Steel plate for lightweight mobile tank pressure vessel and production method

Abstract

The invention discloses a steel plate for a lightweight mobile tank pressure vessel. The steel plate is characterized by comprising the following chemical components in percentage by mass: 0.15 to 0.19 percent of C, 0.20 to 0.40 percent of Si, 1.40 to 1.70 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.40 to 0.70 percent of Ni, 0.015 to 0.035 percent of Nb, 0.15 to 0.20 percent of V, 0.012 to 0.018 percent of N and the balance of Fe and inevitable impurities. The production method comprises the steps of smelting, continuous casting, high-temperature heating, rolling and heat treatment, the carbon steel plate for the pressure vessel can meet the requirements that the transverse impact at-40 DEG C in the delivery state and the PWHT state is larger than or equal to 60 / 60 J, the yield strength is larger than or equal to 460 MPa, the tensile strength is 630-730 MPa, and the ductility is larger than or equal to 18%, and the market competitiveness of the steel plate for the south steel mobile tank pressure vessel is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of light weight mobile tank pressure vessel steel plate and production method. BACKGROUND

[0002] At present, mobile tank pressure vessel steel plate is mostly low alloy high strength steel, which realizes the matching of strength and toughness by adding alloy elements such as Mn, Si, Nb and V and cooperating with controlled rolling process. However, the existing steel plate still has the following problems in the balance of lightweight and comprehensive performance: Some steel plates increase carbon content or alloy element addition amount to pursue high strength, resulting in a decrease in low temperature toughness, especially impact energy is difficult to meet the requirements in severe environment such as -40℃, increasing the risk of container brittle fracture; Too high carbon equivalent (Ceq) will cause hardening of the heat affected zone (HAZ) of welding, which is prone to welding cracks and needs to be compensated by complex pre-welding preheating or post-welding heat treatment (PWHT), increasing production cost; The yield strength of the existing steel plate is mostly concentrated in the 450MPa level, and if higher pressure grade requirements are to be met, the thickness of the steel plate needs to be increased, making it difficult to achieve lightweight design of the container; Some production processes are highly sensitive to composition control, rolling temperature and cooling speed, resulting in large fluctuations in steel plate performance, especially after PWHT treatment, the strength and toughness are prone to significant decay, affecting product consistency. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a lightweight mobile tank pressure vessel steel plate and production method, which can meet the requirements of -40℃ transverse impact ≥60 / 60J, yield strength ≥460MPa, tensile strength 630-730MPa and elongation ≥18% for carbon steel plate for pressure vessels in delivery state and PWHT state, greatly improving the competitiveness of Nangang mobile tank pressure vessel steel plate in the market.

[0004] To solve the above technical problems, the technical scheme of the present application is as follows: A lightweight mobile tank pressure vessel steel plate, the chemical composition and mass percentage of the steel plate are as follows: C: 0.15-0.19%, Si: 0.20-0.40%, Mn: 1.40-1.70%, P≤0.015%, S≤0.005%, Ni: 0.40-0.70%, Nb: 0.015-0.035%, V: 0.15-0.20%, N: 0.012-0.018%, the balance being Fe and unavoidable impurities.

[0005] The steel sheet has a yield strength of 500-540 MPa, a tensile strength of 650-670 MPa, an elongation of >22%, and an average transverse impact energy at -40℃ of >100 J.

[0006] The application provides a method for producing a light-weight steel sheet for a mobile tank pressure container, which comprises smelting, continuous casting, high-temperature heating, rolling and heat treatment processes, and specifically comprises the following steps: S1 smelting: through molten iron desulfurization pretreatment, converter smelting, LF refining and RH vacuum treatment; S2 continuous casting: casting is performed by using an arc-shaped continuous casting machine, the liquidus temperature of the tundish molten steel is detected before continuous casting, the tundish molten steel superheat degree is controlled to be ≤15℃, the cast blank obtained through continuous casting is subjected to macroscopic detection, the macroscopic rating is C1.5, and the cast blank thickness is 220 mm; S3 heating: 220 mm thick continuous casting blank is used, the total furnace time is 8-16 min / cm, the soaking time is ≥1.5 min / cm, and the tapping temperature is 1180-1220℃; S4 rolling: two-stage temperature control rolling is used, and air cooling is performed after rolling; S5 heat treatment process: the steel sheet is heated to 900-920℃ for normalizing heat treatment, the normalizing time is controlled to be (1.3-1.8) min / mm×H (steel sheet thickness) + (15-30) min, and air cooling is performed to room temperature after tapping.

[0007] Preferably, in S1, the sulfur content is controlled to be ≤0.002% after the molten iron desulfurization treatment, and the slag is cleaned; the converter adopts a double-slag method to strictly control the P content to be ≤0.015%; the LF refining adopts white slag operation for desulfurization and deoxidization; the RH vacuum treatment has a vacuum degree of ≤3.0 mbar and a vacuum time of ≥15 minutes; after the vacuum ends, high-silicon nitride cored wire is fed at 550±50 meters / furnace to increase nitrogen, seamless pure calcium wire is fed at 190±10 meters / furnace after the composition meets the internal control requirements, and the static stirring time is ≥15 min after the wire feeding ends.

[0008] Preferably, in S3, the heating adopts segmented heating, which is divided into a preheating section, a heating section and a soaking section, the total furnace time is 8-16 min / cm, the soaking section temperature is set to be 1200±20℃, and the soaking time is ≥1.5 min / cm; the tapping temperature after heating is controlled to be 1180-1220℃.

[0009] Preferably, in S4, the rolling process adopts a two-stage temperature control rolling process, the first stage is a rough rolling stage, and the 220 mm thick cast blank is rolled to an intermediate blank thickness, the intermediate blank thickness is set according to the finished product thickness; the second stage is a finish rolling stage, the two-stage rolling temperature is ≤940℃, and the final rolling temperature is ≤840℃.

[0010] Preferably, the steel plate is subjected to normalizing heat treatment, and the microstructure at 1 / 4 thickness mainly consists of ferrite, pearlite and bainite, and the grains are uniform and fine, and the grain size meets the uniformity requirement of subsequent mechanical properties The beneficial effects of the present application are: The present application significantly improves low-temperature toughness while ensuring strength by adding a lower C content in combination with Ni element, and the synergistic effect of V and N forms VN precipitates, achieving precipitation strengthening while avoiding the decline of welding performance caused by excessive carbon content, solving the traditional low-alloy steel "strength-toughness-weldability" triangular contradiction; by adopting high-temperature heating, two-stage temperature control rolling, air cooling after rolling and appropriate normalizing process, a light-weight mobile tank pressure container steel plate with a yield strength of 500-540 MPa, a tensile strength of 650-670 MPa, an elongation of >22%, and an average value of transverse impact energy at -40℃ of >100J is developed in delivery state and PWHT state, greatly improving the competitiveness of Nangang mobile tank pressure container steel plate in the market. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The microstructure morphology at 1 / 4 thickness of the 14.6mm thick steel plate of the present application. DETAILED DESCRIPTION

[0012] In order to make the content of the present application more easily understood, the present application will be further described in detail according to the specific embodiments.

[0013] The present embodiment provides a light-weight mobile tank pressure container steel plate, and the chemical composition and mass percentage of the steel plate are as follows: C: 0.15-0.19%, Si: 0.20-0.40%, Mn: 1.40-1.70%, P≤0.015%, S≤0.005%, Ni: 0.40-0.70%, Nb: 0.015-0.035%, V: 0.15-0.20%, N: 0.012-0.018%, and the balance is Fe and inevitable impurities.

[0014] The yield strength of the above-mentioned steel plate is 500-540MPa, the tensile strength is 650-670MPa, the elongation is >22%, and the average value of transverse impact energy at -40℃ is >100J.

[0015] The present embodiment provides a generation method of a light-weight mobile tank pressure container steel plate, which comprises the following steps of smelting, continuous casting, high-temperature heating, rolling and heat treatment process. S1 smelting: after the pretreatment of molten iron desulfurization, converter smelting, LF refining and RH vacuum treatment, the sulfur content is controlled to be ≤0.002% after the pretreatment of molten iron desulfurization, and the slag is cleaned; the converter adopts double slag method to strictly control the content of P to be ≤0.015%; the LF refining adopts white slag operation to desulfurize and deoxidize; the RH vacuum treatment has a vacuum degree of ≤3.0 mbar and a vacuum time of ≥15 minutes; after the vacuum ends, high silicon nitride cored wire is fed at 550±50 meters / furnace to increase nitrogen, and after the composition meets the internal control requirements, seamless pure calcium wire is fed at 190±10 meters / furnace, and the static stirring time is ≥15 min after the wire feeding ends; S2 continuous casting: an arc-shaped continuous casting machine is used for casting, the liquidus temperature of the tundish molten steel is detected before continuous casting, and the tundish molten steel superheat is controlled to be ≤15℃, the casting blank obtained by continuous casting is detected by macro examination, and the macro examination rating is C1.5, and the casting blank thickness is 220mm; S3 heating: a 220mm thick continuous casting blank is used, and the blank is heated in sections, including a preheating section, a heating section and a soaking section, and the total furnace time is 8-16 min / cm, wherein the soaking section temperature is set to 1200±20℃, and the soaking time is ≥1.5 min / cm; the temperature of the molten steel after heating is controlled to be 1180-1220℃; S4 rolling: a two-stage temperature control rolling process is used, the first stage is a rough rolling stage, and the 220mm thick casting blank is rolled to an intermediate blank thickness, and the intermediate blank thickness is set according to the finished product thickness; the second stage is a finishing rolling stage, and the two-stage opening rolling temperature is ≤940℃, and the final rolling temperature is ≤840℃, and the finished steel plate thickness obtained by the rolling process is 14.6mm or 18.2mm, and the rolling ends air cooling; S5 heat treatment process: the steel plate is heated to 900-920℃ for normalizing heat treatment, the normalizing time is controlled to be (1.3-1.8) min / mm×H (steel plate thickness) + (15-30) min, and the steel plate is air cooled to room temperature after being discharged.

[0016] According to the above chemical element composition, mass percentage and production method requirements, three examples are prepared, which are example 1, example 2 and example 3, the composition is shown in table 1, the heating process is shown in table 2, the two-stage temperature control rolling process is shown in table 3, the normalizing heat treatment process is shown in table 4, the mechanical properties of each example are shown in table 5, and the tensile and impact properties of each example after the PWHT process of 540℃ for 60 minutes are shown in table 6.

[0017] Table 1 Chemical composition (%)

[0018] Table 2 Heating process

[0019] Table 3 Two-stage temperature control rolling process

[0020] Table 4 Normalizing heat treatment process

[0021] Table 5 Mechanical properties

[0022] Table 6 Mechanical properties in PWHT state

[0023] From the above, it can be concluded that the steel plate obtained by the embodiment of the present application can satisfy the steel plate for lightweight mobile tank pressure vessels with yield strength of 500-540 MPa, tensile strength of 650-670 MPa, elongation of >22%, and average value of transverse impact energy at -40℃ of >100J.

[0024] In addition to the above embodiments, the present application can also have other implementation manners; any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A steel sheet for a light-weight mobile tank pressure vessel, characterized by: The steel plate has the following chemical components and mass percentages: C: 0.15-0.19%, Si: 0.20-0.40%, Mn: 1.40-1.70%, P≤0.015%, S≤0.005%, Ni: 0.40-0.70%, Nb: 0.015-0.035%, V: 0.15-0.20%, N: 0.012-0.018%, and the balance of Fe and inevitable impurities.

2. The steel plate for a light-weight mobile tank pressure vessel according to claim 1, characterized by: The steel plate has a yield strength of 500-540 MPa, a tensile strength of 650-670 MPa, an elongation of >22%, and an average transverse impact energy at -40℃ of >100 J.

3. The method of producing a steel sheet for a light-weight mobile tank pressure vessel according to claim 1, characterized by: The process includes smelting, continuous casting, high-temperature heating, rolling, and heat treatment, and specifically as follows: S1 smelting: through molten iron desulfurization pretreatment, converter smelting, LF refining, and RH vacuum treatment; S2 continuous casting: casting is performed using an arc-shaped continuous casting machine, the liquidus temperature of the tundish molten steel is detected before continuous casting, the tundish molten steel superheat is controlled to be ≤15℃, the cast blank obtained by continuous casting is subjected to macroscopic detection, and the macroscopic rating is C1.5, and the cast blank thickness is 220 mm; S3 heating: using a 220 mm thick continuous casting blank, the total furnace time is 8-16 min / cm, the soaking time is ≥1.5 min / cm, and the tapping temperature is 1180-1220℃; S4 rolling: two-stage temperature control rolling is used, and air cooling is performed after rolling; S5 heat treatment process: the steel plate is heated to 900-920℃ for normalizing heat treatment, the normalizing time is controlled to be (1.3-1.8) min / mm×H (steel plate thickness) + (15-30) min, and air cooling is performed after tapping to room temperature.

4. The method of producing a steel sheet for a light-weight mobile tank pressure vessel according to claim 3, characterized by: In S1, the sulfur content after molten iron desulfurization treatment is controlled to be ≤0.002%, and the slag is cleaned; the converter uses a double-slag method to strictly control the P content to be ≤0.015%; LF refining uses white slag operation for desulfurization and deoxidization; RH vacuum treatment has a vacuum degree of ≤3.0 mbar and a vacuum time of ≥15 minutes; after vacuum ends, high-silicon nitride cored wire is fed at 550±50 meters / furnace to increase nitrogen, after the composition meets the internal control requirements, seamless pure calcium wire is fed at 190±10 meters / furnace, and the static stirring time is ≥15 min after the wire feeding ends.

5. The method of producing a steel sheet for a light-weight mobile tank pressure vessel according to claim 3, characterized by: In step S3, heating is performed in stages, including a preheating stage, a heating stage, and a soaking stage, and the total furnace time is 8-16 min / cm, wherein the soaking stage temperature is set to 1200±20℃, and the soaking time is ≥1.5 min / cm; the heating after tapping temperature is controlled to be 1180-1220℃.

6. The method of producing a steel sheet for a light-weight mobile tank pressure vessel according to claim 3, characterized by: In step S4, the rolling process uses a two-stage temperature control rolling process, the first stage is a rough rolling stage, and the 220 mm thick cast blank is rolled to an intermediate blank thickness, and the intermediate blank thickness is set according to the finished product thickness; the second stage is a finish rolling stage, and the two-stage rolling temperature is ≤940℃, and the final rolling temperature is ≤840℃.

7. The method of producing a steel sheet for a light-weight mobile tank pressure vessel according to claim 3, characterized by: After the steel plate is subjected to normalizing heat treatment, the microstructure at 1 / 4 thickness mainly consists of ferrite, pearlite, and bainite, and the grains are uniform and small, and the grain size meets the uniformity requirements of subsequent mechanical properties.

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