Q460qE high-strength steel plate with thickness of 10-50mm and excellent low-temperature impact toughness and production method of Q460qE high-strength steel plate

Abstract

The invention discloses a Q460qE high-strength steel plate with the thickness of 10-50 mm and excellent low-temperature impact toughness. The Q460qE high-strength steel plate comprises the following chemical components in percentage by mass: 0.09%-0.11% of C, 0.20%-0.30% of S i, 1.50%-1.70% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.020%-0.035% of Al t, 0.035%-0.045% of Nb, 0.010%-0.020% of T i, 0.035%-0.045% of V, 0.10%-0.20% of Cr and the balance of Fe and impurities. The invention also discloses a production method thereof. The method is suitable for industrial production. The Q460qE steel plate produced through the method has high strength, good impact toughness and excellent forming performance and welding performance, and the impact energy at the low temperature of-40 DEG C is stably controlled to be 150 J or above.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical sheet production, and particularly relates to a Q460qE high-strength steel plate with a thickness of 10 - 50 mm and excellent low-temperature impact toughness. Background Art

[0002] The high-strength bridge structural steel Q460qE has been widely used in the field of steel structure construction such as bridges due to its high strength level and excellent processing formability. With the advancement of national infrastructure construction and the progress of technology, the application of bridge structural steel has expanded to environments with harsh geological conditions, such as desert gobi and alpine regions, etc. While ensuring the strength of the steel plate, good low-temperature toughness also needs to be ensured, and the demand for steel plates with a thickness specification of 10 - 50 mm has increased rapidly. In order to seize the market share, major steel enterprises have scrambled to develop Q460qE. The present invention develops a Q460qE high-strength steel plate with a thickness of 10 - 50 mm and excellent low-temperature impact toughness and its production method. Summary of the Invention

[0003] The purpose of the present invention is to provide a Q460qE high-strength steel plate with a thickness of 10 - 50 mm and excellent low-temperature impact toughness. The operation of the present invention is simple and suitable for industrial production. The Q460qE steel plate produced by the present invention has high strength, good impact toughness, excellent forming performance and welding performance. The low-temperature impact energy at -40 °C is stably controlled above 150 J, and the mechanical properties and process properties meet the technical requirements of users.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] For a Q460qE high-strength steel plate with a thickness of 10 - 50 mm and excellent low-temperature impact toughness of the present invention, the mass percentage content of its chemical components is: C: 0.09% - 0.11%, Si: 0.20% - 0.30%, Mn: 1.50% - 1.70%, P: ≤0.010%, S ≤0.005%, Alt: 0.020% - 0.035%, Nb: 0.035% - 0.045%, Ti: 0.010% - 0.020%, V: 0.035% - 0.045%, Cr: 0.10% - 0.20%, and the rest is Fe and inevitable impurities.

[0006] Further, the mass percentage content of its chemical components is: C: 0.09%, Si: 0.24%, Mn: 1.56%, P: 0.009%, S: 0.002%, Alt: 0.031%, Nb: 0.036%, Ti: 0.014%, V: 0.035%, Cr: 0.15%, and the rest is Fe and inevitable impurities.

[0007] Furthermore, the mass percentage content of its chemical components is as follows: C: 0.09%, Si: 0.25%, Mn: 1.55%, P: 0.009%, S: 0.004%, Alt: 0.027%, Nb: 0.038%, Ti: 0.016%, V: 0.037%, Cr: 0.20%, and the rest is Fe and inevitable impurities.

[0008] Furthermore, the mass percentage content of its chemical components is as follows: C: 0.11%, Si: 0.25%, Mn: 1.60%, P: 0.010%, S: 0.001%, Alt: 0.029%, Nb: 0.040%, Ti: 0.017%, V: 0.040%, Cr: 0.16%, and the rest is Fe and inevitable impurities.

[0009] Furthermore, the mass percentage content of its chemical components is as follows: C: 0.10%, Si: 0.26%, Mn: 1.56%, P: 0.008%, S: 0.005%, Alt: 0.035%, Nb: 0.036%, Ti: 0.015%, V: 0.035%, Cr: 0.18%, and the rest is Fe and inevitable impurities.

[0010] A production method of Q460qE high-strength steel plate with excellent low-temperature impact toughness and a thickness of 10 - 50 mm, the main process parameters include:

[0011] The first step: the smelting - continuous casting production process flow, KR desulfurization - converter - LF refining - RH vacuum treatment - slab continuous casting - slow cooling; where:

[0012] (1) After the hot metal pretreatment, the S content ≤ 0.005%, and slag must be skimmed after desulfurization to ensure that the hot metal carries less slag;

[0013] (2) Use self-produced low-sulfur scrap steel, the converter end point hits once or the number of additional blows does not exceed once, and the tapping temperature ≥ 1610 °C;

[0014] (3) LF refining carries out slag-making desulfurization, composition adjustment and temperature-raising operations according to the composition and temperature of the converter molten steel, so that the composition and temperature of the molten steel meet the requirements of RH and continuous casting;

[0015] (4) The RH vacuum treatment time ≥ 20 min. After the RH vacuum treatment ends, adjust the argon flow rate to make the molten steel in a soft blowing state, feed calcium wire for calcium treatment, the [Ca] of the molten steel after wire feeding is 0.0008 - 0.0025%, and ensure that the soft blowing time ≥ 10 min after wire feeding;

[0016] (5) The target superheat degree in the continuous casting process is 20 - 30 °C. The whole process is protected by pouring, electromagnetic stirring and soft reduction are adopted, the casting speed is controlled at 0.8 - 1.1 m / min to ensure the quality of the continuous casting billet. The continuous casting billet is slowly cooled in a heat preservation pit, and the slow cooling time is ≥ 48 hours;

[0017] The second step: the slab is heated in the furnace; strictly control the residence time, soaking time and tapping temperature of the slab in the furnace. The residence time in the furnace is ≥ 220 min, the soaking time is 30 - 60 min, and the tapping temperature is 1230 ± 20 °C;

[0018] The third step: the slab is rolled, specifically including rough rolling and finish rolling; among them:

[0019] (1) Rough rolling: After the billet is taken out of the furnace, it is quickly sent to the descaling machine to remove the scale. The rough rolling is completed with as few passes as possible for width spreading. The rough rolling starting temperature is ≥ 1150 °C, and the rough rolling final thickness is 2 - 4 times the finished product;

[0020] (2) Finish rolling: After rough rolling, the slab is kept at a certain temperature, rolled avoiding part of the recrystallization zone to avoid mixed grains. The finish rolling starting temperature is ≤ 950 °C, and the finish rolling final temperature is 780 °C - 820 °C;

[0021] The fourth step: laminar cooling. The cooling mode of the rolled steel plate adopts the laminar cooling of the self - learning calculation results of the secondary system; the final cooling temperature is 595 °C - 665 °C;

[0022] The fifth step: straightening the steel plate, which is straightened according to the thickness specification of the steel plate and the actual shape of the cold - rolled steel plate.

[0023] Furthermore, the Q460qE steel plate produced by the present invention has high strength, good impact toughness, excellent forming performance and welding performance. Especially, the low - temperature impact energy at - 40 °C can be stably controlled above 150 J.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are:

[0025] The Q460qE steel plate produced by the present invention has high strength, good impact toughness, excellent forming performance and welding performance. The low - temperature impact energy at - 40 °C is stably controlled above 150 J, and the mechanical properties and process properties meet the technical requirements of users. At the same time, the operation method of the present invention is simple and suitable for industrial production. Description of the Drawings

[0026] The present invention will be further described below in conjunction with the description of the drawings.

[0027] Figure 1 It is the microstructure diagram of the steel plate in Embodiment 2 of the present invention. Detailed Embodiments

[0028] The present invention will be described in more detail below through specific embodiments. The embodiments are only descriptions of the best implementation modes of the present invention and do not limit the scope of the present invention in any way.

[0029] Example 1

[0030] The hot metal is subjected to desulfurization pretreatment, and the top-bottom combined blowing converter is used for smelting to decarbonize and dephosphorize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1630 °C. Then, the molten steel after converter smelting is subjected to LF secondary refining, and the in-position refining temperature is ≥1561 °C. After LF secondary refining, the molten steel is subjected to RH vacuum treatment, and the vacuum holding time is 22 min. Slab continuous casting is carried out according to the smelting chemical composition shown in Table 1, with a superheat of 25 °C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1220 °C, the heating time is 245 min, and the soaking time is 60 min. The heated slab is subjected to high-pressure water descaling. After descaling, rolling is carried out. Both rough rolling and finish rolling use two-high reversing mills. The rough rolling starting temperature is 1165 °C. When rolling to the thickness of the intermediate billet, it is kept at a certain temperature. The average starting temperature of finish rolling is 930 °C, and the average final rolling temperature of finish rolling is 810 °C. The final cooling temperature of the steel plate after laminar cooling is 640 °C, and the finished product thickness is 14.0 mm. Then, straightening is carried out. Finally, samples are taken according to the standard for product quality inspection.

[0031] Example 2

[0032] The hot metal is subjected to desulfurization pretreatment, and the top-bottom combined blowing converter is used for smelting to decarbonize and dephosphorize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1640 °C. Then, the molten steel after converter smelting is subjected to LF secondary refining, and the in-position refining temperature is ≥1556 °C. After LF secondary refining, the molten steel is subjected to RH vacuum treatment, and the vacuum holding time is 24 min. Slab continuous casting is carried out according to the smelting chemical composition shown in Table 1, with a superheat of 27 °C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1230 °C, the heating time is 245 min, and the soaking time is 505 min. The heated slab is subjected to high-pressure water descaling. After descaling, rolling is carried out. Both rough rolling and finish rolling use two-high reversing mills. The rough rolling starting temperature is 1185 °C. When rolling to the thickness of the intermediate billet, it is kept at a certain temperature. The average starting temperature of finish rolling is 915 °C, and the average final rolling temperature of finish rolling is 800 °C. The final cooling temperature of the steel plate after laminar cooling is 635 °C, and the finished product thickness is 28.0 mm. Then, straightening is carried out. Finally, samples are taken according to the standard for product quality inspection.

[0033] Example 3

[0034] The hot metal is subjected to desulfurization pretreatment. The top and bottom combined blowing converter is used for smelting to decarbonize and dephosphorize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process. Scrap steel is added to the converter, and the tapping temperature of the converter is 1641°C. Then, the molten steel after converter smelting is subjected to LF secondary refining, and the refining in-position temperature is ≥1563°C. The molten steel after LF secondary refining is subjected to RH vacuum treatment, and the vacuum holding time is 20 min. Slab continuous casting is carried out according to the smelting chemical composition shown in Table 1, with a superheat of 25°C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1227°C, the heating time is 231 min, and the soaking time is 55 min. The heated slab is subjected to high-pressure water descaling. After descaling, rolling is carried out. Both rough rolling and finish rolling use two-high reversing mills. The rough rolling starting temperature is 1185°C. When rolling to the thickness of the intermediate billet, it is held at a certain temperature. The average finish rolling starting temperature is 900°C, and the average finish rolling temperature is 785°C. The final cooling temperature of the steel plate after laminar cooling is 620°C, and the finished product thickness is 40.0 mm. Then, straightening is carried out. Finally, samples are taken according to the standard for product quality inspection.

[0035] Example 4

[0036] The hot metal is subjected to desulfurization pretreatment. The top and bottom combined blowing converter is used for smelting to decarbonize and dephosphorize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process. Scrap steel is added to the converter, and the tapping temperature of the converter is 1645°C. Then, the molten steel after converter smelting is subjected to LF secondary refining, and the refining in-position temperature is ≥1560°C. The molten steel after LF secondary refining is subjected to RH vacuum treatment, and the vacuum holding time is 20 min. Slab continuous casting is carried out according to the smelting chemical composition shown in Table 1, with a superheat of 23°C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1225°C, the heating time is 230 min, and the soaking time is 45 min. The heated slab is subjected to high-pressure water descaling. After descaling, rolling is carried out. Both rough rolling and finish rolling use two-high reversing mills. The rough rolling starting temperature is 1180°C. When rolling to the thickness of the intermediate billet, it is held at a certain temperature. The average finish rolling starting temperature is 890°C, and the average finish rolling temperature is 780°C. The final cooling temperature of the steel plate after laminar cooling is 600°C, and the finished product thickness is 50.0 mm. Then, straightening is carried out. Finally, samples are taken according to the standard for product quality inspection.

[0037] The chemical compositions of Examples 1 to 4 of the Q460qE high-strength steel plate with a thickness of 10 - 50 mm according to the present invention are shown in Table 1, and the mechanical property test values of the examples are shown in Table 2. It can be seen that the mechanical properties of the examples of the present invention are stable with small fluctuations, and the low-temperature impact toughness value is stably controlled above 150 J. It should be noted that all similar changes directly derived or associated by those skilled in the art from the content disclosed in the present invention shall fall within the protection scope of the present invention.

[0038] Table 1 Chemical Compositions (wt%) of Examples 1 to 4 of the Present Invention

[0039]

[0040] Table 2 Mechanical properties and process properties of Examples 1 to 4 of the present invention

[0041]

[0042]

[0043] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A Q460qE high-strength steel plate with a thickness of 10-50 mm and excellent low-temperature impact toughness, characterized in that: The mass percentage of its chemical composition is C: 0.09%-0.11%, Si: 0.20%-0.30%, Mn: 1.50%-1.70%, P: ≤0.010%, S≤0.005%, Alt: 0.020%-0.035%, Nb: 0.035%-0.045%, Ti: 0.010%-0.020%, V: 0.035%-0.045%, Cr: 0.10%-0.20%, and the rest is Fe and unavoidable impurities.

2. The Q460qE high-strength steel plate with a thickness of 10-50 mm and excellent low-temperature impact toughness according to claim 1, characterized in that: The mass percentage of its chemical composition is C: 0.09%, Si: 0.24%, Mn: 1.56%, P: 0.009%, S: 0.002%, Alt: 0.031%, Nb: 0.036%, Ti: 0.014%, V: 0.035%, Cr: 0.15%, and the rest is Fe and unavoidable impurities.

3. The Q460qE high-strength steel plate with a thickness of 10-50 mm and excellent low-temperature impact toughness according to claim 1, characterized in that: The mass percentage of its chemical composition is C: 0.09%, Si: 0.25%, Mn: 1.55%, P: 0.009%, S: 0.004%, Alt: 0.027%, Nb: 0.038%, Ti: 0.016%, V: 0.037%, Cr: 0.20%, and the rest is Fe and unavoidable impurities.

4. The Q460qE high-strength steel plate with a thickness of 10-50 mm and excellent low-temperature impact toughness according to claim 1, characterized in that: The mass percentage of its chemical composition is C: 0.11%, Si: 0.25%, Mn: 1.60%, P: 0.010%, S: 0.001%, Alt: 0.029%, Nb: 0.040%, Ti: 0.017%, V: 0.040%, Cr: 0.16%, and the rest is Fe and unavoidable impurities.

5. The Q460qE high-strength steel plate with a thickness of 10-50 mm and excellent low-temperature impact toughness according to claim 1, characterized in that: The mass percentage of its chemical composition is C: 0.10%, Si: 0.26%, Mn: 1.56%, P: 0.008%, S: 0.005%, Alt: 0.035%, Nb: 0.036%, Ti: 0.015%, V: 0.035%, Cr: 0.18%, and the rest is Fe and unavoidable impurities.

6. The method for producing a Q460qE high-strength steel plate with a thickness of 10-50 mm and excellent low-temperature impact toughness according to any one of claims 1 to 5, characterized in that: The main process parameters include: 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℃; The third step: 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 ≥1150℃, and the final thickness of the rough rolling is 2-4 times that of the finished product; (2) Finishing rolling: After rough rolling, the slab is kept warm, rolling is carried out away from the recrystallization zone to avoid mixed crystals. The starting temperature of finishing rolling is ≤950°C, and the final rolling temperature of finishing rolling is 780°C-820°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 595℃-665℃; 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.

7. The production method according to claim 6, characterized in that: The Q460qE steel plate produced by the present invention has high strength, good impact toughness, excellent forming performance and welding performance, especially the low-temperature impact energy of -40°C can be stably controlled to be above 150J.

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