150mm ultra-thick 09mnndr container steel used in -70 degree celsius environment and preparation method thereof

Abstract

This invention discloses a 150mm ultra-thick 09MnNiDR container steel for use in -70℃ environments and its preparation method. Its chemical composition and mass percentages are as follows: C: 0.08%–0.12%, Mn: 1.5%–1.9%, P≤0.010%, S≤0.005%, Si: 0.35%–0.70%, Ni: 0.5%–0.9%, Mo: 0.02%–0.080%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities. This invention produces a 150mm ultra-thick steel plate suitable for use in -70℃ environments by strictly controlling harmful elements P and S, using low C, adding appropriate Ni, Mo, and Mn alloying elements to match a 460mm thick continuous casting billet, and controlling the rolling and tempering heat treatment processes.

Description

Technical Field

[0001] This invention relates to the field of steel production technology, and in particular to a 150mm ultra-thick 09MnNiDR container steel for use in environments up to -70℃ and its preparation method. Background Technology

[0002] 09MnNiDR steel is a low-temperature pressure vessel steel that requires excellent low-temperature toughness. It is often used in the construction of key parts of equipment in industries such as petroleum, chemical, and boiler, such as heat exchangers, reactors, separators, and boiler drums. With the development of larger equipment, the annual demand for thicker steel plates is increasing.

[0003] Invention patent application number 202110416155.3 describes a high-toughness quasi-sub-temperature quenched 09MnNiDR container steel and its preparation method, which produces steel plates with a thickness of 40-80mm. Patent number CN104451387A discloses an extra-thick 09MnNiDR low-temperature container plate and its production method, using composite slabs for production, producing steel plates with a thickness of 90-120mm. None of these patents cover a method for producing 150mm ultra-thick steel plates. How to produce 150mm steel plates with excellent low-temperature toughness through innovative design of composition and production processes is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment and its preparation method.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A 150mm ultra-thick 09MnNiDR container steel for use in environments with temperatures as low as -70℃ has the following chemical composition and mass percentages: C: 0.08%~0.12%, Mn: 1.5%~1.9%, P≤0.010%, S≤0.005%, Si: 0.35%~0.70%, Ni: 0.5%~0.9%, Mo: 0.02%~0.080%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities.

[0007] As a preferred embodiment of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment as described in this invention, its chemical composition and mass percentage are as follows: C: 0.09%~0.11%, Mn: 1.6%~1.9%, P≤0.008%, S≤0.005%, Si: 0.35%~0.65%, Ni: 0.5%~0.9%, Mo: 0.02%~0.08%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities.

[0008] The present invention also provides a method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment, which includes the following steps in sequence: desulfurization pretreatment - converter smelting - LF refining - RH vacuum treatment - continuous casting - slab stacking cooling - slab heating - controlled rolling - finishing - flaw detection - heat treatment.

[0009] In the continuous casting process, argon blowing protection is used for casting, the casting temperature is 1505~1525℃, the tundish superheat is 5-25℃, the billet pulling speed is 0.50~0.65m / min, a strong cooling process is used, and the billet is pressed down in the last 4 zones, with a casting slab thickness of 460mm.

[0010] As a preferred embodiment of the preparation method of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment as described in this invention, in the slab heating process, the total furnace time of the slab is greater than 10min / cm, and the heating temperature is 1040~1150℃.

[0011] As a preferred embodiment of the preparation method of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment according to the present invention, the controlled rolling process includes a first-stage rolling and a second-stage rolling. The first-stage rolling adopts continuous rolling with a large rolling pass reduction rate, and the second-stage rolling adopts non-recrystallization controlled rolling.

[0012] As a preferred embodiment of the preparation method of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment as described in this invention, the final rolling temperature of the controlled rolling process is less than or equal to 760℃, and the red-heating temperature of the controlled cooling after rolling is 350-450℃.

[0013] As a preferred embodiment of the preparation method of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment as described in this invention, the heat treatment process includes: quenching and tempering the steel plate after shot blasting, with a quenching temperature of 890-930℃ and a total furnace time of 2.0±1min / mm×steel plate thickness / mm, water cooling to room temperature, a tempering temperature of 660-690℃ and a total heating time of 3.25±1min / mm×steel plate thickness / mm, and air cooling to room temperature.

[0014] As a preferred embodiment of the preparation method of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment as described in this invention, the steel plate microstructure of the obtained 09MnNiDR container steel is bainite + ferrite + pearlite, the yield strength is ≥260MPa, the tensile strength is ≥440MPa, the elongation after fracture is ≥23%, and the average impact energy at -70℃ is ≥100J.

[0015] The beneficial effects of this invention are:

[0016] This invention, through the design of a suitable composition, matching a 460mm thick cross-section continuous casting billet, controlled rolling, and tempering heat treatment process, produces a 150mm ultra-thick steel plate suitable for use in -70℃ environments. The microstructure consists of bainite + ferrite + pearlite, with a yield strength ≥260MPa, tensile strength ≥440MPa, elongation after fracture ≥23%, and an average impact energy at -70℃ ≥100J. This invention successfully solves the problem of the thickness effect of high toughness at low temperatures in steel plates, meeting the equipment construction needs of industries such as petroleum, chemical, and boiler manufacturing. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Metallographic image of the 150mm ultra-thick 09MnNiDR container steel plate prepared for use in a -70℃ environment as described in Example 1;

[0019] Figure 2 Metallographic image of the 150mm ultra-thick 09MnNiDR container steel plate prepared for use in a -70℃ environment in Example 2;

[0020] Figure 3 Metallographic image of the 150mm ultra-thick 09MnNiDR container steel plate prepared for use in a -70℃ environment in Example 3. Detailed Implementation

[0021] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0022] This application provides a 150mm ultra-thick 09MnNiDR container steel for use in environments up to -70℃. Its chemical composition and mass percentage are as follows: C: 0.08%~0.12%, Mn: 1.5%~1.9%, P≤0.010%, S≤0.005%, Si: 0.35%~0.70%, Ni: 0.5%~0.9%, Mo: 0.02%~0.080%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities.

[0023] Furthermore, the chemical composition and mass percentage of the 150mm ultra-thick 09MnNiDR container steel used in the -70℃ environment are as follows: C: 0.09%~0.11%, Mn: 1.6%~1.9%, P≤0.008%, S≤0.005%, Si: 0.35%~0.65%, Ni: 0.5%~0.9%, Mo: 0.02%~0.08%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities.

[0024] This application also provides a method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment, which includes the following steps in sequence: desulfurization pretreatment - converter smelting - LF refining - RH vacuum treatment - continuous casting - slab stacking cooling - slab heating - controlled rolling - finishing - flaw detection - heat treatment.

[0025] In the continuous casting process, argon blowing protection is used for casting, the casting temperature is 1505~1525℃, the tundish superheat is 5-25℃, the billet pulling speed is 0.50~0.65m / min, a strong cooling process is used, and the billet is pressed down in the last 4 zones, with a casting slab thickness of 460mm.

[0026] In the slab heating process, the total time the slab spends in the furnace is greater than 10 min / cm, and the heating temperature is 1040~1150℃.

[0027] The controlled rolling process includes a first-stage rolling and a second-stage rolling. The first-stage rolling employs continuous rolling with a large reduction rate per rolling pass, while the second-stage rolling uses non-recrystallization controlled rolling. The final rolling temperature of the controlled rolling process is less than or equal to 760℃, and the post-rolling controlled cooling temperature is 350-450℃.

[0028] The heat treatment process includes: quenching and tempering the steel plate after shot blasting, with a quenching temperature of 890-930℃ and a total furnace time of 2.0±1min / mm×steel plate thickness / mm, water cooling to room temperature, a tempering temperature of 660-690℃ and a total heating time of 3.25±1min / mm×steel plate thickness / mm, and air cooling to room temperature.

[0029] The microstructure of the 09MnNiDR container steel prepared by the above method is bainite + ferrite + pearlite, with a yield strength ≥260MPa, tensile strength ≥440MPa, elongation after fracture ≥23%, and an average impact energy at -70℃ ≥100J.

[0030] The following specific examples will provide further details.

[0031] Examples 1-3 respectively provide a 150mm ultra-thick container steel for use in a -70℃ environment and a preparation method thereof. The preparation method includes the following steps in sequence: desulfurization pretreatment - 150-ton converter smelting - LF refining - RH vacuum treatment - continuous casting - slab stacking cooling - slab heating - controlled rolling - finishing - flaw detection - quenching + tempering heat treatment.

[0032] To ensure excellent core quality in continuously cast slabs, low superheat, strong cooling, and slow casting rates were employed during casting. Specific casting procedures are shown in Table 1.

[0033]

[0034] Table 1 Casting process

[0035] To ensure high steel purity, the content of P and S is strictly controlled during production. The chemical composition is shown in Table 2.

[0036]

[0037] Table 2 Chemical Composition

[0038] To ensure grain refinement, low-temperature heating, short total furnace time, and two-stage rolling are adopted. The reduction per pass in the first stage rolling is controlled to be greater than or equal to 30 mm, and the final rolling temperature and red-hot temperature are low. The rolling process is shown in Table 3.

[0039]

[0040] Table 3 Rolling process

[0041] Due to the extra-thickness of the steel plate, a quenching and tempering heat treatment process was adopted. The quenching heating used a short holding time, and the tempering was carried out at a high temperature. The heat treatment process is shown in Table 4.

[0042]

[0043] Table 4 Heat Treatment Process

[0044] The properties of the 09MnNiDR container steel obtained in Examples 1-3 are shown in Table 5.

[0045]

[0046] Table 5 Performance Parameters

[0047] It can be seen that the technical solution of this application produces 150mm ultra-thick steel plates that meet the requirements of -70℃ environment by strictly controlling harmful elements P and S, using low C, adding appropriate Ni, Mo and Mn alloying elements to match the 460mm thick section continuous casting billet, controlling rolling and tempering heat treatment processes.

[0048] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment, characterized in that: The chemical composition and mass percentage of the container steel are as follows: C: 0.08%~0.12%, Mn: 1.5%~1.9%, P≤0.010%, S≤0.005%, Si: 0.35%~0.70%, Ni: 0.5%~0.9%, Mo: 0.02%~0.080%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities; The preparation method of the 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment includes the following steps in sequence: desulfurization pretreatment - converter smelting - LF refining - RH vacuum treatment - continuous casting - slab stacking cooling - slab heating - controlled rolling - finishing - flaw detection - heat treatment. In the continuous casting process, argon blowing protection is used for casting, the casting temperature is 1505~1525℃, the tundish superheat is 5-25℃, the billet pulling speed is 0.50~0.65m / min, a strong cooling process is used, and the billet is pressed down in the last 4 zones, with a casting slab thickness of 460mm. The controlled rolling process includes a first-stage rolling and a second-stage rolling. The first-stage rolling adopts continuous rolling with a large rolling pass reduction rate, and the second-stage rolling adopts non-recrystallization controlled rolling. The final rolling temperature of the controlled rolling process is less than or equal to 760°C. The heat treatment process includes: quenching and tempering the steel plate after shot blasting and cooling, wherein the tempering temperature is 660-690℃.

2. The method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment according to claim 1, characterized in that: Its chemical composition and mass percentage are as follows: C: 0.09%~0.11%, Mn: 1.6%~1.9%, P≤0.008%, S≤0.005%, Si: 0.35%~0.65%, Ni: 0.5%~0.9%, Mo: 0.02%~0.08%, Nb≤0.05%, V≤0.05%, Al≥0.02%, N≤120ppm, with the balance being Fe and unavoidable impurities.

3. The method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment according to claim 1, characterized in that: In the slab heating process, the total time the slab spends in the furnace is greater than 10 min / cm, and the heating temperature is 1040~1150℃.

4. The method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment according to claim 1, characterized in that: The temperature for the controlled cooling after rolling in the controlled rolling process is 350-450℃.

5. The method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment according to claim 1, characterized in that: In the heat treatment process, the quenching temperature is 890-930℃, the total furnace time is 2.0±1min / mm×steel plate thickness (the unit of steel plate thickness is mm), water cooling to room temperature, the total heating time for tempering is 3.25±1min / mm×steel plate thickness (the unit of steel plate thickness is mm), and air cooling to room temperature.

6. The method for preparing 150mm ultra-thick 09MnNiDR container steel for use in a -70℃ environment according to claim 1, characterized in that: The microstructure of the 09MnNiDR container steel is bainite + ferrite + pearlite, with a yield strength ≥260MPa, tensile strength ≥440MPa, elongation after fracture ≥23%, and an average impact energy at -70℃ ≥100J.

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