;

[0068] (5) Hot rolling: During hot rolling, the slab heating temperature is controlled at 1250-1280°C, the rough rolling start temperature is controlled at 1150-1180°C, and the finishing rolling temperature range is 845-875°C; the thickness of the intermediate slab is 35-50 mm;

[0069] (6) Laminar cooling: cooling water temperature 22-28°C;

[0070] (7) Coiling: Coiling temperature is 550-580°C, steel plate thickness is 2.5-16.0 mm;

[0071] (8) Slow cooling: After coiling, the steel plate enters the slow cooling pit for slow cooling treatment and can be moved after 44 to 56 hours.

[0072] The chemical compositions of Examples 1 to 6 and Comparative Examples 1 to 2 are shown in Table 1.

[0073] Table 1 Chemical composition of Examples 1 to 6 and Comparative Examples 1 to 2 (mass fraction / %)

[0074] serial number C Si Mn P S V Ti Alt N B La+Mg Example 1 0.01 0 1.62 0.004 0.061 0.052 0.08 0.016 0.0081 0.0032 0.0051 (La:Mg=2.0:1) Example 2 0.012 0 1.64 0.005 0.065 0.054 0.088 0.021 0.0085 0.0036 0.0058 (La:Mg=2.2:1) Example 3 0.015 0 1.68 0.007 0.069 0.058 0.094 0.025 0.0089 0.0039 0.0062 (La:Mg=2.3:1) Example 4 0.021 0 1.72 0.008 0.072 0.062 0.102 0.032 0.0092 0.0042 0.0068 (La:Mg=2.5:1) Example 5 0.025 0.005 1.75 0.009 0.076 0.073 0.114 0.052 0.0096 0.0046 0.0074 (La:Mg=2.7:1) Example 6 0.03 0.01 1.79 0.01 0.08 0.08 0.12 0.055 0.01 0.005 0.0080 (La:Mg=3:1) Comparative Example 1 0.06 0.03 0.8 0.015 0.021 0 0.03 0.025 0.0027 0 0 Comparative Example 2 0.08 0.03 0.9 0.012 0.022 0 0.025 0.03 0.003 0 0

[0075] In Examples 1 to 6 and Comparative Examples 1 to 2, the mass ratio of molten iron to scrap steel was 15:3, the soft blowing of argon was 15 minutes, and the soft blowing of argon flow rate was 50 NL / min; the continuous casting billet drawing speed was 1.1 m / min, the thickness of the continuous casting billet was 230 mm, the thickness of the intermediate billet was 40 mm, and the thickness of the finished enameled steel plate was 4.0 mm.

[0076] The main production process parameters of Examples 1 to 6 and Comparative Examples 1 to 2 are shown in Table 2.

[0077] Table 2 Production process of Examples 1 to 6 and Comparative Examples 1 to 2

[0078]

[0079] According to the chemical composition of Example 1 in Table 1 and the rolling process of Example 1 in Table 2, the metallographic structure and inclusion morphology of the enameled steel plate are as follows: Figure 1 、 Figure 2 As shown in the scanning electron microscope photos Figure 3 As shown, the metallographic structure photo of comparative example 1 is as follows Figure 4 As shown, it can be seen that the metallographic structure of Example 1 is ferrite + bainite (F + B), and the grain size is 13 to 13.5, while the metallographic structure of Comparative Example 1 is ferrite + pearlite (F + P), and the grain size is 12 to 12.5. The anti-scale performance of Examples 1 to 6 is better than that of Comparative Examples 1 to 2.

[0080] Table 3 Mechanical properties and anti-fish scale performance of Examples 1 to 6 and Comparative Examples 1 to 2

[0081]

[0082] Among them, the two enameling conditions after the two enamelings are: the first enameling temperature is 800-850°C, the enameling time is 1-1.5h, and the second enameling temperature is 850-900°C, and the enameling time is 1-1.5h. The specific conditions are shown in Table 4.

[0083] Table 4 Enameling conditions of Examples 1 to 6 and Comparative Examples 1 to 2

[0084]

[0085] As can be seen from Table 3, compared with Comparative Examples 1 to 2, the yield strength of Examples 1 to 6 is ≥900 MPa, the tensile strength is ≥950 MPa, and the elongation after fracture is A 50 ≥35%, and the main parameter to measure the performance of enameled steel, the anti-scale sensitivity TH value ≥50min / mm 2 , TH value after two enamelings ≥ 35min / mm 2 , the adhesion performance is good. It can be seen that the enameled steel prepared by the present invention has excellent anti-fishscale performance before and after enameling, and is particularly suitable for products with high requirements for anti-fishscale performance.

Claims

1. A high-strength enameled steel plate with excellent hydrogen capture performance, characterized in that: Including the following chemical composition by mass percentage: C: 0.01-0.03%, Si≤0.01%, Mn: 1.60-1.80%, P≤0.010%, S: 0.06~0.08%, V: 0.05~0.08%, Ti: 0.08~0.12%, Alt: 0.015~0.055%, N: 0.0080~0.0100%, B: 0.0030~0.0050%, La+Mg: 0.0050~0.0080%, and the rest is Fe and other inevitable impurities; The yield strength of the steel plate is ≥900MPa, the tensile strength is ≥950MPa, and the elongation after fracture is A 50 ≥35%, anti-scale sensitivity TH value ≥50min / mm 2 , TH value after enameling ≥35min / mm 2 The enameling conditions are: temperature of 800~900℃, time of 2.0~3.0h.

2. The high-strength enameled steel plate with excellent hydrogen capture performance according to claim 1, characterized in that: La:Mg=2.0~3.0:

1.

3. The high-strength enameled steel plate with excellent hydrogen capture performance according to claim 1, characterized in that: Carbon equivalent <0.16%.

4. The high-strength enameled steel plate with excellent hydrogen capture performance according to claim 1, characterized in that: The thickness of the steel plate is 2.5-16.0 mm.

5. The method for preparing a high-strength enameled steel plate with excellent hydrogen capture performance according to claim 1, characterized in that: The steps include: (1) Using molten iron and scrap steel as raw materials to smelt molten steel; wherein the smelting steps include converter smelting, LF refining, and RH refining; the tapping temperature of the converter smelting is ≥1650°C; La and Mg are added after the RH refining is completed, and soft argon blowing is ≥12 minutes, and the flow rate of soft argon blowing is 40~70NL / min; (2) Continuously casting molten steel into continuous casting billets, heating, hot rolling, laminar cooling, coiling and slow cooling the continuous casting billets to obtain high-strength enameled steel sheets; wherein the hot rolling includes rough rolling and finish rolling, the rough rolling start temperature is controlled at 1150-1180°C, and the finish rolling temperature range is 845-875°C; the coiling temperature is 550-580°C.

6. The preparation method according to claim 5, characterized in that In step (1), the mass ratio of molten iron to scrap steel is 15-16:2-5; aluminum is used for precipitation deoxidation in the early stage of LF steel refining, and aluminum and calcium carbide are used for diffusion deoxidation during the refining process.

7. The preparation method according to claim 5, characterized in that In step (2), during the continuous casting process, the continuous casting billet drawing speed is 1.0-1.3 m / min, and the superheat is controlled at 15-25°C; the slab heating temperature before hot rolling is controlled at 1250-1280°C, and the time is 90-120 min.

8. The preparation method according to claim 5, characterized in that In step (2), the thickness of the continuous casting billet is 210-250 mm; the thickness of the intermediate billet after rough rolling is 35-50 mm.

9. The preparation method according to claim 5, characterized in that In step (2), the temperature of the cooling water for the laminar cooling is ≤28°C; the slow cooling treatment is as follows: the coiled steel plate enters a slow cooling pit for slow cooling, and the slow cooling treatment time is 44 to 56 hours.

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