High-strength weather-resistant q420qenh medium-thick steel plate and production method thereof

Abstract

The application discloses a high-strength weather-resistant Q420qENH medium-thick steel plate and a production method thereof, and belongs to the field of metallurgical technologies.The high-strength weather-resistant Q420qENH medium-thick steel plate is provided by the application, the low-carbon component design is adopted, and elements such as Cr, Cu, Ni, Nb and rare earth are added to control the microstructure so as to improve the strength and toughness of the steel plate, refine the grain, increase the hardenability of the steel plate, inhibit the formation of ferrite and promote the bainite phase change.In addition, the temperature of each process in the production process is controlled, so that the produced steel plate has the characteristics of pure steel, high density and stable quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, in particular to a high-strength weather-resistant Q420qENH medium-thick steel plate and a production method thereof. BACKGROUND

[0002] The Q420qENH steel plate is mainly used for weather-resistant steel plates (atmospheric corrosion-resistant steel) for large bridges under special weather conditions, and the corrosion resistance is between ordinary steel and stainless steel, and the atmospheric corrosion resistance is 2-8 times that of ordinary steel of the same grade. The corrosion behaviors of the produced weather-resistant bridge steel Q420qENH and the traditional weather-resistant steel 09CuPCrNi in the simulated industrial atmospheric environment are compared and studied through a periodic immersion corrosion test, and the corrosion behaviors are analyzed by means of corrosion morphology observation and electrochemical test. The results show that the microstructure and chemical composition have certain influence on the corrosion resistance of the steel matrix, and after the formation of the protective rust layer, the corrosion resistance mainly depends on the protection of the rust layer; the results of the periodic immersion corrosion test and the electrochemical impedance spectroscopy and linear polarization curve analysis of the rust test show that the industrial atmospheric corrosion resistance of the Q420qENH steel is better than that of the 09CuPCrNi steel. Under the premise of ensuring good processing performance of the steel plate, a rare earth high-strength weather-resistant bridge steel Q420qENH steel plate is developed, the stable performance is effectively obtained, the market demand for structural steel is better met, and important social and economic benefits are obtained.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The purpose of the present application is to provide a high-strength weather-resistant Q420qENH medium-thick steel plate and a production method thereof to overcome the defects in the prior art.

[0005] The technical problem of the present application is solved by adopting the following technical scheme.

[0006] The present application provides a high-strength weather-resistant Q420qENH medium-thick steel plate, which comprises the following chemical components in mass percentage: C: 0.07-0.11%, Si: 0.20-0.40%, Mn: 1.25-1.45%, P≤0.015%, S≤0.005%, Alt: 0.010-0.040%, Nb: 0.010-0.030%, Ni: 0.30-0.40%, Cr: 0.40-0.50%, Cu: 0.25-0.35%, Ti: 0.010-0.020%, Mo: ≤0.02%, Re: 0.0015-0.004%, B≤0.0005%, and the rest is Fe and residual elements.

[0007] The application further provides a production method of the high-strength weather-resistant Q420qENH medium-thick steel plate, which comprises the following steps: heating, rolling and post-rolling cooling.

[0008] The application has the following beneficial effects:

[0009] The application provides a high-strength weather-resistant Q420qENH medium-thick steel plate and a production method thereof. The application controls the microstructure by low-carbon component design, adding Cr, Cu, Ni, Nb and rare earth elements, so as to improve the strength and toughness of the steel plate, refine the grain, increase the hardenability of the steel plate, inhibit the formation of ferrite and promote the bainite phase change. The temperature of each process in the production process is controlled, so that the produced steel plate has the characteristics of pure steel, high density and stable quality. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. Other related drawings can also be obtained by those skilled in the art without creative labor.

[0011] Figure 1 The metallographic structure photo of the steel plate produced in Example 1 at the surface;

[0012] Figure 2 The metallographic structure photo of the steel plate produced in Example 1 at the thickness of 1 / 4;

[0013] Figure 3 The metallographic structure photo of the steel plate produced in Example 1 at the thickness of 1 / 2;

[0014] Figure 4 The spectrum analysis of the steel plate produced in Example 1;

[0015] Figure 5 The photo obtained by surface detector of the steel plate produced in Comparative Example 2;

[0016] Figure 6 The metallographic structure photo of the steel plate produced in Comparative Example 3 at the surface;

[0017] Figure 7 The metallographic structure photo of the steel plate produced in Comparative Example 3 at the thickness of 1 / 4;

[0018] Figure 8 The metallographic structure photo of the steel plate produced in Comparative Example 3 at the thickness of 1 / 2;

[0019] Figure 9 The spectrum analysis of the steel plate produced in Comparative Example 3. DETAILED DESCRIPTION

[0020] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0021] A high-strength weather-resistant Q420qENH medium-thick steel plate and a production method thereof provided by the embodiments of the present application will be described in detail below.

[0022] In order to solve the above technical problems, the present application provides a high-strength weather-resistant Q420qENH medium-thick steel plate, which comprises the following chemical components in percentage by mass: C: 0.07-0.11%, Si: 0.20-0.40%, Mn: 1.25-1.45%, P≤0.015%, S≤0.005%, Alt: 0.010-0.040%, Nb: 0.010-0.030%, Ni: 0.30-0.40%, Cr: 0.40-0.50%, Cu: 0.25-0.35%, Ti: 0.010-0.020%, Mo: ≤0.02%, Re: 0.0015-0.004%, B≤0.0005%, and the rest is Fe and residual elements.

[0023] The high-strength weather-resistant Q420qENH medium plate has the following contents: C can be 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, etc.; Si can be 0.20%, 0.30%, 0.40%, etc.; Mn can be 1.25%, 1.26%, 1.28%, 1.30%, 1.32%, 1.35%, 1.38%, 1.42%, 1.45%, P≤0.015%, S≤0.005%, etc.; Alt can be 0.010%, 0.020%, 0.030%, 0.040%, etc.; Nb can be 0.010%, 0.020%, 0.030%, etc.; Ni can be 0.30%, 0.32%, 0.34%, 0.35%, 0.36%, 0.38%, 0.40%, etc.; Cr can be 0.40%, 0.41%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.50%, etc.; Cu can be 0.25%, 0.27%, 0.28%, 0.29%, 0.30%, 0.32%, 0.33%, 0.35%, etc.; Ti can be 0.011%, 0.013%, 0.015% 0.010%, 0.016%, 0.018%, 0.019%, 0.020%, etc.; Mo can be 0.01%, 0.015%, 0.016%, 0.018%, 0.02%; and Re can be 0.0015%, 0.002%, 0.0025%, 0.003%, 0.004%, etc.

[0024] The rare earth in the high-strength weather-resistant Q420qENH mainly includes La element and Ce element.

[0025] Preferably, the content of La element is 0.0015-0.0040%, and the content of Ce element is 0.0015-0.0040%.

[0026] The high-strength weather-resistant Q420qENH medium plate has the following properties: yield strength Rp0.2≥420 MPa, tensile strength Rm≥550 MPa, elongation A≥20%, yield strength ratio≤0.85, and longitudinal impact energy at 1 / 2 thickness and-40°C≥120 J.

[0027] The high-strength weather-resistant Q420qENH medium plate has a granular sorbite and ferrite composite structure.

[0028] The high-strength weather-resistant Q420qENH medium plate has a thickness of 20-80 mm.

[0029] Meanwhile, the embodiment of the present application also provides a production method of the above-mentioned rare earth high-strength weather-resistant bridge steel Q420qENH medium-thick steel plate, which comprises the following steps: steelmaking, continuous casting, medium-thick plate heating, rolling and cooling processes.

[0030] The steelmaking process comprises converter smelting, LF furnace refining and RH vacuum treatment, and the converter smelting process comprises the following steps: end component control C: >=0.080%, P<=0.010%, S<=0.025%, tundish tapping temperature 1610-1640 DEG C, and tapping slag stopping.

[0031] The refining process comprises the following steps: adding refining agent 400-500 kg, lime 600-800 kg, submerged arc slag 200-250 kg, fluorite 80-150 kg, LF furnace power slag 6-8 minutes, temperature measurement and sampling, white slag feeding aluminum wire, and white slag keeping time >=10 minutes.

[0032] The vacuum process comprises the following steps: ensuring vacuum degree <=133 Pa, vacuum time >=15 min, pure degassing time >=10 min, hydrogen determination when leaving station, and ensuring [H] <=2 ppm when leaving station; adding boron iron after breaking vacuum, then feeding pure calcium wire 200-250 m, soft argon blowing >=8 min after treatment, controlling soft argon blowing flow, and ensuring soft blowing effect (molten steel liquid surface peristalsis).

[0033] The continuous casting process comprises the following steps: well protecting casting during casting, and avoiding bright red in impact area; ensuring overheat 10-30 DEG C, and making continuous casting blank timely enter pit for slow cooling 30-48 hours; blank entering pit temperature should not be lower than 550 DEG C, and after blank leaving pit, it should be far away from hot blank, and should not be stacked on tuyere, but should be stacked in the middle of other cold blanks.

[0034] The heating process comprises the following steps: steel blank preheating section heating temperature <=890 DEG C, first adding section temperature <=1140 DEG C, second adding section temperature 1190 DEG C-1255 DEG C, soaking section temperature 1200-1235 DEG C, and total heating time: 300 mm casting blank >=335 min.

[0035] The rolling process comprises the following steps: differential temperature rolling in recrystallization zone and two-stage controlled rolling process in non-recrystallization zone.

[0036] The first stage adopts differential temperature rolling, the starting rolling temperature is ≥1050℃, the final rolling temperature is > 950℃, the first pass and the third pass use the front cooling device to cool the surface of the steel plate, the cooling water amount is 1300-1500 L / min, the cooling speed is 6.5-7.5℃ / s, the temperature difference between the surface and the core of the steel plate after surface cooling is 150-200℃, the reduction rate of each pass is 9%-10% in the first to fourth rolling passes, the final rolling temperature is 960-1000℃, the second stage adopts non-recrystallization rolling, the starting rolling temperature is 800-880℃, the final rolling temperature is 815-855℃, the cumulative reduction rate is 45%-60%, and the single pass reduction amount is 16-29mm.

[0037] Since the temperature of the surface of the steel plate has been reduced to 940-1050℃, but the temperature of the core of the steel plate is still higher than 1150℃, there is a temperature difference between the surface and the core, and the deformation in the rolling process can better penetrate into the core through differential temperature rolling, thereby increasing the core deformation, increasing the welding probability of core structure defects, improving the core nucleation capacity, refining the core structure, and adding rare earth elements (Re: 0.0015-0.004%) to increase the recrystallization temperature of the steel plate, expand the non-recrystallization temperature range, increase the reduction amount in the non-recrystallization area, and improve the pass deformation rate, and on the other hand, the rare earth elements can change the morphology of the inclusions of the steel grade, form fine precipitated particles, pin at the ferrite grain boundaries, hinder dislocation movement, and inhibit grain growth, thereby further refining the grains of the steel plate.

[0038] The post-rolling cooling process includes: using interval cooling, the water temperature of the steel plate after rolling is ≥826℃, 14 groups of ACC nozzles are opened in intervals, including the first to third, sixth to eighth, eleventh to thirteenth, sixteenth to eighteenth, and twentieth to twenty-first groups, the water amount is 500-550m 3 / h for the first to third groups, 440-470m 3 / h for the sixth to eighth groups, 240-260m 3 / / h for the eleventh to thirteenth and sixteenth to eighteenth groups, and 150-170m 3 / h for the twentieth to twenty-first groups, the cooling roll speed is 1.0-1.20m / s, the red temperature after cooling is 600-650℃, and the steel plate is cooled at 200-300℃ for 24-48 hours after cooling. Due to the addition of 0.0015-0.004% of rare earth Re, the use of rare earth elements forms more Re2O2S and Re x S y inclusions in micron or nanometer level in the steel grade, provides more nucleation points for structure nucleation in the rolling process, pins dislocations, and prevents grain growth during interval cooling. And by controlling the rate and proportion of ferrite and bainite phase transformation through roll speed, the core and surface structure and performance are uniform.

[0039] In the embodiment of the present application, 0.0015-0.004% of rare earth Re, mainly La and Ce elements, is added, preferably, the content of La element is 0.0015-0.0040%, and the content of Ce element is 0.0015-0.0040%, the rare earth elements are used to purify molten steel, and the (Mn, Ca)S or TiN complex inclusions are modified into Re2O2S and Re with smaller size and more quantity x S y The inclusions not only reduce the quantity of TiN inclusions in the steel, but also provide more nucleation points for the subsequent rolling process, which is beneficial to the grain refinement in the rolling process, improves the hardenability of the steel plate by refining the hot-rolled grain of the Q420qENH steel plate, in addition, the rare earth Re, Al, O and S form small inclusions and are enriched at the grain boundaries, which reduces the grain boundary interface energy, increases the "potential barrier" of the other elements in the grain boundary segregation energy, and can inhibit the segregation of C, B and P elements at the grain boundary to a certain extent, reduces the segregation of the steel plate, optimizes the microstructure, and achieves the effect of uniform performance of the steel plate.

[0040] In the embodiment of the present application, the differential temperature rolling is used in the rough rolling stage, which increases the deformation of the core of the steel plate, and in combination with the dispersed rare earth modified inclusions in the steel, the grain of the core structure is refined, and the uniformity of the structure performance of the whole thickness of the steel plate is improved. In the embodiment of the present application, the grain of the steel plate structure is refined after adding the rare earth Re, the grain boundary segregation of the strong hardenability element B is reduced, the hardenability of the steel plate is improved, and the content of the alloy elements such as Mn, Cr and Mo is appropriately reduced.

[0041] The features and performance of the present application are further described in detail below in combination with the embodiments.

[0042] Embodiment 1

[0043] The thickness of the high-strength weather-resistant Q420qENH medium-thick steel plate is 60mm, and the chemical composition and mass percentage of the steel plate are as follows: C: 0.08%, Si: 0.28%, Mn: 1.35%, P: 0.012%, S: 0.003%, Alt: 0.026%, Nb: 0.023%, Ni: 0.35%, Cr: 0.46%, Cu: 0.32%, Ti: 0.016%, Mo: 0.01%, La: 0.0026%, Ce: 0.0024%, B: 0.0003%, and the rest is Fe and residual elements. The CEV calculated according to the formula is 0.45, Pcm is 0.21, and the weathering index I is 6.584.

[0044] The production method comprises heating, rolling and post-rolling cooling processes, and the specific process steps are as follows:

[0045] Heating process: the steel billet containing the above smelting components is transported into a heating furnace which has reached a set furnace temperature, the steel billet has an end face size of 295 mm, the preheating section temperature is 885℃, the first adding section temperature is 1123℃, the second adding section temperature is 1247℃, the soaking temperature is 1226℃, and the total heating time is 368 minutes.

[0046] Rolling process: the first stage rolling open rolling temperature is 1058℃, the first pass and the third pass are rolled before cooling the steel billet by using a cooling device, the cooling water amount is 1310L / min, the cooling speed is 7.12℃ / s, the roller speed is set to 1.0m / s during cooling, and after cooling is completed, normal rolling is performed, the first four passes of rolling reduction amounts are 32mm, 30mm, 29mm and 30mm respectively, the finish rolling temperature is 954℃, the second stage rolling open rolling temperature is 862℃, and the finish rolling temperature is 841℃, and the cumulative reduction rate is 53.1%.

[0047] Post-rolling cooling process: interval cooling is adopted, the steel plate enters the water at a temperature of 826℃ after rolling is completed, the first-3rd, 6th-8th, 11th-13th, 16th-18th and 20th-21st groups of ACC nozzles are opened in intervals, a total of 14 groups, the water amount is 535m 3 / h for the first-3rd group, 460m 3 / h for the 6th-8th group, 255m 3 / h for the 11th-13th and 16th-18th groups, and 158m 3 / h for the 20th-21st group, the cooling roller speed is 1.05m / s, the red temperature after cooling is 602℃, and after cooling is completed, the steel plate is discharged at a temperature of 280℃ and is stacked for cooling for 24 hours.

[0048] The microstructure of the steel plate provided in the embodiment is shown in Figures 1-4 , the mechanical properties of the steel plate are shown in Table 1, and the properties are shown in Table 1.

[0049] Table 1 shows the mechanical property results of the 60mm Q420qENH steel plate in Example 1.

[0050]

[0051] It can be seen from Table 1 and Figures 1-4 that the mechanical properties at the thickness 1 / 4 and the thickness 1 / 2 of the 60mm Q420qENH steel plate are good, which fully meet the requirements of the corresponding standards, and have good strength and toughness matching.

[0052] Comparative Example 1

[0053] Similar to the steps of Example 1, the only difference is that no rare earth elements are added. The surface structure of the steel plate of Comparative Example 1 without rare earth elements is ferrite + pearlite, and there is a certain amount of bainite at the thickness of 1 / 2 in addition to the ferrite + pearlite structure, and there is a certain difference between the core and surface structures, and the longitudinal impact performance at the thickness of 1 / 2 and the Brinell hardness at -40℃ are low, and there is a difference between the surface and core performances.

[0054] Comparative Example 2

[0055] Existing production process examples and corresponding metallographic structure and mechanical properties.

[0056] The thickness of the high-strength weather-resistant Q420qENH medium-thick steel plate is 60mm, and the chemical composition of the steel plate and its mass percentage are: C: 0.08%, Si: 0.28%, Mn: 1.45%, P: 0.012%, S: 0.003%, Alt: 0.026%, Nb: 0.023%, Ni: 0.35%, Cr: 0.46%, Cu: 0.32%, Ti: 0.016%, Mo: 0.15%, La: 0.0045%, Ce: 0.0050%, B: 0.0003%, and the rest is Fe and residual elements. The CEV calculated according to the formula is 0.49, Pcm is 0.22, and the weathering index I is 6.584.

[0057] Compared with Example 1, the amount of rare earth elements is increased, and the results are: a large number of longitudinal cracks appear on the surface of the steel plate, as shown in Figure 5 , and the mechanical test shows that the tensile layering occurs.

[0058] Comparative Example 3

[0059] The thickness of the high-strength weather-resistant Q420qENH medium-thick steel plate is 60mm, and the chemical composition of the steel plate and its mass percentage are: C: 0.08%, Si: 0.28%, Mn: 1.45%, P: 0.012%, S: 0.003%, Alt: 0.026%, Nb: 0.023%, Ni: 0.35%, Cr: 0.46%, Cu: 0.32%, Ti: 0.016%, Mo: 0.015%, La: 0.0026%, Ce: 0.0024%, B: 0.0003%, and the rest is Fe and residual elements. The CEV calculated according to the formula is 0.49, Pcm is 0.22, and the weathering index I is 6.584.

[0060] The production method includes heating, rolling, and post-rolling cooling processes, and the specific process steps are as follows:

[0061] Heating process: the steel billet containing the above smelting components is transported into the heating furnace which has reached the set furnace temperature, the steel billet adopts the end face size of 295 mm, the preheating section temperature is 865℃, the first adding section temperature is 1103℃, the second adding section temperature is 1247℃, the soaking temperature is 1234℃, and the total heating time is 359 minutes.

[0062] Rolling process: the first stage rolling open rolling temperature is 1062℃, the first pass and the third pass rolling are cooled by using the cooling device before rolling, the cooling water amount is 750L / min, the cooling speed is 6.0℃ / s, the roller speed is set to 1.0m / s during cooling, and after cooling, the steel billet is normally rolled, the first four passes rolling reduction is 19mm, 20mm, 18mm and 15mm respectively, the finish rolling temperature is 984℃, the second stage rolling open rolling temperature is 882℃, the finish rolling temperature is 871℃, and the cumulative reduction is 36.5%.

[0063] Post-rolling cooling process: interval cooling is adopted, the steel plate enters the water at a temperature of 796℃ after rolling, the first-3rd, 6th-8th, 11th-13th, 16th-18th and 20th-21st groups of ACC nozzles are opened in intervals, a total of 14 groups, the water amount is 535m 3 / h for the first-3rd group, 460m 3 / h for the 6th-8th group, 255m 3 / h for the 11th-13th and 16th-18th groups, and 158m 3 / h for the 20th-21st group, the cooling roller speed is 1.05m / s, the red temperature after cooling is 602℃, and after cooling is completed, the steel billet is discharged at a temperature of 280℃ and is stacked for cooling for 24 hours.

[0064] The microstructure of the steel plate of Comparative Example 3 is shown in Figure 3 , and the mechanical properties of the steel plate are shown in Table 2.

[0065] Table 2 shows the mechanical property results of the 60mm Q420qENH steel plate in Comparative Example 3.

[0066]

[0067] As can be seen from the performance test results in Table 2, the -40℃ longitudinal impact performance at the thickness 1 / 2 and the Brinell hardness of the 60mm Q420qENH steel plate are low, and there is a difference in performance between the surface and the core.

[0068] The microstructure diagram of the steel plate provided by Comparative Example 3 and the metallographic structure photo of the cutting end after flame cutting are shown in Figures 6-9 , it can be seen that the surface structure of the steel plate is ferrite + pearlite, and there is a certain amount of bainite at the thickness 1 / 2 in addition to the ferrite + pearlite structure, and there is a certain difference between the core and the surface structure.

[0069] Comparative Example 4

[0070] The high-strength weather-resistant Q420qENH medium-thickness steel plate has a thickness of 60 mm, and the chemical composition and mass percentage of the steel plate are as follows: C: 0.08%, Si: 0.28%, Mn: 1.45%, P: 0.012%, S: 0.003%, Alt: 0.026%, Nb: 0.023%, Ni: 0.35%, Cr: 0.46%, Cu: 0.32%, Ti: 0.016%, Mo: 0.015%, Re: 0.0029%, B: 0.0003%, and the rest is Fe and residual elements. The CEV calculated according to the formula is 0.49, Pcm is 0.22, and the weathering index I is 6.584.

[0071] The production method comprises heating, rolling, and post-rolling cooling processes, and the specific process steps are as follows:

[0072] The heating process: the steel billet containing the above-mentioned smelting components is transported into a heating furnace that has reached a set furnace temperature, and the steel billet adopts an end face size of 295 mm, a preheating section temperature of 865℃, a first adding section temperature of 1103℃, a second adding section temperature of 1247℃, a soaking temperature of 1234℃, and a total heating time of 359 minutes.

[0073] The rolling process: the first-stage rolling open rolling temperature is 1062℃, the first pass and the third pass are rolled before cooling the steel billet by using a cooling device, the cooling water amount is 450 L / min, the cooling speed is 3.0℃ / s, the roller speed is set to 1.0 m / s during cooling, normal rolling is performed after cooling is completed, the first four passes of rolling have a reduction of 19 mm, 20 mm, 18 mm, and 15 mm, respectively, the finish rolling temperature is 984℃, the second-stage rolling open rolling temperature is 882℃, the finish rolling temperature is 871℃, and the cumulative reduction rate is 36.5%.

[0074] The post-rolling cooling process: interval cooling is adopted, the plate enters the water at a temperature of 793℃ after rolling is completed, a total of 14 groups of ACC nozzles are opened in intervals, namely, the first to third, sixth to eighth, eleventh to thirteenth, sixteenth to eighteenth, and twentieth to twenty-first groups, the water amount is 535 m 3 / h for the first to third groups, 460 m 3 / h for the sixth to eighth groups, 255 m 3 / h for the eleventh to thirteenth and sixteenth to eighteenth groups, and 158 m 3 / h for the twentieth to twenty-first groups, the cooling roller speed is 1.05 m / s, the red temperature after cooling is 602℃, and the plate is cooled at a temperature of 280℃ for 24 hours after cooling is completed.

[0075] The mechanical properties of the steel plate of Comparative Example 4 are shown in Table 3.

[0076] Table 3: Mechanical property results of the 60 mm Q420qENH steel plate in Comparative Example 4

[0077]

[0078] As shown in Table 3, the properties of the Q420qENH medium-thick steel plate produced in Comparative Example 4 are all poor, and cannot meet the requirements.

[0079] Comparative Example 5

[0080] Compared with Example 1, only the cooling process is changed: non-interval cooling is adopted, the water temperature after rolling is 793℃, the ACC nozzle is directly opened for a total of 18 groups, the water amount is 255m 3 / h, the cooling roll speed is 1.05m / s, the red temperature after cooling is 622℃, and the steel plate is discharged at 280℃ and stacked for 24 hours after cooling. The mechanical properties of the steel plate of Comparative Example 5 are shown in Table 4.

[0081] Table 4: Mechanical property results of the 60mm Q420qENH steel plate in Comparative Example 5

[0082]

[0083] As shown in Table 4, the yield strength and tensile strength of the Q420qENH medium-thick steel plate produced in Comparative Example 5 do not meet the requirements, and the impact is also extremely low.

[0084] As shown above, the high-strength weather-resistant Q420qENH medium-thick steel plate and the production method thereof provided by the embodiment of the present application, the high-strength weather-resistant Q420qENH medium-thick steel plate provided by the embodiment of the present application comprises the following chemical components in percentage by mass: C: 0.07-0.11%, Si: 0.20-0.40%, Mn: 1.25-1.45%, P≤0.015%, S≤0.005%, Alt: 0.010-0.040%, Nb: 0.010-0.030%, Ni: 0.30-0.40%, Cr: 0.40-0.50%, Cu: 0.25-0.35%, Ti: 0.010-0.020%, Mo: ≤0.02%, Re: 0.0015-0.004%, B≤0.0005%, and the rest is Fe and residual elements. The high-strength weather-resistant Q420qENH medium-thick steel plate provided by the embodiment of the present application is designed by low-carbon components, and Cr, Cu, Ni, Nb, rare earth elements and other elements are added to control the microstructure to improve the strength and toughness of the steel plate, refine the grain, and increase the hardenability of the steel plate. And through two-stage controlled rolling (first stage warm rolling, second stage non-recrystallization rolling) and interval cooling, the cooling rate and roll speed are controlled, the rate and proportion of ferrite and bainite phase transformation are controlled, the formation of ferrite is inhibited, and the bainite phase transformation is promoted. The produced high-strength weather-resistant Q420qENH medium-thick steel plate has the characteristics of pure steel, high density and stable quality.

[0085] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A production method of high-strength weather-resistant Q420qENH medium-thick steel plate, characterized by, The high-strength weather-resistant Q420qENH medium plate comprises the following chemical components in percentage by mass: C: 0.07-0.11%, Si: 0.20-0.40%, Mn: 1.25-1.45%, P≤0.015%, S≤0.005%, Alt: 0.010-0.040%, Nb: 0.010-0.030%, Ni: 0.30-0.40%, Cr: 0.40-0.50%, Cu: 0.25-0.35%, Ti: 0.010-0.020%, Mo: ≤0.02%, rare earth Re: 0.0015-0.004%, B≤0.0005%, and the rest is Fe and residual elements. The production method of the high-strength weather-resistant Q420qENH medium plate comprises a heating process, a rolling process and a post-rolling cooling process. The rolling process comprises two-stage controlled rolling process of differential temperature rolling in a recrystallization zone and rolling in a non-recrystallization zone, wherein: The differential temperature rolling in the recrystallization zone comprises: an opening rolling temperature≥1050℃, a finish rolling temperature>950℃, surface cooling of the steel plate by using a pre-cooling device in the first pass and the third pass, a cooling water amount of 1300-1500L / min, a cooling speed of 6.5-7.5℃ / s, so that the temperature difference between the surface and the core of the steel plate reaches 150-200℃ after surface cooling, and a reduction rate of 9%-10% for each pass in the first to fourth passes after cooling, and a finish rolling temperature of 960-1000℃; The rolling in the non-recrystallization zone comprises: an opening rolling temperature of 800-880℃, a finish rolling temperature of 815-855℃, a cumulative reduction rate of 45%-60%, and a single pass reduction amount of 16-29mm; The high-strength weather-resistant Q420qENH medium plate has a granular sorbite and ferrite composite structure, a yield strength Rp0.2≥420MPa, a tensile strength Rm≥550MPa, an elongation A≥20%, a yield strength ratio≤0.85, and a longitudinal impact energy at 1 / 2 thickness at-40℃≥120J.

2. The production method according to claim 1, characterized by, The high-strength weather-resistant Q420qENH medium plate has a thickness of 20-80mm.

3. The production method according to claim 1, characterized by, The rare earth Re mainly comprises La and Ce elements.

4. The production method according to claim 1, characterized by, The heating process comprises: a billet preheating section heating temperature≤890℃, a first heating section temperature≤1140℃, a second heating section temperature of 1190-1255℃, a soaking section temperature of 1200-1235℃, and a total heating time:≥335 minutes for a 300mm cast billet.

5. The production method according to claim 1, characterized by, The post-rolling cooling process comprises: using interval cooling, specifically: the water entry temperature after the steel plate rolling is≥826℃, interval opening ACC nozzle groups 1-3, 6-8, 11-13, 16-18 and 20-21 in total 14 groups, water quantity: 500-550m 3 / h for the first three groups, 440-470m 3 / h for the sixth to eighth groups, 240-260m 3 / h for the eleventh to thirteenth and sixteenth to eighteenth groups, and 150-170m 3 / h for the twentieth to twenty-first groups, the cooling roll speed is 1.0-1.2m / s, the red temperature after cooling is 600-650℃, and after the cooling is completed, the steel plate is discharged at 200-300℃ and is stacked and cooled for 24-48 hours.

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