High-strength enameled steel plate with excellent hydrogen trapping performance and preparation method of high-strength enameled steel plate

Abstract

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

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and specifically relates to a high-strength enameled steel plate with good hydrogen capture performance and a preparation method thereof. The product is widely used in multiple industries such as construction, chemical industry, metallurgy and household. 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, which is widely used in chemical, household, light industry, construction, metallurgy and other industries. By applying enamel coating on the surface of 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 enamel coating.

[0003] At present, the anti-fish-scaling performance of existing enameled steel is relatively poor. The presence of a large amount of freely diffusible hydrogen in steel is the main cause of the fish-scaling phenomenon in enameled steel. During the high-temperature enameling process, a large amount of hydrogen will penetrate into the interior of the enameled steel. After enameling, these diffusible hydrogen diffuses to the junction of the steel and the enamel layer and aggregates. When the pressure generated by the hydrogen aggregation is greater than the bonding strength of the steel and the enamel layer, fish-scaling defects will occur, resulting in the scrapping of the enameled products. Therefore, it is urgent to improve the anti-fish-scaling performance of enameled steel. At the same time, the strength of enameled steel products is low, the surface quality is poor, and the welding performance is poor, so its performance also needs to be improved. 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 the produced enameled steel products have 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 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%, in addition, the steel also contains 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.

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

[0008] Furthermore, the carbon equivalent (Pcm) is less than 0.16%, and the calculation formula is as follows:

[0009]

[0010] The effects of the chemical elements in the present invention are mainly based on the following principles:

[0011] C: It exists in the form of cementite, interstitial solid solution and TiC in enameled steel and is the most important strengthening element in steel. It plays a beneficial role in improving the strength of enameled steel. Nano-sized TiC is beneficial to anti-fish scale performance and adhesion performance. Too high C is not good for the surface quality of enameled steel, and too low C is not good for the strength of enameled steel. In the present invention, C is controlled to 0.01-0.03%.

[0012] Si: It plays a role of calming and deoxidizing in enameled steel, but a high Si content has an adverse effect on the surface quality of the enameled steel after enameling. In order to ensure the enameling performance and surface quality, Si is controlled to be ≤ 0.01%.

[0013] Mn: It is a commonly used solid solution strengthening element in steel. An appropriate amount of Mn can, on the one hand, ensure the enameling performance and avoid coating defects caused by softening of the steel plate. On the other hand, it can ensure the forming performance and welding performance of the enameled steel plate. In order to ensure the strength of the enameled steel, Mn is 1.60-1.80%.

[0014] P: Aggregation and growth at the grain boundary will reduce the formability and toughness of the enameled steel and cause cold brittleness. Therefore, in the present invention, P is controlled to be ≤ 0.010%.

[0015] S: is a harmful element in steel, and the lower its content, the better. However, in the present invention, S generates a large number of Mn-SOBN-La inclusions, as well as LaS, La2O2S and MgS inclusions in the steel. These inclusions act as hydrogen traps to improve the anti-fish scale explosion performance and adhesion performance of the enameled steel. Therefore, the S content is controlled to 0.06-0.08%.

[0016] Ti: On the one hand, it combines with C to form 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 anti-scale explosion performance of enameled steel. In the present invention, the Ti content is controlled at 0.08-0.12%.

[0017] V: It is a microalloying element in steel and plays a role in precipitation strengthening. V combines with C and N to form VN and VC. While improving the strength of enameled steel, it can also serve as a hydrogen trap to improve the anti-fish scale explosion performance of enameled steel. In the present invention, the V content is controlled at 0.05-0.08%.

[0018] La+Mg: The main function is to modify the inclusions and play the role of oxide metallurgy to form spherical and point-shaped Mn-SOBN-La inclusions and LaS, La2O3, La2O2S, MgS and MgO inclusions, inhibiting the brittleness and white spots caused by hydrogen in the steel, reducing the diffusion coefficient of hydrogen, delaying the enrichment of hydrogen in the plastic zone at the crack tip, and prolonging the incubation period and fracture time of crack propagation. The above inclusions act as hydrogen traps to improve the anti-scale explosion performance and adhesion performance 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 generate Ti(C, N), VN, BN, etc., which will play a role in precipitation strengthening and grain refinement in steel, thereby improving the strength of the enameled steel plate and the fish scale resistance of the enameled steel. In the present invention, the N content is controlled at 0.0080-0.010%.

[0020] B: mainly combines with N to form BN particles. BN has good stability and is not easily dissolved at high temperatures. It has a stable effect of improving anti-fish scale explosion. In addition, B is concentrated at the austenite grain boundary to inhibit the precipitation of proeutectoid ferrite, so that carbides are dispersed and precipitated in the low temperature zone. In the present invention, the B content is controlled at 0.0030-0.0050%.

[0021] Alt: It reacts with N to form AlN, which refines the grains and prevents the grains from growing during enameling. With the cooperation of specific processes, the strength of enameled steel sheets 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 invention has uniform anti-fish scale performance before and after enameling.

[0026] Furthermore, the microstructure of the high-strength enameled steel plate is ferrite and bainite, and a large number of spherical Mn-SOBN-La inclusions, as well as LaS, La2O3, La2O2S and MgS inclusions are distributed in the ferrite matrix. At the same time, there are also a large number of VN, TiC, and BN precipitates with a size less than 7.5 nm. The above-mentioned inclusions and precipitates can act as stable hydrogen traps, significantly improving the anti-fishscale performance of 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 steel tapping temperature is ≥1650°C.

[0032] Furthermore, in step (1), a 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 drawn for cyclic treatment to remove C and H in the steel, alloying, and La and Mg are added after the RH refining is completed. Argon is soft-blown for ≥12 minutes to make the chemical composition of the molten steel meet the composition requirements of the above-mentioned hot-rolled enameled steel. The flow rate of the soft argon is 40-70 NL / min, so that the steel slag creeps slightly and the molten steel is not 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 heating temperature of the slab before hot rolling is controlled at 1250-1280°C for 90-120 min; the hot rolling includes rough rolling and finish rolling, the start rolling temperature of the rough rolling 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 only after 44 to 56 hours.

[0042] It should be pointed out that obtaining enameled steel with good hydrogen capture performance is not only related to the composition design, but also to the production process. Only through reasonable composition design combined with optimized production process can the expected microstructure be obtained, thereby effectively improving the anti-fish scale explosion performance and adhesion performance of enameled steel.

[0043] The enameled steel production process described in 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 content of O, H and inclusions at the expected level is beneficial to improving the anti-scale burst performance and adhesion performance of enameled steel.

[0046] 2. Limiting the billet drawing 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, final rolling temperature and coiling temperature, the TiC grain size is ≤7.5nm and exists in the form of interphase precipitation, which is beneficial to improve the anti-fish scale explosion performance of enameled steel.

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

[0050] 6. The purpose of limiting the slow cooling time is to allow the alloy elements in the steel to be fully precipitated, thereby ensuring the uniformity of the performance of the enameled steel plate and its anti-fish scale performance.

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

[0052] Through reasonable composition design and optimized process control, a large number of spherical Mn-SOBN-La inclusions, as well as LaS, La2O3, La2O2S and MgS inclusions are distributed in the ferrite matrix, and there are also a large number of VN, TiC, and BN precipitates with a size less than 7.5nm. These inclusions and precipitates can act as stable hydrogen traps to capture a large amount of diffusible hydrogen, thereby improving the anti-fish scale explosion performance of enameled steel. In addition, since Mn-SOBN-La inclusions, as well as LaS, La2O3, La2O2S and MgS inclusions will not grow significantly during the enameling process (enameling temperature is 800-900℃), their hydrogen capture capacity will not be significantly reduced, so the enameled steel still has excellent anti-fish scale explosion performance after two enamelings.

[0053] The enameled steel prepared by the invention has high strength, good surface quality, welding performance, anti-thinning ability and forming performance, as well as good adhesion performance, and good anti-scale sensitivity after enameling.

[0054] In addition, the steel plate prepared by the present invention can be used to make pressure vessels (such as steel for electric water heater inner tanks, etc.). For pressure vessels (such as steel for electric water heater inner tanks, etc.), the steel plate still has a high yield strength after two high-temperature enameling processes at 800 to 900°C, thereby ensuring the fatigue performance and pressure requirements of the enameled inner tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the specific implementation manner of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation manner or the description of the prior art are briefly introduced below.

[0056] Figure 1 The microstructure diagram (500×) of the enameled steel plate prepared in Example 1 of the present invention;

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

[0058] Figure 3 Scanning electron microscope photo of the enameled steel plate prepared in Example 1 of the present invention (1000×)

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

[0060] The following non-limiting embodiments may enable a person 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 components in 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%, in addition, the steel further comprises N: 0.0080-0.0100%, B: 0.0030-0.0050%, La+Mg: 0.0050-0.0080% (La:Mg=(2.0-3.0):1), and the rest is Fe and other inevitable impurities; Pcm c <0.16%.

[0063] The preparation method of 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: top and bottom 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, and vacuum is evacuated for circulation treatment to remove C and H in the steel. La and Mg are added at the end of refining. Soft blowing of argon gas is ≥12min, and the flow rate of soft blowing argon gas is 40~70NL / min;

[0067] (4) Continuous casting: The continuous casting billet drawing 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 final 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, and the thickness of the steel plate 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 is 15:3, the soft blowing of argon is 15 minutes, and the soft blowing of argon flow rate is 50NL / min; the continuous casting billet drawing speed is 1.1m / min, the thickness of the continuous casting billet is 230mm, the thickness of the intermediate billet is 40mm, and the thickness of the finished enameled steel plate is 4.0mm.

[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 sheet 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 shown in 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 explosion 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 explosion 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, 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] It can be seen from Table 3 that 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-fish scale explosion performance before and after enameling, and is particularly suitable for products with high requirements for anti-fish scale explosion performance.

Claims

1. A high-strength enameled steel plate with excellent hydrogen capture performance, characterized in that: The invention comprises the following chemical compositions in 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 are Fe and other inevitable impurities.

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 to 16.0 mm.

5. The high-strength enameled steel plate with excellent hydrogen capture performance according to claim 1, characterized in that: 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 as follows: temperature is 800-900°C and time is 2.0-3.0h.

6. 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; after the RH refining, La and Mg are added, and soft blowing of argon gas is ≥12min, and the flow rate of soft blowing of argon gas 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 plates; 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.

7. The preparation method according to claim 6, 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.

8. The preparation method according to claim 6, characterized in that: 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.; the slab heating temperature before hot rolling is controlled at 1250-1280° C., and the time is 90-120 min.

9. The preparation method according to claim 6, 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.

10. The preparation method according to claim 6, characterized in that: In step (2), the water temperature of the cooling water for laminar cooling is ≤28°C; the slow cooling treatment is: the coiled steel plate enters a slow cooling pit for slow cooling, and the slow cooling treatment time is 44 to 56 hours.

Images