High-performance uniform container steel produced through casting blank and manufacturing method of high-performance uniform container steel

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to high-performance uniform container steel produced by casting blanks and a manufacturing method of the high-performance uniform container steel, and the container steel comprises the following chemical components in percentage by weight: 0.17-0.19% of C, 0.4-0.5% of Si, 1.5-1.6% of Mn, less than or equal to 0.02% of P, less than or equal to 0.003% of S, less than or equal to 0.45% of Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Cu + Ni) / 15, and the balance of Fe and inevitable impurities. According to the high-performance uniform container steel plate, the transverse impact energy Akv of 1 / 4 thickness at-20 DEG C is larger than or equal to 170 J, the yield strength ranges from 353 MPa to 356 MPa, the tensile strength ranges from 547 MPa to 551 MPa, the proportional gauge length elongation ranges from 26% to 28%, the actual difference value of yield strength uniformity is smaller than or equal to 3 MPa, the actual difference value of tensile strength uniformity is smaller than or equal to 4 MPa, and the actual difference value of proportional gauge length elongation uniformity is smaller than or equal to 2%.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, in particular to a casting process for producing high-performance uniform container steel and a manufacturing method thereof. Background Art

[0002] Driven by national requirements for green, environmentally friendly, and clean energy, the petrochemical and coal chemical industries are experiencing rapid growth. However, large-scale storage tanks, reactors, and other equipment within the petrochemical industry require high-performance, uniform steel plates. These devices often withstand high temperatures, high pressures, and corrosive media. The high performance and uniformity of these steel plates ensures that, during long-term operation, they will not experience safety incidents such as leaks and ruptures due to localized performance variations, thereby ensuring a safe and stable production process.

[0003] Therefore, a high-performance, uniform container steel plate produced by casting has become an important metal material for the manufacture of petrochemical container equipment such as gas absorption towers, large gas condensers, and chemical pipelines. Market demand is high, and domestic methods for producing high-performance, uniform container steel using casting have not yet been reported. The high-performance, uniform container steel plate exhibits excellent strength and toughness properties, with a transverse impact energy Akv of ≥170J at -20°C (1 / 4 thickness), a yield strength of 353-356MPa, a tensile strength of 547-551MPa, a proportional gauge elongation of 26-28%, an actual difference in yield strength uniformity of ≤3MPa, an actual difference in tensile strength uniformity of ≤4MPa, and an actual difference in proportional gauge elongation uniformity of ≤2%. This product has become an important metal material for the manufacture of equipment such as gas absorption towers, chemical pipelines, and normal-temperature wind tower gas storage tanks. The development of specialized container steel with high strength, uniformity, and high toughness has a significant guiding significance for the development of the high-performance, uniform container steel market.

[0004] Many steel mills at home and abroad are researching the production of high-strength, high-toughness container steel. However, a method for producing high-performance, uniform container steel plates from billets using a double-normalizing process has yet to be reported. Furthermore, published patents show very few actual engineering applications for these products. This paper describes a method for producing high-performance, uniform container steel from billets, which has been applied to a large-scale international petrochemical pipeline equipment project in the Middle East, and its performance has been recognized within the industry.

[0005] Publication number: CN105324505B - High-strength hot-rolled steel plate and its manufacturing method. Through rational composition design and an online controlled rolling and coiling and controlled cooling process, reasonable performance is achieved. However, this patent uses a microalloying composition design with 0.14% Ti, achieving a maximum strength uniformity of 59 MPa. The strength uniformity difference produced by this patented method also reaches 15 MPa, and no impact energy value is measured.

[0006] Publication number: CN113564504B - A heat treatment process for rapid aging of large-size GH4738 alloy forgings adopts a reasonable composition design and obtains reasonable performance through solid solution + aging heat treatment process. However, this patent adopts a high-alloy combination design of adding Co+Cr+Mo, and the product is a forging with a low yield and high production cost. In terms of strength uniformity, the highest reaches 13MPa.

[0007] The publication number is: CN110331343A - A low-yield ratio X80MO submarine pipeline steel plate and its manufacturing method. It adopts a reasonable composition design and obtains reasonable performance through online controlled rolling and cooling process. However, this patent adopts a high-alloy combination design of adding Ni+Cu+Cr+Mo, which has high alloy cost and the strength uniformity has a maximum difference of 42MPa.

[0008] Considering that ultra-low strength differential container steel plates require not only high strength and low-temperature toughness, particularly improved strength uniformity, but also good weldability, all of which must be easily produced and cost-effective, the inventors have conducted research on the chemical composition and production process for producing high-performance, uniform container steel using ingot casting. They have designed a method for producing high-performance, uniform container steel using ingot casting and a method for manufacturing the same. Summary of the Invention

[0009] The present invention addresses the above-mentioned technical problems, overcomes the shortcomings of the prior art, and provides a casting blank for producing high-performance uniform container steel and a manufacturing method thereof. The invention utilizes a low-carbon, low-manganese, and carbon equivalent (Ceq) ≤ 0.45 low-cost composition design, combined with a reasonable rolling and double normalizing heat treatment process, to produce high-performance uniform container steel. The uniformity of the mechanical properties meets the requirements of technical standards, thereby resolving technical difficulties such as unstable strength uniformity and unstable weldability in the production of high-strength container steel from casting blanks.

[0010] In the first aspect, the present application proposes a method for producing high-performance uniform container steel by casting, the manufacturing method comprising: molten iron desulfurization pretreatment → converter smelting → LF+RH refining → continuous casting → slow cooling of casting stacking → casting inspection → casting determination → casting acceptance → casting heating → descaling → controlled rolling → weak controlled cooling → flaw detection → shot blasting → primary normalizing → secondary normalizing → straightening → cutting and sampling → printing identification → inspection → warehousing;

[0011] In steelmaking composition design, the chemical composition of container steel includes by weight percentage:

[0012] C: 0.17-0.19, Si: 0.4-0.5, Mn: 1.5-1.6, P≤0.02, S≤0.003, Ceq=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15≤0.45, the balance is Fe and unavoidable impurities.

[0013] Furthermore, it also includes the furnace rolling process, specifically: the steel tapping temperature is between 1180-1220℃, the furnace time is 220-260 minutes, the finishing rolling start temperature is 880-910℃, the thickness of the warm billet is controlled at ≥8.0h, where h is the thickness of the finished steel plate, the second stage final rolling temperature is 800-820℃, weak controlled cooling is used after rolling, and the total controlled cooling water volume is 1800-2000m 3 .

[0014] Furthermore, a heat treatment process is also included, specifically: first normalizing temperature: 890-900°C, heating rate: 1.4±0.1min / mm, holding time: 15±2min; second normalizing temperature: 840-850°C, heating rate: 1.6±0.1min / mm, holding time: 15±2min.

[0015] In a second aspect, the present application also provides a casting blank for producing high-performance uniform container steel, which is produced using the casting blank for producing high-performance uniform container steel manufacturing method described in any one of the first aspects.

[0016] Furthermore, the obtained ingot is used to produce high-performance uniform container steel at -20°C, with a 1 / 4 thickness transverse impact energy Akv ≥ 170J, a yield strength of 353-356MPa, and a tensile strength of 547-551MPa.

[0017] Furthermore, the obtained castings for producing high-performance uniform container steel have a proportional gauge elongation of 26-28%, an actual difference in yield strength uniformity of ≤3MPa, an actual difference in tensile strength uniformity of ≤4MPa, and an actual difference in proportional gauge elongation uniformity of ≤2%.

[0018] Furthermore, its microstructure is pearlite + ferrite structure, the grain size is controlled at 10μm-12μm, and the grain size is controlled at level 10.

[0019] The beneficial effects of the present invention are:

[0020] (1) The method of the present invention produces high-performance uniform container steel by designing a low-carbon, low-manganese and carbon equivalent Ceq ≤ 0.45 low-cost component, combined with a reasonable rolling and two-time normalizing heat treatment process. The high-temperature end rolling does not require high rolling force of the rolling mill, and the production process is simple and low-cost.

[0021] (2) The method of the present invention adopts a reasonable controlled rolling process to produce high-performance uniformity such as high strength and high impact toughness. All mechanical performance indicators meet the technical standard requirements. Its actual production level reaches: -20℃, 1 / 4 thickness transverse impact energy Akv ≥ 170J, yield strength: 353-356MPa, tensile strength 547-551MPa, proportional gauge elongation: 26-28%, actual difference in yield strength uniformity ≤ 3MPa, actual difference in tensile strength uniformity ≤ 4MPa, actual difference in proportional gauge elongation uniformity: ≤ 2%;

[0022] (3) The method of the present invention successfully solves the technical difficulties of unstable impact performance, poor uniformity and unstable weldability of high-strength container steel produced by casting, and successfully produces high-strength, high-toughness and high-performance uniformity container steel on the rolling mill production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a normalizing metallographic structure diagram of a high-performance uniform container steel produced by casting in a specific embodiment of the present invention at 1 / 4 thickness;

[0024] Figure 2 This is a schematic diagram of dissecting and sampling along the rolling direction of the casting billet to produce high-performance uniform container steel in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is mainly realized through the following processes: molten iron desulfurization pretreatment → converter smelting → LF+RH refining → continuous casting → ingot stacking and slow cooling → ingot inspection → ingot judgment → ingot acceptance → ingot heating → descaling → controlled rolling → weak controlled cooling → flaw detection → shot blasting → primary normalizing → secondary normalizing → straightening → cutting and sampling → printing identification → inspection → warehousing.

[0026] (1) The actual weight percentages of chemical composition of high performance uniformity container steel produced by casting are shown in Table 1 below.

[0027] Table 1 Chemical composition and percentage of each embodiment

[0028]

[0029] Because high-strength, high-toughness container steel plates require high-temperature, high-reduction rolling, the post-rolling shape of the steel plates is poor, requiring online pre-straightening at 780-810°C to maintain the original shape. While maintaining low-cost production requirements, the company aims to ensure uniform performance across the entire width and length of the steel plate. During the rolling process, the entire steel plate surface must be flat, with an unevenness of ≤2mm / m. Rolling is terminated at high temperatures to reduce the need for high rolling forces and other equipment.

[0030] (2) Rolling heating process

[0031] Table 2 Heating process parameters of each embodiment

[0032]

[0033] Since the experimental steel needs to obtain high strength, high toughness and high performance uniformity, the steel plate needs to be controlled rolled in a high-temperature and high-reduction mode. In order to improve and reduce the impact of low-multiple quality of the ingot, this patented method adopts a large compression ratio of 8.8 times, that is, 220mm thick ingots are selected, and the soaking temperature is controlled between 1200℃-1240℃. Considering that the temperature difference from the surface to the core of the ingot is controlled within the range of ≤3℃, the furnace time is appropriately extended to ensure that the overall steel temperature of the ingot is uniform and avoid the appearance of "red and black" alternating steel temperatures.

[0034] (3) Controlled rolling process

[0035] Table 3 Controlled rolling process parameters

[0036]

[0037] Since the thickness of the finished product is 25mm, in order to avoid core segregation during the rolling process, which affects the strength and impact toughness value, a two-stage widening rolling method is adopted, and the deformation rate of the first stage rolling pass is ≥20%, and the deformation rate of the second stage rolling pass is ≥15%, ensuring that the structure from the surface to the core is sufficiently fine.

[0038] (4) First normalizing process

[0039] Table 4 First normalizing process parameters

[0040]

[0041] (5) Second normalizing process

[0042] Table 5 Second normalizing process parameters

[0043]

[0044] (6) Mechanical properties

[0045] Select each embodiment steel plate according to Figure 2 Nine sets of specimens were taken from the steel plate positions shown in the figure to test the mechanical properties. The mechanical properties results are shown in Tables 6 and 7:

[0046] Table 6

[0047]

[0048] Table 7

[0049]

[0050] The present invention uses a low-carbon + low-manganese alloying composition with a carbon equivalent of Ceq ≤ 0.45 to produce high-performance uniform container steel using ingots. After two normalizing heat treatments, the mechanical properties all meet the technical standard requirements. The product has been applied to a large-scale international petrochemical pipeline equipment project in the Middle East, greatly improving the competitiveness of export products. The high-performance uniform container steel plate has a -20°C, 1 / 4 thickness transverse impact energy Akv ≥ 170J, yield strength: 353-356MPa, tensile strength 547-551MPa, proportional gauge elongation: 26-28%, actual difference in yield strength uniformity ≤ 3MPa, actual difference in tensile strength uniformity ≤ 4MPa, actual difference in proportional gauge elongation uniformity: ≤ 2%. The strength, plasticity, and transverse impact toughness performance indicators obtained in this application all meet the technical standard requirements, and also meet the mechanical performance design standards required by a large-scale international petrochemical project in the Middle East. Due to the high demands for high strength, high toughness, and plasticity, in actual industrial production, to avoid the failure to meet the requirements of high reduction rolling, which can easily lead to coarse original grain size and even the appearance of mixed crystals, thus seriously affecting the mechanical properties of strength and low-temperature impact toughness, high requirements are placed on the uniformity and precision of heating temperatures in rolling equipment and normalizing furnaces. Through a low-carbon, low-manganese, and low-carbon equivalent (Ceq ≤ 0.45) low-cost composition design, the use of a transversely and longitudinally widened rolling billet design method, and the completion of the rolling process at high temperature, this overcomes the inability of conventional rolling lines to produce high-performance, uniform container steel with high strength, high toughness, and high welding stability due to the limited equipment capacity.

[0051] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A method for producing high-performance uniform container steel by casting, characterized in that: The manufacturing method comprises: hot metal desulfurization pretreatment → converter smelting → LF+RH refining → continuous casting → ingot stacking and slow cooling → ingot inspection → ingot determination → ingot acceptance → ingot heating → descaling → controlled rolling → weak controlled cooling → flaw detection → shot blasting → primary normalizing → secondary normalizing → straightening → cutting and sampling → printing labels → inspection → warehousing; In steelmaking composition design, the chemical composition of container steel includes by weight percentage: C: 0.17-0.19, Si: 0.4-0.5, Mn: 1.5-1.6, P≤0.02, S≤0.003, Ceq=C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15≤0.45, the balance is Fe and unavoidable impurities.

2. The method for producing high-performance uniformity container steel by casting according to claim 1, characterized in that: It also includes the furnace rolling process, specifically: the steel tapping temperature is between 1180-1220℃, the furnace time is 220-260 minutes, the finishing rolling start temperature is 880-910℃, the thickness of the warm billet is controlled at ≥8.0h, where h is the thickness of the finished steel plate, the second stage final rolling temperature is 800-820℃, weak controlled cooling is used after rolling, and the total controlled cooling water volume is 1800-2000m 3 .

3. The method for producing high-performance uniformity container steel by casting according to claim 1, characterized in that: It also includes a heat treatment process, specifically: first normalizing temperature: 890-900°C, heating rate: 1.4±0.1min / mm, holding time: 15±2min; second normalizing temperature: 840-850°C, heating rate: 1.6±0.1min / mm, holding time: 15±2min.

4. A casting process for producing high-performance uniform container steel, characterized in that: The invention is obtained by using the method for producing high-performance uniform container steel by using the casting billet described in any one of claims 1-3.

5. The process for producing high-performance uniform container steel by casting according to claim 4, characterized in that: At -20℃, 1 / 4 thickness transverse impact energy Akv≥170J, yield strength: 353-356MPa, tensile strength 547-551MPa.

6. The process for producing high-performance uniform container steel by casting according to claim 4, characterized in that: Its proportional gauge elongation is 26-28%, the actual difference in yield strength uniformity is ≤3MPa, the actual difference in tensile strength uniformity is ≤4MPa, and the actual difference in proportional gauge elongation uniformity is ≤2%.

7. The process for producing high-performance uniform container steel by casting according to claim 4, characterized in that: Its microstructure is pearlite + ferrite structure, the grain size is controlled at 10μm-12μm, and the grain size is controlled at level 10.

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