A medium-thickness steel sheet for a thin-gauge container having low-temperature impact resistance and a method of producing the same

Abstract

The application discloses a thin-gauge medium-thickness steel plate with low-temperature impact resistance and a production method thereof. The steel plate comprises the following chemical components in percentage by weight: C: 0.14-0.17%, Si: 0.3-0.5%, Mn: 1.35-1.50%, P: <=0.016%, S <=0.008%, Ni: <=0.1%, V: <=0.03%, Ti: <=0.020%, Nb: 0.01-0.02%, Als: 0.022-0.04%, and the balance of Fe and other inevitable impurities. By controlling the contents of carbon, silicon and manganese and through a hot rolling + normalizing process, the thin-gauge low-temperature impact-resistant steel plate with a thickness of <=7mm is produced, the transverse impact value of which at-40 DEG C reaches 95J or more, the yield strength reaches 350MPa or more, the tensile strength is 530-600MPa, and the elongation reaches 30%.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to a medium-thick steel plate for thin-gauge containers with low-temperature impact resistance and its production method. Background Technology

[0002] Cryogenic pressure vessel steel is mainly used in the storage tank industry for cryogenic liquids such as liquid hydrogen, liquid nitrogen, and liquid oxygen. The demand for cryogenic pressure vessels for transporting and storing cryogenic liquids is constantly increasing across various industries. This necessitates that cryogenic pressure vessels maintain more robust transport and storage performance, continuously improving the steel used in them and substantially enhancing the application quality of cryogenic pressure vessels from a material perspective. Furthermore, due to differences in pressure and function, steel plates of various specifications must meet the application requirements.

[0003] Medium-thick steel plates for high-strength containers with thin specifications and low-temperature (-40℃) impact requirements, with a thickness not exceeding 7mm, yield strength ≥310MPa, tensile strength 490~620MPa, elongation ≥21%, and transverse Charpy V-shaped transverse impact energy ≥21J at -40℃.

[0004] Chinese patent CN116145031A discloses a 16MnDR steel plate. The chemical composition and mass percentage of the steel plate are as follows: C: 0.07%-0.09%, Si: 0.15%-0.30%, Mn: 1.50%-1.60%, P≤0.010%, S≤0.003%, Nb: 0.030%-0.035%, with the balance being Fe and unavoidable impurities. The production method of the steel plate includes electric arc furnace primary refining, LF refining, VD vacuum treatment, continuous casting, rolling, and normalizing processes. This patent utilizes a controlled rolling and cooling + normalizing process to produce steel plates with a thickness of 16-60 mm.

[0005] Chinese patent CN102345054A discloses a 120mm thick 16MnDR steel plate for low-temperature pressure vessels, with a carbon content of 0.10-0.17%, a phosphorus content of ≤0.015%, and a sulfur content of ≤0.005%. Through KR hot metal pretreatment, converter smelting, oxygen blowing, LF refining, VD refining, ingot casting, heating, controlled rolling and cooling, stacking cooling, and heat treatment processes, the patent ensures the 16MnDR composition while strictly controlling the content of harmful elements such as P and S that affect the ductility and toughness of the steel plate. It also strictly controls the heating regime during rolling, the final rolling temperature, the red-hot temperature, and the cooling rate during rolling, and employs methods such as slow cooling by stacking copper plates. This ensures that the various performance indicators of the 120mm thick 16MnDR steel plate meet the standard requirements. However, this patent only guarantees low-temperature impact performance at -30℃.

[0006] Chinese patent CN116254398A discloses a 5-6mm normalized rolled steel plate for low-temperature pressure vessels and its production method. This patent adopts a normalizing rolling process of coil rolling and controlled rolling + controlled cooling, which replaces the hot rolling + heat treatment normalizing process.

[0007] In the aforementioned existing technologies, for medium-thickness thin-gauge low-temperature impact 16MnDR steel plates, the production process is all based on the rolling of heavy plate mills and the production of online hot rolling + normalizing process. During the hot rolling process, the billet is heated and the rolling and cooling are controlled. Because the temperature drops very quickly during the rolling process, the uniformity of the metallographic structure of the rolled steel plate is poor, and the impact performance after normalizing is low and difficult to achieve. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides a thin-gauge medium-thick steel plate for containers with low-temperature impact resistance and its production method. By controlling the carbon, silicon and manganese content and using hot rolling + normalizing process, a thin-gauge low-temperature impact resistant steel plate with a thickness of ≤7mm is produced. Its transverse impact value at -40℃ reaches above 95J, its yield strength reaches above 350MPa, its tensile strength is 530-600MPa, and its elongation reaches 30%.

[0009] The technical solution adopted in this invention is as follows:

[0010] A medium-thick steel plate for thin-gauge containers with low-temperature impact resistance comprises the following chemical composition by weight percentage: C: 0.14–0.17%, Si: 0.3–0.5%, Mn: 1.35–1.50%, P: ≤0.016%, S≤0.008%, Ni: ≤0.1%, V: ≤0.03%, Ti: ≤0.020%, Nb: 0.01–0.02%, Als: 0.022–0.04%, with the balance being Fe and other unavoidable impurities.

[0011] The metallographic structure of the thin-gauge container medium-thick steel plate with low-temperature impact resistance is ferrite + pearlite.

[0012] The thickness of the medium-thick steel plate used for thin-gauge containers with low-temperature impact resistance is ≤7mm.

[0013] The medium-thick steel plate for thin-gauge containers with low-temperature impact resistance has a transverse impact value of over 95J at -40℃, a yield strength of over 350MPa, a tensile strength of 530-600MPa, and an elongation of 30%.

[0014] The present invention also provides a method for producing the aforementioned low-temperature impact resistant medium-thick steel plate for thin-gauge containers, the method comprising the following steps: steelmaking, billet heating, rolling, straightening, cooling and normalizing.

[0015] The steelmaking process includes the following steps: 120t converter smelting, LF refining, RH vacuum refining, slab continuous casting, and billet cleaning.

[0016] The blank size selection position is thickness * width = 180 * 1300 mm.

[0017] In the billet heating step, a walking beam slab heating furnace is used for heating.

[0018] In the billet heating step, the preheating section temperature is 700-900℃, the first heating section temperature is 1050-1150℃, the second heating section temperature is 1220-1260℃, the soaking temperature is 1220-1250℃, and the furnace time is (1.4-1.6)×H minutes, where H is the billet thickness in mm.

[0019] In the rolling process, the roughing and finishing stages are rolled continuously, for a total of 11 passes, without temperature control in between. The roughing temperature is 1070℃~1120℃, the roll speed is 1.0~2.0m / s, and the reduction rate of each of the first three passes or the first two passes before steel transfer is greater than 18%, achieving full recrystallization rolling to achieve large reduction and ensure austenite grain refinement. The reduction of the last pass is 0.6~0.9mm, the steel ejection speed is ≤3m / s, and the final rolling temperature is 830-870℃. After rolling, the steel is air-cooled to room temperature. Under these rolling conditions, rolling stability and continuity can be effectively guaranteed, and the plate shape is good.

[0020] In the rolling process, the reduction rate of the fourth pass is 15-23%, the reduction rate of the fifth to eighth passes is 30-50%, the reduction rate of the ninth pass is 20-25%, and the reduction rate of the tenth pass is 14-16%.

[0021] In the rolling step, a 3800mm rolling mill is used for rolling.

[0022] In the straightening process, there are three straightening passes to ensure that the final straightening temperature is not lower than 550℃; after straightening, the material is air-cooled on a cooling bed.

[0023] In the normalizing process, the normalizing temperature is 850±10℃, and the furnace time is (4.4~4.6)×H minutes, where H is the steel plate thickness in mm; after removal from the furnace, the plate is air-cooled. This invention controls the normalizing temperature within AC3+30~50℃. Within this temperature range, austenite recrystallizes and homogenizes. If this temperature or time is not reached, the degree of austenite recrystallization will not meet the requirements, directly affecting the performance after normalizing heat treatment.

[0024] The medium-thick steel plate for thin-gauge containers with low-temperature impact resistance provided by this invention adopts a low-alloy, low-cost approach, without adding precious alloying elements such as Ni, and controls the C+Si+Mn content, wherein the C content is 0.14%~0.17%, the Mn content is 1.35%~1.5%, and the Si content is 0.2%~0.45%, achieving the purpose of solid solution strengthening. In addition, because phosphorus (P) tends to cause segregation in steel, deteriorating the uniformity of the steel structure and reducing plasticity and low-temperature toughness; sulfur (S) tends to form sulfide inclusions, which have a significant impact on the low-temperature toughness of steel and will cause anisotropy in the properties of steel. Therefore, this steel grade selects P≤0.016% and S≤0.008%.

[0025] The present invention provides a method for producing medium-thick steel plates for thin-gauge containers with low-temperature impact resistance. The main method involves rationally setting the reduction amount of the steel plate. The reduction rate in each of the first three passes or the first two passes before the steel transfer is greater than 18%, achieving a large reduction under complete recrystallization. The reduction amounts in the last two passes are no greater than 2mm and 1.5mm, with reduction rates of 14-16% and 9-13%, respectively. By setting the reduction amount in the final pass, the system evenly distributes the reduction amount in each pass according to the mill capacity, matching the set reduction schedule with the actual reduction schedule. This ensures relatively stable rolling forces in each pass, preventing large changes and guaranteeing a good plate shape, thus solving the problem of thin-gauge rolled plate shape. By controlling the rolling process, the microstructure of the steel is ensured to completely transform from austenite to ferrite + pearlite. Furthermore, the rapid cooling of thin-gauge steel plates refines the grains, improving the overall properties of the steel, thereby obtaining higher strength and impact toughness. Compared with existing technologies, the present invention has the following beneficial effects:

[0026] 1. The low-temperature impact resistant thin-gauge container medium-thick steel plate provided by the present invention has low cost, does not add precious alloy elements such as Ni, and ensures strength indicators by controlling the C+Si+Mn content;

[0027] 2. This invention controls the hot rolling and normalizing process conditions to produce thin-gauge low-temperature impact resistant steel plates with good plate shape and performance that meet the following requirements: transverse impact value of -40℃ reaches above 90J, yield strength reaches above 350MPa, tensile strength is between 530-600MPa, elongation reaches above 30%, and thickness is ≤7mm. Attached Figure Description

[0028] Figure 1 The image shows the metallographic structure of a quarter section of the steel plate in Example 1, with a microstructure of F+P.

[0029] Figure 2 The image shows the metallographic structure of the steel plate at 1 / 2 in Example 1, which is F+B+P.

[0030] Figure 3The image shows the metallographic structure of a quarter section of the steel plate in Example 2, with a microstructure of F+P.

[0031] Figure 4 The image shows the metallographic structure of the steel plate at 1 / 2 in Example 2, which is F+B+P.

[0032] Figure 5 The image shows the metallographic structure at 1 / 4 of the steel plate in Comparative Example 1, with a microstructure of F+P.

[0033] Figure 6 The image shows the metallographic structure at 1 / 2 of the steel plate in Comparative Example 1, with a structure of F+B+P.

[0034] Figure 7 The image shows the metallographic structure at 1 / 4 of the steel plate in Comparative Example 2, with a microstructure of F+P.

[0035] Figure 8 The image shows the metallographic structure at 1 / 2 of the steel plate in Comparative Example 2, which is F+B+P. Detailed Implementation

[0036] This invention provides a medium-thick steel plate for thin-gauge containers with low-temperature impact resistance, comprising the following chemical composition by weight percentage: C: 0.14-0.17%, Si: 0.3-0.5%, Mn: 1.35-1.50%, P: ≤0.016%, S≤0.008%, Ni: ≤0.1%, V: ≤0.03%, Ti: ≤0.020%, Nb: 0.01-0.02%, Als: 0.022-0.04%, with the balance being Fe and other unavoidable impurities.

[0037] The method for producing the thin-gauge medium-thick steel plate for containers with low-temperature impact resistance includes the following steps: steelmaking, billet heating, rolling, straightening, cooling and normalizing.

[0038] The steelmaking process includes the following steps: 120t converter smelting, LF refining, RH vacuum refining, slab continuous casting, and billet cleaning.

[0039] The blank size selection position is thickness * width = 180 * 1300 mm.

[0040] In the billet heating step, a walking beam slab heating furnace is used for heating.

[0041] In the billet heating step, the preheating section temperature is 700-900℃, the first heating section temperature is 1050-1150℃, the second heating section temperature is 1220-1260℃, the soaking temperature is 1220-1250℃, and the furnace time is (1.4-1.6)×H minutes, where H is the billet thickness in mm.

[0042] In the rolling process, the roughing and finishing stages are rolled continuously, for a total of 11 passes, without intermediate temperature control. The roughing temperature is 1070℃~1120℃, the roll speed is 1.0~2.0m / s, and the reduction rate of each of the first three passes or the first two passes before steel transfer is greater than 18%, achieving complete recrystallization rolling to achieve large reduction and ensure austenite grain refinement. The reduction of the last pass is 0.6~1.0mm, the steel ejection speed is ≤3m / s, and the final rolling temperature is 830-870℃. After rolling, air cooling is performed. Under these rolling conditions, rolling stability and continuity can be effectively guaranteed, and the plate shape is good.

[0043] In the rolling process, the reduction rate of the fourth pass is 15-23%, the reduction rate of the fifth to eighth passes is 30-50%, the reduction rate of the ninth pass is 20-25%, the reduction rate of the tenth pass is 14-16%, and the reduction rate of the eleventh pass is 9-13%.

[0044] In the rolling step, a 3800mm rolling mill is used for rolling.

[0045] In the straightening process, there are three straightening passes to ensure that the final straightening temperature is not lower than 550℃; after straightening, the material is air-cooled on a cooling bed.

[0046] In the normalizing process, the normalizing temperature is 850±10℃, the furnace time is (4.4~4.6)×H minutes, where H is the steel plate thickness in mm; after exiting the furnace, the plate is air-cooled.

[0047] The present invention will now be described in detail with reference to the embodiments.

[0048] Example 1

[0049] A medium-thickness steel plate for thin-gauge containers with low-temperature impact resistance comprises the following chemical composition by mass percentage, as shown in Table 1 below, with the remainder being Fe and unavoidable impurities.

[0050] Table 1

[0051] element C Si Mn P S Ni Nb Ti V Als content(%) 0.16 0.34 1.41 0.014 0.001 0.02 0.011 0.012 0.005 0.028

[0052] The production method of the aforementioned medium-thick steel plate for thin-gauge containers with low-temperature impact resistance includes the following steps: steelmaking, billet heating, rolling, straightening, cooling, and normalizing treatment, wherein...

[0053] 1) Billet heating process: billet thickness 180mm, preheating section temperature 775-830℃, first heating section 1055-1120℃, second heating section 1230-1247℃, soaking temperature 1222-1242℃, furnace time 263 minutes, after exiting the furnace, rolling is carried out.

[0054] 2) Rolling process: The rolling mill used is a 3800mm wide and thick plate reversible rolling mill, single stand, with a target plate thickness of 6mm and a target specification of thickness * width = 6 * 2780mm. The billet specification is thickness * width = 180 * 1300mm. The initial rolling temperature is 1097.66℃. In the roughing stage (first three passes), high temperature, low speed, and large reduction rolling are adopted, with reductions of 36.19, 28.75, and 22.57mm, and pass reduction rates of 20.10%, 19.99%, and 19.61%, respectively. There are 11 rolling passes to ensure good plate shape. The reductions of the last three passes are 2.30, 1.27, and 0.88mm, respectively, with rolling speeds of 3.34, 2.56, and 1.39m / s. The final rolling temperature is 844.26℃, followed by air cooling.

[0055] The rolling process is shown in Table 2:

[0056] Table 2

[0057]

[0058]

[0059] Note: In Table 2, the rolling speed is positive when the steel is fed from the front to the back of the machine, and negative when it is fed from the back. The same applies below.

[0060] 3) Straightening and cooling process: After rolling, the steel plate is directly and quickly straightened in three passes to ensure that the final straightening temperature is not lower than 550℃. Then the steel plate is air-cooled on a cooling bed, removed from the cooling bed, and subjected to non-destructive ultrasonic testing online.

[0061] 4) Heat treatment process: normalizing temperature 843~852℃, furnace time 32 minutes, air cooling after taking out of the furnace.

[0062] The mechanical properties of the steel plate produced in this embodiment are shown in Table 3.

[0063] Table 3

[0064]

[0065] Example 2

[0066] A medium-thickness steel plate for thin-gauge containers with low-temperature impact resistance comprises the following chemical composition by mass percentage, as shown in Table 4 below; the remainder is Fe and unavoidable impurities.

[0067] Table 4

[0068] element C Si Mn P S Ni Nb Ti V Als content(%) 0.16 0.34 1.42 0.014 0.002 0.02 0.013 0.005 0.004 0.028

[0069] The production method of the aforementioned medium-thick steel plate for thin-gauge containers with low-temperature impact resistance includes the following steps: steelmaking, billet heating, rolling, straightening, cooling, and normalizing treatment, wherein:

[0070] 1) Billet heating process: billet thickness 180mm, preheating section temperature 762~836℃, first heating section 1113-1135℃, second heating section 1231-1247℃, soaking temperature 1226-1240℃, furnace time 258 minutes, then out of the furnace for rolling.

[0071] 2) Rolling process: The rolling mill used is a 3800mm wide and thick plate rolling mill, single stand, with a target plate thickness of 7mm and a target specification of thickness * width = 7 * 3030mm. The billet specification is thickness * width = 180 * 1300mm. The initial rolling temperature is 1085℃. In the roughing stage (first three passes), high temperature, low speed, and large reduction rolling are adopted, with reductions of 33.45, 27.33, and 23.14mm, and pass reduction rates of 18.59%, 18.65%, and 19.41%, respectively. There are 11 rolling passes to ensure good plate shape. The reductions of the last three passes are 2.93, 1.57, and 0.89mm, respectively, with rolling speeds of 2.63, 2.53, and 1.61m / s. The final rolling temperature is 860.20℃. After rolling, the plate is air-cooled.

[0072] The rolling process is shown in Table 5:

[0073] Table 5

[0074] Daocihao Rolled thickness Rolling force Rolling torque Rolling speed Rolling temperature Indentation (mm) Compression ratio (%) billet 180 1 146.55 17488.12 2494.15 1.35 1083.37 33.45 18.59 2 119.21 18319.41 2633.01 -1.36 1110.25 27.33 18.65 3 96.07 20221.59 2362.14 1.36 1116.89 23.14 19.41 4 74.13 22752.10 2623.13 -1.38 1116.26 21.94 22.83 5 51.61 32147.96 3514.75 1.36 1185.04 22.53 30.39 6 33.02 39231.41 4487.74 -1.32 1186.37 18.59 36.02 7 19.69 46857.62 3645.41 1.85 1169.58 13.33 40.37 8 12.74 44896.17 2583.35 -2.40 1105.99 6.95 35.29 9 9.81 35815.77 1251.50 2.63 1057.51 2.93 23.00 10 8.24 26404.80 655.35 -2.53 963.98 1.57 16.00 11 7.35 35236.89 717.15 1.61 860.20 0.89 10.82

[0075] 3) Straightening and cooling process: After rolling, the steel plate is directly and quickly straightened in three passes to ensure that the final straightening temperature is not lower than 550℃. Then the steel plate is air-cooled on a cooling bed, removed from the cooling bed, and subjected to non-destructive ultrasonic testing online.

[0076] 4) Heat treatment process: normalizing temperature 847~858℃, furnace time 28 minutes, air cooling after taking out of the furnace.

[0077] The mechanical properties of the steel plate produced in this embodiment are shown in Table 6 below.

[0078] Table 6

[0079]

[0080] Comparative Example 1

[0081] A medium-thickness steel plate for thin-gauge containers with low-temperature impact resistance comprises the following chemical composition by mass percentage, as shown in Table 7 below, with the remainder being Fe and unavoidable impurities.

[0082] Table 7

[0083] element C Si Mn P S Ni Nb Ti V Als content(%) 0.14 0.30 1.39 0.012 0.002 0.03 <![CDATA[ 0.008 ]]> 0.010 0.008 0.030

[0084] The production method of the aforementioned medium-thick steel plate for thin-gauge containers with low-temperature impact resistance includes the following steps: steelmaking, billet heating, rolling, straightening, cooling, and normalizing treatment, wherein...

[0085] 1) Billet heating process: billet thickness 180mm, preheating section temperature 770-833℃, first heating section 1048-1113℃, second heating section 1280-1299℃, soaking temperature 1273-1292℃, furnace time 295 minutes, rolling after reaching the temperature;

[0086] 2) Rolling process: The rolling mill used is a 3800mm wide and thick plate rolling mill, single stand, with a target plate thickness of 6mm and a target specification of thickness * width = 6 * 2920mm. The billet specification is thickness * width = 180 * 1300mm. The initial rolling temperature is 1089.25℃. In the roughing stage (first three passes), high temperature, low speed, and large reduction rolling are adopted, with reductions of 32.65, 35.07, and 18.63mm, and pass reduction rates of 18.14%, 23.80%, and 16.59%, respectively. There are 11 rolling passes to ensure good plate shape. The reductions of the last three passes are 2.77, 1.71, and 0.96mm, respectively, with rolling speeds of 3.08, 2.23, and 2.06m / s. The final rolling temperature is 867.52℃, followed by air cooling.

[0087] The rolling process is shown in Table 8:

[0088] Table 8

[0089] Daocihao Rolled thickness Rolling force Rolling torque Rolling speed Rolling temperature Indentation (mm) Compression ratio (%) billet 180 1 147.35 20882.27 3303.13 1.37 1179.25 32.65 18.14 2 112.28 15634.47 2032.09 -1.38 1165.39 35.07 23.80 3 93.65 15951.29 1784.91 1.44 1143.58 18.63 16.59 4 76.38 17670.50 1706.77 -1.48 1130.37 17.27 18.44 5 50.96 32557.22 3734.95 1.42 1125.67 25.42 33.28 6 32.31 36452.57 3899.31 -1.48 1143.98 18.65 36.60 7 17.56 44720.00 3511.42 1.93 1150.97 14.75 45.66 8 11.87 37532.60 1946.67 -2.58 1118.79 5.69 32.39 9 9.10 33348.22 1090.57 3.07 1074.15 2.77 23.36 10 7.39 28634.23 701.48 -2.23 947.71 1.71 18.78 11 6.43 27766.11 494.95 2.06 867.52 0.96 12.99

[0090] 3) Straightening and cooling process: After rolling, the steel plate is directly and quickly straightened in three passes to ensure that the final straightening temperature is not lower than 550℃. Then the steel plate is air-cooled on a cooling bed with an offline temperature of 43℃, and non-destructive ultrasonic testing is performed online.

[0091] 4) Heat treatment process: normalizing temperature 845~855℃, furnace time 31 minutes, air cooling after taking out of the furnace.

[0092] The mechanical properties of the steel plate produced in this embodiment are shown in Table 9.

[0093] Table 9

[0094]

[0095] The results indicate that the steel plate was heated for too long and at too high a temperature, resulting in poor performance.

[0096] Comparative Example 2

[0097] A medium-thickness steel plate for thin-gauge containers with low-temperature impact resistance comprises the following chemical composition by mass percentage, as shown in Table 10 below, with the remainder being Fe and unavoidable impurities, and the chemical composition meets the requirements.

[0098] Table 10

[0099] element C Si Mn P S Ni Nb Ti V Als content(%) 0.15 0.32 1.45 0.015 0.004 0.03 0.010 0.008 0.009 0.026

[0100] The production method of the aforementioned medium-thick steel plate for thin-gauge containers with low-temperature impact resistance includes the following steps: steelmaking, billet heating, rolling, straightening, cooling, and normalizing treatment, wherein:

[0101] 1) Billet heating process: billet thickness 180mm, preheating section temperature 752~841℃, first heating section 1123-1146℃, second heating section 1283-1303℃, soaking temperature 1276-1291℃, furnace time 292 minutes, and rolling after exiting the furnace; that is, the heating temperature and heating time are not controlled within the range required by this invention.

[0102] 2) Rolling process: The rolling mill used is a 3800mm wide and thick plate rolling mill, single stand, with a target plate thickness of 7mm and a target specification of thickness * width = 7 * 2920mm. The billet specification is thickness * width = 180 * 1300mm. The initial rolling temperature is 1190℃. In the roughing stage (first three passes), high temperature, low speed, and large reduction rolling are adopted, with reductions of 32.55, 30.18, and 25.63mm, and pass reduction rates of 18.08%, 20.47%, and 21.86%, respectively. There are 11 rolling passes to ensure good plate shape. The reductions of the last three passes are 3.67, 1.57, and 1.08mm, respectively, with rolling speeds of 2.84, 2.59, and 1.79m / s. The final rolling temperature is 828.76℃. After rolling, the plate is air-cooled.

[0103] The rolling process is shown in Table 11:

[0104] Table 11

[0105]

[0106] 3) Straightening and cooling process: After rolling, the steel plate is directly and quickly straightened in three passes to ensure that the final straightening temperature is not lower than 550℃. Then the steel plate is air-cooled on a cooling bed, sheared, and put into storage.

[0107] 4) Heat treatment process: normalizing temperature 851~857℃, furnace time 29 minutes, air cooling after taking out of the furnace.

[0108] The mechanical properties of the steel plate produced in this embodiment are shown in Table 12 below.

[0109] Table 12

[0110]

[0111] Note: The impact energy in this indicator is low. The main influencing factor is the large deviation in heating quality. In order to maintain the rolling temperature, the heating temperature and heating time are too long.

[0112] Table 13 shows the comprehensive statistics of the steel plates in each embodiment and comparative example.

[0113] Table 13

[0114]

[0115] Note: As can be seen from the performance indicators and metallographic images, the metallographic structure of the comparative example is significantly coarser than that of the example, and the performance indicators are significantly different.

[0116] The above detailed description of a medium-thick steel plate for thin-gauge containers with low-temperature impact resistance and its production method is illustrative rather than limiting. Several embodiments can be listed within the defined scope. Therefore, variations and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for producing a medium-thick steel plate for thin-gauge containers with low-temperature impact resistance, characterized in that, The production method includes the following steps: steelmaking, billet heating, rolling, straightening, cooling and normalizing. In the rolling process, the roughing and finishing stages are rolled continuously, for a total of 11 passes, without temperature control in between. The roughing start temperature is 1070℃~1120℃, the roll speed is 1.0~2.0m / s, the reduction rate of each of the first three passes or the first two passes before steel transfer is greater than 18%, the reduction of the last pass is 0.6~0.9mm, the steel ejection speed is ≤3m / s, and the final rolling temperature is 830-870℃; air cooling is performed after rolling. In the rolling process, the reduction rate of the fourth pass is 15-23%, the reduction rate of the fifth to eighth passes is 30-50%, the reduction rate of the ninth pass is 20-25%, and the reduction rate of the tenth pass is 14-16%. In the normalizing process, the normalizing temperature is 850±10℃, the furnace time is (4.4~4.6)×H minutes, where H is the steel plate thickness in mm; after exiting the furnace, the plate is air-cooled. The medium-thick steel plate for thin-gauge containers with low-temperature impact resistance comprises the following chemical composition by weight percentage: C: 0.14~0.17%, Si: 0.3~0.5%, Mn: 1.35~1.50%, P: ≤0.016%, S≤0.008%, Ni: ≤0.1%, V: ≤0.03%, Ti: ≤0.020%, Nb: 0.01~0.02%, Als: 0.022~0.04%, with the balance being Fe and other unavoidable impurities; The thickness of the medium-thick steel plate for thin-gauge containers with low-temperature impact resistance is ≤7mm; the metallographic structure of the medium-thick steel plate for thin-gauge containers with low-temperature impact resistance is ferrite + pearlite.

2. The production method according to claim 1, characterized in that, The medium-thick steel plate for thin-gauge containers with low-temperature impact resistance has a transverse impact value of over 60J at -40℃, a yield strength of over 350MPa, a tensile strength of 530-600MPa, an elongation of 30%, and a transverse V-shaped impact energy absorption of ≥95J at -40℃.

3. The production method according to claim 1, characterized in that, In the billet heating step, the preheating section temperature is 700-900℃, the first heating section temperature is 1050-1150℃, the second heating section temperature is 1220-1260℃, the soaking temperature is 1220-1250℃, and the furnace time is (1.4-1.6) × H minutes, where H is the billet thickness in mm.

4. The production method according to claim 1, characterized in that, In the straightening process, there are three straightening passes to ensure that the final straightening temperature is not lower than 550℃; after straightening, the material is air-cooled on a cooling bed.

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