Production method for optimizing impact performance of thick E ship plate

Abstract

The invention discloses a production method for optimizing impact performance of a thick E ship plate, which comprises the following chemical components in percentage by mass: 0.06-0.09% of C, 0.15-0.23% of Si, 1.5-1.6% of Mn, 0.020-0.05% of Al, 0.010-0.02% of Ti, 0.020-0.030% of Nb, less than or equal to 0.02% of P, less than or equal to 0.003% of S, less than or equal to 0.006% of N and the balance of iron and inevitable impurity elements, and the carbon equivalent Ceq in the steel plate is controlled to be less than or equal to 0.36%. Wherein Ceq = [C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15]. The rolling reduction in the rough rolling process is strictly controlled, meanwhile, the structure is promoted to be further refined through the ACC technology, a uniform structure with ferrite and pearlite as main components is obtained, the performance uniformity is guaranteed, and therefore good obdurability and impact resistance are obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgy, and particularly relates to a production method for optimizing impact performance of thick-specification E ship plate. BACKGROUND

[0002] With the rapid development of shipping industry in China and in the world, the demand for ship plates is increasing, and the ship plate has become one of the steel grades that are generally produced in large quantities by domestic steel enterprises. With the increase of shipbuilding capacity and product structure, the capacity of large container ships, drilling ships and other high-value-added ships is continuously improved, the tonnage of the ships is larger and larger, and the ship types are more and more various, and accordingly, the size and thickness requirements for the ship plates are higher and higher.

[0003] In the prior art, the production of the steel plate with a thickness specification less than 60 mm is relatively mature, and the tensile and impact performance of the E plate under the thickness specification is relatively stable. However, the production of the thick steel plate with a thickness specification greater than 80 mm still has deficiencies, and the impact performance is prone to fluctuation, and the-40 DEG C impact is prone to the phenomenon of low single value. Therefore, it is necessary to propose a production method with low cost and capable of ensuring the stable-40 DEG C impact performance of the E plate with a thickness specification greater than 80 mm. SUMMARY

[0004] The present application solves the technical problems of the prior art, and provides a production method for optimizing impact performance of thick-specification E ship plate. The E ship plate provided by the production method for optimizing impact performance of thick-specification E ship plate does not add valuable elements such as V, Cu and Cr, and has the effects of low overall cost and simple production process.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a production method for optimizing impact performance of thick-specification E ship plate, the chemical components are proportioned according to the mass fraction as follows: C: 0.06-0.09%, Si: 0.15-0.23%, Mn: 1.5-1.6%, Al: 0.020-0.05%, Ti: 0.010-0.02%, Nb: 0.020-0.030%, P≤0.02%, S≤0.003%, N≤0.006%, and the rest is iron and inevitable impurity elements, and the carbon equivalent Ceq in the steel plate is controlled to be less than or equal to 0.36%; wherein, Ceq = [C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15].

[0006] Specifically, the method comprises the following steps: S1, proportioning the steel grade components according to the mass percentage.

[0007] S2, desulfurizing the molten iron. The KR stirring method is used for desulfurization treatment, and the S content in the treated molten iron is less than or equal to 0.012%.

[0008] S3, converter smelting.

[0009] S4, LF refining. The LF refining treatment is adopted, and the S content of the treated molten steel is less than or equal to 0.005%; S5, soft stirring. The soft stirring time is 10 minutes. S6, slab continuous casting. In the slab continuous casting stage, the tundish temperature is controlled to be 1540-1560 DEG C, and the casting speed is 0.6-0.7 m / min. S7, reheating and soaking in a heating furnace. In the slab reheating stage, the temperature is controlled to be 1130-1200 DEG C, the soaking temperature is controlled to be 1130-1200 DEG C, and the furnace time is not less than 300 minutes.

[0010] S8, rough rolling. The rough rolling temperature is 1020-1100 DEG C, the rough rolling is carried out with large reduction, the average reduction after the rough rolling is finished is greater than or equal to 28 mm, and the intermediate billet thickness is 155-175 mm. S9, finish rolling. The finish rolling starting temperature is less than or equal to 880 DEG C, and the finish rolling temperature is 750-850 DEG C. S10, steel plate rapid cooling, steel plate hot bending, and cooling on a cooling bed. In the steel plate rapid cooling stage, the final cooling temperature is 600-690 DEG C, and the cooling rate is controlled to be 10+ / -5 DEG C / s. S11, shearing and storage.

[0011] Preferably, S2, hot metal desulfurization; the KR stirring method is adopted for desulfurization treatment, and the S content of the treated hot metal is less than or equal to 0.010%.

[0012] Preferably, S4, LF refining; the LF refining treatment is adopted, and the S content of the treated molten steel is less than or equal to 0.003%.

[0013] Preferably, S8, rough rolling; the rough rolling temperature is 1030-1080 DEG C, the rough rolling is carried out with large reduction, the average reduction after the rough rolling is finished is greater than or equal to 28 mm, and the intermediate billet thickness is 160-170 mm.

[0014] Preferably, S9, finish rolling; the finish rolling starting temperature is less than or equal to 880 DEG C, and the finish rolling temperature is 780-830 DEG C.

[0015] Preferably, S10, steel plate rapid cooling, steel plate hot bending, and cooling on a cooling bed; in the steel plate rapid cooling stage, the final cooling temperature is 650-690 DEG C, and the cooling rate is controlled to be 10+ / -5 DEG C / s.

[0016] Preferably, the E ship plate has a thickness of 80-100 mm, a yield strength greater than or equal to 240 MPa, a tensile strength greater than or equal to 400 MPa, an elongation greater than or equal to 23%, and an impact energy at -40 DEG C greater than or equal to 200 J.

[0017] The present application has the following beneficial effects: 1. This invention strictly controls the reduction during the rough rolling process and simultaneously promotes further microstructure refinement through accelerated cooling control (ACC) technology, obtaining a uniform microstructure dominated by ferrite and pearlite, ensuring uniform performance, and thus achieving good strength, toughness, and impact resistance. The chemical composition of the steel plate does not contain added precious elements such as V, Cu, and Cr; and the carbon equivalent (Ceq) in the E-type ship plate is strictly controlled, with Ceq ≤ 0.36%.

[0018] 2. By controlling the rough rolling start temperature to be limited to 1020-1100℃, the present invention can ensure the austenite recrystallization effect during the rough rolling process and give full play to the fine grain strengthening and solid solution strengthening effects of alloying elements during rolling and cooling. The thickness of the intermediate billet after rough rolling is controlled to be 155-175mm.

[0019] 3. The microstructure obtained by this invention is mainly composed of ferrite and pearlite, which effectively ensures the uniformity of the microstructure in the head, middle and tail of the rolled plate. The method is applicable to steel plates with a thickness of 80-100mm, yield strength ≥240MPa, tensile strength ≥400MPa, elongation ≥23%, and impact energy at -40℃ ≥200J. The mechanical properties meet the requirements of E-level steel plates in classification societies such as ABS and CCS. Detailed Implementation

[0020] A production method for optimizing the impact performance of thick E-grade ship plates, wherein the chemical composition is formulated by mass fraction as follows: C: 0.06-0.09%, Si: 0.15-0.23%, Mn: 1.5-1.6%, Al: 0.02-0.05%, Ti: 0.01-0.02%, Nb: 0.02-0.03%, P≤0.02%, S≤0.003%, N≤0.006%, with the remainder being iron and unavoidable impurity elements, and Ceq≤0.36% controlled; wherein, Ceq=[C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15].

[0021] Among them, C: 0.06~0.09%. Carbon is an indispensable strengthening element in steel. It can significantly improve the strength of steel through solid solution strengthening. However, the increase of carbon content will reduce the low-temperature impact toughness of steel and affect the weldability of steel plates. Therefore, the range of 0.06~0.09% is appropriate.

[0022] The Si content is 0.15–0.23%. Si is added for deoxidation. However, if the addition exceeds 0.40%, the toughness of the base material and the weld heat-affected zone decreases significantly; therefore, the Si content is kept below 0.40%. A range of 0.1–0.23% is selected.

[0023] Mn: 1.5-1.6%. Mn is mainly used to improve the strength of the steel plate, and is also a necessary deoxidizer and reducing agent. If the amount of addition exceeds 5.0%, not only the toughness of the base material deteriorates, but also the central segregation is promoted, and the central porosity of the billet is enlarged, so it is appropriate to be in the range of 1.60-1.70%.

[0024] Al: 0.02-0.05%, Al is used in steel as a deoxidizer and a grain refining element. Adding an appropriate amount of Al can refine the grain and improve the strength and toughness of the steel. However, excessive Al will reduce the toughness of the steel plate. Therefore, Al is appropriate to be in the range of 0.02-0.05%.

[0025] Ti: 0.01-0.02%, Ti can refine the grain and improve the strength and toughness of the steel plate. However, if the content of Ti is too high, the toughness of the steel plate will be reduced, so it is appropriate to be in the range of 0.01-0.02%.

[0026] Nb: 0.02-0.03%, a small amount of Nb can promote ferrite nucleation, refine the grain, and improve the strength and toughness of the steel.

[0027] P, S: P≤0.02%, S≤0.003%. Phosphorus and sulfur are harmful elements in steel. Sulfur exists in the form of iron sulfide in steel, and steel is prone to thermal embrittlement during processing, which reduces the ductility and toughness of the steel. Phosphorus in steel can cause segregation, which significantly reduces the low-temperature toughness of the steel, so the content of phosphorus and sulfur in the steel should not be too high.

[0028] Further, the method comprises the following steps: S1, preparing the composition of the steel grade according to the mass percentage.

[0029] S2, desulfurizing the molten iron. KR stirring method is used for desulfurization treatment, and the S content of the treated molten iron is ≤0.012%.

[0030] Preferably, S2, desulfurizing the molten iron; KR stirring method is used for desulfurization treatment, and the S content of the treated molten iron is ≤0.010%.

[0031] S3, converter smelting.

[0032] S4, LF refining. LF refining treatment is used, and the S content of the treated molten steel is ≤0.005%.

[0033] Preferably, S4, LF refining; LF refining treatment is used, and the S content of the treated molten steel is ≤0.003%.

[0034] S5, soft stirring. The soft stirring time is 10 min.

[0035] S6, slab continuous casting. In the slab continuous casting stage, the temperature of the tundish is controlled at 1540-1560 DEG C, and the drawing speed is 0.6-0.7 m / min.

[0036] S7, reheating and soaking in the heating furnace; in the slab reheating stage, the temperature is controlled at 1130-1200 DEG C, the temperature in the soaking section is controlled at 1130-1200 DEG C, and the furnace time is not less than 300 min.

[0037] S8, rough rolling; the rough rolling temperature is 1020-1100 DEG C; rough rolling is carried out with large reduction, and the average reduction after the rough rolling and spreading is greater than or equal to 28 mm, and the intermediate blank thickness is 155-175 mm.

[0038] Preferably, S8, rough rolling; the rough rolling temperature is 1030-1080 DEG C, rough rolling is carried out with large reduction, and the average reduction after the rough rolling and spreading is greater than or equal to 28 mm, and the intermediate blank thickness is 160-170 mm.

[0039] S9, finish rolling; the finish rolling starting temperature is less than or equal to 880 DEG C, and the finish rolling temperature is 750-850 DEG C. Preferably, S9, finish rolling; the finish rolling starting temperature is less than or equal to 880 DEG C, and the finish rolling temperature is 780-830 DEG C.

[0040] S10, rapid cooling of the steel plate, hot bending of the steel plate, and cooling on the cooling bed; in the rapid cooling stage of the steel plate, the final cooling temperature is 600-690 DEG C, and the cooling rate is controlled at 10±5 DEG C / s.

[0041] Ferrite+pearlite is obtained by controlling the final cooling temperature and the ACC cooling rate; the final cooling temperature is controlled at 600-690 DEG C, and the ACC cooling rate is controlled at 10±5 DEG C / s.

[0042] Preferably, S10, rapid cooling of the steel plate, hot bending of the steel plate, and cooling on the cooling bed; in the rapid cooling stage of the steel plate, the final cooling temperature is 650-690 DEG C, and the cooling rate is controlled at 10±5 DEG C / s.

[0043] The present application strictly controls the reduction in the rough rolling process, and promotes further refinement of the structure by the accelerated cooling control (ACC) technology, so that a uniform structure mainly composed of ferrite+pearlite is obtained, the uniformity of the performance is ensured, and good strength, toughness and impact resistance are obtained.

[0044] The application can ensure austenite recrystallization effect in rough rolling process by controlling rough rolling starting temperature to be limited in 1020-1100 DEG C, and can fully exert the effects of fine-grain strengthening and solid solution strengthening of alloy elements in rolling and cooling process, and the thickness of the intermediate blank after rough rolling is controlled in 155-175 mm.

[0045] S11, shearing and warehousing.

[0046] The obtained tissue is mainly ferrite+pearlite, which effectively ensures the uniformity of the head, middle and tail of the rolled plate, and the method is suitable for a steel plate with a thickness of 80-100 mm, a yield strength of ≥240 MPa, a tensile strength of ≥400 MPa, an elongation of ≥23%, and an impact energy at-40 DEG C of ≥200 J, and the mechanical properties meet the requirements of ABS, CCS and other ship classification societies in the E grade. Example 1

[0047] In the embodiment, the E steel plate has a thickness of 100 mm, and the chemical components are proportioned as follows in mass fraction: C: 0.06%, Si: 0.18%, Mn: 1.53%, Al: 0.037%, Ti: 0.014%, Cr: 0.03%, P: 0.018%, S: 0.002%, N: 0.0029%, and the rest is iron and inevitable impurity elements, wherein Ceq: 0.33%.

[0048] The production method comprises the following steps: proportioning steel grade components, desulfurizing molten iron, converter smelting, LF refining, soft stirring, slab continuous casting, reheating and soaking in a heating furnace, rough rolling, finish rolling, rapid cooling of the steel plate, hot straightening, cooling on a cooling bed, shearing and warehousing, wherein the S content of the molten iron after desulfurization treatment is 0.006%; the S content of the molten steel after LF refining treatment is 0.002%; the soft stirring time is 10 min; the tundish temperature is controlled in 1552 DEG C, the withdrawal speed is 0.6-0.7 m / min; the slab reheating stage temperature is controlled in 1180 DEG C, the soaking stage temperature is controlled in 1150 DEG C, the furnace time is not less than 300 min, the rough rolling temperature is 1050 DEG C, the rough rolling is carried out by using large reduction, the rough rolling is carried out for 5 passes with an average reduction of 32 mm, the intermediate waiting thickness is 160 mm, the finish rolling starting temperature is ≤880 DEG C, the finish rolling temperature is 768 DEG C, the final cooling temperature of the steel plate rapid cooling stage is 660 DEG C, and the cooling rate is controlled in 9 DEG C / s. Example 2

[0049] In the embodiment, the E steel plate has a thickness of 80 mm, and the chemical components are proportioned as follows in mass fraction: C: 0.06%, Si: 0.17%, Mn: 1.55%, Al: 0.035%, Ti: 0.014%, Cr: 0.03%, P: 0.019%, S: 0.002%, N: 0.0031%, and the rest is iron and inevitable impurity elements, wherein Ceq: 0.33%.

[0050] The production method has the following steps: proportioning steel components in mass percentage, desulfurization of molten iron, converter smelting, LF refining, soft stirring, slab continuous casting, reheating and soaking in a heating furnace, rough rolling, finish rolling, rapid cooling of the steel plate, hot straightening, cooling on a cooling bed, shearing, and warehousing. After desulfurization treatment, the S content of the molten iron is 0.006%; after LF refining treatment, the S content of the molten steel is 0.002%; the soft stirring time is 10 min; the tundish temperature is controlled at 1558℃, and the drawing speed is 0.6-0.7 m / min; in the slab reheating stage, the temperature is controlled at 1185℃, the soaking temperature is controlled at 1160℃, the furnace time is not less than 300 min, the rough rolling temperature is 1045℃, the rough rolling is performed with large reduction, the rough rolling is performed for 5 passes with an average reduction of 32 mm, the intermediate temperature is 160 mm, the finish rolling starting temperature is ≤880℃, the finish rolling temperature is 798℃, in the rapid cooling stage of the steel plate, the final cooling temperature is 663℃, and the cooling rate is controlled at 10℃ / s. Example 3

[0051] In the embodiment, the E steel plate has a thickness of 80 mm, and the chemical components are proportioned as follows in mass fraction: C: 0.07%, Si: 0.18%, Mn: 1.56%, Al: 0.034%, Ti: 0.015%, Cr: 0.03%, P: 0.016%, S: 0.002%, N: 0.0024%, and the rest is iron and inevitable impurity elements, wherein Ceq: 0.34%.

[0052] The production method comprises the following steps: preparing the steel grade components by mass percentage, desulphurization of molten iron, converter smelting, LF refining, soft stirring, slab continuous casting, reheating and soaking in a heating furnace, rough rolling, finish rolling, fast cooling of the steel plate, hot straightening, cooling on a cooling bed, shearing and warehousing. After the desulphurization treatment, the S content of the molten iron is 0.006%; after the LF refining treatment, the S content of the molten steel is 0.002%; the soft stirring time is 10 min; the tundish temperature is controlled at 1552℃, the drawing speed is 0.6-0.7 m / min; the slab reheating stage temperature is controlled at 1170℃, the soaking stage temperature is controlled at 1140℃, the furnace time is not less than 300 min, the rough rolling temperature is 1060℃, the rough rolling is performed by using large reduction, the rough rolling is performed for 5 passes with an average reduction of 28 mm, the intermediate temperature is 160 mm, the finish rolling starting temperature is ≤880℃, the finish rolling final temperature is 776℃, the fast cooling stage final cooling temperature of the steel plate is 650℃, and the cooling rate is controlled at 10℃ / s.

[0053] The chemical component mass percentage of the E ship plate in Examples 1-3 is shown in Table 1, and the mechanical properties of the E ship plate in Examples 1-3 are shown in Table 2.

[0054] Table 1: Chemical component mass percentage of the E ship plate in Examples 1-3 In the formula, the small amount of Ni, Cu, Mo and B are impurities.

[0055] Table 2: Mechanical properties of the E ship plate in Examples 1-3 As shown in the table, the E ship plate produced by using the chemical component mass percentage and the production process steps in Examples 1-3 can meet the performance requirements of the 80-100 mm E ship plate.

[0056] The technical features of the above-described embodiments can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict, they should be considered as falling within the scope of the present disclosure.

[0057] The preferred embodiments of the present application have been described in detail above, but the present application is not limited to the specific details of the above-described embodiments, and various equivalent modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these equivalent modifications all fall within the protection scope of the present application.

Claims

1. A method of producing a thick gauge E-ship plate with optimized impact performance, characterized by: The chemical composition is proportioned as follows in mass fraction: C: 0.06-0.09%, Si: 0.15-0.23%, Mn: 1.5-1.6%, Al: 0.020-0.05%, Ti: 0.010-0.02%, Nb: 0.020-0.030%, P ≤0.02%, S ≤0.003%, N ≤0.006%, and the rest is iron and inevitable impurity elements, and the carbon equivalent Ceq in the steel plate is controlled to be ≤0.36%. Ceq = [C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15].

2. The method of producing a thick-gauge E-ship plate optimized for impact performance according to claim 1, characterized in that: The method comprises the following steps: S1, proportioning the steel grade components in mass percentage; S2, desulfurization of molten iron; KR stirring method is adopted for desulfurization treatment, and the S content of the treated molten iron is ≤0.012%; S3, converter smelting; S4, LF refining; LF refining treatment is adopted, and the S content of the treated molten steel is ≤0.005%; S5, soft stirring; The soft stirring time is 10 min; S6, slab continuous casting; In the slab continuous casting stage, the tundish temperature is controlled to be 1540-1560℃, and the pulling speed is 0.6-0.7 m / min; S7, reheating and soaking in a heating furnace; In the slab reheating stage, the temperature is controlled to be 1130-1200℃, the soaking segment temperature is controlled to be 1130-1200℃, and the furnace time is not less than 300 min; S8, rough rolling; The rough rolling temperature is 1020-1100℃, and the rough rolling is carried out with large reduction, the average reduction of the passes after the rough rolling widening is ≥28 mm, and the intermediate billet thickness is 155-175 mm; S9, finish rolling; The finish rolling starting temperature is ≤880℃, and the finish rolling temperature is 750-850℃; S10, rapid cooling of the steel plate, hot bending of the steel plate, and cooling on a cooling bed; In the rapid cooling stage of the steel plate, the final cooling temperature is 600-690℃, and the cooling rate is controlled to be 10±5℃ / s; S11, shearing and storage.

3. The method of producing a thick-gauge E-ship plate optimized for impact performance according to claim 2, characterized in that: S2, desulfurization of molten iron; KR stirring method is adopted for desulfurization treatment, and the S content of the treated molten iron is ≤0.010%.

4. The method of producing thick-gauge E-ship plate optimized for impact performance of claim 2, wherein: S4, LF refining; LF refining treatment is adopted, and the S content of the treated molten steel is ≤0.003%.

5. The method of producing thick-gauge E-ship plates with optimized impact properties according to claim 2, characterized in that: S8, rough rolling; the rough rolling temperature is 1030-1080℃, and the rough rolling is carried out with large reduction, the average reduction of the passes after the rough rolling widening is ≥28 mm, and the intermediate billet thickness is 160-170 mm.

6. The method of producing thick-gauge E-ship plate with optimized impact performance of claim 2, wherein: S9, finish rolling; the finish rolling starting temperature is ≤880℃, and the finish rolling temperature is 780-830℃.

7. The method of producing thick-gauge E-ship plates with optimized impact properties according to claim 2, characterized in that: S10, rapid cooling of the steel plate, hot bending of the steel plate, and cooling on a cooling bed; in the rapid cooling stage of the steel plate, the final cooling temperature is 650-690℃, and the cooling rate is controlled to be 10±5℃ / s.

8. The method of producing thick-gauge E-ship plates with optimized impact properties according to claim 2, characterized in that: The E ship plate has a thickness of 80-100 mm, a yield strength of ≥240 MPa, a tensile strength of ≥400 MPa, an elongation of ≥23%, and an impact energy at -40℃ of ≥200 J.

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