Method for improving ballistic work of thermomechanically rolled Q420qENH high-strength steel plate

Abstract

The invention discloses a method for improving impact energy of a hot-mechanical rolled Q420qENH high-strength steel plate, which comprises the following steps: carrying out tempering heat treatment on the hot-mechanical rolled Q420qENH high-strength steel plate with the thickness specification of 10.0-60.0 mm, tempering at the tempering temperature of 555-625 DEG C according to the thickness specification of the steel plate, and keeping the temperature for 25-35 minutes; after the steel plate is treated, the low-temperature impact energy at the temperature of minus 40 DEG C is stably controlled to be 200 J or above. The method is simple to operate and suitable for industrial production; the Q420qENH steel plate produced through the method is high in strength, good in impact toughness and excellent in forming performance and welding performance, the impact energy at the low temperature of-40 DEG C is stably controlled to be 200 J or above, and the mechanical property and the technological property meet the technical requirements of users.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical plate production, and in particular relates to a method for improving the impact energy of a thermomechanically rolled Q420qENH high-strength steel plate. Background Art

[0002] High-strength weathering structural steel is widely used in steel structure construction fields such as container plates, railway trucks, building bridges, and power towers due to its high strength level, excellent weathering resistance, and processing formability. Although the addition of weathering elements such as copper, chromium, and nickel makes the production cost slightly higher than that of traditional structural steel, its longer service life, lower maintenance and protection costs, and excellent paint-free use make it more suitable for areas that cannot be repaired or are at risk. With the advancement of national infrastructure and the advancement of science and technology, the application of weathering structural steel has expanded to environments with harsh geological conditions such as deserts and cold regions. In order to ensure the safety of weathering structural steel, higher requirements are placed on its low-temperature impact toughness. Due to its high alloy content, the thermomechanically rolled (TMCP) Q420qENH high-strength steel plate has high requirements for the stability control of rolling temperature, post-rolling cooling rate, and final cooling temperature during the production process (narrow process window), resulting in low low-temperature impact performance of the steel plate or large fluctuations in impact value. It is urgent to develop a method to improve the impact work of thermomechanically rolled (TMCP) Q420qENH high-strength steel plate. Summary of the invention

[0003] The purpose of the present invention is to provide a method for improving the impact energy of a thermomechanically rolled Q420qENH high-strength steel plate. The thickness specification of the steel plate is 10.0 mm-60.0 mm. The present invention is simple to operate and is suitable for industrial production. The Q420qENH steel plate produced by the present invention has high strength, good impact toughness, excellent forming performance and welding performance, and the low-temperature impact energy of -40°C is stably controlled to be above 200 J, and the mechanical properties and process performance meet the technical requirements of users.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The invention discloses a method for improving the impact energy of a thermomechanically rolled Q420qENH high-strength steel plate. The thermomechanically rolled Q420qENH high-strength steel plate is subjected to tempering heat treatment, the thickness specification of the steel plate is 10.0 mm-60.0 mm, the tempering temperature is selected according to the thickness specification of the steel plate, the tempering temperature is 555° C.-625° C., and the heat preservation is performed for 25-35 minutes; after the treatment, the low-temperature impact energy of the steel plate at -40° C. is stably controlled to be above 200 J.

[0006] Furthermore, the mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.08%-0.11%, Si: 0.20%-0.30%, Mn: 1.30%-1.50%, P: ≤0.010%, S≤0.005%, Alt: 0.020%-0.035%, Nb: 0.035%-0.045%, Ti: 0.010%-0.020%, Ni: 0.30%-0.40%, Cr: 0.30%-0.50%, Cu: 0.30%-0.50%, and the rest is Fe and unavoidable impurities.

[0007] Furthermore, the corrosion resistance index I>6.5.

[0008] Furthermore, the mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.08%, Si: 0.26%, Mn: 1.36%, P: 0.009%, S: 0.001%, Alt: 0.030%, Nb: 0.041%, Ti: 0.012%, Ni: 0.36%, Cr: 0.39%, Cu: 0.39%, and the rest is Fe and unavoidable impurities.

[0009] Furthermore, the mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.09%, Si: 0.25%, Mn: 1.35%, P: 0.008%, S: 0.004%, Alt: 0.027%, Nb: 0.039%, Ti: 0.017%, Ni: 0.40%, Cr: 0.39%, Cu: 0.39%, and the rest is Fe and unavoidable impurities.

[0010] Furthermore, the mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.10%, Si: 0.26%, Mn: 1.36%, P: 0.008%, S: 0.005%, Alt: 0.038%, Nb: 0.036%, Ti: 0.016%, Ni: 0.35%, Cr: 0.38%, Cu: 0.40%, and the rest is Fe and unavoidable impurities.

[0011] Furthermore, the mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.09%, Si: 0.24%, Mn: 1.37%, P: 0.010%, S: 0.003%, Alt: 0.026%, Nb: 0.038%, Ti: 0.013%, Ni: 0.38%, Cr: 0.40%, Cu: 0.38%, and the rest is Fe and unavoidable impurities.

[0012] Furthermore, the main production process parameters of the thermomechanically rolled Q420qENH high-strength steel plate are as follows:

[0013] Step 1: Smelting-continuous casting production process, KR desulfurization-converter-LF refining-RH vacuum treatment-slab continuous casting-slow cooling; Among them:

[0014] (1) The sulfur content of molten iron after pretreatment is ≤0.005%. Slag must be removed after desulfurization to ensure that the molten iron contains less slag;

[0015] (2) Use self-produced low-sulfur scrap steel, the converter end point is hit once or the number of re-blowing does not exceed one, and the steel tapping temperature is ≥1610℃;

[0016] (3) LF refining performs slag desulfurization, composition adjustment and temperature raising operations according to the composition and temperature of the molten steel in the converter, so that the composition and temperature of the molten steel meet the requirements of RH and continuous casting;

[0017] (4) RH vacuum treatment time ≥ 20 min. After the RH vacuum treatment, adjust the argon flow rate to make the molten steel in a soft blowing state, feed calcium wire for calcium treatment, and the molten steel [Ca] is 0.0008-0.0025% after wire feeding. Ensure that the soft blowing time is ≥ 10 min after wire feeding;

[0018] (5) The target superheat of the continuous casting process is 20-30°C, the casting is protected throughout the process, electromagnetic stirring and light pressure are used, the casting speed is controlled at 0.8-1.1m / min to ensure the quality of the ingot, and the ingot is slowly cooled in the insulation pit for ≥48 hours;

[0019] Step 2: The slab is put into the furnace for heating; the slab time in the furnace, soaking time and out-of-furnace temperature are strictly controlled, the time in the furnace is ≥220min, the soaking time is 30-60min, and the out-of-furnace temperature is 1230±20℃;

[0020] Step 3: Slab rolling, including rough rolling and finish rolling:

[0021] (1) Rough rolling: After the billet comes out of the furnace, it is quickly sent to the descaling machine to remove the iron oxide scale. The rough rolling is completed with as few passes as possible. The starting temperature of the rough rolling is ≥1100℃, and the final thickness of the rough rolling is 2-4 times that of the finished product;

[0022] (2) Finish rolling: After rough rolling, the slab is kept warm, rolling is carried out away from the recrystallization zone to avoid mixed crystals. The start rolling temperature of the finishing rolling is ≤950°C, and the final rolling temperature of the finishing rolling is 790°C±10°C-820°C±10°C;

[0023] Step 4: Laminar cooling. The cooling mode of the rolled steel plate adopts the laminar cooling of the self-learning calculation result of the secondary system; the final cooling temperature is 640℃±25℃;

[0024] Step 5: Straighten the steel plate according to the thickness specification of the steel plate and the actual shape of the steel plate after cooling.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are:

[0026] The Q420qENH steel plate produced by the present invention has high strength, good impact toughness, excellent forming performance and welding performance, and the low-temperature impact energy of -40°C is stably controlled to be above 200J, and the mechanical properties and process performance meet the technical requirements of users. At the same time, the operation method of the present invention is simple and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings.

[0028] Figure 1 This is the microstructure diagram of the steel plate of Example 3 of the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in more detail below through specific examples and comparative examples. The comparative examples include the first step, the second step, the third step, the fourth step, and the fifth step of the technical solution; the examples include the first step, the second step, the third step, the fourth step, the fifth step, and the sixth step of the technical solution. The examples are merely descriptions of the best implementation of the present invention and do not limit the scope of the present invention in any way.

[0030] Comparative Example

[0031] The molten iron is pre-treated for desulfurization, and the top and bottom combined blowing converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1620℃. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1562℃. After LF refining outside the furnace, the molten steel is subjected to RH vacuum treatment, and the vacuum time is maintained for 20min. The slab is continuously cast according to the smelting chemical composition shown in Table 1, with an overheat of 26℃, followed by slab cleaning, slow cooling, and continuous casting billet quality inspection. The slab heating temperature is 1230℃, the heating time is 250min, the soaking time is 50min, and the heated slab is dephosphorized by high-pressure water. After descaling, rolling is carried out. Rough rolling and finishing rolling are both carried out using a 2-roll reversible rolling mill. The starting temperature of rough rolling is 1180℃, and the rolling is carried out until the intermediate billet thickness is reached. The average starting temperature of finishing rolling is 940℃, and the average final temperature of finishing rolling is 800℃. The final cooling temperature of the steel plate after laminar cooling is 655℃, and the finished product thickness is 22.0mm. Straightening is then carried out. Finally, sample the product quality according to the standard.

[0032] Example 1

[0033] The molten iron is pre-treated for desulfurization, and the top and bottom combined blowing converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1643℃. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1565℃. After LF refining outside the furnace, the molten steel is subjected to RH vacuum treatment, and the vacuum time is maintained for 22min. The slab is continuously cast according to the smelting chemical composition shown in Table 1, with an overheat of 27℃, followed by slab cleaning, slow cooling, and continuous casting billet quality inspection. The slab heating temperature is 1225℃, the heating time is 245min, the soaking time is 60min, and the heated slab is dephosphorized by high-pressure water. After descaling, rolling is carried out. Rough rolling and finishing rolling are both carried out using a 2-roll reversible rolling mill. The starting temperature of rough rolling is 1170℃, and the steel is rolled to the intermediate billet thickness for waiting. The average starting temperature of finishing rolling is 948℃, and the average final temperature of finishing rolling is 790℃. The final cooling temperature of the steel plate after laminar cooling is 660℃, and the finished product thickness is 14.0mm. Straightening is then carried out. After shot peening, the straightened steel plate is subjected to tempering heat treatment, and the tempering process is 620℃ for 30 minutes. Finally, standard sampling is carried out for product quality inspection.

[0034] Example 2

[0035] The molten iron is pre-treated for desulfurization, and the top and bottom combined blowing converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1655℃. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1554℃. After LF refining outside the furnace, the molten steel is subjected to RH vacuum treatment, and the vacuum time is maintained for 23min. The slab is continuously cast according to the smelting chemical composition shown in Table 1, with an overheat of 29℃, followed by slab cleaning, slow cooling, and continuous casting billet quality inspection. The slab heating temperature is 1220℃, the heating time is 250min, the soaking time is 45min, and the heated slab is dephosphorized by high-pressure water. After descaling, rolling is carried out. Rough rolling and finishing rolling are both carried out using a 2-roll reversible rolling mill. The starting temperature of rough rolling is 1175℃, and the steel is rolled to the intermediate billet thickness for waiting. The average starting temperature of finishing rolling is 900℃, and the average final temperature of finishing rolling is 810℃. The final cooling temperature of the steel plate after laminar cooling is 645℃, and the finished product thickness is 30.0mm. Straightening is then carried out. After shot peening, the straightened steel plate is subjected to tempering heat treatment, and the tempering process is 600℃ for 30 minutes. Finally, sample the product quality according to the standard.

[0036] Example 3

[0037] The molten iron is pre-treated for desulfurization, and the top and bottom combined blowing converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1641°C. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1560°C. After LF refining outside the furnace, the molten steel is subjected to RH vacuum treatment, and the vacuum time is maintained for 20 minutes. The slab is continuously cast according to the smelting chemical composition shown in Table 1, with an overheat of 27°C, followed by slab cleaning, slow cooling, and continuous casting billet quality inspection. The slab heating temperature is 1230°C, the heating time is 240 minutes, and the soaking time is 50 minutes. The heated slab is dephosphorized with high-pressure water. After descaling, rolling is carried out. Rough rolling and finishing rolling are both carried out using a 2-roll reversible rolling mill. The starting temperature of rough rolling is 1186℃, and the steel is rolled to the intermediate billet thickness for waiting. The average starting temperature of finishing rolling is 890℃, and the average final temperature of finishing rolling is 795℃. The final cooling temperature of the steel plate after laminar cooling is 635℃, and the finished product thickness is 46.0mm. Straightening is then carried out. After shot peening, the straightened steel plate is subjected to tempering heat treatment, and the tempering process is 580℃ for 30 minutes. Finally, sample the product quality according to the standard.

[0038] Example 4

[0039] The molten iron is pre-treated for desulfurization, and the top and bottom combined blowing converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1654℃. Then the molten steel after converter smelting is subjected to LF furnace refining, and the refining temperature is ≥1560℃. After LF furnace refining, the molten steel is subjected to RH vacuum treatment, and the vacuum time is maintained for 21min. The slab is continuously cast according to the smelting chemical composition shown in Table 1, with an overheat of 28℃, followed by slab cleaning, slow cooling, and continuous casting billet quality inspection. The slab heating temperature is 1225℃, the heating time is 235min, and the soaking time is 55min. The heated slab is dephosphorized with high-pressure water. After descaling, rolling is carried out. Rough rolling and finishing rolling are both carried out using a 2-roll reversible rolling mill. The starting temperature of rough rolling is 1170℃, and the steel is rolled to the intermediate billet thickness for waiting. The average starting temperature of finishing rolling is 890℃, and the average final temperature of finishing rolling is 790℃. The final cooling temperature of the steel plate after laminar cooling is 630℃, and the finished product thickness is 56.0mm. Straightening is then carried out. After shot peening, the straightened steel plate is subjected to tempering heat treatment, and the tempering process is 560℃ for 30 minutes. Finally, standard sampling is carried out for product quality inspection.

[0040] The chemical compositions of the comparative examples and embodiments 1 to 4 of the Q420qENH steel plate of the present invention are shown in Table 1. The mechanical property test values ​​of the comparative examples and embodiments are shown in Table 2. It can be seen that the low-temperature impact toughness value of the embodiment of the present invention is stably controlled at more than 200 J, which greatly improves the low-temperature toughness of the Q420qENH steel plate and has good stability. It should be noted that all similar changes directly derived or associated from the contents disclosed in the present invention by those skilled in the art should fall within the scope of protection of the present invention.

[0041] Table 1 Chemical composition (wt%) of comparative examples and embodiments 1 to 4 of the present invention

[0042]

[0043]

[0044] Table 2 Mechanical properties and process properties of the comparative examples and embodiments 1 to 4 of the present invention

[0045]

[0046] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate, characterized in that: The thermomechanically rolled Q420qENH high-strength steel plate is subjected to tempering heat treatment, the thickness of the steel plate is 10.0mm-60.0mm, the tempering temperature is selected according to the thickness of the steel plate, the tempering temperature is 555℃-625℃, and the heat preservation is 25-35min; after the treatment, the low-temperature impact energy of the steel plate at -40℃ is stably controlled to be above 200J.

2. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 1, characterized in that: The mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.08%-0.11%, Si: 0.20%-0.30%, Mn: 1.30%-1.50%, P: ≤0.010%, S≤0.005%, Alt: 0.020%-0.035%, Nb: 0.035%-0.045%, Ti: 0.010%-0.020%, Ni: 0.30%-0.40%, Cr: 0.30%-0.50%, Cu: 0.30%-0.50%, and the rest is Fe and unavoidable impurities.

3. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 2, characterized in that: Corrosion resistance index I>6.

5.

4. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 2, characterized in that: The mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.08%, Si: 0.26%, Mn: 1.36%, P: 0.009%, S: 0.001%, Alt: 0.030%, Nb: 0.041%, Ti: 0.012%, Ni: 0.36%, Cr: 0.39%, Cu: 0.39%, and the rest is Fe and unavoidable impurities.

5. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 2, characterized in that: The mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.09%, Si: 0.25%, Mn: 1.35%, P: 0.008%, S: 0.004%, Alt: 0.027%, Nb: 0.039%, Ti: 0.017%, Ni: 0.40%, Cr: 0.39%, Cu: 0.39%, and the rest is Fe and unavoidable impurities.

6. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 2, characterized in that: The mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.10%, Si: 0.26%, Mn: 1.36%, P: 0.008%, S: 0.005%, Alt: 0.038%, Nb: 0.036%, Ti: 0.016%, Ni: 0.35%, Cr: 0.38%, Cu: 0.40%, and the rest is Fe and unavoidable impurities.

7. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 2, characterized in that: The mass percentage of the chemical composition of the thermomechanically rolled Q420qENH high-strength steel plate is C: 0.09%, Si: 0.24%, Mn: 1.37%, P: 0.010%, S: 0.003%, Alt: 0.026%, Nb: 0.038%, Ti: 0.013%, Ni: 0.38%, Cr: 0.40%, Cu: 0.38%, and the rest is Fe and unavoidable impurities.

8. The method for improving the impact energy of thermomechanically rolled Q420qENH high-strength steel plate according to claim 1, characterized in that: The main production process parameters of the thermomechanically rolled Q420qENH high-strength steel plate are as follows: Step 1: Smelting-continuous casting production process, KR desulfurization-converter-LF refining-RH vacuum treatment-slab continuous casting-slow cooling; Among them: (1) The sulfur content of molten iron after pretreatment is ≤0.005%. Slag must be removed after desulfurization to ensure that the molten iron contains less slag; (2) Use self-produced low-sulfur scrap steel, the converter end point is hit once or the number of re-blowing does not exceed one, and the steel tapping temperature is ≥1610℃; (3) LF refining performs slag desulfurization, composition adjustment and temperature raising operations according to the composition and temperature of the molten steel in the converter, so that the composition and temperature of the molten steel meet the requirements of RH and continuous casting; (4) RH vacuum treatment time ≥ 20 min. After the RH vacuum treatment, adjust the argon flow rate to make the molten steel in a soft blowing state, feed calcium wire for calcium treatment, and the molten steel [Ca] is 0.0008-0.0025% after wire feeding. Ensure that the soft blowing time is ≥ 10 min after wire feeding; (5) The target superheat of the continuous casting process is 20-30°C, the casting is protected throughout the process, electromagnetic stirring and light pressure are used, the casting speed is controlled at 0.8-1.1m / min to ensure the quality of the ingot, and the ingot is slowly cooled in the insulation pit for ≥48 hours; Step 2: The slab is put into the furnace for heating; the slab time in the furnace, soaking time and out-of-furnace temperature are strictly controlled, the time in the furnace is ≥220min, the soaking time is 30-60min, and the out-of-furnace temperature is 1230±20℃; Step 3: Slab rolling, including rough rolling and finish rolling: (1) Rough rolling: After the billet comes out of the furnace, it is quickly sent to the descaling machine to remove the iron oxide scale. The rough rolling is completed with as few passes as possible. The starting temperature of the rough rolling is ≥1100℃, and the final thickness of the rough rolling is 2-4 times that of the finished product; (2) Finish rolling: After rough rolling, the slab is kept warm, rolling is carried out away from the recrystallization zone to avoid mixed crystals. The start rolling temperature of the finishing rolling is ≤950°C, and the final rolling temperature of the finishing rolling is 790°C±10°C-820°C±10°C; Step 4: Laminar cooling. The cooling mode of the rolled steel plate adopts the laminar cooling of the self-learning calculation result of the secondary system; the final cooling temperature is 640℃±25℃; Step 5: Straighten the steel plate according to the thickness specification of the steel plate and the actual shape of the steel plate after cooling.

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