Electroslag container plate with ultralow-temperature impact requirement and preparation method of electroslag container plate

Abstract

The invention discloses an electroslag container plate with an ultralow-temperature impact requirement and a preparation method of the electroslag container plate. The electroslag container plate comprises the following chemical components in percentage by mass: less than or equal to 0.20% of C, 0.10-0.50% of Si, less than or equal to 0.90% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 3.00-4.00% of Ni, less than or equal to 0.30% of Cr, less than or equal to 0.20% of Mo and the balance of Fe and inevitable impurities. The preparation method comprises the working procedures of smelting, continuous casting, electroslag remelting, heating, rolling, hydrogen diffusion annealing and heat treatment. The thickness of the steel plate provided by the invention is 220mm-250mm, the yield strength is greater than or equal to 350MPa, the tensile strength is 485-585MPa, the ductility is greater than or equal to 24.5%, the impact energy unit value at the position of 1 / 2 of the transverse plate thickness of the steel plate at the temperature of-111 DEG C is greater than or equal to 83.3 J, the internal and external quality is excellent, and the design and manufacturing of key equipment such as ultralow-temperature storage tanks are completely met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to an electroslag container plate requiring ultra-low temperature impact and a preparation method thereof. Background Art

[0002] As cryogenic storage tanks become larger and thicker, industries like the chemical industry are increasingly demanding that the critical pressure-bearing cylinder materials of these equipment withstand harsh and extreme environments. To meet this demand for thick, high-performance steel plates in these equipment manufacturing industries, it is necessary to develop nickel-containing alloy steel plates with superior strength and toughness. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a high-performance ultra-low temperature impact electroslag container plate and its preparation method, wherein the single value of the impact energy at -111°C at 1 / 2 of the transverse thickness of the steel plate is ≥83.3J. In order to solve the above technical problems, the technical solutions of the present invention are as follows: An electroslag container plate with ultra-low temperature impact requirements has the following chemical composition and mass percentage: C≤0.20%, Si0.10%-0.50%, Mn≤0.90%, P≤0.010%, S≤0.005%, Ni 3.00%-4.00%, Cr≤0.30%, Mo≤0.20%, and the balance is Fe and unavoidable impurities.

[0004] The thickness of the electroslag container plate of the present invention is 220 mm to 250 mm.

[0005] The preparation method of the electroslag container plate of the present invention comprises the steps of smelting, continuous casting, electroslag remelting, heating, rolling, hydrogen expansion annealing and heat treatment.

[0006] The heating process of the present invention: the soaking temperature is 1180°C to 1230°C.

[0007] The rolling process of the present invention adopts high temperature and high reduction in the initial rolling process, the initial rolling temperature is 1100° C. to 1200° C., the reduction of each of the first three passes is 35-40 mm, the rolling process adopts type II controlled rolling, the steel thickness is equal to the thickness of the finished steel plate + 70-100 mm; the initial rolling temperature of the second stage is ≤870° C., and the ACC is water-cooled to ≤530° C. after rolling.

[0008] The hydrogen expansion annealing process of the present invention is as follows: the temperature is kept at 620-710° C. in a car bottom furnace for 70-80 hours, and the heating and cooling rate is 30-50° C. / h.

[0009] The heat treatment process of the present invention includes: normalizing temperature of 800-895° C., heat preservation of 2.2-2.8 min / mm, water cooling after normalizing, wherein the initial water temperature is controlled to be ≤28° C., and gas stirring is fully turned on during the process; tempering temperature of 595-630° C., heat preservation of 2.8-4 min / mm.

[0010] The inventive principle and beneficial effects of the technical solution of the present invention are: In order to ensure the unit weight and purity of the steel plate, the present invention adopts the electroslag remelting method for production. The composition design re-matches the content of alloying elements such as C, Si, Mn, Ni, Cr, and Mo in the steel, while ensuring the strength of the steel plate, improving the low-temperature impact toughness of the steel plate. The C element in the present invention plays a major role in the mechanical properties of the steel. It forms carbides with other alloying elements in the steel, which increases the strength of the steel plate; at the same time, in order to improve the low-temperature impact toughness of the plate, the C content cannot be too high and must be controlled within a certain range. Since nickel and iron are infinitely solid-dissolved, the austenite region in the steel of the present invention can be significantly expanded and the austenite phase can be stabilized, the critical transition temperature can be lowered, and the hardenability of the steel plate can be improved. It is the main contributing element to maintain high strength and high toughness. In addition, in order to improve the strength and high-temperature resistance of the steel plate, the present invention also adds a certain amount of Cr and Mo elements to the steel.

[0011] This invention optimizes the composition and ratio of each element in the steel plate, ensuring that all mechanical properties meet the requirements of the ASME standard with a significant margin. By selecting appropriate alloy composition ratios and adjusting the corresponding rolling and heat treatment processes, the produced steel plate meets both the T1 grade of the domestic NB / T47013.3 flaw detection standard and the American standard SA578 / 578M C grade + S1 requirements.

[0012] The steel plate provided by the present invention has excellent mechanical properties and stable quality, with a yield strength of ≥350 MPa, a tensile strength of 485-585 MPa, an elongation of ≥24.5%, and a single value of impact energy of ≥83.3 J at -111°C at 1 / 2 of the transverse thickness of the steel plate; it has the characteristics of high purity, uniform composition, and internal density. The mechanical properties fully meet the standard requirements and are fully suitable for the design and manufacture of equipment such as large thick-walled cryogenic storage tanks. DETAILED DESCRIPTION

[0013] The present invention will be further described in detail below with reference to specific embodiments.

[0014] Examples 1-6 The chemical composition and thickness of the electroslag container plate of each embodiment are shown in Table 1.

[0015] Table 1 Chemical composition (wt%) and thickness of electroslag container plates in various embodiments

[0016] In Table 1, the balance of the chemical composition is Fe and inevitable impurities.

[0017] The preparation method of the electroslag container plate of each embodiment includes smelting, continuous casting, electroslag remelting, heating, rolling, hydrogen expansion annealing and heat treatment processes; the details are as follows: (1) Smelting A. Primary smelting: Steelmaking uses molten iron and scrap steel with low levels of impurities and residual elements such as P, As, Sn, and Sb; B. Refining: The total refining time should be ≥70 min, of which the white slag holding time should be ≥40 min to ensure good slag formation; the lime dosage should be ≥22 kg / t steel to ensure the refining effect; C. Vacuum treatment: transfer the refined molten steel into the VOD furnace for vacuum treatment, with the vacuum degree of 20-30Pa maintained for ≥20min, and then enter the casting process.

[0018] (2) Continuous casting The vacuum-treated molten steel is continuously cast to obtain a continuous casting billet; the flame heat is used to remove possible defects such as cracks and subcutaneous bubbles on the billet surface.

[0019] (3) Electroslag remelting The continuous casting billets are welded into electrodes, and then electroslag is remelted in an electroslag remelting furnace using a 960-980mm cross-section crystallizer to obtain electroslag ingots, which are then cleaned with heat before entering the next process.

[0020] (4) Heating A soaking furnace is used for heating; the soaking temperature of the electroslag ingot in the soaking furnace is 1180℃~1230℃.

[0021] (5) Rolling The product is produced by slab-forming, with a slab thickness of 500-530mm. The billet is heated in a continuous furnace for 1.1-1.3 min / mm. High-temperature, high-reduction rolling is employed at the start of rolling, with a temperature of 1100°C to 1200°C. The first three passes each have a reduction of 35-40mm. Type II controlled rolling is used during the rolling process, with the air-cured steel thickness being the finished plate thickness plus 70-100mm. The start-rolling temperature in stage II is ≤870°C, and after rolling, the ACC is water-cooled to ≤530°C.

[0022] (6) Hydrogen expansion annealing After rolling, the steel plate is promptly placed in the car bottom furnace for hydrogen annealing; hydrogen annealing process: keep warm at 620-710℃ in the car bottom furnace for 70-80h, with a heating and cooling rate of 30-50℃ / h.

[0023] (7) Heat treatment Normalizing and tempering of steel plates are both carried out in a car-bottom furnace; the normalizing temperature is 800-895°C, the insulation is 2.2-2.8 min / mm, and water cooling is carried out after normalizing, wherein the initial water temperature is controlled ≤28°C, and the gas stirring is fully turned on during the process; the tempering temperature is 595-630°C, and the insulation is 2.8-4 min / mm.

[0024] The parameters of the electroslag container plate smelting and heating process of each embodiment are shown in Table 2, and the parameters of the rolling, hydrogen expansion annealing and heat treatment process are shown in Table 3.

[0025] Table 2 Parameters of smelting and heating processes in various examples

[0026] Table 3 Rolling, hydrogen annealing and heat treatment process parameters of each embodiment

[0027] The mechanical properties test (at 1 / 2 of the plate thickness) was carried out on the electroslag container plates prepared in each embodiment. The results are shown in Table 4.

[0028] Table 4 Mechanical properties of steel plates in various examples

[0029] The electroslag container plates prepared in each example were subjected to ultrasonic flaw detection inspection one by one according to the dual standards of NB / T47013.3 and SA578 / 578M. The results are shown in Table 5.

[0030] Table 5 Flaw detection results of steel plates in various examples

[0031] As can be seen from Tables 4 and 5, the steel plate of the present invention has good tensile properties and good low-temperature impact toughness, and the flaw detection results meet the requirements of NB / T47013 T1 grade and SA578 / 578M standard C grade + S1, with excellent comprehensive performance.

Claims

1. An electroslag container plate with ultra-low temperature impact requirements, characterized in that: Its chemical composition and mass percentage are: C≤0.20%, Si 0.10%~0.50%, Mn≤0.90%, P≤0.010%, S≤0.005%, Ni 3.00%~4.00%, Cr≤0.30%, Mo≤0.20%, and the balance is Fe and unavoidable impurities.

2. The ultra-low temperature impact-resistant electroslag container plate according to claim 1, characterized in that: The thickness of the electroslag container plate is 220 mm to 250 mm.

3. The ultra-low temperature impact-resistant electroslag container plate according to claim 1, characterized in that: The electroslag container plate has a yield strength of ≥350 MPa, a tensile strength of 485-585 MPa, an elongation of ≥24.5%, and a single value of impact energy at -111°C at 1 / 2 of the transverse thickness of the steel plate of ≥83.3 J.

4. The method for preparing an electroslag container plate with ultra-low temperature impact requirements according to any one of claims 1 to 3, characterized in that: It includes smelting, continuous casting, electroslag remelting, heating, rolling, hydrogen annealing and heat treatment processes.

5. The method for preparing an electroslag container plate with ultra-low temperature impact requirements according to claim 4, characterized in that: The heating process: the soaking temperature is 1180°C to 1230°C.

6. The method for preparing an electroslag container plate with ultra-low temperature impact requirements according to claim 4, characterized in that: The rolling process adopts high temperature and high reduction in the initial rolling process, the initial rolling temperature is 1100° C. to 1200° C., the reduction amount of each of the first three passes is 35-40 mm, the rolling process adopts type II controlled rolling, the steel thickness is equal to the thickness of the finished steel plate + 70 to 100 mm; the initial rolling temperature of the second stage is ≤870° C., and the ACC is water-cooled to ≤530° C. after rolling.

7. The method for preparing an electroslag container plate with ultra-low temperature impact requirements according to claim 4, characterized in that: The hydrogen expansion annealing process is as follows: keeping the temperature at 620-710° C. for 70-80 hours, with a heating and cooling rate of 30-50° C. / h.

8. The method for preparing an electroslag container plate with ultra-low temperature impact requirements according to claim 4, characterized in that: The heat treatment process includes: normalizing temperature of 800-895° C., heat preservation of 2.2-2.8 min / mm, water cooling after normalizing; tempering temperature of 595-630° C., heat preservation of 2.8-4 min / mm.

9. The method for preparing an electroslag container plate with ultra-low temperature impact requirements according to claim 8, characterized in that: The normalizing process controls the initial water temperature to be ≤28° C., and the gas stirring is fully turned on during the process.

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